Representative Groundwater Monitoring on California’s Central Valley Dairies

We devised a pioneering, industry-wide monitoring well network in response to the Regional Water Quality Control Board’s Dairy General Order (R5-2007-0035). The Dairy General Order was the Regional Board’s first effort to address agricultural non-point source contamination of groundwater and required the installation of monitoring wells on all ~1,370 regulated dairies.

Our new approach generates information representative of the entire industry on a subset of only 42 dairies from a network of 443 monitoring wells. It takes advantage of key similarities between dairies and site conditions while fully accounting for substantive differences. The representative nature and functionality of the network were vetted by two expert advisory committees.

The results are impactful. A key program summary report found that approximately 94 percent of nitrate losses to groundwater are linked to fields where dairy forage crops are grown. A critical step toward achieving farm-scale manure nitrogen balance will be to increase exports of manure from some dairies to other farms, where it can be used to build healthier soils when used in proper amounts. The report recommends specific improved protocols and robust diagnostics to create more accurate inventories of manure nitrogen and other nutrients.

Significant Project Elements

• Saved the dairy community on the order of $50 million in the first few years of implementation
• Groundbreaking design of monitoring wells for site-specific impact analysis of non-point source contaminants such as nitrate and salinity
• Installation of hundreds of monitoring wells under intense regulatory pressure in a matter of weeks
• Briefings of the Governor’s Office, CalEPA, State Water Resources Control Board, and California Department of Food and Agriculture
• Effective engagement with regulatory agency and stakeholder groups
• Convened and organized two expert advisory committees
• Highly effective: Comprehensive dataset produced insightful results in the first year of the program