Climate change and stream temperature projections in the Columbia River basin: habitat implications of spatial variation in hydrologic drivers

Abstract

Abstract. Water temperature is a primary physical factor regulating the persistence and distribution of aquatic taxa. Considering projected increases in air temperature and changes in precipitation in the coming century, accurate assessment of suitable thermal habitats in freshwater systems is critical for predicting aquatic species' responses to changes in climate and for guiding adaptation strategies. We use a hydrologic model coupled with a stream temperature model and downscaled general circulation model outputs to explore the spatially and temporally varying changes in stream temperature for the late 21st century at the subbasin and ecological province scale for the Columbia River basin (CRB). On average, stream temperatures are projected to increase 3.5 °C for the spring, 5.2 °C for the summer, 2.7 °C for the fall, and 1.6 °C for the winter. While results indicate changes in stream temperature are correlated with changes in air temperature, our results also capture the important, and often ignored, influence of hydrological processes on changes in stream temperature. Decreases in future snowcover will result in increased thermal sensitivity within regions that were previously buffered by the cooling effect of flow originating as snowmelt. Other hydrological components, such as precipitation, surface runoff, lateral soil water flow, and groundwater inflow, are negatively correlated to increases in stream temperature depending on the ecological province and season. At the ecological province scale, the largest increase in annual stream temperature was within the Mountain Snake ecological province, which is characterized by migratory coldwater fish species. Stream temperature changes varied seasonally with the largest projected stream temperature increases occurring during the spring and summer for all ecological provinces. Our results indicate that stream temperatures are driven by local processes and ultimately require a physically explicit modeling approach to accurately characterize the habitat regulating the distribution and diversity of aquatic taxa.

StreamFlow 1.0: an extension to the spatially distributed snow model Alpine3D for hydrological modelling and deterministic stream temperature prediction

“…Ferrari et al, 2007;Ficklin et al, 2012). The increase in mean annual precipitation predicted by some studies will only slightly mitigate this temperature rise through an increase of the mean annual discharge -and hence the heat capacity -of the streams (Ficklin et al, 2012(Ficklin et al, , 2014. The reduction of the spring freshet will diminish the buffering effect of snowmelt on stream temperature, hereby leading to larger stream temperature increases in spring (Ficklin et al, 2014).…”

“…Mohseni et al, 1998;Caissie, 2006), the increase in air temperature is expected to be associated with globally higher stream temperatures over the year (e.g. Ferrari et al, 2007;Ficklin et al, 2012). The increase in mean annual precipitation predicted by some studies will only slightly mitigate this temperature rise through an increase of the mean annual discharge -and hence the heat capacity -of the streams (Ficklin et al, 2012(Ficklin et al, , 2014.…”

“…Apart from its relevance for downstream areas, mountain hydrology also strongly impacts hydropower production (e.g. Finger et al, 2012;Majone et al, 2016), determines the habitat suitability of numerous aquatic organisms (e.g. Short and Ward, 1980;Hari et al, 2006;Wilhelm et al, 2015;Padilla et al, 2015) and even plays a noticeable role in the global emission of carbon dioxide into the atmosphere (Butman and Raymond, 2011;Raymond et al, 2013).…”

“…Some studies predict an increase in winter precipitation, which could at least partially compensate for the decreased fraction of solid precipitation and sustain the spring freshet close to its actual level Beniston, 2012;Finger et al, 2012;Fatichi et al, 2015). Autumn and winter stream discharge is expected to increase in magnitude and variability as a result of the higher fraction of precipitation falling as rain, which might result in greater flood risks in winter (Barnett et al, 2005;Bavay et al, 2009;Finger et al, 2012;Beniston, 2012). Summer discharge will likely be much reduced and the drought risks therefore more pronounced, at least in the watersheds with little or no glacier cover Stewart et al, 2015).…”

“…Morrison et al, 2002;Null et al, 2013;Ficklin et al, 2014;Stewart et al, 2015). Due to the strong correlation between stream and air temperatures (e.g.…”