Two Gates Review Panel Report and Response Released

The CALFED Science Program coordinated an independent review panel in August to review the 2-Gates Fish Protection Demonstration Project-an experimental project where two temporary, removable gates would be placed in the central Delta in an effort to protect sensitive fish species and manage the water supply. The panel’s role was to evaluate the proposal’s scientific strengths and weaknesses as an experiment in reducing delta smelt entrainment.

The review report and a response from the project proponent, the Metropolitan Water District of Southern California, are now posted. The review panel is complimentary about several aspects of the project, saying the proposed fish protection project is “a rare opportunity to conduct a large-scale adaptive management experiment and could provide flexibility in operations.”

The review panel also voiced several concerns including necessary improvements to the delta smelt behavioral model and the need to gather field data to test the fundamental hypothesis driving the project, the response of delta smelt to high turbidities. Initial research suggests that the pre-spawning migration of smelt is tied to the amount of sediment and suspended particles in the water (turbidity).

The panel makes six overall recommendations (see sidebar) and several precautionary steps to take if the decision is made to proceed with the project-including considering an alternative location of the gates.

“In their response, the project proponents note that the design and optimal operation of the 2-Gates Project for the adult phase of delta smelt are based on the best available understanding of cues that influence pre-spawning migration behavior in winter and spring,” said CALFED Lead Scientist Cliff Dahm in his acknowledgment of the response to the independent science review. “Refining our understanding of the link between turbidity and upstream migration behavior of adult delta smelt is a critical scientific need. Ideally, this information will be a high priority science study that begins this winter and assists project design and operation.”


“Refining our understanding of the link between turbidity and upstream migration behavior of adult delta smelt is a critical scientific need.”

--Cliff Dahm, CALFED Lead Scientist


“We [the CALFED Science Program] stand ready to provide staff expertise, peer-review, or organize topical workshops regarding the science supporting the project,” Dahm said.

Environmental documents are currently being drafted by the Bureau of Reclamation. For more information, see