4.1.10.E+pd.2

Human Events on Watersheds
Man-made surfaces such as parking lots, roofs, and roads are impervious to water. When precipitation falls on these surfaces, the water does not become ground water but instead becomes surface runoff. Because less water becomes groundwater, more water enters streams or rivers as runoff or through a a storm drain system. Water that enters a watershed through a storm drain system usually carries a variety of contaminants such as phosphorus, nitrogen, toxic metals, herbicides and pesticides from agriculture, other organic material, and bacteria. Oil compounds from roadways and and animal waste from lawns also enters the storm drain system.

Water that enters a watershed as surface area and travels over surfaces that are impervious to water cause the water to travel at a high velocity. The high velocity of the water causes greater erosion. The swift moving water also carries a lot of sediments that muddies the rivers and streams and also carries bacteria. Both cause water treatment to be more extensive. More sediments in the water also affect aquatic plants because less sunlight reaches the plants (Chesapeake Bay Foundation 2008).

Human Events on Wetlands
When humans first settled North Americia, they thought that wetlands were useless wastes of land. As a result, many wetlands were drained or converted to some other uses. Some have been destroyed by the daming of rovers. Humans have done many things to affect the ecosystems of wetlands including adding pollution to wetlands and introducing non-native species that compete for the resources that native species need.Wetlands have also been used for logging.

http://streaming.discoveryeducation.com/search/assetDetail.cfm?guidAssetID=CABC5FC5-6605-41A7-B47D-54931D28E0DB&rand=A9AC30B3-1560-AC16- [|46C8DC105979F379]
 * Video**

Water: A User's Guide. Environmental Media (2001). Retrieved May 2, 2008, from unitedstreaming: http://streaming.discoveryeducation.com/

4.1 Watersheds pd2