An assessment of the current and future thermal regimes of three streams located in the Wenatchee River basin, Washington State: some implications for regional river basin systems

Abstract

We examine summer temperature patterns in the Wenatchee River and two of its major tributaries Icicle and Nason Creeks, located in the Pacific Northwest region of the United States. Through model simulations we evaluate the cooling effects of mature riparian vegetation corridors along the streams and potential increases due to global warming for the 2020s-2080s time horizons. Site potential shade influences are smaller in the mainstream due to its relatively large size and reduced canopy density in the lower reaches, proving a modest reduction of about 0.3 • C of the stream length average daily maximum temperature, compared with 1.5 • C and 2.8 • C in Icicle and Nason Creeks. Assuming no changes in riparian vegetation shade, stream length-average daily maximum temperature could increase in the Wenatchee River from 1-1.2 • C by the 2020s to 2 • C in the 2040s and 2.5-3.6 • C in the 2080s, reaching 27-30 • C in the warmest reaches. The cooling effects from the site potential riparian vegetation are likely to be offset by the climate change effects in the Wenatchee River by the 2020s. Buffers of mature riparian vegetation along the banks of the tributaries could prevent additional water temperature increases associated with climate change. By the end of the century, assuming site potential shade, the tributaries could have a thermal condition similar to today's condition which has less shade. In the absence of riparian vegetation restoration, at typical summer low flows, stream length average daily mean temperatures could reach about 16.4-17 • C by the 2040s with stream length average daily maxima around 494 Climatic Change (2010) 102:493-520 19.5-20.6 • C, values that can impair or eliminate salmonid rearing and spawning. Modeled increases in stream temperature due to global warming are determined primarily by the projected reductions in summer streamflows, and to a lesser extent by the increases in air temperature. The findings emphasize the importance of riparian vegetation restoration along the smaller tributaries, to prevent future temperature increases and preserve aquatic habitat.

Potential future climate effects on mountain hydrology, stream temperature, and native salmonid life history

“…This finding is similar to previous a study that demonstrated T s response to climate change was more related Q reductions than to increased T a (Cristea and Burges 2010). We also demonstrate that T s and subsequent salmonid incubation responses to future climate scenarios are likely to vary with interannual hydroclimatological conditions, with 2010 having a greater magnitude of Q and T s response in all scenarios.…”

“…Expected changes include earlier spring snowmelt (Mote et al 2005;Stewart 2009;MacDonald et al 2011), reductions in late season streamflow (St. Jacques et al 2010), increased drought (Pederson et al 2010;Sauchyn and Bonsal 2013), and subsequent increased human demand on water resources (Schindler and Donahue, 2006). Stream thermal regimes are likely to respond to changes in hydroclimatic regimes (Cristea and Burges 2010), as the capacity for streams to store heat is inversely proportional to volume (Poole and Berman 2001;Webb et al 2003). Degradation of thermal habitat as a result of anthropogenic and natural disturbance, coupled with competition from introduced species, will likely further reduce habitat availability for native salmonids in the Rocky Mountains (Meyer et al 1999;Isaak et al 2012a;Isaak et al 2012b;Jones et al 2013).…”

Coupled daily streamflow and water temperature modelling in large river basins

“…Brown, 1969;Sridhar et al, 2004;Cristea and Burges, 2010), were disregarded. Although this contributes to uncertainties in river discharge and water temperature simulations, impacts of processes like groundwater advection, energy exchange between river bed and water interface, dispersion of heat and local conditions (topography and vegetation) in main rivers are relatively small at this large scale (Liu et al, 2005;Caissie, 2006).…”

Climate change effects on stream and river temperatures across the northwest U.S. from 1980–2009 and implications for salmonid fishes

“…On large rivers where cold-water storage is available behind reservoirs, water releases could be timed to decrease temperatures during critical biological periods as has been the case on the Clearwater River for migrating salmon in northern Idaho the last two decades. On smaller streams, maintaining or restoring instream flows and improving riparian communities to increase stream shading could offset significant amounts of future warming where degradation is severe (Meier et al 2003;Moore et al 2005;Cristea and Burges 2009). Removal of barriers to fish movement could decrease fragmentation and provide populations the flexibility to shift their distributions and track thermal habitat as needed (Fausch et al 2006;Daufresne and Boet 2007;Isaak et al 2010a).…”