1. Groundwater Management Concept
• Watershed concepts: water management, land management,
integrated management
• Groundwater supply management
• Artificial recharge enhancement
• Spring protection and development
• Groundwater demand management
• Adaptive management of groundwater

2. What is a Watershed?
 A watershed is an area that drains water to a
common outlet on the stream network
 It is a land area that captures rainfall and conveys
the overland flow and run off to an outlet in the
main flow channel
 The boundary between two watersheds is
referred to as a watershed boundary or
drainage divide.
 Other terms for a watershed are basin, catchment,
or contributing area.
 Catchment is another term synonymous to
watershed or drainage basin

3. From McKnight, Physical Geography

5. • A small watershed of few hectares draining into a small
stream may form part of larger watershed, which in turn may
form larger watershed, which in turn may form part of a still
larger watershed.
• All combined watershed may become a major river basin
draining millions of square kilometers of land
• Watershed of small streams are the sub-watersheds of the
larger stream.
• A watershed may be nearly flat or may include hillocks, hills
or mountains.
• Each and every land or water area is part of one or the other
watershed
Extent and size of Watershed

6. Fig. Ridges act as water divide and form limits of watershed

7. Watershed geology
 The geology controls watershed hydrological
reaction.
 A watershed that has an impermeable substrate
presents a faster and violent increase of the
runoff in comparison to a watershed with a
permeable substrate.
 A watershed with a permeable substrate will
provide a base runoff during dry periods that
will last longer.
 is essential for groundwater flow, through the
identification of the karst areas

8. Explanation river drainage direction reversal

9. Land use and soil characteristics of watershed
 Common types of land use and land cover includes urban, agricultural land,
forest land, water, wetland, barren land and perennial snow or ice
 Land use and soil characteristics affect both the volume and timing of
runoff
 The land in a watershed has to be used for numerous purposes like
cultivation forestry, livestock production, housing, water harvesting etc.
 The land use affects rate of runoff, infiltration and types and quality of
vegetation.
 Suitable land use minimizes the soil erosion and reduces the runoff
 A lot of information about land use available from maps as GIS data
sets with associated reports
 The map is constructed mainly by interpreting remotely sensed such as
aerial photograph and satellite image.
 In some cases, a field survey is necessary to determine the various land
uses within a watershed

10. Example for Land use/land cover map and the raw data
from which it is constructed
Fig. a) MODIS (Moderate Resolution Imaging Spectroradiometer) image
for Ziway-Awasa basin, Ethiopian Rift Valley; b) Land cover map of the
basin as derived from MODIS monthly composites (Source: Bedru Sherefa,
2006).
a)
b )

12. The rate and magnitude of soil erosion and sedimentation are vital for
watershed community
• adversely effects the productivity and production on agricultural
horticultural, forest lands and grasslands; (at higher elevation)
• results in higher production due to transportation of silt and
sediments into the rivers and reservoirs and then on agricultural
land but also results into the reduction of life and benefits of the
reservoir; ( in plains)
• results in situation of streams and rivers which causes flash floods;
• results in severe drought due to low soil infiltration, excessive
runoff etc;
• results in converting useful economic assets into useless
commodities by formation of ravines
Soil

13. Water quality, quantity and regime are influenced by
watershed conditions
Runoff
- results into loss if water from the watershed which
could have been utilized by the community for
drinking, domestic use, irrigation, industry
- results in sheet grill, gully or ravenous erosion of soil
from the watershed
- leads to decline in ground water table and effects
recharge adversely
- results in damage to property and life
WATER

14. The type, quantity and quality of vegetative cover in watershed
influences runoff, erosion and sediment production, rate of
evaporation and infiltration rate
• The first effect of vegetation is to intercept a portion of the
rain through the process of wetting the leaves, branches and
stem.
• In dense vegetation, shrubs and grasses, this intercepted
moisture may be substantial.
• Following the end of precipitation a portion of this moisture
falls to the ground due to wind.
• This delayed precipitation prolongs the period of rainfall
at the ground surface and tends to increase infiltration into
the ground.
• The second influence of vegetation is to protect and shade
the soil
Vegetative cover

15. (a) Size: The size or area of a watershed is an important parameter in
determining the peak rate of runoff. The rate and volume of runoff
increase with size of the watershed area.
(b) Shape: Long and narrow watersheds are likely to have longer time of
concentration resulting in lower runoff rates than square shaped
watershed of the same size.
The longer it takes water to leave the watershed, the move the opportunity or
the water to infiltrate in the soil.
c) Land Slope
• The speed and extent of runoff depends on he shape of the land.
• The velocity of flow if the runoff increases with increase in land slope.
• The erosive capacity of the runoff is directly proportional to the slope of land
on which the runoff occurs. Thus soil erosion also increases with increase in
slope. The land use is also determined by the slope
(d) Drainage density and pattern
• High drainage density watershed drains runoff water rapidly
• Drainage pattern is influenced by the slope, lithology, structure,
distribution of rock systems etc. The coarser the drainage texture, the
higher the conductivity
Watershed Characteristics

18. • Watershed management may be defined as the process of
formulating and carrying out a course of action involving
manipulation of natural, agricultural and human resources
of a watershed to provide resources that are desired by and
suitable to the watershed community, but under the
condition that soil and water resources are not adversely
affected.
• Watershed management must consider the social, economic
and institutional factors operating within and outside the
watershed management practices are there changes in land
use vegetative cover and other non-structural and structural
actions that are taken on a watershed to achieve watershed
development objections.
watershed management

19. • Watershed management is an integrated and
interdisciplinary approach.
• It generally requires land use adjustment measures which
contribute to the reduction in soil erosion rates vis – a – vis
increased agricultural production generation of neutral
employment and balanced growth of national economy
• Watershed management usually involves the use, by the
people of the watershed are a of the watershed natural
resources, especially the land, water and vegetation, with
the active participation of their institutions and
organizations and in harmony with eco-system

20. • Conserving soil and water
• Improving the ability of land to hold water
• Rainwater harvesting and recharging
• Growing greenery – trees, crops and grasses
The objectives of watershed management

22. • Groundwater supply can be increased through recharge or
supplemented with surface water
• Conjunctive management with surface water supplies can
increase groundwater sustainability
• Supply measures includes
• water harvesting measures
• water retention measures
• protecting natural recharge
• Conjunctive use
• Enhanced aquifer recharge
Groundwater supply management