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Research proves lack of water impacts from grazing

by Wyoming Livestock Roundup

Sheridan – “Despite all efforts, there is still quite a bit of controversy about grazing and water in California,” says Leslie Roche, a University of California, Davis (UC Davis) researcher. 

Roche adds that grazing on BLM and Forest Service lands across the West is important for ranchers, saying, “California and Wyoming have seen the biggest drops in animal unit months in terms of destocking from 2000-13.”

She describes newspaper articles that have been published in the Sacramento Bee over the last several years implicating livestock in water quality issues. The news articles stimulated concern in the public and the need for increased research related to cattle impacts on water quality. 

“A collaboration between the U.S. Forest Service (USFS) Region Five, UC Davis, Extension, permittees, regional water quality boards, the state and other range stakeholders was stimulated,” she describes. 

The group met and determined that a research project should first, quantify fecal indicator bacteria and nutrient concentration in surface waters and then compare those levels to regulatory benchmarks set. 

Finally, they hoped to look at the relationships between clean water quality, environmental conditions, cattle grazing and recreational areas.

“The big question is, is public lands cattle grazing degrading environmental quality? And is it putting human health at risk?” she asks. “This is a very serious question.”

Water study

“We conducted a study that is, to date, the most comprehensive, largest water quality survey in the state, and possibly in the nation,” Roche notes. “It included 12 USFS grazing allotments across five national forests, covering 320,000 acres.”

Across the allotments, 155 stream collection sample sites were established and monitored monthly during the active grazing and recreation season – typically June through November – in 2011. 

“The sites we looked at were key grazing areas – areas where cattle were known to graze and congregate – and recreation areas, where people camp and swim. We also looked at areas with no concentrated use activity.”

The team collected 743 water samples, analyzing them for fecal indicator bacteria, fecal coliforms, E. coli and a suite of nutrients.

Comparisons to benchmarks

The water samples were then compared to regulatory benchmarks, which vary across the state of California, depending on the water quality board with oversight of the area. 

“Standards ranged from 20 to 200 colony forming units (CFU) per milliliter of sample for fecal coliforms and 190 to 235 CFU for E. coli,” Roche says. 

For fecal coliforms, only 10 percent of samples exceeded the standards, and less than six percent of samples exceeded E. coli standards, regardless of site type. 

“For nutrients, the majority of samples are below what our minimum detection limits allow,” she mentions. 

Sampling conditions

Roche notes that samples were also collected across a wide array of conditions and in a variety of stream types. 

“We also had the people taking samples record if they were sampling in low flows, turbid waters, next to a cow grazing, where people are swimming and other environmental conditions,” she says. 

“What we found – and not surprisingly – is that in conditions where there are low stream flows and turbid waters, fecal coliforms and E. coli are greater, as well as when cattle were present,” Roche continues. “Where turbidity was present, we were still meeting the standards.”

She urges people to keep in mind that, despite the higher levels seen, benchmarks are still being met, with 90 percent of their total sample volume below the recommended criteria levels. 


“When we look site-by-site, consistently what we find is that recreation areas tend to be cleaner, higher quality waters,” Roche says. “This is a positive story. People are smart and finding good water to recreate in.”

Observed nutrient concentrations were at least an order of magnitude below levels of ecological concern in all water sampling, she continues, and water quality benchmarks were broadly met. 

“Really, our conclusion is that results don’t support concern of widespread microbial or water quality pollution across grazed landscapes,” Roche summarizes. “We keep finding this over and over in other surveys, as well.”

Roche presented at the 2014 Wyoming Association of Conservation Districts Annual Meeting, held Nov. 18-20 in Sheridan. 

Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at

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