Sustainability of the Bedrock Aquifer Systems in South-Central Manitoba: Implications for Large-Scale Modelling

Abstract

A three-dimensional density dependent flow and transport model was developed for the Carbonate and Sandstone Aquifers in a 60,000 square-kilometre area of south-central Manitoba. Hydrogeological properties, such as transmissivity, and aquifer response data, were collected for both aquifers. Bayesian Updating was used to determine the heterogeneous transmissivity field of each aquifer. Other parameters were designated based on collected data or typical values from the literature. The resulting model was used to evaluate several water resources scenarios within the Province of Manitoba. The sustainability over 20 years with constant pumping rates was examined. Within both aquifers, hydraulic heads declined in some regions and on average a decline in head was predicted. Model simulations were also conducted to observe the effect of flooding as this is an issue of concern in southern Manitoba. A pseudo-flood was assumed to last for a period of one month. The model was run for a period of 50 years to observe the long-term effects. The solute transport results show a concentration increase in the region south of the City of Winnipeg after one-month, indicating a decline in water quality. Drought simulations were incorporated by reducing recharge rates to the aquifers. The hydraulic heads within the Carbonate Aquifer decline within the Interlake region with a maximum decline within the Sandilands region southeast of the City of Winnipeg. As might be expected, the effects of reduced recharge on the entire aquifer sequence are significant.