California Department of Fish and Wildlife Steelhead Report Card Dashboard
The California Department of Fish and Wildlife (CDFW) tracks steelhead angler effort and success through a reporting program. This reporting program consists of a mandatory report card that all steelhead anglers need to have in their possession while fishing. Anglers record each day that they fish, where they fish, how many fish they catch, and whether those fish are from a hatchery (determined by the lack of an adipose fin, which is removed by hatchery staff before the fish is released), or were spawned in the wild (determined by the presence of an adipose fin).
Each year, anglers are required to send these report cards back to CDFW, either physically or by entering the information online.
After many years of collecting data, CDFW recently released a compilation of raw summary data for the period of 2012-2023 (linked here). The data set can be sorted by area (the Trinity River is one of 20 river systems or regions), season, or month, and shows the numbers of fishing trips, the number of hatchery steelhead caught, and the number of wild steelhead caught.
The Klamath River and tributaries (except the Trinity River) stands out as an exceptional fishery. The Trinity River is not too far behind it among the 20 steelhead fisheries in the state.
It’s important to understand that while the raw data is informative, it is only a starting point toward understanding the fisheries. For example, in many systems, including the Trinity, hatchery production has changed substantially over the time period that the dashboard shows. Some hatcheries have reduced steelhead production by as much as 40%, which has an obvious bearing on the average number of steelhead caught per trip. Conversely, this data set covers two of the most severe droughts that Northern California has ever experienced. Droughts can leave the smaller tributary streams, which are usually off-limits to fishing because steelhead prefer to spawn in smaller streams, too dry for fish to migrate into. So, they remain in the mainstem river where people can catch them more readily than in normal or wetter years when they would have migrated into their spawning streams earlier. Tribal harvest methods, too, have changed in this time period and are much more selective for hatchery steelhead (identified by their lack of an adipose fin) over wild steelhead.
Still, this dashboard can be very useful for planning where and when to go on a steelhead fishing trip. And steelhead anglers should be happy to see the data that they carefully record and report is going to good use!
You may notice a distinct absence of bugs flying above the river during these winter months. However, if you look closely you’ll find an active colony of tiny midges buzzing on the surface. These midges, despite their small size, are extremely important to the ecology of the Trinity River. Midges belong to the ‘true flies’ (order Diptera) and are related to other flies such as houseflies, craneflies, and mosquitoes.
Midges are often referred, especially by Trinity River Restoration Program scientists, as chironomids. This is because they belong to the family Chironomidae within the order Diptera. Chironomids are extremely diverse and are found worldwide in all types of different aquatic environments. Some are extremely tolerant of low oxygen and pollution; some even have a hemoglobin analog to survive in low oxygen environments. Others are extremely sensitive to poor water quality. Chironomids are often used to determine the health of streams because of the diversity of different water qualities they can tolerate.
Chironomids are especially important to the ecology of the Trinity River because they are a major food source for juvenile salmonids and other native species. Chironomids are known as a pioneer species which means they are the first to colonize new habitats. During the winter, when seasonal floods are wetting new landscapes, Chironomids take advantage. Their short life cycle (usually between 6 and 12 weeks) enables them to exploit habitat extremely quickly. This often results in a Chironomid ‘bloom’ (see picture). These seasonal ‘blooms’ often coincide with the emergence of salmonids from the gravel.
The chironomids small size and high abundance make it an easy first meal for tiny salmonid mouths. Chironomids along with Baetid mayflies profiled last month, are some of the most important food sources for juvenile salmonids during their outmigration to the ocean.
Figure Captions
A larval Chironomid [photo courtesy of Bugguide.net]
Newly inundated floodplain habitat with a Chironomid ‘bloom’. Each one of the tube-like structures are cases that Chironomids construct out of fine sediments. [Chris Laskodi, Yurok Tribe]
Chris Laskodi, M.S., Fish Ecologist – Yurok Tribal Fisheries Department
Chris serves as the fish biologist/ecologist for the TRRP in the program’s Science branch. Chris has worked on the Trinity River since 2015, previously serving as a fish biologist for the Yurok Tribe and a fisheries technician for the US Fish & Wildlife Service. Chris holds a B.S. in Wildlife, Fish and Conservation Biology from the University of California, Davis and a M.S. in Aquaculture/Fisheries from the University of Arkansas at Pine Bluff. In his free time, Chris enjoys taking friends and family fishing on one of the many watercraft available to him.
Rivers are dynamic ecosystems shaped by multiple interacting and overlapping physical and biological processes. A fundamental aspect of a river’s ecology is sediment, which is the foundational underpinnings of habitats, influence for water quality, and support for wildlife. In this article, we explore terminology and features of Trinity River sediments, the building blocks of our river system.
What is Sediment?
Although it might seem obvious, all sizes of rocks fit into the larger family of sediments. Sediments are inorganic particulates that can be transported by water, wind, or ice and deposited and perhaps stored for long periods of time in a particular location. In rivers, sediment is further classified according to its diameter and composition:
Clay (Particles smaller than 0.002 mm): Clay transports while suspended in the water column and when deposited can store nutrients aiding the growth of biology when organics chemically bind to individual clay particles.
Silt (Particles 0.002 mm to 0.063 mm): Silt also transports suspended in the water column and can affect light penetration and aquatic plant growth, just as clay particles do. Clays and silts that cloud the water also provide cover for fish, which use the cloudy water as protection from predators and tend to survive at higher rates when available intermittently.
Sand (Particles 0.063 mm to 2 mm): Sand provides a medium for plants to establish and grow. This sediment type provides rearing habitat for juvenile lamprey when located in deposits below large rocks or trees, and acts as a filter to benefit water quality when deposited between gravel particles.
Gravel (Particles 2 mm to 64 mm): Ranging from the size of a small blueberry to a large kiwi, gravel offers essential spawning grounds for fish and invertebrates.
Cobble (Particles 64 mm to 128 mm): About the size of an orange, cobbles are the framework for bar deposits in river systems. When settled they form a surface that is difficult to mobilize from and creates roughness that encourages small particles to deposit on top of them. While waters flow over through and under these habitat formations the sediments caught provide a diversity of flow in depth and velocity which species depend on in streams.
Boulders (Rocks larger than 128 mm): These create physical barriers in rivers that help form log jams, leading to diverse flow patterns and detailed habitats for a range of organisms.
Sources of Sediment in River Systems
Fine sediments entering the confluence of the North Fork and the East Fork North Fork after rain dropped on the the Monument Fire scar in July 2023.
Sediment can enter river systems through multiple processes, each contributing to the overall sediment dynamics and ecology of the river. Key sources of sediment include:
Erosion: As water flows over land soil and rock can move with it. Depending on the landscape and the soil content these sediments can be delivered to rivers, especially during heavy rainfall or rapid snowmelt.
Runoff: Rain and melting snow can wash fine sediments from forests, fields, urban areas, roads, and construction sites into nearby streams and rivers.
Bank Collapse: Riverbanks can be eroded by the current of flowing water, particularly in areas with high flow velocities, resulting in banks collapsing directly into the water.
Tributary Inputs: Creeks can contribute sediment as they flow into larger rivers, contributing sediments from their own drainage basins.
Human Activities: Construction, mining, and land clearing can disturb soil and rock, increasing sediment loads in nearby rivers. Deforestation can also enhance erosion rates when tree roots are damaged or destroyed, leading to hillslope failures into streams.
Natural Events: Floods, landslides, wildfires and volcanic eruptions can rapidly introduce large amounts of sediment into river systems, altering habitats and turbidity.
Aquatic Organisms: Organisms can influence sediment storage by building dams (beavers) or webs between gravels to capture food and fines (net-spinning caddisfly). Organisms can also mobilize sediment when building nests (salmon) or grazing for food, such as crayfish winnowing fine sediments from amongst gravels.
When the slope of a river is greater than 2 percent, water moves quickly over rocks and other obstacles creating rumbling mountain streams. Moving downstream as the valley walls open and slope decreases a pool and riffle river system will form. The creation of alternating river bends is based on physical obstacles along the river’s path and water velocity which will form deep (pools) and shallow (riffles). The dynamic plays a crucial role in the movement and storage of sediment as the river runs its course to the ocean. A few key terms:
Pools: Pools are deep areas of the river that form over time with flow velocity that scours (or digs) small unstable sediments from the area. Pools offer dynamic habitat during different times of the year that include a varied temperature column in the summer months when waters slow within the river. In winter, during high flows, pools are areas where faster water occurs. The increase in speed in pools relative to their companion riffles is what is responsible for pools scouring to depths found in summer.
Riffles: During lower flows that occur in late spring through fall, faster currents are found in riffles because the water surface is steeper on them. Riffles are nursery areas for macroinvertebrates and help oxygenate the water and benefit species that thrive in turbulent conditions. High flows in winter that scour pools deposit sediments from the scour on riffles downstream, and in this way a pool-riffle sequence of habitats is formed and maintained on alluvial rivers.
Salmon and Sediment Interaction
Salmon are a keystone species in freshwater ecosystems, and their interaction with sediment is crucial for their lifecycle. During spawning, female salmon seek out gravel beds on riffles and near the streams banks to lay their eggs. These gravel beds, composed of appropriately sized sediment, are essential because they provide the necessary water flow to provide oxygen to fertilized eggs, ensuring their development to the fry stage.
Additionally, the composition and stability of sediment in spawning areas can influence the quality of habitat available for juvenile salmon. Fine sediments, often stirred up during high flow events, can cover spawning habitats, suffocating eggs and reducing the overall success of salmon populations when fines are overly present.
However, Trinity River geomorphologists are learning that too few fines also pose survival risks to salmon. When spaces between gravels where eggs are spawned are left open, turbulence is created through flow within the salmon nest and can jiggle eggs causing abrasion to the egg membrane, leading to mortality. Too few fines can also cause surface flows in a river to be conveyed entirely through a bar, sieving off the juvenile salmon onto dry bar surfaces for predation by birds.
Join us Feb. 26 for Science on Tap featuring Dr. Todd Buxton for “Fine Sediment in the Trinity River: History, effects, and current Impacts”
Maintaining a balanced sediment regime within pool and riffle systems is essential not only for river ecology but also for the conservation of salmon, whose life cycles are intricately tied to the health of their sediment-rich habitats. As we learn more about these systems, it becomes increasingly important to recognize how sediment influences river health and ecology, guiding conservation efforts to ensure the survival of these vital ecosystems.
We invite you to join us Wednesday, Feb. 26 for Science on Tap! Dr. Todd Buxton will dive into Trinity River Fine Sediment, history, effects and current impacts. The event is held at the Trinity County Brewing Company and starts at 6pm.
Mayflies from the family Baetidae are this month’s ‘bug of the month’. Commonly known as blue winged olives by fly fishermen, Baetid mayflies are small (<10mm) and can be extremely prolific. In addition, they grow rapidly and can have multiple generations within a year (known as multivoltine). This means that you can see adult Baetid mayflies during most of the year although they are especially apparent during the winter in early spring when few other bugs are hatching.
Photo Credit: TroutNut.com
Baetid mayflies are exceptionally adept at colonizing new habitat. They are extremely good swimmers (for a bug) and are known for undertaking what is known as behavioral drift. Behavioral drift is a strategy where macroinvertebrates enter the flow of the river voluntarily to seek out new habitat. Short life cycles, excellent swimming ability, and the propensity to undertake behavioral drift allow them to settle new habitat like when high flows inundate floodplains.
They are often the first to colonize a new area due to their swimming skills and their preference for shallow, slow water. These newly formed areas grow algae very well which is the primary food source for Baetid mayflies. They can often exploit newly formed habitat within a few weeks and live their entire life cycle within 12 weeks before other bugs get a chance to settle in an area. Seasonal inundation of floodplains are extremely important to Baetid mayflies success. Juvenile salmon have evolved to depend on the seasonal inundation of floodplains because of the presence of Baetid mayflies, which they eat for food.
Chris Laskodi, M.S., Fish Ecologist – Yurok Tribal Fisheries Department
Chris serves as the fish biologist/ecologist for the Trinity River Restoration Program in the program’s Science branch. Chris has worked on the Trinity River since 2015, previously serving as a fish biologist for the Yurok Tribe and a fisheries technician for the US Fish & Wildlife Service. Chris holds a B.S. in Wildlife, Fish and Conservation Biology from the University of California, Davis and a M.S. in Aquaculture/Fisheries from the University of Arkansas at Pine Bluff. In his free time, Chris enjoys taking friends and family fishing on one of the many watercraft available to him.
Eric Peterson, Science Coordinator out monitoring algae on the Trinity River in 2024. [Jeanne McSloy, Trinity River Restoration Program]
The Program and partners have approved winter-time Environmental Flows for the next few water years. The intent of moving flows into the winter time is to provide flow conditions that Trinity River salmonids evolved to exploit. From a scientific point of view, that intent and the reasons behind it are organized into hypotheses that the Trinity River Restoration Program will be testing throughout implementation of the project.
For the year ahead with the implementation of a new flow management the Program will continue with both short and long-term monitoring projects. Long-term monitoring projects include, outmigrant monitoring (tracking the number and size of young fish heading out to sea), adult escapement monitoring (tracking the number and size of adult fish returning from the sea). Shorter duration studies to examine the flow changes include acoustic monitoring of rock movement, tracking the development of periphyton (algae) on newly inundated floodplains, and investigating the benthic macroinvertebrate (fish food) response to the flows.
Currently in the river, spring and fall run Chinook Salmon eggs are hatching and young fish are starting to emerge. Outmigrant monitoring will be ramping up to count these young fish on their migration. The Program is also preparing for some research on how low floodplains, like the Oregon Gulch inundation areas, develop vegetation and if it differs from our more traditional channel restoration sites.
Last but not least, the Limiting Factors Analysis, is on schedule with initial model development. The project intends to dissect the many limiting factors during the lifecycle of Trinity River Chinook so that the Program can better analyze it’s role and ways to continue restoration efforts more effectively. As the model is developed the task group will assemble the data to parameterize the model, an effort that will continue through 2025. Watch for results of those efforts to come out in summer of 2026!
Aerial Image of the Upper Conner Creek Restoration Site during phase 1 restoration in fall of 2024. [Elliot Sarnacki, Trinity River Restoration Program]
The Trinity River Restoration Program is working on two Trinity River channel rehabilitation projects in 2025; Phase II of the Upper Conner Creek Rehabilitation Project located in Junction City, CA and Phase I of the Sawmill Gravel Processing Site Rehabilitation Project located in Lewiston, CA.
Upper Conner Creek – Phase II
The second phase of the Upper Conner Creek Rehabilitation project includes similar physical habitat improvements constructed under Phase I such as floodplain connectivity, coarse sediment additions and large wood features. Recreational improvements include a new launch ramp and public restroom for the Bureau of Land Management – managed Junction City Campground River Access. Phase II of the Upper Conner Creek will begin in January 2025.
Sawmill Gravel Processing Site
The Sawmill Gravel Processing Site Rehabilitation Project Phase I is another implementation of the mechanical channel rehabilitation component of the Trinity River Restoration Program and is also intended to function in concert with the managed flow and sediment regimes to restore physical habitats that promote the spawning and rearing success of salmon in the Trinity River. As implied in the project name, the focus of the project is to rehabilitate an area that has thus far been used only as a source area and processing site for supplying coarse sediment used in gravel augmentation and channel reconstruction activities elsewhere on the river. Rather than leaving the area disturbed when processing activities conclude, the Trinity River Restoration Program recognized the opportunity to optimize the habitat and ecosystem benefits by developing a rehabilitation design centered on that area.
Environmental Assessments
Sediment was placed upriver of the Lewiston Bridge prior to high flow in 2023 to encourage habitat formation down river. [Todd Buxton, Trinity River Restoration Program]
The Trinity River Restoration Program’s Sediment and Wood Augmentation Environmental Assessment is complete. In addition to multiple existing sites and based on site-specific annual recommendations from the The Trinity River Restoration Program’s Physical Workgroup and Riparian and Aquatic Workgroup, the Environmental Assessment establishes new augmentation sites and allows for sediment and wood placement to address the a shortage of those key ingredients of riverine habitat upstream of Indian Creek.
The new augmentation sites are in the upper reaches of the Trinity River downstream of Lewiston Dam and include Dark Gulch, Trinity House Gulch, Steel Bridge, and Vitzthum Gulch. River corridors which periodically mobilize sediment and large wood perform diverse physical and ecological functions. Contributions to the disturbance regime disperse organisms and provide refugia during baseflow periods and during floodplain inundation events. The Sediment and Wood Augmentation Environmental Assessment is available by clicking below.
In partnership with the US Forest Service’s Shasta-Trinity National Forest and BLM’s Redding Field Office, TRRP is finalizing a Programmatic Environmental Assessment (PEA) to evaluate aquatic habitat restoration activities in the Trinity River watershed. The Watershed PEA analysis will focus on restoration activities that improve the quality and quantity of accessible cold-water aquatic habitat. As a programmatic analysis, watershed restoration projects would be implemented within the Trinity River watershed, in Trinity and Humboldt counties, with site specific surveys and compliance for individual projects tiered to the PEA.
Watershed Grantees
In 2025, the following watershed projects are slated to be implemented.
Salt Creek Floodplain Restoration – The Watershed Research and Training Center
This project aims to improve 2,000 feet of heavily degraded salmonid habitat along Salt Creek, a South Fork Trinity River tributary, by reconnecting the creek to its historic floodplain using engineered and process-based restoration techniques. The project will increase aquifer recharge and storage for slow release to temper a thermal barrier for salmonids, restore geomorphic functions that will improve salmonid spawning gravels, create pools for summer cool water refugia, increase habitat heterogeneity for winter flow high-velocity refugia, and improve native riparian flora, all of which will increase the resilience of aquatic species from the impacts of climate change. Implementation is scheduled for summer 2025 and summer 2026
Upper Hayfork Creek Assessment and Planning Study – The Watershed Research and Training Center
This project will assess over 17 stream miles and 700 floodplain acres within the upper Hayfork Creek watershed, a major tributary to the South Fork Trinity River, to identify restoration opportunities to improve salmonid habitat quality and quantity. The project will utilize GIS and LiDAR analyses, field measurements of salmonid presence and habitat characterization, and a comparison of ecological flow needs with water availability to produce one Restoration Assessment and Planning document with a priority list of restoration projects and one restoration design to advance toward implementation.
Water Resiliency in the Greater River Trinity Watershed for Aquatic Ecosystem and Human Domestic Needs – The Watershed Research and Training Center
The organization is tasked to plan and implement four storage tank arrays and establish long-term forbearance agreements to reduce annual water withdrawals from key tributaries to the Trinity River during the summer low-flow period. The project will increase the quality and quantity of natural habitats crucial to the survival of anadromous fishes and aquatic organisms in the Trinity River Watershed. Implementation is scheduled for spring 2025.
Weaver Creek Habitat Restoration Implementation – The Yurok Tribe Fisheries Department
The Yurok Tribe Fisheries Department will create instream habitat and develop new floodplain areas along the upper section of Weaver Creek, a tributary to the Trinity River. The project will control the spread of invasive plant species, establish habitat connectivity during summertime baseflow conditions, and support populations of threatened Coho Salmon. The Tribe will construct new habitat features including 4.96 acres of floodplain, 1.23 acres of overflow channels, 0.94 acres of constructed riffles, 0.37 acres of channel fill, and 0.36 acres of low flow channels. These enhancements will increase the structural complexity of the project reach and mitigate the impacts of low flows, which can lead to dry channel conditions on Weaver Creek. The project area is identified in the state and Federal recovery plans for Coho Salmon, which encourage floodplain reconnection and streambed restoration in Weaver Creek. The Yurok Tribe is collaborating with the Nor Rel Muk Wintu Nation, Federal land managers, the Weaverville Sanitary District, and adjacent landowners for this restoration project. Implementation is may be implemented as soon as summer 2025.
Rivers are vital parts of our ecosystems, and they behave differently depending on the climate they flow through. In a Mediterranean climate, which is characterized by hot, dry summers and variable, wet winters, river flow can be particularly interesting. Let’s explore some important terms and concepts related to river flow that is represented in our unique climate and system.
John Hubbel
What is River Flow?
At its most basic, river flow, or discharge, is the volume of water that moves through a river over a specific period of time. On the Trinity River, flow is typically measured in cubic feet per second (CFS). Currently flow rates are measured in a few locations above and below Trinity and Lewiston Dams. Discharge on the Trinity River at Lewiston has been measured daily since 1911, when Model T’s were just rolling off of the assembly line!
There are very few rivers in California that experience full natural flow. Most Northern California rivers are managed through dams that generate power, create water diversions, or hold back water for later use. Dams block upstream deposits of water, wood and sediment and when managed narrowly have caused significant harm to riverine ecology downstream.
Understanding river flow both pre-dam and post-dam helps river ecologists to compare current management with the pre-dam natural conditions that species and their ecology developed within. This strategy aims to deepen understanding of the natural environment to provide favorable conditions for plants, wildlife, and people that depend on the river.
Why is River Flow Important?
The Trinity River’s flow is crucial for many reasons:
Ecosystems: Flow influences the types of plants and animals that live in and around the river.
Water Supply: The Trinity River provides drinking water, supports economic development, supplies irrigation for agriculture and generates power for millions of Californians.
Recreation: The Trinity River supports activities like fishing, boating, hiking, gold panning, wildlife viewing and swimming.
Key Terms Related to River Flow: Managed vs Natural
Natural Seasonal Flow: Although highly variable from year to year, undammed rivers in a Mediterranean climate, tend to exhibit seasonal patterns. During the rainy winter months, flow rates typically increase due to precipitation, the size and magnitude of that increase depends on seasonal patterns and the frequency of storm events. In the spring, snow in the mountains melts adding flow to the Trinity River and its watershed. Conversely, in summer, flow rates tend to slowly decrease as the dry season progresses.
Natural Base Flow: This is the normal level of water flow in a river during dry periods. It usually comes from groundwater and keeps the river flowing even when there hasn’t been rain for a while. In a Mediterranean climate, base flow can be low during the summer months due less water in the system and high evaporation rates. Baseflows are important for cold-blooded aquatic species like foothill yellow legged frogs who utilize slow water for rearing and then populate riverside riparian areas as adults.
Hydrograph: A graph that illustrates how the flow of water in a river changes over time. It shows time on the horizontal axis and the flow rate, usually measured in cubic feet per second, on the vertical axis. As the line on the graph rises, it indicates an increase in river flow (like after rain), and when it falls, it represents a decrease (such as during dry periods). Hydrographs are important for managing water resources, studying weather patterns as well and ensuring that environmental flow needs are met in regulated river systems.
Natural Surface Runoff: After it rains, water flows over the land and enters rivers. This is known as surface runoff. Winter rains in the Trinity watershed typically lead the tributaries and the Trinity River (below Douglas City) to a spike in flow. However, the impact is highly dependent on the water year, ground saturation and snow accumulation. Surface runoff provides additional wood, leaf litter and sediment to rivers which are the building blocks for healthy habitat creation in the Trinity system.
Over-bank floods: When there is a lot of rain in a short period, rivers can overflow their banks, causing over-bank floods. On the Trinity River over-bank floods are more likely to occur during the wet season and provide important ecological functions, including to Trinity River fish. These flows improve soil quality, provide prime growing grounds for aquatic insects and other fish food and help to reset the form of the river’s main channel through scour.
Environmental Flow: Is a management term that identifies the quantity and timing of water needed to sustain the health of river ecosystems, particularly downstream from a dam. Managing environmental flow is important for maintaining habitat for Trinity River salmonids and other wildlife that depend on the river. Within the environmental flows framework there are many methods for implementation. Since 2004, the Trinity River Restoration Program’s method for environmental flows were based on functional implementation of three periods, a summer baseflow (450 CFS), a fall/winter baseflow (300 CFS), and a spring snowmelt mimic hydrograph. Since 2016 local scientists have advocated to adapt this method by adding variable flows to the wet-season months (December – April) for the benefit of growing healthier juvenile salmonids.
Recommended Periods within the Environmental Flow Timeline for Water Year 2025
1. December 15 – February 15 – Synchronized Storm Pulse
A dam release synchronized to a natural storm event. The release is triggered by a CNRFC forecast for the Trinity River above North Fork that rises to 4500 CFS or more. Once initiated, the release would be triggered even if the forecast is reduced. The primary purpose is to reduce redd smothering by preventing fine sediment accumulation from tributaries, to maximize the synchrony between tributaries and the mainstem of the river, as well as recondition the streambed and align the ecology for salmon food production.
2. February 16 – April 15 – Wet Season Flood
Depending on forecast water year type in the California Department of Water Resources February B120 forecast and whether a synchronized flow has occurred, the Program may schedule flows above baseflow in the Feb. 15 to Apr. 15 timeframe. Depending on the March B120 forecast, the schedule may be adjusted as of March 15. The primary purpose of this is to inundate floodplains for aquatic food production and habitat for juvenile salmonids at the right time of year – similar to natural wet season flooding.
3. April 16 – Variable – Snowmelt Peak and Recession
The spring snowmelt peak and recession are an important annual migratory cue for both adult and juvenile chinook. The Program has implemented a spring snow-melt mimic release annually since 2004. CDWR April B120 forecast determines total volume of restoration flow releases. Water that has not been released for Storm Pulse Flows or Wet Season Flooding is scheduled for release during the Snowmelt Peak and Recession period. This schedule encompasses many purposes for river ecology and the salmonid life cycle.
4.Managed Base Flow
Baseflows released from Lewiston Dam to the Trinity River are currently managed at 450 CFS through the summer, shifting to 300 CFS on Oct 15 through the subsequent spring. This management strategy is a relic from the 1999 Flow Study and was put in place with the mindset that increasing baseflow in the summertime could help with river temperature management for migrating adult spring chinook. Flows reduce in the fall because temperature objectives are no longer needed. In addition, water managers leaned on water savings during the fall through the wet season so that accumulation in the system could be understood prior to use for diversions or river ecology. Fish biologists hypothesize that if current summer and fall management were adapted to a more natural hydrograph it may serve Trinity River salmonids and other wildlife better.
Dicosmoecus (dee-co-smee-cus) caddisflies are better known by the common name ‘October caddisflies’. These caddisflies are notable for there extremely large size (1-2 inches), their concentrated emergence window (October), and their abundance especially in streams containing anadromous fish. These characteristics make it one of the most important hatches to not only fly-fishermen, but to wildlife such as birds as well.
Dicosmoecus like other caddisflies have three life stages: larvae, pupae, and adult. Larvae build cases out of small rocks which serves as protection and their housing. They drag these cases around while foraging for food, mostly algae and detritus. Dicosmoecus are especially notable by the large distances they can cover (up to 25 meters per day) to forage (Resh et al. 2011).
They continually grow and have to build new cases as the old ones become too small. After molting five times (called instars), they attach their cases to the underside of rocks and began to pupate. After about a month of pupating, they cut a hole in their case and swim to the surface before shedding their exoskeleton one more time and becoming adults.
Caddisflies, unlike mayflies, will live for several weeks while they seek out a mate. You will often see them active at dusk and just after sunset. Keep a look out for the large moth-like bugs during sunset for the next few weeks.
References
Resh, V.H., M. Hannaford, J. Jackson, G.A. Lamberti, and P.K. Mendez. 2011. The biology of the limnephilid caddisfly Dicosmoecus gilvipes (Hagen) in Northern California and Oregon (USA) streams. Zoosymposia 5:413-419.
Images courtesy of Red’s Fly Shop and Troutnut.com
Chris Laskodi, M.S., Fish Ecologist – Yurok Tribal Fisheries Department
Chris serves as the fish biologist/ecologist for the TRRP in the program’s Science branch. Chris has worked on the Trinity River since 2015, previously serving as a fish biologist for the Yurok Tribe and a fisheries technician for the US Fish & Wildlife Service. Chris holds a B.S. in Wildlife, Fish and Conservation Biology from the University of California, Davis and a M.S. in Aquaculture/Fisheries from the University of Arkansas at Pine Bluff. In his free time, Chris enjoys taking friends and family fishing on one of the many watercraft available to him.
Prior to construction of dams on the Trinity River, flow and river temperatures were synchronized throughout the watershed with seasonal ecology. Storms and snow melt floods regularly altered the stream channel, transporting sediments, wood and rocks. Seasonally predictable disturbance helped maintain a healthy streambed and riparian forest. Disturbance was followed by growth, with wetted areas providing consistent habitat for insects, fish and frogs alike. Even though each year provided different conditions, there was predictability with which aquatic and riverine species, like salmon, evolved to exploit.
Since the foundational 1999 Trinity River Flow Evaluation Report, more than 20 years of scientific research within the Trinity River Basin and from rivers across the world have improved outcomes for Trinity River salmonids. This wealth of new and improved knowledge has made scientists within the Program increasingly aware that changes to flow management have the potential to increase the strength and resiliency of juvenile salmonids produced in the Trinity River.
One important revelation is that elevated releases that continue through late spring and into the summer have kept water too cold for optimal juvenile salmon growth. Larger fish have a better chance of survival in the ocean, so improved flow management that can provide better temperatures for growth is likely to improve survival and subsequent adult returns. Further, Program scientists have found that the majority of young Chinook Salmon have already left the restoration reach by the time elevated spring releases provide access to restored habitats created by the Program over the last 18 years, including floodplains and side channels.
Many studies have shown that when floodplains and side channels get wet at the right time of year when juvenile salmon can use them, then they can take advantage of all the extra food that those habitats create. When fish can access important habitat, increase their food consumption, and have the right temperatures for growth, they can grow faster, get bigger, and survive better.
Recommendations for Change
Changes to Trinity River flow management to partially mimic the seasonality of natural flow were approved by the Trinity Management Council this past September. Program partners in our Flow Workgroup technical advisory committee developed a collaborative proposal that met ecological objectives and accommodated recreational considerations requested by Trinity County. The proposal also needed to adhere to existing environmental regulations. Following the affirmative Trinity Management Council vote in September, the recommendation is now awaiting approval by the U.S. Department of the Interior.
Water Year 2025 environmental flow management is designed to partially mimic natural seasonality so that river ecology can build around flow as it did prior to dams. These managed flows do not strictly follow the natural ecology of the watershed, but rather they represent management that strikes a balance between ecological needs, water availability, and other management and infrastructure constraints. Scientists hypothesize that adding pulse flows, increasing flow in winter, and decreasing flow in the spring and summer could be beneficial to Trinity River salmonids. However, there is no recommendation for this water year to reduce minimum baseflows in summer or fall.
First Recommended Change: Synchronized Storm Pulse
The first recommended sequential change is the two-month Synchronized Storm Pulse period (December 15-February 15) where there may be one peak flow of 6,500 cubic feet per second released from Lewiston Dam timed to match a natural storm event. This synchronized flow would consist of a rapid flow increase release held for a short period then reduced to 750 cubic feet per second. A synchronized storm pulse would only be triggered if the river is predicted to be at least 4,500 cubic feet per second near the North Fork Trinity River. No synchronized release would occur if the river is not predicted to reach that level between December 15 and February 15.
Winter storm pulses provide many ecological benefits, primarily by causing streambed disturbance. Sediments ranging in size from sand to large gravel are displaced and moved downstream, and wood in the channel can be moved or cause erosion in the channel that increases habitat diversity. Fine sediments rich in nutrients are also washed onto upland riparian areas that are typically dry. As waters recede, nutrients remain to help develop a healthy riparian community of plants and animals. For salmon, the disturbance from big powerful storms provides opportunity for small, soft-bodied bugs to proliferate, which are an excellent food source for small juvenile salmonids as they emerge from the gravel.
Pre-dam Trinity River flows at Lewiston (colored lines), and a typical normal water year flow release after 2000 (black line).
Since 1960’s, with very few exceptions, typical winter flow releases from Lewiston Dam have remained under 300 cubic feet per second. When big storms pass through, tributaries deliver trees, nutrients, and all sizes of sediment, which enter the Trinity River where flows are artificially low due to limited dam releases. Often there is not enough flow in the Trinity River to move these deliveries from tributaries, so they settle out quickly. Where Deadwood Creek enters the Trinity River, large fine sediment deposits from the 2018 Carr fire have immediately settled into slow waters in recent years resulting in two negative effects. First, the tributary delta has formed unnaturally, and second fine sediments have smothered and suffocated salmon and steelhead eggs in the gravel.
Second Recommended Change: Wet-Season Flood
The second recommended change is the two-month (February 16 – April 15) Wet-Season Flood period, during which dam releases would be elevated above the typical 300 cfs baseflow with some variability. The amount of water released during this period depends on seasonal snow and rain accumulation and a conservative forecast of inflow to Trinity Reservoir from the California Department of Water Resources (90% B120).
These beneficial floods push water onto floodplains and keeps them wet for months, which essentially converts terrestrial habitat into aquatic habitat just as salmon and steelhead begin to emerge from the gravel and populations increase. This seasonal aquatic habitat grows food for fish and provides slow water habitat for small fish to rest, grow, and escape many aquatic predators.
Oregon Gulch floodplain inundation in March 2024 provided habitat for millions of juvenile salmonids and other aquatic species. Aaron Martin, Yurok Tribal Fisheries Department.
Snow Melt Peak and Recession
The Snowmelt Peak and Recession period has been implemented on the Trinity River for the past 20 years. The action provides important migration cues for adult and juvenile salmonids. Peak flows can provide many of the benefits that winter storm pulse flows provide earlier in the year, resetting the base of the food web and delivering nutrients to riparian areas. Receding flows trigger spring Chinook Salmon returning from the ocean to migrate toward over-summer habitat. Additionally, juvenile salmon and steelhead migrate out of rivers, to the ocean, as habitat availability decreases with dropping flows.
Proposed changes to flow management in 2025 would use the same volume of water that has been available since 2000, so any water released for a synchronized storm pulse or wet season flood would be borrowed from the spring snow melt release. As a result, releases would slow earlier, reducing cold-water impacts to fish growth while providing ecological benefits earlier in the year. Adjustments to flow management that more closely align dam releases with natural ecological processes are intended to also benefit other aquatic and semi-aquatic species, such as Foothill Yellow Legged frogs and Northwestern Pond turtles.
As mentioned, the recommendations presented for water year 2025 are designed to partially mimic natural seasonal processes so that ecological function can develop on the seasonal timeline, as it did for millennia prior to dam construction. Program scientists have long known that these recommended changes are necessary for making progress toward producing stronger healthier Trinity River fish populations.
If changes are approved by the Department of the Interior, the Trinity River Restoration Program will announce details regarding; flow action changes, ways to stay informed and notification timelines as they develop.
Recommended 2025 Water Year Environmental Flow Management Timeline
You may have noticed a rather large insect fluttering down the river during the months of September and October. These insects are mayflies from the family Isonychiidae (eye-son-nic-ee-uh-day) (known in the fly-fishing community as Mahogany Duns or Slate Drakes). Mayflies are unique in that they have two adult stages in their lifecycle while all other insects have one.
Isonychiidaemayflies usually live an entire year in the river as nymphs before swimming to the edges of the river, crawling out of the river on a rock, and emerging into their sub-adult stage. As adults, they typically only live for a day or two as their only job is to mate, lay eggs, and then die. Isonychiidae mayflies are noted for their large size compared to other mayflies and for their unique swimming ability. They are very adept swimmers and use their swimming prowess to capture their prey. They also have fine hairs on their forelegs which trap algae and other detritus which they then consume. The nymphs are a very strange looking (compared to other mayflies) and are readily identifiable by their elongated shape and ‘racing-stripe’ down their backs. Looking closely, the hairs on their forelegs become readily apparent and they are very easy to identify for any aquatic entomologist.
Isonychiidae mayflies are unique to the Trinity River with other populations scattered across northern California. The nearest population is found in the Pit River, but are rare there. The population in the Trinity River seems to be thriving and right now is the best time to see both the nymphs and adults. Look for the nymphs along the streambanks where they will look like small fish darting between the rocks. You will notice their shed exuviae (exoskeletons) attached to rocks. Adults can be found in the early afternoon fluttering in the air above the river. They seem to be more common in the area between Junction City and Cedar Flat.
Chris Laskodi, M.S., Fish Ecologist – Yurok Tribal Fisheries Department
Chris serves as the fish biologist/ecologist for the TRRP in the program’s Science branch. Chris has worked on the Trinity River since 2015, previously serving as a fish biologist for the Yurok Tribe and a fisheries technician for the US Fish & Wildlife Service. Chris holds a B.S. in Wildlife, Fish and Conservation Biology from the University of California, Davis and a M.S. in Aquaculture/Fisheries from the University of Arkansas at Pine Bluff. In his free time, Chris enjoys taking friends and family fishing on one of the many watercraft available to him.
![image of some of the restoration area before construction at Upper Conner Creek phase II in July 2024. [Kiana Abel, Trinity River Restoration Program]](https://www.trrp.net/wordterrain/wp-content/uploads/2025/01/IMG_0512.jpg)
