Influence of subhumid climate and water table depth on groundwater recharge in shallow outwash aquifers

[1] Hypothetical one-dimensional models of unsaturated flow were used to estimate the probability of groundwater recharge to shallow, glacial outwash aquifers. Simulations were supported by field data, previous three-dimensional modeling, and cross-sectional models of water table response to precipitation events for a research area in northern Alberta, Canada. Groundwater recharge rates were found to depend on the year-to-year climate variation, the depth to the water table, and were largely driven by annual snowmelt. Simulations indicate that in summer months, when transpiration and canopy interception were considered explicitly, groundwater recharge was negligible. For water table depths less than 6 m below ground surface, the occurrence of recharge depends on climatic conditions (water deficit or surplus) of the current and previous year, and can vary from 0 to 266 mm yr(-1). For water table depths of 6 m or more, recharge will depend on climate conditions from the most recent decade, have less annual variability, and a mean annual rate of approximately 45 mm yr(-1).