Wednesday, November 6, 2013

Watershed management

Watershed management:
Watershed is defined as the geographic area from which water in a particular stream, lake or estuary originates.It includes entire area of land that drains into the water body. It is supported from other systems by high points in the area such as hills or slopes.
Ex: Watershed of a lake would not only include the streams entering the lake but also the land that drains those streams and eventually the lake.
Watershed management is a process aimed at protecting and restoring the habitat and water resources of a watershed, incorporating the needs of multiple stakeholders.

Impacts of human beings on a watershed:
The activities of human beings have the following impacts on a watershed:
  1. Altering water course: The water course is altered by changing the contour of the land and adding storm water systems
  2. Adding pollution sources: The type of pollutant absorbed and carried by the storm water depends on the land use. During the course of storm water impounded in a parking area might pick-up litter, road salt, motor oil and carry these pollutants to a local stream. In agricultural fields, the rainwater might wash fertilizers and soil into a stream. Melting of snow might wash fertilizers and pesticides into the lawn of suburban homes.
  3. Urbanization: Urbanization has impacted local resources in more ways than one can imagine. It has resulted in a change in the flow and constituents of water flowing into a watershed. Urbanization has changed both the surface and ground water. Urban areas have replaced trees, plants and shrubs with impervious surfaces like roads, roof tops, parking lots and other hard surfaces. These impervious surfaces prevent water to seep into the ground thereby increasing surface runoff. This leads to increased flooding after storms and reduced flow in streams and rivers during dry seasons.
  4. Scouring of channels: Erosion of stream banks and scouring of channels occurs due to increase in volume. Sediment in eroded stream banks clogs the gills of fish and light needed by aquatic plants. Sediment settles in stream channels, lakes and reservoirs thereby increasing flooding and requiring  dredging to clear streams or lakes for boating.
Goals of watershed management:
The two main goals of watershed management are listed below:
  1. Watershed management seeks to preserve the environment and
  2.  Watershed management is applied to make the most cost-effective methods to achieve the above listed goal
Controlling storm water flow
It is essential to control storm-water flow in order to reduce the impact of development of local watershed and aquifers. Storm-water flow can be controlled in both quality and quantity by minimizing the disturbances developed in the natural flow of water. By designing in alignment with nature, the impact of urbanization can be greatly reduced. Storm-water flow can be controlled in the following ways:
  1. Minimizing development of impervious surfaces
  2. Maximizing areas of dense vegetation
  3. Use of structural storm water management basins
  4. Reducing the possibility of pollution of storm-water

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