Controls on connectivity and streamflow generation in a Canadian Prairie landscape

Abstract

Linkages between the controls on depressional storage and catchment streamflow response were examined in a wetland dominated basin in the Canadian Prairie Pothole region through a combination of field monitoring and modelling. Snowmelt, surface storage, water table elevation, atmospheric fluxes, and streamflow were monitored during spring snowmelt and summer in a 1 km2 sub-catchment containing a semi-permanent pond complex connected via an intermittent stream. Snow accumulation in the basin in spring of the 2013 study year was the largest in the 24-year record. Rainfall totals in 2013 were close to the long term average, though June was an anomalously wet month. The water budget of the pond complex indicates that there was a significant subsurface contribution to surface storage, in contrast to previous studies in this region. Following snowmelt, subsurface connectivity occurred between uplands and the stream network due to activation of the effective transmission zone in areas where the water table was located near the ground surface, allowing significant lateral movement of water into the stream network. Modelling results suggest there was significant infiltration into upland soils during the study period and that upland ponds are an important consideration for accurately simulating catchment discharge. The flux of groundwater to the wetland complex during periods of subsurface connectivity was also important for maintaining and re-establishing surface connectivity and streamflow. As the observed period of surface and subsurface hydrological connectivity was one of the longest on record in the catchment due to very wet conditions, the results of this study denote observations of the wet extremes of the hydrological regime important for proper understanding, modelling, and prediction of streamflow in the region.