1. INTERCEPTION, DEPRESSION
STORAGE AND INFILTRATION

2. Interception – loss of rainfall due to vegetation (from
trees to grass)
rainfall
throughfall
stemflow
Interception = f (vegetation (age, density, type), season, rain intensity, antecedent
conditions)
Forest cover data collected by placing rain gauges under forest canopy and
comparing with gauge data from open area.

3. Factors affecting interception
• Storm characteristics
The number and spacing of precipitation
events, intensity and amount of
precipitation
Wind speed
• Vegetation characteristics
Species, age, density, and condition of
vegetation

4. Estimation of interception
Li = Si + KEt
Li = volume of water intercepted (inches)
Si = interception storage that will be retained on the
foliage, (0.01 to 0.05 in)
f (wind, gravity, type)
K = ration of surface area of intercepting leaves to
horizontal projection of tree area,
Light storms K = 100%
Heavy storms K = 10 to 40 %
E = amount of water evaporating per hour during
precipitation (in/hr)
t = time, hrs

5. DEPRESSION STORAGE
• Depression storage, or ponding, is that
water on a drainage a drainage basin that
drains into closed depressions and never
reaches the outlet of the basin.
• This water becomes trapped in ponds;
some eventually evaporates and the
remainder infiltrates into the ground.
• Depression storage occurs on most
basins.

6. INFILTRATION
• Infiltration is the vertical movement of
water through the soil surface.
• Similar terminology:
percolation into the soil
seepage out of the soil

7. Factors influencing infiltration:
• condition of soil surface and vegetative
cover
• soil properties (moisture content, porosity,
hydraulic conductivity)
• antecedent moisture conditions
• rainfall intensity

8. • Infiltration is highly related to soil
properties.
• Our ability to physically represent the
infiltration process is related to being able
to represent soil properties.
• However, soils exhibit a great deal of
variability spatially and vertically.
• Thus our representations generalize over
a large variability of soil characteristics

9. Process of infiltration,
Moisture content
soil moisture description
Soil water zone – max depth from which
water can be returned to surface through Saturated zone
capillary action or ET.
Transmission zone,
Gravitational water – flow direction uniform moisture
is vertical due to gravity. content, not saturated
(unsaturated zone or zone of
aeration)
Capillary zone, less than
atmospheric pressure
Wetting front
Groundwater, saturation at atmospheric pressure

10. Moisture Content:
Total volume = air volume (voids) + solid volume
η, porosity = volume of voids ÷ total volume
θ, soil moisture content = volume water ÷ total volume
maximum θ = η

11. Measurement:
Initial efforts to describe infiltration are based on measured data.
Split (double) ring infiltrometer
• shown to represent Horton parameters fairly well.
• Measure rate of vertical movement from center ring
• Exterior ring to offset lateral movement of moisture
• Change in elevation measured at selected time intervals
(commonly use a point gauge).
• Actually measures maximum infiltration capacity because
excess water is available.
35 cm
23 cm

12. Sprinkler infiltrometer
catch and measure runoff rate
infiltration rate = “rainfall” rate - runoff rate12’6’
usually have high application rate therefore
approaching maximum infiltration rate

13. Runoff

14. RUNOFF
Runoff or overland flow will occur if the amount of
water falling on the ground is greater than the
infiltration rate of the surface,.
Runoff specifically refers to the water leaving an
area of drainage and flowing across the land surface
to points of lower elevation.
It is not the water flowing beneath the surface of the
ground.
This type of water flow is called throughflow.

15. Runoff involves the following events:
• Rainfall intensity exceeds the soil's infiltration
rate.
• A thin water layer forms that begins to move
because of the influence of slope and gravity.
• Flowing water accumulates in depressions.
• Depressions overflow and form small rills.
• Rills merge to form larger streams and rivers.
• Streams and rivers then flow into lakes or
oceans.

16. Runoff on a global scale
• Surface runoff sends 7 % of the land based precipitation back to the
ocean to balance the processes of evaporation and precipitation.
Continent Runoff Per Unit Area (mm per yr.)
Europe 300
Asia 286
Africa 136
North and Central America 265
South America 445
Australia, N.Zealand and New 218
Guinea
Antarctica and Greenland 165

17. Streamflow and Stream Discharge
• The term streamflow describes the process of
water flowing in the organized channels of a
stream or river.
• Stream discharge represents the volume of
water passing through a river channel during a
certain period of time.
• Stream discharge can be expressed
mathematically with the following equation:
Q=WxDxV
– where,
– Q equals stream discharge usually measured in cubic
meters per second, W equals channel width, D equals
channel depth, and V equals velocity of flowing water.

18. Stream hydrograph
• Because of streamflow's potential hazard to humans
many streams are gauged by mechanical recorders.
These instruments record the stream's discharge on a
hydrograph.

19. From this graph we can observe the following things:
A small blip caused by rain falling directly into the channel is the first evidence
that stream discharge is changing because of the rainfall.
A significant time interval occurs between the start of rain and the beginning of
the main rise in discharge on the hydrograph. This lag occurs because of the time
required for the precipitation that falls in the stream's basin to eventually reach the
recording station. Usually, the larger the basin the greater the the time lag.
The rapid movement of surface runoff into the stream's channels and
subsequent flow causes the discharge to rise quickly.
The falling limb of the hydrograph tends to be less steep that the rise. This flow
represents the water added from distant tributaries and from throughflow that
occurs in surface soils and sediments.
After some time the hydrograph settles at a constant level known as base flow
stage. Most of the base flow comes from groundwater flow which moves water
into the stream channel very slowly.

20. the shape and magnitude of the hydrograph is controlled by two sets of factors:
Permanent Factors - slope of basin, soil structure, vegetation, channel density,
etc.
Transient Factors - are those factors associated with precipitation input - size of
storm, intensity, duration of rainfall, etc.

21. Runoff Models
Historical Perspective
The development and application of hydrological models have gone through a long
time period, the remarkable dates in the history of the development of
hydrological models are:
The origins of rainfall-runoff modelling in the broad sense can be found in the
middle of the 19th century, when Mulvaney (1850), an Irish engineer who
used in the first time the rational equation to give the peak flow Qp as:
Qp = CiA
Where,
C is the coefficient of runoff (dependent on catchment characteristics)
i is the intensity of rainfall in time Tc and
A is the area of catchment.
Tc is the time of concentration, the time required for rain falling at the farthest
point of the catchment to flow to the measuring point of the river.

22. A major step forward in hydrological analysis was the concept of the unit
hydrograph introduced by the American engineer Sherman in 1932 on the basis
of superposition principle.
The use of unit hydrograph made it possible to calculate not only the flood peak
discharge (as the rational method does) but also the whole hydrograph (the
volume of surface runoff produced by the rainfall event).
The real breakthrough came in the 1950s (Todini, 1988) when hydrologists
became aware of system engineering approaches used for the analysis of
complex dynamic systems. This was the period when conceptual linear models
originated (Nash, 1958, 1960).
Many other approaches to rainfall-runoff modelling were considered in the 1960s.
A large number of conceptual, lumped, rainfall-runoff models appeared thereafter
including the famous Stanford Model IV (Crawford and Linsley, 1966) and the
HBV model (Bergström and Forsman, 1973).
Stochastic time series models were first introduced by Box and Jenkins (1970)
which provided hydrologists with an alternative model type.

23. One remarkable model developed in the late 1970s is the TOPMODEL (Beven and
Kirkby, 1979) that is based on the idea that topography exerts a dominant control on
flow routing through upland catchments is called.
To meet the need of forecasting (1) the effects of land-use changes, (2) the effects
of spatially variable inputs and outputs, (3) the movements of pollutants and
sediments, and (4) the hydrological response of ungauged catchments where no
data are available for calibration of a lumped model, the physically-based
distributed-parameter models were developed. The Systéme Hydrologique
Européen (SHE) model is a excellent example of such models (Abbott et al., 1986).

24. The macro-scale hydrological models were developed on the basis of the following
motivations.
1. First, for a variety of operational and planning purposes, water resource
managers responsible for large regions need to estimate the spatial
variability of resources over large areas, at a spatial resolution finer than
can be provided by observed data alone.
2. Second, hydrologists and water managers are interested in the effects of
land-use and climate variability and change over a large geographic
domain.
3. Third, there is an increasing need of using hydrologic models as a base to
estimate point and non-point sources of pollution loading to streams.
4. Fourth, hydrologists and atmospheric modellers have perceived
weaknesses in the representation of hydrological processes in regional
and global atmospheric models.
5. Examples of GIS supported macro-scale hydrological models include
those developed by Vörösmarty et al. (1989), the VIC model (Wood et al.,
1992) and the Macro-PDM (Arnell, 1999). These models are state-of-the-
art tools in assessing regional and continental scale water resources.

25. Applications of hydrologic models
Nowadays, mathematical models have taken over the most important tasks in
problem solving in hydrology. The important applications of hydrological model are
summarised below:
Design Operation
Dams and reservoirs Flow forecasting
design Reservoir control
water yield Urban storm drain control
capacity, failure Management
Floods Land-use changes
frequency Climate changes
mapping Point/nonpoint pollution
Urbanisation Groundwater recharge
storm drains Research and teaching
flood plains University training
channel alterations Industrial training
Irrigation and drainage Research

26. Runoff models are probably what most hydrologists spontaneously refer to when
discussing hydrological models.
This was also the first branch in which models were used when computers
became easily available in the 1970s.
The basic principle in hydrological modelling is that the model is used to calculate
river flow based on meteorological data, which are available in a basin or in its
vicinity.
Hydrological models include subroutines for the most significant hydrological
processes, such as snow accumulation and melt at different elevations, soil
moisture dynamics, evapotranspiration,recharge of groundwater, runoff
generation and routing in lakes and rivers.
Most runoff models are based on the water balance, using precipitation as a
driving variable and calculating the quantities directed as runoff, R, from the water
balance equation,
R = P – E – DS,
where P is precipitation, E evapotranspiration, and DS represents various storage
terms.

27. Runoff and Hydrologic Modeling (RS)
Runoff cannot be directly measured by remote sensing
techniques.
However, there are two general areas where remote
sensing can be used in hydrologic and runoff modeling:
4. determining watershed geometry, drainage network,
and other map-type information for distributed
hydrologic models and for empirical flood peak, annual
runoff or low flow equations; and
5. providing input data such as soil moisture or delineated
land use classes that are used to define runoff
coefficients

28. • Remote sensing data can be used to obtain almost any
information that is typically obtained from maps or aerial
photography.
• In many regions of the world, remotely sensed data, and
particularly Landsat, Thematic Mapper (TM) or Systeme
Probatoire, d'Observation de la Terre (SPOT) data, are the
only source of good cartographic information.
• Drainage basin areas and the stream network are easily
obtained from good imagery, even in remote regions
• Topography is a basic need for any hydrologic analysis and
modeling.
• Remote sensing can provide quantitative topographic
information of suitable spatial resolution to be extremely
valuable for model inputs. for example, stereo SPOT
imagery can be used to develop a Digital Elevation Model
(DEM) with 10 m horizontal resolution and vertical
resolution approaching 5 m in ideal cases

29. • Empirical flood formulae are useful for making
quick estimates of peak flow when there is very
little other information available.
• Generally these equations are restricted in
application to the size range of the basin and the
climatic/hydrologic region of the world in which
they were developed.
• Most of the empirical flood formulae relate peak
discharge to the drainage area of the basin.
• Landsat data have been used to improve empirical
regression equations of various runoff
characteristics

30. MIKE BASIN - MIKE 11's rainfall-runoff model NAM
• Given rainfall and evaporation data, NAM calculates a
runoff time series that is automatically assigned to MIKE
BASIN for use in the river flow simulation.
• NAM is a lumped, conceptual rainfall-runoff model
simulating overland flow, interflow and baseflow as a
function of the moisture content in each of four mutually
interrelated storages:
• Snow storage
• Surface storage
• Root zone storage

32. MIKE 11 is a comprehensive, one-dimensional modelling system for the simulation of
flows, sediment transport and water quality in estuaries, rivers, irrigation systems and
other water bodies.
It is a 4th generation modelling package designed for microcomputers with DOS or
UNIX operating systems and provides the user with an efficient interactive menu and
graphical support system with logical and systematic layouts and sequencing in the
menus.
The package was introduced in 1989 and today the number of installations world-wide
exceeds 300.
The hydrodynamic module of MIKE 11 is based on the complete partial differential
equations of open channel flow (Saint Venant).
The equations are solved by implicit, finite difference techniques.
The formulations can be applied to branched and looped networks and quasi two-
dimensional flow simulations on floodplains.
MIKE 11 operates on the basis of information about the river and the floodplain
topography, including man- made hydraulic structures such as embankments, weirs,
gates, dredging schemes and flood retention basins.
The hydrodynamic module forms the basis for morphological and water quality studies
by means of add-on modules.

33. MIKE21 is a comprehensive modelling system for 2-dimensional free surface
flows applicable to studies of lakes, reservoirs, estuaries, bays, coastal areas
and seas where stratification can be neglected.
MIKE21 solves the vertically integrated equations of continuity and conservation
of momentum in two horizontal dimensions.
Like MIKE11, MIKE21 has a modular structure where water quality modules and
sediment transport modules are available as add-on modules to the MIKE21
hydrodynamic module.

34. Integrated Hydrological Modeling
MIKE 3
MIKE SWMM
MIKE SHE

35. An Integrated Hydrological Model
Traditional Models Integrated Model
Evapotrans-
piration
Unsaturated
zone Unsaturated Evapotrans-
zone piration
Groundwater
flow
Groundwater
Surface Water/ Surface Water/
flow
Overland flow Overland flow

36. MIKE SHE – An example of an
integrated model
Overland
flow
Unsaturated
zone Surface
water
Groundwater
flow

37. Why not one model?
MIKE 3
MIKE SWMM

38. Different models offer
MIKE FLOOD
solutions to various problems,
MIKE BASIN
MIKE SHE
with different approach/focus/
MIKE 21
MIKE 11
level of detail
Flood forecasting, flood management
Dam break analysis
Reservoir operation
River management, navigation
Sediment transport, river morphology
River water quality
River ecology
Groundwater & surface water interaction
Wetlands
Basin-wide water resources planning
Soil & groundwater contamination
Watershed management
Irrigation, canal operation

39. MIKE SHE
Application Areas
• River Basin planning, water use/allocation
• Irrigation and drainage
• Wetland protection, restoration and ecology
• Impacts of farming practices
• Soil and water management
• Effects of changes in land use
• Effects of changes in climate
• Contamination from waste disposal sites
• Saline related problems (not released yet)

40. MIKE SHE
Flexible Process Descriptions
Processes can be mixed as required
Processes run on different spatial scales
Processes run on different time scales

41. MIKE SHE
MIKE SHE has been used in hundreds
of consulting and research projects
around the world

42. Web-address: www.dhi.dk

43. Trends in hydrological modeling
• Models → modules in integrated, flexible
modeling systems
• Hydrological models become integrated with
other tools (GIS, statistical, economic,
optimization, decision support tools, remote
sensing)
• Models describe natural, as well as human
influences on water flow and distribution
• Models describe water quality as well as quantity

44. Hydrometeorological data requirements
Rainfall, evapotranspiration, surface water levels, water table depth
2.0
1.8
Water Level (m OD)
1.6
1.4
1.2
SB e
1.0 SB g
SB h
0.8
21/12/98
09/07/99
25/01/00
12/08/00
16/11/97
04/06/98
0.2
0.0
6
-0.2
5
-0.4
Water Table Depth (m)
Potential Evapotranspiration (mm)
4
-0.6
3
-0.8 1
2
2
-1.0 9
1
10
-1.2 11
0
25/06/98
25/12/98
25/06/00
25/06/97
25/09/97
25/12/97
25/03/98
25/09/98
25/03/99
25/06/99
25/09/99
25/12/99
25/03/00
-1.4
01/12/96 19/06/97 05/01/98 24/07/98 09/02/99 28/08/99 15/03/00 01/10/00 19/04

45. Hydrogeological data requirements
• Sub-surface geology conceptual model
• Geologic properties (Kx, Storage, etc)
• Pumping rates
• Boundary conditions
• Surficial geology
• Soil properties
• Vegetation properties (root depth, LAI, etc)

46. MIKE 11 Hydrology Data Requirements
• Detailed topography
• Channel cross sections
• Channel network
• Control structures
• Flow cond’s at boundaries

47. Steps in modeling
1. Define purpose of modeling
2. Determine model to use
3. Setup model
4. Calibrate model
5. Apply model:
• Prediction
• Scenario analysis
• Optimization

48. Model setup/input
River network/Topography/Soils/Landuse
Precipitation, ET
Non-point Initial
sources conditions
Point
sources
Boundary
conditions Geology,
soils

49. Model animation

50. MIKE BASIN
balances
water with water
needs availability

51. Setup of MIKE BASIN
Diversion point Ground
water
Reservoir
Intake
Water
Irrigation Runoff
supply
area
Return flow Hydro-
Catchment power
Flow target
Irrigation Intake
area

52. MIKE SHE <-> MIKE BASIN
MIKE SHE MIKE BASIN
Detailed, physically Simple, nodal based
based routing
For process, cause- For water allocation
effect understanding
Focus on soil, Focus on riverflow
groundwater processes

53. Constraints for modeling
• Insufficient data:
– Not available, non-existing
– Poor quality
– Not accessible
• Models costly, complex, non-transparent,
time-consuming
• No tradition for modeling
• No faith in models

54. Perspectives for modeling in the
CP
Project participants:
• Think modeling from the conception of a project
• Plan for data collection in coordination with modeling
• Modeling as an integrated part of the project
• Coordinate approaches across projects
Modellers:
• Provide capacity building and support to concrete
projects
• Continue making models more user-friendly, flexible (in
complexity, scale) and integrated