An expanded Pacheco Reservoir would benefit threatened South Central California Coast Steelhead

The proposed expansion of Pacheco Reservoir in southern Santa Clara County is not solely a project aimed at improving our region’s ability to store water for droughts and emergencies.

A collaboration between Valley Water, the San Benito County Water District and Pacheco Pass Water District, the proposed expansion will improve the quality of fish habitat downstream of the dam.
Currently, Pacheco Reservoir is not large enough to allow for sufficient releases of water into Pacheco Creek to support the South-Central California Coast Steelhead, a fish population listed as federally threatened.

The South-California Central Coast Steelhead migrate and spawn in watersheds that flow into Monterey Bay and the Pacific Ocean, such as the Pajaro, Salinas, Carmel and Big Sur rivers. The juvenile fish are reared (grow and develop) in freshwater streams before migrating to the ocean to grow and mature, and then return as adults to reproduce in the same freshwater systems where they hatched.

The proposed expansion will increase the reservoir’s capacity from 5,500 acre-feet to up to 140,000 acre-feet. By increasing the reservoir’s capacity, Valley Water and its partners will have the ability to store more of the native water, which can then be used to further enhance habitat for the threatened steelhead.

The larger reservoir will provide water storage and emergency water supply benefits to Santa Clara and San Benito counties. A bigger and deeper reservoir will also create a reserve of more water and cooler water to release into Pacheco Creek throughout the year, providing suitable flow and water temperatures to support the migration and survival of the South-Central California Coast Steelhead.

A more robust year-round water flow in Pacheco Creek will improve approximately 10 miles of habitat that could support threatened steelhead. The resulting delivery of more consistent flows of cooler water is expected to provide migration opportunities, elevate the survival of steelhead eggs and fry, and provide adequate conditions for summer rearing in Pacheco Creek, improving the long-term survival of this cold-water fish.


  1. Will you also provide steelhead hatcheries to mitigate the damage your projects have done? Over the past 6 or 7 decades all of your dam projects, (Uvas, Pacheco, and Chesbro,) are the reason the steelhead are endangered to begin with. Creating a hatchery program would surely help restore the fish populations and also restore your agency’s image in the eyes of many of your many paying customers! I am not sure how you guys actually have gotten away with this for so long but it would be a step in the right direction. While you are at it, put a hatchery program on Coyote creek, Los Gatos Creek, Stevens Creek and all the other fisheries that have been destroyed buy your past negligence, greed, and general lack of environmental stewardship. I understand it is not all your current agency administrations fault but repairing the damage done while creating and enhancing recreational opportunities and restoring the environment al damage is your responsibility now. It would be better for you to do it on your own, rather than through court mandate, I would think. Just my opinion. Please don’t think that the expansion of one of your dams gets you off the hook for all the damage done to our fisheries over the years.


    1. Valley Water strives to balance its water supply, flood protection, and environmental stewardship missions. Information about Valley Water’s efforts to protect and enhance fish habitat is available here


    2. Jacob is correct and I thank him for his well expressed opinion … Valley Water has a long, long way to go in rehabilitating the streams that they have channeled or more often just let them dry up for most of the year … Valley Water has for decades simply ignored any environmental stewardship that they should have embraced … Valley Water has a lot of work to do in order to move towards redeeming themselves for past damage to stream environments …


  2. This is over simplified. What happens to the Steelhead during the 8 years of construction? What guarantee is there that water will actually be released for the fish? Will water rights changes be needed and how will that impact water supply? Will there be water quality problems when poor quality imported water from the Delta is introduced into the system?


    1. Thank you for your thoughtful questions regarding potential environmental impacts of the Pacheco Reservoir Expansion Project. The project team includes expert fisheries biologists and many other water resources specialists who are helping to guide the project design, with regular input from state and federal regulatory authorities. We look forward to engaging with you and with other members of the public directly during the CEQA process.


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