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 (>65^oF, 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 <65^oF 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 56^oF.  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 65^oF 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 68^oF (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 65^oF until September, and should be kept below 60^oF in October (Figure 8).  After November 1, Reclamation should maintain temperatures below 56^oF 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 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 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 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 (56^oF).

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.

It is that time of year again for another Sacramento River Temperature Management Plan.  You know, the plan adopted to protect Sacramento River salmon from the operation of the Shasta/Trinity Division of the federal Central Valley Project of US Department of Interior, Bureau of Reclamation (Reclamation).  Past plans have failed to protect salmon since they became a requirement in 1990 in the State Water Board’s Water Rights Order 90-05.

The plans have failed even in wet years, including this wet year (four wet years have occurred since 2010).  This year, Shasta Reservoir is full, and there is more than ample cold water to deliver to the salmon below Shasta Dam (a “Tier 1” wet year).  Oroville and Folsom reservoirs are also full this year and ready to help Shasta supply the needs of salmon in the Sacramento River and Bay-Delta.

In this year’s 2023-sacramento-river-temperature-management-plan, Reclamation has committed to providing 53.5^oF water in the upper ten river miles (RM) of the Sacramento River downstream of Keswick Dam (RMs 290-300).  53.5ºF is the upper optimal threshold water temperature for adult salmon spawning, egg incubation, and fry emergence.  Reclamation has not always met this temperature in past wet years (Figure 1).

Other important benchmarks are maintaining lower Sacramento River water temperatures at and upstream of Red Bluff (RM 240) at <56^oF and at <68^oF downstream of Red Bluff (RMs 100-240).  Reclamation has exceeded these temperatures in the three most recent wet years (Figure 2).  Reclamation has not met summer water temperatures in the lower Sacramento River below 56^oF at Red Bluff (RM 240) and below 68^oF at Wilkins Slough (RM 120), because water diversions leave flows too low in summer (Figure 3).  In fact, Reclamation has given up trying to meet those temperatures.  The 2023 TMP evaluates maintaining 56^oF at Balls Ferry, 36 miles upstream of Red Bluff, but concludes, without any supporting data or evidence, that maintaining that objective would be too uncertain and risky.

Analyses of flow and water temperature data for Wilkins Slough indicates it generally takes 6,000 to 10,000 cfs flow at Wilkins Slough to maintain water temperatures below 68^oF in June, depending on air temperatures.  Note the water temperature in early June 2023 reached above 68^oF (Figure 2) as flows fell below 10,000 cfs (Figure 3).

Table 1 shows optimal temperatures for adult migration, holding, and spawning.  Adult salmon migrating, holding, or spawning are stressed by water temperatures above 60^oF.  Water temperature above 68^oF are considered “lethal” for migrating salmon – such temperatures occurred in June of three wet years (Figure 2).  Stressful water temperatures occurred during the spring in the lower Sacramento River in all four wet years (Figure 3).  Spawning and egg incubation water temperatures exceeded the target 53^oF for spring-summer spawning winter run salmon in all four wet years (Figure 1).

The 2023 Sacramento River Temperature Management Plan

“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.” (2023 TMP, p. 3) 

Comment:  Reclamation’s repeated strategy of staying close to 56º in a limited stretch of the Sacramento River, even in a year like 2023 when there is really no reason to adopt such a conservative strategy, unnecessarily compromises the salmon and sets a course for failure to meet permit requirements.  At the beginning of June, there were still endangered adult winter-run and spring-run salmon migrating up the lower Sacramento River.

As in 2023, Reclamation made overt decisions in 2017 and 2019 to drop flows below 7000 cfs in the lower reaches of the lower Sacramento River, knowing water temperatures would exceed their permitted upper limit and water quality standard of 68^oF.  Flows closer to Keswick Dam in Redding also dropped, allowing Red Bluff water temperatures to exceed their limit of 56^oF.

“The strategy of meeting 53.5 at CCR will likely result in average daily temperatures at or near 56 degrees F at BSF. Reclamation does not propose to operate the TCD explicitly to meet 56 degrees F at BSF under conditions that may require changes to TCD operations that could risk cold water pool resources for use later in the temperature management season. This would cause an unreasonable risk to other goals and objectives”.  (2023 TMP, p. 4)

Comment:  The TMP acknowledges from the start that Reclamation has no intention of meeting the 56^oF standard at Balls Ferry (RM 276), let alone Red Bluff (RM 240).  With CCR maintained at 53^oF, it takes more dam releases to keep the 60-mile upper river reach below 56^oF and the 100+ miles of lower river below 68^oF.  The 2023 Plan thus plainly ignores these other license and water quality standard requirements important to salmon survival.  Lower river water temperatures above 68^oF through late summer will also compromise the fall-run salmon migration up the river.

Update

Water temperatures in the Sacramento River downstream of Red Bluff steadily increased through June (Figure 4).  In over 100 miles of the Sacramento River from Red Bluff downstream to the mouth of the Feather River, Reclamation is operating in violation of federal/state water quality standards, the federal/state Endangered Species Acts, and state water rights permits.  Water temperatures have reached lethal levels for migrating adult and juvenile salmon blocking their migrations up and down the river, respectively.  Stress, disease, and predation are compromising two brood years of salmon production in a wet year!  Water diversions from the river below Red Bluff are approaching 6000 cfs (Figure 5) not counting diversions upstream or from tributaries.

In Conclusion

In conclusion, the Sacramento River Temperature Management Plan should cover all of Reclamation’s obligations under its permits and all applicable water quality standards, not just water temperatures in the upper 10 river miles of over 200 river miles used by salmon.

Table 1. Water temperature objectives for adult Central Valley salmon. (Sources: San Joaquin River Recovery Plan). Note that the temperatures cited in this figure are the maximum daily temperatures. The 2023 TMP target for winter-run Chinook spawning is an average daily temperature of 53.5ºF.

Figure 1, Water temperature (daily average) at the Clear Creek gage in the Sacramento River above the mouth of Clear Creek (RM 290) in wet years 2011, 2017, 2019, and 2023.

Figure 2. Water temperature (daily average) at the Red Bluff (RM 240) and Wilkins Slough (RM 120) gages in the Sacramento River in wet years 2011, 2017, 2019, and 2023.

Figure 3. Lower Sacramento River flow at the Wilkins Slough gage (RM 120) in wet years 2011, 2017, 2019, and 2023.

Figure 4. Water temperature and streamflow at Bend Bridge (RM 250) and Wilkins Slough (RM 120) in May-June 2023. Note 68^oF water quality standard and critical water temperature for salmon is exceeded.in late June at Wilkins Slough gage. The 56^oF standard was exceeded at Bend Bridge for much of May and June.

Figure 5. Streamflow at various gages in the Sacramento River from Keswick Dam (RM 300), Bend Bridge (RM 250) downstream to Wilkins Slough (RM 120) in May-June 2023. Note: tributary inflows in the reach below Bend gage in mid-June were approximately 5000 cfs in mid-May. Keswick Dam releases were increased in late June to maintain deliveries and sustain 5000 cfs at Wilkins Slough gage.