Annual and Seasonal Variations of Hydrological Processes Under Climate Change Scenarios in Two Sub-Catchments of a Complex Watershed

Abstract

The Elbow River watershed, located in the rain shadow of the Rocky Mountains in western Canada, is characterized by a complex hydrological regime due to significant differences in climate and geomorphological settings between the west and east sub-catchments. This watershed has experienced several extreme droughts and floods in the recent decades, which might be accentuated with climate change. This study was undertaken to investigate the average annual and seasonal variations of surface and sub-surface hydrological processes in the west and east sub-catchments along with and the entire watershed under five plausible GCM-scenarios up to 2070 using the physically-based, distributed MIKE SHE/MIKE 11 model. Most of the scenarios indicate a reduction in the average annual overland flow, groundwater recharge and baseflow in the east sub-catchment. The pattern of seasonal change generally exhibits a rise in overland flow, baseflow, evapotranspiration, groundwater recharge, and streamflow in winter-spring and a decline in summer-fall. The induced changes in hydrological processes are proportionally more perceptible in the east sub-catchment compared to the west sub-catchment. However, the west sub-catchment governs the watershed behaviour and determines the future changes, over-riding the stronger climate change signal in the east. This investigation indicates that a greater understanding of climate change impacts on the water balance of a watershed with significant differences in sub-regional settings is achieved when capturing the surface and subsurface hydrological process responses of each sub-catchment individually along with the entire watershed. Such information can guide water resources management by providing a more rigorous assessment of the processes involved in the watershed.