Nitrate nitrogen is a nutrient that supports the growth of algae and aquatic plants, which provide food and habitat for fish, shellfish and smaller organisms that live in water. Too much of this nutrient in the water causes algae to grow faster than ecosystems can handle. Significant increases in algae harm water quality, food resources and habitats, and decrease the oxygen that fish and other aquatic life need to survive. Sources of nitrate include agriculture, stormwater, treated wastewater, fossil fuels and home products such as fertilizers, detergents and pet waste.

Nitrate nitrogen concentrations which were compared against the Los Angeles Region Water Quality Control Plan (Basin Plan) standard of 10 mg/L.

1. Exceeds Basin Plan, > 10 mg / L
2. Below Basin Plan, ≤ 10 mg / L

On the map on your left explore the proportion of water samples that exceeded regulatory standards for each region of the San Gabriel watershed for Nitrate Nitrogen.