Ranchers, environmentalists and policy makers unite to protect water quality on California rangeland
(Adapted from UC Davis Magazine Online)
Volume 29 Number 4 (Summer 2012)
By Diane Nelson
Grazing and water quality?
Over half of California’s 57 million acres of rangeland is privately owned and managed for livestock production – and that holds big implications for the food we eat and the water we drink. Some 80 percent of the state’s irrigation and drinking water passes through or is stored on rangeland. All the water and all those animals raise a serious concern:
Can microbial pollutants in cow manure be transferred to the water that runs off these ranges, tainting the food we eat and the water we drink?
The short answer: Yes, but it takes a herculean effort for a bad bug to survive the journey from cow to human, and there are ways to manage cattle to make the journey highly improbable. Rangelands, in fact, provide some of the state’s healthiest watersheds.
That short answer was a long time in the making, a journey that continues to this day. UC Davis researchers and UC Cooperative Extension specialists have been central to the process, helping turn foes into friends committed to a common goal — protecting rangelands in order to meet society’s need for open space, habitat for plants and wildlife, and healthy watersheds delivering clean water for us all.
A thirsty state
People don’t like the thought of cow manure near their drinking water. “In the late 1980s, grazing was being blamed – wrongly in many cases – for any number of environmental and wildlife conservation issues,” says Mel George, UC Cooperative Extension Rangeland Specialist Emeritus. “So we knew it was important to get out in front of grazing and water-quality issues. We wanted to know, what was the risk of pathogens in water runoff from rangeland? Where there ways to mitigate it?”
In the early 1990s, George helped spearhead the UCCE Rangeland Watershed Program, which used education and applied research to answer those questions and more. Collaborating with local water districts, the U.S. Environmental Protection Agency, and several state and federal natural resources agencies and associations, the rangeland watershed team went to work.
The program really started making headway in 1995, with the birth of a new research partnership. Rangeland hydrologist Ken Tate joined UC Davis as a UCCE Rangeland Watershed Specialist. He joined forces with Rob Atwill, a newly hired UCCE Specialist at the School of Veterinary Medicine and an expert on waterborne infectious diseases. Their teams conducted groundbreaking experiments with “waterborne zoonotic pathogens,” bugs that are shed by animals, transmitted by water and can make people sick. Some common culprits include Cryptosporidium parvum, Giardia, E. coli and Salmonella.
“Their science helped us find that balance, helped us make smart land-use decisions.” Tim Koopmann, a watershed resource specialist with the San Francisco Public Utilities Commission.
It takes a toolbox
Conditions vary from ranch to ranch – soil, slope, climate, vegetation, etc. – so when it comes to rangeland watershed management, one strategy does not fit all.
“Our goal is to build a tool box, a range of methods to reduce the risk of microbial pollutants,” says Tate. “We don’t tell ranchers and regulators what tools to use. We identify what works and what doesn’t work, so they can design a water-quality and grazing management plan that’s feasible and sustainable.”
The biggest threat to human health from cow manure is from the youngest in the herd – most pathogens found in cows live within calves less than 4 months old. (Ten percent of adult cows shed Cryptosporidium but only 0.5 percent of them shed a strain that is infectious to humans. And most Giardia shed by cows of any age is not infectious to humans.) Accordingly, early fall or spring calving is better than winter calving. Strategic fencing can help keep livestock away from running water, as well as providing water and feed in spots away from creeks.
Pathogens in cow dung die quickly in warm weather, thanks to solar radiation. And even in cold, wet weather, pathogens tend to stay trapped in the fecal pat. By timing grazing in critical watershed areas to occur during spring, summer or early fall, all Cryptosporidium can be inactivated before winter rainfall and runoff occurs.
Take care of your rangelands and riparian areas, and they will take care of you. Researchers say that well-vegetated hill slopes, riparian areas and buffers function as kidneys, trapping and holding pathogens. “For each additional yard pathogens have to travel through vegetation, there is another 30-99.99 percent reduction in potential transfer of pathogens from fecal pat to stream or lake,” Tate says.
There’s no silver bullet, and management can’t reduce the risk to zero. But when ranchers keep cows from loafing near running water, give pastures a rest before irrigation, care for the buffers and protect their soils, they minimize the threat. Even during the wettest winter, rangeland runoff is generally safer than runoff from urban areas, with its full suite of pollutants like gasoline, garbage, motor oil, heavy metals, fertilizers and pesticides.
Building on the common ground established over that past 20 years, this team of stakeholders is working today to establish the California Grazing Water Quality Partnership as a forum to ensure collaborative, proactive grazing land water quality protection for the next 20 years.