New Report on Nitrate in California Ground Water

One in ten people living in California’s most productive agricultural areas is at risk of exposure to harmful levels of nitrate contamination in their drinking water, according to a report released recently by the University of California at Davis. The report was commissioned by the California State Water Resources Control Board. The report, “Addressing Nitrate in California’s Drinking Water,” is the first comprehensive scientific investigation of nitrate contamination in the Tulare Lake Basin, which includes Fresno and Bakersfield, and the Salinas Valley. It defines the extent of the problem, suggests promising solutions and outlines possible funding mechanisms.

In their new report, UC Davis scientists examine data from wastewater treatment plants, septic systems, parks, lawns, golf courses and farms. The report concludes that more than 90 percent of human-generated nitrate contamination of groundwater in these basins is from agricultural activity. Much of that excess is only now beginning to affect water quality in the Tulare Lake Basin and Monterey County portion of the Salinas Valley. Today’s discharges will continue to contaminate drinking water decades from now, the report says. Fixes for drinking water systems in these basins could cost about $20 million to $35 million per year for decades, the report concluded. As nitrates continue to spread, drinking water system costs could increase for Tulare Lake Basin and Salinas Valley communities. Key findings include:

  • Drinking water supply actions, such as water treatment and finding alternative water supplies, are most cost-effective. However, well supplies will become less available as nitrate pollution continues to spread.
  • While many options exist to provide safe drinking water, there is no single or ideal solution for every community affected.
  • Agricultural fertilizers and animal manure applied to cropland are the two largest regional sources of nitrate leached to groundwater — representing more than 90 percent of the total.
  • Reducing nitrate in the groundwater is possible, with methods such as improved fertilizer management and water treatment. Costs range from modest to quite expensive.
  • Directly removing nitrate from large groundwater basins is extremely costly and not technically feasible.

For the full UC Davis report, videos, maps, and more information, visit the report’s website.