Agencies Propose Solutions for San Luis Reservoir

What many drivers traveling the Pacheco Pass probably don't realize is that the body of water they see out their car window as they wind their way between the Central Valley and the San Francisco Bay Area is more than just some Insta-worthy scenery.

The San Luis Reservoir is an artificial lake located in Mercer county. Shown here during drought conditions, it provides water to Santa Clara and San Benito counties. Photo courtesy of the Bureau of Reclamationv


Published: May, 2019


What many drivers traveling the Pacheco Pass probably don’t realize is that the body of water they see out their car window as they wind their way between the Central Valley and the San Francisco Bay Area is more than just some Insta-worthy scenery.


The San Luis Reservoir is in fact the state’s fifth largest reservoir and a significant source of water for many nearby communities. The reservoir weathered seven years of drought conditions like a champ. Still, the Bureau of Reclamation and the Department of Water Resources, which jointly own and operate the reservoir, have some ideas for ways to ensure uninterrupted service to end-users in Santa Clara and San Benito counties, including farmers, whenever the reservoir’s water level gets low. The San Luis Low Point Improvement Project Draft Feasibility Report was released last month and outlines the costs, benefits and environmental impacts of four proposed “action alternatives.”


The state pumps water to the reservoir during the wet season from the nearby Delta-Mendota Canal, as well as the California Aqueduct outside Tracy, and water is stored there until summer. When the state extracts water from the reservoir during dryer months and sends it to nearby pumping stations for distribution, warmer temperatures and the lowering water level create conditions that foster algae growth.


When the algae blooms get bad (and they do), the water districts that count on water from the San Luis Reservoir, including the Santa Clara Valley Water District (Valley Water), have two options—treat the water, or find water elsewhere that’s not green.


“None of those are preferred methods to deliver water to customers,” said a Valley Water spokesperson.


The problem with treating the water to kill the algae is that the treatment stinks—literally. And not only does the treated water smell bad, it also doesn’t taste great. But finding another reliable source of water isn’t easy, particularly when water is as scarce a commodity as it was during the epic seven-year drought from which California is only now emerging thanks to recent storms. And if you believe in the reality of climate change, plenty more rainless days are in store for Californians.


One proposed option, the Lower San Felipe Intake Alternative Plan, proposes constructing a new lower intake to keep water flowing to Valley Water in the dryer months. The new intake would be closer to the bottom of the reservoir and allow for water to be extracted even when the level is low—without getting any of the algae that’s sitting closer to the surface.


A second option, the Treatment Alternative Plan, proposes retrofitting Valley Water’s Santa Teresa Water Treatment Plant to include an additional treatment step that uses ozone to kill the algae and disinfect the water. Option three, the San Luis Reservoir Expansion Plan, proposes adding fill material to raise the existing dam’s crest and increase storage capacity.


The last and locally-preferred option, the Pacheco Reservoir Expansion Plan, proposes expanding the reservoir to increase its storage capacity by knocking down the existing dam and building a new one a half-mile upstream. (There actually is one more option, and that’s to do nothing at all. That’s called the “No Action/No Project Alternative.”)


The pro and cons of each option are discussed at length in the report. When asked to pick its favorite, the Bureau of Reclamation responded, “The federal planning process is a non-bias process.”


Valley Water, on the other hand, prefers option four, the Pacheco Reservoir Expansion Plan. During the year-long public selection process that preceded last month’s report with the top four options, Valley Water collected more than 70 letters of support for the Pacheco Reservoir Expansion Plan from business associations, agricultural organizations, labor groups, natural resources groups, elected officials, disadvantaged community advocates, fellow water districts and other municipalities.


“From Valley Water’s perspective, [this option] will not impact the recreational use of the San Luis Reservoir, and will provide the highest benefits in longer drought conditions,” Valley Water said.


If the state chooses this option, Valley Water has $484.55 million in cash to help pay for it. The money was awarded conditionally last summer from funds set aside by the state under the Proposition 1 Water Storage Investment Program, a response to a drought that at the time seemed might never end.


And while the drought is now technically over, the reservoir’s key stakeholders agree that Californians very much need to continue regulating their water consumption. “It is important to conserve water when possible to maximize the benefits of available water to everyone and the environment,” said a Bureau of Reclamation spokesperson. “The demand for water in California continues to grow.”


Valley Water added that water conservation and environmental stewardship continue to be key tenets of the agency’s mission. And truth be told, they’re just happy that Sacramento and Washington are working to address the challenges Valley Water faces delivering clean water to its customers on a consistent basis.


“It is great to see this project move forward with various solutions,” said Valley Water Board Chair Linda J. LeZotte in a written statement.


The general public has until May 6 to weigh in on the report. As of press time, no public comments had been received. The report can be viewed on the Bureau of Reclamation website:

The San Luis Reservoir is California’s fifth largest reservoir. Photo courtesy of the Bureau of Reclamation