A three-dimensional groundwater flow model of the Waterloo Moraine for water resource management

Abstract

The Waterloo Moraine has been a drinking water source for the people of Waterloo Region for over a century and, as such, it has been the subject of numerous geologic and hydrogeologic studies for over five decades. Two of the companion papers in this Special Issue describe the evolution of the hydrogeological conceptualization of the Moraine sediments and the history of groundwater modelling of the Moraine groundwater flow system, respectively. This paper builds on those findings and describes the development and calibration of a three-dimensional finite-element groundwater flow model. A key aspect in the development was the implementation of a spatial geodatabase that links the conceptual hydrogeological framework with the numerical groundwater flow model. The model was based on a detailed characterization of the groundwater and surface water systems, and calibrated to available data under average (steady-state) and variable (transient) pumping and climate conditions. Following model development and calibration, the model was used to conduct a detailed water budget and risk assessment study that compared groundwater demands to available supplies within the Central Grand River Watershed, a subwatershed of the main Grand River Watershed. Several scenarios involving future municipal water demands and potential reductions in groundwater recharge due to planned land-use development were simulated, leading to the conclusion that the projected municipal water demand to 2031 can be supplied by the existing system of wells without causing a significant reduction in groundwater discharge to ecologically sensitive streams and wetlands. The model was also applied to delineate the capture zone for a well field in the Region under conditions of uncertainty, demonstrating a methodology that could be applied to other well fields. The model provides an effective and efficient tool for Regional water managers for the long-term sustainable management of the groundwater resources of the Waterloo Moraine.