Big benefits from fences on Olema Creek


A study published this month by the Point Reyes National Seashore and the University of California’s Marin cooperative extension shows that fecal coliform levels in the Olema Creek watershed have dropped by 95 percent over the last 19 years—the result of local ranches implementing new best management practices around streams.

The initiative, which the seashore facilitated in collaboration with ranchers, conservation organizations and regulatory agencies, began in 1999 and included three main types of best practices: fencing, hardened stream crossings and the creation of separate water systems for cattle.

The estimated cost of implementation—much of which ranchers completed themselves—was roughly $870,000, with funding provided by the United States Department of Agriculture, the San Francisco Bay Regional Water Quality Control Board, the Environmental Protection Agency, and state Fish and Wildlife, among other agencies. 

“The data shows us that we can use grazing livestock agriculture as part of our food system, and we can also reach environmental goals—watershed quality, in this case—within the working landscape,” said David Lewis, one of the authors of the recently published paper who specializes in watershed management for the cooperative extension. “Agriculture can be a partner in the solution; in fact, it is one of the key partners.”

Although the conservation work in the Olema Creek watershed is part of a larger, ongoing effort supported by groups such as the Marin Resource Conservation District and others along all the tributaries that feed Tomales Bay, the study analyzes the specific effect of 40 practices along Olema Creek. 

Within that watershed, the seashore manages 9,000 acres of what the study describes as “mixed annual grassland and oak savanna and woodland ecological sites.” Half of those 9,000 acres are leased to cattle ranching operations for grazing.

To monitor the success of best management practices, park biologists collected stream water samples at five permanent sites on grazing lands alongside Olema Creek where the best management practices were implemented from 1999 to 2017. Biologists also sampled one non-grazed, perennial tributary of Olema Creek to serve as a control.

Samples were taken quarterly between 1999 and 2003 and monthly between 2004 and 2017 during summer low-flow seasons; biologists drew storm runoff samples during the winter rainfall season most years. The monitoring looked for bacteria—in this case, E. coli—that indicate the presence of fecal material and pathogens in water.  

The study explains that cattle in stream corridors can increase microbial pollutants not only by directly depositing fecal material, but also by disturbing microbial pollutants in stream sediments and damaging riparian vegetation and soils, which provide natural filtration.

The data showed a 95 percent reduction in average fecal coliform concentrations at the grazed sites. The study determines there was a “concurrent, significant trend of reduced fecal coliform concentrations over the course of the 19-year grazing [best management practices] implementation campaign.”

During a presentation of the report to the Tomales Bay Watershed Council last Friday, the seashore’s range program manager, Dylan Voeller, answered several challenges posed about the study, including about the reduction of coliform levels over time relative to large storm events.

Mr. Voeller said that large precipitation events over the course of the study were fairly comparable, signifying that the decrease in coliform levels was not due to lower water levels. In 2006, biologists recorded 1,421 millimeters of water column in the creek, compared to 1,309 millimeters in 2011 and 1,420 millimeters in 2017.

The authors state that their study, by taking a bird’s eye view, has unique relevance for the scientific and agricultural communities. “Real-world [best management practice] implementation and associated monitoring campaigns—such as the one reported in this paper—often suffer from challenges, including insufficient pre- and post-implementation data and not having identical treatment and control watersheds,” they write. “Thus, it is often difficult to demonstrate, beyond all reasonable doubt, that grazing [best management practice] implementation strategies result in quantifiable water quality improvements.”

They continue, “Our results indicate that in a sustained watershed scale effort, specifically designed to protect public health from livestock grazing activities, managers in Olema Creek were successful in achieving substantial reductions in fecal coliform concentrations via [best management practice] implementation.”

Mr. Lewis underscored the uniqueness of the study. “We have the science to show us the benefit of each practice—such as, let’s say, the repair of an erosion feature—on that smaller scale, but it is not often done to try to look at the larger, long-term, watershed scale,” he said. 

Mr. Voeller gave the ranchers a lot of the credit. “Ranchers participated in the development and implementation of projects in numerous ways, working with the [National Park Service] and various partners—including [the U.S.D.A. and the Marin R.C.D.]—applying for funding and assistance, going out and looking at sites and contributing their working knowledge of the lands to come up with feasible and effective improvements,” he wrote in an email. “All in all, it has been a collaborative effort with ranchers being key participants.”

One caveat the study makes is that the first phase of the effort—which began in 1999 and lasted until 2006—may have been the most effective.

Although the data showed a continued reduction in coliform levels over the 19 years, the greatest reduction was observed in the first seven years, when cattle were fenced out of 90 percent of the main stem of Olema Creek.

At the data sites, the mean coliform level until 2006 was 1,906 MN/100mL (a common water quality metric that means the most probable number of viable cells in 100 milliliters of water). Between 2007 and 2017, the mean levels dropped down to 291 MN/100mL. 

The analysis of that data yielded that the “initial prioritization and implementation of [best management practices] was associated with a mean reduction of fecal coliform by 1,615 cfu/100ml—an 85 percent mean reduction that persisted throughout the remainder of the study period,” the study states.

This suggests, it continues, a “disproportionately large return on investment," considering the beginning phase cost $125,000, compared to practices implemented in the latter half of the project, which cost $745,000. 

Monitoring water quality at the six sites in the watershed will continue, Mr. Voeller emphasized. That work is also just one piece of the whole, considering that Olema Creek is one of three main tributaries of Tomales Bay, where efforts from a host of regulatory agencies and conservation groups have strengthened since the regional water quality control board put the bay on its list of impaired water bodies in 2007.

In 2014, the water board and the Tomales Bay Watershed Council combined resources and now collaborate on a single water-quality monitoring program for the watershed, with help from the park service and the Inverness Public Utility District. The water board collects samples at around 30 stations on a monthly basis, and each year those stations are monitored weekly for five weeks during both wet and dry seasons.

The impaired listing for Tomales Bay opened up funding streams for a variety of projects to address the impairment, including for the creation of the community wastewater system in Marshall.