Soil, water, and Vegetation are vital natural resources for the existence of any living organism. These three resources are interdepend and one cannot be managed without proper management of the other two.
The literal meaning of watershed is ‘ Divide line’ that separates one drainage basin from another. In India and china watershed denotes the Drainage basin and catchment area.
Simply, a Watershed can be defined as a unit of area which covers all the land and contributes to runoff through common point.
The phrases “watershed,” “catchment,” “drainage area,” “river basin,” and “drainage basin” are all used synonymously. But generally, small streams and rivers are referred to as watersheds, while larger river systems with several sub-watersheds or sub-catchments nestled within them are referred to as drainage basins or river basins.
Characteristics of Watershed
Each individual watershed has several characteristics that affect the functioning of the watershed, its management, and manipulation.
Physiographic Factors
Size
The size of the watershed has a direct relationship with the quantity of precipitation received i.e larger the area more the precipitation is retained and disposed off.
Shape
The shape of the watershed varies with the geography and other features forming either square, rectangular, Triangular, or any shape. Variation in shape influences the length to width ratio which determines the manner in which water is disposed off.
Longer the watershed, the higher the time of concentration allowing more time for infiltrating, evaporating, or utilization by vegetation.
2. Topography and Geology of watershed Factors
Slope
Length, degree, and uniformity of slope affect the disposal of water and soil loss by influencing the time of concentration and infiltration opportunities.
Drainage
Drainage density, length, width, depth of main and subsidiary channels, main outlet and its size depends on the topography.
3. Geology of rock and soil
The rock and soil types present in the area influence the erodibility of the channel and hill faces. Igneous rocks like quartz, feldspar, etc, and clayey soil are hard and do not erode easily while shales, phyllites as well as sandy gravel soil erode easily.
4. Land use characteristics
The watershed area is the complex area of different types of land use practices that can be
- Forest: Influences the infiltration, retention of runoff, rainfall interception, and sediment of the Watershed area.
- Shrubs: Scattered vegetation which creates runoff retention, and reduces sun exposure to the soil of the watershed area.
- Pastureland: Grassland which attracts the livestock influences the physiology of the area through soil compaction reducing infiltration while also holding soil.
- Upland and Lowland agriculture: Temporary vegetation, induces soil erosion if done on very steep slopes.
- Settlements: Mostly deteriorates the watershed areas.
- Others like ponds, lakes, reservoirs, etc.
5. Land capability
It refers to the land classification according to its suitability. This is done following the FAO Guidelines.
6. Socioeconomic Characteristics
Land use of watersheds is hugely controlled by the socioeconomic characteristics of the residence area. Socioeconomic characteristics comprise:
- Demography: Size, structure, and composition of the community
- Literacy: Awareness status
- Socio-cultural aspects: Social, cultural, religious belief
- Land ownership: Landholding size
- Economic aspect: Income generating source, dependency
- Peoples need: Willingness, demand, and supply
- Institutional aspect: Legislations, incentives, and local institutions
Being the Interdisciplinary sector, Watershed management should incorporate the integrated approach. Integrated watershed management (IWM) is the process of developing and implementing a plan of action involving the manipulation of natural, agricultural, and human resources in a watershed to achieve resource objectives while taking into account the social, economic, and institutional factors operating within a river basin or other relevant region.
