Can small buried-valley aquifers be an emergency water source on the Canadian Prairies?

Water security for regions that depend on mountain runoff is threatened by climate change and upstream impacts. To build resilience against water scarcity, groundwater may be an emergency or alternative water source, providing a temporary solution in the event of upstream contamination or during drought. Across western North America, buried-valley aquifers are a viable emergency water source. In Alberta, Canada, buried-valley aquifers supply domestic users; however, little is known about their capacity to supply larger water volumes. Using a regional groundwater model, this study investigated the capacity for buried-valley aquifers to supply water to the City of Edmonton, Alberta (population of 1 million) in an emergency scenario where the principal river water source was unusable. The numerical groundwater model has complex hydrostratigraphy, including glacial deposits, dipping bedrock units, and recently mapped Onoway, Beverly, and Stony buried-valley aquifers. Pumping rates varying from 10 to 375 ML/day were assessed for durations of 3, 30, and 365 days, corresponding to hypothetical response times for a range of emergencies. Although none of the aquifers could supply a sufficient volume of water for no change in service, it is possible that up to 190 ML/day could be sourced from groundwater for a period of 1 year. To achieve high rates of pumping, up to 13 production wells would be required in a buried-valley aquifer. The unique hydrogeological responses to hypothetical pumping scenarios also demonstrate the hydrogeology of buried-valley aquifers from a more holistic viewpoint as part of a regional groundwater flow system.