What are the main sources of pollution affecting California's water quality?

The selection highlights the primary sources responsible for water pollution in California, which significantly impact the state's water quality. Agricultural runoff, urban runoff, and industrial discharges are well-recognized contributors to pollution in many regions, including California.

Agricultural runoff consists of fertilizers, pesticides, and other chemicals that wash off from farms into nearby waterways, leading to nutrient loading and triggering eutrophication, which can harm aquatic ecosystems. Urban runoff encompasses stormwater collecting pollutants from city landscapes—such as oil, heavy metals, and other contaminants—that eventually flow into rivers, lakes, and oceans. Industrial discharges from factories and manufacturing facilities can introduce hazardous substances directly into water bodies, affecting both environmental health and human safety.

Understanding these sources is crucial for developing appropriate policies and practices aimed at improving water quality and managing resources effectively. Other options may include contributors to water pollution, but they do not encompass the leading sources recognized in California's context as effectively as agricultural runoff, urban runoff, and industrial discharges do.