With poor salmon runs from 2009 to 2011, Reclamation provided good conditions in the lower Sacramento River below Shasta Reservoir in spring-summers of 2010 to 2012 for fall-run and winter-run salmon. That effort contributed to recovery of fall-run salmon from the 2007-2009 drought in 2012-2014 (Figure 1). The sequence of below-normal, wet, and below-normal water years (2010-2012) provided sufficient water for good smolt survival, overcoming a significant deficit of adult spawners (eggs spawned). Poor conditions in the subsequent drought of 2013-2015 led to the latest fall-run collapse in 2016-2017.1
So did Reclamation provide good spring-summer conditions in the lower Sacramento River in below-normal, wet, below-normal water year sequence 2016-2018 to help recovery from the latest drought? No. As a result, we can now expect poor runs in 2019 and 2020 instead of a recovery.
Reclamation made a concerted effort in 2010-2012 to meet water temperature objectives in the upper river near Red Bluff (Bend, Balls Ferry, and Red Bluff) and the lower river near Sacramento (Wilkins Slough, Verona). The 56°F and 68°F water temperature objectives for the upper and lower river, respectively, were regularly met (Figures 2-4) in spring and summer.
In a less than concerted effort in 2016-2018, Reclamation has failed to meet the water temperature objectives more often and with greater discrepancies (Figures 5-7). More detail on the failure is provided in a recent post.
Problem and Solution
The causal factor is simply lower flows in spring and summer 2016-2018 than 2010-2012 (Figure 8). Lower flows, higher water temperatures, and lower turbidities lead to poor salmon smolt survival (and low adult migrant survival and subsequent egg viability). A concerted effort to recover salmon would mean maintaining water temperature objectives with spring-summer flows in the lower river at Wilkins Slough in the 7000-8000 cfs range instead of the 5000-6000 cfs range (Figure 8). This may require a supplemental release from Shasta Reservoir as in 2012 (Figure 9), which amounted to nearly 200,000 acre-ft of storage release, so that storage ended at 2,600,000 acre-ft at the end of September. The target end-of-September storage in below-normal water year 2018 is 2,300,000 acre-ft. With water deliveries near 2 million acre-ft from the Sacramento River in 2012 and 2018, a “concerted effort” involving 200 thousand acre-ft to maintain water temperature objectives prescribed in the water right permits seems reasonable. Whether it comes from Shasta storage or water contractor deliveries is a management/permitting agency decision.