Author Archives: Tom Cannon

The Importance of Big Springs to the Shasta River

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Big Springs contributes streamflow, cold water, and volcanic nutrients to the middle and lower Shasta River. Although its contribution to the overall volume of the Klamath River is small (Figure 1), the cold, nutrient-rich flows originating from Mount Shasta’s source springs, combined with a gentle gradient, play a key role in making the Shasta River the most productive salmon tributary in the Klamath River watershed.

Streamflow

Big Springs is the major source of water for the Shasta River.  It’s 52ºF clear water supports salmon, steelhead, and trout in the middle and lower Shasta River.  Its 100-120 cfs base inflow makes up the predominant flow of the Shasta River in summer (Figure 2).

Much of the water sourced from springs in the watershed is diverted for agriculture or other human purposes. The primary uses are pasture irrigation, hay production, and livestock watering. Other purposes include bottled water production, domestic use, and city supply.

Water from the upper mainstem—both spring-fed and snowmelt—is stored in Lake Shastina and released gradually throughout the summer via a large canal and ditch system. Big Springs, which serves as the main source of spring water for the middle and lower river, is also diverted or pumped into irrigation systems through several small dams and distribution networks.

Notwithstanding its springs-fed sources, the Shasta River experiences ongoing streamflow shortages, especially during summer and fall in most years. Only exceptionally wet years provide enough water for both ranchers and fish. In dry years, nearly all water is allocated to agriculture, leaving the lower river and its main tributaries—such as Parks Creek, Little Shasta River, and Yreka Creek—almost completely dry. Salmon and steelhead manage to survive during these dry periods only in the middle sections of the Shasta River and in nearby large springs fed by Mt. Shasta’s snow fields or by leakage from Lake Shastina.

Before irrigation begins on April 1, base flows in the Shasta River are about 150 cubic feet per second (cfs). They drop to 10-20 cfs or less by summer (Figures 3 and 4). Flow recovers once irrigation ends after October 1. Most diversions in the mainstem Shasta River happen in the reach 10 to 20 miles downstream from Big Springs, as shown by streamflow data from Montague (Figure 5).

Water Temperature

Reduced flows result in elevated temperatures in the lower river, often above 65ºF. These high temperatures restrict salmonid habitat, survival, and smolt production. Unlike the nearby Scott River, dewatering and stranding aren’t major issues in the middle Shasta River’s spring-fed refuge. Instead, high water temperatures between Grenada and the mouth of the Shasta River at the Klamath River pose the main challenge. Historical temperature records at Yreka show that the lower river becomes almost uninhabitable for salmonids in summer, with temperatures reaching 20–25ºC due to low streamflows and warm agricultural runoff.

Data from the Grenada gage (Figure 6) show acceptable water temperatures (below 20ºC) when streamflows exceed 50 cfs. These levels would at least meet the minimum requirements for migrating adult fall-run Chinook salmon in late summer.

Most salmon and steelhead spawning and rearing occur in the middle stretches of the Shasta River below Big Springs, where cold, spring-fed water creates ideal habitat. However, during dry summers like 2021 (Figures 3 and 4), the amount of cold spring-sourced water that reaches Yreka is minimal due to upstream extraction.

Source of Nutrients

“The unique water quality of the Big Springs complex, and presumably other spring complexes associated with the Shasta River south of the Big Springs Creek-Shasta River confluence, was likely one of the largest contributing factors to high historical abundances and productivity of salmonids in the Shasta River.” (Jeffres, et. al. 2009.)

The Shasta River below the spring complexes is rich in natural sources of nitrogen (N) and phosphorus (P). These elements support high concentrations of aquatic invertebrates. This in turn contributes to the river’s historically high fish production (Jeffres, et. al. 2009).

Agricultural runoff is another source of nutrients. However, agricultural return flows often have elevated water temperatures, which, in combination with animal and plant waste, contribute to point sources of low dissolved oxygen in the stream.  Such conditions degrade salmonid spawning, rearing, and migration habitat.

Conclusion

Big Springs and other springs in the Shasta River system supply cold, high-quality water that supports salmon and steelhead populations. Maintaining an adequate amount of spring-fed water throughout summer is vital. Any assessment of river flow needed for salmon and steelhead should consider the source and quality of streamflow, as well as the location of springs in relation to specific reaches of the river. Flow, water temperature, and proximity to springs are all important.

Figure 1. Lower Klamath River with late May of wet year 2017 streamflows in red. Note Shasta River streamflow was only 140 cfs near Yreka, California. Data source: CDEC.

Figure 2. Selected Shasta River hydrology in late May of wet year 2017. Roughly 150 cfs of the 300 cfs total basin inflow was diverted for agriculture, with remainder reaching the Klamath River. Red numbers are larger diversions. The “X’s” denote major springs. Big Springs alone provides near 100 cfs. Of the 100 cfs entering Lake Shastina (Dwinnell Reservoir) from Parks Creek and the upper Shasta River and its tributaries, only 16 cfs was released to the lower river below the dam. Red numbers and arrows indicate larger agricultural diversions. Up to 15 cfs is normally diverted to the upper Shasta River from the north fork of the Sacramento River, west of Mount Shasta.

Figure 3. Streamflow during peak Chinook salmon spawning season in the lower Shasta River near Yreka CA in September and October of drought year 2021. Yellow markers show average for the day over 84 years of gage record.

Figure 4. Streamflow in the lower Shasta River near Yreka CA from April 2018 through June 2021. Yellow markers show average for the day over 84 years of gage record. Note the low streamflow in dry summer 2020 and spring-summer of drought year 2021.

Figure 5. Streamflow in the lower Shasta River near Montague CA from April 2019 through June 2021. Note the low streamflow (<30 cfs) in spring-summer of dry year 2020 and spring of drought year 2021.

Figure 6. Water temperature (hourly) in the lower Shasta River below Big Springs near Grenada CA July 2019 to June 2021. Source: CDEC.

Bibliography

Jeffres, C. A., R.A. Dahlgren, M.L. Deas, J.D. Kiernan, A.M. King, R.A. Lusardi, J.M. Mount, P.B. Moyle, A.L. Nichols, S.E. Null, S.K. Tanaka, A.D. Willis. 2009. Baseline Assessment of Physical and Biological Conditions Within Waterways on Big Springs Ranch, Siskiyou County, California. Report prepared for: California State Water Resources Control Board. https://watershed.ucdavis.edu/sites/g/files/dgvnsk8531/files/products/2021-11/Jeffres-et-al-SWRCB-2009.pdf

Shasta River Watershed Stewardship Report. 2018. Shasta Valley Resource Conservation District 215 Executive Court, Suite A, Yreka, CA 96097. Version 1.2 April 2018. https://ifrmp.org/wp-content/uploads/2021/10/SVRCD_2018_0548_Shasta_Watershed_Stewardship_Report.pdf#:~:text=Shasta%20River%20Watershed%20strongly%20influences%20groundwater%20chemistry%2C%20which%20is&text=Big%20Springs%2C%20Shasta%20River%20at%20the%20Montague%E2%80%90Grenada%20Bridge%2C%20and%20Shasta%20River

Butte Creek Spring-Run Salmon – May 2026 Update

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Central Valley Spring-run Chinook Salmon. Central Valley spring-run Chinook salmon typically return from the ocean and enter the Sacramento River system from February through June. Spawning occurs in Sacramento River tributaries from mid-September through early October with genetically distinct populations known from Clear, Mill, Deer, and Butte Creeks. Central Valley spring-run Chinook salmon also spawn in the Feather and Yuba rivers. Juveniles emigrate soon after emergence as young-of-year, or remain in or near their natal streams and emigrate as yearlings. Yearlings typically emigrate with the first flow increases in the fall and early winter. Similar to winter-run, Central Valley spring-run Chinook salmon populations have suffered significant declines in size. They are state and federally listed as threatened. CDFW

Butte Creek is a moderately sized tributary of the Sacramento River, located in California’s Central Valley near Chico, CA (Figure 1). It supports a core population of the threatened spring-run Chinook salmon native to the Central Valley and Sacramento River. Over the past decade, the Butte Creek watershed has experienced some of the largest Sierra fires of recent record.1 Prior to this period, the spring-run salmon in Butte Creek had represented a successful recovery within one of the Central Valley’s few remaining undammed streams.

I last updated the status of the Butte Creek spring-run salmon in a November 2024 post.  The spawning runs in spring-summers of 2023 and 2024 had been devastatingly low after suffering in the most recent three-year drought (2020-2022).  Some recovery in the spawning population in 2025 and 2026 brings a measure of optimism.

Problems with Recruitment

Low runs in 2023 and 2024 (Figure 2) suggest that brood years 2023 (BY23) and 2024 (BY24) will make limited contributions to runs between 2025 and 2028. Fewer eggs and any poor survival rates (e.g., from the 2024 fires or Thiamine deficiencies) will restrict recruitment of age 2-4 spawners from both brood years, limiting their contributions (recruitment into) to the future runs.

Initial survey findings show that the runs in 2025 and 2026 had fewer contributions from BY23 and BY24. Instead, most of the fish came from BY21 and BY22 spawners, whose offspring thrived during the wet years of 2023 to 2025 and gained advantages from fishery closures in those same years. Preliminary information on the 2026 run (not shown in Figure 2) indicates a low run, with only modest numbers of age-4 BY22 spawners, and lacking the normally predominant age-2 (BY 24) and age-3 spawners (BY 23).

The Cause

The cause of depressed recruitment in 2023 and 2024 was most likely poor spawning and early survival conditions during drought water years 2020-2022 that affected brood years 2020-2024.  The poor 2023 run was likely the consequence of poor survival of their source spawning adults (prespawn mortality in 2019-2021), eggs laid (2019-2021), and juveniles reared (2020-2022) of BY19-BY21 affected by the drought conditions of fall 2019 through winter-spring 2022.  For example, conditions in 2020 were very poor from low flows and high water temperatures from spring to fall (Figure 3).  The failure of PG&E’s Butte Canal in 2023 may have also been a factor.

The cause of the poor 2024 run is more complicated, because the number spawners in 2021 was high.  Drought conditions in fall 2021 and spring 2022 likely contributed to poor reproductive success and low smolt production (Figure 4).  However, the 2023 and 2024 ocean fisheries were closed, which should have more than doubled the normal run size.  The 2024 massive Park Fire may have contributed to the poor run, with lower summer-fall flows and higher water temperatures (Figure 5) and high pre-spawn mortality.

Other factors related to escapement (run size) include ocean conditions (e.g., the warm water blob and Thiamine deficiency), fishery harvest (or lack thereof), conditions in the lower Sacramento River and Bay- Delta.  All factors acting together in combination is yet another factor, with each factor potentially contributing to the other factors.

Conditions in the lower Sacramento River and Bay-Delta are changing for the worse.  For example, 2026 has been a relatively wet year, but poor snowpack and low March precipitation has led to stressful river and Bay-Delta habitat conditions in March during the peak of the adult spring-run salmon migration from the ocean.  Delta inflow was too low and water temperatures too high from mid-March to early April in 2026, almost as poor as drought year 2022 (Figures 6 and 7).  This problem led the Bureau of Reclamation to release a pulse flow from Shasta Dam in early April 2026 to help migrating salmon in the Sacramento River and its tributaries.

Solutions

The improvement of reliably robust runs of spring-run Chinook salmon is bound up in ongoing debates on how to manage Butte Creek salmon and their habitat.  Resource enhancement funds are scarce.  There is significant mitigation funding available from the PG&E 2023 flume failure that could play an important role.  More on solutions in upcoming posts.

Figure 1. Current distribution of spring-run Chinook salmon as reported by CDFG, 1998.

Figure 2. Butte Creek spring-run salmon escapement estimates by surviey 2001-2025. Source: CDFW.

Figure 3. Butte Creek water temperature and streamflow at USGS BCK-gage near Chico Feb-Oct 2020. Water temperatures above 18-20C are stressful to migrating and holding adult salmon.

Figure 4. Butte Creek water temperature and streamflow at USGS BCK-gage near Chico Aug 2021 to Jun 2022. Water temperatures above 18-20C are stressful to migrating juvenile salmon and holding adult salmon.

Figure 6. Flow in the Sacramento River at Freeport at the entrance to the north Delta in spring 2022-2026. Red line is recommended minimum Freeport flow. Source: CDEC.

Figure 7. Water temperature(F) in the Sacramento River at Freeport in the north Delta in spring 2022-2026. Red line is recommended maximum Freeport water temperature for spring salmon migrations. Source: CDEC.

Bay-Delta Conditions – Early Spring 2026

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Figure 1. Sacramento River system and major water gaging locations in red.

Figure 1. Sacramento River system and major water gaging locations in red.

Dry and Warm Beginning in March

The end of winter 2026 brought dry conditions to the lower Sacramento River and Bay-Delta (Figure 1). What had been wet-year-type conditions in early March at Wilkins Slough (WLK) and Freeport (FPT), and high Delta outflows (DTO), had become dramatically drier by late March (Figures 2 and 3). The lower flows and dry warmer weather brought warm water temperatures stressful (>65ºF) to many of the Delta’s native juvenile fish (smelt, salmon, steelhead, and sturgeon) that concentrate in the lower Sacramento River and the Bay-Delta in early spring.

Reservoirs were holding back what remained of the winter snowmelt (Figure 4), putting unnecessary stress on this year’s fish reproduction. Minimum flows should have been 10,000 cfs at Wilkins Slough, 20,000 cfs at Freeport (below inputs from the Feather and American Rivers), and 10,000 cfs Delta outflow (see Figure 1 for locations).

Delta exports were moderate but falling from 8000 cfs to 5000 cfs during March (Figure 5). With falling Delta inflows and dry and warming conditions, central and southern Delta water temperatures also increased to stressful levels (reaching 70ºF, Figure 5). The moderate exports decreased outflow and increased Delta water temperatures.

Many of the naturally produced juvenile salmon had passed into the Delta by early March (Figure 6) and began showing up in Delta export salvage (Figure 7).  Millions of Sacramento River hatchery salmon were released in late March and began showing up in Delta export salvage facilities (Figure 8).  These fish also suffered from the low flows and related stress-level water temperatures.

Wet and Cool April

Wet and cool weather returned to the Central Valley in April.  Reclamation also released a flow pulse from Shasta Reservoir into the Sacramento River to help salmon migrations (Figure 9).  Benefits of the flow pulse came late to the problem but will likely provide benefits further into the spring.

Figure 2. Sacramento River daily average streamjlow and water temperatures, and Delta outflow to the Bayin early spring 2026. Orange, green, and blue lines are recommended minimum daily-average flows for Freeport, Wilkins Slough, and Delta outflow. Red line is the sress-level for water temperature at Wilkins Slough and Freeport for juvenile Delta native fish.

Figure 2. Sacramento River daily average streamjlow and water temperatures, and Delta outflow to the Bayin early spring 2026. Orange, green, and blue lines are recommended minimum daily-average flows for Freeport, Wilkins Slough, and Delta outflow. Red line is the sress-level for water temperature at Wilkins Slough and Freeport for juvenile Delta native fish.

Figure 3. Delta outflow and Sacramento River channel flow below rhe Delta Cross Channel (GES) along with west Delta water temperatures at Antioch (ANH), Rio Vista (RVB), and Emmaton (EMM) in early spring 2026.

Figure 3. Delta outflow and Sacramento River channel flow below rhe Delta Cross Channel (GES) along with west Delta water temperatures at Antioch (ANH), Rio Vista (RVB), and Emmaton (EMM) in early spring 2026.

Figure 4. Streamflow and water temperature from the lower Feather River at Gridley (GRL) and American River at Fair Oaks (AFO) in early spring 2026.

Figure 4. Streamflow and water temperature from the lower Feather River at Gridley (GRL) and American River at Fair Oaks (AFO) in early spring 2026.

Figure 5. Delta exports from state Harvey Banks and federal Tracy pumping plants, San Joaquin River Delta inflow at Mossdale, and water temperatures at the three locations in early spring 2026.

Figure 5. Delta exports from state Harvey Banks and federal Tracy pumping plants, San Joaquin River Delta inflow at Mossdale, and water temperatures at the three locations in early spring 2026.

Figure 6. Catch of juvenile salmon in Knights Landing screw trap along with river flow, water temperature, and turbidity from August 2025 to April 2026.

Figure 6. Catch of juvenile salmon in Knights Landing screw trap along with river flow, water temperature, and turbidity from August 2025 to April 2026.

Figure 7. Export rates and juvenile salmon daily salvage at south Delta export pumping planrs in winter and early spring 2026.

Figure 7. Export rates and juvenile salmon daily salvage at south Delta export pumping planrs in winter and early spring 2026.

Figure 8. Marked hatchery salmon Delta pumping plant salvage and export rates from November 2025 to April 2026. Also shown is net flow in south Delta Old and Middle River channels (OMR) near export facilities.

Figure 8. Marked hatchery salmon Delta pumping plant salvage and export rates from November 2025 to April 2026. Also shown is net flow in south Delta Old and Middle River channels (OMR) near export facilities.

Figure 9. Shasta/Keswick Dam release rates into the Sacramento River near Redding CA in late winter and early spring 2026. Also shown is daily average rate for previous 62 years.

Figure 9. Shasta/Keswick Dam release rates into the Sacramento River near Redding CA in late winter and early spring 2026. Also shown is daily average rate for previous 62 years.

Once again, Sturgeon overlooked in Spring 2026

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Water temperatures are reaching lethal levels (22oC) for the newly spawned sturgeon eggs and fry in the lower Sacramento River. To save this broodyear of sturgeon, resource managers must immediately increase flows in the lower Sacramento River. Right now, those flows are unusually low.

The San Francisco Bay-Delta watershed is home to two native sturgeon species: white sturgeon and green sturgeon. White sturgeon are popular among sport fishers in major rivers and the Bay-Delta. Green sturgeon are less common and are protected under state and federal endangered species laws, making their harvest illegal.

Both species migrate from the ocean or Bay into rivers to spawn—a behavior known as anadromy. Green sturgeon tend to spend more time in marine environments and travel further upstream to reproduce. White sturgeon are larger and sought after by anglers. Both types feed along river and bay bottoms, often attracted by bait that has a strong scent. The introduction of non-native clams has given sturgeon an abundant food source, potentially boosting their growth. However, they are sensitive to warm water and thrive best in cooler, saltier environments below 68°F (20°C).

Spawning poses significant challenges for sturgeon. They use stored energy in late winter and spring to reach clean, cool, fast-flowing rivers with deep, rocky bottoms where they lay sticky eggs. After several days, these eggs hatch. The young fry drift down to the Delta and Bay over about a month, feeding and growing along the way. Their survival depends on river conditions—low flow and warm water can be fatal in dry years. During wetter years, strong currents help them safely reach the Bay.

Once in the Bay, sturgeon can take 10 to 15 years to mature before returning upstream to spawn. Unlike salmon, sturgeon live long lives and can reproduce multiple times.

The frequency of wet years and the quality of Bay conditions both affect how many adult sturgeon persist in the population. Recently, recreational fishing has removed about 5–10% of adults annually. Droughts pose bigger risks—especially to white sturgeon—by warming Bay waters and encouraging algae blooms that deplete oxygen, sometimes causing mass die-offs during the summer.

Measures needed to support sustainable sturgeon populations amidst climate change include maintaining adequate river flows and suitable water temperatures in the Sacramento River, Delta, and Bay. This is especially important during spring and early-summer spawning and rearing periods.

Under current water management, most young sturgeon fail to survive the Delta due to poor flows, high temperatures, predation, and entrainment into water diversions. Summer is a critical season in the Bay, where most sturgeon reside, and healthy conditions are vital. Some years, large tides associated with Super Moons bring warm water into the Bay, triggering harmful algal blooms. Consistent freshwater inflow is necessary to support the food web and keep the Bay cool and oxygenated.

During consecutive dry years, population maintenance involves options like hatchery releases, rescuing stranded sturgeon, and stricter controls on fishing. The top priorities should be protecting breeding adults over 15 years old, ensuring adequate recruitment of younger subadults, and improving the survival of eggs and juveniles. Achieving these goals requires enhanced scientific monitoring and assessment of both the fish and their habitats, as is commonly recommended for other native fish like salmon and steelhead.

The current status of sturgeon is less well documented than other species like salmon, steelhead, smelt, and striped bass. Unlike others, there is no formal recovery plan for sturgeon. There are increasing calls to end the sport fishery and list white sturgeon as endangered. However, some scientists and resource managers argue that more pressing threats should be addressed first, and recommend focusing on gathering data from the fishery and data on population abundance.

In my last post on the sturgeon (February 2026), I hypothesized that the big reason for the unsuccessful sturgeon reproduction in water years 2024 and 2025 was poor conditions in the spring spawning and early rearing reach of the middle Sacramento River.  Water temperatures were above optimal (>65oF) and at times stressful (>68 oF) or even lethal (>72 oF) in spring 2024 and 2025.  Few juvenile sturgeon survive to reach the Delta under these habitat conditions.  This was one of the factors that led the State Water Board and USEPA to set 68 oF as the water quality standard for the Sacramento River two decades ago. This standard is also a condition of the State Water Board water right permits for the state and federal water projects.

Once again, during a relatively wet winter-spring, both the sturgeon and the water quality standard seem to be overlooked (see Figure 1).

To save this broodyear of sturgeon, resource managers must immediately increase flows in the lower Sacramento River. Right now, those flows are unusually low.

For more on white sturgeon science, monitoring, and fisheries management see https://wildlife.ca.gov/Conservation/Fishes/Sturgeon/White-Sturgeon.

Figure 1. Sacramento River streamflow and water temperature at Wilkins Slough in the lower prime spawning reach of white sturgeon in spring 2026.

Figure 1. Sacramento River streamflow and water temperature at Wilkins Slough in the lower prime spawning reach of white sturgeon in spring 2026.

Yuba River Fall-Run Salmon Crash 2016-2025

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The Yuba River Fall-Run Chinook salmon population “crashed” in the last decade.  Yuba River escapement ranged only from 2000-5000 spawners counted per year (Figure 1).  Such low escapements were last encountered only during the Central-Valley-wide crash during the 2007-2009 drought.

The decade-long low escapement reflects the effects of two droughts (2013-15 and 2020-22). Though the 2023-to-2025 escapements have increased slightly1 despite the 2020-2022 drought, the higher escapement reflects the benefit of fishery closures from 2023-2025 (fisheries normally harvest more than 50% of the adult stock).  Yuba escapement also reflects substantial numbers of hatchery strays from other rivers, including the Mokelumne and American River hatcheries, the Coleman hatchery on Battle Creek in some years, as well as the Feather River (Oroville) hatchery.  Small numbers of spring-run Feather hatchery strays from release locations near the mouth of the Yuba on the Feather River are also included.

The highest number of strays in the 2020-2022 period were from one group of Mokelumne River hatchery smolts released in 2018 to Half Moon Bay on the coast south of San Francisco.  The next highest group of strays are from American and Feather hatchery smolt releases to San Francisco Bay.  The trucked hatchery smolts do very well during drought years and thus tend to bias high the Yuba returns from drought years.  That is to say, drought effects on the natural Yuba run are even worse than indicated in escapement estimates.

I categorize the decade-long decline as a “crash” based on the population spawner-recruit (S/R) relationship (Figure 2).  The S/R “curve” generally reflects a positive logarithmic relationship between spawner and recruitment numbers.  The more eggs spawned generally leads to more adult returns three years later.  The S/R ratio, at least in the Central Valley salmon populations, also reflects drought or habitat conditions wherein recruits are generally depressed from density-independent habitat factors like droughts.  The six drought years in the last decade shown in Figure 2 as red dots have led to escapement levels in the lower-left quadrant of the S/R curve – a pattern often referred to as a population crash.

Often it is difficult for a population to recover from that situation because there are not enough spawners (eggs) to get the population out of the hole.  It would take a lot of good years in sequence to make that happen, unless certain actions are taken to accelerate the recovery.  For some suggestions on how this can be accomplished, see my past post on the subject.

Because of the supplementation of recruitment from other rivers and resulting mixed bag of spawners, the Yuba run is not threatened with extinction.  However, in its present state, its poor contribution to the commercial and recreational fisheries is a problem.  The Yuba is a magnificent salmon river that should contribute more salmon.

Figure 1. Yuba River Fall-Run Chinook salmon escapement estimates 1953-2024.

Figure 2. Yuba River Fall-Run Chinook salmon spawner-recruitment relationship wherein recruits are related to recruits three years earlier. Red dots represent escapement years where two years earlier it was a drought year during rearing and outmigration.