Category Archives: Northern California

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

Sacramento River Salmon Redd Dewatering – Fall 2025

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I have previously reported on the dewatering of fall-run salmon redds in the upper Sacramento River near Redding during the early fall spawning season. Redd dewatering has a significant negative effect on salmon egg and fry production that translates to lower annual escapement and significantly contributes to the multi-decade decline in the population (Figure 1).

Figure 1. Escapement to the upper Sacramento River natural spawning area 1952-2024.

October is the peak in the fall-run Chinook salmon spawning season (Figure 2).  During early November 2024, the Bureau of Reclamation reduced Keswick Dam releases from the October average of 7000 cfs to 4000 cfs.  The flow reduction reduced water levels in the upper river spawning grounds below Keswick Dam from approximately the 11-ft water surface elevation (stage) to about the 8.5 ft level, a drop of about 2.5 feet.  In 2025, nearly identical flow management led to the same redd dewatering conditions (Figure 3). With most of salmon redds constructed in the 1-to-3 ft depth range, most were dewatered or only slightly watered and thus susceptible to high-egg-mortality conditions (low flow, warm water, low oxygen, and sedimentation).

The flow management strategy was also employed in recent wet years 2017 and 2019, although a more benign strategy was employed in historical wet year 2011 (Figure 4).  The issue has attracted inter-agency study and mention, but actions necessary to reduce the problem have been limited.

Figure 2. Stage and water temperature in the Sacramento River below Keswick Dam in fall 2024. Grey box denotes period when most fall run salmon spawn in the upper Sacramento River.

Figure 3. Stage and water temperature in the Sacramento River below Keswick Dam in fall 2025. Grey box denotes period when most fall run salmon spawn in the upper Sacramento River.

Figure 4. Stage and water temperature in the Sacramento River below Keswick Dam in fall of wet years 2011, 2017, and 2019.

Klamath Dam Removal is Complete – How well did it go?

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The final steps in Klamath River dam removal are complete, and the first salmon has migrated upstream into the dam-removal reach in over 100 years.  The four reservoirs were drained last winter and the dams removed this summer.  The river is now free in its natural channel. Two dams remain up at Klamath Lake (Keno and Link dams – not part of the project), but the lower four hydroelectric project dams – three in Oregon and one in California – are gone.  With the demolition of the last of these lower four dams this summer, the Klamath is running free from its headwaters in southeastern Oregon to its mouth in the Pacific Ocean on Yurok tribal lands in northwestern California.  Hundreds of miles of spawning grounds are open to Chinook salmon, Coho salmon, and steelhead for the first time in more than a century.

The dam-removal process was not without problems, although these problems were generally foreseen in planning and permitting.  First was the reservoir draining process this past winter, when the reservoirs were drained, from mid-January to mid-February.  In the four-dam reach and in the Klamath River downstream, high suspended fine sediment and low dissolved oxygen were problems, though determined of limited risk to the few salmon and steelhead in the river at that time.  However, the Assisted Sediment Evacuation project element (Figure 1) continued past its prescribed end date of March 15 into early April, extending the presence of lethal levels of suspended sediment into the early juvenile salmon and steelhead emigration season from tributaries, a season that includes March.  Lethal levels of suspended sediment extended downstream over 100 miles as far as Orleans (Figures 2 and 3).

Subsequently, during the summer, dam infrastructure was removed to provide full salmon passage past the dam sites.  Low flows necessary to access the dam sites for material removal, and high summer air temperatures, resulted in very warm water temperatures beginning in July.  Removal of coffer dams and further Assistant Sediment Evacuation at the dam sites (Figure 4) led to the return of lethal sediment levels in the river below Iron Gate (see Figure 2).  On three days, dissolved oxygen below Iron Gate reached zero. 

Though approved by the project technical team, the high suspended sediment level through September likely hindered a major portion of the fall-run Chinook salmon run up the Klamath River (Figure 5).  Only 60 adult salmon were reported at the Shasta River trap as of early October, by which time daily numbers are usually in the hundreds.  Numbers at other traps at other tributaries were even lower, which perhaps explains why only one salmon has been seen at the new sonar station above the Iron Gate Dam site.

With the cessation of Assisted Sediment Evacuation at the end of September, the hope is that suspended sediment levels will return to the low pre-summer levels and fall-run Chinook salmon will recommence their migration upriver.  The river should be clear for late fall and winter runs of coho salmon and steelhead. 

The use of Assisted Sediment Evacuation in winter and early spring, and then again in late summer, will remain controversial, if only in that it was applied under an extended time frame from the original planning and permitting documents.  The summer application was certainly a surprise to local stakeholders,1 who were shocked by the extent and duration of the muddy and smelly river conditions.  A condition of zero dissolved oxygen for 50 miles below Iron Gate dam for two days in September was not approved under the permits issued by the state or federal governments.

In my opinion, the initial and final evacuation of muddy sediment should not have been implemented by using excavators to dump sediment directly into the river.  A better option would have been natural removal by winter storm events that would have provided a much higher dilution factor and would have had a better chance for a non-lethal concentration of suspended sediment.  Furthermore, more of the sediment should have been removed or stored in upper terraces and not allowed to enter the river.

The NOAA Fisheries final assessment of the dam removal effort failed to acknowledge the problems and potential consequences of the spring or summer events. 

“Heavy equipment removed the final obstacle separating the Klamath River from the Pacific Ocean on Tuesday. The reconnected river was turbid but remained safe for fish after crews took steps to avoid erosion and impacts to water quality.”  The river was not safe for salmon or steelhead for over 100 miles downstream.

“Crews used a strategy of releasing sediment and organic material that muddied the river but avoided a decline in dissolved oxygen that could have otherwise harmed fish.”  Untrue.  Both dissolved oxygen and suspended sediment levels were lethal.  Hopefully, many fish were able to avoid these conditions.

Figure 1.  Photo of Assisted Sediment Evacuation process from Iron Gate Reservoir in March 2024.  (KRRC video screengrab)
Figure 2.  Turbidity (as measured in FNUs) in lower Klamath River in 2024.  (Karuk water quality data). See Figure 3 for locations.  Red line is approximate lethal concentration for salmon.
Figure 3.  Lower Klamath River USGS water quality sampling stations.  (source: USGS)
Figure 4.  Assisted Sediment Evacuation associated with the removal of Copco No. 1 Dam cofferdam on August 14, 2024.  The mainstem Klamath flow is coming from bypass tunnel in upper center of photo. 
Figure 5.  Timing of fall-run salmon return (daily counts) to the lower Shasta River weir-trap in years 2017-2020.  (CDFW data)
  1. See Facebook (Klamath River & Dam Removals) ↩

Park Fire – Spring-Run Salmon’s Worst Nightmare

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The fire that started on July 24 has burned most of the lower foothill and middle reaches of the affected streams as of August 8th.  It is now actively encroaching on the mountain spawning reaches of Mill and Deer creeks on the south slopes of Mt Lassen, the two most important of the affected spawning streams (see maps below).  It will likely slow only when it reaches the boundary of the 2021 Dixie Fire and its lower levels of fuels.

Map of Park Fire in northeast Sacramento Valley dated 8/3/2024.  Red arrows indicate further fire growth as of 8/6, mainly in the upper Mill and Deer creeks watersheds.  Green stripes indicate spring-run salmon summer holding and fall spawning reaches.

Spring-run salmon populations in the Central Valley, including the core Battle, Mill, Deer, and Butte Creeks populations, are at recent historic lows.  It is essential to rehabilitate previously burned watersheds as soon as possible.  The California Department of Fish and Wildlife should expand the Deer Creek Spring-Run Conservation Hatchery Program begun in 2023 at UC Davis to include the other spring-run salmon streams in the Sacramento Valley. 

At the same time, it is important to attack the causes of poor survival of juveniles migrating to the ocean and poor survival of adults returning to the spawning grounds.  In this regard, comments on the Environmental Impact Statement for the Long-Term Operations of the Central Valley  Project and the State Water Project are due on September 9.  Operations of these water projects play a major role in the survival of Central Valley salmon to and from the ocean.  With the acceleration of climate change, it is important to re-evaluate the present and future effects of these water projects and potential operational changes to protect salmon under this new climate change baseline.

For more on Mill and Deer creek salmon see:  https://www.facebook.com/CaliforniaDFW/videos/spring-run-chinook- salmon/306327998810027/

Park Fire active zone moving northeast in the upper Mill Creek watershed on August 8th, 2024.  CALFIRE hopes to stop the Park Fire advance at highways 32/36 and the boundary of 2021 Dixie Fire (see next map).

Park Fire active zone moving northeast in the upper Mill Creek watershed on August 8th, 2024.  CALFIRE hopes to stop the Park Fire advance at highways 32/36 and the boundary of 2021 Dixie Fire (see next map).

Western boundary (extent) of Dixie Fire in summer 2021.

Klamath River Update – July 2024

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It is the first summer without the reservoirs on the Klamath River.  Upper river flows at Iron Gate are now at summer lows (900 cfs, Figure 1).   The flow, water temperature, and turbidity in the river without the reservoirs (the dams have not all been removed) is shown in the following figures.  Two major concerns are sporadic turbidity events from dropping flows and higher water temperatures that are a consequence of unshaded former reservoir reaches and loss of cold-water dam releases.

Extensive gaging data are available for the lower Klamath River from the USGS and Karuk Tribe (Figure 2).  The focus here is on the reach below the four-dam-removal project where the dams were drained in early 2024, leaving the river free-flowing.

Late spring and early summer gage data show the upper reaches below Iron Gate had the warmest water in 2024 (Figures 3-5).  Water temperatures reached 25oC/77oF, lethal to salmonids.  Further downstream, water temperatures were gradually cooler as the river progressed toward the mouth, generally remaining in the 68-70oF maximum range after receiving cool tributary water and cooler air temperatures.  Further upstream above Iron Gate, water temperatures were similar those immediately below Iron Gate (Figure 6).

Prior to dam removal, the upper reaches below Iron Gate had the lowest water temperatures in 2022 and 2023 (Figure 7 and 8), reflecting the release of cold water from the bottom of Iron Gate Reservoir.  Without this source of cold water, the upper reaches are now significantly warmer in late spring and summer. 

Because the water temperatures were similar in 2024 above and below the former Iron Gate Reservoir (see Figures 4 and 6), there seems to be little warming in the unforested former Iron Gate reservoir reach.  The upper reach of river below Iron Gate Dam now generally reflects historic warm water characteristics of the 6-dam project reach between Klamath Lake and Iron Gate Dam.  Future riparian forest restoration of the three former reservoir reaches may lead to some cooling of the upper river in the future.

Finally, the drop in river flow in early July 2024 (see Figure 1) appears to have caused additional reservoir-footprint erosion and scouring, leading to high turbidity levels below Iron Gate (Figure 9).  Such turbidities like the warm water are generally lethal to salmonids.

Figure 1.  Upper Klamath River flow at Iron Gate gage in June and early July 2024.

Figure 2.  Lower Klamath River gauging stations from Klamath Lake downstream to mouth.  Blue marker denotes gage below JCBoyle Dam.  Numbers in green and yellow circles denote multiple gage locations.

Figure 3.  Water temperatures in lower Klamath River in June 2024.  Iron Gate Dam is uppermost location and Turwar Gage is lower-most location near mouth.  Note greatest water temperatures were recorded from the two uppermost reaches:  Iron Gate and Walker Bridge.

Figure 4.  Water temperature recorded at Iron Gate gage 6/15-7/7 2024.

Figure 5.  Water temperature recorded at Walker Bridge gage 5/20-7/7 2024.

Figure 6.  Water temperature recorded at Fall Creek gage 6/1-7/7 2024.

Figure 7.  Water temperatures in lower Klamath River in June-July 2022.  Iron Gate Dam is uppermost location and Turwar Gage is lower-most location near mouth.  Note lowest water temperatures were recorded from the two uppermost reaches:  Iron Gate and Walker Bridge.

Figure 8.  Water temperatures in lower Klamath River in June-July 2023.  Iron Gate Dam is uppermost location and Turwar Gage is lower-most location near mouth.  Note lowest water temperatures were recorded from uppermost reach: below Iron Gate.

Figure 9.  Turbidity (suspended sediment) concentrations measured at Iron Gate Gage in 2024.  Note original reservoir drawdown and subsequent reservoir sediment deposit erosion January-