San Leandro Creek has suffered the same fate as many urban creeks in the last century — with the onslaught of development and its natural channels manipulated, it began to function ecologically much differently than in the past.
Today, the most pristine portion of the creek is in its upper reaches, near the unincorporated community of Canyon, which is nestled between Oakland and Moraga. There the creek channels are natural and experience a limited urban influence.
But when researchers from CSU East Bay sampled water from that area last year, they found evidence of fecal pollution that sometimes exceeded state guidelines.
The creek, a protected watershed, flows from the eastern slope of the hills near Oakland's Huckleberry Botanic Regional Preserve. It runs southeast through Canyon before joining Upper San Leandro Reservoir and then Lake Chabot, two bodies of water owned by the East Bay Municipal Utility District (EBMUD).
It then flows west through San Leandro and on into San Leandro Bay at Arrowhead Marsh, just north of Oakland International Airport.
The study on the health of upper San Leandro Creek was conducted by CSU East Bay biologist Dr. Stephanie Molloy and graduate student Kathy Seiber.
Between October 2009 and May 2010 they sampled water 10 times, five during rain conditions and five when there had been no precipitation for at least 24 hours. Bacteria indicating the presence of fecal matter were found in all samples. The bacteria levels were higher after rain events, and highest overall upstream of Canyon.
For the sampling events last September and October, the team found levels of E. coli and Enterococcus, both bacteria that live in human intestines, exceeded maximum guidelines for recreational fresh water established by the California Department of Public Health.
The findings could be due to environmental runoff from less forested land cover, the researchers postulate. Other studies have shown that fecal indicator bacteria levels in creeks and streams are affected by land use, with urban and agricultural areas having higher numbers than forested land, Molloy said.
A genetic marker for ruminant fecal bacteria was not detected in any samples. (Ruminants include cattle, goats, sheep and deer, among other animals.)
The researchers also suspect the pollution is partly caused by runoff from septic systems near Canyon, Molloy said, although they couldn't prove their hypothesis because they weren't allowed to test that water, she said.
Bert Mulchaey, an EBMUD fisheries and wildlife biologist who works extensively in the creek watershed near Canyon, said that although he hadn't read the study, he also suspected septic systems could be the source of the contamination. The water district has in the past found similar issues with fecal pollution in the area, he said.
EBMUD’s master plan, adopted in 1996, says of the watersheds near San Pablo and Upper San Leandro reservoirs: “Runoff samples have extremely high amounts of fecal bacteria, as is typical of developed watersheds.”
Mulchaey participated in a forum last month on the health of San Leandro Creek sponsored by Friends of San Leandro Creek. About 20 residents and high school students attended the meeting, held Feb. 19 at the .
At the forum, Mulchaey said biologists with the agency test water quality in the watershed primarily by conducting fish and bug sampling. Though fish species are struggling in other, more urban areas along the creek, they are actually thriving in its upper regions, Mulchaey said. That includes native species like rainbow trout.
“But it’s definitely an issue of public health,” he said of the study showing high fecal bacteria in the creek.
Friends of San Leandro Creek also tests water quality monthly at a site near Lake Chabot. Laurey Hemenway, watershed awareness coordinator for the group, said she tests pH, oxygen and nitrate levels, temperature, depth and turbidity (how clear the water is).
Hemenway said the results usually show acceptable water quality, although there have been exceptions, as in February when she tested the water and found the pH and dissolved oxygen levels were abnormally high.
According to Mulchaey, the area from the Chabot dam to I-580 is pretty much the only viable habitat for fish species in lower San Leandro Creek, and that may be because the water in the lake itself does not come from local sources.
About 90 percent of the water in the agency's reservoirs, including Lake Chabot, is piped in from the Mokelumne River, which is fed pure water from melted snow in the Sierra Nevada mountains.
"San Leandro Creek obviously has significant problems with pollution. Most Bay Area creeks are in the same boat," Mulchaey said."Most of the damage was done a long time ago."
Biologists with EBMUD are focusing their energy on areas of local creeks that are more natural, which have a greater chance of reestablishing native ecosystems.
But while Mulchaey said the situation looked bleak for the creek as a whole, if government and the public do their part to manage its health, "hopefully we can improve the habitat and range of these fish species."
In the early 1990s, the Oakland Museum of California published a report on East Bay creeks. Included is a written guide to a tour of San Leandro Creek.