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Whoa on the Delta Exports DWR

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The California Department of Water Resources (DWR) and the US Bureau of Reclamation (USBR) recently raised south Delta exports from 800 cfs (12/15) to 6,700 cfs (12/29). Delta outflow of freshwater has declined from 27,000 cfs (12/25) to 5,300 cfs (12/29) in just four days. Though these conditions are allowed in Delta standards, the standards must be changed.

Under these conditions, with the Delta Cross Channel gates closed (per standards), water is pulled from the central and west Delta toward the south Delta export pumps (Figure 1). The problem is that remnants of the Delta smelt population have moved into the west and central Delta on their annual winter spawning migration, as shown in early warning surveys at Jersey Point (Figure 2). Negative net flows (Figures 3-6) draw fish to the pumps and disrupt the salinity field and Low Salinity Zone. Exports also continue to take brackish water (Figure 7) – not good for fish, crops, or humans. They also take juvenile salmon emigrating through the Delta (Figure 8).

Map of Delta Flows Dec 2015

Figure 1. Delta net flow patterns in late December 2015 – positive (blue arrow) and negative (red arrows).

Graph of False River Flows

Figure 3. False River (middle left red arrow in Figure 1) net flows have turned negative with lower Delta outflow and higher exports.

Graph of Three Mile Slough flows

Figure 4. Three Mile Slough (top left red arrow in Figure 1) net flows have turned sharply negative with higher exports.

Graph of Jersey Point flows

Figure 5. Jersey Point (left end of middle left arrow in Figure 1) net flows have turned negative with higher exports.

Graph of Old and Middle River Flows


Figure 6. Net flow in Old and Middle Rivers in south Delta (large lower right arrow in Figure 1) has turned sharply negative with higher exports.

Graph of EC at Clifton Court

Figure 7. Salinity levels (EC) in Clifton Court Forebay in December 2015.

Graph of Chinook and Exports

Figure 8. Salvage of Chinook salmon and export rate at Clifton Court Forebay in December 2015. Many of these salmon are likely endangered Winter Run and Spring Run.