Effects Of Climate Change On Depression-Focused Groundwater Recharge In The Canadian Prairies

Small topographic depressions are ubiquitous in the glaciated terrain of the Northern Prairies characterized by a cold semiarid climate. Groundwater recharge in this region is focused in topographic depressions, which receive lateral inputs of snowmelt runoff in addition to vertical inputs of precipitation. The response of depression-focused recharge to climate change is largely unknown due to the difficulty of representing the complex interaction between depressions and surrounding uplands in hydrological models. This study evaluates climate change effects on recharge using a process-based hydrological model and the pseudo-global warming (PGW) approach representing a climate of 2092-2100, which has a higher mean annual temperature (+4.9 degrees C) and precipitation (+135 mm or +27%) compared with the present climate. The recharge model is conditioned using field data from an instrumented grassland site in the Canadian Prairies. Under the present climate, snowmelt runoff occurred in March-April over frozen soil, which accounted for the majority of water transfer from the upland to the depression. Under the PGW scenario, the amount of snowmelt runoff in March-April decreased due to lower snow accumulation and shorter periods of frozen soil. Instead, runoff occurred in midwinter and also in summer months due to increased intensity and duration of summer storms. Despite the increased precipitation, mean annual recharge rates decreased from 10.2 to 3.2 mm yr(-1), indicating the importance of considering the complex effects of warmer and wetter climate on hydrological processes in cold semiarid regions.