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Lake Shasta and Sacramento River Operations: Lessons Learned – #1, Part 1

Following an introductory post, this is the first post in a series on the lessons learned by the National Marine Fisheries Service (NMFS) from the 2013-2015 drought that devastated Sacramento River salmon populations.  This post addresses Lesson #1 and how it was not applied in 2020.Water and fisheries managers have known for many years that both the Lake Shasta storage level on April 1 and spring releases from Shasta determine how much cold water will be available in the lower Sacramento River through the summer. The Central Valley Project’s (CVP) decades-old state-water-right permits require that the Project maintain cold-water releases through the summer and fall. The Bureau of Reclamation’s CVP water managers know that their contractors need to make planting decisions in the spring based on available and allocated water supply. Finally, CVP water managers know that water temperature management is necessary in the spring as a condition of water right permits and state water quality standards.

The cold-water storage in Lake Shasta going into the April-September irrigation season is in part a consequence of carryover storage from the previous September and of winter reservoir inflows and releases. After April 1, new inflows from spring rainfall and snowmelt, and outflows from irrigation releases, further change the amount of cold-water storage available for salmon into the fall. Spring releases are varyingly limited in drier, low-storage years, depending on the willingness of irrigators to defer planting and of CVP managers to limit allocations. In past drought years, some contractors have voluntarily delayed spring planting to save cold-water storage.

Based on the low supply of cold water on March 1, 2021 (Figure 1), management must be conservative and reactive to changing conditions. In March 2020, the cold-water pool was relatively high (Figure 2) after wet year 2019. In March 2021, the cold-water pool (Figure 3) is slightly less than it was in March 2020, a below normal water year.

Controversy surrounded Reclamation’s 2020 Temperature Management Plan (TMP; draft presented April 23, 2020; final presented May 20, 2020). The State Water Resources Control Board (State Board) refused to accept and objected to final TMP in a June 1, 2020 letter. Reclamation’s release pattern in spring 2020, when compared to prior years, clearly showed that Reclamation did not heed the “lesson learned:” 2020 Shasta Reservoir releases in spring were actually significantly higher than normal (Figure 4).

Reclamation never resolved the issues that the State Board raised in its June 1, 2020 letter. The State Board largely dropped the immediate issues, since it was too late to improve the cold-water pool after the high spring releases from Shasta. How developments between Reclamation and the State Board over the summer of 2020 affect decision making in the spring of 2021 will be the subject of the next post.

In the summer and fall of 2020, the State Board apparently decided to look forward to 2021. However, there has been no apparent positive movement toward better decision making for 2021 either. The lesson learned has not changed: temperature management plans need to be finalized in early April.

Here we are at the beginning of March in 2021, a drier than normal water year to date. Reclamation has allocated the Sacramento River Settlement (SRS) contractors 75% of their normal supply.1 Reclamation has not released even a preliminary Sacramento River Temperature Management Plan. How much water will Reclamation release from Shasta in April and May? What will likely happen this summer and fall? Will the Bureau of Reclamation under the Biden Administration cooperate with the State Board and issue an early TMP? Will the State Board enforce its requirements, or will it once again back down?

Stay tuned.

Figure 1. Cold-water pool storage in Shasta Reservoir on the Sacramento River as of March 1, 2021, along with patterns in recent years and long-term average. Of note is that the 2021 level is only slightly above that of critical drought years 2014 and 2015, whose limited supply by fall led to very poor survival of winter-run salmon.

Figure 2. Shasta Lake temperature profile and configuration of Temperature Control Device (TCD) release points in March 2020.

Figure 3. Shasta Lake temperature profile and configuration of Temperature Control Device (TCD) release points in March 2021.

Figure 4. Shasta/Keswick dam releases to the upper Sacramento River in spring of five examples of drier than normal years. Note the higher releases in below-normal water year 2020.