CHARACTERISTICS OF WATERSHED: size, shape; physiography, slope, climate, drainage, land use, vegetation, geology and soils, hydrology and hydrogeology, socio-economic characteristics, basic data on watersheds.

1. CHARACTERISTICS OF
WATERSHED
(WATERSHED MANAGEMENT)
UNIT – II
Rambabu Palaka, Assistant ProfessorBVRIT

2. Learning Objectives
1. Climatic Characteristics
Rainfall & its movement, Intensity, Duration, Temperature, Wind
Velocity, Humidity, Transpiration, and Evaporation
2. Physiographic Characteristics
Size, Shape, Slope, Drainage Density, Elevation, Land use, Vegetation
Cover, Soil, Geology, Hydrology, Hydrogeology
3. Socio-economics Characteristics
Statistics on people and their health, wants & wishes, Cattle and
Farming Practices, People Participation

3. Watershed Characteristics
Each and every watershed has distinct characteristics of its own.
No Two Watersheds are Identical
1. Climatic Characteristics
2. Physiographical Characteristics
All the above characteristics affect the pattern of disposal of stream flow

4. Micro-Watershed near Moosapet Village,
Narsapur Mandal, Medak District, Telanagana State
Case Study

6. Moosapet Tank

7. Moosapet Tank

8. Common Point
(Tank Outlet)

9. Climatic Characteristics
 If the climatic condition is dry before the rainfall, loss of runoff is more
due to infiltration and evapotranspiration.
Climatic condition depends on Temperature, Wind Velocity, and Humidity
Transpiration, Evaporation, and Evapotranspiration depends on Climatic Condition
 The more the intensity of rainfall in the watershed, the more is the peak
flow disposal from the area.
 If the duration is less, time taken to dispose with lower peak flow is also
less

10.  If the rain moves downstream, the peak stream flow of watershed
occurs quickly
 If rain moves upstream, the peak flow occurs late

12. Climatic Characteristics
For the correct design of hydraulic structures like
 Dams
 Weirs
 Barrage
 Reservoirs
 Spillways
 Retaining walls
 Embankments
a peak flow assessment of run-off or flood should be
accurately worked out

13. Physiographic Characteristics
Shape:
 Watersheds differ in their shape based on morphometric parameters like
geology and structure.
 The shape of watershed has a dominant effect on the characteristics of
the hydrograph of the watershed such as peak flow, overland flow, and
base of hydrograph (run-off time).

15. Physiographic Characteristics
Size:
The size of watershed is governed by the size of stream or river and the
development and management works taken.
 For minor irrigation project, size may be few hundred square kilometers
 For Tank or Pond Irrigation, size is just few square kilometers
 In Watershed management works in hilly or undulating topography, the size of
watershed may be even much smaller .
Measurement of precipitation as well as water retention, drainage from the
watershed complex for a bigger size of watershed

16. Influence of Basin Area on Runoff Volume

17. Influence of Basin Size on Runoff

18. Physiographic Characteristics
Slope:
It controls the rainfall distribution and movement, land utilization and watershed
behavior.
If slope is more,
 the velocity is more, and hence flood water drains quickly
 results in higher peak discharge
 reduces infiltration
 increases the soil transportation

19. Influence of Basin Sloe of Runoff
Gentle slope indicates lesser runoff and Steeper slope indicates higher runoff

20. Physiographic Characteristics
Drainage:
The Stream Order, Drainage Pattern, and Drainage Density have a profound
influence on watershed as to runoff, infiltration, land management etc.
 It determines the flow characteristics and erosional behavior.
 If drainage density is more, peak runoff is more.

22. Stream Order (Strahler)
 First and Second order streams
generally form on steep slopes and flow
quickly until they slow down and meet
the next order waterway.
 First to Third Order Streams generally
found in upper reaches of watershed
Streams that are classified through 4th
to 6th are called as medium streams
 If Stream order is larger than 6th is
considered as river.

23. Drainage Pattern

24. Pattern Description Controlling influences
Dendritic
random, tree-like branching
pattern
flat-lying sedimentary rock, thick
sediment, or homogeneous rock
uninterrupted by fractures
Trellis
long (subsequent) streams follow
strike valleys fed by short
tributaries descending from
adjacent obsequent and dip slopes
developed in differentially eroded
fold belts containing Lithology of
varying strengths
Radial
tributaries radiate away from a
central region
central highland such as a volcano
or eroding pluton surrounded by
sedimentary rock
Rectangular tributaries make right angle bends jointed or faulted bedrock
Drainage Patterns

25. Physiographic Characteristics
Physiography:
Type of land, its altitude and physical disposition immensely speak about a
watershed as to the climate and planning the activities in greening.
 Hilly tract could be useful mainly for Forestry
 Plains of populated areas could be utilized for Crops

26. Physiographic Characteristics
Land Use:
The land in watershed is used for numerous purposes such as
 dwelling houses
 cultivation
 livestock
 water harvesting
 roads and railways
Land use affects the run-off rates.

27. Physiographic Characteristics
Vegetation Cover:
 Vegetation cover retard the flow and increases the infiltration and interception,
there by reducing the peak flow.
 Vegetation cover protects the soil erosion.
Detailed information on vegetation helps in choosing type, mode and manner of
greening the watershed

28. Physiographic Characteristics
Soil:
 The soil such as sand absorbs a larger part of run-off water, so the rate of flow is
less. Clay soil produces more flow as its absorption is less.
 Soil parameters such as depth, nature, moisture and fertility determines crops.

29. Physiographic Characteristics
Geology:
Rocks and their structure control formation of a watershed itself because their nature
determines size, shape, physiography, drainage, and groundwater conditions.
 Geological conditions affects the run-off of watershed. If there are some cracks in
rocks joining surface water and groundwater, a part of water flows quickly
underground.
 Lakes, Storages, Swamp hold a part of excess rainfall

30. Physiographic Characteristics
Hydrology:
The availability, quality and distribution of surface water is basic to the final goal of
growing greenery in a watershed.
 Hydrological parameters such as intensity and duration of rainfall help in
quantification of water available in watershed.
 If rainfall continues for longer period with low intensity, evaporation and
percolation increases but run-off is less. Further it may cause landslide in sloping
hillside areas.

31. Physiographic Characteristics
Hydrogeology:
The groundwater demand for irrigation, farm plantation, drinking water , domestic
use and industrial use is more as it is relatively less polluted and pure.
 The information about aquifer such as nature, thickness and characteristics
should be known for betting planning of watersheds.

32. Socio-economic Characteristics
A survey of people living in the watershed should be made regarding their
 needs and wants,
 economic conditions,
 health & hygiene,
 cattle,
 farming practices and
 participation
in watershed management.
Demographic profile, sociological stratification, attitude and behavior of community
will affect the watershed management to a great extent.

33. Benchmark Survey
Benchmark Survey of a watershed is the survey of basic resources. It is essential for
a master plan and future evaluation and monitoring of the watershed.
The basic points considered in Benchmark Survey are as follows:
 Physiography (Name, Elevation, Boundaries, Transportation etc.)
 Climate (Temperature, Wind, Humidity etc.)
 Soil (Type, Depth, Permeability etc.)
 Hydrological Survey (Rainfall, Infiltration, Evaporation, Evapotranspiration)
 Topographical Survey (Size, Slope, Shape etc.)
 Land Use and Vegetation Survey
 Socio-economic Survey

34. Reference
Watershed Management
by
Madan Mohan Das
Mimi Das Saikia
PHI Learning Private Limited