Welcome to the California Fisheries Blog

The California Sportfishing Protection Alliance is pleased to host the California Fisheries Blog. The focus will be on pelagic and anadromous fisheries. We will also cover environmental topics related to fisheries such as water supply, water quality, hatcheries, harvest, and habitats. Geographical coverage will be from the ocean to headwaters, including watersheds, streams, rivers, lakes, bays, ocean, and estuaries. Please note that posts on the blog represent the work and opinions of their authors, and do not necessarily reflect CSPA positions or policy.

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

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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

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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). https://doi.org/10.1007/s10641-006-9085-5 ↩
  2. https://www.waterboards.ca.gov/waterrights/water_issues/programs/bay_delta/california_waterfix/exhibits/docs/petitioners_exhibit/dwr/part2/DWR-1102%20Van%20Eenennaam%20et%20al.%202005.pdf ↩

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

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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.

Shasta Experiment #3 – Saving the Cold-Water Pool or Increasing Irrigation Deliveries?

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In early April 2021, the Bureau of Reclamation began a series of tests to determine if releases of water that bypass the powerhouses at Shasta Dam could help save Shasta’s cold-water pool through the summer and fall and thus help sustain salmon spawning in the Sacramento River below Shasta.  This post describes the third experiment in the series.

Experiments or tests of the powerhouse bypass continued at Shasta Dam from 4/19-4/24, 2021.  But the apparent goal of conserving cold-water pool volume for later in summer seems to have morphed into an acute operational phase of releasing a lot of water for contractor deliveries early in a critical drought year.  This higher release volume shows little regard for this year’s production of endangered winter-run salmon.  This unprecedented federal operational regime has not been approved by the California State Water Resources Control Board, nor has it been endorsed by the federal National Marine Fisheries Service, which is charged with protecting endangered salmon.

What was billed as a power turbine bypass at the federal Shasta Dam to save cold water storage has turned out to be a unique way to release a lot of Shasta’s remaining critical dry year storage (as well as cold-water pool supply) to Sacramento Valley water contractors.  The approach is both ingenious and insidious, and is likely a leftover planned action by the previous federal administration, whose goal was to maximize water deliveries to Central Valley farmers without regard for an already fragile and weakened ecosystem.

The approach entails releasing warm water from the surface of the reservoir into the upper river outlets (as in the above photo) instead of through the deeper cold water through the power penstocks and powerhouse (five penstocks and powerhouse are to left of spillway in above photo). 1

The problem is that too much warm water is being released, so cold water must also be released to overcome the release of relatively warm surface water (Figure 1), via mixing in downstream Keswick Reservoir before ultimately being discharged into the Sacramento River downstream of Keswick.  Total releases reached 12,000 to 16,000 cfs in the afternoon peak-power-demand periods from 4/19-4/24 (Figure 2).  Water temperatures topped out at 56-58ºF in the non-peak hours (Figure 3), when releases were dominated by spillway releases (Figure 4).  Shasta Reservoir storage dropped approximately 30 TAF (from 2,360 TAF) during the four-day period.  Downstream water temperatures increased up to several degrees during the four-day period (Figures 5-7).  Downstream water deliveries to contractors increased as well, based on differences in gaged flow between the upper and middle river (Figure 8).

In summary, power bypass releases from Shasta reservoir occurred in this critical drought year, resulting in higher downstream river water temperature, no cold-water pool saving, lower reservoir storage, and higher contractor deliveries.  The higher water temperatures (>56ºF) exceed state water quality standards and existing water temperature targets for the upper Sacramento River.

Figure 1. Shasta Dam and reservoir schematic depicting late April 2021 release regime. Warm surface water is released through six upper outlets. Colder layered water is released through five middle gates of the Temperature Control Device (TCD) outlet tower on the face of the dam to the powerhouse via the five penstocks.

Figure 2. Shasta reservoir storage hourly release pattern 4/19 – 4/24, 2021. The graph shows total combined powerhouse and spillway releases. Note powerhouse peaking-power releases generally occurred only in late afternoon or early evenings or mornings. Spillway releases appear to have been continuous: 4,000 cfs on 4/21-22, and 6,000 cfs on 4/23-24

Figure 3. Shasta Reservoir hourly release water temperature pattern 4/19 – 4/24, 2021. The water temperature is that of water below the dam made up of blended spillway and powerhouse releases. Comparison with Figure 2 shows that minimum water temperatures occur during power peaking events that draw from cold-water pool in Shasta Reservoir.

Figure 4. Daily average releases (cfs) from Shasta Dam river outlets to spillway bypassing power house, showing releases from 4/18-4/23.

Figure 5. Water temperature below Keswick Dam 4/19-4/24, 2021. Note gradual increase in water temperature from increasing spillway releases during period.


Figure 6. Water temperature above mouth of Clear Creek ten miles below Keswick Dam 4/15-4/24, 2021. Note increase from increasing spillway releases beginning on 4/19. Note existing target temperature for this gage is daily average 56ºF.

Figure 7. Daily average water temperatures in the lower Sacramento River 4/1-4/24, 2021. Note RDB (Red Bluff) is lowermost gage. Note sharply higher water temperatures during the 4/19-4/24 test period. See Figure 9 for location map.

Figure 8. Daily average river flows in the lower Sacramento River 4/19-4/24, 2021. Note the difference between WLK and KWK gages represent approximate water deliveries to contractors. Note VON (Verona) is lowermost gage and is influenced heavily by Feather River inflows. See Figure 9 for location map.

Figure 9. Gage locations

 

Shasta Experiment #2 – Saving the Cold-Water Pool

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In the afternoons of 4/15 and 4/16, the Bureau of Reclamation conducted a second set of experiments or tests of the powerhouse bypass at Shasta Dam with the apparent goal of conserving the volume of Shasta Reservoir’s cold-water pool for later in the summer.    Reclamation released warm surface water from Shasta Reservoir into upper Keswick Reservoir through the upper river outlets to the dam spillway (see inset at right), bypassing the TCD and powerhouse.  Water temperature immediately below Shasta Dam reached values greater than 70ºF in the early afternoon on the 14th and 15th (Figure 1).  The river outlet releases occurred between the normal daily peak-power releases through the powerhouse (Figure 2).  In the prior test (Exp #1) in the early morning hours of 4/11, water temperature below the dam reached only 55ºF, as some cold water was also being released through the powerhouse.

After mixing occurred in Keswick Reservoir, water temperature of the Keswick release water to the Sacramento River increased approximately 2ºF to 52ºF (Figure 3).  The total reservoir release also increased about 1,300 cfs to 6400 cfs from the Exp #1 release level (Figure 4).

Overall, the test showed that bypassing the powerhouse can potentially save cold-water pool volume in Shasta Reservoir, although this bypass increases water temperatures in the upper Sacramento River.  As long as Keswick release temperature remains below its upper limit (in this case 53ºF), the option of bypassing power appears to have promise in conserving cold-water pool volume in Shasta Reservoir.

In this particular case, with the increase in total release to 6500 cfs, it is difficult to determine the amount of cold-water pool saved.  With the dam’s river-outlet water temperatures higher than 70ºF, it takes a lot of cold-water powerhouse release to cool it down to meet target levels in the upper Sacramento River.  It appears that operators were able to maintain normal peaking power levels while also releasing some warm reservoir surface water, with only a small increase in downstream river water temperature.  However, the additional loss of Shasta storage, in this case approaching 3000 ac-ft per day, will negatively affect the summer cold-water pool supply.

Figure 1. Water temperature immediately below Shasta Dam on 4/15-4/16, 2021. Note afternoon peaks corresponding to upper outlet releases

Figure 2. Dam release 4/14-4/16, 2021. Note afternoon upper outlet releases were 3000 cfs on 4/14-15. High 13,000 cfs releases between spillway releases late on 4/15 were for peaking power and were necessary to cool Keswick Reservoir to 50ºF below dam (see Fig 1).

Figure 3. Below Keswick, water warmed to 52ºF in the afternoon of 4/15.

Figure 4. Keswick release increased to 6500 cfs on 14th.