Flow Variability in the Trinity River

Aaron Martin [Yurok Tribal Fisheries Department]

Imagine a winter storm brewing in the west, clouds accumulating over the mountain peaks dropping a dusting of snow and at lower elevations dripping down as rain. Waters accumulate and funnel toward low points in steep terrain running down stream paths catching sediment, leaves, and branches and delivering them into the tributaries of the Wild and Scenic Trinity River. Depending on the amount of precipitation or snow melt, creeks can daintily deliver cool mountain waters with smaller sediments while larger rain events can powerfully move tree logs and large rocks.

Between 1960 and 2022, when this wild pulse of storm-fed tributaries finally converged with the Trinity River, something peculiar happened; the mainstem did not match the same force of its smaller tributaries. The river’s flatlined flow left debris delivered by the tributaries stacked and settled at their mouths. In the wet winter of 2022-’23, the community witnessed Deadwood Creek deliver a plume of sediment from its wildfire-scarred upper reaches after a significant rain. The plume settled on a large group of salmon redds at the mouth of the creek, and the Trinity River, at its baseline winter flow of 300 cfs, couldn’t mobilize the sediments. The embryos developing in redds at the mouth of the Deadwood Creek likely died by suffocation.

As you are probably aware, the Trinity River has two dams which hold back waters from its upper watershed. In the absence of flow from those tributaries, the river then must rely on two hydrologic sources for river health: downstream tributaries and restoration flow actions released from the dam. Restoration flows have been managed by the Trinity River Restoration Program since 2004 and until quite recently, flow amounts during winter months were managed to maintain a consistent low flow (300 cfs) from October 15 through mid-April. Management was designed this way because the science of how flow influences the ecology of the river wasn’t as far along as the physical river sciences, and further, the water year type which establishes the volume of restoration flow is not determined by the California Department of Water Resources until April 15. Based upon that water year determination, program staff develop a hydrograph for its spring restoration release which intends to mimic an important ecological function of mountainous river systems – the snow melt flood.

As described in the first paragraph, the snow melt flood moves mountains, well the loose parts anyway. High flows during melt events benefit the river in form by moving sediments, logs and rocks which are critical in building habitat for salmonids. Logs slow upstream current, allowing migrating fish to rest and providing cover from predators. Rocks create oxygenation in riffles and provide nesting salmonids a place to dig their redds when spawning. Sediments, when settled and in healthy amounts, encourage proper algae and thus hatches of bugs, which feed fish on their path of migration.

With the snow melt restoration release the Trinity River began to heal from decades of dam-regulated flows. Data shows that the Program has been successfully sending more young fish to the ocean suggesting that habitat is increasing with more water in the system (Pinnix et al, 2022), but adult fish returns have not met expectations and scientists wanted to know why. In the mid-2010’s the Program began to explore the use of flows during winter months. A significant portion of rain events that trigger tributary flows happen from December to April and flows below the dam don’t match that pattern. Studies commenced on temperature, salmonid growth, food availability, habitat availability, redd scour, and geomorphic and hydrologic benefits of current and potential flow practices. The results from these studies became clear and culminated in the Trinity River Winter Flow Project report (Abel et al., 2022). The research led to a proposal of using some of the restoration flow volume earlier in the year by synchronizing a dam release with a winter storm between December 15– February 15 and then providing the river with an elevated base flow between February 15 and April 15; the balance of the restoration water volume would still be used to mimic spring snowmelt in the spring. The authors hypothesize that this change in flow management would more efficiently use the same amount of water to move rock in the river, while also increasing habitat and food availability for young salmon.

When you think about it, it makes sense. All the native species of the Trinity River evolved with winter storm flows, higher winter base flows, spring snow melt and dry hot summers. But for the past 56 years, water dispersal from the dam has been flipped and has largely disregarded vital variability in flow patterns outside of the spring and early summer. Key floodplain habitat that was once inundated for months during winter and provided an abundance of rearing areas and food production to Trinity River fish has been lost, unless flow patterns change. Catch data from downstream screw traps show that inundation of that rearing habitat does not occur until most juvenile salmonids are downstream of the restoration reach (Petros et al. 2017), meaning most juvenile salmon don’t have a chance to use all that habitat that has been created by restoration projects in the last 18 years, unless flow patterns change. We are also learning that water released from the dam can be so cold that it slows the growth of juvenile salmon and that the right temperatures and abundant food will translate into faster growth for salmonids (Lusardi et al. 2019).

Young fish need diverse habitats, appropriate temperatures and abundant food to thrive and survive as they travel down the river to the ocean. More natural flows, including winter floods, increased winter base flows, and spring snow melt better support a healthy ecosystem that many species depend upon. The system is a balancing act of physical processes like flow, seasonality, and a vast network of species that rely on each other to thrive.  The Trinity River Restoration Program is looking to give that power back to the ecosystem so that our cherished fish of the Trinity can be armed with bigger, healthier bodies when they meet the challenges of their harrowing migration to and from the ocean.

Highlights from the Trinity Management Council September Meeting

TMC Partnership Ring
TMC Partnership Ring

The last quarterly meeting of Fiscal Year 2023 was held in Weitchpec, CA on Wednesday and Thursday last week. Typical of the start to the first days agenda, is an approval of the June meeting minutes, however this was moved to later in the day due to a request from Justin Ly [National Marine Fisheries Service] who noticed an inconsistency between how a motion had been characterized and requested time to edit prior to approval. Following this decision, the TMC requested questions and discussion of non-agenda items and then moved into TRRP program updates. The TRRP Executive Director’s report can be downloaded by clicking here.

Comments on non-agenda items brought questions from the public regarding recent social media posts of non-native/introduced fish released into the Trinity River at a rehabilitation site in Junction City. Mike Dixon, [Trinity River Restoration Program] commented that office staff saw a social media post with a bullhead catfish and noted that bullhead are introduced as a sportfish into Trinity Lake and do occur in the Trinity River. The system does not have a robust population and their chance of surviving in the conditions of the river are slim. Interestingly Kyle De Juilio [Yurok Tribal Fisheries Department] also commented that bullhead can be found in the Klamath River as conditions are suitable for them, but they are not known to persist farther up in the Trinity River system. State officials attending the meeting also commented that the State does not have a specific policy regarding introduced game fish.

There were two presentations given to the TMC before and after the lunch hour. Max Ramos [Yurok Fisheries Department] presentation titled Modeling the reestablishment of Coho salmon in Klamath River tributaries following dam removal was postponed due to illness. In his place Kiana Abel [TRRP] presented on FY23 outreach accomplishments and early FY24 outreach plans. Following the outreach presentation, the TMC heard from Dr. Greg Courtice [Applied Ecohydraulics] presented Implications for wildfire-induced fine sediment loading within the Trinity Watershed. Slides from both presentations can be downloaded here: TRRP: Event Details

Post presentations, TMC members held a blind vote to replace the TMC’s vice chair vacancy. Some shuffling with responsibilities at the US Fish and Wildlife Service opened the Board’s Chair position. According to the TMC Bylaws a Chair vacancy mid-service is to be filled by the current Vice Chair and a vote is to be held to fill the open position. The TMC voted to place National Marine Fisheries Service Representative, Justin Ly into the position, he will serve as Vice Chair and Don Bader [Reclamation] will serve as Chair until the December 2024 meeting.

The final agenda item of the first day meeting was a decision item. TMC members voted to select, Dr. Daniele Tonina of the University of Idaho to join the Scientific Advisory Board in an advertised position to focus on hydrology. To learn more about the SAB, please click here.

Day 2 of the TMC quarterly meeting started with regular business in discussing non-agenda items. Thanks were given to the Yurok Tribe for hosting the meeting. There was no request from the public to comment on non-agenda items.

Seth Naman [NOAA Fisheries] reported on the latest synthesis report on temperature in the Trinity River, Synthesizing 87 years of inquiry into Trinity River Temperatures. Please download the report here: Asarian etal (2023) Temperature Synthesis 87 years.pdf

Ken Lindke [California Department of Fish and Wildlife] led the TMC’s final presentation, Water Year 2023 initial findings and WY24 flow recommendation from the TRRP Interdisciplinary Team Work Group. The TMC considered the WY24 flow recommendation from the Flow Work Group and Interdisciplinary Team and Justin Ly [National Marine Fisheries Service] made the following motion: “to approve the IDT’s recommendation to implement winter flow variability for WY24, to timely complete the NEPA process prior to implementation, and to inform the public at least two weeks prior to moving forward with winter flow. In addition, a monitoring plan will be provided to the SAB for their review prior to winter flow variability implementation to assess the effectiveness.” The motion failed 6-2 (TMC bylaws require 7/8 affirmative votes if 8 members are present).

After a discussion of what it meant for the TMC to not send a flow recommendation for the upcoming year to the Department of Interior, Justin Ly [National Marine Fisheries Service] made a second motion to, “recommend that TMC approve beginning October 1, implement 450 cfs baseflow through October 15, then reduce baseflow to 300 cfs from October 16 to April 15.” This motion also failed. The TMC failed to pass the flow recommendation and subsequently failed to pass a motion recommending that DOI implement status-quo winter base flows, so the TMC has not yet made a recommendation to DOI. The winter flow recommendation ruleset does not change flows until December 15, so there is still time for TMC to revisit this issue and make a recommendation to DOI one way or another. If no further guidance is provided by TMC, DOI will have to evaluate its obligations under the law and determine how to proceed.

The TMC will hold their first quarterly meeting for FY24 on December 6 & 7, 2023 at the Shasta-Trinity National Forest Service office in Redding, CA.

Trinity River: August Current Conditions

Trinity River: Current Conditions

River flows continue to be released from Lewiston Dam at the summer base flow of 450 cubic feet per second. Upper and lower river temperatures have continued to trend lower than 2022 and remain “optimal” (50F-65F) for spring salmonids holding in the river. Numbers of fish trapped in the JC weir have gone on a downward trend indicating that spring run steelhead and salmon are working their way up river and the fall run are holding.

River enthusiasts will see a rise in flows due to tribal trust agreements between the Hoopa Valley Tribe and the Bureau of Reclamation. Beginning Aug. 18 flows will gradually increase from the summer base flow of 450 cfs and are expected to reach a peak flow of 2,000 cfs on Aug. 20 before gradually returning to summer base flows later in the week. The Bureau’s official press release can be found here.

The Restoration Program continues work with partners at Oregon Gulch, north of Junction City. The project has moved into phase II which calls for channel reconstruction and in-river work. Trained technicians are on site monitoring turbidity to permitted levels. Anglers and river enthusiasts should expect moderately turbid waters downstream of the site. If traveling on the river, please follow signage as navigation pathways may have changed.

Workers at Oregon Gulch stand near the upper river entrance on August 9 2023. Photo Credit: Kiana Abel, Reclamation

Monitoring of fish health continues throughout the summer at the Junction City weir by several partner agencies. As of August 2, temperatures were recorded between 59F and 62F (in range for optimal temps). Fish trapped at the weir are still showing evidence of past gill infections, however they are “less than trace or healed” and seasonally the infection rate is holding in the 20% range. This is still higher than years past and the fish health alert will be held to a “yellow” cautionary level.

Trinity R a Lewiston CA – USGS Water Data for the Nation
Trinity R a Douglas City CA – USGS Water Data for the Nation
Trinity R AB NF Trinity R NR Helena CA – USGS Water Data for the Nation
Trinity R a Hoopa CA – USGS Water Data for the Nation

Current river flow gauges can be found on our homepage, click here and scroll to the middle of the page.

Trinity River Watershed : Plant Spotlight – August

California buckeye (Aesculus californica)

California Buckeye

California buckeye (Aesculus californica) is a fast-growing species that grows below 4000 feet in dry slopes, canyons, and stream edges. Various species of buckeye grow throughout the world, but this is the only species that grows in California. Here in Trinity County, it seems to prefer the cooler and wetter parts of the region, mostly growing downriver towards Willow Creek or along moist riverbanks. They are a summer deciduous species and start to lose their leaves as early as July, turning crinkly and yellow and creating a seasonal stand-out display amongst the surrounding green riparian foliage.

Described as either a small tree or a large shrub, California buckeyes usually have multiple, gnarled trunks with smooth grey bark. One of the earliest riparian trees to leaf out in the spring, they ornately decorate the still dormant riparian area with large, dark green, palmately compound leaves. Soon thereafter, impressive clusters of whitish-pink flowers explode from the backdrop of tropical-looking leaves. Each cluster is primarily composed of male flowers, but towards the tip are a few functionally female flowers. This means that though each inflorescence contains several dozen blooms, they only manage to produce 1-2 seeds, which are rather large and somewhat resemble chestnuts (hence one of this plant’s common names, “horse chestnut”).

Buckeye seeds are known for being toxic to non-native bees. This is due to a neurotoxic glycoside called aesculin, which causes hemolysis (rupturing) of red blood cells. This not only affects hive species like honeybees – who take the pollen back to the hive and inadvertently poison their own queen – but it also affects humans and fish, causing symptoms like diarrhea, muscle weakness, lack of coordination and even paralysis. Thanks to coevolution, native bees and pollinators are unaffected by aesculin and savor the sweet nectar and pollen.

Native Americans have a cultivated relationship with buckeye seeds. In the Hupa language, the word for buckeye is la:whe’, and the seeds are believed to be a food of the pre-human immortals (k’ixinay). With significant preparation (including repetitive leaching, boiling, and pounding), the seeds become edible as flour or meal, similarly to acorns.

California buckeyes are drought tolerant, fast growing, and highly effective reproductively, making them extremely well adapted to their environment. To propagate some on your own property, simply take a seed and plant it about 1” deep – it will rapidly develop a large and robust taproot and can grow up to 10” a year, making a lovely landscaping attraction.

Veronica Yates, Riparian Ecologist

Hoopa Valley Tribal Fisheries Department, Weaverville

Featured Article – August

This image shows the Bucktail channel rehabilitation site in April 2019, three years after construction. This image illustrates a pond with a beaver dam analogue in the location of a former gravel quarry that is connected to the river by a perennial side channel (lower right), a main channel that reoccupied a channel that filled in after Trinity Dam was completed (top of photo), and an alcove with perennial flow (second channel from top). The variety of water depths, velocities, and temperatures resulting from the project are intended to provide good rearing conditions for all anadromous fish species that may use the site. Photo by A. Martin, Yurok Tribal Fisheries Dept., 2019.

A Brief Introduction to Thermal Ecology of the Trinity River

Rivers, particularly those in Mediterranean climates, are extremely complicated systems (see figure 1). Water temperatures in unregulated rivers vary over time and space. They tend to be warm in the summer, cold in the winter, colder in the headwaters than in downstream reaches, and colder at the bottom of slowly moving, deep pools. Temperatures in tributaries often differ from mainstem rivers and create even more variability in the system. This complexity ‘muddies the water’ when the topic of water temperatures comes up in conversation or when making flow management decisions. To complicate matters more, dams and diversions strongly affect water temperatures, especially how they change over time and space, so river managers have invested heavily [1] in understanding riverine thermal patterns to better maintain water temperatures needed by fish and wildlife.

Figure 1. Reproduced from: J. Eli Asarian, Kyle De Juilio, David Gaeuman, Seth Naman, and Todd Buxton. (2023). Synthesizing 87 years of scientific inquiry into Trinity River water temperatures. 80 p. + appendices. Prepared for the Trinity River Restoration Program, Weaverville, California.

It is well known that native Trinity River salmonids – Coho, spring and fall Chinook, and winter and summer steelhead – generally require ‘cold’ water. However, Trinity River ecology is more complex than that, as salmonid temperature needs vary by species and life stage. When speaking in generalities, there are a few truths. Mortality is likely if daily average water temperatures reach 73°F (23°C) for young and mature salmonids alike, however, if adult salmonids can access cooler water and don’t encounter other stressors they can survive. When salmonids are young and food is unlimited, optimal growth in freshwater occurs between 55°F-65°F (12°C-18°C), and seasonal runs of adult Chinook salmon stop migrating upstream when temperatures exceed about 68°F (20°C). Among salmonids, Coho eggs are the most sensitive to temperature while they develop in the gravel during the winter months. Optimal temperatures range from 36°F-44°F (2.5°C-6.5°C). Survival rates begin to decline at temperatures above 50°F (10°C).

When a river is dammed, water pools behind it and is exposed to sunlight and warm air, and the water inevitably warms.  Water that is too warm directly kills salmon. Conversely, with cooler water, salmonids also have a threshold as low temperatures slow growth and can enhance conditions for some diseases, and mask environmental cues for migration. Since cooler waters do not directly kill salmonids and since the degradation of cooler temperatures affects out migrating young salmon vs adult salmon, managers have been conserving salmon in dam-regulated rivers as cold as possible. Doing this is straightforward: release water from deep in the lake (where water is colder than at the top), and release as much of this cold water as is necessary to keep the tailwater at the desired temperature downstream to the desired point. However, from empirical data, we know that rivers within a Mediterranean climate warm in the summer. In fact, the seminal fisheries investigation on the Trinity River [2] documented summer surface water temperatures of about 80°F (27°C) in the Lewiston area, and simultaneously salmon were present and thriving in this environment. Anecdotal reports from long-time Trinity County residents also suggest that very low flows, “to the point that one could walk across the river”, in places, without getting wet – were frequent and salmonids were able to handle these conditions just fine. Coincidentally, these warmer, slower flows were also needed by other aquatic species that co-evolved with salmonids such as the foothill yellow-legged frog and western pond turtle whom we have seen decline in dammed rivers due to higher summer flows and colder temperatures.

Fish biologists will tout the natural warming of a river found in Mediterranean-climates as a benefit because warm summer waters stop upstream salmon migration. Thermal barriers separate the spring and fall Chinook runs and minimize interbreeding between the runs. This is important because when individuals from these two runs interbreed, their adult offspring are rewired to begin their upstream migration in the hottest months of the summer [3] and depending on the year these re-wired fish can enter into poor to very poor river conditions.

Managers can achieve a cold river by one of two ways. Using the current system they release lots of water (450cfs) from the deep in the reservoir and keep the river cold. This large mass of cold water gradually and uniformly warms as it goes downstream. The second management system would be to release less cold water to promote stratification, and have both warm and cold water in close proximity to each other for a long ways downstream. For many years, public opinion and legal requirements, informed by our limited understanding of how rivers work, has favored the former strategy. In the future, an ever-shrinking water supply, a better understanding of thermal ecology, and perhaps a need to conserve other species along with salmonids, requires each of us to explore the latter.

  1. J. Eli Asarian, Kyle De Juilio, David Gaeuman, Seth Naman, and Todd Buxton. (2023). Synthesizing 87 years of scientific inquiry into Trinity River water temperatures. 80 p. + appendices. Prepared for the Trinity River Restoration Program, Weaverville, California.
  2. Moffett, J. W. and Smith, S. H. (1950) Biological Investigations of the Fishery Resources of Trinity River, California. Special Scientific Report – Fisher No. 12 from the U.S. Fish and Wildlife Service.
  3. Neil F. Thompson, Eric C. Anderson, Anthony J. Clemento, Matthew A. Campbell, Devon E. Pearse, James W. Hearsey, Andrew P. Kinziger, and John Carlos Garza. (2020). A complex phenotype in salmon controlled by a simple change in migratory timing. Science, 370 (6516)
  4. Buxton, T. H., Y. G. Lai, N. A. Som, E. Peterson, and B. Abban. 2022. The mechanics of diurnal thermal stratification in river pools: Implications for water management and species conservation. Hydrological Processes 36(11):e14749. DOI: 10.1002/hyp.14749.
  5. Carter, Katharine (2008). Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids – Implecations for California’s North Coast TMDLs.