Scott-Shasta River Salmon Update – February 2024

The upper Scott River near Callahan in early spring of drought year 2013.

At the end of November 2023, the Beaver Moon, the last full moon before December, appeared. The Beaver Moon was so named because it was the last chance for trappers to catch beaver with full coats before winter set in. The Beaver Moon also occurs at the peak of the Coho and Chinook salmon runs in the Scott River Valley, once named Beaver Valley. The beaver were once very abundant before being “removed” by ranchers and trappers. Today, beaver are slowly coming back. The beaver help maintain the local groundwater tables, streamflow, water temperatures, riparian vegetation, and create good coho salmon rearing habitat.1

The State Water Resources Control Board took up the Scott and Shasta Rivers water issues again in fall 2023,2 following its adoption of emergency drought regulations in 2022 and a 2023 petition from the Karuk Tribe and environmental organizations3 to protect salmon and steelhead in the Scott river in all water years.

The emergency regulations for 2022 called for summer minimum flows of 30-50 cfs in the Scott River and 50 cfs in the Shasta River. Such minimums were not achieved on the Scott River (Figure 1), but for the most part were achieved on the Shasta River (Figure 2). Such flows were necessary for two key flow functions: (1) maintaining connectivity between spawning and rearing areas in the valleys and the Klamath River, and (2) sustaining over-summering rearing habitat of salmon and steelhead throughout the two rivers and their tributaries.

Without adequate summer flows, salmon fry become trapped in upstream spawning areas without access to productive spring-fed Valley rearing habitat. Maintaining flow in Valley spring-fed habitats provides connectivity and rearing refuges. Late summer and fall minimum flows are necessary to provide access to the valleys from the Klamath River canyon for salmon and steelhead adult spawners.

The State Board should have kept some emergency order elements in place after the orders ended in July 2023, even though 2023 was a wet year. In 2023, both rivers and their salmon were stressed again by low flows (Figures 3 and 4).

Because base flows from mountain and valley springs are just over 100 cfs in both streams, stressful conditions are brought on by the cumulative effects of small water diversions and groundwater pumping. Surface water diversions and groundwater extraction for agricultural and domestic water use draw from this supply, with peak use in the summer-fall irrigation season. On the Shasta River, the irrigation season ends at the beginning of October, allowing flows from springs to fill the river channel for returning salmon. On the Scott River, the irrigation season extends through November to water pastures and to get in the last crop of hay.

In the Shasta River, flows in October are sufficient for Chinook spawners passage to spawning areas around Big Springs in Shasta Valley. But in the Scott Valley, Chinook often do not have adequate passage flows to ascend from the Klamath Canyon up to Scott Valley until the first late-fall rains. In most years, early December rains accommodate the Coho run in the Scott River. Young salmon from the prior year’s spawning also need the fall flows to emigrate from the Valley to the Klamath River and ocean.

2023 Karuk et. al. Petition for Scott River4

On May 22, 2023, the Karuk Tribe, Environmental Law Foundation, Pacific Coast Federation of Fishermen’s Association, and Institute for Fisheries Research petitioned the State Water Board to initiate a rulemaking to establish permanent (not just emergency) instream flows on the Scott River.

As an initial response, the State Water Board re-adopted, on an emergency basis, the emergency minimum instream flows previously in effect in both the Scott River and Shasta River.

Comment: The State Board did not readopt the emergency regulations in wet year 2023 and the salmon suffered.

2024 Coastkeeper et al. Petition for Shasta River

On January 17, 2024, California Coastkeeper Alliance, Friends of the Shasta River, Mt. Shasta Bioregional Ecology Center, Water Climate Trust, Shasta Waterkeeper, Save California Salmon, and Environmental Protection Information Center petitioned the State Water Board to initiate a rulemaking to establish permanent (not just emergency) instream flows on the Shasta River.

Recommendations

As an initial matter, the State Water Board should adopt as permanent the minimum instream flows it adopted on February 1, 2024 as emergency instream flows.5 This will put an immediate end to dry streambeds in the summer and fall as shown in Figures 3-5 below. This will admittedly also significantly reduce water available for human use and cause a conflict between groundwater and surface water users, as well as among water right holders.

In the longer term, there are some relatively straightforward additional measures that could help create solutions to the problems in Scott and Shasta Valleys and potentially reduce the water supply impacts. Whether these actions are equitable, reasonable, cost-effective, and/or politically doable is open to question and evaluation. The adoption of the flow requirements as shown must not be contingent on the implementation or effectiveness of such actions.

Possible additional measures include:

  1. Create additional instream or off-stream storage to capture winter water for summer release to meet demands and needs.
  2. Make concerted efforts to recharge groundwater storage with the often-plentiful winter-spring runoff.
  3. Deepen the river channel by removing accumulated fine and course sediments to enhance channel access to groundwater. Removing Young’s Dam in the middle Scott Valley would deepen channel upstream and alleviate the dam’s impediment to salmon and steelhead migration.
  4. Eliminate all surface water diversions from stream channels. There are many small water diversions from the Scott and Shasta rivers that divert streamflow and juvenile salmon. Surface diversions should be replaced by a regulated groundwater extraction program.

     Small water diversion on a Scott River tributary. All small and larger surface diversions should be eliminated. The present system was controlled by the state watermaster program that no longer covers the Scott River and its tributaries.

    Small water diversion on a Scott River tributary. All small and larger surface diversions should be eliminated. The present system was controlled by the state watermaster program that no longer covers the Scott River and its tributaries.

  5. Use unused well capacity to temporarily augment surface water flow in the streams in late summer to help with salmon migrations and to accommodate spawners. In Scott Valley, many hay producers cease pumping from wells at the beginning of August or September. A monitoring and evaluation program would be required to avoid long-term impacts to groundwater levels. The target flow in both the Scott River and Shasta River should be near 100 cfs by October 1 at the Fort Jones and Yreka gages, respectively.
  6. Enhance and restore water storage in mountain and valley meadows through watershed management, including introductions of beaver.
  7. Institute an aggressive water conservation program in the two watersheds.

Latest Actions

 The petitioners requested the following:

Drought emergency minimum flows are specified below:

 Scott River:

  Shasta River:

 The State unveiled the California Salmon Strategy for a Hotter, Drier Future:  Restoring Aquatic Ecosystems in the Age of Climate Change on January 31, 2024.  The Strategy describes state actions for the Scott and Shasta rivers, as follows:

 Scott/Shasta:

  • Designate Salmon Strongholds: the Klamath River and its tributaries including the Salmon, Scott, and Shasta rivers.
  • In April 2023, CDFW awarded $20 million in Drought Emergency Salmon Protection Grants to 10 projects demonstrating support from and collaboration with Tribal Nations and landowner interests in the Shasta and Scott rivers and their watersheds. These include habitat improvement, removal of barriers to fish passage, and groundwater recharge projects that help ensure streamflow.
  • The State Water Board, acting upon a petition from the Karuk Tribe, began consideration of an emergency regulation in 2023 to set emergency minimum flows for the Scott and Shasta rivers while a longer, inclusive process evaluates long-term strategies for these salmon strongholds.
  • By early 2024, commence work to establish minimum instream flows in the Scott and Shasta Rivers, working with local partners on locally driven solutions and coordinating on options for incentivizing the reduction of diversions and groundwater pumping. (SWRCB, CDFW)
  • Currently, with state funding support, the Yurok Tribe, the Karuk Tribe, California Trout, Scott River Water Trust, and Farmers Ditch Company are developing a design-build project to restore habitat in the Scott River and improve water diversion infrastructure for on-farm water utilization and efficiency.

 For more on the Scott River issues see: https://calsport.org/fisheriesblog/?p=1608 .

Figure 1. Scott River streamflow in 2021 and 2022 at Fort Jones gage. Note the end of the irrigation season in November-December. Note also prescribed emergency flows were not met in 2022.

Figure 2. Shasta River summer 2021 and 2022 streamflow at the Yreka gage. Note the end of the irrigation season on October 1st. Note also prescribed emergency flows were met in 2022 with the exception of about a one-week period in August.

Figure 3. Scott River streamflow in summer-fall 2023 at Fort Jones gage. Note the July 2023 flow reduction when the emergency flow regulations ended. Note also the end of the irrigation season on December 1st.

Figure 4. Shasta River summer 2023 streamflow at the Yreka gage. Note the July 2023 flow reduction when the emergency flow regulations ended. Note also the end of the irrigation season on October 1st.

Figure 5. Scott River in Scott Valley in August 2013. The riverbed is perched above the water table that was low due to groundwater extraction for hay and pasture watering.

Figure 6. Lower Valley location of Scott River at the mouth of Shackleford Creek, a major salmon spawning tributary, on October 26, 2013.

Figure 7. Young’s Dam and fish ladder. Portions of the dewatered Scott Valley stream are located in the perched channel upstream of Young’s Dam. Under low late-summer streamflows, the ladder at Young’s Dam is not functional and blocks the Chinook migration. The channel upstream of the dam is wide and perched above the water table, so it is often too warm, with insufficient flow and cover, for rearing salmon. In contrast, the channel below the dam is deep and shaded with spring-fed juvenile salmon refugia.

  1. Beaver dams sometimes block salmon migrations.  In Alaska, biologists sometimes resort to blowing up dams with dynamite.  On the Yuba River near Brownsville, biologists in recent decades had to “dismantle” some dams to allow salmon access to tributary creek spawning habitat.
  2. https://www.times-standard.com/2023/08/22/minimum-flows-set-for-scott-river-in-state-water-board-meeting/
  3. https://www.waterboards.ca.gov/drought/scott_shasta_rivers/docs/2023/petition-minimum-flows.pdf
  4. https://www.waterboards.ca.gov/waterrights/water_issues/programs/drought/scott_shasta_rivers/docs/2022/klamath-reg-2022.pdf
  5. State Water Board, Emergency Regulation Scott River & Shasta River Watershed, February 1, 2024:  https://www.waterboards.ca.gov/drought/scott_shasta_rivers/docs/2024/scott-shasta-reg-oal-approval-2024.pdf.

Why Does the Mokelumne River Hatchery Have a Record Salmon Run this Fall 2023 when Runs at the Battle Creek (Coleman) Fish Hatchery Are at Record Lows?

Water Year 2023 (10/1/22-9/30/23) in the Central Valley was very wet, with exceptional hydrology. With the state’s salmon fishery closed and plentiful water there had been some optimism for the 2023 salmon runs. But there was also concern as to how much this year’s salmon runs would be affected by the poor water years 2020-2022.

The Mokelumne River system is achieving hoped-for outcomes from its salmon management. Over 20,000 salmon adult salmon have been counted moving upstream past the Woodbridge counting facility. The counting facility on Battle Creek has counted only about 5,000 salmon, in a system whose adult return are generally far greater than those on the Mokelumne. What happened?

  1. Reasons for Strong Run in Mokelumne River – News reports and interviews with hatchery managers indicate a record high escapement of fall-run salmon to the Mokelumne River and hatchery. Factors that likely contributed to the strong run include the following:
    1. Of the 21 million fall-run smolts produced and released by the Mokelumne Hatchery during drought years 2020-2022, about half were released to coastal harbors and half released to Sherman Island sites on the lower San Joaquin River channel in the Delta (Table 1). These releases likely made up the vast majority of Mokelumne River returns in 2023 of age 2-4 adult returns.1 Past survival rates for such coastal and Delta releases are among the highest for Central Valley hatchery fall-run salmon smolt releases. Coastal releases regularly have survival rates 5 times the rates of the Delta releases and 10 or more times the rates of Mokelumne River in-river releases. No releases were made to the Mokelumne River below the hatchery from 2020-2022. Straying rates of adults returning from the Mokelumne Hatchery off-site smolt releases often exceed 50%, with most going to the American River and lesser amount returning to the Feather and Merced rivers. Strays from hatcheries on those rivers also return to the Mokelumne River.
      b. The Mokelumne River has prescribed summer-fall attraction flows for fall-run salmon (Figure 1). However small in magnitude, they seem to attract adult salmon.

  2. Reasons for Poor Winter-Run and Fall-Run Salmon Runs in Upper Mainstem Sacramento River and Battle CreekNews reports and hatchery news releases indicate a very low run for salmon in Battle Creek and the upper Sacramento River in 2023.
    1. a. All hatchery smolt releases from the Coleman Fish Hatchery on Battle Creek and the Livingston Stone Fish Hatchery on the Sacramento River in Redding in 2020-2022 were to the upper river near the two hatcheries. In prior years, survival was low for river releases in drought years and higher for Bay-Delta releases (Table 2).
    2. River conditions in the Sacramento River are generally poor (high water temperatures and low flows) in drought years like 2021 for late winter and early spring hatchery releases and wild salmon emigration. Overall outmigration success in every year but one has been poor since 2008, and is trending downward (Figure 2). However, in late winter and early spring 2021, a natural flow pulse occurred in the upper river that helped move the hatchery and wild smolts downstream (Figures 3 and 4).
    3. Water temperatures in the lower reaches of the Sacramento River were high when adult salmon were migrating upstream towards the upper Sacramento River and Battle Creek (and hatchery) (Figure 5).

Table 1. Tag groups of Mokelumne Hatchery fall-run smolts released in spring by location in 2020-2022 (brood years 2019-2021).

Figure 1. Streamflow of lower Mokelumne River at Woodbridge gage in water years 2020-2022 and long term average. Note October attraction flows and winter pulse flows.

Table 2. Survival table for selected winter-run and fall-run smolt release groups from the Livingston Stone Hatchery and Coleman Hatchery during critical drought years 2009, 2044, 2015 and normal year 2016.

Figure 2. Broodyear index for juvenile fall-run salmon catch in the lower Sacramento River at Knights Landing rotary screw trap 2008-2023. Source

Figure 3. Water temperature and streamflow in the lower Sacramento River at Wilkins Slough in March-April 2021. Red outline is period of (upstream) Coleman Hatchery smolt releases.

 

Figure 4. Tisdale screw trap collections of winter-run smolts in the lower Sacramento River in fall-winter of water year 2021. Source

Figure 5. Water temperatures in the lower Sacramento River at Wilkins Slough and Freeport during adult salmon immigration period in 2023. Green line represents safe level for adult migration. Yellow line is stress level and water quality standard. Red line is high stress and avoidance level.

  1. Only partial 2020-2022 returns have been recorded for broodyear 2019 releases on the RIMS code-wire-tag database. Two-year old returns appear complete and show over 50% of returns to river-hatchery escapement was to the American River, particularly Nimbus Hatchery.

Hunter’s Moon – Action Needed to Save Central Valley Salmon

October has just ended, and the spawning of spring-run Chinook salmon should be nearing completion.  The winter-run have already finished spawning, and their eggs are now hatching.  The fall-run salmon are in the rivers and beginning their spawning on the Hunter’s Moon.  The fall-run are often neglected after the two endangered runs are complete.  There are actions needed now to protect this biggest and most important run.  After all, the California Fish and Game Commission sacrificed the commercial and sport salmon fishing this year to let the fall-run recover from record lows.

The first signs of trouble in 2023 came with the the low number of returning Central Valley spring-run Chinook Salmon this year.  The decline was indicative of a sudden drastic collapse in all the salmon runs around the Central Valley.

In the northern Sacramento Valley, there are the Clear Creek and Battle Creek spring-run populations.  In the middle Sacramento Valley, there are the Mill and Deer Creeks populations with their remnant counterparts in nearby Big Chico and Antelope Creeks.  There is also the relatively robust (until 2023) Butte Creek population.  Then there is the Feather-Yuba population in the lower Sacramento Valley.  Finally, there is the new population being restored in the upper San Joaquin River near Fresno.  An October 11, 2023 joint news release from NMFS and CDFW describes the numbers of returning spring-run this year as drastically low, to the point that fishery agencies have begun capturing the wild yearlings still residing in the spawning creeks and transporting them to a UC Davis conservation hatchery to preserve the species.

An immediate need is to focus attention on the fall-run Chinook that normally pour into the rivers and begin spawning with the Hunter’s Moon.  Water year 2023 was a wet year, and salmon fishing has been closed in anticipation of predicted low numbers in this year’s spawning run.  It turns out drought years 2021 and 2022 had worse-than-predicted effects on the Valley salmon.

The news release from NMFS and CDFW says, “While other year-classes (or cohorts) will return in coming years, the 2019-2022 drought impacted multiple cohorts, increasing risks for extirpation.”  Actually, 2019 was a wet year and 2020 was a below-normal water year.  It is brood-years 2020, 2021, 2022, and now 2023, that the 2021-2022 drought damaged from many different directions.  Looking ahead, there is a bad forecast for the coming years.  Poor brood years 2020-2023 will lead to poor brood years in 2024-2027, and so on, unless we pay attention now to this year’s fall run.

The Actions Needed Now – Starting the First of November:

1. An intensive monitoring program to assess the damage.

2. Remaining wild and hatchery salmon need maximum protection – this includes a temporary conservation hatchery.

3. This year’s production, no matter how minuscule, must be protected. A substantial portion of the juveniles should be rescued and preserved.  If water year 2024 turns dry this winter, fry, fingerling, and pre-smolt salmon from all races should be captured and eventually transported to the Bay unless significant strategic, coordinated flow pulses can be provided or occur naturally.

4. All hatchery smolts should have at least an adipose fin-clip mark. As many as possible should be released to the Bay or coast for maximum survival.  The marks will be important to differentiate between hatchery and natural-born salmon in the coming years.

5. At locations where migrating adult spring-run salmon potentially originating from Clear, Battle, Mill, Deer, and Butte creeks are clearly stuck or off-course during fall-winter-spring of water year 2024, and where it is possible to collect them, fish agencies should attempt to capture them and return them to their natal stream or to the conservation hatchery. Locations include weirs, dams, ladders, or traps, as well as hatcheries.  This will require Genetic Stock Identification (GSI).

6. Juvenile salmon salvaged at south Delta export facilities this winter and spring should be handled as follows: pre-smolt and smolt salmon should be transported to Golden Gate pens for release. Salvaged fry and fingerlings should be hatchery reared or pen reared to smolt size for eventual pen release at the Golden Gate.

7. The fish agencies and water managers must provide prescribed streamflows and water temperatures in spawning streams and in rearing and migratory reaches. They should not even consider Temporary Urgency Change Petitions for water supply.  Given the current storage in reservoirs across the state, they should prioritize fall and winter flows for salmon over reservoir storage.

8. Fall-run salmon hatcheries will be short of eggs this year. Some hatcheries may need to ship eggs to other hatcheries.  The American River Fish Hatchery in the past sorted adult strays from the Coleman Hatchery on Battle Creek and transported their eggs back to Coleman.

9. Hatcheries should increase the proportion of smolt production trucked to the Bay or coast, where survival rates are up to ten times higher than river releases.

Site-Specific Actions:

10. Yuba River – In the lower Yuba River downstream from Englebright Dam to Marysville streamflow should be immediately increased for spawning and incubation.  Target minimum streamflow should be at least 700 cfs from Englebright Dam to Marysville gage – through spring.

Chart of New Bullards Bar Reservoir

Figure 1. New Bullards Bar Reservoir has never been fuller at this time of year.

11. American River – Water temperatures should be lowered to 55oF to protect spawning salmon in this fall’s spawning season. This will require greater power bypass releases from the reservoir as begun in mid-October (Figure 2).  Folsom Reservoir is also “full.”

12. Upper Sacramento River – Streamflow should be maintained at a minimum of 7000 cfs (Figure 3) through the fall-winter-spring at Bend Bridge gage to provide good spawning, rearing, and emigrating conditions for salmon. Shasta Reservoir is also “full.”

13. Deer and Mill creeks – Streamflow from February through May should be maintained at a minimum of 100 cfs or higher to provide a clear migration corridor with water temperatures in the optimal range. Diversions should be disallowed when flows drop below 100 cfs in these months.

14. Butte Creek – Streamflow from February through May should be maintained to conform with the recommendations in the 2017 Draft Instream Flow Regime Recommendations Butte Creek.

15. Lower river migration corridors to and through the Delta – Water temperatures in winter and spring should be maintained below 60-65oF (see Figure 4), the lower the better. Striped bass still eat a lot of salmon at 65o

In conclusion, it is time for action.

chart of Water temperature in the lower American River at Watt Ave gage in September-October 2023 and 6-year average.

Figure 2. Water temperature in the lower American River at Watt Ave gage in September-October 2023 and 6-year average. Water temperatures need to be 55F by November 1. They should have been no higher than 60F in October.

Chart of streamflow in the upper Sacramento River at Bend Bridge gage in September-October 2023 and 59-year average.

Figure 3. Streamflow in the upper Sacramento River at Bend Bridge gage in September-October 2023 and 59-year average. Flows should be maintained near 7000 cfs through the fall.

Chart of water temperatures in spawning areas: Feather River at Gridley (GRL), Sacramento River from Keswick Dam (KWK) to Bend (BND), Stanislaus River at Ripon (RPN), American River at Watt Bridge (AWB), and Clear Creek at IGO (IGO).

Figure 4. Water temperatures in spawning areas should be below 55oF, while rearing and migration corridors should be below 60oF through spring. Spawning reaches include Feather River at Gridley (GRL), Sacramento River from Keswick Dam (KWK) to Bend (BND), Stanislaus River at Ripon (RPN), American River at Watt Bridge (AWB), and Clear Creek at IGO (IGO). Migration and rearing corridors include lower San Joaquin River at Mossdale (MSD), upper Sacramento River at Red Bluff (RDB), lower Sacramento River at Wilkins Slough (WLK) and Freeport (FPT). Blue dotted line is spawning temperature limit. Red dotted line is rearing and migration limit.

American River Salmon – Fall 2023

It is early October 2023, and the fall-run salmon are running.  The California Department of Fish and Wildlife expects to open the ladder to the American River Hatchery on or about November 1.  There are already salmon in the lower American River from its mouth all the way to Nimbus Dam.

The run expected this year has a mixed forecast.  There was no ocean or river salmon fishery this year because of poor runs in the Central Valley during the 2020-2022 drought.  The fact that fishing was not allowed will improve the 2023 run size (escapement).  The 2020 run (parents of this year’s run) was pretty good (Figure 1).  But when brood year 2020 was rearing and migrating to the ocean, it was a critical drought year 2021, conditions under which juvenile salmon almost always have poor success in making the journey from rivers to the ocean.

Conditions in 2023 have been a mixed bag for the migration of adult spawners from the Bay to Central Valley rivers.  Summer 2023 started with warm water and low flows.  That changed when the Fall X2 requirement kicked in September (Figure 2).  The September Fall X2 flow pulse helped cool the lower Sacramento River and the Bay-Delta (Figure 3), and provided attraction flows for the adult salmon to move into the Bay and on toward the rivers.

An unforeseen problem has faced the running salmon when they hit the north Delta and mouth of the American River: water temperatures have been stressful for migrating adult salmon (>65oF, Figure 4) despite high flows (3000 cfs) from the American River.  The water quality standard for the lower American River requires water temperatures to be maintained <65oF in summer.  But water temperatures rose through September, with continuing increased water temperatures of water released from Folsom Reservoir (Figure 5).  Water year 2023 was a very wet year with above-average reservoir storage.  So why was the American River so warm?

The answer is that the powerhouse intakes at Folsom Dam had limited access to the cold-water pool, and the supply of accessible cold water was running short.  To ensure colder water for the hatchery and river for the November spawn, the Bureau of Reclamation began operating the powerhouse intakes in September to draw warmer water from the surface layers of the reservoir as the reservoir slowly drained.

The water temperature for spawning needs to be below 56oF.  Getting the temperature down that low by November is a tall order, but it was achieved in the 2020-2022 drought (Figure 6) under much lower reservoir storage levels (the present level is 135% of average for October and is much higher than in 2020-2022).  Reclamation achieved November spawning temperatures in those drier, lower-storage years by releasing substantial cold-water from the lower dam outlets, bypassing the power intakes.   The power bypass measure will likely be needed again in 2023 to meet the November temperature targets in the river.

There is a case to be made that Reclamation should also have used the power bypass in September 2023 to maintain 65oF at the Watt Avenue bridge.  Reclamation’s reluctance to use the power bypass to maintain release water temperature requirements further highlights the need for Reclamation to complete the planned refinements to the Folsom powerhouse intake system that will allow both continuous power generation and greater access to Folsom’s cold-water pool.

How else could this series of events have been avoided or at least improved?

First, summer flows in the lower Sacramento River should have been higher to help keep water temperatures at or closer to the standard of 68oF (see Figure 3) at the Wilkins Slough gage, located  on the lower Sacramento River upstream of the mouths of the Feather and American rivers.  Flows at Wilkins Slough for wet year 2023 were well below the average for water years 1994-2003, when salmon did relatively well (Figure 7).  These low flows in 2023 contributed to poor conditions in the lower Sacramento River, the Delta, and the Bay.

Second, the water temperature in the  lower American River at the Watt Avenue Bridge (AWB) should have met the water quality standard of 65oF until September, and should be kept below 60oF in October (Figure 8).  After November 1, Reclamation should maintain temperatures below 56oF for spawning.

Such improved conditions would improve the health of adult salmon spawning in the American River and its hatchery, as well as in other rivers and streams in the Sacramento River watershed.

Figure 1. Escapement (run size) for in-river spawning fall-run salmon in the lower American river 1952-2022.

Figure 1. Escapement (run size) for in-river spawning fall-run salmon in the lower American river 1952-2022.

Figure 2: Flow and water temperature at the Rio Vista Bridge July 15 – September 30, 2023.

Figure 2: Flow and water temperature at the Rio Vista Bridge July 15 – September 30, 2023.

Figure 3. Air and water temperature on the Sacramento River at Red Bluff (River Mile – RM - 240), and water temperature at Wilkins Slough (RM 120), Freeport (RM 50), and Rio Vista Bridge (RM 25). Also shown is water temperature standard at Red Bluff and Wilkins Slough.

Figure 3. Air and water temperature on the Sacramento River at Red Bluff (River Mile – RM – 240), and water temperature at Wilkins Slough (RM 120), Freeport (RM 50), and Rio Vista Bridge (RM 25). Also shown is water temperature standard at Red Bluff and Wilkins Slough.

Figure 4. Water temperature in the upper Sacramento River below Keswick Dam (RM 300), lower American River at Watt Avenue Bridge (AWB), the lower Feather River at Gridley gage (GRL), the lower Sacramento River at Wilkins Slough (WLK, RM 120) upstream of the Feather and American Rivers, and Freeport (FPT, RM 46) downstream of the American River.

Figure 4. Water temperature in the upper Sacramento River below Keswick Dam (RM 300), lower American River at Watt Avenue Bridge (AWB), the lower Feather River at Gridley gage (GRL), the lower Sacramento River at Wilkins Slough (WLK, RM 120) upstream of the Feather and American Rivers, and Freeport (FPT, RM 46) downstream of the American River.

Figure 5. Daily average water temperatures in the lower American River 9/10-10/3 2023 below Folsom Dam (AFD), at Fair Oaks gage below Nimbus Dam (AFO), at William Pond gage (AWP), and at Watt Avenue Bridge gage (AWB). The water quality standard in all water year types is 65oF maximum (year-round) at AWB.

Figure 5. Daily average water temperatures in the lower American River 9/10-10/3 2023 below Folsom Dam (AFD), at Fair Oaks gage below Nimbus Dam (AFO), at William Pond gage (AWP), and at Watt Avenue Bridge gage (AWB). The water quality standard in all water year types is 65oF maximum (year-round) at AWB.

Figure 6. September through December daily average water temperatures of Folsom Dam releases 2020-2022. Note the sharp drops in water temperatures in middle October from Power Bypass cold-water releases to provide target spawning temperatures (56oF).

Figure 6. September through December daily average water temperatures of Folsom Dam releases 2020-2022. Note the sharp drops in water temperatures in middle October from Power Bypass cold-water releases to provide target spawning temperatures (56oF).

Figure 7. Average daily flows in the lower Sacramento River at Wilkins Slough, upstream of the mouths of the American and Feather rivers in 2023, compared to the average during the decade of strong escapement 1994-2003.

Figure 7. Average daily flows in the lower Sacramento River at Wilkins Slough, upstream of the mouths of the American and Feather rivers in 2023, compared to the average during the decade of strong escapement 1994-2003.

 Figure 8. Water temperatures in the lower American River at Fair Oaks (below Nimbus Dam) June-September 2023 with average from prior eight years that included 5 critical dry years.

Figure 8. Water temperatures in the lower American River at Fair Oaks (below Nimbus Dam) June-September 2023 with average from prior eight years that included 5 critical dry years.

Super Moon #4 – Harvest Moon (9/28/23)

The Harvest Moon is the full moon nearest the autumn equinox (in 2023, the equinox was on 9/22).  The Harvest Moon greets fall-run salmon returning from the ocean to the Central Valley.  Unlike the previous two full moons, the 2023 Harvest Moon is coincident with improved conditions for fish.

The last two full moons, the Sturgeon Moon and the Blue Moon, wreaked havoc on the Bay by contributing to warm water and algae blooms (Figure 1) and to the associated low dissolved oxygen levels that led to sturgeon mortality in the Bay (Figures 2-4).  Low Delta water inflows and outflows contributed to the problems.1  The fish kills that occurred in the Bay were generally a consequence of poor water quality brought on by high summer water temperatures, associated algae blooms, and low dissolved oxygen levels (hypoxia).

Water temperatures above 20oC/68oF bring about stressful conditions, while those above 22oC/72oF lead to lethal conditions such as those that occurred in summer 2022 and summer 2023.  Other effects of warm water include plankton blooms and low dissolved oxygen levels that result from the algae die-offs after such blooms.  Though there is no direct evidence of the magnitude of mortality events, there is evidence that such events may have occurred in the Bay in summer 2022 and summer 2023.  Summer conditions in 2022 and 2023, and perhaps prior years, were likely major trauma incidents that had significant short-term and perhaps long-term effects on the sturgeon populations of the San Francisco Bay Estuary (Bay-Delta Estuary).

The warm water and algae blooms in the Bay abated early in September 2023.  Water quality improved with the advent of cooler air temperatures and with the higher Delta outflows (Figure 5) associated with the Fall X2 requirement from the Delta Smelt Biological Opinion (US Dept. of Interior).  The cooling of the water ensured that salmon could safely make their fall runs into the Central Valley rivers during the Harvest Moon, the last super moon of 2023.

Figure 1. River water stage (elevation) and water temperature at Rio Vista Bridge in Sacramento River channel of the Delta near exit to the Bay. Stage drops (draining of the Delta toward Bay) occurred prior to and after the four Super Moons of summer 2023. Note the warm water (74-75oF) draining from the Delta during the two mid-summer drain periods.

Graph of Water temperature (C), dissolved oxygen (DO, mg/l), and chlorophyll (mg/l) in western Suisun Bay in summer 2023.

Figure 2. Water temperature (C), dissolved oxygen (DO, mg/l), and chlorophyll (mg/l) in western Suisun Bay in summer 2023. Note algae bloom at end of July that began during the warm water period. Note very low DO (<6 mg/l) after bloom die-off in August.

Graph of Chlorophyll concentration (mg/l) in 2022 and 2023 in Suisun Bay.

Figure 3. Chlorophyll concentration (mg/l) in 2022 and 2023 in Suisun Bay. Note two summer algae blooms in red circles.

Graph of Dissolved oxygen concentration (mg/l) in 2022 and 2023 in Suisun Bay.

Figure 4. Dissolved oxygen concentration (mg/l) in 2022 and 2023 in Suisun Bay. Note low levels after two summer algae blooms in red circles.

Graph of Daily average flow in summer 2023 and 25-year average at Rio Vista in the lower Sacramento River channel of the Delta leading into Suisun Bay. Late August and September increases are related to the Fall X2 requirement of Delta water projects in wet years.

Figure 5. Daily average flow in summer 2023 and 25-year average at Rio Vista in the lower Sacramento River channel of the Delta leading into Suisun Bay. Late August and September increases are related to the Fall X2 requirement of Delta water projects in wet years.