Category Archives: Water Quality

Cache Slough Tidal Wetland Restoration – Update More misguided resource-damaging habitat restoration for an already highly altered and compromised Delta

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Cache Slough Complex Restoration

The Cache Slough Complex is in the lower (southern) Yolo Bypass in the north Delta region (Figure 1). It is the focus of the state’s tidal wetland restoration EcoRestore Program that spans 16,000 acres in the Cache Slough region of the Sacramento-San Joaquin Delta.

The 53,000-acre Cache Slough Complex is located in the northwest corner of the Sacramento-San Joaquin River Delta in Solano and Yolo counties (Figure 1). The Yolo Bypass receives inflow directly from the Sacramento River (Fremont Weir), the Colusa Basin Drain, Putah and Cache creeks, and agricultural and municipal discharges. The Cache Slough Complex exits the Yolo Bypass via Cache Slough, first connecting to the outlets of Miner and Steamboat Sloughs, before entering the tidal Sacramento River channel near Rio Vista.

The Cache Slough Complex has been identified as an area with great potential for tidal restoration as a result of its connectivity with the Yolo Bypass floodplain, suitable elevations, high turbidity, high primary and secondary productivity, and use by Delta smelt (Hypomesus transpacificus), Chinook salmon (Oncorhynchus tshawytscha), and other native fishes. Both federal and state wildlife agencies consider the Cache Slough Complex to be a prime area to advance habitat conservation to benefit endangered species in the Sacramento-San Joaquin Delta and incorporate improvements to the regional flood management system.

The latest project approved for construction is the Lookout Slough Project, a 3000-acre tidal marsh restoration immediately to the west of Liberty Island. The Project was certified by DWR in 2020 as mitigation/compensation for the Delta Tunnel Project. The Delta Stewardship Council recently denied appeals1 to the state’s certification of the Lookout Slough tidal marsh restoration project. Once completed, Lookout Slough will be the Delta’s largest single tidal habitat restoration project to date.

The Problem

Most of the tidal “restoration projects” in the Cache Slough Complex involve breeching leveed tracts of agricultural land to create subtidal or intertidal habitat. Tidal waters once confined to narrow floodplain channel are now allowed to pour through breaches onto over 10,000 acres of formerly diked farmlands. The process started between 1980 and 2000 when Little Holland Tract (1456 acres) and Liberty Island (4340 acres) levees failed and were not repaired, leaving these lands open to the tides. Because these reclaimed wetlands had subsided during active farming, most of the “restored tidelands” became sub-tidal, year-round, warm, shallow, open-water habitat. Such habitat is too warm for Delta native fishes except during the winter.

The enhanced tidal exchange and warm productive winter and early-spring habitat attracts migratory Delta native fishes like smelt, splittail, and salmon to the Cache Slough Complex. While such habitat is considered beneficial in winter, it warms excessively in spring and summer, reducing the period of quality rearing, and can reduce overall survival and production. Native fishes have succumbed to the heat, stranding in the uneven landforms, and predation by non-native warm-water fish.

The latest projects, Lower Yolo Ranch (1749 acres), Yolo Flyway Farms (300 acres), and Lookout Slough (3000 acres), will add 5000 acres of mostly shallow intertidal habitat. Tidewater will flood onto these lands twice a day to warm in the California sun and then return to cooler deep, shaded, sub-tidal sloughs long considered prime Delta smelt and salmon rearing habitat. Not only will the new inter-tidal “wetlands” be too warm, but they will contribute to warming adjacent sub-tidal sloughs that convey water to and from other parts of the north Delta. This water quality degradation gets worse with each new project and has resulted in the degradation of the entire north Delta as a viable spawning, rearing, and critical habitat of Delta smelt. The effect has measurably contributed to the near extinction of Delta smelt.

The Evidence

The United States Geological Service has many water quality and flow monitoring gages in the Cache Slough Complex (Figure 2) that provide considerable evidence of the above-described problem. Specific gages with pertinent data records reviewed for this post are highlighted in Figure 2.

Waters in the northern Cache Slough Complex become too warm for salmon and smelt (>20ºC) by spring (Figure 3). In summer (Figure 4), water tidally flooded into subtidal island-tracts can warm 5-7ºC over a day before draining back into adjacent sloughs. Water temperatures in the northern sloughs of the Cache Slough Complex reach 25ºC (lethal to smelt) or higher in summer, even in wet and normal water years (2016-2018, Figure 5). Water temperatures in the southern Cache Slough Complex are only slightly lower (Figure 6). Over the past decade, water temperatures in the Cache Slough Complex overall have been gradually increasing (Figures 7 and 8), to the detriment of Delta native fishes.

The Solution

The problem can be lessened or even reversed at existing and future restoration projects by:

  1. Limiting tidal access to sub-tidal sites to winter, when water and air temperatures are colder.
  2. Building projects with flow-through tidal channel features rather than a single opening.
  3. Ensuring that projects are inter-tidal with small, narrow, shaded channels, or tule benches.
  4. Narrowing, deepening, and shading connecting tidal sloughs.
  5. Limiting discharge of warm agricultural wastewater into tidal channels.
  6. Providing supplementary inflow of Sacramento River water from the Fremont Weir, from the entrance gates of the Sacramento Deepwater Shipping Channel, or from other locations.
  7. Retrofitting existing restoration sites and designing future projects as outlined above.

 

Figure 2. USGS gage locations in the Cache Slough Complex.

Figure 3. Water temperatures recorded at Little Holland Tract in 2015-16.

Figure 4. Water temperatures and water surface elevation (gage height) recorded at Little Holland Tract in July 2017. Note higher water temperature spikes occurred with strongest ebb (draining) tides.

Figure 5. Water temperature in Liberty Cut adjacent to Little Holland Tract, 2016-18.

Figure 6. Water temperature and tidally-filtered flow rate in Sacramento Deepwater Ship Channel, April-September 2021.

Figure 7. Water temperature in lower Cache Slough, 2011-2016.

Figure 8. Water temperature in the lower Sacramento River channel near Rio Vista, 2010-2019.

State and Federal Hatcheries Release Salmon Smolts to Rivers, Delta, Bay, and Coast

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Hatcheries in California are releasing tens of millions of salmon smolts in 2022, per normal operations.  State hatcheries are trucking over ten million fall-run salmon to the Bay again this spring because of the drought.  State and federal hatcheries are releasing another ten million-plus fall-run smolts to the rivers near the hatcheries.

Future salmon fisheries will depend mostly on the Bay releases, because few of the hatchery smolts released to the river or wild salmon smolts will survive the journey to the ocean this drought year.  Yet even the prognosis for smolts released to the Bay is poor.  Delta outflows near 4000 cfs under the State’s TUCP will keep survival below one percent (Figure 1).

Meanwhile, the prognosis for wild fall-run smolts under the TUCP is grim as they began moving through the Delta in late April and early May (Figures 2 and 3).  The extra month of normal outflow needed to help the salmon get to the ocean would amount to about 100-150 TAF, less than 10% of what is being supplied to water users from reservoirs in spring 2022.  Is the TUCP allocation to outflow and fish reasonable?

Figure 1. Fall-run salmon adult returns to the American River hatchery from Bay releases vs Delta outflow to Bay at time of release. Years noted are percent returns for below normal years 2016 and 2018, and wet year 2017 under normal rules. Blue dots with outflow below 5000 cfs are from 2014 and 2015, TUCP years. Red line is hypothesized relationship. Returns under normal rules are approximately triple the returns under TUCP rules.

Figure 2. Red circle denotes wild fall-run and spring-run smolts passing through the Delta in late April and early May 2022.

Figure 3. Peak migration of fall-run and spring-run smolts into Bay from Delta in late April and early May 2022.

2022 Sacramento River Operations – Temperature Management Plan

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So much is at stake in this water year 2022: water supplies, water quality, agricultural production, hydropower production, as well as the future of salmon, steelhead, sturgeon, smelt, and other native fishes of the Klamath and Sacramento-San Joaquin watersheds. Despite the lessons of the 1976-1977, 1987-1992, 2007-2009, and 2013-2015 droughts, the choices and tradeoffs are more difficult, and effects more significant and consequential to the fish, in 2022, the third year of the 2020-2022 drought. The State Water Resources Control Board is about to approve 2022 water operation plans for Central Valley Project (CVP) and the State Water Project (SWP). Among the most immediate effects of these plans will be the fate of iconic fisheries resources of the Sacramento and Klamath Rivers, in 2022 and beyond.

The two key elements of the plans are (1) the Sacramento River Temperature Management Plan (TMP) governing Shasta/Trinity operations, and (2) the Temporary Urgency Change Petition (TUCP) governing Delta operations. A 4/5/22 post covered some aspects of the TUCP on Delta operations, which serves to cut demands on federal and state reservoir storage in the Sacramento River watershed by lowering Delta outflow requirements. (See also CSPA and allied organizations’ protest and objection to the TUCP.)

This post covers the 2022 TMP, which focuses on Shasta/Trinity storage releases and management of Shasta Reservoir’s storage releases and cold-water pool in support of Sacramento River salmon. It starts with a review of both the hydrological and biological effects of Shasta and Trinity operations in 2021. Starting with 2021 creates context in two ways. First, it explains the severe depletion of CVP and SWP storage in 2021, which created the avoidable portion of the extreme storage conditions of 2022. Second, it describes the disastrous failure to protect fish in 2021, both as consequence of bad management and contributor to the dire conditions of fisheries in 2022.

2021 Sacramento River Operations

The predominant characteristic of 2021’s operations of Shasta Reservoir and the Sacramento River was excessive reservoir storage releases over the spring and summer for water deliveries. Within this constrained context, the dominant biological features in 2021 were management of the cold-water pool for salmon , along with associated “downstream” effects on the lower river and Bay-Delta. The 2021 Sacramento River operations plan led to significantly reduced production in brood year 2021 of all four runs of Sacramento salmon.

I have divided the 2021 story into five event periods (Figure 1), each with differing conditions and outcomes:

Period A: The early-April through early-June period was characterized by rapidly rising high releases (6000-9000 cfs) for water deliveries in late April and May. Reclamation claimed it saved 300 TAF of Shasta’s cold-water pool using power bypass of warm surface water for the high spring releases. In reality, the excessive delivery of irrigation water unnecessarily depleted total Shasta storage by nearly 500 TAF and depleted the cold-water pool by 200 TAF. Those storage losses also crippled any ability to subsequently sustain the cold-water pool through the summer.

The releases of unseasonably warmer water (56-60ºF) also (as planned) inhibited spawning in the late-April to early-June portion of the winter-run salmon spawning season (about half of the historical season). It also stressed winter-run and spring-run adults in their upper river pre-spawn holding areas. Recent scientific studies suggest that such stress (extended holding and warmer water) may have contributed to thiamine deficiencies in spawners that contributed to poor subsequent fry survival and smolt production. Rapidly rising flows and water temperatures may have also compromised late-fall-run salmon egg incubation that normally continues into April. Irrigation deliveries in the middle and upper river led to lower flows and high water temperatures in the lower river (Figures 2 and 3); this both reduced the survival of emigrating spring smolts of all four races of salmon, and hindered and stressed upstream migrating winter-run and spring-run adults.

Period B: The mid-June period of cold-water releases (53-55ºF) was designed to stimulate winter-run adult spawning. It also provided 8000 cfs irrigation releases that unnecessarily depleted total storage and the cold-water pool by 6-8 TAF per day for nearly two weeks (~100 TAF lost cold-water pool and total storage). It also resulted in salmon spawning at 8000 cfs, spawning habitat conditions that led to water surface elevations that increased by one-foot and then dropped by two-feet over the summer salmon egg incubation season. I have not assessed the role of flow on the amount of quality spawning habitat available or on the potential of redd dewatering/stranding, although such factors should also be considered in evaluating an operations plan. Irrigation deliveries in the middle and upper river led to lower flows and high water temperatures in the lower river (see Figures 2 and 3), hindering and stressing winter-run and spring-run adults that were late in migrating upstream.

Period C: The late-June to early-August period was the main winter-run egg incubation period under 2021 operations. Flow releases increased to accommodate irrigation demands. Irrigation diversions, in turn, reduced flows in the river further downstream, leading to high water temperatures (72-78ºF) that blocked early arriving fall-run adult immigrants. A rise of almost two feet in water level in early June from the increased flow likely caused some redd scouring in the upper river spawning reach below Keswick Dam.

Period D: The mid-August to mid-September period was characterized by falling storage releases, associated declining water levels, and warming water as the cold-water pool and access to it declined. Winter-run egg incubation continued through the period and likely suffered from stressful water temperatures and redd dewatering. Flows in the lower river increased, and water temperatures declined, becoming less stressful for upstream migrating adult fall-run.

Period E: The late-September through November period was characterized by continued warming of water temperatures due to lessening access to Shasta’s severely depleted cold-water pool, followed by natural fall cooling. Releases and water levels declined rapidly in the spawning reach. At the beginning of the period, warm water interrupted or delayed spring-run and fall-run spawning, while a water level drop of several feet led to redd dewatering and stranding. Winter-run fry were also subjected to potential stranding during the drop in water level. Spring-run and fall-run spawning was likely hindered or delayed into November due to high water temperatures and decreasing flows and associated water levels.

The 2022 Plan

The May 2 2022 Final TMP Is a radical change from the 2021 plan and actual operations. For the first time, Reclamation has prioritized protection of fish over irrigation deliveries to senior Sacramento River Settlement Contractors. The changes also reflect the much lower available storage in this third year of drought (Figure 4). Water release projections are much lower to sustain the cold-water pool and cool downstream temperatures through the summer (Tables 1 and 2).

April Operations and Effects

April operations closely followed the draft plan that Reclamation submitted to the State Water Board on April 6. April operations using middle TCD gates and small imports of Trinity River water maintained Keswick releases at 52-53ºC and 3250 cfs per the draft 2022 TMP. Such operation helped preserve Shasta storage and the volume of the deeper, cold-water pool (<50ºF). Valley-wide precipitation since mid-April increased flows in the middle and lower Sacramento River, stimulating juvenile salmon emigration and adult spring-run and winter-run salmon immigration. A small pulse flow from Keswick to the 30 miles of spawning and rearing habitat below Keswick Dam would have helped stimulate and benefit these salmon migrations, especially those from the upper 30-mile reach that saw little or no benefits from the April storms, but this did not occur.

The draft TMP (April 6) had the same proposed releases from Keswick Reservoir as the final TMP (May 2). However, the end-of-September storage in Shasta Reservoir predicted in the final TMP (1135 TAF) is over 100 TAF lower than was the prediction in the draft TMP (1250 TAF).

Proposed May Operations

The proposed May 4500 cfs release would come from Shasta Dam’s middle gates with access to warmer surface water in the lake, thus saving some of the cold-water pool. Such savings would require warmer releases that would delay spawning and stress holding adult winter-run and spring-run salmon.

For those winter-run who do spawn in May, egg survival could be compromised by the warmer water. With warming surface waters and warmer reservoir inflows in May, and more pre-spawn adult salmon arriving in the 10-mile spawning reach below Keswick Dam, a Keswick release temperature maintained at or below 51ºF would ensure the 10-mile spawning and holding reach is maintained near 53ºF. A colder release would require proportionately more cold water be released from deeper dam gates.

In reality, middle gate operation through early May (Figures 5 and 6) has sustained cooler-than-expected daily-average release temperatures at 51-52ºF. Hydropower peaking has accessed the warmer upper layers of the reservoir (Figures 7 and 8), saving some of the cold-water pool as planned. However, middle-gate operation under hydropower peaking, and gradual warming of reservoir surface waters, will result in increasing release temperatures per the plan later in May. A rapidly warming reservoir may necessitate use of lower gates or less hydropower peaking operations to maintain <54ºF through May per the plan. If spawning commences in early May due to cooler than planned dam releases, higher late May release temperatures would begin to compromise earlier-spawned egg survival. This should cause some re-evaluation of the plan.

Proposed June-September Operations

The proposed June-September 4500 cfs release (4000 cfs in September) from Shasta Dam will be from the lower TCD gates from the cold-water pool at ~50ºF (Table 2). Slightly higher Keswick Dam release water temperatures are predicted due to warming in Keswick Reservoir at ~4500 cfs through-flow. Water temperatures 5 miles downstream at Highway 44 will increase slightly more due to warm air temperatures.

The final temperature management strategy, based on recommendations received from the Sacramento River Temperature Task Group (SRTTG), is to target 58ºF at Highway 44 during the initial part of the season and then target 54.5ºF for 16 weeks around the estimated peak spawning date of Aug 2. This would result in targeting 54.5ºF from June 7 through September 27 or until the cold water is used up. Due to the limited available control in operating the middle gates (as described above), temperatures in June and July may be cooler than 54.5ºF. Reclamation will operate the TCD to target as close as possible to 54.5ºF to conserve cold water for maintaining target temperatures throughout the critical period.

Reclamation also received feedback from SRTTG members that an initial target of 58ºF would help to conserve cold water for later during the more critical portion of the temperature management season. The problem with this is that it will delay spawning, stressing yet-to-spawn adults and compromising survival of earlier-spawned embryos.

Fall Operations

Fall operations will be similar to those described above for Period E in 2021, with the exception of a lesser drop in flow. Water temperatures in late summer and fall will increase as the cold-water pool is depleted and access to it ends. Increasing temperatures will delay spring-run and fall-run spawning and stress pre-spawn adults (potentially aggravating the thiamine deficiency problem).

Uncertainties

The planners have noted significant uncertainties that will require intensive real-time operations and management throughout the summer to achieve the various goals and targets throughout the system. To address uncertainty, Reclamation has employed conservative estimates of future conditions in the modeling assumptions (e.g., hydrology, operations, and meteorology) and projections, and has included as part of the TMP the potential to make changes, in consultation with the SRTTG, Water Operations Management Team, and/or the Shasta Planning Group. The State Board and NMFS should be included in the decision process.

Infrastructure limitations

The 2022 TMP was developed in consideration of the limitations on using the TCD and the need for temperatures below 56ºF at the Livingston Stone National Fish Hatchery. Efforts to address these limitations should be accelerated. Hydropower peaking operations changes should also be considered.

Related Actions to the Final 2022 TMP

1. Six-Fold Increase in Winter-Run Hatchery Smolt Production
Reclamation plans to fund a six-fold increase in the production of hatchery winter-run smolts this year with staged fall-winter releases from the hatchery and Battle Creek. Such releases should timed to coincide with natural flow pulses and pulse flows from Keswick Dam.

2. Transfers of Adult Salmon
The plan includes the capture and transport of adult winter-run salmon to the headwaters of Battle Creek. Good additional measures would be to give these adult fish thiamine injections and to enhance spawning gravels in Battle Creek as soon as possible.

3. Thiamine Treatments
Stresses imposed prior to spawning (e.g., delayed spawning, low flows, warm water during migration) and holding contributes to thiamine deficiency and high mortality of yolk sac fry, both in hatcheries and wild salmon1. Only hatchery salmon can be treated effectively at adult or egg stage, so efforts should be made to treat any wild adults that are handled, as well as to minimize pre-spawning stresses (e.g., erratic flows and high water temperatures).

4. Water delivery cut to 18% to Settlement Contractors
The TMP proposes to limit water deliveries to Sacramento River Settlement Contractors to 18% of their contracted amounts. The State Board should enforce this limitation. Reclamation should subordinate the timing of water releases to contractors to the needs of salmon downstream of Keswick Dam.

5. Reduced Downstream Deliveries
Demand on Shasta storage for Delta inflow/outflow has been reduced by relying more on other SWP/CVP and non-project reservoirs. However, lower Sacramento River and Delta inflows have reached water temperatures above 65ºF in early May, which puts additional stress on salmon that are immigrating in late spring. It is not a question of whether in May or June lower river water temperatures will exceed 68ºF – the state standard – but when.

6. System-Wide Water Management
Reclamation plans to manage system water supplies to minimize demands on Shasta’s cold-water supply. The Plan and temperature modeling relies on numerous drought actions throughout the Sacramento watershed to reduce reliance on stored water from CVP and SWP reservoirs this summer. “These drought actions have added a degree of flexibility to manage storage at Shasta, Oroville and Folsom reservoirs for meeting public health and safety needs, repelling salinity in the Delta, producing hydropower and providing additional cold water for fishery protection throughout the summer.” In 2022, Reclamation has finally cut deliveries to Sacramento River Settlement Contractors substantially below minimum amounts stated in contracts, in order to protect salmon. However, DWR has not done so for Feather River Settlement Contractors. Reclamation and DWR should be looking at system-wide delivery reductions. Reclamation should also call on New Melones for Delta salinity control as needed. See also NRDC et al. Objection to the TMP (May 6, 2022) for additional recommended system measures.

7. Real-Time Adjustments and Reporting
“Daily releases may vary from these flows to adjust for real-time operations. Significant uncertainties exist within the forecast that will require intensive real-time operations management throughout the summer to achieve the various goals and targets throughout the system.” Reporting, scrutiny, and decision making should be open processes.

8. Restoration of Salmon Upstream of Dams
Reclamation is committed to restoring endangered salmon to their historical habitat upstream of Central Valley rim dams. This program should be accelerated.

Tables 1 and 2 are copied directly from the Final TMP dated May 2, 2022.

Figure 1. Keswick Dam release water release rate and temperature, April-November 2021. Five general periods (A-E) are depicted, based on flow-temperature conditions as described in more detail in text. A. Spring high storage release rate (6-9K cfs), including extensive power bypass releases of warm surface water. B. A late-June cold water release to stimulate winter-run salmon spawning (<53ºF). C. A post-spawn higher irrigation release period with late-egg-stage sustaining water temperatures. D. Cold-water pool saving period with falling flows and higher water temperatures. E. Early fall period with loss of access to cold-water pool and reduction in storage releases.

Figure 2. April-December 2021 Sacramento River flow below Keswick Dam (river mile 300) and below Wilkins Slough (river mile 120). The difference between the two locations, plus tributary and ag return inputs, equals total irrigation deliveries via surface diversions and ground water depletions.

Figure 3. Water temperature in the lower Sacramento River at Wilkins Slough (river mile 120) May-August 2021, along with average for past 13 years. Note that the state’s year-round water quality standard for the lower Sacramento River is for water temperature to remain below 68ºF. Water temperatures above 65ºF are stressful to migrating juvenile and adult salmon. Water temperatures above 70ºF hinder adult salmon migration. Water temperatures above 75ºF are lethal to salmon.

Figure 4. Shasta Reservoir storage in 2022 and other selected years.

Figure 5. Shasta Reservoir water temperature profile at end of April 2022.

Figure 6. Water temperatures of Shasta and Keswick Dam releases in 2021 and to date in 2022.

Figure 7. Hourly water temperature in Shasta Dam releases, 4/27-5/7 2022.

Figure 8. Hourly Shasta Dam flow releases 4/27-5/7 2022.

  1. Adult salmon thiamine stores reduce most during the pre-spawning fast (Vuorinen et al. 2020).  Vuorinen PJ, Rokka M, Ritvanen T, Käkelä R, Nikonen S, Pakarinen T, Keinänen M. 2020. Changes in thiamine concentrations, fatty acid composition, and some other lipid-related biochemical indices in Baltic Sea Atlantic salmon (Salmo salar) during the spawning run and pre-spawning fasting. Helgol Mar Res. 74(1):1–24. doi:https://doi.org/10.1186/s10152-020-00542-9. (Crossref), (Web of Science ®), (Google Scholar) https://hmr.biomedcentral.com/articles/10.1186/s10152-020-00542-9 ↩

Water Projects’ Temporary Urgent Change Petition 3/18/22 Comment on Provision #1 – Spring (April-June) Delta Outflow and Salinity Intrusion

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The U.S. Bureau of Reclamation and the California Department of Water Resources (Reclamation and DWR) filed a “Temporary Urgency Change Petition” (TUCP) on March 18, 2020.  If granted, the TUCP reduce Delta outflow requirements.  The proposed averaging requirements in the TUCP pose a problem in addition to the problem of too little overall outflow.

The TUCP states:

Reclamation and DWR are requesting to modify certain terms as the Projects’ storage and inflow may not be sufficient to meet D-1641 requirements and additional operational flexibility of the Projects is needed to support Reclamation and DWR’s priorities, which include: operating the Projects to provide for minimum health and safety supplies (defined as minimum demands of water contractors for domestic supply, fire protection, or sanitation during the year); preserve upstream storage for release later in the summer to control saltwater intrusion into the Sacramento-San Joaquin Delta (Delta); preserve cold water in Shasta Lake and other reservoirs to manage river temperatures for various runs of Chinook salmon and steelhead; maintain protections for State and federally endangered and threatened species and other fish and wildlife resources; and meet other critical water supply needs. (3/18/22 TUCP, p. 1)

The TUCP is requesting reduced Delta outflow requirements for the April 1 through June 30, 2022 period, for the stated primary purpose of preserving storage in Oroville and Folsom reservoirs.   What I term Provision #1 is reduction of outflow requirement from 3-day average of 7,6001 to 14-day average of 4,000 cubic feet per second (cfs).

The requirement in Revised Water Rights Decision 1641 of a 3-day average of 7,600 cfs is meant to keep salt water from encroaching upstream from the Bay into the Delta in drought years like 2021 and 2022.   This helps to protect the beneficial uses in the Delta including fish, fish low-salinity habitat, Delta agriculture, and south Delta water export water quality.  The TUCP’s proposed Delta outflow of 4000 cfs is meant to provide minimum protection in the face of low available water supply (reservoir storage and precipitation).

The overriding problem with the TUCP’s proposed flow reduction is that it does not require enough flow.  Yet, even accepting the need to reduce flow to allow storage of more water in Reclamation and DWR’s reservoirs, the requested change could be modified to better protect beneficial uses.

Under past TUCPs, DWR and Reclamation have used the 14-day averaging window to game operations to skate as closely as possible to the edge of compliance.  This has led to erratic outflows, often below 4000 cfs (Figure 1).  More precise estimates taking into account tides show outflow is lower than intended (Figure 2).  In these circumstances, salinity has increasingly moved up from the Bay into the Delta under such minimum freshwater outflow (Figures 3-6).

I recommend the outflow required be more stable, allowing for only minimal salinity increase over the spring.  A 3-day average of 4,000 cfs measured outflow would provide greater protection of beneficial uses.

Salinity criteria are more easily defined and measured, and more directly related to beneficial uses.  Criteria for Collinsville, Emmaton, Jersey Point, and Old River that have a maximum for a 3-day average or a maximum daily level with a minimum increase over the spring would also be more protective.

Figure 1. Daily Delta outflow estimated from measured Delta hydrology conditions in spring 2014, 2015, and 2021, drought years when previous TUCPs were implemented

Figure 2. Measured Delta outflow into Suisun Bay in spring 2021.

Figure 3. Salinity in eastern Suisun Bay in spring 2021.

igure 4. Salinity in lower end of Sacramento River near Rio Vista in late April 2021.

Figure 5. Salinity and net tidal flow in lower San Joaquin River channel at Jersey Point in spring 2021.

Figure 6. Salinity (EC) and net tidal flow in lower Old River channel in south Delta near Byron in spring 2021.

  1. The normal requirements are stated in Revised Water Rights Decision 1641, Table 3, footnote 10, pp. 185-186.  The April-June requirement in a Critically Dry year is also met if either the daily average or 14-day running average EC (measurement of salinity) at the confluence of the Sacramento and the San Joaquin rivers is less than or equal to 2.64 mmhos/cm (Collinsville station C2).  From May 1 through June 30, if the Sacramento River Index is less than 8.1 million acre-feet, the flows requested in the TUCP would be the same as the required flows under Decision 1641. ↩

Salmon Released from Central Valley Hatcheries

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Hundreds of thousands of smolts of endangered salmon are being released to the lower Sacramento River from federal and state hatcheries this winter, the San Francisco Chronicle reported on March 2.1 It is a drought year, and most of the young salmon will likely perish in the jaws of predators on their 300-mile journey to the ocean through the river, Delta, and Bay. Without the protection of adequate river flow, cold water, and turbidity for the journey, there is little hope. Reservoir storage is depleted from the past two years of overzealous water deliveries. What little rain and snowmelt there has been in the Valley is being stored in reservoirs. Warm weather has come early. The 400 thousand smolts released on March 2 could use some help, but they have not received it and are not likely to get it.

River Flow

Flow from Shasta Reservoir to the upper river via Keswick Dam has been minimal (Figure 1, KWK). 40 miles downstream at the Bend (BND) gage near Red Bluff, the river received some snowmelt from tributaries in January, but even that tapered off by the end of January. Flow into the Delta from the Sacramento Valley at Freeport (FPT) reached minimal levels by the end of January. Delta outflow (Figure 2) settled at its minimal prescribed level near 12,000 cfs after some January export taking.

Water Temperature

Warm weather and low flows have allowed water temperatures in the lower Sacramento River and north Delta migration corridor to reach the mid-fifties (Figure 3), temperatures that activate lower river predators like striped bass, resident trout, and pikeminnow.

Turbidity

Turbidities (Figure 4) are now at seasonal lows from the upper river near Red Bluff (RDB) to the Delta near the Rio Vista Bridge (RVB), reflecting clear waters needed by sight-feeding predators like striped bass.

Delta Salmon Salvage

Hatchery salmon smolts released in December at least reached the Delta during the December storms (Figure 5). It remains to be seen if the February and March smolt releases even reach the Delta.

What’s Needed

The article in the Chronicle mentioned that only one of the 140 radio-tagged hatchery smolts released in February has reached the Delta. The March 2 release of 400,000 smolts could use a pulse of cold turbid water from Shasta, Oroville and Folsom reservoirs to help them reach the Bay. So far, only Oroville releases have increased, from 3500 to 5500 cfs in recent days, with the added 2000 cfs showing at Freeport (Figure 1). While this helps near the Delta, it does little for the upper 200 miles of river the smolts have yet to transit.

Figure 1. River flows near Keswick (River Mile-RM 300), Bend (RM 250), and Freeport (RM 50) in winter 2022.

Figure 2. Delta outflow in tidally averaged daily cfs in winter 2022.

Figure 3. Water temperature in Sacramento River near Bend (RM 250), Wilkins Slough (RM 140) and Freeport (RM 50) in winter 2022.

Figure 4. Water turbidity in Sacramento River near Bend (RM 250), Red Bluff (RM 240), Freeport (RM 50), and Rio Vista (RM 30) in winter 2022.

Figure 5. Salmon salvage observed at Delta Fish Facilities in water year 2022.