Watersheds are the locations where water flows on its way to a common body such a stream, river, lake, or aquifer. These natural systems range in size from small ponds to the Nile River Basin, which is almost 7000 kilometers long.
Watershed management begins with knowing how water moves within it and calculating the full range of the natural and human elements that influence this movement as well as the amounts of water that the watershed can offer.
Watersheds are frequently “managed” by people in an unintentional manner. Roads, parking lots, and other paved surfaces enhance runoff volume and peak flow while also shortening runoff duration. Plant and tree removal can increase erosion and increase runoff water quantities.
Many watershed management programs focus on protecting the quantity and quality of source waters. Preserving topsoil and vegetation helps to prevent erosion and other water loss events and provides natural water purification. Terraced farming, common in South-east Asia, is one example of how watershed management has been used for many centuries to reduce water losses and to stop erosion.
Catchment basins, dam structures, and other diversionary architecture are used in water harvesting activities to collect precipitation and runoff and store it for later use. More water may be able to return underground and refill groundwater supplies as a result of water storage, either naturally or through regulated artificial recharge methods.
Watershed managers can use these efforts to reduce seasonal rainfall variations.
Some watershed management strategies may focus on influencing human behavior. Watershed managers can impose land use plans and zoning priorities through incentives and prohibitions to ensure minimal negative impacts on the natural watershed cycle—or to boost that cycle in order to maximize available drinking water resources.
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