Water quality - how healthy lakes, streams and rivers are, and what exactly is polluting them. Within the United States, many state agencies and local partners work to monitor the quality of water in lakes and streams. They measure for pollutants, make sure drinking water is clean, and work to restore what is dirty. One of the. major sources of water pollution? Agricultural runoff and animal agriculture. But it also comes from stormwater and wastewater. Because everything we do on the land, eventually is reflected in the water.