Flow and water temperature simulation for habitat restoration in the Shasta River, California

Abstract

Low instream flows and high water temperatures are two factors limiting survival of native salmon in California's Shasta River. This study examines the potential to improve fish habitat conditions by better managing water quantity and quality using flow and water temperature simulation to evaluate potential restoration alternatives. This analysis provides a reasonable estimate of current and potential flows and temperatures for a representative dry year (2001) in the Shasta River, California. Results suggest restoring and protecting cool spring-fed sources provides the most benefit for native salmon species from a broad range of restoration alternatives. Implementing a combination of restoration alternatives further improves instream habitat. Results also indicate that substituting higher quality water can sometimes benefit native species without increasing environmental water allocations. This study shows the importance of focusing on the limitations of specific river systems, rather than systematically increasing instream flow as a one size fits all restoration approach.

Using Benthic Indicator Species and Community Gradients to Optimize Restoration in the Arid, Endorheic Walker River Watershed, Western USA

“…The effect of thermal loading, and maximum water temperature, in structuring aquatic communities is of particular importance for restoration optimization (Null et al ., ). The complicated relationship of maximum temperature with both season and elevation underscores the need for a working temperature model for the watershed to help predict the outcome of restoration actions with respect to temperature.…”

Seasonal macrophyte growth constrains extent, but improves quality, of cold‐water habitat in a spring‐fed river

“…Historically, surface runoff from direct precipitation and snowmelt in the Klamath Mountain's headwaters mixed with voluminous groundwater spring sources, creating a complex hydrologic regime characterized by stable baseflows augmented by seasonal runoff. However, due to upstream water storage and flow regulation (see Null, Deas, & Lund, for a description of surface water infrastructure in the Shasta River basin), streamflow in the Shasta River below Dwinnell Dam and Lake Shastina is derived predominantly from discrete springs discharging cool (11–13°C) and nutrient‐rich groundwater (Dahlgren et al, ; Lusardi et al, ; Nichols et al, ; NRC, ). The limited annual precipitation (24–46 cm year −1 ; NCRWQCB, ) in the Shasta River basin infiltrates Quaternary basalts and basaltic andesites of the High Cascades bounding the Shasta River to the north and east (Blodgett, Poeschel, & Thornton, ; Nathenson, Thompson, & White, ), ultimately discharging downslope at numerous springs along the eastern edge of the Shasta Valley.…”

Fish Habitat Optimization to Prioritize River Restoration Decisions

“…Input data for each reach includes initial flow and water temperature, boundary conditions at tributaries, diversions (including accretions/depletions) and atmospheric heating (Figure ). Input data are from a simulation model of the Shasta River (Null et al , ). Atmospheric heating is applied during summer, and the rate of heating varies with the extent of riparian shading (derived from atmospheric heating rates estimated from 2001 simulated conditions) (Null et al , ).…”

“…Input data are from a simulation model of the Shasta River (Null et al , ). Atmospheric heating is applied during summer, and the rate of heating varies with the extent of riparian shading (derived from atmospheric heating rates estimated from 2001 simulated conditions) (Null et al , ). Water and heat balances are simulated within the optimization model using a mass balance approach and do not explicitly incorporate thermal mass or travel time.…”

“…For the Shasta River, adding flow could be accomplished by reducing diversions, water marketing or instream flow releases from the Dwinnell Dam. Flow increases are bounded between zero and simulated weekly unimpaired flow (Null et al ., ). Flow is added at the existing water temperature of the reach, so there are no temperature benefits from increasing flow.…”