Environmental stewardship on California dairies

A dairy is a nutrient factory. Feed comes in, much of it grown on the dairy's own fields; milk goes out; and the manure in between has to be stored, moved and returned to the land without harming the water underneath or the air around it. This page maps the main environmental questions California dairies deal with and points to our guides on each.

Groundwater: the central issue in the Central Valley

Most of California's dairies are in the Central Valley, where cropland and corrals lie above aquifers used for drinking water. Nitrate leaching from manured fields and, to a lesser degree, seepage from ponds and corrals are the main concerns. Since 2007 the Central Valley Regional Water Quality Control Board has regulated existing dairies through a General Order, reissued in 2013 as Order R5-2013-0122. In September 2026 the State Water Resources Control Board remanded that order and set a new framework for nitrogen discharges, with milestones over five years.

Nutrient planning and record-keeping

Each dairy under the General Order keeps a waste management plan for its production area and a certified nutrient management plan for its fields, samples manure, water, soil and crops, and reports each year by 1 July. The quality of those records determines how well a dairy can show that its applications match what its crops remove.

Surface water and storm water

Discharges of manure and wastewater from production areas to surface water are prohibited, and production areas must contain storm water. Ponds need freeboard going into the wet season, fields need management that keeps tailwater and runoff on the property, and anything that does leave must be monitored and, in some cases, reported within 24 hours.

Air quality and greenhouse gases

Dairies also emit ammonia, volatile organic compounds from feed and silage, dust and methane. In the San Joaquin Valley, which has some of the country's most polluted air, large dairies are subject to rules of the San Joaquin Valley Air Pollution Control District. At state level, Senate Bill 1383 (2016) set a goal of reducing methane emissions from livestock manure management by up to 40 percent below 2013 levels by 2030, and the California Department of Food and Agriculture funds methane reduction projects through its Dairy Digester Research and Development Program and its Alternative Manure Management Program. Digesters capture methane from manure ponds to produce energy; alternative practices, such as converting flush systems to scrape systems and drying or composting manure, keep manure out of anaerobic ponds altogether.

A note on certification and education programmes

Since the late 1990s, California dairy producers have been able to take part in voluntary education and certification programmes run as partnerships between the dairy industry, the University of California and state and federal agencies, covering environmental stewardship, food safety and animal care. These programmes are independent of this publication. Milkshed Ledger does not certify farms or offer courses; our guides are a reading companion to the public rules and research.

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