Abstract
Circulation in Clifton Court Forebay (CCF) was simulated using the three-dimensional (3–D) hydrodynamic model UnTRIM. These numerical simulations were performed to provide a better understanding of circulation patterns, flow pathways, and residence time in Clifton Court Forebay in support of ongoing studies of pre-screen loss and fish facility efficiency for delta smelt (Hypomesus transpacificus) at the California State Water Project (SWP) export facilities. The 3–D hydrodynamic model of CCF was validated through comparisons to observed water surface elevations inside CCF, and comparisons to observed drifter paths and velocity measurements collected by the U.S. Geological Survey as part of this study. Flow measurements collected near the radial gates for 2 days during relatively low inflows suggest that the Hills (1988) gate equations may over-estimate inflow by as much as 39% when the CCF radial gates are only partially opened. Several alternative approaches to improve the implementation of the radial gate flows in the UnTRIM model were evaluated. The resulting model accurately predicts water surface elevations and currents inside CCF over a range of wind and operating conditions. The validated model was used to predict residence time and other transport time scales for two 21-day simulation periods, one of very low daily SWP export pumping averaging 19.3 m3 s-1 and one for moderate daily SWP export pumping averaging 66.6 m3 s-1. The average transit time, indicating the time from entering CCF to reaching the fish facility, was estimated as 9.1 days for low export conditions and 4.3 days for moderate export conditions. These transport time scale estimates may be used to inform estimates of pre-screen losses inside CCF due to predation or other causes.
Highlights
Clifton Court Forebay (CCF) is a regulating reservoir in the southern Sacramento–San Joaquin Delta which is used to improve operations of the California State Water Project (SWP) Harvey O
The Banks Pumping Plant has a daily export capacity of about 15.7 million m3 (12,700 ac-ft), continuous operation is limited by the water level in CCF, and the highest pumping rates typically occur during periods of off-peak power demand (Kano 1990)
Flow measurements collected near the radial gates for 2 days during relatively low inflows (Figure 4) suggest that the Hills (1988) gate equations are not accurate under these conditions
Summary
Clifton Court Forebay (CCF) is a regulating reservoir in the southern Sacramento–San Joaquin Delta (south Delta) which is used to improve operations of the California State Water Project (SWP) Harvey O. The radial gates are generally operated to allow inflows into CCF during high water and to minimize effects on south Delta water levels during low tides. The Banks Pumping Plant has a daily export capacity of about 15.7 million m3 (12,700 ac-ft), continuous operation is limited by the water level in CCF, and the highest pumping rates typically occur during periods of off-peak power demand (Kano 1990). Skinner Delta Fish Protective Facility (SFPF), and the Banks Pumping Plant
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