May Shasta-Trinity Operations Prove Deadly for Salmon

Back on May 3, 2021, I warned about how bad things were getting for salmon in the Sacramento River below Shasta Reservoir, even compared to drought years 2014 and 2015. With high-volume releases from Shasta storage through almost the end of May, conditions went from bad to worse. 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 Central Valley Project (CVP) contractors. The latter objective has won outright.

Water releases to the upper Sacramento River were even higher in May than April (Figure 1). Releases remained significantly higher than either 2014 or 2015. Such high releases sustained water deliveries to the CVP’s Sacramento River Settlement Contractors at high levels despite reduced allocations for a critically dry year with low storage.

Water temperatures were also significantly higher in May (Figure 2), creating lethal conditions (>53ºF) for eggs of winter-run salmon, which typically begin spawning in April. Peak spawning occurs in June and July, with 60-90% of total spawning by the end of July, even with spawning delayed in warmer years.1 Spawning has likely been delayed in 2021 because of the warmer water temperatures. Delayed spawning also has deleterious effects on egg survival and smolt production.2

The high-volume releases have led to lower total Shasta Reservoir storage at the end of May in 2021 compared to 2014 and 2015 (Figure 3). Inflows to the reservoir (not shown) were similar in the three years – averaging for May just above 3000 cubic feet per second (cfs).

Reclamation has sustained the volume of Shasta Reservoir’s cold-water pool through May 2021 at 2014 and 2015 levels (Figure 4), despite the higher releases and lower storage in 2021. Reclamation did that in part by bypassing power plant releases that draw colder water and instead drawing warmer surface water from “river outlets” nearer the top of the dam (Figure 5).

Reclamation has yet to gain approval for summer operations, but the draft Temperature Management Plan (TMP) it submitted to the State Water Board on May 5 proposed Shasta-Keswick releases of 8000-10,000 cfs. Reclamation’s May 5 draft plan also proposed a target temperature of 56ºF for the 10-mile spawning reach of the Sacramento River just downstream of Keswick Reservoir, around Redding. Such temperatures will lead to high egg mortality this summer. Reclamation’s draft plan included significant inputs of warmer water (>53ºF) originating in Trinity Reservoir and exported to the Sacramento River via the Spring Creek Tunnel from Whiskeytown Reservoir to Keswick Reservoir.

The higher Shasta releases and warmer Trinity water, while proving substantial power generation and water supply deliveries, are depleting already-too-low Trinity and Shasta reservoir storage. They also preclude maintaining the safe water temperature of 53ºF that would minimize egg mortality this summer in the Sacramento River’s spawning reach. Lower storage also results in late summer loss of access to the cold-water pool in Shasta Reservoir.

In a May 21, 2021 letter to Reclamation, the State Water Resources Control Board commented on Reclamation’s draft TMP. The State Water Board’s letter suggested maintaining an end-of-September Shasta target storage of 1,250,000 acre-feet, stating that this would represent a “reasonable balance between temperature control this year, maintaining some carryover storage going into next year, and providing for consumptive water supply needs.” The main problem with the State Water Board’s target 1.25 MAF end-of-September storage is that it would still result in >50% (and potentially much higher) salmon egg mortality. The State Water Board’s target does not correct warm Trinity transfers, excessive Shasta and Trinity releases, and low Shasta and Trinity storage. It would also leave no cold water for Sacramento River fall-run salmon in the fall. The low storage levels may even limit access to cold-water pools in the reservoirs.

Eliminating 80-85% of the warm Trinity transfers and reducing cold water releases from Shasta would save a much greater percentage of the fish in the Sacramento and Trinity-Klamath river systems. It could maintain safe 53-55ºF spawning reach temperatures through the summer, while preserving approximately 500,000 acre-ft of Shasta and Trinity storage for next year.

Such an alternative would cut power production and Sacramento Valley water supply deliveries to roughly half of the levels in 2014 and 2015. In this regard it bears remembering that senior water contractors chose not to absorb some of the water cutbacks in 2020, the first year of the latest drought. Now, drastic delivery cuts are necessary to avoid the third disaster for winter-run salmon in seven years.

For more complete discussion, see CSPA’s May 23, 2021 alternate Temperature Management Plan at

Figure 1. Keswick Reservoir water releases (cfs) in April-May 2014, 2015, and 2021

Figure 2. Keswick Reservoir water temperatures (ºF) in April-May 2014, 2015, and 2021.

Figure 3. Shasta Reservoir storage (acre-feet) in April-May 2014, 2015, and 2021.

Figure 4. Shasta Reservoir cold-water-pool volume (1000s of acre-ft) in water years 2014 (red line), 2015 (purple line), and 2021 (black line). Also shown is average (shaded) and two wetter years. Source.

Figure 5. Shasta Reservoir pool configuration and release sources on May 18, 2021. Temperature Control Device (TCD) gate operation is also shown. Note the combination of turquoise from TCD gates and orange from river outlet water sources provided Shasta releases on May 18.

  1. Source.
  2. For further discussion, see E. Dusek Jennings and Henrdix (2020), Spawn Timing of Winter-Run Chinook Salmon in the Upper Sacramento River.  Available at:

Upper Sacramento River Summer Water Temperatures – Lesson #6: 53ºF Is Key

Following a series of posts, this is the last 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 #6. The will be the last in the series because the past has become the present, and the focus must now shift to drought conditions and management in 2021 and beyond.1

The best science is that a 53oF daily-average temperature (DAT) is protective of salmon eggs/embryos in their gravel redds in the Sacramento River in the spring and summer spawning season.  But the Bureau of Reclamation, without enough pushback from NMFS and the State Water Board, continues to manage for higher water temperatures in the 10-mile spawning reach of the Sacramento River from Keswick Dam (River Mile 300) downstream to the mouth of Clear Creek (RM 290).2

A 53oF DAT is close to the 55oF seven-day-average-daily-maximum temperature (7DADM) that NMFS cited in its Lesson #6, quoted above.  The Bureau of Reclamation met that target in wet year 2019 (Figure 1).

Protection was compromised in 2020 (Figure 2), as Reclamation only maintained the 53oF DAT at Clear Creek in the peak mid-summer egg and embryo period.  Since the 2019 Biological Opinion, this  has become Reclamation’s dry-year strategy.  This dry-year strategy is a partial improvement over the prior dry-year strategy of 56ºF DAT at Clear Creek that Reclamation employed in 2015 (Figure 3), when there was very low over-summer survival of eggs and embryos, and very little fry and smolt production, of winter-run salmon.

Water temperatures were even higher in May 2021, reaching 58-62oF early in the month (Figure 4).  Such temperatures were high enough to compromise the health and reproductive success of the many pre-spawn adults holding below Keswick Dam.  First, elevated water temperatures delay spawning.  Second, adults have higher disease vulnerability at water temperatures above 60oF.  Third, eggs and embryos from holding adults subjected to water temperatures higher than 60oF have higher pre-hatch mortalities and abnormalities.

With tentative approval by the State Water Board of Reclamation’s draft summer temperature management plan for 2021, we can expect a 56oF DAT at Clear Creek target for the peak June-July egg incubation season.  Such operation allows significant hydropower production and water deliveries from Shasta storage releases, as well as water exports from the Trinity River.  If these were curtailed, Reclamation could achieve a target of 53oF DAT at Clear Creek and save salmon.

Figure 1. Water temperatures May-October, 2019 in the Sacramento River at Keswick Dam-KWK (RM 300), Redding-SAC (RM 295), Clear Creek-CCR (RM 290), and Balls Ferry-BSF (RM 276).

Figure 2. Water temperatures May-October, 2020 in the Sacramento River at Keswick Dam-KWK (RM 300), Redding-SAC (RM 295), Clear Creek-CCR (RM 290), and Balls Ferry-BSF (RM 276).

Figure 3. Water temperatures May-October, 2015 in the Sacramento River at Keswick Dam-KWK (RM 300), Redding-SAC (RM 295), Clear Creek-CCR (RM 290), and Balls Ferry-BSF (RM 276).

Figure 4. Daily average water temperature in the winter-run salmon spawning reach of the Sacramento River below Keswick Dam (KWK – RM 300) and above Clear Creek (CCR – RM 290) in April-May 2021. Safe level for holding adult salmon for reproduction success is 56ºF. The safe level for disease potential in holding adults is 60ºF.

Figure 4. Water temperatures in the Sacramento River at the lower end of the spawning reach above Clear Creek (CCR), May 1-May 30, 2021.



The Forgotten Green Sturgeon

Adult Green Sturgeon and General Life History –  Source

The Southern Green Sturgeon is an anadromous fish species that spawns in the upper Sacramento River near Red Bluff CA.  It is a state and federal listed endangered species.  Adults migrate from the ocean to spawn in April-May in gravel/cobble riffles and pools.1  The eggs hatch in approximately 12 days.  The young larval or fry are susceptible to stress and mortality if water temperature warm too quickly into the 65-70oF range.  Optimal water temperatures for embryos and larvae are 60-65oF.2  Survival declines at higher temperatures, with 68oF considered lethal.

The fry grow quickly and begin moving downstream from mid-May to mid-July, as shown by screw trap collections at the Red Bluff Diversion Dam (Figures 1 and 2).  It is the reaches below Red Bluff downstream into the middle river near Wilkins Slough where larvae-fry are vulnerable to excessive spring-season water temperatures.  There are minimal available records of juvenile survival in the middle and lower river, although some data indicate they do not move to the Delta and Bay until the first fall rains.

Juvenile production measured at Red Bluff is lower in drought years (Figure 2) as a consequence of low flows and high water temperatures. With water temperatures already high in early May 2021 (Figure 3), the prognosis for young green sturgeon production is not good.

Figure 1. Screw traps at Red Bluff Diversion Dam in Sacramento River. USFWS photo.

Figure 2. Green sturgeon collections in Red Bluff screw traps 2003-2012. Note poor survival in drought years 2007 through 2009. Source.

Figure 3. Water temperature of the Sacramento River at Red Bluff (RDB rm 240) and Wilkins Slough (WLK rm 125) April-June in 2014, 2015, and 2021. Note the lethal water temperature for green sturgeon larvae is considered to be 68oF.


  1. Brown, K. Evidence of spawning by green sturgeon, Acipenser medirostris, in the upper Sacramento River, California. Environ Biol Fish 79, 297–303 (2007).

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.