Aquatic plants thrive on phosphorus and can grow or spread to levels harmful to desirable fish populations. Large algae blooms result from high levels of phosphorus in surface water. Sediment is the largest pollutant by volume of Midwest surface waters. Soil eroded from fields settles in ditches, streams and other surface waters. A build-up of sediment requires dredging to clear the waterway.
Sediment increases the turbidity, or cloudiness, of water.
Turbidity reduces light penetration, which impairs photosynthesis, alters oxygen levels and reduces the food supply for certain aquatic organisms. Sediment can cover spawning beds, destroying fish populations. Sedimentation slowly fills in lakes and reservoirs, reducing their water holding capacity. Pesticides - Herbicides are the type of pesticide most frequently detected in water supplies. Herbicides control weeds on over 90 percent of Indiana's cropland.