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What is a Watershed?
What is the Watercycle?
Why do homes and land development create pollution?
How Can Nonpoint Source Pollution Be Controlled?
A watershed is the area of land from which runoff (from rain snow and springs) drains to a stream, river, lake or other body water. Its boundaries can be identified by locating the highest points of land around the waterbody. Streams and rivers function as the "arteries" of the watershed. They drain water from the land as they flow from higher to lower elevations.
The water cycle is the movement of water through the environment (top graphic). It is through this movement that water in river system is replenished. When precipitation falls to earth a natural (undeveloped) watershed, 40 percent will be return( to the atmosphere by evaporation or transpiration (loss of water vapor by plants). About 50 percent will percolate into the soil (middle graphic). The remaining 10 percent of the precipitate moves across the land as runoff and drains into streams, wetlands and other bodies of water.
The water that soaks into the ground is important for maintaining stream flow during dry weather. Percolating water slowly moves downward through the soil until it drains into an area where all the pores and cracks in the rock are saturated with water, The top of this zone is known as the water table.
Water in this saturated zone moves laterally, following the la of gravity and/or water pressure from above. If the path of the moving ground water intercepts a stream channel, the ground water is discharged into the stream as a spring. This discharge defined as its base flow. At times when there is no surface runoff, the entire flow of a stream might be base flow from ground water.
Developed land is more impervious than natural land. Rain hits the hard surfaces of buildings, pavement and compacted ground and runs off into a storm drain instead of percolating into the ground (bottom graphic). These man-made structures are designed to move water quickly away from developed areas and into a natural watercourse.
This practice drastically changes the fate of precipitation in the water cycle:
The most obvious way to prevent nonpoint source pollution from entering a creek is to have new development retain storm water runoff on-site. This is one recommendation of the Davis Creek Watershed Plan. Another recommendation is that developed lands .should capture the first one-half inch of rainfall. The first runoff from a rain storm can be highly polluted because it contains the accumulated pollutants washed from roads and parking lots.
Simple common sense, good housekeeping and wise choices are also critically important for preventing surface water damage from storm water related nonpoint source pollution. Rain can leach pollutants onto the ground whenever trash bins are left uncovered. Other controllable sources of pollution include: excessive use of lawn fertilizers and pesticides, leaves and limbs placed near a drain, grass clippings dumped into streams, dumpster spillage, people hosing dirt or paint waste into the street, and oil and fuel spillage from poorly maintained vehicles.
Davis Creek Watershed
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