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  California Water Science Center

Assess the Preliminary Finding That There Are Increased Fall Salinities in the Western Sacramento-San Joaquin Delta

In the last several years (2002-2004), abundance indices calculated by the Interagency Ecological Program (IEP) have been at record lows for delta smelt Hypomesus transpacificus and age-0 striped bass Morone saxatilis and near-record lows for longfin smelt Spirinchus thaleichthys and threadfin shad Dorosoma petenense. While several of these declining species have shown evidence of long-term declines, there appears to have been a precipitous “step-change” to very low abundance by at least 2002-2004 even though flow conditions were moderate. Similar flow conditions have supported modest production of these species in the past. These changes are particularly important to managers because the delta smelt is a federal and state endangered species.

As part of the POD research, Contra Costa Water District identified increases in fall salinity as measured by the Bureau of Reclamation at Jersey Point. A further investigation of this preliminary finding is necessary to understand possible underlying mechanisms for this rise in salinity. Furthermore, two USGS flow and water quality monitoring stations are located in the South Delta and these funds will be used to support these stations for three months. Increasing salinity is important because it affects the water quality of Contra Costa Water District drinking water exports. Salinity is also important in understanding the distribution of an invasive clam Corbula amurensis, which can reduce the forage base for fishes by consuming phytoplankton and zooplankton.

Project Chief: Cathy Ruhl - No longer with the USGS

For more information contact:
David Schoellhamer
Phone: 916-278-3000
Email: dschoell@usgs.gov

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