Groundwater and heat flow in southeastern Manitoba: Implications to water supply and thermal energy

The study of groundwater and heat flow can provide an understanding of the sustainability of groundwater supplies and geothermal energy in southeastern Manitoba. In areas where temperatures are significantly altered by groundwater flow, it is sometimes possible to estimate specific discharges. This approach has been applied in the Sandilands region of southeastern Manitoba, which is a major recharge area to regional bedrock aquifers. Temperature data have been used to estimate recharge rates to these aquifers. Subsurface heat flow in the Winnipeg area was also of interest in this study due to the exploitation of the Carbonate Rock Aquifer for air conditioning and industrial cooling. Aquifer temperatures beneath the City of Winnipeg are currently several degrees Celsius greater than those found in surrounding rural areas. Numerical modeling conducted during this study indicates that increases in temperature of up to 5°C can be attributed to heat loss from buildings. The bulk of this increase in temperatures occurs over the first few decades after building construction. Injection of thermal wastewater into the aquifer causes temperature increases of a similar magnitude, but the rate of temperature increase in the subsurface is much greater. In most thermal developments of the aquifer, the temperature at the production well increases by a few degrees Celsius in the first few years of operation. This increase in temperature makes current practises unsustainable and future development should include plans to prevent further increases in the temperature of the Carbonate Rock Aquifer.