Estimating Deep Recharge Rates Beneath an Interlobate Moraine Using Temperature Logs

The Sandilands area of southeastern Manitoba contains an interlobate moraine that is a major ground water recharge area. Underlying the highly permeable sediments of the moraine are up to 100 m of till and the subcrop of the Winnipeg Formation, which contains a major sandstone aquifer. Ground water flow within the till is examined using high-resolution temperature profiles and solutions to the differential equation for heat flow in porous media. These analyses indicate that recharge to the sandstone aquifer is occurring at a rate of approximately 2 2 10–8 m/sec beneath the moraine, which is in agreement with recharge rates determined by conventional ground water hydraulics (10–7 to 10–10 m/sec) and another study using multiple environmental tracers (1 2 10–9 to 6 2 10–9 m/sec). The use of temperature to determine ground water flux is not limited by half-lives as many environmental tracers are, and this allows for cost-effective estimation of recharge and discharge rates over longer periods.