A nice spurt of Delta inflow and outflow occurred during mid-March 2020 (Figure 1). In past dry winters, this would have been a life saver for many juvenile salmon and smelt in the Delta. But this March brought no miracles for Delta fish. Without new rules for the State Water Project (SWP), the Project’s Banks pumping plant in the south Delta maxed out exports (Figure 2), just like the SWP did after last December’s storms.1 March exports have been just below the maximum export-to-inflow (E/I) ratio allowed by the State Water Board (35%). From 2009 through 2019, the state’s incidental take permit (ITP)2 limited exports by restricting negative flows in Old River and Middle River (OMR restrictions) to protect the state-listed longfin smelt and Delta smelt. Not so in the winter of 2020.
Longfin smelt need more protection. See Figures 3-7. In the past, March 2020 conditions would have been termed high risk by the Smelt Working Group. But the Smelt Working Group disappeared while the new federal Biological Opinions for Delta operations were making their entrance in late 2019. Although managers often ignored the recommendations of the Smelt Working Group, there was at least some outside technical documentation and accountability.
Meanwhile, the state’s soon-to-be-released new ITP looks like it will divert the discussions that the Smelt Working Group used to have to an in-house colloquy between the Department of Water Resources and the Department of Fish and Wildlife. The ITP also has provisions to allow more negative OMR’s and thus higher levels of exports during storm events. This will make fish in the Delta more dependent on miracles even as miracles become harder to come by.
Figure 1. March 2020 calculated Delta outflow. Source: CDWR.
Figure 2. March 2020 Delta exports. TRP = Federal Tracy Plant. HRO = state Harvey Banks Plant.
Figure 3. Early March 2020 Larval Survey for Longfin Smelt. Yellow denotes X2 location. Blue arrow denotes positive downstream Sacramento River channel flow. Red arrows denote interior Delta net flow direction. Pattern indicates risk to Longfin Smelt.
Figure 4. Mid March 2020 CDFW Larval Survey – partial survey results for longfin smelt.
Figure 5. Mid March 2020 CDFW 20-MM Survey – partial survey results for longfin smelt.
Figure 6. March 2020 Old and Middle River combined daily average flows in Central Delta. Source: USBR.
Figure 7. March 2020 tidally-filtered flows at three Delta locations that represent net Delta outflow. Note mid-March outflow (sum of three) was negative for several days. Source: USGS.