Shifting of Dominant Hydrological Processes in Headwater Catchments Under a Changing Climate

Abstract:

Headwater areas are critical in the hydrological mosaic of the global landscape. In mid-latitude regions, higher elevation headwater basins are usually snowmelt dominated. Due to diurnal fluctuations in temperature and thus incoming longwave radiation plus solar loading, snowmelt and evaporation can both start and end over the course of a 24-hour period. These processes yield an increase or decrease in the daily diurnal streamflow. We examined the diurnal fluctuations in streamflow from eight years of sub-daily resolution data at a number of small headwater basins located across the Southern Rocky Mountains of the Western United States. For each station-year, the shifting of the dominant hydrological process from snowmelt to evaporation was identified from the diurnal increase or decrease in streamflow. The magnitude and timing of this diurnal change was also estimated. The analysis included high and low snow years to determine the variation in process shifting, magnitude and timing of the diurnal change. Future climate scenarios were also considered to evaluate possible future changes.