Wherever there is building, sediment is typically found in streams nearby. When there is a high amount of sediment in water, fish gills can become clogged, and the amount of light, which can penetrate through the water decreases. Bacteria - Septic systems, which leak, can cause an increase in bacteria, resulting in disease. Hydrocarbons - Hydrocarbons come from leaking crankcase oils and other car lubricants. We've all seen the rainbow sheen that appears in puddles along the side of a road - these are caused by hydrocarbons.
Hydrocarbons can be toxic to aquatic organisms.
Also they accumulate in the tissue of fish that we eat. When they enter the food chain, they become a threat to humans. Animal Waste - Manure runoff from livestock is a major contributor. Soil Erosion - Soil erosion can occur either by improper irrigation practices, stream channel modification, stream bank vegetation loss, poor livestock management or wind. Fertilizers and Pesticides - These seep into the surface and groundwater.