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.

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.

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

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

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.


Summer Shasta Releases Are Too High and Lower Sacramento River Summer Flows Are Too Low: Lessons Learned – #5

Following an introductory post, this is the seventh 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 #5.

The reason for high summer releases to the Sacramento River from Shasta and Keswick reservoirs is to meet the demands of Sacramento Valley water contractors for stored water.  For example, in 2012, summer releases to the Sacramento were 15,000 cfs, with roughly 7000-8000 cfs diverted in the Sacramento Valley for water supply use (Figure 1).

The Bureau of Reclamation learned during the 2012-2015 drought that, if the previous year was wet, it must still limit water releases in summer of dry years to 12,000-13,000 cfs (Figures 2 and 3) to preserve Shasta Reservoir’s cold-water pool supply.  One consequence of this limitation as implemented has been less flow in the lower river 150-200 miles downstream.  This reduced flow has exacerbated water temperature problems in the lower river.  Reclamation has likely also reduced water deliveries in the Sacramento Valley to some degree, but the extent of any such reductions is difficult to tease out.

Because of the lessons learned, Reclamation in 2018 targeted a 53oF water temperature limit in the main spawning reach of winter-run salmon from Keswick Dam (RM 300) down to the mouth of Clear Creek (RM290) (Figure 4).  In the past, the water temperature limit had been higher (56-58oF).  In 2020, the target was once again set higher to sustain a depleted cold-water pool supply through the summer and fall. The target in the spawning reach in drought years 2014 and 2015 was 56oF, which proved ineffective at providing egg/embryo survival.

One of the actions to sustain the cold-water pool has been to limit June-July Keswick releases (Figure 5) to near 11,000 cfs in wet years (2017 and 2019).  Such action cuts into water supply deliveries and leads to reduced flows (Figure 6) and excessive water temperatures (>70 oF, Figure 7) in the lower 200 miles of river.  Without simultaneous reductions in Sacramento Valley water deliveries, reductions in Keswick releases lead to excessive water temperatures downstream of the upper 10-mile salmon spawning reach.   This violates the Central Valley Basin Plan’s temperature standard for the lower reaches of the Sacramento River (68oF).  It causes stress on rearing and migrating salmon and sturgeon, and if high enough severely retards upstream migration of adult salmon.

The obvious lesson learned is that Reclamation must limit summer Shasta cold-water storage releases and maintain sufficient lower river flows.  This will necessarily require Reclamation to more greatly restrict water supply deliveries in the Sacramento Valley than it has historically and recently.

Figure 1.

Figure 2.

Figures 1-3. Sacramento River flow (cfs) at Keswick Dam (rm 300) and Wilkins Slough (rm 120) in summer of dry years 2012, 2018, and 2020. Note: the difference between

Figure 4. September-October water temperatures in the upper Sacramento River at Clear Creek (river mile 290) from 2012-2020. Note loss of temperature control in 2014 and 2015. Note limited control in 2013, 2018, and 2020. Note meeting target 53oF 2012, 2016, 2017, and 2019

Figure 5. Flow rates below Keswick Dam in June-July 2012-2020.

Figure 6. July-September Sacramento River flow rates at Wilkins Slough (rm 120) 2015-2020. Note flows were compromised in summer 2016 and 2017 to help preserve Shasta’s cold-water pool supply and upper river water supply deliveries.

Figure 7. Water temperatures in Sacramento River at Wilkins Slough (river mile 120) May-Oct, 2015-2020

Shasta Water Temperature Experiment #1 4/10-4/11, 2021

In the evening of 4/10 and early morning hours of 4/11, the Bureau of Reclamation began releasing warm surface water from Shasta Reservoir through the upper river outlets to the dam spillway (see inset at right), bypassing the Shasta Temperature Control Device (TCD) and the Shasta powerhouse,  forgoing power production.

Figure 1 shows the warm water beginning at 20:00 4/10 and continuing to 8:00 4/11.  Reclamation changed the recent pattern of midnight releases, raising releases from about 3000 cfs releases to about 6000 cfs (Figure 2).  This was possible due to the available capacity of the upper-level river outlets on the dam spillway.  Reclamation also curtailed peaking power releases through the TCD and penstocks on the evening of 4/10.  The 55ºF temperature in Figure 1 immediately downstream of Shasta Dam reflects the temperature of the lake’s surface water at the upper level outlets (Figure 3).

During and after the experiment, water temperatures in the Sacramento River downstream increased less than 1ºF, both immediately below Keswick Dam (Figure 4) and 10 miles further downstream at the Clear Creek gage (Figure 5).

Overall, the experiment shows that forgoing some peaking power by bypassing penstocks and releasing warmer upper-level lake water in April can save cold-water-pool volume, although with a small increase (0.5ºF in this case) in downstream water temperatures under these specific conditions.

Figure 1. Water temperature immediately below Shasta Dam at gage SHD 4/7-4/12, 2021. Note substantial increase from 20:00 4/10 to 06:00 4/11 during Exp #1.

Figure 2. Inflow to Keswick Reservoir from Shasta Dam 4/7-4/12, 2021. There was also 400-750 cfs of Trinity water entering Keswick from Spring Creek Powerhouse.

Figure 3. Water temperature profile in lake at Shasta Dam on 4/14/2021. Note water temperature in mid-50s at level of the upper six outlets to the spillway, in contrast to the cooler 50ºF water entering the penstocks via the middle gates of the TCD.

Figure 4. Water temperature of water released from Keswick reservoir 4/7-4/12, 2021. Note temperature increased up to 0.5-0.8ºF during and after the experiment.

Figure 5. Daily average water temperatures at selected gages 4/1-4-12, 2021. Note temperatures at Clear Creek confluence (CCR, in bold), with little increase on 4/10-4/11.