San Luis Reservoir levels slowly on the rise, improvements in local water quality

Earlier this summer, the water district encountered a string of challenges that originated from our imported water resources and highlighted the need to work with state and federal governments to improve water management and secure water supply reliability.

Imported water, which accounts for nearly half of our county’s water supply, is part of an intricate water management system. Actions hundreds of miles away can have a profound effect on our local water resources, eventually trickling down to our tap water and groundwater basins.

Our imported water supplies are stored in state and federally managed reservoirs throughout the state and also in the Delta, the hub of California’s water supply system. A high tide and increased salinity in the Delta earlier this summer compromised the quality of water, so officials restricted pumping water from the Delta until conditions improved. There were also reduced water releases from the state’s largest reservoir, Lake Shasta, to protect Chinook salmon.

With these limitations, the water district had to rely on San Luis Reservoir for most of our imported water deliveries – but storage in that reservoir was dropping fast. Normally, water levels in San Luis start to drop steadily in April, after the state and federal agencies have announced water allocations for the year and prepare to deliver water supplies. However, last winter, fishery agencies restricted the amount of water pumped into San Luis to protect fish in the Delta. This resulted in historically low levels in San Luis Reservoir which produced algal bloom that caused the water to have an earthy, musty taste and odor.


San Luis experienced historically low levels in 2015-2016 compared to the driest period on record – Department of Water Resources

To address these issues, the water district began drawing water from Anderson and Coyote reservoirs to minimize the use of San Luis water at our treatment plants and diminish the taste and odor issue. However, drawing down on our local reservoirs resulted in water levels too low to continue the launching of boats at Anderson and Coyote. It also meant that we could not continue replenishing our percolation ponds with water from these reservoirs, and so for a few weeks some of our local pond systems throughout the county went dry.

Two months after the peak period of obstacles, we are glad to report that our trying conditions are improving. Among other efforts, officials are releasing water from Shasta which has allowed for the pumping of water into San Luis Reservoir, and improved water levels and water quality, since the middle of August.

Since Aug. 25, the water district has been able to utilize water from San Luis without blending with local reservoir water, and our local taste and odor issues have significantly reduced.  Once we were able slow our draw from local reservoirs to supply our water treatment plants, the expected early close of boating season at Anderson Reservoir was extended by two weeks. Luckily, our local reservoirs had received a healthy amount of water from last winter’s El Niño storms.

The recent complications, including the inaccessibility of water in the Delta and the concerns for endangered fish species, prove the need to address our water management challenges and secure water supply reliability. Threatened by aging levees, climate change and rising seas, and the possibility of earthquake damage, not only is the Delta ecosystem at stake, but also the reliability of the water transported to us by the State Water Project and federal Central Valley Project.

Currently, the state has asserted that the California Water Fix project will improve the transfer of water across the state while reducing environmental threats to fish. Santa Clara Valley Water District continues to study the proposal and assess its costs and benefits.

On a separate track, the U.S. Bureau of Reclamation is working on a draft Feasibility Study (FS) and an Environmental Impact Study/Report (EIS/R) for the San Luis Low Improvement Project. The purpose of the study is to evaluate alternatives for improving water management in San Luis Reservoir. Possible alternatives include increasing storage by expanding the reservoir, or extending the intake that sends water to Santa Clara and San Benito counties. There will be a public draft FS and EIS/R available for the public to review by approximately February 2017.

Besides stabilizing our imported water resources, the water district understands the need to diversify water supply resources. Expanding our regional water supply through potential partnerships  would mean less dependency on the Delta, and more options in trying times.

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