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Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
W o r l d M e t e o r o l o g i c a l O r g a n i z a t i o n 
WMO-No. 168 
GUIDE 
TO HYDROLOGICAL PRACTICES 
Fifth edition 
1994 
DATA ACQUISITION AND PROCESSING, 
ANALYSIS, FORECASTING AND 
OTHER APPLICATIONS
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Page 
CONTENTS 
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxix 
PART A — GENERAL 
CHAPTER 1 — INTRODUCTION TO THE GUIDE . . . . . . . . . . . . . . . . . . . . . . 1 
1.1 Scope of the Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 
1.2 Plan and content of the Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 
1.3 Cross-reference between the Guide and the HOMS Reference 
Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 
CHAPTER 2 — WATER-RELATED ACTIVITIES OF WMO . . . . . . . . . . . . 5 
2.1 General overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 
2.1.1 Purpose and scope of water-related activities . . . . . . . . . . . . . . . . . . . . . . . . 6 
2.1.2 Programme organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 
2.1.3 Programme implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 
2.1.4 Human-resources development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 
2.1.5 Technical cooperation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 
2.2 International databases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 
2.2.1 Hydrological Information Referral Service (INFOHYDRO) . . . . . . . . 11 
2.2.2 Global Runoff Data Centre (GRDC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 
2.2.3 World Climate Data Information Referral Service (INFOCLIMA) . . 13 
2.3 The Hydrological Operational Multipurpose System (HOMS). . . . . . . 14 
2.3.1 Structure of HOMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 
2.3.2 Organization and operation of HOMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 
2.4 Training in hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 
CHAPTER 3 — HYDROLOGICAL SERVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 
3.1 Functions of Hydrological Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 
3.1.1 Uses of hydrological information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 
3.1.2 Functions and responsibilities of a Hydrological Service . . . . . . . . . . . . 24 
3.1.3 Types of data required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 
3.1.4 Real-time forecasting of extremes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 
3.2 Organization of Hydrological and Meteorological Services . . . . . . . . . 29 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
iv CONTENTS 
CHAPTER 4 — HYDROLOGICAL STANDARDS AND 
Page 
REGULATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 
4.1 Units and symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 
4.2 Recommended practices and procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 
4.3 Accuracy of hydrological measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 
4.3.1 Basic principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 
4.3.2 Definitions of terms related to accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 
4.3.3 Types of error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 
4.3.4 Sources of errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 
4.3.5 Secondary errors of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 
4.3.6 Characterization of instruments and methods of observation . . . . . . . . 54 
4.3.7 Recommended accuracy of hydrological measurements . . . . . . . . . . . . . 55 
4.4 Hydrological codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 
4.4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 
4.4.2 Code forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 
4.4.3 Hydrological observing station identification . . . . . . . . . . . . . . . . . . . . . . . . 57 
4.4.4 BUFR and GRIB codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 
CHAPTER 5 — INTERNATIONAL ORGANIZATIONS INVOLVED 
WITH HYDROLOGY AND WATER RESOURCES . . . . 59 
5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 
5.2 Intergovernmental organizations (IGOs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 
5.3 Nature and interrelationship of the activities of the UN organizations 
in water-resources development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 
5.4 Arrangements for inter-organizational cooperation at the global, 
regional, and sectoral levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 
5.5 Non-governmental organizations (NGOs) . . . . . . . . . . . . . . . . . . . . . . . . . . 72 
5.6 Institutionalized cooperation in international river and lake basins . . . 82 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 
PART B — HYDROLOGICAL INSTRUMENTS AND METHODS OF 
OBSERVATION AND ESTIMATION 
CHAPTER 6 — OVERVIEW OF HYDROLOGICAL INSTRUMENTS 
AND METHODS OF OBSERVATION . . . . . . . . . . . . . . . . . . . 83 
6.1 The hydrological cycle as the subject of observation . . . . . . . . . . . . . . . . 83 
6.2 Emerging technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 
6.2.1 Remote sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 
6.2.2 Micro-electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 
6.2.3 Microprocessors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 
6.2.4 Multi-parameter data loggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
CONTENTS v 
Page 
CHAPTER 7 — PRECIPITATION MEASUREMENT . . . . . . . . . . . . . . . . . . . . 91 
7.1 General requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 
7.2 Gauge location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 
7.3 Non-recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 
7.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 
7.3.2 Standard gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 
7.3.3 Storage gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 
7.3.4 Methods of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 
7.3.5 Errors and accuracy of readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 
7.3.6 Correction of systematic errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 
7.4 Recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 
7.4.1 Weighing type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 
7.4.2 Float type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 
7.4.3 Tipping-bucket type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 
7.4.4 Rainfall-intensity recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 
7.4.5 Methods of recording . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 
7.5 Snowfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 
7.5.1 Depth of snowfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 
7.5.2 Water equivalent of snowfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 
7.6 Observation of rainfall by radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 
7.6.1 Uses of radar in hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 
7.6.2 The radar-rainfall equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 
7.6.3 Factors affecting measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 
7.6.3.1 Precipitation type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 
7.6.3.2 Beam width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 
7.6.3.3 Refraction of beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 
7.6.3.4 Atmospheric attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 
7.6.3.5 Range attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 
7.6.4 Methods and procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 
7.6.4.1 Photographic methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 
7.6.4.2 Manual techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 
7.6.4.3 Automatic techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 
7.6.5 Doppler radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 
7.7 Observations by satellite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 
7.8 Dew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 
7.9 Sampling for precipitation quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 
7.9.1 Sample collectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 
7.9.1.1 Rain collectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 
7.9.1.2 Snow collectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 
7.9.1.3 Dry deposition collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
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Page 
CHAPTER 8 — SNOW COVER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 
8.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 
8.2 Snow courses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 
8.2.1 Points of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 
8.2.2 Snow-sampling equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 
8.2.3 Snow-sampling procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 
8.2.4 Accuracy of measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 
8.3 Depth and extent of snow cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 
8.3.1 Measurement with graduated snow stakes . . . . . . . . . . . . . . . . . . . . . . . . . . 122 
8.3.2 Measurement with snow tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 
8.3.3 Measurement by photogrammetric methods . . . . . . . . . . . . . . . . . . . . . . . . 122 
8.4 Radioisotope snow gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 
8.4.1 Vertical radioisotope snow gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 
8.4.2 Horizontal radioisotope snow gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 
8.5 Snow pillows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 
8.6 Natural gamma radiation surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 
8.6.1 Aerial gamma surveys of snow cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 
8.6.2 Ground surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 
8.7 Measurement of water equivalent by cosmic radiation . . . . . . . . . . . . . . 127 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 
CHAPTER 9 — EVAPORATION AND EVAPOTRANSPIRATION . . . . . 129 
9.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 
9.2 Pan evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 
9.3 Soil evaporimeters and lysimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 
9.4 Snow evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 
9.5 Indirect methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 
9.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 
9.5.2 Solar radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 
9.5.3 Long-wave radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 
9.5.4 Air temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 
9.5.5 Water-surface temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 
9.5.6 Humidity or vapour pressure of the air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 
9.5.7 Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 
9.5.8 Integrating devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 
CHAPTER 10 — WATER LEVELS OF RIVERS, LAKES, AND 
RESERVOIRS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 
10.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 
10.2 Gauges for measurement of stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 
10.2.1 Non-recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
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10.2.2 Recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 
10.3 Procedures for measurement of stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 
10.3.1 Establishment of gauge datum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 
10.3.2 Recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 
10.3.3 Winter operation of recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 
10.4 Frequency of stage measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 
CHAPTER 11 — DISCHARGE MEASUREMENTS . . . . . . . . . . . . . . . . . . . . . . . 141 
11.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 
11.2 Measurement of discharge by current meters . . . . . . . . . . . . . . . . . . . . . . . . 141 
11.2.1 Selection of sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 
11.2.2 Measurement of cross-sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 
11.2.3 Measurement of velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 
11.2.3.1 Meters for measurement of velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 
11.2.3.2 Measurement of velocity using the current meter . . . . . . . . . . . . . . . . . . . . 144 
11.2.3.3 Determination of mean velocity in a vertical . . . . . . . . . . . . . . . . . . . . . . . . 144 
11.2.4 Computations of discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 
11.2.5 Measurement of discharge under ice cover . . . . . . . . . . . . . . . . . . . . . . . . . . 147 
11.2.5.1 Selection of site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 
11.2.5.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 
11.2.5.3 Discharge measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 
11.2.5.4 Computation of discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 
11.2.6 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 
11.3 Measurement of discharge by the float method . . . . . . . . . . . . . . . . . . . . . . 150 
11.3.1 Selection of sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 
11.3.2 Floats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 
11.3.3 Measuring procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 
11.3.4 Computation of velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 
11.3.5 Computation of discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 
11.4 Measurement of discharge by dilution methods . . . . . . . . . . . . . . . . . . . . . 151 
11.4.1 General requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 
11.4.2 Selection of site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 
11.4.3 Tracers and detection equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 
11.4.4 Computation of discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 
11.5 Measurement of corresponding stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 
11.6 Computations of discharge by indirect methods . . . . . . . . . . . . . . . . . . . . . 154 
11.6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 
11.6.2 Field survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 
11.6.3 Slope-area measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 
11.6.4 Measurement of flow through culverts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 
11.6.5 Measurement of flow through width contractions . . . . . . . . . . . . . . . . . . . 155
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11.6.6 Measurement of flow over dams and highway embankments . . . . . . . . 155 
11.7 Measurement of discharge under difficult conditions . . . . . . . . . . . . . . . . 156 
11.7.1 Unstable channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 
11.7.2 Mountain streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 
11.7.3 Measurement of unsteady flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 
11.7.3.1 Measurement of discharge during floods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 
11.7.3.2 Measurement of discharge in tidal reaches . . . . . . . . . . . . . . . . . . . . . . . . . . 158 
11.7.4 Weed growth in stream channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 
11.8 Non-traditional methods of stream gauging . . . . . . . . . . . . . . . . . . . . . . . . . 161 
11.8.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 
11.8.2 Moving boat method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 
11.8.3 Ultrasonic ( acoustic ) method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 
11.8.4 Electromagnetic method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 
CHAPTER 12 — STREAM GAUGING STATIONS . . . . . . . . . . . . . . . . . . . . . . . 167 
12.1 Purpose of stream gauging stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 
12.2 Selection of sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 
12.3 Stage-discharge controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 
12.4 Measuring structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 
12.4.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 
12.4.2 Selection of structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 
12.4.3 Measurement of head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 
12.4.4 Operation of measuring structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 
12.5 Stage-discharge relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 
12.5.1 Stability of stage-discharge relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 
12.5.2 Frequency of discharge measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 
CHAPTER 13 — SEDIMENT DISCHARGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 
13.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 
13.2 Selection of site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 
13.3 Measurement of suspended-sediment discharge . . . . . . . . . . . . . . . . . . . . . 175 
13.3.1 Sampling instruments and in situ gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 
13.3.2 Measurement procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 
13.3.3 Determination of sediment concentration . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 
13.3.4 Computation of suspended-sediment discharge . . . . . . . . . . . . . . . . . . . . . 177 
13.3.5 Continuous record of suspended-sediment discharge . . . . . . . . . . . . . . . . 178 
13.4 Measurement of bed-material discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 
13.4.1 Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 
13.4.2 Measurement procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 
13.4.3 Computation of bed-material discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
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13.4.4 Continuous record of bed-material discharge . . . . . . . . . . . . . . . . . . . . . . . 181 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 
CHAPTER 14 — ICE ON RIVERS, LAKES AND RESERVOIRS . . . . . . . . 183 
14.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 
14.2 Elements of ice regime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 
14.3 Methods of observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 
14.4 Times and frequency of observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 
14.5 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 
Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 
CHAPTER 15 — SOIL-MOISTURE MEASUREMENT . . . . . . . . . . . . . . . . . . 185 
15.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 
15.2 Gravimetric method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 
15.2.1 Sample collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 
15.2.2 Description of samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 
15.2.2.1 Auger samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 
15.2.2.2 Tube or core-barrel samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 
15.2.3 Laboratory procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 
15.3 Electrical-resistance method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 
15.4 Neutron method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 
15.4.1 Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 
15.4.2 Access tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 
15.4.3 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 
15.4.4 Measurements and accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 
15.5 Gamma-ray attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 
15.6 Dielectric methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 
15.6.1 Time domain reflectometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 
15.6.2 Capacitance method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 
15.7 Remote sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 
15.8 Tensiometric method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 
CHAPTER 16 — GROUNDWATER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 
16.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 
16.2 Installation of observation wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 
16.3 Testing of observation wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 
16.4 Sealing and filling of abandoned wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 
16.5 Instruments and methods of observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 
16.5.1 Manually-operated instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 
16.5.2 Automatic recording instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 
16.5.3 Water samplers for unpumped wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
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16.5.4 Salinity and temperature loggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 
16.6 Groundwater quality monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 
CHAPTER 17 — WATER QUALITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 
17.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 
17.2 Sampling methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 
17.2.1 Types of water samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 
17.2.1.1 Grab samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 
17.2.1.2 Composite samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 
17.2.2 Collecting a representative water sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 
17.2.3 Field sampling equipment and techniques . . . . . . . . . . . . . . . . . . . . . . . . . . 216 
17.2.3.1 Grab samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 
17.2.3.2 Dissolved-oxygen sampler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 
17.2.3.3 Automatic samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 
17.2.3.4 Sampling procedures as influenced by station location and season . . . 220 
17.3 Preparation for field trips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 
17.3.1 General preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 
17.3.2 Selection of sample volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 
17.3.3 Checklist prior to field trip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 
17.4 Field filtration and preservation procedures . . . . . . . . . . . . . . . . . . . . . . . . . 222 
17.4.1 Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 
17.4.2 Preservation techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 
17.4.2.1 Containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 
17.4.2.2 Chemical addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 
17.4.2.3 Freezing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 
17.4.2.4 Refrigeration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 
17.4.2.5 Practical aspects of preservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 
17.5 Field measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 
17.5.1 Automatic monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 
17.5.2 Field-measured parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 
17.5.2.1 pH measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 
17.5.2.2 Conductivity measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 
17.5.2.3 Dissolved-oxygen measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 
17.5.2.4 Temperature measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 
17.5.2.5 Turbidity measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 
17.5.2.6 Colour measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 
17.5.2.7 Transparency measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 
17.5.2.8 General summary of field procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 
17.6 Radioactivity measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 
17.6.1 Sources of radioactivity in water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 
17.6.2 Collection and preservation of samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
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17.7 Sampling for biological analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 
17.7.1 Microbiological analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 
17.7.2 Macrobiota . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 
17.8 Biochemical oxygen demand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 
17.8.1 Methods of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 
17.8.2 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 
CHAPTER 18 — SAFETY CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . 239 
18.1 General practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 
18.2 Safety at recording stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 
18.2.1 Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 
18.2.2 Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 
18.2.3 Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 
18.3 Safety precautions when working from bridges . . . . . . . . . . . . . . . . . . . . . 240 
18.3.1 Traffic hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 
18.3.2 Hazards from suspended equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 
18.4 Safety precautions while wading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 
18.4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 
18.4.2 Assessing the situation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 
18.4.3 Wearing of lifejackets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 
18.4.4 Safety lines and taglines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 
18.4.5 Wading technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 
18.4.6 Mishap technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 
18.4.7 Responsibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 
18.5 Safety precautions while working from boats . . . . . . . . . . . . . . . . . . . . . . . 242 
18.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 
18.5.2 Lifejackets and safety equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 
18.5.3 Use of taglines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 
18.5.4 Use of dinghies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 
18.6 Safety precautions when working from cableways . . . . . . . . . . . . . . . . . . 243 
18.7 Safety precautions when handling equipment . . . . . . . . . . . . . . . . . . . . . . . 244 
18.7.1 Surveying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 
18.7.2 Chainsaws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 
18.7.3 Electrical equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 
18.7.4 Power tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 
18.7.5 Protective clothing and safety equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 
18.7.6 Radioactive equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 
18.7.7 Safety aspects of groundwater monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . 245 
18.8 Safety precautions when handling chemicals . . . . . . . . . . . . . . . . . . . . . . . . 245 
18.9 Special precautions for cold conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 
18.9.1 Hypothermia (exposure) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
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18.9.2 Frostbite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 
18.9.3 Working on ice-covered lakes and streams . . . . . . . . . . . . . . . . . . . . . . . . . . 247 
18.9.4 Working in mountainous areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 
18.9.5 Cold-water survival . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 
18.10 Special precautions for hot conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 
18.10.1 Heat stroke (hyperthermia) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 
18.10.2 Sunburn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 
18.11 Travel and transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 
18.11.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 
18.11.2 Helicopters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 
18.11.3 Motor vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 
18.12 Survival kits and rations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 
18.13 Other hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 
PART C — COLLECTION, PROCESSING AND DISSEMINATION OF 
HYDROLOGICAL DATA 
CHAPTER 19 — THE ROLE OF HYDROLOGICAL DATA IN AN 
INFORMATION SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 
19.1 Information systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 
19.2 Computer technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 
19.3 Staff and training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 
CHAPTER 20 — DESIGN AND EVALUATION OF HYDROLOGICAL 
NETWORKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 
20.1 General concepts of network design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 
20.1.1 Definition of network design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 
20.1.2 Surrogate approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 
20.1.3 The basic network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 
20.1.3.1 The minimum network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 
20.1.3.2 Expanding the information base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 
20.1.4 Integrated network design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264 
20.1.4.1 Stations for operational purposes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 
20.1.4.2 Bench-mark stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 
20.1.4.3 Representative basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 
20.1.5 Conducting a network analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 
20.2 Density of stations for a minimum network . . . . . . . . . . . . . . . . . . . . . . . . . 268 
20.2.1 Minimum densities for climatological stations . . . . . . . . . . . . . . . . . . . . . . 269 
20.2.1.1 Precipitation stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 
20.2.1.2 Snow surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
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20.2.1.3 Evaporation stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 
20.2.2 Minimum densities for hydrometric stations . . . . . . . . . . . . . . . . . . . . . . . . 272 
20.2.2.1 Streamflow stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 
20.2.2.2 River stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 
20.2.2.3 Lake and reservoir stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 
20.2.2.4 Sediment discharge and sedimentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 
20.2.2.5 Water quality stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 
20.2.2.6 Water temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 
20.2.2.7 Ice cover on rivers and lakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 
20.3 Groundwater observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 
20.4 Specific requirements for water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 
20.4.1 Water quality parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 
20.4.2 Surface-water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 
20.4.3 Precipitation quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 
20.4.4 Sediment quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 
20.4.5 Groundwater quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 
CHAPTER 21 — COLLECTION OF DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 
21.1 Site selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 
21.2 Station identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 
21.2.1 Identification of data-collection sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 
21.2.2 Descriptive information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 
21.2.2.1 Station description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 
21.2.2.2 Detailed sketch of station location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 
21.2.2.3 Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 
21.2.2.4 Coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 
21.2.2.5 Narrative description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 
21.3 Frequency and timing of station visits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298 
21.3.1 Manual stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298 
21.3.2 Recording stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 
21.4 Maintenance of collection sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 
21.5 Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 
21.5.1 Manual stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 
21.5.2 Recording stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303 
21.5.3 Real-time reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303 
21.5.4 Additional instructions for observers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 
21.6 Transmission systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 
21.6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 
21.6.2 Transmission links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 
21.6.3 Factors affecting the choice of transmission systems . . . . . . . . . . . . . . . . 306 
21.7 Water quality monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
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21.7.1 Station identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 
21.7.2 Field sheets for water quality monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 
21.7.3 Transportation of water quality samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 
21.7.4 Field quality assurance in water quality monitoring . . . . . . . . . . . . . . . . . 311 
21.8 Special data collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 
21.8.1 Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 
21.8.2 Bucket surveys of storm rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 
21.8.3 Weather-radar and satellite data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 
21.8.4 Extreme river stages and discharges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 
CHAPTER 22 — DATA REVIEW AND CODING . . . . . . . . . . . . . . . . . . . . . . . . . 315 
22.1 Quality control and error detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 
22.1.1 Inspection of stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 
22.1.2 Preliminary checking of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 
22.1.3 Error detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317 
22.1.4 Results of quality control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318 
22.2 Validation procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 
22.2.1 General procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 
22.2.2 Combined techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320 
22.2.3 Specific validation procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 
22.2.3.1 Climatological data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 
22.2.3.2 Rainfall data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 
22.2.3.3 Snow and ice data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326 
22.2.3.4 Water level data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326 
22.2.3.5 River-gauging data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 
22.2.3.6 Water quality data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 
22.2.3.7 Sediment data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331 
22.2.4 Missing data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331 
22.3 Coding data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 
22.3.1 Location codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 
22.3.2 Variable (parameter) codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 
22.3.3 Data-qualification codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 
22.3.4 Missing data codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 
22.3.5 Transmission codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 
CHAPTER 23 — PRIMARY DATA PROCESSING . . . . . . . . . . . . . . . . . . . . . . . 341 
23.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 
23.2 Data entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 
23.2.1 Key stroking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 
23.2.2 Processing of charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
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23.2.3 Manual stations using telemetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346 
23.2.4 Automatic station data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 
23.2.4.1 Paper-tape and cassette recorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 
23.2.4.2 Solid-state memories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 
23.3 Processing procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 
23.3.1 General primary processing procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 
23.3.2 Specific primary processing procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352 
23.3.2.1 Climatological data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352 
23.3.2.2 Evaporation and evapotranspiration observations . . . . . . . . . . . . . . . . . . . 353 
23.3.2.3 Precipitation data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 
23.3.2.4 Streamflow data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 
23.3.2.5 Water quality data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 
CHAPTER 24 — DATA STORAGE AND RETRIEVAL . . . . . . . . . . . . . . . . . . 361 
24.1 Archiving of original data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 
24.2 Management and storage of processed data . . . . . . . . . . . . . . . . . . . . . . . . . 361 
24.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 
24.2.2 Controlling data flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 
24.2.3 Updating procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 
24.2.4 Compression and accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365 
24.2.5 Physical-file organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 
24.2.6 Logical-file organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 
24.2.7 Extraction of single variable data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 
24.2.8 On-line versus off-line data storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 
24.3 Data retrieval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 
CHAPTER 25 — DATA DISSEMINATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 
25.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 
25.2 Catalogues of information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 
25.3 Summary reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 
25.4 Publication of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 
25.4.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 
25.4.2 Frequency of publication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 
25.4.3 Contents and format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 
25.5 Magnetic media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385 
25.5.1 Tapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385 
25.5.2 Magnetic discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 
25.5.3 Optical discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389 
25.6 Real-time data-exchange formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390
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CHAPTER 26 — INTRODUCTION TO HYDROLOGICAL ANALYSIS . . 391 
26.1 Methods of analysis in hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 
26.2 Scope of Part D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392 
CHAPTER 27 — FREQUENCY ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 
27.1 The use of frequency analysis in hydrology . . . . . . . . . . . . . . . . . . . . . . . . . 393 
27.2 Statistical series and return periods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 
27.3 Mathematical approach to frequency analysis . . . . . . . . . . . . . . . . . . . . . . . 394 
27.3.1 Probability distributions used in hydrology . . . . . . . . . . . . . . . . . . . . . . . . . 394 
27.3.2 Parameter estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 
27.3.3 Homogeneity of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 
CHAPTER 28 — RAINFALL FREQUENCY AND INTENSITY . . . . . 399 
28.1 Rainfall frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 
28.1.1 Point rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 
28.1.1.1 Adjustment of data for fixed observational time intervals . . . . . . . . . . . . 399 
28.1.1.2 Indirect estimation of point rainfall-frequency data . . . . . . . . . . . . . . . . . . 400 
28.1.1.3 Maximum observed rainfalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 
28.1.2 Area rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 
28.1.3 Generalized maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 
28.1.4 Drought . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 
28.2 Rainfall intensities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406 
28.2.1 Point rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406 
28.2.2 Area rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408 
CHAPTER 29 — STORM-RAINFALL ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . 409 
29.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 
29.2 Mass curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 
29.3 Depth-area duration analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 
29.4 Probable maximum precipitation (PMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 
29.4.1 Methods of estimating PMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 
29.4.2 Preliminary estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 
29.4.3 Selection of design rainfall duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 
29.4.4 Selection of sub-basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 
29.4.5 Storm transposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 
29.4.6 Selection and analysis of major storms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414 
29.4.7 Maximization of selected storms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 
29.4.8 Orientation of storm-rainfall patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415
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29.4.9 Regional consistency of estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 
29.4.10 Estimating in the absence of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418 
CHAPTER 30 — INTERPRETATION OF PRECIPITATION DATA . . . . 421 
30.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 
30.2 Adjustment of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 
30.2.1 Standard base period of record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 
30.2.2 Double-mass curve analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 
30.2.3 Estimation of missing data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 
30.3 Areal distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 
30.3.1 Illustration by isohyetal maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 
30.3.2 Evaluation of physiographic effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 
30.4 Computation of areal average precipitation . . . . . . . . . . . . . . . . . . . . . . . . . 425 
30.4.1 Arithmetic mean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 
30.4.2 Polygon method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426 
30.4.3 Isohyetal method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 
30.4.4 Per cent normal method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 
30.4.5 Hypsometric method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 
CHAPTER 31 — SNOW-MELT RUNOFF ANALYSIS . . . . . . . . . . . . . . . . . . . 431 
31.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431 
31.2 Theory of snow melt at a point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431 
31.3 Estimates of catchment melt in the absence of rain . . . . . . . . . . . . . . . . . . 434 
31.4 Estimates of catchment melt with rain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 
31.5 Estimating snow-melt inflow rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 
31.6 Evaporation from a snow cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439 
31.7 Probable maximum precipitation and snow melt . . . . . . . . . . . . . . . . . . . . 441 
31.7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441 
31.7.2 Probable maximum snow accumulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441 
31.7.3 Snow-melt estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442 
31.8 Runoff from short-period snow melt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442 
31.8.1 Plains regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442 
31.8.2 Mountainous terrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443 
CHAPTER 32 — EVALUATION OF STREAMFLOW DATA . . . . . . . . . . . . 445 
32.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445 
32.2 Adjustment of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445 
32.3 Areal distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 
32.3.1 Maps of average annual runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
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32.3.2 Average runoff from precipitation and temperature data . . . . . . . . . . . . . 447 
32.3.3 Correlation between stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450 
32.3.4 Effective length of an extended record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452 
CHAPTER 33 — RAINFALL-RUNOFF RELATIONSHIPS . . . . . . . . . . . . . . 453 
33.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453 
33.2 Runoff volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453 
33.2.1 Antecedent-precipitation index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453 
33.2.2 Initial base flow as an index to runoff volume . . . . . . . . . . . . . . . . . . . . . . . 456 
33.2.3 Moisture-accounting techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456 
33.3 Temporal distribution of runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 
33.3.1 Unit hydrograph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 
33.3.1.1 Derivation from streamflow records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 
33.3.1.2 Derivation by synthetic methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 460 
33.3.1.3 Conversion of unit-hydrograph durations . . . . . . . . . . . . . . . . . . . . . . . . . . . 462 
33.3.2 Isochrone method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463 
33.4 Distributed models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465 
CHAPTER 34 — STREAMFLOW ROUTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 
34.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 
34.2 Hydrodynamic methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 
34.2.1 Complete method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 
34.2.2 Diffusion and kinematic routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469 
34.3 Hydrological methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 
34.4 Reservoir routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473 
CHAPTER 35 — LOW-FLOW AND DROUGHT ANALYSIS . . . . . . . . . . . . 475 
35.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475 
35.2 Flow-duration curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475 
35.3 Low-flow frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476 
35.4 Statistical analysis of droughts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 
35.5 Recession-curve analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479 
CHAPTER 36 — FLOOD-FLOW FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . . . . 481 
36.1 Station analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 
36.1.1 Peak flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 
36.1.2 Statistical analysis of flood hydrographs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 
36.2 Regionalization of flood flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
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36.2.1 The index-flood procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483 
36.2.2 Regression-based procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485 
CHAPTER 37— ESTIMATING LAKE AND RESERVOIR 
EVAPORATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 
37.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 
37.2 Water-budget method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 
37.2.1 Inflow and outflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 
37.2.2 Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 
37.2.3 Net seepage and bank storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 
37.2.4 Change in reservoir storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 
37.3 Energy-budget method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 
37.3.1 Reflected long-wave radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491 
37.3.2 Radiation emitted by the reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491 
37.3.3 Change in energy storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492 
37.3.4 Energy utilized for evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493 
37.3.5 Energy convected to or from the body of water as sensible heat . . . . . . 493 
37.3.6 Energy advected by the evaporated water . . . . . . . . . . . . . . . . . . . . . . . . . . . 493 
37.3.7 Energy exchange between the water in the reservoir and its bottom . . 493 
37.3.8 Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495 
37.4 Aerodynamic approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495 
37.4.1 Value of the coefficient N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496 
37.4.2 Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497 
37.4.3 Water-surface temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497 
37.4.4 Humidity or vapour pressure of the air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497 
37.4.5 Eddy-correlation method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498 
37.5 Combination of aerodynamic and energy-balance equations . . . . . . . . 498 
37.6 Extrapolation from pan measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504 
CHAPTER 38 — ESTIMATING BASIN EVAPOTRANSPIRATION . . . . 507 
38.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507 
38.2 Potential evapotranspiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507 
38.3 Actual evapotranspiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507 
38.4 Water-budget method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 
38.4.1 Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 
38.4.2 Streamflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 
38.4.3 Change in storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 
38.4.4 Deep seepage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 
38.5 Energy-budget method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 
38.6 Aerodynamic approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509
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38.7 Penman-Monteith method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 
38.8 Priestley-Taylor (radiation) method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 
38.9 Complementary equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 
CHAPTER 39 — MODELLING OF HYDROLOGICAL SYSTEMS . . . . . 513 
39.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513 
39.2 Black-box models (system approach) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514 
39.3 Conceptual models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515 
39.3.1 Model of the Hydrometeorological Centre of the former U.S.S.R. . . . 516 
39.3.2 Sacramento model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517 
39.3.3 Tank model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 519 
39.3.4 Selection of models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522 
39.4 Hydrodynamic models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522 
39.5 Parameter evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525 
39.6 Stochastic simulation of hydrological time-series . . . . . . . . . . . . . . . . . . . 526 
39.6.1 Markovian lag-1 models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527 
39.6.2 Autoregressive moving average (ARMA) models . . . . . . . . . . . . . . . . . . 527 
39.6.3 Fractional gaussian noise and broken-line process models . . . . . . . . . . . 528 
39.7 Water quality modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 
39.7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 
39.7.2 Types of models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 
39.7.3 Models of the pollutant transport in rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . 530 
39.7.4 Applications and examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531 
39.8 Selection of models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532 
CHAPTER 40 — MEASUREMENT OF PHYSIOGRAPHIC 
CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537 
40.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537 
40.2 Reference systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537 
40.3 Point measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538 
40.4 Linear problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538 
40.4.1 The stream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539 
40.4.2 The drainage network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539 
40.4.3 Stream profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540 
40.4.4 The drainage network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541 
40.4.5 Cross-section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541 
40.4.6 Physical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 542 
40.5 Area measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 542 
40.5.1 The basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 542 
40.5.2 The grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548
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40.6 Volumetric measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 
40.6.1 Bathymetric methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 
40.6.2 Topographical methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 
40.7 Geographical information systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550 
PART E — HYDROLOGICAL FORECASTING 
CHAPTER 41 — INTRODUCTION TO HYDROLOGICAL 
FORECASTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 
41.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 
41.2 Characteristics of forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 
41.3 Effectiveness of hydrological forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553 
41.3.1 Accuracy and timeliness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554 
41.3.2 Costs and benefits of hydrological forecasts . . . . . . . . . . . . . . . . . . . . . . . . . 554 
41.4 The hydrological forecasting service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558 
41.4.1 Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558 
41.4.2 Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559 
41.5 Dissemination of forecasts and warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . 559 
CHAPTER 42 — DATA REQUIREMENTS OF HYDROLOGICAL 
FORECASTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563 
42.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563 
42.2 Data for developing forecast procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563 
42.2.1 Hydrological variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564 
42.2.2 Catchment characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564 
42.2.3 River characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564 
42.3 Data required for forecast operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564 
42.3.1 Rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565 
42.3.2 Snow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565 
42.3.3 Water levels and streamflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565 
42.3.4 Other data requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566 
42.4 Use of meteorological forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566 
42.5 Precision of observations and frequency of measurement . . . . . . . . . . . 567 
42.6 Operational data acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567 
42.6.1 Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567 
42.6.2 Remote sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567 
42.6.2.1 Radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 570 
42.6.2.2 Satellite-based methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571 
42.6.2.3 Aircraft sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573 
42.6.3 Communication systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573 
42.6.3.1 Satellite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574
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42.6.3.2 Meteor burst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575 
CHAPTER 43 — FORECASTING TECHNIQUES . . . . . . . . . . . . . . . . . . . . . . . . 577 
43.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 
43.2 Correlation and regression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 
43.3 Moisture index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579 
43.4 Crest stage forecasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 580 
43.5 Flow forecasts based upon storage volume . . . . . . . . . . . . . . . . . . . . . . . . . . 582 
43.6 Recession forecasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582 
43.7 Conceptual streamflow models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582 
43.8 Flow routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583 
43.9 Time-series analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583 
43.10 Forecast-adjustment techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584 
43.11 Probability forecasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586 
CHAPTER 44 — FLOOD AND WATER-SUPPLY FORECASTS . . . . . . . . 589 
44.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589 
44.2 Flood forecasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589 
44.3 Flash floods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590 
44.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590 
44.3.1.1 Forecast programmes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590 
44.3.1.2 Alarm systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591 
44.3.1.3 Watches and warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591 
44.3.1.4 Flash floods and water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591 
44.3.2 Flooding in urban areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592 
44.3.3 Dam break . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592 
44.4 Storm surges in rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 593 
44.5 Water supply forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594 
44.6 Low flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596 
CHAPTER 45 — SNOW-MELT FORECASTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 
45.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 
45.2 Snow-melt runoff processes in lowland and mountain rivers . . . . . . . . 597 
45.3 Forecast models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598 
45.3.1 Index methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598 
45.3.2 Conceptual models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 599 
45.3.3 Extended streamflow prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600 
45.3.4 Input data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 601 
45.4 Short- and medium-term snow-melt runoff forecasts . . . . . . . . . . . . . . . . 601
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45.5 Long-term snow-melt forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602 
45.6 Seasonal snow-melt forecasts for the plains regions . . . . . . . . . . . . . . . . . 602 
45.7 Seasonal snow-melt forecasts for mountainous regions . . . . . . . . . . . . . . 603 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604 
CHAPTER 46 — FORECASTS OF ICE FORMATION AND 
BREAK-UP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605 
46.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605 
46.2 Forecasts of ice formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605 
46.3 Forecasts of ice break-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608 
46.3.1 Forecasts of ice break-up on reservoirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608 
46.3.2 Forecasts of ice break-up on rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609 
46.4 Long-term ice forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609 
46.4.1 Ice formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610 
46.4.2 Ice break-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610 
46.4.3 Use of atmospheric circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611 
PART F — APPLICATIONS FOR WATER MANAGEMENT 
CHAPTER 47 — INTRODUCTION TO APPLICATIONS FOR 
WATER MANAGEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613 
47.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613 
47.2 Purposes to be served by a water-management project . . . . . . . . . . . . . . 613 
47.3 Multi-purpose projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614 
47.4 Water-resources systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614 
47.5 Preliminary investigation of water-management projects . . . . . . . . . . . . 614 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 618 
CHAPTER 48 — SUSTAINABLE WATER DEVELOPMENT . . . . . . . . . . . 619 
48.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619 
48.2 The changing nature of the resource . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619 
48.2.1 Natural changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619 
48.2.2 Man-induced changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620 
48.3 Changing attitudes to management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620 
48.3.1 Watershed management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622 
48.3.2 Management fragmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622 
48.4 Water-data programmes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623 
48.4.1 Assessing data needs for the future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623 
48.4.2 Network character and relevance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624 
48.4.3 Network-strategy options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625 
48.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 626 
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 626
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Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994
Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994

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Guide to Hydrological Practices: Data Acquisition and Processing, Analysis, Forecasting and other Applications WMO-No.168 Fifth Edition 1994

  • 3. W o r l d M e t e o r o l o g i c a l O r g a n i z a t i o n WMO-No. 168 GUIDE TO HYDROLOGICAL PRACTICES Fifth edition 1994 DATA ACQUISITION AND PROCESSING, ANALYSIS, FORECASTING AND OTHER APPLICATIONS
  • 5. Page CONTENTS Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxix PART A — GENERAL CHAPTER 1 — INTRODUCTION TO THE GUIDE . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Scope of the Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Plan and content of the Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.3 Cross-reference between the Guide and the HOMS Reference Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 CHAPTER 2 — WATER-RELATED ACTIVITIES OF WMO . . . . . . . . . . . . 5 2.1 General overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1.1 Purpose and scope of water-related activities . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.2 Programme organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.3 Programme implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.1.4 Human-resources development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.1.5 Technical cooperation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.2 International databases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.2.1 Hydrological Information Referral Service (INFOHYDRO) . . . . . . . . 11 2.2.2 Global Runoff Data Centre (GRDC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.2.3 World Climate Data Information Referral Service (INFOCLIMA) . . 13 2.3 The Hydrological Operational Multipurpose System (HOMS). . . . . . . 14 2.3.1 Structure of HOMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.3.2 Organization and operation of HOMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.4 Training in hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 CHAPTER 3 — HYDROLOGICAL SERVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.1 Functions of Hydrological Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.1.1 Uses of hydrological information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.1.2 Functions and responsibilities of a Hydrological Service . . . . . . . . . . . . 24 3.1.3 Types of data required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.1.4 Real-time forecasting of extremes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.2 Organization of Hydrological and Meteorological Services . . . . . . . . . 29 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
  • 6. iv CONTENTS CHAPTER 4 — HYDROLOGICAL STANDARDS AND Page REGULATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4.1 Units and symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4.2 Recommended practices and procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4.3 Accuracy of hydrological measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.3.1 Basic principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.3.2 Definitions of terms related to accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.3.3 Types of error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.3.4 Sources of errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.3.5 Secondary errors of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.3.6 Characterization of instruments and methods of observation . . . . . . . . 54 4.3.7 Recommended accuracy of hydrological measurements . . . . . . . . . . . . . 55 4.4 Hydrological codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.4.2 Code forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.4.3 Hydrological observing station identification . . . . . . . . . . . . . . . . . . . . . . . . 57 4.4.4 BUFR and GRIB codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 CHAPTER 5 — INTERNATIONAL ORGANIZATIONS INVOLVED WITH HYDROLOGY AND WATER RESOURCES . . . . 59 5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 5.2 Intergovernmental organizations (IGOs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 5.3 Nature and interrelationship of the activities of the UN organizations in water-resources development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 5.4 Arrangements for inter-organizational cooperation at the global, regional, and sectoral levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 5.5 Non-governmental organizations (NGOs) . . . . . . . . . . . . . . . . . . . . . . . . . . 72 5.6 Institutionalized cooperation in international river and lake basins . . . 82 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 PART B — HYDROLOGICAL INSTRUMENTS AND METHODS OF OBSERVATION AND ESTIMATION CHAPTER 6 — OVERVIEW OF HYDROLOGICAL INSTRUMENTS AND METHODS OF OBSERVATION . . . . . . . . . . . . . . . . . . . 83 6.1 The hydrological cycle as the subject of observation . . . . . . . . . . . . . . . . 83 6.2 Emerging technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 6.2.1 Remote sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 6.2.2 Micro-electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 6.2.3 Microprocessors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 6.2.4 Multi-parameter data loggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
  • 7. CONTENTS v Page CHAPTER 7 — PRECIPITATION MEASUREMENT . . . . . . . . . . . . . . . . . . . . 91 7.1 General requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 7.2 Gauge location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 7.3 Non-recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 7.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 7.3.2 Standard gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 7.3.3 Storage gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 7.3.4 Methods of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 7.3.5 Errors and accuracy of readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 7.3.6 Correction of systematic errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 7.4 Recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7.4.1 Weighing type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7.4.2 Float type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 7.4.3 Tipping-bucket type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.4.4 Rainfall-intensity recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 7.4.5 Methods of recording . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 7.5 Snowfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 7.5.1 Depth of snowfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 7.5.2 Water equivalent of snowfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 7.6 Observation of rainfall by radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 7.6.1 Uses of radar in hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 7.6.2 The radar-rainfall equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 7.6.3 Factors affecting measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 7.6.3.1 Precipitation type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 7.6.3.2 Beam width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 7.6.3.3 Refraction of beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 7.6.3.4 Atmospheric attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 7.6.3.5 Range attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7.6.4 Methods and procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7.6.4.1 Photographic methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7.6.4.2 Manual techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7.6.4.3 Automatic techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 7.6.5 Doppler radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 7.7 Observations by satellite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 7.8 Dew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 7.9 Sampling for precipitation quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 7.9.1 Sample collectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 7.9.1.1 Rain collectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 7.9.1.2 Snow collectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 7.9.1.3 Dry deposition collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
  • 8. vi CONTENTS Page CHAPTER 8 — SNOW COVER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 8.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 8.2 Snow courses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 8.2.1 Points of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 8.2.2 Snow-sampling equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 8.2.3 Snow-sampling procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 8.2.4 Accuracy of measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 8.3 Depth and extent of snow cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 8.3.1 Measurement with graduated snow stakes . . . . . . . . . . . . . . . . . . . . . . . . . . 122 8.3.2 Measurement with snow tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 8.3.3 Measurement by photogrammetric methods . . . . . . . . . . . . . . . . . . . . . . . . 122 8.4 Radioisotope snow gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 8.4.1 Vertical radioisotope snow gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 8.4.2 Horizontal radioisotope snow gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 8.5 Snow pillows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 8.6 Natural gamma radiation surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 8.6.1 Aerial gamma surveys of snow cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 8.6.2 Ground surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 8.7 Measurement of water equivalent by cosmic radiation . . . . . . . . . . . . . . 127 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 CHAPTER 9 — EVAPORATION AND EVAPOTRANSPIRATION . . . . . 129 9.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 9.2 Pan evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 9.3 Soil evaporimeters and lysimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 9.4 Snow evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 9.5 Indirect methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 9.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 9.5.2 Solar radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 9.5.3 Long-wave radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 9.5.4 Air temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 9.5.5 Water-surface temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 9.5.6 Humidity or vapour pressure of the air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 9.5.7 Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 9.5.8 Integrating devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 CHAPTER 10 — WATER LEVELS OF RIVERS, LAKES, AND RESERVOIRS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 10.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 10.2 Gauges for measurement of stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 10.2.1 Non-recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
  • 9. CONTENTS vii Page 10.2.2 Recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 10.3 Procedures for measurement of stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 10.3.1 Establishment of gauge datum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 10.3.2 Recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 10.3.3 Winter operation of recording gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 10.4 Frequency of stage measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 CHAPTER 11 — DISCHARGE MEASUREMENTS . . . . . . . . . . . . . . . . . . . . . . . 141 11.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 11.2 Measurement of discharge by current meters . . . . . . . . . . . . . . . . . . . . . . . . 141 11.2.1 Selection of sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 11.2.2 Measurement of cross-sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 11.2.3 Measurement of velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 11.2.3.1 Meters for measurement of velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 11.2.3.2 Measurement of velocity using the current meter . . . . . . . . . . . . . . . . . . . . 144 11.2.3.3 Determination of mean velocity in a vertical . . . . . . . . . . . . . . . . . . . . . . . . 144 11.2.4 Computations of discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 11.2.5 Measurement of discharge under ice cover . . . . . . . . . . . . . . . . . . . . . . . . . . 147 11.2.5.1 Selection of site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 11.2.5.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 11.2.5.3 Discharge measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 11.2.5.4 Computation of discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 11.2.6 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 11.3 Measurement of discharge by the float method . . . . . . . . . . . . . . . . . . . . . . 150 11.3.1 Selection of sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 11.3.2 Floats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 11.3.3 Measuring procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 11.3.4 Computation of velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 11.3.5 Computation of discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 11.4 Measurement of discharge by dilution methods . . . . . . . . . . . . . . . . . . . . . 151 11.4.1 General requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 11.4.2 Selection of site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 11.4.3 Tracers and detection equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 11.4.4 Computation of discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 11.5 Measurement of corresponding stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 11.6 Computations of discharge by indirect methods . . . . . . . . . . . . . . . . . . . . . 154 11.6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 11.6.2 Field survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 11.6.3 Slope-area measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 11.6.4 Measurement of flow through culverts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 11.6.5 Measurement of flow through width contractions . . . . . . . . . . . . . . . . . . . 155
  • 10. viii CONTENTS Page 11.6.6 Measurement of flow over dams and highway embankments . . . . . . . . 155 11.7 Measurement of discharge under difficult conditions . . . . . . . . . . . . . . . . 156 11.7.1 Unstable channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 11.7.2 Mountain streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 11.7.3 Measurement of unsteady flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 11.7.3.1 Measurement of discharge during floods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 11.7.3.2 Measurement of discharge in tidal reaches . . . . . . . . . . . . . . . . . . . . . . . . . . 158 11.7.4 Weed growth in stream channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 11.8 Non-traditional methods of stream gauging . . . . . . . . . . . . . . . . . . . . . . . . . 161 11.8.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 11.8.2 Moving boat method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 11.8.3 Ultrasonic ( acoustic ) method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 11.8.4 Electromagnetic method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 CHAPTER 12 — STREAM GAUGING STATIONS . . . . . . . . . . . . . . . . . . . . . . . 167 12.1 Purpose of stream gauging stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 12.2 Selection of sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 12.3 Stage-discharge controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 12.4 Measuring structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 12.4.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 12.4.2 Selection of structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 12.4.3 Measurement of head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 12.4.4 Operation of measuring structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 12.5 Stage-discharge relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 12.5.1 Stability of stage-discharge relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 12.5.2 Frequency of discharge measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 CHAPTER 13 — SEDIMENT DISCHARGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 13.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 13.2 Selection of site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 13.3 Measurement of suspended-sediment discharge . . . . . . . . . . . . . . . . . . . . . 175 13.3.1 Sampling instruments and in situ gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 13.3.2 Measurement procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 13.3.3 Determination of sediment concentration . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 13.3.4 Computation of suspended-sediment discharge . . . . . . . . . . . . . . . . . . . . . 177 13.3.5 Continuous record of suspended-sediment discharge . . . . . . . . . . . . . . . . 178 13.4 Measurement of bed-material discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 13.4.1 Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 13.4.2 Measurement procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 13.4.3 Computation of bed-material discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
  • 11. CONTENTS ix Page 13.4.4 Continuous record of bed-material discharge . . . . . . . . . . . . . . . . . . . . . . . 181 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 CHAPTER 14 — ICE ON RIVERS, LAKES AND RESERVOIRS . . . . . . . . 183 14.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 14.2 Elements of ice regime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 14.3 Methods of observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 14.4 Times and frequency of observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 14.5 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 CHAPTER 15 — SOIL-MOISTURE MEASUREMENT . . . . . . . . . . . . . . . . . . 185 15.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 15.2 Gravimetric method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 15.2.1 Sample collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 15.2.2 Description of samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 15.2.2.1 Auger samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 15.2.2.2 Tube or core-barrel samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 15.2.3 Laboratory procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 15.3 Electrical-resistance method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 15.4 Neutron method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 15.4.1 Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 15.4.2 Access tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 15.4.3 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 15.4.4 Measurements and accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 15.5 Gamma-ray attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 15.6 Dielectric methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 15.6.1 Time domain reflectometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 15.6.2 Capacitance method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 15.7 Remote sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 15.8 Tensiometric method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 CHAPTER 16 — GROUNDWATER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 16.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 16.2 Installation of observation wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 16.3 Testing of observation wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 16.4 Sealing and filling of abandoned wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 16.5 Instruments and methods of observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 16.5.1 Manually-operated instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 16.5.2 Automatic recording instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 16.5.3 Water samplers for unpumped wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
  • 12. x CONTENTS Page 16.5.4 Salinity and temperature loggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 16.6 Groundwater quality monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 CHAPTER 17 — WATER QUALITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 17.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 17.2 Sampling methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 17.2.1 Types of water samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 17.2.1.1 Grab samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 17.2.1.2 Composite samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 17.2.2 Collecting a representative water sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 17.2.3 Field sampling equipment and techniques . . . . . . . . . . . . . . . . . . . . . . . . . . 216 17.2.3.1 Grab samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 17.2.3.2 Dissolved-oxygen sampler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 17.2.3.3 Automatic samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 17.2.3.4 Sampling procedures as influenced by station location and season . . . 220 17.3 Preparation for field trips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 17.3.1 General preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 17.3.2 Selection of sample volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 17.3.3 Checklist prior to field trip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 17.4 Field filtration and preservation procedures . . . . . . . . . . . . . . . . . . . . . . . . . 222 17.4.1 Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 17.4.2 Preservation techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 17.4.2.1 Containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 17.4.2.2 Chemical addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 17.4.2.3 Freezing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 17.4.2.4 Refrigeration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 17.4.2.5 Practical aspects of preservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 17.5 Field measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 17.5.1 Automatic monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 17.5.2 Field-measured parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 17.5.2.1 pH measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 17.5.2.2 Conductivity measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 17.5.2.3 Dissolved-oxygen measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 17.5.2.4 Temperature measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 17.5.2.5 Turbidity measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 17.5.2.6 Colour measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 17.5.2.7 Transparency measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 17.5.2.8 General summary of field procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 17.6 Radioactivity measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 17.6.1 Sources of radioactivity in water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 17.6.2 Collection and preservation of samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
  • 13. CONTENTS xi Page 17.7 Sampling for biological analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 17.7.1 Microbiological analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 17.7.2 Macrobiota . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 17.8 Biochemical oxygen demand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 17.8.1 Methods of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 17.8.2 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 CHAPTER 18 — SAFETY CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . 239 18.1 General practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 18.2 Safety at recording stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 18.2.1 Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 18.2.2 Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 18.2.3 Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 18.3 Safety precautions when working from bridges . . . . . . . . . . . . . . . . . . . . . 240 18.3.1 Traffic hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 18.3.2 Hazards from suspended equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 18.4 Safety precautions while wading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 18.4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 18.4.2 Assessing the situation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 18.4.3 Wearing of lifejackets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 18.4.4 Safety lines and taglines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 18.4.5 Wading technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 18.4.6 Mishap technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 18.4.7 Responsibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 18.5 Safety precautions while working from boats . . . . . . . . . . . . . . . . . . . . . . . 242 18.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 18.5.2 Lifejackets and safety equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 18.5.3 Use of taglines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 18.5.4 Use of dinghies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 18.6 Safety precautions when working from cableways . . . . . . . . . . . . . . . . . . 243 18.7 Safety precautions when handling equipment . . . . . . . . . . . . . . . . . . . . . . . 244 18.7.1 Surveying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 18.7.2 Chainsaws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 18.7.3 Electrical equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 18.7.4 Power tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 18.7.5 Protective clothing and safety equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 18.7.6 Radioactive equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 18.7.7 Safety aspects of groundwater monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . 245 18.8 Safety precautions when handling chemicals . . . . . . . . . . . . . . . . . . . . . . . . 245 18.9 Special precautions for cold conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 18.9.1 Hypothermia (exposure) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
  • 14. xii CONTENTS Page 18.9.2 Frostbite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 18.9.3 Working on ice-covered lakes and streams . . . . . . . . . . . . . . . . . . . . . . . . . . 247 18.9.4 Working in mountainous areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 18.9.5 Cold-water survival . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 18.10 Special precautions for hot conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 18.10.1 Heat stroke (hyperthermia) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 18.10.2 Sunburn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 18.11 Travel and transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 18.11.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 18.11.2 Helicopters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 18.11.3 Motor vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 18.12 Survival kits and rations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 18.13 Other hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 PART C — COLLECTION, PROCESSING AND DISSEMINATION OF HYDROLOGICAL DATA CHAPTER 19 — THE ROLE OF HYDROLOGICAL DATA IN AN INFORMATION SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 19.1 Information systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 19.2 Computer technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 19.3 Staff and training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 CHAPTER 20 — DESIGN AND EVALUATION OF HYDROLOGICAL NETWORKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 20.1 General concepts of network design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 20.1.1 Definition of network design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 20.1.2 Surrogate approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 20.1.3 The basic network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 20.1.3.1 The minimum network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 20.1.3.2 Expanding the information base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 20.1.4 Integrated network design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264 20.1.4.1 Stations for operational purposes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 20.1.4.2 Bench-mark stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 20.1.4.3 Representative basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 20.1.5 Conducting a network analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 20.2 Density of stations for a minimum network . . . . . . . . . . . . . . . . . . . . . . . . . 268 20.2.1 Minimum densities for climatological stations . . . . . . . . . . . . . . . . . . . . . . 269 20.2.1.1 Precipitation stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 20.2.1.2 Snow surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
  • 15. CONTENTS xiii Page 20.2.1.3 Evaporation stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 20.2.2 Minimum densities for hydrometric stations . . . . . . . . . . . . . . . . . . . . . . . . 272 20.2.2.1 Streamflow stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 20.2.2.2 River stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 20.2.2.3 Lake and reservoir stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 20.2.2.4 Sediment discharge and sedimentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 20.2.2.5 Water quality stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 20.2.2.6 Water temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 20.2.2.7 Ice cover on rivers and lakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 20.3 Groundwater observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 20.4 Specific requirements for water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 20.4.1 Water quality parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 20.4.2 Surface-water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 20.4.3 Precipitation quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 20.4.4 Sediment quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 20.4.5 Groundwater quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 CHAPTER 21 — COLLECTION OF DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 21.1 Site selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 21.2 Station identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 21.2.1 Identification of data-collection sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 21.2.2 Descriptive information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 21.2.2.1 Station description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 21.2.2.2 Detailed sketch of station location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 21.2.2.3 Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 21.2.2.4 Coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 21.2.2.5 Narrative description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 21.3 Frequency and timing of station visits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298 21.3.1 Manual stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298 21.3.2 Recording stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 21.4 Maintenance of collection sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 21.5 Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 21.5.1 Manual stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 21.5.2 Recording stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303 21.5.3 Real-time reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303 21.5.4 Additional instructions for observers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 21.6 Transmission systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 21.6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 21.6.2 Transmission links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 21.6.3 Factors affecting the choice of transmission systems . . . . . . . . . . . . . . . . 306 21.7 Water quality monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
  • 16. xiv CONTENTS Page 21.7.1 Station identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 21.7.2 Field sheets for water quality monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 21.7.3 Transportation of water quality samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 21.7.4 Field quality assurance in water quality monitoring . . . . . . . . . . . . . . . . . 311 21.8 Special data collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 21.8.1 Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 21.8.2 Bucket surveys of storm rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 21.8.3 Weather-radar and satellite data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 21.8.4 Extreme river stages and discharges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 CHAPTER 22 — DATA REVIEW AND CODING . . . . . . . . . . . . . . . . . . . . . . . . . 315 22.1 Quality control and error detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 22.1.1 Inspection of stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 22.1.2 Preliminary checking of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 22.1.3 Error detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317 22.1.4 Results of quality control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318 22.2 Validation procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 22.2.1 General procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 22.2.2 Combined techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320 22.2.3 Specific validation procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 22.2.3.1 Climatological data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 22.2.3.2 Rainfall data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 22.2.3.3 Snow and ice data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326 22.2.3.4 Water level data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326 22.2.3.5 River-gauging data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 22.2.3.6 Water quality data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 22.2.3.7 Sediment data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331 22.2.4 Missing data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331 22.3 Coding data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 22.3.1 Location codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 22.3.2 Variable (parameter) codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 22.3.3 Data-qualification codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 22.3.4 Missing data codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 22.3.5 Transmission codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 CHAPTER 23 — PRIMARY DATA PROCESSING . . . . . . . . . . . . . . . . . . . . . . . 341 23.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 23.2 Data entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 23.2.1 Key stroking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 23.2.2 Processing of charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
  • 17. CONTENTS xv Page 23.2.3 Manual stations using telemetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346 23.2.4 Automatic station data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 23.2.4.1 Paper-tape and cassette recorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 23.2.4.2 Solid-state memories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 23.3 Processing procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 23.3.1 General primary processing procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 23.3.2 Specific primary processing procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352 23.3.2.1 Climatological data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352 23.3.2.2 Evaporation and evapotranspiration observations . . . . . . . . . . . . . . . . . . . 353 23.3.2.3 Precipitation data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 23.3.2.4 Streamflow data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 23.3.2.5 Water quality data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 CHAPTER 24 — DATA STORAGE AND RETRIEVAL . . . . . . . . . . . . . . . . . . 361 24.1 Archiving of original data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 24.2 Management and storage of processed data . . . . . . . . . . . . . . . . . . . . . . . . . 361 24.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 24.2.2 Controlling data flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 24.2.3 Updating procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 24.2.4 Compression and accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365 24.2.5 Physical-file organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 24.2.6 Logical-file organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 24.2.7 Extraction of single variable data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 24.2.8 On-line versus off-line data storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 24.3 Data retrieval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 CHAPTER 25 — DATA DISSEMINATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 25.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 25.2 Catalogues of information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 25.3 Summary reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 25.4 Publication of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 25.4.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 25.4.2 Frequency of publication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 25.4.3 Contents and format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 25.5 Magnetic media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385 25.5.1 Tapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385 25.5.2 Magnetic discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 25.5.3 Optical discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389 25.6 Real-time data-exchange formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390
  • 18. xvi CONTENTS PART D — HYDROLOGICAL ANALYSIS Page CHAPTER 26 — INTRODUCTION TO HYDROLOGICAL ANALYSIS . . 391 26.1 Methods of analysis in hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 26.2 Scope of Part D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392 CHAPTER 27 — FREQUENCY ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 27.1 The use of frequency analysis in hydrology . . . . . . . . . . . . . . . . . . . . . . . . . 393 27.2 Statistical series and return periods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 27.3 Mathematical approach to frequency analysis . . . . . . . . . . . . . . . . . . . . . . . 394 27.3.1 Probability distributions used in hydrology . . . . . . . . . . . . . . . . . . . . . . . . . 394 27.3.2 Parameter estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 27.3.3 Homogeneity of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 CHAPTER 28 — RAINFALL FREQUENCY AND INTENSITY . . . . . 399 28.1 Rainfall frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 28.1.1 Point rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 28.1.1.1 Adjustment of data for fixed observational time intervals . . . . . . . . . . . . 399 28.1.1.2 Indirect estimation of point rainfall-frequency data . . . . . . . . . . . . . . . . . . 400 28.1.1.3 Maximum observed rainfalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 28.1.2 Area rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 28.1.3 Generalized maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 28.1.4 Drought . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 28.2 Rainfall intensities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406 28.2.1 Point rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406 28.2.2 Area rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408 CHAPTER 29 — STORM-RAINFALL ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . 409 29.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 29.2 Mass curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 29.3 Depth-area duration analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 29.4 Probable maximum precipitation (PMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 29.4.1 Methods of estimating PMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 29.4.2 Preliminary estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 29.4.3 Selection of design rainfall duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 29.4.4 Selection of sub-basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 29.4.5 Storm transposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 29.4.6 Selection and analysis of major storms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414 29.4.7 Maximization of selected storms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 29.4.8 Orientation of storm-rainfall patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415
  • 19. CONTENTS xvii Page 29.4.9 Regional consistency of estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 29.4.10 Estimating in the absence of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418 CHAPTER 30 — INTERPRETATION OF PRECIPITATION DATA . . . . 421 30.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 30.2 Adjustment of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 30.2.1 Standard base period of record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 30.2.2 Double-mass curve analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 30.2.3 Estimation of missing data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 30.3 Areal distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 30.3.1 Illustration by isohyetal maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 30.3.2 Evaluation of physiographic effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 30.4 Computation of areal average precipitation . . . . . . . . . . . . . . . . . . . . . . . . . 425 30.4.1 Arithmetic mean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 30.4.2 Polygon method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426 30.4.3 Isohyetal method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 30.4.4 Per cent normal method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 30.4.5 Hypsometric method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 CHAPTER 31 — SNOW-MELT RUNOFF ANALYSIS . . . . . . . . . . . . . . . . . . . 431 31.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431 31.2 Theory of snow melt at a point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431 31.3 Estimates of catchment melt in the absence of rain . . . . . . . . . . . . . . . . . . 434 31.4 Estimates of catchment melt with rain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 31.5 Estimating snow-melt inflow rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 31.6 Evaporation from a snow cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439 31.7 Probable maximum precipitation and snow melt . . . . . . . . . . . . . . . . . . . . 441 31.7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441 31.7.2 Probable maximum snow accumulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441 31.7.3 Snow-melt estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442 31.8 Runoff from short-period snow melt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442 31.8.1 Plains regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442 31.8.2 Mountainous terrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443 CHAPTER 32 — EVALUATION OF STREAMFLOW DATA . . . . . . . . . . . . 445 32.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445 32.2 Adjustment of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445 32.3 Areal distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 32.3.1 Maps of average annual runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
  • 20. xviii CONTENTS Page 32.3.2 Average runoff from precipitation and temperature data . . . . . . . . . . . . . 447 32.3.3 Correlation between stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450 32.3.4 Effective length of an extended record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452 CHAPTER 33 — RAINFALL-RUNOFF RELATIONSHIPS . . . . . . . . . . . . . . 453 33.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453 33.2 Runoff volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453 33.2.1 Antecedent-precipitation index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453 33.2.2 Initial base flow as an index to runoff volume . . . . . . . . . . . . . . . . . . . . . . . 456 33.2.3 Moisture-accounting techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456 33.3 Temporal distribution of runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 33.3.1 Unit hydrograph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 33.3.1.1 Derivation from streamflow records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 33.3.1.2 Derivation by synthetic methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 460 33.3.1.3 Conversion of unit-hydrograph durations . . . . . . . . . . . . . . . . . . . . . . . . . . . 462 33.3.2 Isochrone method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463 33.4 Distributed models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465 CHAPTER 34 — STREAMFLOW ROUTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 34.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 34.2 Hydrodynamic methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 34.2.1 Complete method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 34.2.2 Diffusion and kinematic routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469 34.3 Hydrological methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 34.4 Reservoir routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473 CHAPTER 35 — LOW-FLOW AND DROUGHT ANALYSIS . . . . . . . . . . . . 475 35.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475 35.2 Flow-duration curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475 35.3 Low-flow frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476 35.4 Statistical analysis of droughts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 35.5 Recession-curve analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479 CHAPTER 36 — FLOOD-FLOW FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . . . . 481 36.1 Station analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 36.1.1 Peak flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 36.1.2 Statistical analysis of flood hydrographs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 36.2 Regionalization of flood flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
  • 21. CONTENTS xix Page 36.2.1 The index-flood procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483 36.2.2 Regression-based procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485 CHAPTER 37— ESTIMATING LAKE AND RESERVOIR EVAPORATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 37.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 37.2 Water-budget method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 37.2.1 Inflow and outflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 37.2.2 Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 37.2.3 Net seepage and bank storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 37.2.4 Change in reservoir storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 37.3 Energy-budget method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 37.3.1 Reflected long-wave radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491 37.3.2 Radiation emitted by the reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491 37.3.3 Change in energy storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492 37.3.4 Energy utilized for evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493 37.3.5 Energy convected to or from the body of water as sensible heat . . . . . . 493 37.3.6 Energy advected by the evaporated water . . . . . . . . . . . . . . . . . . . . . . . . . . . 493 37.3.7 Energy exchange between the water in the reservoir and its bottom . . 493 37.3.8 Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495 37.4 Aerodynamic approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495 37.4.1 Value of the coefficient N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496 37.4.2 Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497 37.4.3 Water-surface temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497 37.4.4 Humidity or vapour pressure of the air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497 37.4.5 Eddy-correlation method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498 37.5 Combination of aerodynamic and energy-balance equations . . . . . . . . 498 37.6 Extrapolation from pan measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504 CHAPTER 38 — ESTIMATING BASIN EVAPOTRANSPIRATION . . . . 507 38.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507 38.2 Potential evapotranspiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507 38.3 Actual evapotranspiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507 38.4 Water-budget method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 38.4.1 Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 38.4.2 Streamflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 38.4.3 Change in storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 38.4.4 Deep seepage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 38.5 Energy-budget method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 38.6 Aerodynamic approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509
  • 22. xx CONTENTS Page 38.7 Penman-Monteith method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 38.8 Priestley-Taylor (radiation) method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 38.9 Complementary equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 CHAPTER 39 — MODELLING OF HYDROLOGICAL SYSTEMS . . . . . 513 39.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513 39.2 Black-box models (system approach) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514 39.3 Conceptual models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515 39.3.1 Model of the Hydrometeorological Centre of the former U.S.S.R. . . . 516 39.3.2 Sacramento model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517 39.3.3 Tank model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 519 39.3.4 Selection of models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522 39.4 Hydrodynamic models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522 39.5 Parameter evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525 39.6 Stochastic simulation of hydrological time-series . . . . . . . . . . . . . . . . . . . 526 39.6.1 Markovian lag-1 models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527 39.6.2 Autoregressive moving average (ARMA) models . . . . . . . . . . . . . . . . . . 527 39.6.3 Fractional gaussian noise and broken-line process models . . . . . . . . . . . 528 39.7 Water quality modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 39.7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 39.7.2 Types of models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 39.7.3 Models of the pollutant transport in rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . 530 39.7.4 Applications and examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531 39.8 Selection of models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532 CHAPTER 40 — MEASUREMENT OF PHYSIOGRAPHIC CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537 40.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537 40.2 Reference systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537 40.3 Point measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538 40.4 Linear problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538 40.4.1 The stream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539 40.4.2 The drainage network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539 40.4.3 Stream profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540 40.4.4 The drainage network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541 40.4.5 Cross-section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541 40.4.6 Physical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 542 40.5 Area measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 542 40.5.1 The basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 542 40.5.2 The grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548
  • 23. CONTENTS xxi Page 40.6 Volumetric measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 40.6.1 Bathymetric methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 40.6.2 Topographical methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 40.7 Geographical information systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550 PART E — HYDROLOGICAL FORECASTING CHAPTER 41 — INTRODUCTION TO HYDROLOGICAL FORECASTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 41.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 41.2 Characteristics of forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 41.3 Effectiveness of hydrological forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553 41.3.1 Accuracy and timeliness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554 41.3.2 Costs and benefits of hydrological forecasts . . . . . . . . . . . . . . . . . . . . . . . . . 554 41.4 The hydrological forecasting service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558 41.4.1 Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558 41.4.2 Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559 41.5 Dissemination of forecasts and warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . 559 CHAPTER 42 — DATA REQUIREMENTS OF HYDROLOGICAL FORECASTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563 42.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563 42.2 Data for developing forecast procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563 42.2.1 Hydrological variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564 42.2.2 Catchment characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564 42.2.3 River characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564 42.3 Data required for forecast operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564 42.3.1 Rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565 42.3.2 Snow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565 42.3.3 Water levels and streamflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565 42.3.4 Other data requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566 42.4 Use of meteorological forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566 42.5 Precision of observations and frequency of measurement . . . . . . . . . . . 567 42.6 Operational data acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567 42.6.1 Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567 42.6.2 Remote sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567 42.6.2.1 Radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 570 42.6.2.2 Satellite-based methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571 42.6.2.3 Aircraft sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573 42.6.3 Communication systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573 42.6.3.1 Satellite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574
  • 24. xxii CONTENTS Page 42.6.3.2 Meteor burst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575 CHAPTER 43 — FORECASTING TECHNIQUES . . . . . . . . . . . . . . . . . . . . . . . . 577 43.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 43.2 Correlation and regression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 43.3 Moisture index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579 43.4 Crest stage forecasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 580 43.5 Flow forecasts based upon storage volume . . . . . . . . . . . . . . . . . . . . . . . . . . 582 43.6 Recession forecasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582 43.7 Conceptual streamflow models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582 43.8 Flow routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583 43.9 Time-series analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583 43.10 Forecast-adjustment techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584 43.11 Probability forecasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586 CHAPTER 44 — FLOOD AND WATER-SUPPLY FORECASTS . . . . . . . . 589 44.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589 44.2 Flood forecasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589 44.3 Flash floods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590 44.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590 44.3.1.1 Forecast programmes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590 44.3.1.2 Alarm systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591 44.3.1.3 Watches and warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591 44.3.1.4 Flash floods and water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591 44.3.2 Flooding in urban areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592 44.3.3 Dam break . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592 44.4 Storm surges in rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 593 44.5 Water supply forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594 44.6 Low flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596 CHAPTER 45 — SNOW-MELT FORECASTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 45.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 45.2 Snow-melt runoff processes in lowland and mountain rivers . . . . . . . . 597 45.3 Forecast models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598 45.3.1 Index methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598 45.3.2 Conceptual models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 599 45.3.3 Extended streamflow prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600 45.3.4 Input data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 601 45.4 Short- and medium-term snow-melt runoff forecasts . . . . . . . . . . . . . . . . 601
  • 25. CONTENTS xxiii Page 45.5 Long-term snow-melt forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602 45.6 Seasonal snow-melt forecasts for the plains regions . . . . . . . . . . . . . . . . . 602 45.7 Seasonal snow-melt forecasts for mountainous regions . . . . . . . . . . . . . . 603 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604 CHAPTER 46 — FORECASTS OF ICE FORMATION AND BREAK-UP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605 46.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605 46.2 Forecasts of ice formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605 46.3 Forecasts of ice break-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608 46.3.1 Forecasts of ice break-up on reservoirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608 46.3.2 Forecasts of ice break-up on rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609 46.4 Long-term ice forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609 46.4.1 Ice formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610 46.4.2 Ice break-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610 46.4.3 Use of atmospheric circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611 PART F — APPLICATIONS FOR WATER MANAGEMENT CHAPTER 47 — INTRODUCTION TO APPLICATIONS FOR WATER MANAGEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613 47.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613 47.2 Purposes to be served by a water-management project . . . . . . . . . . . . . . 613 47.3 Multi-purpose projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614 47.4 Water-resources systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614 47.5 Preliminary investigation of water-management projects . . . . . . . . . . . . 614 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 618 CHAPTER 48 — SUSTAINABLE WATER DEVELOPMENT . . . . . . . . . . . 619 48.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619 48.2 The changing nature of the resource . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619 48.2.1 Natural changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619 48.2.2 Man-induced changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620 48.3 Changing attitudes to management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620 48.3.1 Watershed management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622 48.3.2 Management fragmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622 48.4 Water-data programmes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623 48.4.1 Assessing data needs for the future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623 48.4.2 Network character and relevance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624 48.4.3 Network-strategy options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625 48.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 626 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 626