Shasta Dam Update – July 18, 2021

There is still time to take action needed to save some of this year’s salmon production in the Sacramento River.1 Reclamation must immediately stop its irresponsible operation and revert to a maximum 5000 cfs Shasta Dam release, with no release from the middle gates and with minimal peaking power releases or input from Whiskeytown Reservoir.2

Here is the situation right now:

  • The last two weeks of July in the spawning reach near Redding will have daily average air temperatures over 85ºF, with highs of 100-107ºF.
  • Shasta Reservoir is losing 10,000 acre-feet and ½ foot of water-surface elevation per day, due to excessive storage releases (Figure 1).
  • Lower elevation dam release gates are about to go above the top of the cold water pool (Figure 2). This will reduce Reclamation’s ability to sustain cold-water releases through the summer for downstream salmon.
  • Peak power releases draw warmer water from surface layers (Figure 3).
  • Release of warmer 56-57ºF water from Whiskeytown Reservoir via Spring Creek Powerhouse into Keswick Reservoir further compromises Shasta’s cold-water pool3 (Figure 4)
  • As Reclamation had predicted in its Temperature Management Plan, the bottom side gates will have to be opened to sustain cold water releases by mid-August, which will accelerate the loss of the cold-water pool and compromise cold-water dam releases.
  • Diversions from the Trinity via Whiskeytown are getting warmer, requiring more of Shasta’s cold-water to overcome warming of Shasta/Keswick reservoir releases.
  • Shasta’s warmer peaking power water also requires more cold-water pool water to maintain the target <54ºF Keswick Dam release temperature.

It is essential to maintaining cold-water releases from Shasta Dam into early October to save winter-run salmon reproduction in this critical drought year. Cold water ran out in the summers of 2014 and 2015, and the winter-run salmon runs plummeted.4 Recovery of this critically endangered species5 requires an all-out-effort to protect the survival of eggs and embryos over the summer in the 10-mile spawning reach below Shasta and Keswick dams.

Conclusions and Recommendations

  1. Releases from Whiskeytown Reservoir (Trinity River water) should be minimized, because the 2000 cfs of 56-57ºF water must be neutralized with water from the Shasta cold-water pool. It is taking about 1000 cfs of 48ºF water from Shasta to keep Keswick releases less than 54ºF. Eliminating the import of Trinity River water would save 2000 acre-feet of Shasta storage and cold-water pool volume each day. That would save over 100,000 acre-feet of Shasta storage and over 200,000 acre-feet of Trinity storage by the end of September.
  2. In addition to the cutting the Shasta release by 1000 cfs by discontinuing the need to offset warm Whiskeytown water, Shasta releases should be cut a further 1000 cfs by shutting off warm water from the middle gates (see Figure 2). This would further preserve the volume of the cold-water pool and save an additional 100,000 acre-feet of Shasta storage.

These actions would allow a 5000 cfs releases of <54ºF water from Keswick Dam through September, which would save a significant proportion of the endangered Winter-Run Chinook salmon. It would also save nearly 400,000 acre-feet of reservoir storage for water year 2022.

Figure 1. Shasta Reservoir inflow, outflow, and storage, 1-16 July, 2021.

Figure 2. Shasta Dam operations scheme and reservoir conditions during the first week of July 2021. Note middle remain open to accommodate peaking power releases and high downstream irrigation deliveries.

Figure 3a

Figure 3b Figure 3a and 3b. Hourly water temperature (a) and flow (b) release pattern from Shasta Dam during first half of July 2021. Note most peaking-power releases are in afternoon and evening hours, with water temperatures several degrees higher during the daily peak generation. Daily average releases were 6500-7500 cfs, with peaks on the 6th and 9th.

Figure 4a

Figure 4b Figures 4a and 4b. Hourly water temperature (a) and flow (b) release pattern from Whiskeytown Dam during first half of July 2021. Note most peaking-power releases are in afternoon and evening hours, with water temperatures in the middle range of the daily pattern or about 1ºF below the daily maximum. Note the base flow of 250 cfs is to Clear Creek, with the remainder to Spring Creek powerhouse on Keswick Reservoir. Also, note peak releases to the Spring Creek powerhouse were about 3500 cfs for 12 hours from July 3-8. Daily average releases rose from about 1000 cfs on July 1 to 2000 cfs on July 4, then dropped to 1500 cfs on July 11, only to increase again through July 15.

 

 

  1. As much as 50% of spawning may yet occur. See https://escholarship.org/uc/item/00c1r2mz 
  2. This is an update from my late June report on Shasta Dam operations.
  3. It takes about 1000 cfs of Shasta’s cold-water pool to cool 2000 cfs of 56-57ºF Whiskeytown water.
  4. https://www.fisheries.noaa.gov/feature-story/endangered-winter-run-chinook-salmon-increase-millions-offspring-headed-sea
  5. https://www.fisheries.noaa.gov/video/species-spotlight-sacramento-winter-run-chinook-salmon

State Water Board to Decide Fate of Shasta and Scott River Salmon and Steelhead – Part 2, the Scott River

On July 1, 2021, staff from the State Water Resources Control Board (State Board) held a public Zoom meeting to provide information and solicit input on potential actions that could be implemented to address low flows in the Scott River and Shasta River watersheds (Figure 1) during the ongoing drought.  The Scott and Shasta rivers are major salmon and steelhead producing tributaries of the Klamath River. The State Board’s July 1 workshop sought input and options prior to taking action.   

 CSPA is providing comments through this three-part series.  Part 1 was the introduction, with a description of the general problems and solutions.  This is Part 2, with specific comments on the Scott River.  Part 3 will cover the Shasta River.

The Scott River Problem

The Scott River has a chronic low streamflow problem that occurs in the summer and fall of most years.  Only in very wet years, do ranchers and fish for the most part get the water they need.  In most years, nearly all the water in the watershed goes to agriculture, while the lower river and its tributaries run virtually dry.  Fish survive in the upper reaches of the river and in the lower tributaries that receive snowmelt and spring water from the adjacent Marble and Trinity mountains.  There are also spring-fed refugia in the middle sections of the river and In tributaries to the lower sections of the river.  But at many locations in the watershed, a large portion of the surface-water flow goes underground into near-surface aquifers, only to resurface as springs and be further diverted or extracted by wells, or go back underground.

The California Department of Fish and Wildlife is recommending summer minimum flows from 30-50 cfs at the lower end of the river to protect over-summering juvenile Chinook and Coho salmon, and steelhead.  These recommended flows represent roughly half of the available summer baseflow water supply in the Scott River.  Without a minimum flow requirement, almost the entire summer baseflow is  consumed by a carefully distributed water supply extraction system regulated by seniority-based surface water rights and overseen by the State Board or by minimally regulated groundwater pumping.  A large portion of the consumption occurs by means of minimally regulated shallow well pumping from the valley’s alluvial floodplain aquifer.  This supplies water for stock watering, pasture irrigation, or large scale sprinkler irrigation of hayfields.  The aquifer is recharged by surface flows and applied irrigation, and in places is augmented by beaver dam flooding.  The floodplain was once known as “beaver valley”.  However, much of such wetland floodplain habitat has been lost to channelization to enable irrigated agriculture.

There are many areas in the watershed that provide refugia for over-summering salmon and steelhead.  The extent of these refugia decreases over the summer as the surface water supply declines and springs cease flowing.  The loss of refuge habitat over the summer is greatest in drought years.  As the extent of refuge habitat declines, juvenile salmon and steelhead become more concentrated or succumb to “catastrophic stranding” where they die from refugia drying up or overheating.  Many refugia are on private lands.  Many are unidentified.  They need to be identified and surveyed to determine their characteristics and need for protection.

Drying rivers also pose problems for emigrating juvenile and immigrating adult salmon and steelhead in the fall and winter.  When fall rains and winter snow are lacking or late, juvenile fish are hindered or blocked from moving downstream to the Klamath River.  Adult fish cannot move upstream to spawning grounds in the valleys.

General Solution Options for the Scott River

Other than CDFW’s recommended minimum instream flows to save the fish (which would be successful), there are further options to help the fish.  One major option is to protect through the summer-fall season the many refuge areas that are present and functioning at the end of the spring snowmelt season. This can be accomplished in several ways:  (1) not allowing any diversion of surface or groundwater within or near the designated refuge; (2) pumping well water directly into the refugia; (3) diverting other surface waters into the refugia; and (4) protecting and enhancing refuge habitat (e.g., cattle fencing, riparian plantings, channel improvements).  The basic concept is to protect and enhance cold-water habitats of the refugia.  Each refuge will have its own prescription.  Some may benefit from introduced beaver colonies.  Note that some landowners working with CDFW and local stakeholder groups have accomplished some of these actions at varying scales of effort and with varying degrees of success.

Another solution option is a program to scale back seasonal agricultural water use based on the needs of fish and their habitat, as well as those of the landowners.  For example, a major problem for Scott River salmon is not being able to ascend into Scott Valley in the fall because of low streamflows.  Unlike the Shasta River Watershed, in which irrigation is disallowed after October 1, irrigation is allowed into December in the Scott watershed.  Scott Valley hay-crop irrigators in particular could cease irrigating a month or two earlier, foregoing late season cuttings.  This option was suggested by a landowner of a large ranch who was even willing to use his large-capacity wells to help water the river during the fall salmon migration.

Specific Recommended Solutions

The following recommendations offer large potential benefits with limited impacts and costs.

1.      Focus on the surface water irrigation diversions – all should cease in summer of dry years

Two large diversions with large canal distribution systems make up the bulk of the surface water diversions in Scott Valley, at least in wetter years or spring of drier years.  If these have not as yet cut back diversions as in most dry years, their diversions should cease.  The largest diversion, Young’s Dam, is a relatively large concrete structure with a fish ladder (Figure 2).  In summer of dry years, it usually does not divert, but does back up water in the river channel, causing significant rises in water temperature.  More flow would minimize such heating.  More flow is necessary to provide upstream passage of adult salmon in late summer and fall through the dam’s fish ladder, even when the dam is not diverting water.

The second largest surface diversion is Farmers Ditch, which diverts directly from the Scott River channel (Figure 3).  It too usually does not divert in summer of dry years, due to lack of surface flow.  Prior to ceasing its diversions, it contributes to drying up the river in the downstream tailings reach.

There are many small diversions1 in the middle and upper valley from reaches of the river and lower tributaries that retain flows in the summer.  Locally, they divert significant portions of the available streamflow.  Some are crudely designed and operated, and are unregulated (Figure 4).  All surface diversions should cease operating, since most are from spring-fed stream reaches supporting rearing salmon and steelhead.  In many cases, such diversions contribute to the dewatering of downstream reaches.  One such example is lower Shackleford Creek, where multiple small diversions in flowing spring-fed sections in the several miles upstream contribute to the drying up of the creek near its mouth on the Scott River (Figure 5).

2.      Middle and lower reaches of Scott River affected by groundwater pumping – all well pumping from locations contributing to dewatering of the main channel of the Scott River or lower tributaries should cease pumping.

Most free-flowing reaches of the middle and lower Scott River and its lower tributaries are over-summering juvenile salmon and steelhead refugia.  Even warm low flows provide some cooler hyporheic flow to sustain young salmon and trout in microhabitat areas of the stream channel (Figure 6; also see videos referenced at the end of this post).  Such locations cannot support high population densities for long and thus could use added flow to sustain them.

3.      Refugia in middle and lower reaches of Scott River and lower tributaries affected by groundwater pumping could be supported by pumping cold groundwater into stream channels to help sustain refuge habitat.

In reaches where groundwater pumping is no longer needed, idle wells can pump cold groundwater directly into stream channels to sustain specific refugia or to provide added flow for fish migrations.  Many ponds situated within the Valley’s water table have cold water that could be drained or pumped to refuge areas.  The tailings reach in the upper end of the Valley has many such ponds.

Summary and Conclusions

All surface diversions from free-flowing reaches of the Scott River should cease in summer-fall of 2021.  All such reaches are fed by snowmelt or springs, and are most likely refugia for over-summer rearing salmon and steelhead.  All well pumping near the river and lower tributaries that may affect springs or hyporheic flow in refugia should be cut back to help sustain the refugia.  All refugia should be identified and classified to value and need.  Where feasible, wells or surface waters can supply supplemental water to sustain refugia.  All refugia should be mapped, surveyed, and characterized for need; high value  options should be identified and implemented.  All irrigation in the Scott Valley (not including stock watering) should cease by October 1, as is already done in the Shasta Valley.  Cutbacks of well pumping for Scott Valley irrigation should commence on a graded scale on August 1 and September 1.

Figure 1. The Scott River and Shasta River Valleys in northern California west of Yreka, CA (Yreka is located in the Shasta River Valley). The Scott and Shasta Rivers flow north into the Klamath River, which runs west to the ocean. The Salmon River watershed is immediately west of the Scott River watershed. The upper Trinity River watershed is immediately to the south of the Scott River watershed.

Figure 3. Farmers Ditch diversion located in upper middle valley on Scott River.

Figure 2. Young’s Dam and diversion located on the Scott River in mid-Valley.

Figure 4. An unnamed small diversion located in spring-fed reach of Scott River below tailings reach. Both the river and diversion ditch contained large numbers of juvenile coho salmon.

Figure 5. The mouth of Shackleford Creek on Scott River in late summer.

Figure 6. Reach of the lower Scott River upstream of Fort Jones near Eller Bridge, nearly dewatered by groundwater pumping and lowering of the groundwater table. Despite lack of flow, the reach retains some over-summering refuge pools sustained by groundwater and hyporheic flow. Eventually, these areas become too warm, and many thousands of juvenile salmon and steelhead die. Such areas would benefit from a cessation of irrigation with water sourced from adjacent wells. Idle wells could be employed to add cold water to sustain the refugia.

Available Videos of Scott River Refugia

 

 

 

  1. There are approximately 800 water right holders in the Scott River watershed.

Reclamation Begins Summer Shasta Operations that Sacrifice Endangered Winter-Run Chinook Salmon to Power Production and Irrigation Deliveries

Reclamation has begun its planned summer operation for winter-run salmon in this critically-dry summer of 2021. After delivering a lot of warm surface water from Shasta Reservoir to its downstream contractors this spring,1 Reclamation has now begun dipping into Shasta’s cold-water pool (Figures 1 and 2). Reclamation’s summer operation will encourage the holding salmon to spawn and, for a time, ensure the eggs can survive in the primary ten-mile spawning reach downstream to the mouth of Clear Creek (CCR). Reclamation’s plan would subsequently raise water temperatures later in summer, after peak spawning and embryo development have occurred.

In first five days (June 17-22) of the new operation, Reclamation met its target temperature. It has released about 8000 cfs of 53ºF water from Keswick Dam to the Sacramento River near Redding (Figure 3). It achieved the target by blending hydropower-peaking flows from Shasta and Whiskeytown dams in Keswick Reservoir, and then releasing the blended water to the Sacramento River below Keswick Dam. During this time, Reclamation released an average of 6500 cfs from Shasta Dam at 50-51ºF, and an average of 1200 cfs at 53ºF through the Spring Creek Powerhouse (SPP) from Whiskeytown, into Keswick Reservoir.

This operation is not sustainable over the summer. It uses more of the cold-water-pool volume than is necessary to maintain temperature control. It sacrifices the cold-water pool in order to continue power peaking and to maintain relatively high downstream irrigation deliveries. Considering all of the factors pushing Keswick release temperatures higher over the summer, there will not be enough cold water by the end of the summer to protect salmon.

High Shasta Dam releases in the afternoon and evening to meet peak power demands pull more water from the warmer surface waters of the reservoir (Figures 4-6). This then requires blending with cold-water releases to keep Keswick water cooler. A similar situation occurs with the Whiskeytown releases (Figure 7-8). In addition, water in Whiskeytown becomes progressively warmer over the summer and requires an ever-increasing amount of Shasta’s cold-water pool to cool that water. Atmospheric heating combines with heating of water from Shasta during power-peaking operations to further affect Keswick Reservoir’s water temperatures (Figures 9 and 10).

Reclamation’s current high demands on Shasta’s cold-water pool will thus require reverting in late summer to warmer water releases. This will lower the survival of late summer spawners and their eggs. It will also leave little cold water for fall-run salmon in October and November. Reclamation is willing to accept these trade-offs to make relatively high power and irrigation deliveries.

To reduce the loss of winter-run (and fall-run) salmon this summer, CSPA and two other organizations submitted an alternative Temperature Management Plan (CSPA TMP) to the State Water Board on May 23, 2021. The CSPA TMP would provide better summer water temperatures and salmon egg survival. The CSPA TMP, comprised of a transmittal letter, descriptive elements and spreadsheet, proposes a release of just 5000 cfs of 52-53ºF water from Shasta Dam’s gates and minimal warmer water inputs from Whiskeytown/Trinity. The CSPA TMP proposes a 5000 cfs release of 53-54ºF water from Keswick, with less daily peaking power production to limit withdrawals of warm water from the surface of Shasta reservoir.

The CSPA TMP would minimize impacts to the salmon and save approximately 200,000 acre-feet of Shasta storage. It would also save 200,000 acre-feet of Trinity storage. It would greatly reduce power production from five system powerhouses, though power generation capacity would still be available for periods of extreme power demand.

Above all, the CSPA TMP would reduce water supply deliveries in the Sacramento Valley and eliminate water transfers from Shasta in the summer and fall. Reclamation is willing to sacrifice a substantial portion of the Sacramento River’s salmon in order to prioritize agricultural water deliveries. The CSPA TMP prioritizes a system operation that will reasonably protect salmon, and allocates water supply based on the water that is available within the constraints of that operation.

Figure 1. Shasta Dam infrastructure and operations, and cold-water pool conditions, during the June 17-22 period. Note water release from PRG gates, drawing from the layer of water less than 48ºF, and release from middle gates of water that is 70ºF or warmer. The combined flow release from the Temperature Control Device was 6000-7000 cfs of 51-52ºF water.

Figure 2. Water temperatures (ºF) recorded at Sacramento River gages from Shasta Dam (SHD, RM 310) downstream to Red Bluff (RDB, RM 240) 5/1-6/16, 2021. Keswick Dam (KWK, RM 300) is the release point from the Shasta Dam complex to the Sacramento River. Spawning area is ten miles downstream of Keswick to mouth of Clear Creek (CCR). Red arrow points out yellow highlight of recently changed operation to benefit salmon spawning.

Figure 3. Water temperatures (daily average. ºF) from Shasta Dam release (SHD) and from Keswick Dam (KWK, RM 300) downstream through primary winter-run spawning reach to gage located just upstream from mouth of Clear Clear Creek (CCR, RM 290). Note: the difference between SHD and KWK release temperatures are due to inputs to Keswick Reservoir from Whiskeytown from Whiskeytown Reservoir through the Spring Creek Powerhouse (SPP) and to internal heating and mixing in Keswick Reservoir. The compliance control point gage is SAC, located at the midpoint of the ten-mile spawning reach. The compliance point target was 55ºF during the period.

Figure 4. Water temperature (ºF) at gage SHD immediately downstream of Shasta Dam, June 17-22.

Figure 5. Shasta Reservoir hourly outflow (cfs), June 17-22.

Figure 6. Water temperature (ºF) at gage SHD immediately downstream of Shasta Dam, June 17-22.

Figure 7. Hourly measued water release (cfs) from Whiskeytown.

Figure 8. Water temperature (ºF) at gage SPP immediately downstream of Spring Creek Powerhouse June17-22.

Figure 9. Keswick Reservoir hourly outflow (cfs), June17-22.

Figure 10. Water temperature (ºF) at gage KWK immediately downstream of Keswick Dam, June17-22.

Hatchery Delta Smelt 2021

Efforts continue to gain approval for releasing hatchery-raised delta smelt in the San Francisco Bay-Delta Estuary. However, given a poor prognosis for a successful introduction, the chances of approval are not good.1  The biggest obstacle is the absence of a location to release the hatchery-raised fish that will allow their survival and thus contribute to the species’ recovery. Another problem is the potential detrimental effect on the remaining wild smelt from genetic compromise.

To me, the answer to the second issue is clear. With few if any “wild” delta smelt left on Earth, it is essential to get as many hatchery smelt out into the wild as soon as possible to save the species. Let the genetics get worked out later by Mother Nature.

Two locations for release of hatchery smelt seem most plausible: the low salinity zone in the west Delta/eastern Suisun Bay and the Deep-Water Shipping Channel in the north Delta. These are primary late spring and early summer nursery areas that are most likely to have the right habitat conditions (water temperature and low salinity) and food supply. These two locations were the last known concentrations of juvenile delta smelt (Figure 1) from the last strong adult spawn in 2012 (Figure 2).

The better of the two sites is the eastern-Bay/west-Delta location, because the ship-channel gets too warm by summer (Figure 3). In contrast, the region between Collinsville in eastern Suisun Bay and Decker Island in the west Delta is cooler and within the low salinity zone (Figures 4 and 5). A nighttime near-bottom release into cooler, deeper channel waters would give the hatchery smelt at least a minimum opportunity to acclimate to the warm Bay-Delta waters.2

Figure 1. Last known prime late spring and early summer nursery area of delta smelt (2012, 20-mm survey). Red lines denote approximate location of X2 (~2000-4000 EC) at the time.

Figure 2. Adult delta smelt catch index from monthly winter trawl surveys 2002-2021.

Figure 3. Water temperature (ºC) and salinity (EC) in spring 2020 in Deep Water Ship Channel.

Figure 4. Water temperature (C) and salinity (EC) in spring 2021 in Sacramento River channel near Collinsville in eastern Suisun Bay.

Figure 5. Water temperature (ºC) and salinity (EC) in spring 2021 in Sacramento River channel near Decker Island in the western Delta.

Peaking Power at Shasta Dam in Summer 2021 – Saving Winter Run Chinook Salmon

In a recent 6/13/21 post, I discussed various tradeoffs of Shasta Reservoir operations on water supply deliveries, power production, and salmon survival for summer 2021. In that post I made reference to tradeoffs with peaking power production at the Shasta hydropower system. This post provides more information on those potential tradeoffs.

Peaking Power Production

Peaking power refers to the release of varying amounts of water through power turbines on a within-day schedule to meet the peak power demands of the regional electric grid. Inflows into Keswick Reservoir near Redding show the peaking power production schedule from Shasta Dam and Whiskeytown Dam into Keswick Reservoir on the Sacramento River (Figure 1). Over a recent two-day period, June 12-14 2021, hourly inflows to Keswick Reservoir ranged from 1900 cubic feet per second (cfs) to 17,500 cfs. Peak inflows were in late afternoon and evening, reflecting peak power demands. Minimum inflows were in the early morning, when power demand is low.

Peaking Power and Water Temperature from Shasta Dam

High releases for peaking power at Shasta Dam can draw warm water from near the surface of Shasta Reservoir (Figure 2). Water temperature below the dam increased from 50ºF to 56ºF in the recent example peaking periods, June 12-14. The positive relationship between dam release flow and water temperature is obvious (Figure 3).1

Peaking Power and Water Temperature from Whiskeytown Dam

In contrast to Shasta Dam, there was minimal influence on water temperatures when there were peaking releases from Whiskeytown Dam from June 12-14. The release water temperatures into Keswick Reservoir through the Spring Creek Powerhouse are minimally influenced by the flow rate (Figures 4 and 5). On June 13, there was no peaking through Spring Creek Powerhouse, but there was little variation in water temperature from peaking days on June 12 and 14.

Summary of Shasta-Keswick Operations

Shasta-Keswick operations is about to enter a new phase of summer operations. Under the Bureau pf Reclamation’s planned operations, there will be larger volumes of exports from the Trinity River system through Whiskeytown Reservoir over the summer. There will also be larger release volumes from Keswick Reservoir to meet increasing downstream contractor demands (Figure 6).

Proposed Operations

The proposed CSPA Temperature Management Plan2 for June-October, 2021 would provide a lower Keswick Dam release. First, Trinity exports would end, except for releases of 300 cfs down Clear Creek, because Trinity water releases through Spring Creek Powerhouse are already pushing the threshold temperature of 53ºF. Second, Shasta release would be limited to releases from coldwater pool at 52ºF to provide 5000 cfs total Keswick release, thereby saving Shasta storage. Third, peaking power at Shasta Dam would be minimized to ensure that warm surface waters are not drawn into the TCD gates (Figure 7) during peaking operations.

Sustaining the cold-water pool in Shasta through the summer is a function of (1) maintaining total storage and cold-water-pool volume in storage: (2) reducing Whiskeytown releases when they become too warm (>53ºF); and (3) minimizing warm water from peak power releases. Such a strategy would help save winter-run salmon eggs in the summer spawning season.

Figure 1. Inflow (cfs) to Keswick Reservoir from Shasta Dam and Spring Creek Powerhouse (cfs), June 12-14, 2021.

Figure 2. Water temperature (ºF) of the water released from Shasta Dam, June 12-14, 2021.

Figure 3. Relationship between water temperature and Shasta Dam release volume, June 12-14, 2021.

Figure 4. Total reservoir release (cfs) from Whiskeytown Dam, June 12-14, 2021. Note that of the minimum 250 cfs release, about 125 cfs were released to Clear Creek to maintain base flows and were not releases through Spring Creek Powerhouse.

Figure 5. Water temperature of water exiting the Spring Creek Powerhouse into Keswick Reservoir, June 9-14, 2021.

Figure 6. Summary of Shasta operations, June 1-13, 2021. Note SAC is gage station 5 miles below Keswick Dam on Sacramento River. Source: https://www.usbr.gov/mp/cvo/vungvari/sactemprpt.pdf

Figure 7. Shasta Dam operations and reservoir storage conditions on June 10, 2021. Source: https://www.usbr.gov/mp/cvo/vungvari/sactemprpt.pdf .

  1. At other times, depending on specific conditions and operations, the opposite relationship is true.  See https://calsport.org/fisheriesblog/?p=3596, Figure 6, for example from 2014 when higher temperatures were associated with lower release volumes.
  2. Referenced in https://calsport.org/fisheriesblog/?p=3714.  The May 23, 2021 CSPA Temperature Management Plan proposed limiting Trinity exports to 300 cfs for the entirety of the June-October period, to be released exclusively down Clear Creek.  In addition to the water temperature benefits in the Sacramento River, such operation would also conserve cold water and overall storage in Trinity Reservoir.