Much of California’s surface drinking water and irrigation supplies are either derived from rangeland runoff, or are stored in reservoirs situated within the State’s 40 million acres of rangeland watershed. 

Microbial water quality standards are based upon indicator bacteria – fecal coliform or Escherichia coli. It is assumed that these bacteria can “indicate” the presence of pathogens, and associated human health risks. Pathogens of concern in rangeland streams include Cryptosporidium parvum, Salmonella, Campylobacter and Escherichia coli O157:H7.

There is substantial concern that pollution from livestock on rangelands degrades water quality, threatening human and environmental health. For the past 25 years, the Rangeland Watershed Program (RWP)—a diverse partnership of rangeland stakeholders—has developed and implemented an integrated research, education, and planning program to proactively address this concern.

This brief summarizes an analysis of Water Quality impairments in California for which livestock grazing has been identified as one possible source of impairment. The data for this analysis was sourced from the 2012 California State Water Resources Control Board Integrated Report (Clean Water Act Section 303(d) List / 305(b) Report). 

Stream temperature is an important water quality attribute in many of California’s streams, especially those that support cold-water fisheries such as trout, steelhead, and salmon. Several fish have been identified as threatened or endangered, and elevation of summer stream temperatures is often cited as a cause.

Prescribed grazing and fire are among the most cost effective vegetation management tools available to most rangeland managers, however, the watershed-scale impacts of prescribed grazing and fire on water quality, hydrology, and nutrient cycling are the subject of intense debate.