Scott and Shasta River Update – October 2021 Saved by the Bell

The Scott and Shasta rivers, California tributaries to the Klamath River, received irrigation curtailment orders from the State Water Resources Control Board  September 10 of this drought year.  The Shasta River responded well to the curtailment orders, and flows subsequently improved even more when  the irrigation season ended on 10/1 (Figure 1).  In contrast, the Scott River showed little response to curtailment (Figure 2).  The Shasta River salmon counts reported by the California Department of Fish and Wildlife as of October 18th were 6,659, whereas the Scott River count was only 23.

Heavy rains in late October improved river flows, reduced the need to irrigate pastures and hayfields, and have allowed Chinook and Coho salmon to freely ascend both rivers to spawn. The Salmon River, a third large tributary that enters the Klamath downstream of the Scott, responded similarly to the storms (Figure 3).

Figure 1. Streamflow in the Shasta River Sep-Oct, 2021.

Figure 2. Streamflow in the Scott River Sep-Oct, 2021.

Figure 3. Streamflow in the Salmon River Sep-Oct, 2021.


The Next Threat to Winter-Run Salmon – Rising Delta Exports

A modest production of winter-run salmon fry was achieved in the Sacramento River near Redding this summer (Figure 1).1 With the recent storm that peaked on October 24, these young salmon are now moving down the river toward the Delta (Figure 2).

Upon entering the Delta, these young salmon face the grim fate of passing through the Delta Cross Channel (DCC)/and Georgiana Slough into the central and south Delta, where they are drawn to Delta pumps by sharply increased exports (Figure 3).

The diversion of Sacramento flows increases with the periodic opening of the Delta Cross Channel (Figure 4). On an outgoing tide, the diversion via the DCC and GS can be higher than 50% under these circumstances.

Once they enter the interior Delta, it is difficult for young salmon to navigate out to the Bay. Many are drawn with reverse net flows to the south Delta, especially in periods when the DCC is closed. The risks to salmon fry in Clifton Court Forebay (predation) and at fish facility screens are severe.

Closing the DCC during the flow pulse only increases flow through Georgiana Slough and traps any diverted salmon in the interior Delta. Keeping the DCC open minimizes the reverse flows in the interior Delta, but draws more salmon in. It is a tough call either way. So the best option for this first fall pulse of winter-run fry is to minimize exports. This type of protection has been considered many times in the past. It is currently required in the Incidental Take Permit (p. 80) for the operation of the State Water Project, but not until after December 1.

Figure 1. Passage of juvenile winter-run salmon past Red Bluff, September-October 2021.

Figure 2. Catch of winter-run fry in lower Sacramento River near Wilkins Slough (RM 120) in fall 2021.

Figure 3. Graphic depiction of Delta net flow (cfs) conditions in late October 2021.

Figure 4. Hourly flows through Delta Cross Channel in October, 2021.

Winter Run Chinook Salmon 2021 – Update 10/15/2021

When I last updated the status of the winter-run salmon population of the upper Sacramento River in an April 2020 post, trends in spawning escapement indicated the population was recovering in 2018 and 2019 after the poor runs in 2016 and 2017. That trend continued in 2020 and 2021 (Figures 1-3). These recent runs benefited from wet years in 2017 and 2019, and near-normal 2018 that contributed to better natural egg and fry survival as well as hatchery smolt survival. The only negative trend in the adult escapement is the higher proportion of hatchery-produced adults in the recent year returns that reflects the enhanced hatchery efforts1 during and after the 2013-2015 drought. The prognosis for the 2022 run remains good, as 2019 was a wet year and 2020 was near normal. Both years had flow and water temperature much better than during the 2013-2015 drought.

The prognosis for the 2023 and 2024 runs does not look as good, given the extreme drought conditions in 2021 that have likely limited survival of the 2021 brood year.2 Reclamation undertook unusual operations in 2021 in an attempt to maintain a modicum of winter-run egg and fry survival given the drought conditions (Figure 4). The first indicator of potential success is from screw trap collections at Red Bluff that indicate survival in 2021 has been better than 2015 but poorer than 2018 and 2019 (Figures 5-8). The screw trap collections also produce an end-of-season estimate of total passage (Figure 9), which is another way of summarizing these same data. These indices also show a post-drought recovery from 2018-2020, where 2021 brood-year production would likely fall back to a level below brood year 2018.

In a recent post, the Northern California Water Association (NCWA) expressed a more upbeat prognosis, although tempered by poor drought year 2021 conditions.

“To be sure, the dry and hot conditions in 2021 are not ideal for salmon nor any other part of the ecosystem that depends upon water and they are having challenging years. Yet, despite these dry and hot conditions, salmon are amazingly resilient and they: 1) have returned to the Sacramento Valley in record numbers; 2) will continue to spawn, and 3) are now beginning their journey down the river in large numbers. Importantly, there continues to be a concerted effort throughout the region to improve conditions for every freshwater life-cycle stage of all four runs of Chinook salmon.”

I generally agree on item 3, noting that “large numbers” are relative, as discussed above and shown by comparing the figures below. I do not agree with the other assertions. Much of the “record number” are hatchery fish, as also discussed above. And spawning conditions in the Sacramento River for the rest of the fall will be poor.

NCWA is one of the major users of Sacramento River water. High drought-year allocations of Shasta storage to NCWA users led to high spring demands on storage by NCWA water users (see Figure 4) and in part to the current near-record-low storage in Shasta Reservoir (Figure 10). Unless it rains and snows a considerable amount this winter, salmon and water users will be in dire straits next year.

Figure 1. Winter-run Chinook salmon escapement (run size) to the Sacramento River 1974-2020. (Source: CDFW)

Figure 2. Winter-run Chinook salmon annual aerial redd counts in the upper Sacramento River 2003-2021. (Source: CDFW)

Figure 3. Winter-run Chinook salmon annual carcass counts in the upper Sacramento River 2003-2021. (Source: CDFW)

Figure 4. Winter-run Chinook salmon spawning season conditions in the Sacramento River in 2021. River flows at Keswick Dam (KWK, rm 300) and Bend (BND, rm 250). Water temperatures KWK, BND, and Redding (SAC, rm 290; CCR, rm 280).

Figure 5. Juvenile winter-run salmon counts in Red Bluff screw traps 8/1-10/7, 2021.

Figure 6. Juvenile winter-run salmon counts in Red Bluff screw traps 8/1/15-8/1/16.

Figure 7. Juvenile winter-run salmon counts in Red Bluff screw traps 8/1/18-8/1/19.

Figure 8. Juvenile winter-run salmon counts in Red Bluff screw traps 8/1/19-8/1/20.

Figure 9. Estimated total passage past Red Bluff of unclipped (naturally produced) juvenile winter-run salmon for brood years 2006-2020.

Figure 10. Lake Shasta water level conditions in water year 2021-2022 and other water years, plus historical averages. Source: DWR-CDEC.


Poor First Indicators of 2021 Winter-Run Salmon Fry Production

The first indicators of winter-run salmon spawning survival in the Sacramento River in 2021 indicate poor production, as expected.1 The drought and Reclamation’s operations in 2021 have provided production levels on par with 2014 and 2015, the last two critical drought years.

Red Bluff screw-trap collections since August 1, 2021 have been very low (Figure 1). The spawning delay in 2021 due to high spring water temperatures and low flows may be delaying downstream movement. However, outmigration patterns are similar to 2014 and 2015 (Figures 2 and 3). Even 2020, a dry year with poor production, had numbers five times higher than 2021 to date (Figure 4). Historical wet years with good production like 2006 had collection numbers ten times higher (Figure 5). There is a slim chance that the spawning delays and low flows of 2021 will provide screw-trap collection patterns similar to 2018, a dry year with a later collection peak (Figure 6).

Regardless of the low fry production, the young winter-run salmon must still make it 300 miles to the ocean this fall and winter, a phenomenal hurdle under the best of circumstances. Low fall flows will make the journey difficult. The class of 2021 will get no help from storage releases. Like almost every other user of California water in the beginning of water year 2022, outmigrating winter-run salmon are wholly dependent on future rain to provide the water they need.

Figure 1. Late summer 2021 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.

Figure 2. The 2014 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.

Figure 3. The 2015 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.

Figure 4. The 2020 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.

Figure 5. The 2006 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.

Figure 6. The 2018 catch of salmon fry at Red Bluff traps with water temperature, streamflow, and water turbidity.

A Possible Chance to Save Some Sacramento River Salmon in 2021

The Problem

The 2021 target upper water temperature limit for salmon spawning and gravel-bed egg incubation below Shasta/Keswick dams on the Sacramento River near Redding was 55oF.  It is a little late for that now.  Since September 1, Keswick releases have been greater than 56.5ºF, and are now approaching 58ºF.  That’s too warm for the winter-run salmon who have finished spawning (Figures 1 and 2).

But what about the far larger run of fall-run salmon during their peak October spawning?  Can water temperatures downstream of Keswick be lowered back to 55oF in October?  The answer is a qualified yes.

Figure 1. Daily average water temperature of Sacramento River near Redding (SAC gage), September 1-21, 2021.

Figure 2. Daily average water temperatures from Shasta Dam powerhouse (TCD), immediately below Shasta Dam (SHD), and from Keswick Dam (KWK) to Sacramento River, September 1-21, 2021.

The Solution

A “qualified yes” means it would be a complex undertaking involving two actions possible under Reclamation’s operation of its Shasta/Trinity Division:

  1. Switching most or all of Shasta releases to the cold-water lower river outlets of the dam and ceasing warm-water hydropower releases from the dam’s powerhouse.
  2. Minimizing warm-water hydropower releases from Whiskeytown Lake to Keswick Reservoir.

Much of the remaining cold-water pool in Shasta Reservoir is being used to overcome warm-water hydropower releases into Keswick Reservoir (~60oF or higher) before water is released to the Sacramento River below Keswick Dam.  Cutting hydropower releases and rationing the available cold-water-pool supply through Shasta Dam’s lower river outlets is therefore a potential solution to warm water releases to the river.  Though this would reduce hydropower in the short-term, it would save storage in the long-term.

The solution would require a substantial reduction in Shasta Reservoir releases to ensure the cold-water-pool is not exhausted over the next month or more.  However, reducing releases would lower river water levels and strand salmon redds or reduce egg-embryo survival of remaining active winter-run redds or any newly spawned spring-run and fall-run redds.

A possible resolution is to drop flows after the vast majority of winter-run fry have left their redds and before most of the fall-run salmon have spawned.  This has been the standard management approach in many years to save storage – sometime in late September or in October.

Further Context

Under present conditions in late September 2021, access to the cold-water pool in Shasta Reservoir occurs primarily during the afternoon/evening, during peaking-power releases (Figures 3-5) from the penstocks via the Temperature Control Device (TCD) on the face of the dam.  Side-gate openings on the TCD (Figure 6) are able to pull cold water from below only during peak releases.  This pattern indicates that a modified solution might be to reduce warm-water power releases during non-peak operations, while retaining some peaking power releases from Shasta Dam in combination with lower level dam outlet releases.

Figure 3. Hourly flow releases from Shasta Dam September 18-23, 2021.

Figure 4. Hourly water temperature of water releases from Shasta Dam September18-23, 2021.

Figure 5. Hourly water temperature of water releases from a Shasta Dam penstock September18-23, 2021.

Figure 6. Shasta Dam conditions and operation on September 15, 2021.