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Shasta Reservoir Operations, April 2021 Recap – A Bad Start to an Awful Year

April 2021 is a month for the record books. Central Valley Project (CVP) operations of the Shasta-Trinity Division were beyond the pale. Water year 2021 began as a critical drought year after a dry year, with everyone scrambling to save the winter-run salmon in the Sacramento River below Shasta and provide water for downstream CVP contractors. The two opposing goals have proven impossible to meet. With no approved operations plan, the US Bureau of Reclamation (Reclamation) moved ahead to fulfill its water contractor needs at the expense of the federally-and state-listed endangered winter-run salmon, other fisheries, and carryover storage for 2022.

Water releases in April to the Sacramento River below Shasta were significantly higher in 2021 than in the most recent critical drought years 2014 and 2015 (Figure 1). With these higher releases, Shasta storage, which began ahead of 2014, ended up lower than 2014 (Figure 2). As a consequence, Shasta’s cold-water pool has also fallen behind what it was in both 2014 and 2015 (Figure 3). In both 2014 and 2015, releases of warm water from Lake Shasta led to extremely high spring-summer egg mortality, devastating the winter-run spawning year cohort. In both years, the cold-water pool in Shasta simply gave out before the end of summer.

In 2021, water temperatures in the Sacramento River below Shasta have already risen well above the safe level (Figure 4) as Reclamation began releasing warm surface water from Shasta in mid-April to meet contractor demands.1 Reclamation seems to accept sacrificing endangered salmon again in 2021. There has been little mention of the similar fate this year for green and white sturgeon, and for spring-run and fall-run salmon.

Figure 1. Daily average flows (cubic feet per second) in Sacramento River below Shasta Reservoir in April 2014, 2015, and 2021.

Figure 2. Daily average storage (acre-feet) in Shasta Reservoir in April 2014, 2015, and 2021.

Figure 3. Daily average cold-water-pool (<52ºF) volume in Shasta Reservoir in 2014, 2015, 2021 (black line), and other selected years.

Figure 4. Daily average water temperature in Sacramento River below Shasta in April-May period of 2014, 2015, 2020, and 2021. Red line represents safe target daily average water temperature (53ºF) for winter-run salmon egg incubation.