Pacheco Reservoir Expansion: storing water, saving fish

When listing the pros and cons of building a new dam, you would hardly expect that “environmental benefits” would fall on the “pro” side. Yet, that’s exactly what we anticipate for the proposed expansion of the Pacheco Reservoir. While it may seem counterintuitive, an expanded Pacheco Reservoir east of Gilroy is projected to benefit fish downstream.

We asked Dr. Jerry Smith, an emeritus professor of biology at San Jose State University, to explain how this particular reservoir could help improve conditions for fish. Dr. Smith points out that the expanded reservoir would help support a steelhead population in Pacheco Creek below the new reservoir site. The creek above the reservoir is too dry to support steelhead, so there’s not enough water in most years to support a steelhead population. Imported water would be stored in the expanded reservoir, creating a reserve of cool water to release every year, even during severe droughts. This reliable water source will allow steelhead to migrate and spawn in the Pacheco Creek and Pajaro River system.

In fact, a more robust year-round water flow in Pacheco Creek will provide more than 10 miles of habitat for threatened steelhead enabling protection from drought events. The resulting delivery of cooler water is expected to elevate the survival of steelhead eggs and fry in Pacheco Creek, helping ensure the long-term survival of this cold-water fish.

An expanded Pacheco Reservoir would reduce the frequency and severity of water shortages, provide flood protection for disadvantaged communities, as well as protect and grow the native steelhead population. This cooperative project will help our wildlife flourish and sustain our water supply to aid and benefit our community and those who share this environment with us.


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