Education For Environmental Responsibility

Water trouble may not be from cattle

It's mostly human bacteria seen in waterways studied

This article appeared in the Modesto Bee on January 9, 2007

By John Holland, Bee Staff Writer

A study commissioned by a farmers group suggests that humans, not livestock, are the main source of certain bacteria entering waterways in the Northern San Joaquin Valley.

The study authors cautioned that the findings are tentative, but if they hold up, they could influence the debate over how farmers manage runoff from irrigated land.

People involved in the study said much of the bacteria detected at the 27 monitoring sites in August could have come from failing septic systems or other sources of human waste, rather than from livestock manure.

"Everyone was kind of thinking thiswas going to be a cow problem, but it's not," said Wayne Zipser, executive manager of the Stanislaus County Farm Bureau.

Zipser is a leader in the East San Joaquin Water Quality Coalition, which commissioned the report. The coalition, representing the east side of the valley from Stanislaus to Madera counties, is one of several formed by Central Valley farmers in an effort to meet tightened rules on runoff.

The study, by three experts at the University of California at Davis, followed up on earlier detection of E.coli, a type of bacteria that can sicken people, at some of the sites monitored by the coalition.

The new study looked not for E.coli, but for bacteria from the genus Bacteroides. These microbes contain DNA specific to their sources — human, livestock or others — and can be a general indicator of how bacteria movethrough a watershed.

At almost all of the sites, human DNA was found far more often than the cattle or chicken versions. At two sites, one near Waterford and one east of Turlock, human and chicken DNA were equal but cattle DNA was a tiny contributor.

"We were surprised it turned out the way it did, the fact that human DNA is so high in almost all the samples,"said lead researcher Michael Johnson, director of the Aquatic Ecosystems Analysis Laboratory at Davis.

Wildlife and pets also can produce bacteria in waterways, but the study authors left them out because of limited funding.

Attorney Brent Newell, a frequent critic of valley agriculture, said the study is of little value because it measured only the relative shares of DNA, not the actual amount of E.coli.

He also said the study dealt only with creeks,irrigation drains and other surface water, not the groundwater many rural residents drink.

"Anybody that tries to make a statement here that agriculture is not a source of E.coli is vastly overstating the conclusions," said Newell, who works for the Center on Race, Poverty and the Environment in San Francisco.

The farmers coalition sends itsdata to the Central Valley Regional Water Quality Control Board, which aims to prevent pollution of the Sacramento and San Joaquin rivers and their many tributaries.

Board spokeswoman Liz Kanter also noted the lack of E.coli data in the study.

"We want to know more — what the scope of the work entailed, how random was the sampling," she said. "It's not conclusive for us."

Second sampling is likely

Coalition chairman Parry Klassen said another round of sampling will likely be done this winter to see if storms have any effect on movement of bacteria.

He said human sources of bacteria could include illegally dumped portable toilets or "vagrants" relieving themselves near the sampling sites.

"It's unlikely that it's sewage treatment plants, because they have to comply with permits," Klassen said.

Kanter said the state is moving to tighten controls on septic systems, which when working properly allow waste to break down harmlessly in soil.

Klassen noted that farmers own many of the septic systems in rural areas. These systems are not under the farm runoff rules, which deal mainly with containing water tainted by pesticides, livestock waste and fertilizers.

Johnson and his co-authors on the study, Lizabeth Bowen and Melissa Turner, stressed that their findings are only a start.

"Clearly," they wrote, "much more research needs to be conducted before we can confidently understand the behavior of bacteria in these systems."

The reporter can be reached at (209) 578-2385 or jholland@modbee.com.

On the Net: http://www.modbee.com/business/story/13179388p-13821920c.html