Abstract
Long-term hydrodynamic and salinity transport modeling of the Sacramento–San Joaquin Delta is needed to evaluate the future Delta in terms of the California co-equal goals of ecosystem health and reliable water supply. While 2-D and 3-D hydrodynamic and water quality models are by definition better suited to modeling a complex network of tidally influenced flows under future conditions, a 1-D model is more computationally efficient in narrowing the large variety of multiple-year simulations required into a more manageable task. Still, a 1-D model of sea level rise in an estuary must account for the three-dimensional effects where increased depths will affect density driven (baroclinic) circulation and tidal dispersion of salt. In this paper, we use a simplified Delta network model with a tidally averaged computational approach to quickly perform multi-year simulations for sea level rise. The 1-D model uses tidal dispersion coefficients developed from 3-D hydrodynamic models. The resulting model is capable of performing very fast simulations over a wide range of conditions, providing guidance on what should be explored in depth with more detailed, but slower models. Comparisons of unimpaired Delta inflow with the historical case show that the south Delta and San Joaquin River would be much fresher without exports, while the Sacramento River would be fresher in spring and more saline in the fall. Sea level rise will increase salinity throughout the Delta over time. With peripheral conveyance of export, water salinity will intrude upstream in the Sacramento River, be slightly lower up the San Joaquin River and increase in the south Delta. With sea level rise, peripheral conveyance will have similar trends to changes to the historical case, but export salinity will be improved by the peripheral conveyance component. A larger peripheral conveyance can benefit both the ecosystem and exports if managed properly.
Highlights
The California Sacramento–San Joaquin Delta (Figure 1) once included over 202,000 hectares (500,000 acres) of sub-tidal, intertidal marsh and seasonal floodplains (Thompson 1957; Whipple et al 2012)
To examine a range of effects for agricultural, urban, and environmental water uses, we focused output on five locations in the Delta (Figure 1): (1) Chipps Island, used to monitor salinity regulations for fish during the spring; (2) Emmaton, where irrigation water standards are in effect; (3) Jersey Point, an irrigation standard; (4) the Contra Costa Water District (CCWD) pumping plant in the southwestern Delta with more stringent urban standards; and (5) Clifton Court Forebay (Clifton CF) in the southern Delta representing water exports for the State Water Project (SWP) and the Central Valley Project (CVP) with year-round urban standards and seasonal irrigation standards
We used Water Analysis Module (WAM) to evaluate some key water quality issues associated with broad export-management alternatives and anticipated changes in the Sacramento–San Joaquin Delta
Summary
The California Sacramento–San Joaquin Delta (Figure 1) once included over 202,000 hectares (500,000 acres) of sub-tidal, intertidal marsh and seasonal floodplains (Thompson 1957; Whipple et al 2012). With peripheral conveyance of export, water salinity will intrude upstream in the Sacramento River, be slightly lower up the San Joaquin River and increase in the south Delta.
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