DWR Statement on Fall X2 action

From the Department of Water Resources:

The operators of the State Water Project and Central Valley Project, working with federal and state wildlife protection agencies, have agreed to modify fall flows for endangered Delta smelt fish species.

Throughout September, the water projects have been implementing actions to decrease salinity and increase food availability to support the critically endangered Delta smelt in the Sacramento/San Joaquin Delta.  One of these actions includes increasing delta outflow to decrease salinity in the delta, also referred to as “Fall X2.” The other main action included the Department of Water Resources (DWR) operating gates in the Suisun Marsh to maximize suitable habitat for the endangered fish to improve conditions in areas of the delta where Delta smelt are most likely to exist.

The Fall X2 action is included in the 2019 U.S. Fish and Wildlife Service (USFWS) Biological Opinion and California Department of Fish and Wildlife (CDFW) 2020 Incidental Take Permit to improve low-salinity habitat for Delta smelt during September and October in wet and above normal years. Fall X2 is achieved through a combination of State Water Project and Central Valley Project reservoir releases and reduced exports to move the location of the low-salinity zone downstream of the Delta. The intention of the flow action is to provide Delta smelt habitat in Suisun Bay, where it was hypothesized the fish species would have improved access to food supply and less stressful water temperatures.  The 2019 Biological Opinion provides for adaptive management actions based on changing scientific data.

USFWS modeling indicates that October implementation of “Fall X2” is not a critical driver of Delta smelt survival. Reclamation and DWR will off-ramp from the Fall X2 action in October in consideration of the September voluntary gate action. Analysis concludes that these actions taken together will provide similar or greater protection compared to a September/October outflow action only.  A gate operation in September and off-ramping in October provides conditions to allow scientists to test hypotheses about the efficacy of the Fall X2 action.

Reclamation and the Fish and Wildlife Service conclude that this action will provide similar or better protection for the Delta smelt and could allow for the delivery of as much as 150,000 acre-feet of additional water supply as compared to the alternative of providing Fall X2 flows only, during both September and October.  CDFW has approved a minor amendment to the 2020 Incidental Take Permit submitted by DWR for this action. DWR, which manages the State Water Project, and Reclamation, which manages the Central Valley Project, will continue to work with the state and federal fish agencies to carry out this adaptive management proposal in October.