Pollution that impacts water quality is divided into point and nonpoint sources. Point source pollution is discharged from a known source, such as a wastewater treatment plant or a factory. Point sources are monitored and regulated to control discharges.

The leading cause of water quality problems is nonpoint source pollution, the accumulation of runoff from city streets, construction sites and agricultural fields, spills and abandoned mines.

By far the leading cause of water quality problems is nonpoint source pollution, the accumulation of runoff from city streets, construction sites and agricultural fields, spills and abandoned mines. Contaminants are picked up by rainfall, snowmelt and urban runoff and carried to creeks, rivers, lakes and even groundwater. Some examples of nonpoint source pollutants include fertilizers, herbicides, oil, grease and sediment.

It was once thought that polluted water would be naturally filtered as it seeped underground, but that is not the case. Many industrial chemicals are highly persistent and do not break down in soil. Consequently, more technologically advanced testing techniques are necessary to detect contamination. The full extent of groundwater contamination is not known, but the number of threats has increased, forcing the closure of thousands of wells.

Nonpoint sources are difficult to regulate because of their diffuse nature and so are dealt with through management measures that stress prevention and cost-effective, low-tech solutions.

Because of the collective impact of multiple pollutants on drinking water supplies, recreation, fisheries and wildlife, officials say the solution to the problem lies in educating people that they all have a part to play in minimizing the amount of pollutants that originate in a watershed. Among other things, this includes carefully following directions when applying lawn fertilizers, curbing pet waste and ensuring motor oil and other harmful chemicals are kept out of storm drains. Information about steps you can take to reduce runoff can be found at this website, http://www.waterboards.ca.gov/nps/index.html