In an August 1, 2024 post, I updated the status of water quality in the Klamath River during the 4-dam removal project. I had several concerns: sporadic turbidity events, dropping flow rates, and higher water temperatures; all of these concerns had been acknowledged in the project’s planning documents.
Final steps to remove dams on the Klamath River in summer 2024, including dumping additional sediment from exposed reservoir reaches, has again raised concerns about water quality in the Klamath River. The problem is that, this time, fall-run Chinook salmon runs to tributary streams like the Scott and Shasta Rivers are at their peaks. Such water quality degradation events, especially during the late summer fall-run Chinook migration season, would normally be considered violations of state and federal water quality standards. However, these events were expected in the monumental 4-dam removal project on the lower Klamath River.1
Excerpts from NMFS biological opinion (p. 164 of NOAA 2021):
“Effects associated with reservoir drawdown (i.e., SSC and dissolved oxygen impacts) will affect all populations of SONCC coho salmon that utilize the Klamath River during some portion of their life history cycle, while the other short-term effects associated with dam removal, construction, and restoration will primarily be limited to individuals from the Upper Klamath population. Therefore, the proposed action is likely to adversely affect coho salmon from the Upper Klamath River, Shasta River, Scott River, Middle Klamath River, Salmon River, Lower Klamath River, Upper Trinity River, Lower Trinity River, and South Fork Trinity River population units in the short term.”
“Behavioral effects resulting from elevated suspended sediment include alarm reactions, avoidance, and reduced feeding. Cederholm and Reid (1987) found that juvenile coho salmon prefer low to medium concentrations of suspended sediment, and that juvenile coho salmon prey capture success significantly declined at concentrations of 100 to 400 mg/l. Salmonids have been observed to prefer clear over turbid water (Bisson and Bilby 1982), and move vertically near the water surface (Servizi and Martens 1992) and/or downstream to avoid turbid areas (McLeay et al. 1984; McLeay et al. 1987). More than six weeks of exposure to concentrations of 100 mg/L reduces feeding success, reduces growth, causes avoidance, and displaces individuals (Spence et al. 1996).”
“Suspended sediment contributes to turbidity, which also can have adverse effects if excessive. Bisson and Bilby (1982) found that juvenile coho salmon avoided water with turbidities of 70 Nephelometric Turbidity Units (NTU).”
The problem this summer has been the removal of coffer dams, other remaining infrastructure, and further remaining reservoir sediments (Figure 1). The release of oxygen-demanding sediment caused critically low dissolved oxygen levels for several days in late August, from the Iron Gate gage (Figure 2) downstream 30 miles to the mouth of Walker Creek (Figure 3, about midway between the mouths of the Scott and Shasta Rivers). Highly stressful levels of suspended sediment (>300 FTUs) occurred for nearly a week, and also occurred sporadically through September, downstream as far as Orleans (Figure 4). With water temperatures in the river falling through September (Figure 5), the annual run of adult fall-run Chinook salmon was likely occurring (Figure 6).
The risks to coho salmon and juvenile salmon were likely minimal in summer. The coho salmon run occurs in November-December. Juvenile coho and Chinook salmon juveniles begin moving out of the tributaries with the first significant fall or winter rains. The rains will also bring erosion of accumulated sediment that could cause stress and mortality this winter and spring, factors that were also anticipated in project planning/permitting documents.
Figure 1. Iron Gate gage turbidity recordings 8/22/24 to 9/22/24.Figure 2. Iron Gate gage dissolved oxygen measurements in 2024. Note zero levels recorded during initial dam breaching in late January and Iron Gate cofferdam removal on August 28.Figure 3, Dissolved oxygen recordings in Klamath River in summer 2024.Figure 4. Turbidity recordings in Klamath River in summer 2024.Figure 5. Water temperatures in Klamath River May-September 2024.Figure 6. Fall-run Chinook timing to lower Shasta River in 2016.
“The breaching of the cofferdam at Iron Gate released fine sediment – predominantly dead algae – from the former reservoir footprint. As this sediment has moved downstream, there have been impacts to water quality in the reaches below Iron Gate. The largest of these impacts has been increased turbidity levels and large reductions in dissolved oxygen concentrations immediately downstream of the Iron Gate dam site. For decades there have been enormous seasonal blooms of toxic blue green algae in the reservoirs behind the Iron Gate, Copco No. 1, and J.C. Boyle dams and millions of cubic yards dead algae settled to the bottom over years. While most of this dead organic matter was flushed downstream during the drawdown when the reservoirs were drained back in January, some remained on the backside of the Iron Gate cofferdam. That sediment was released earlier this week when the river was returned to a free-flowing state with the breaking of the cofferdam.
“As this oxygen starved dead organic matter is flushed out from the former reservoir into the river, it absorbs the oxygen in the water. That leads to a drop in available oxygen for aquatic animals in the river, including fish.
“KRRC continues to monitor the impacts of this pulse of sediment. The intensity of the impacts to water quality has been decreasing as the turbid water moves downstream. The dips in dissolved oxygen have been smaller and shorter in the downstream reaches of the river, as freshwater from tributaries dilutes the sediment in the river.
“Crews monitoring the situation have observed some mortality among fish in the river reach directly below Iron Gate Dam. These impacts are unfortunate but expected following such a drop in dissolved oxygen. Fortunately, we have not seen mortality in returning adult salmon, currently making their way upstream. Crews will continue to monitor the situation, and we will share information as we learn more.
“This is precisely the kind of temporary negative impact that was anticipated and fully analyzed by state and federal regulatory agencies overseeing the dam removal. Scientists and other experts determined that any short-term pain associated with the dam removal activity was worth the long-term gain for the health of the river, native fish species, and surrounding communities. After the Iron Gate cofferdam was broken last week, some parts of the cofferdam remained in place to allow for the removal of diversion infrastructure. KRRC will remove this remaining piece of in-river infrastructure before the project is completed later this month. Following the breach, a significant amount of impounded sediment began to move down-river, but some remains on the backside of the cofferdam segment still in place.
“Taking guidance from the project’s Fisheries Coordination Team, which is comprised of NOAA Fisheries, Karuk Tribe, Yurok Tribe, California Department of Fish and Wildlife, US Geological Service, US Fish & Wildlife Service and other fisheries and water quality specialists, KRRC will implement an assisted sediment evacuation plan in the coming days. Utilizing a long arm excavator to stir up the material, much of the remaining accumulated sediments will be sent downstream slowly in the coming weeks, ahead of the final removal of the what’s left of the Iron Gate cofferdam later this month. The goal of this activity is to remove as much of this material as possible gradually to limit water quality impacts later in the month, when adult salmon will be coming through the river reach directly below Iron Gate. While we have seen adult salmon already entering the river, they are currently downstream of the areas that were most affected by the sediment that has been released with the breaching of the Iron Gate cofferdam.
“The sediment, mostly consisting of dead algae, is non-toxic, and is too water-logged to effectively be removed from the river using machinery, so a gradual release was determined to be the best option to protect incoming salmon. As the sediment is gradually released downstream over the coming weeks, KRRC, Tribes, and public agencies will carefully monitor river conditions to ensure the dissolved oxygen levels are kept at habitable conditions for fish. Because the Klamath is, in general, a sediment-heavy system, it is important to note that Klamath River salmon are adapted to survive with a certain degree of sediment in the river as they migrate upriver to spawn.
Communities down river can expect turbid (murky) conditions to continue for the coming weeks. These conditions are temporary, and this controlled sediment removal is an important activity to protect the salmon currently making their way upstream. You can see the targeted sediments for removal below. They are darker in color than the dam material and are upstream of the cofferdam on the right hand side of the image.”
I fully support implementation in 2024 of the Fall X2 action prescribed in the biological opinion for Delta smelt. Furthermore, I support maintaining Delta Outflow at 10,000-12,000 cfs year-round[1] in all water year types to protect Delta smelt and longfin smelt. The compelling reason for such action is to maintain the low salinity zone (LSZ) and the head of that zone downstream of the confluence of the Sacramento and San Joaquin rivers in the western Delta, on an average-daily or tidally-filtered basis (Figures 1 and 2).
Such action will require approximately 10,000-12,000 cfs daily average Delta outflow (Figure 3). Such action would ensure the LSZ is maintained downstream of the Delta within Suisun Bay, Suisun Marsh, and Montezuma Slough – conditions necessary to protect listed Delta and longfin smelt populations. Otherwise allowing the LSZ to enter the Delta subjects the pre-spawn staging of the smelts (Figures 4 and 5) to entrainment into Delta water exports and the vagaries of Delta habitat (poor water quality and food supply, as well as lower turbidity and higher predation). Failure to maintain the X2 in Suisun Bay below the confluence also undermines the integrity of the LSZ critical habitat of the smelt in future months. My conclusions are further amplified in prior comments in support of the Fall X2 (https://calsport.org/fisheriesblog/?p=2940).
In conclusion, failure to implement Fall X2 will have an adverse impact on Delta smelt and longfin smelt and their critical LSZ habitat.
Figure 1. Water temperature and salinity of eastern Suisun Bay near Pittsburg June-September 2024.
Figure 2. . Hourly and tidally filtered salinity of eastern Suisun Bay near Collinsville August-September 2024. Note X2 is approximately 2 psu (ppt)
Figure 3. Daily Delta outflow August-October in 2023, 2024, and average 2014-2023. Note application of Fall X2 in September 2023 (> 8,000 cfs).
Figure 4. October 2023 fall midwater trawl survey catch of longfin smelt.
Figure 5. October 2011 fall midwater trawl survey catch of Delta smelt.
[1] Except in critical drought years when exports are minimum due to minimum available water supply.
In a June 2024 post, I hypothesized factors controlling the white sturgeon population in San Francisco Bay-Estuary. I concluded the major factor controlling the adult stock size was periodic recruitment of juvenile sturgeon from successful spring spawning and early rearing in the lower Sacramento River. Successful recruitment only occurs in the wettest years, when there are higher streamflows and cooler water temperatures.
Recruitment of young white sturgeon in significant numbers has only occurred in three years since 2010: 2011, 2017, and 2023. Recruitment in 2024, an above normal water year, is likely to be poor. Production of young sturgeon is likely of function of attraction of spawners from San Francisco Bay (to high winter-spring river flows – good in 2024), good spawning conditions (streamflow and water temperatures – good in 2024), and good early rearing and transport conditions in the lower Sacramento River and the north and central Delta (streamflow and water temperatures – poor in 2024).
The adult spawning stock size may not be as important as spawning conditions, given strong recruitment in wet year 2023 under a very low stock abundance (observed Bay die-off in summer of critical drought year 2022).
There are a number of measures that hold promise to protect and enhance adult stock numbers, recruitment, and survival of white sturgeon.
Spawning Conditions
Flows in the lower Sacramento River (Wilkins gage) should be 8,000 to 10,000 cfs or higher in spring.
Flow in the lower Sacramento River (Wilkins Slough) should be at least 8,000-10,000 cfs.
Early Rearing and Juvenile Transport
Sacramento River inflows to the Delta should be at least 20,000 cfs in spring.
Flow from the lower Sacramento River into the Delta (Freeport) should be at least 20,000 cfs in spring and early summer (April-July).
Delta Conditions
The net flow in the lower Sacramento River channel downstream of the entrance to Georgianna Slough should be at least 10,000 cfs in spring and early summer (April-July). This will require total Delta diversions, including local agricultural diversions and exports by the State Water Project (SWP) and Central Valley Project (CVP), to be limited to approximately 10,000 cfs.
Flow in the lower Sacramento River in the Delta below Georgianna Slough should be at least 10,000 cfs in spring and early summer (April-July).
White sturgeon recruitment is best assessed at fish salvage facilities at the water project south Delta export pumps. Young sturgeon produced in the lower Sacramento River reach the Delta in early summer as shown here in 2023. Note the high export levels of 20,000 acre-feet per day (approximately 10,000 cfs; in this figure, SWP exports are shown behind CVP exports).
Bay Conditions
Delta outflow to the Bay should be at least 10,000 cfs from spring to early fall (April-October).
Delta outflow to the Bay (DTO) and Rio Vista water temperature May-Oct, 2021-2024. Recommended Delta Outflow is a minimum 10,000 cfs (purple line).
Minimize Sturgeon Adult Harvest and Pre-Adult Fishing Mortality
Sturgeon sport fishing should be limited to the Bay only, with catch-and-release regulations, with the following further considerations:
Fishing for sturgeon should be closed in the east Bay or north Bay if daily maximum water temperatures are expected to exceed 65ºF (18ºC) in any open water portion gage locations in either Bay portions (possible from late spring through early fall).
CDFW could allow limited harvest through short-term regulations, limited by slot (length range) and number. (Note that slot harvest in 2024 would allow a small harvest of broodyear 2011 white sturgeon, the most recent abundant broodyear in the adult population).
Under such restrictions, the effects of sport fishing on the sturgeon population would be minimal.
In addition, sturgeon collected at south Delta export salvage facilities should be transported to an appropriate location in the Bay for release (presently, they are released in the Delta).
Population abundance and recruitment of white sturgeon are mainly a function of annual Central Valley hydrology (river flow), with abundant juvenile production occurring only in the wettest years. Past harvest has only involved a small percentage of the adult population, while watershed hydrology has orders of magnitude greater effect on recruitment and eventual adult population abundance.
Allowing a limited fishery could also help in continuing to assess the health of the population. Sport fishers should be asked to contribute important information on the sturgeon they catch.
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.
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.
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-
