Contaminated storm water runoff can have many adverse effects on plants, fish, animals and people:
Sediment can cloud the water and make it difficult or impossible for aquatic plants to grow. It also can destroy aquatic habitat.
Bacteria and other pathogens can wash into swimming areas and create health hazards.
Excess nutrients can cause algae blooms. When algae die, they sink to the bottom and decompose in a process that removes oxygen from the water. This is a major problem because fish and other aquatic organisms can't exist in water with low dissolved oxygen levels.
Household hazardous wastes like insecticides, pesticides, paint, solvents, grease, used motor oil and other auto fluids can poison aquatic life. Land animals and people can become sick or die from eating diseased fish or ingesting polluted water.
Debris - plastic bags, 6-pack rings, bottles and cigarette butts - washed into creeks and water bodies can choke, suffocate, or disable aquatic life like ducks, fish, turtles and birds.
Contaminated storm water often affects drinking water sources, this, in turn, can affect human health and increase drinking water treatment costs.