What is a Watershed?
A watershed is an area of land where all of the rain and snow in it drains to the same water body, like a stream, river, pond, lake, or ocean. Watersheds are named after the water body they drain into. When water flows across the land it can pick up pollutants and carry them to a water body. We all live in a watershed that feeds a local water body which might be used as a drinking water source or for recreational or commercial activities. Watershed management often involves multiple communities working together on mutual land use policies and reducing polluted runoff to improve water quality.
The Water Cycle
The water cycle is the process of water moving due to gravity and heat between the atmosphere, glaciers and snow, water bodies, plants, animals, and land. During the water cycle, water changes between solid, liquid, and gas form, for example, changing from a liquid (lake water) to a gas (water vapor) when evaporation occurs. 97% of the Earth’s water is salt water, with the remaining 3% freshwater being divided up into frozen water (snow, glaciers, and ice sheets) (2%), groundwater (0.8%), and surface water (permafrost, lakes, ponds, rivers, streams, and freshwater wetlands) (0.2%).
Urban Impaired Streams
A stream is considered impaired if it fails to meet water quality standards because of effects of stormwater runoff from developed land.
Additional stormwater treatment controls are necessary in urban watersheds of impaired streams because proposed stormwater sources in urban and urbanizing areas contribute to the further degradation of stream water quality. Urban impaired streams are listed in Appendix B of this rule and include all streams where violations of water quality classification standards have been documented for which urban stormwater has been identified as a significant cause. Urban impaired streams are considered “degraded, sensitive or threatened regions or watersheds” as described in 38 M.R.S. §420-D(4).
