Update on Shasta River – Summer 2022

In a post in July 2021, I discussed the problems facing Shasta River salmon.  An 8/20/22 article in CalMatters described how the problems became acute this summer when the local ranchers’ water association ignored the State’s emergency order to stop diverting water from the Shasta River in this drought year.  After complying for most of the summer, the ranchers diverted about 20 cfs of water for about a week in mid-August (Figure 1; blue line)

Figure 1. Streamflow in the lower Shasta River upstream of Montague. Ranchers complied with the State’s emergency drought order until mid August. After a week under the threat of fines they stopped diverting.

What the ranchers did in mid-August was simply what they had been doing for decades but were asked to stop in 2022 (see Figure 1, median for 37 years; orange line).

It appears based on the downstream Yreka gage that other ranchers also took part in ignoring the State’s mandate (Figure 2) as the deficit reached about 30 cfs.  These other diverters also returned to compliance with the mandate after a week of non-compliance.

Several reductions in Shasta River flow are not mentioned in the CalMatters article. The total water supply to the Shasta River from springs  originating from Mt. Shasta is somewhere between 250 and 300 cfs in most summers (Figure 3 shows summer of wet year 2017).  In critical drought year 2022, the total supply is closer to 200 cfs, because there are less spring inputs and demands are greater.  In general, about 40-50 cfs is taken out by large wells from the 100 cfs input of Big Springs (leaving the roughly 50 cfs of river flow reaching Montague in Figure 1).  The springs shown in Figure 3 provided less inflow in drought year 2022 than they did in 2017, because Lake Shastina is critically low and input from the upper river and its springs are lower (Figure 4).  The upper Shasta River also loses water at Weed to the city supply and to water bottlers.

Coho salmon once thrived in the Shasta River below Big Springs and in the upper Shasta River.  Coho have suffered for many decades under the historical pattern shown in Figures 1-3.  Some of the remnant population may have been living in the 20 miles of river below Montague this summer, until they were subjected to the low flows and very stressful water temperatures that came with the one week of unauthorized diversions.  There is also this year’s run of fall-run Chinook salmon holding in the Klamath River at the mouth of the Shasta River, awaiting sufficient flow and adequate water temperatures to migrate up the Shasta River.

The fact is that the State Water Board can’t solve a century-old problem with an emergency decree in one dry summer.  The State needs to develop a comprehensive solution for the Shasta River that provides 50 cfs of water for salmon year-round (at Montague Figure 1, and Yreka, Figure 2), out of the available 200-300 cfs supply.  Users need to share the rest equitably, especially in a drought year like 2022.

Figure 2. Streamflow in the lower Shasta River downstream of Yreka in the summer of 2022. Also shown is daily average mean flow for the previous 85 years.

Figure 3. Selected Shasta River hydrology in late May of wet year 2017. Roughly 150 cfs of the 300 cfs total basin inflow in this wet year is being diverted for agriculture, city water supply, and water bottling (Weed) with remainder reaches the Klamath River. Red numbers are larger diversions. The “X’s” denote major springs. Big Springs alone provides near 100 cfs. Of the roughly 100 cfs entering Lake Shastina (Dwinnell Reservoir) from Parks Creek and the upper Shasta River and its tributaries, only 16 cfs is released to the lower river below the dam. The remainder is stored and released to east-side irrigation canal (about 50 cfs). Red numbers and arrows indicate larger agricultural diversions. Up to 15 cfs is diverted to the upper Shasta River from the north fork of the Sacramento River, west of Mount Shasta. Blue dots show locations of river flow gages.

Figure 4. Hourly flow in the upper Shasta River in summer 2022 at Edgewood just downstream of the City of Weed.

Wishful Thinking on The Upcoming 2022 Salmon Season

We should be careful about wishful thinking in considering the forecasts for the 2022 California salmon season along the coast and in major rivers.1  The 2022 ocean abundance projection for Sacramento River fall Chinook, a main salmon stock harvested in California waters, is estimated at 396,500 adult salmon, a higher number than the 2021 forecasts. However, we should expect further drought-related fishery and escapement downturns in 2022 and 2023, as occurred after the 2007-2009 and 2013-2015 droughts (Figure 1). We can also expect low fishery catches, especially in rivers from low summer flows and associated high water temperatures that keep river spawners in the Bay until rivers cool in the fall.

The issues relate primarily to remaining stocks of Chinook salmon, not to the nearly extinct endangered Coho. The 2022 season also relates mostly to the availability of brood year 2019 salmon from Central Valley rivers, not coastal streams. Finally, it is important to remember that most of the adult salmon in 2022 will come from hatcheries on the Klamath, Trinity, Sacramento, Feather, American, Mokelumne, and Merced rivers, especially those hatcheries that truck and barge salmon to the Bay or coast.

Hatchery returns, the backbone of California salmon fisheries, are likely to be lower in 2022 than expected. Near 40 million Chinook salmon smolts from brood year 2019 were released from California federal and state hatcheries in 2020. Of the total, about 26 million were raised at Sacramento River watershed hatcheries, 9 million at San Joaquin River hatcheries, and 4 million at Klamath-Trinity hatcheries. Most of the releases were fall-run (34 million), with about 4 million spring-run, 1 million late-fall-run, and 0.4 million winter-run. Their returns of jacks and adults are likely to be lower in 2022 than expected because of low Delta inflows and outflows (Figure 2) and low Klamath-Trinity flows (Figures 3 and 4) in winter-spring 2020 and 2021, which are likely to result overall in relatively poor returns from river and Bay releases of hatchery smolts.2

Wild salmon stocks, already severely depressed, are going to further decline and contribute even less to fisheries. Natural production of brood years 2019 and 2020 was likely poor because wild smolts faced dry-year conditions in winter-spring 2020 and 2021, respectively.

Adult salmon that return to spawn in 2022 will face warm rivers, as they did in 2021 (Figures 5 and 6). They will be delayed, and many will die before spawning.

In summary, we must be careful about wishful thinking about the future based on the recently released ocean abundance estimate for 2022. Many other factors point in a downward direction. Perhaps the most immediate question is whethersalmon will simmer again in what looks to be a dry, hot summer.

Figure 1. Sacramento River Basin fall-run salmon escapement 1975-2020.

Figure 2. Sacramento-San Joaquin Delta outflow 2014-2022.

Figure 3. Klamath River flow at Orleans 2014-2022.

Figure 4. Trinity River flow at Hoopa 2014-2022.

Figure 5. Flow and water temperature in the lower Sacramento River at Wilkins Slough in 2021. Red line is 20ºC (68F) water quality standard and safe upper level for salmon.

Figure 6. Water temperature at Wilkins Slough in 2021 and recent historical average.

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.


What is it about the Scott River and its Coho Salmon?

A recent article in Science Magazine provides a possible clue as to why the Scott River, a California tributary to the Klamath River, still produces a relatively large amount of coho salmon. A chemical released onto roads as tires wear has been found to kill young coho.1 Watersheds like the Scott River are pristine, sourced directly from springs and snowmelt, with low highway interaction. The Scott contrasts with its neighbor the Shasta river, which runs very close to Interstate Highway 5, and which produces few coho salmon.

Absence of pollution from tire debris may also be part of the reason why Butte Creek is able to produce so many spring-run salmon. On the other side of the coin, the prevalence of roads may help explain why coho salmon have been extirpated from many of the highly urbanized Puget Sound watersheds in Washington State and British Columbia.

The recent study regarding pollution from tires emphasizes the need to protect pristine watersheds like the Scott River, as well as the need to restore those like the Shasta River. There is likely to be more public discussion of this subject in the coming months and years, hopefully as the tire industry seeks alternatives to its problem chemical

  1. As described in Science Magazine, the chemical is: “a highly toxic quinone transformation product of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), a globally ubiquitous tire rubber antioxidant.”

Scott River Coho 2020 Run Improves

I last updated the status of Coho salmon in the Scott River, a major Klamath River tributary in northern California east of Yreka (Figures 1 and 2), in a January 2020 post. At that time, I lamented on the decline of the strongest distinct population subgroup, 2013-2016-2019, exemplified by the weak run in 2016 caused by the 2013-2016 drought. In this post, I am happy to report on the strong 2020 run and the surprise improvement of the 2014-2017-2020 subgroup (Figure 3).

The improvement in the 2020 run, despite a sparse spawning run in late-fall 2017, is likely a consequence of good water conditions in early water year 2018 (Oct 2017-Sep 2018, Figure 4) after wet water year 2017. The run had good access to spawning habitat and early rearing conditions from fall 2017 through the spring of 2018. The young coho were sustained though the dry summer of 2018 in spring-fed reaches of the upper river and its tributaries. Spring-fed habitats likely benefitted from the abundant winter 2017 snowpack. The Scott watershed had also benefitted from significant restoration of its over-summering habitat over the past decade.1

The yearlings of brood year 2017 then had good wet year emigrating conditions in late fall 2018 and early winter 2019 (Figures 4 and 5). There were multiple winter flow pulses to help the yearling coho smolts emigrate from Scott Valley and on down the Klamath to the ocean.

In summary, the spawning run in fall 2020 (from brood year 2017) was exceptional, benefitting from conditions that were a consequence of wet years 2017 and 2019. Over-summering survival in dry year 2018 was likely good because of good spring-fed flows and habitat in the upper watershed, a carryover from the good 2017 snowpack and restoration of beaver-pond habitat by Scott Valley stakeholder groups. This one small success bodes well for recovering other salmon and steelhead populations throughout the Klamath watershed, especially in a future dominated by climate change.2

Figure 1. Klamath River watershed with the Scott River west of Yreka, CA. (Source DOI.)

Figure 2. Google Earth view of the Scott River watershed with its snow-covered Marble Mtns to the west and the Trinity Alps to the south. Scott Valley, with its green hay fields from Etna to Fort Jones, was once called “beaver valley” due to its abundance of spring-fed beaver ponds and meadow streams ideal for over-summering salmon and steelhead.

Figure 3. Spawner-recruit relationship for Scott River Coho salmon. The number represents recruits (spawner counts) for that year versus spawners counts from three years earlier. For example: “13” represents spawner counts (recruits) in fall 2013 versus spawner numbers three years earlier in 2010. Number color represents different spawner subgroups (blue=subgroup 10-13-16-19). The Red circle highlights the significant outlier in 2016. The Yellow line is trend-line for years other than 2016 and 2020. Data source: CDFW weir counts.

Figure 4. Scott River streamflow measured downstream of Fort Jones as the river leaves Scott Valley, September 2017 to April 2019. Note the near average wet winters in 2018 and 2019, and dry summer in 2018 typical of the Mediterranean climate of northern California. The drier-than-average summer 2018 is indicative of water use for hay-pasture irrigation.

Figure 5. Klamath River streamflow measured downstream of the mouth of the Scott River, October 2018 to June 2019. Note the near average wet winter-spring with five distinct flow pulses typical of wetter years. of the Mediterranean climate of northern California. The flow pulses helped yearling coho from brood year 2017 emigrate to the ocean. The adults from brood year 2017 returned in late fall of 2020.