Nitrates are a common water pollutant most often associated with agricultural effluent and excess fertilizer. It is a common issue in many locations. One in 10 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 today by the University of California, 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, which includes Salinas and areas near Monterey.
Nutrients from human activities tend to travel from land to either surface or ground water. Nitrates in particular are removed through storm drains, sewage pipes, and other forms of surface runoff. Nutrient losses in runoff and leachate are often associated with agriculture. Modern agriculture often involves the application of nutrients onto fields in order to maximize production. However, farmers frequently apply more nutrients than are taken up by crops or pastures.
"Cleaning up nitrate in groundwater is a complex problem with no single solution," said Jay Lund, director of the UC Davis Center for Watershed Sciences and a report co-author.
Nitrogen in organic and synthetic fertilizers has dramatically increased crop production in California in recent decades. However, excess nitrate in groundwater from surface nitrogen use has been linked to thyroid illnesses, some cancers and reproductive problems.
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.
The nitrate study area includes four of the nation’s five counties with the largest agricultural production, representing 40 percent of California’s irrigated cropland and more than half of the state’s confined animal farming industry.
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.
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. The following treatment method(s) have proven to be effective for removing nitrate to below 10 mg/L or 10 ppm: ion exchange, reverse osmosis, electrodialysis.
The UC Davis report outlines several potential funding solutions, including a fee on nitrogen fertilizer use to help fund drinking water costs.
The report found that 10 percent of the 2.6 million people in the Tulare Lake Basin and Salinas Valley rely on groundwater that may exceed the nitrate standard of 45 milligrams per liter set by the California Department of Public Health for public water systems. The problem is likely to worsen for decades, as nitrogen applied to today’s crops slowly makes its way into groundwater as nitrate.
Communities often respond to initial contamination by drilling a new well or shifting to cleaner water sources. But as high nitrate concentrations continue to persist, communities are faced with using expensive treatment and alternatives.
Key findings included:
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.
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.
For further information and photo: http://www.news.ucdavis.edu/search/news_detail.lasso?id=10164