Graduation Date

Spring 2024

Document Type



Master of Science degree with a major in Natural Resources: option Environmental Science and Management

Committee Chair Name

Alison O'Dowd

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Darren Ward

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Nicholas Som

Third Committee Member Affiliation

HSU Faculty or Staff


Trinity River, Northern California, Benthic invertebrates, Scour, Floodplain inundation, Flow management, Juvenile salmonid food availability

Subject Categories

Environmental Science and Management


Regulated flow releases on the Trinity River in northern California have shifted the timing of high flows from winter to late spring and reduced their magnitude. The timing and extent of scour from high flow events and the timing and duration of marginal (bankside) habitat inundation has shifted as a result. Literature is sparse regarding the effects of these hydrologic alterations on Trinity River benthic macroinvertebrate (BMI) communities, an important food resource for juvenile salmonids. In the 2023 water year, a wet winter coupled with additional flow releases from Lewiston Dam provided the opportunity to analyze the impact of scour and marginal inundation on BMI biomass and density. Sampling was conducted at four study sites on the Trinity River from October 2022 to June 2023. Invertebrate biomass and density declined sharply following a January 2023 scouring event. The post-scour community biomass contained higher percentages of juvenile salmonid food taxa, and food biomass reached or exceeded pre-scour levels at 47 days post-scour. Invertebrates colonized newly inundated marginal habitats within two weeks, with the most abundant taxa being Chironomidae (a key food taxon for juvenile salmonids). However, clear patterns were absent when examining the relationship between increasing marginal inundation duration and juvenile salmonid food taxa biomass. A scour event concurrent with marginal inundation complicated the ability to see if marginal inundation duration was related to changes in invertebrate biomass. These results suggest that dam-derived scouring flows released earlier in the water year would allow benthic macroinvertebrate communities to reset and recover prior to juvenile salmonid rearing. Furthermore, the presence of juvenile salmonid food resources in newly inundated habitats gives credence to flow regimes that include elevated baseflows during late winter and early spring, thereby creating more optimal habitat conditions for juvenile salmonids.

Citation Style



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