Interactive Effects of Water Diversion and Climate Change for Juvenile Chinook Salmon in the Lemhi River Basin (U.S.A.)

Abstract

The combined effects of water diversion and climate change are a major conservation challenge for freshwater ecosystems. In the Lemhi Basin, Idaho (U.S.A.), water diversion causes changes in streamflow, and climate change will further affect streamflow and temperature. Shifts in streamflow and temperature regimes can affect juvenile salmon growth, movement, and survival. We examined the potential effects of water diversion and climate change on juvenile Chinook salmon (Oncorhynchus tshawytscha), a species listed as threatened under the U.S. Endangered Species Act (ESA). To examine the effects for juvenile survival, we created a model relating 19 years of juvenile survival data to streamflow and temperature and found spring streamflow and summer temperature were good predictors of juvenile survival. We used these models to project juvenile survival for 15 diversion and climate-change scenarios. Projected survival was 42-58% lower when streamflows were diverted than when streamflows were undiverted. For diverted streamflows, 2040 climate-change scenarios (ECHO-G and CGCM3.1 T47) resulted in an additional 11-39% decrease in survival. We also created models relating habitat carrying capacity to streamflow and made projections for diversion and climate-change scenarios. Habitat carrying capacity estimated for diverted streamflows was 17-58% lower than for undiverted streamflows. Climate-change scenarios resulted in additional decreases in carrying capacity for the dry (ECHO-G) climate model. Our results indicate climate change will likely pose an additional stressor that should be considered when evaluating the effects of anthropogenic actions on salmon population status. Thus, this type of analysis will be especially important for evaluating effects of specific actions on a particular species. Efectos Interactivos de la Desviación del Agua y el Cambio Climático en Individuos Juveniles de Salmón Chinook en la Cuenca del Río Lemhi (E.U.A.).

Incorporating Climate Science in Applications of the U.S. Endangered Species Act for Aquatic Species

“…Listing decisions ideally require a large‐scale, full‐range model because the likely future of the entire species is being assessed. Evaluations for Section 7 or similar consultations may require a much more local or mechanistically detailed model in addition to a species‐wide model (e.g., Walters et al ).…”

Interactive influences of climate change and agriculture on aquatic habitat in a Pacific Northwestern watershed

“…However, global drivers, such as climate change, may pose even more substantial threats to aquatic habitats (Rieman and Isaak ) and may interact with local‐scale stressors in ways that compound their effects (e.g., Walters et al. ). Climate change is expected to have profound impacts on various factors, including water temperatures and the hydrologic cycle, that influence the ability of aquatic systems to provide services (Frederick and Gleick , Poff et al.…”

“…, Walters et al. , Lawrence et al. ), our knowledge of how climate change will interact with future changes of other stressors is limited.…”

Choosing and Using Climate‐Change Scenarios for Ecological‐Impact Assessments and Conservation Decisions

“…Ecological sensitivity to climate can be characterized via empirical analysis of biological response to climatic drivers (e.g., Battin et al ; Boughton & Pike [this issue]; Walters et al [this issue]), especially at transition zones, where climate can limit performance (Baker et al ; Hazen et al ), and biological thresholds, where changes in local climate conditions cause nonlinear responses (e.g., stream‐temperature threshold for salmon mortality [McCullough ]). Such analyses are sensitive to choice of biological response variable and require accounting for nonclimatic drivers of change, spatial heterogeneity, and temporal autocorrelation (Brown et al ; Hare et al ).…”

“…These observations, the locked‐in emissions from the existing energy system, and the lack of substantial international commitment to reducing emissions, make achieving low‐end scenarios (e.g., B1) increasingly unlikely (MIT ). Walters et al (this issue) deem the higher of the available emissions scenarios more plausible (A1B vs. B1), whereas Brainard et al () use a range of emissions scenarios in part because they did not make assumptions about future technology or policy developments. Step 3c.…”