As a result, upwelling hyporheic waters create cool thermal refugia during warm months. Where hyporheic exchange is extensive, this seasonal redistribution of heat load can significantly attenuate the summer maximum temperatures of surface waters. Floodplain forests are critical to maintain the channel processes and floodplain structure that encourage hyporheic flow exchange. Forests also mediate local microclimate, conserving the relatively cool thermal signature of hyporheic-origin water after it upwells at the surface in summer. The potential importance of these mechanisms suggests that protection or restoration of natural forests and dynamic, anabranched or anastomosed channel structure can substantially improve the capacity of floodplain rivers to resist adverse effects of climate warming.
Salmonids are especially sensitive to stream temperatures in summer months.
With increases in concentrations of greenhouse gases, climate models suggest warmer temperatures and reduced summer stream flows for the Rocky Mountain West. To analyze the impact of potential climate change, a case study of the Madison River in Montana has been chosen. This river has been identified by Trout Unlimited as an important sport fishery. The model will be run for representative 7-day periods in the spawning period and low flow summer period for current climate. Additionally, results from the GISS and GFDL double CO2 GCM runs for mean monthly temperature will be imposed on current climate.