Modeling effects of climate change on Yakima River salmonid habitats

Abstract

We evaluated the potential effects of two climate change scenarios on salmonid habitats in the Yakima River by linking the outputs from a watershed model, a river operations model, a two-dimensional (2D) hydrodynamic model, and a geographic information system (GIS). The watershed model produced a discharge time series (hydrograph) in two study reaches under three climate scenarios: a baseline , a 1-°C increase in mean air temperature (plus one scenario), and a 2-°C increase (plus two scenario). A river operations model modified the discharge time series with Yakima River operational rules, a 2D model provided spatially explicit depth and velocity grids for two floodplain reaches, while an expert panel provided habitat criteria for four life stages of coho and fall Chinook salmon. We generated discharge-habitat functions for each salmonid life stage (e.g., spawning, rearing) in main stem and side channels, and habitat time series for baseline, plus one (P1) and plus two (P2) scenarios. The spatial and temporal patterns in salmonid habitats differed by reach, life stage, and climate scenario. Seventy-five percent of the 28 dischargehabitat responses exhibited a decrease in habitat quantity, with the P2 scenario producing the largest changes, followed by P1. Fry and spring/summer rearing habitats were the most sensitive to warming and flow modification for both species. Side channels generally produced more habitat than main stem and were more responsive to flow changes, demonstrating the importance of lateral connectivity in the floodplain. A discharge-habitat sensitivity analysis revealed that proactive management of regulated surface waters (i.e., increasing or decreasing flows) might lessen the impacts of climate change on salmonid habitats.

Effects of Extreme Hydrologic Regimes on Juvenile Chinook Salmon Prey Resources and Diet Composition in a Large River Floodplain

“…The importance of off‐channel habitats has been demonstrated in several systems (Limm and Marchetti ; Hattin et al. ; Goertler et al. ), and the Yolo Bypass provides two valuable forms of off‐channel habitat: floodplain in wet years and tidal slough in drier years.…”

Changes in Streambed Composition in Salmonid Spawning Habitat of the Elwha River during Dam Removal

“…First, many of these floodplain channels have completely filled in and contain very little flow during the winter and no flow during the summer. Floodplain channels provide important spawning (i.e., Morley et al, 2005;Hatten et al, 2014) and rearing habitats (i.e., Bustard and Narver, 1975;Murphy et al, 1989;Sommer et al, 2001) for some salmonid species. The reduced or eliminated seasonal flow resulting from sediment deposition significantly reduces or eliminates this habitat.…”

Assessing climate-change risks to cultural and natural resources in the Yakima River Basin, Washington, USA

“…Some simulations, however, indicate that salmonids could benefit from warmer water temperatures and increased flows, depending on stream reach, season, and elevation. For example, Hardiman and Mesa (2013) found warmer water increased juvenile steelhead growth in springtime, while Hatten et al (2013) projected that coho salmon spawning and over-wintering habitats increased in late fall and winter under climate change as simulated stream flows increased. However, our simulations did produce more negative than positive outcomes for salmonid habitat, leading us to conclude that there will likely be a decrease in salmonid habitat in portions of the YRB (i.e., mid to lower elevations).…”

“…The potential effects of two climate change scenarios on the habitats of four life stages of coho salmon and three life stages of fall Chinook salmon in the Gap and Wapato reaches were evaluated in final article, Hatten et al (2013). The habitat analysis focused on suitable hydraulic features (e.g., depth and velocity at a given discharge) and not water temperature since two-dimensional simulations of water temperature were not available.…”

“…Hardiman and Mesa (2013) then looks at the effects of increased stream temperatures on juvenile steelhead growth in two tributary and one mainstem reach under baseline and future climate scenarios with a bioenergetics model. Finally, Hatten et al (2013) examines how changes in stream flow will affect coho and fall Chinook salmon in two Yakima River mainstem reaches under baseline and future climate scenarios with a rule-based fish habitat model. Each article has been published as a standalone product since each tackled a unique climate change challenge, from decision-support tools to detailed habitat simulations under baseline and future conditions.…”