Sensitivity Assessment of Simulated Evapotranspiration and Groundwater Recharge Across a Shallow Water Region for Diverse Land Cover and Soil Properties

Climate and land cover changes impact groundwater resources primarily through changes in net surface recharge. Actual evapotranspiration (ET) and the partitioning between runoff and groundwater infiltration govern the change in drainage to the aquifer (recharge supply). We discuss a comprehensive program of in-situ and model based measurement to quantify current and projected changes in recharge within the Oak Ridges Moraine (ORM), in the Greater Toronto Area. Major findings indicate that land use changes may have a considerable effect on the water balance of ORM and that the sensitivity of recharge to vegetation depends on soils. Substantial differences in annual ET estimates are noted between modeled results and those based on average annual potential evapotranspiration (PET) formulations. Further work will include the change in recharge to be compared to calibrated recharge values from existing groundwater modeling efforts in the region. Future plans to measure soil water budgets and to extend the modeling effort to include lateral flow processes are discussed.