City to study Gibraltar Reservoir capacity

ERIC LINDBERG
DAILY SOUND STAFF WRITER

Santa Barbara city leaders said they are keeping a close eye on water supply issues as they discussed and approved a study of debris buildup in Gibraltar Reservoir at Tuesday's City Council meeting.
"I know there is a lot of concern about the effect of the Zaca Fire on siltation in the Gibraltar Reservoir," Councilmember Iya Falcone said. "...We are on top of it. We are paying attention to it."

Cathy Taylor, the city's water system manager, said heavy rains will likely intensify the siltation effect due to the impacts of the Zaca Fire, which scorched 60 percent of the watershed. Erosional rates could be 40 times greater than normal and could fill half of the current capacity with sediment, she said.
"This is a real concern for us, because Gibraltar is currently at half its normal capacity," Taylor said.
Santa Barbara receives about 35 percent of its water from Gibraltar Reservoir. Even if that supply was diverted to Lake Cachuma, Taylor said a bottleneck would occur at the South Coast Conduit, which serves Goleta, Santa Barbara, Montecito and Carpinteria.
That pipeline has a maximum conveyance of 43 million gallons per day, typically below the supply needed for the South Coast. During Labor Day weekend, the local communities used nearly 50 million gallons a day, she said.
"If we had five hot days in a row, we'd have a problem," Taylor said. "...We'd have water rationing at that point."
Mitigating the effects of the unstable watershed is a balancing act between protecting the water supply and protecting the environment, since those areas are all critical habitats for endangered species. Taylor has been discussing potential solutions with the U.S. Forest Service and local environmental groups, such as Los Padres ForestWatch and the Environmental Defense Center.
Among the options being discussed is installing debris racks in creek beds to catch logs, rocks and other large objects. Taylor also said a peninsula created by sediment at the inlet of the Santa Ynez River could be dug out, which would have not only a positive impact on capacity, but water quality as well.
With a large-scale fire like the Zaca Fire, ash, sediment and resin from burned vegetation mixes to create what Taylor termed "gooey gunk," which would slow down the water flow.
"We need to keep that out of the water system," she said. "It would just wreak havoc with everything."
By digging out the peninsula, the "gunk" could be trapped in settling pools at the inlet of the river.
Since the land is owned by the federal government, Taylor is hoping to get recommended projects added to the BAER (Burned Area Emergency Recovery) report completed by federal officials for the Zaca Fire. With support from the government, Taylor said they will be freed up to move forward with mitigation efforts.
The bathymetric study approved unanimously by the Council will determine how much additional silt has been deposited in the reservoir since the last study and how much capacity remains. Mapping of the lake floor last occurred in 2004, and Taylor said the study will help staff as they develop ways to limit the flow of debris into the reservoir.
"We are working to come forward with the best solution to address our water quality and water capacity issues with the least amount of impact on the environment," Taylor told the Council.
Councilmember Roger Horton said if those solutions involve spending city funds, the Council needs to know about it soon.
"If we don't figure out a way to solve it, we will be spending a lot of capital money to build new dams or raise our current dams," he said.
City Administrator Jim Armstrong said the Council will receive a water supply report next month. In the meantime, Taylor said she will continue to work with U.S. Forest Service officials and environmental groups to analyze potential projects that will reduce silt deposits in the reservoir and await the results of the bathymetric study, which is expected to be complete by December.