Pollutants like oil and pesticides that are dumped on the soil will eventually be carried into rivulets, streams and rivers. Contaminants carried by water can be concentrated in the fish and other organisms. Contaminants can also be deposited in mud at the bottom of lakes and rivers. Some of the contaminants alter the kinds of organisms that live in the water. Changes in water quality and the aquatic communities ultimately affect our use and enjoyment of our natural water resources.
Humans are part of every watershed.
We live on watersheds and play in water. We use water for drinking, food production, power generation and industrial activity and we make all kinds of waste that is put back into the water. Some of our waste products are put on the soil. Some wastes are deposited in landfills and others are flushed down our sinks and toilets. All of these wastes are moved by water and transported down to streams and rivers.