Predicting local and regional effects of urbanisation on the subsurface water balance of north Pickering agricultural lands (Ontario)

This thesis explores the idea of quantifying expected urbanisation effects on groundwater recharge. Medium-density urban neighbourhoods were applied to a predominantly agricultural area in north Pickering, Ontario, in order to examine potential local and regional effects. Ideas of urban microclimate, urban leakage and impermeability were considered in depth. At a local (neighbourhood) scale, urban recharge values ranged from 43–134 mm/a, 57–148 mm, 110–205 mm and 140–233 mm, for natural recharge rates of 25 mm/a, 50 mm/a, 150 mm/a and 200 mm/a, respectively. A steady-state finite difference groundwater flow model (MODFLOW) was used to predict the regional watershed scale effects. Urbanisation significantly affected groundwater recharge, the water balance, velocity and direction of groundwater flow, and groundwater discharge to river flow. Both at the local and regional scale, the results suggest that recharge increase is much more of a concern than depletion.