Flow pulses released from Shasta Reservoir are badly needed in fall to match up with downstream tributary flow events.  Such flow pulses are needed to support the emigration of young winter-run salmon from the spawning reach near Redding.  The Redding reach receives no flow pulses because fall-precipitation inflows to Shasta are retained as storage in the reservoir, even in wet years.  In a December 2018 post, I described the lack of these badly needed and widely recommended fall flow pulses.

The problem occurred in fall 2021.  Because water year 2021 was a critically dry year with near record low end-of-September Shasta storage, there was understandably a common interest in retaining inflows to the reservoir.  But since water year 2022 began on October 1, there were major Valley-wide storm events, including significant inputs into Shasta Reservoir (Figure 1).

Despite these inflows, there were only reduced releases from Shasta this fall as irrigation demands and water transfers ebbed (Figure 2).  When the flow rates in the Redding reach dropped, water levels also fell 3 to 4 feet, reducing available rearing habitat as well as flows that might stimulate emigration.  The minimal Shasta-Keswick flow releases were high in turbidity (Figure 4), due to the storm-caused erosion in the severely storage-depleted reservoir.  The stage drop and higher turbidity also hurt the fall-run spawners during the peak of their fall spawning in the river near Redding.  None of Mother Nature’s late October flow gift to Shasta Reservoir was shared with beneficial uses immediately downstream.

Further downstream, the Sacramento River received its own gifts (Figure 4), but only from downstream (20-60 miles) tributary inputs.  The young winter-run salmon in the Redding spawning reach should have been given a boost to get them to where they could have benefitted from tributary inputs to the main lower river.  Higher flows in the mainstem provide quicker and safer trips to the Delta, Bay, and ocean.

It is apparent that many of the young salmon left the spawning reach earlier, during the higher September-October flows (Figure 5).  Many of these fish spent the early fall rearing in the upper 60 miles of river in less-than-optimal water temperatures, greater than 58ºF (Figure 6).  This is another reason a flow pulse to stimulate the emigration of those juvenile salmon that remained in the uppermost and coolest reach near Redding was important.

The reason that flow rate is important is that it speeds young salmon emigration.  How fast they move to the Bay-Delta greatly influences their survival (Figure 7).  In low-flow drought years like water year 2014, the fall emigration takes longer (Figure 8). Tag data also indicate flows near 10,000 cfs improve survival over lower fall flows (Figure 9).

So what should the prescription for the fall of 2021 have been?  First, Shasta Reservoir should not have been drawn down so far as to provide release of only warm muddy water.  Second, a pulse flow of at least 7000 cfs was needed coincident with the first lower river flow-pulse event with the reservoir release sometime between October 23 and November 1.  This would have added 2000 cfs to the already existing 5000 cfs reservoir releases (see Figure 2), and 2000 cfs to the already existing 8000 cfs Red Bluff flow (see Bend flow in Figure 4).  Third, a second flow pulse of about 5000 cfs Keswick release was needed on or about December 13 coincident with the second precipitation event and Red Bluff pulse.  This would have added 2000 cfs to the already existing 3000 cfs reservoir release.  Such one-day pulse releases should be short enough in duration to make them unlikely to stimulate substantial spawning of fall-run salmon in areas where the eggs would be subject to stranding.

In conclusion, the two days with an added release of 2000 cfs to create two separate pulse flows would have amounted to 8000 acre-feet of Shasta or Whiskeytown/Keswick storage.  Whiskeytown held 200,000 acre-feet of storage of cooler, lower turbidity Lewiston Reservoir/Trinity River water that could have provided the 8000 acre-feet needed for the Keswick flow pulses.  These two flow pulses would have provided significant benefit in improving the survival of emigrating young winter-run salmon in the Sacramento River near Redding.  A December pulse would also have created benefits for the fall-run spawn.

A one-day flow pulse with an added release from Keswick of 2000 cfs in early January would still provide benefits for outmigrating fall-run salmon.

Figure 1. Four significant precipitation events produced 5000 to 13,000 cfs daily inflow to Shasta Reservoir in fall 2021.

Figure 2. Flow and stage in the Sacramento River below Keswick Dam near Redding in fall 2021.

Figure 3. Water temperature and turbidity in the Sacramento River below Keswick Dam (KWK, RM 300) and above mouth of Clear Creek (CCR, RM 290) near Redding in fall 2021. Red line is 7 NTU turbidity above which eggs and embryo salmon in spawning redds are adversely affected.

Figure 4. Daily flow average (cfs) of Sacramento River below Keswick Dam (KWK, RM 300), at Bend Bridge (BND, RM 240), and at Wilkins Slough (WLK, RM 140) in fall 2021.

Figure 5. Passage rate of juvenile winter run salmon at Red Bluff screw traps and nearby Bend Bridge gage flow summer-fall 2021. Note increased catch rate during pulse flow events.

Figure 6. Water temperature (F) in the Sacramento River below Keswick Dam (KWK, RM 300) and at Red Bluff (RDB, RM 240) in fall 2021.

Figure 7. Estimated survival rate from Redding to Delta for juvenile salmon per the number of days spent upstream. Source: NMFS presentation.

Figure 8. Cumulative passage of winter-run at Red Bluff screw traps 2007-2013. Note longer period of passage in fall 2013 for Brood Year 2013. Source: USFWS Red Bluff.

Figure 9. Survival of juvenile salmon (acoustic-tagged wild and hatchery spring-run and fall-run salmon) as a function of flow in upper Sacramento River from Red Bluff (RM 240) to the Delta (RM 100). NMFS, Santa Cruz: “Nonlinear survival of imperiled fish informs managed flows in a highly modified river”. Cyril J. Michel $, Jeremy J. Notch, Flora Cordoleani, Arnold J. Ammann, Eric M. Danne. First published: 19 May 2021 doi.org/10.1002/ecs2.3498. Ecosphere / Volume 12, Issue 5 / e03498

Fall-run salmon spawn in the fall in the 20-40 miles of the Sacramento River downstream of Keswick Dam near Redding. Numbers of in-river fall-run spawners have declined severely over the past several decades (Figure 1). Declines were worst three years after drought periods (2007-2009, 2013-2015), due to poor egg and fry survival during droughts. A February 2021 post discussed the role of redd dewatering and fry stranding from severe drops in flow and water level (stage) as major drought-related factors in the escapement declines. A 2018 post listed a broader range of factors, including high water temperatures during droughts in addition to stranding.

Stranding was once again a major factor in fall 2021 as water levels near Redding dropped 4 feet from October to November (Figure 2). Further downstream in the lower spawning reach, salmon have also had to contend with high flows as well (Figure 3). High flows (1) encourage salmon to spawn in margin habitat that later dewater, and (2) cause scouring of redds spawned earlier at lower water levels.

In fall of drought year 2021, an additional severe-mortality factor has become apparent. Turbidity/suspended sediment levels in the spawning reach (Figure 4) were at or above lethal levels for salmon eggs and embryo (see December 23, 2021 post) for most of November, a peak spawning period. The late-October record storm and subsequent further rain and runoff have elevated inflows to Shasta Reservoir. As these higher flows have entered the reservoir, they have eroded vast areas of sediment exposed in the drought-depleted reservoir.¹ The suspended sediment has carried through the reservoir into the spawning reach below Keswick Dam.

Of positive note, the higher flows (Figure 3) and associated turbidity have likely helped salmon fry that spawned earlier in tributaries like Battle Creek and Clear Creek move downstream in the Sacramento River toward the Delta and Bay.

In summary, fall-run salmon spawning in the most upstream reach of the lower Sacramento River near Redding have faced extreme habitat conditions in 2021. These conditions began with high October water temperatures from a depleted cold-water-pool in Shasta Reservoir. Next came a four-foot drop in water level due to sharply reduced Shasta Reservoir releases. Added to these traumas were egg-smothering levels of suspended sediments from Shasta Reservoir caused by erosion of drought-exposed, decades-old reservoir sediment during a record-level late October storm and subsequent runoff events.

Figure 1. In-river fall-run Chinook adult escapement to the upper Sacramento River 1952-2020.

Figure 2. Streamflow (cfs) and water surface elevation (stage) in the Sacramento River immediately below Keswick Dam October 1 – December 15, 2021.

Figure 3. Streamflow (cfs) and water surface elevation (stage) 50 miles below Keswick Dam October 1 – December 15, 2021. High flows were from tributary inflows below Redding (Cow Creek, Battle Creek, Clear Creek, and others).

Figure 4. Water temperatures and turbidities below Keswick Dam (RM 300) and above the mouth of Clear Creek (RM 290) October 1 – December 15, 2021. Red line depicts literature-based, severe-mortality turbidity level for eggs and embryo salmon for a one-day exposure.

Figure 5. Spring and fall run salmon fry catch at Red Bluff (RM 240) screw traps August – November, 2021. Also shown are nearby Bend Bridge water temperature and flow, and Red Bluff turbidity.

The Bureau of Reclamation and California Department of Water Resources (DWR) have proposed another temporary urgency change petition (TUCP) for Delta operations in 2022 (Figure 1, below).  The purported purpose is:

operating the Projects to provide for minimum health and safety supplies…; 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 maintain cool river temperatures for various runs of Chinook salmon; maintain protections for State and federally endangered and threatened species and other fish and wildlife resources; and meet other critical water supply needs.  (TUCP, p. 1).

Under the previous TUCPs in 2014, 2015, and 2021, Reclamation and DWR did not preserve reservoir storage, control salt water intrusion, maintain cold-water in Central Valley reservoirs, or protect listed fish species, but they sure did sustain Central Valley farmers.  In the spirit of being consistent, the latest TUCP makes no mention of the tradeoffs or specific priority criteria.  That’s because, once again, everything in this TUCP is for water contractors.  There is no fresh water to the Bay, its crabs, herring, or anchovies, let alone its salmon, smelt, striped bass, or other fisheries.

The TUCP claims: “The TUCP will support Reclamation and DWR in balancing the competing demands on water supply and is critical to provide some protection of all beneficial uses of the Delta including for fish and wildlife, salinity control, and critical water supply needs.”  (TUCP, Environmental Information, p. 1).  No, it’s simply for contractor water, nothing else.

The TUCP explains: “The continuation of extremely dry conditions in the Delta watershed has resulted in inadequate water supply to meet water right permit obligations for instream flows and water quality under D-1641.”  (TUCP, p. 1).  Apparently, Reclamation and DWR must have forgotten that during extremely dry conditions last year and the year before, Reclamation and DWR gave too much water to their contractors.  They depleted storage to historic lows.  In 2020 and 2021, they knew the snowpack was low.  They knew reservoirs would empty.  They delivered the water anyway.

Well, things are looking really bad: “[T]he conditions of 2021 have left the Projects in a precarious state, with little water to manage even under slight drought conditions next year.”  (TUCP, p. 2).  They knew this was going to happen.  They also knew they could employ their TUCP tricks again.

But fear not.  “[T]he proposed changes in operations will not injure other lawful users of water; will not unreasonably affect public trust resources such as fish and wildlife or other instream beneficial uses; and are in the public interest.”  (TUCP, p. 2).  This is an outright lie, and they think we are suckers enough to believe it.

Figure 1. TUCP Framework, Table from TUCP, p. 2.

Translation of Figure 1: Let no water flow to the Bay.  Open the Delta Cross Channel gates to capture all the out-migrating salmon, steelhead, sturgeon, and steelhead and divert them straight to the Central Delta and water project pumps, along with the fresh water from the Sacramento River.  Let the San Joaquin River die.  Make minimal exports from the Delta because upstream contractors will take all the reservoir and river inputs to the Delta.  Well, not entirely, because upstream contractors will sell much of their water to Southern California users.  The State Water Board will allow transfers through the Delta without the minimal safeguards required for non-transfer exports.  In sum, Reclamation and DWR will deliver to Sacramento Valley contractors about 20 times the water allegedly “saved” by weakening Delta standards, once again disproving the elementary school arithmetic that says to preserve storage, you can’t let more water out of a reservoir than you take in.

Is this a great system or what?

For more on the subject, read https://www.nrdc.org/experts/kate-poole/california-drought.