Drought impacts on Canadian prairie wetland snow hydrology

Droughts affect the Canadian prairies on a regular basis. The drought of 1999-2005 was the most recent one and was the most severe on record for part of the region. It was characterized by lack of precipitation, desiccation of agricultural soils, decline in groundwater tables and depletion of surface water supplies. The effects on wetlands were particularly severe, with many wetlands completely drying out. The physically based cold regions hydrological modelling (CRHM) platform was used to analyse the impacts of this recent drought on water flow to and storage within a small Canadian prairie Weiland. Model simulations were conducted for a small closed basin for the drought period of 1999-2005 and the relatively wet period of 2005-2006. The basin consists of a cultivated upland, draining into a glacially formed pothole depression with no outlet. The Weiland fills the depression in wet years and is underlain by a heavy glacial till that impedes groundwater exchange. Results from the observations and model outputs showed that much lower precipitation and snow accumulation, shorter snow-covered duration, enhanced winter evaporation, and much lower discharge to the Weiland from basin snowmelt runoff developed in the severe drought years of 1999-2002. As a result, there were only 14.9, 3.7, and 14-4 mm of snowmelt runoff for the springs of 2000, 2001, and 2002, respectively. Compared to the 68-2 mm of melt-water discharge in the spring of 2006, discharge to the wetland was 78, 95, and 79% less for these years. This is consistent with the observed water level in the Weiland, which shows dramatic decline over this period. CRHM was used to investigate the potential impact of snow management as a tool to enhance runoff to the Weiland during droughts. Model runs parameterized with suppressed vegetation in the cultivated land surrounding the wedand showed increased blowing snow transport to the wetland from an area exceeding the basin area that resulted in greater snow accumulation in and melt-water supply to the Weiland. Copyright (c) 2008 John Wiley & Sons, Ltd.