Gull Lake, a lake on a hilltop, located in Manitoba, Canada, is a groundwater-sourced lake approximately 1 km2 within a closed catchment area of 4.8 km2. The lake is surrounded by over one hundred holiday homes. The Gull Lake community, wishing to preserve the lake through catchment management, requested Manitoba Sustainable Development study the area’s regional hydrodynamics. This included determining the source of the nearby spring-fed fen-type Brokenhead wetland. Quarrying activity located between the lake and the wetland was of concern.
The study drew upon existing forest cover, soils, climatic, hydrometric and bore data. Bore locations were field verified. Geology from drilling reports was analysed in Viewlogtm software and compared to soils maps, to create a three-dimensional geological model, separating aquifers and aquitards. Water level data were used to determine groundwater flow. Heads were cross referenced to topography and reports of artesian conditions, while the dominant forest cover was used to outline recharge-discharge areas. The Gull Lake water balance was determined using lake level, groundwater level and climate data dating from the 1970s.
It was determined that Gull Lake is sustained entirely by precipitation within its catchment area, and is vulnerable to drought. The lake is surrounded by an unconfined gravel aquifer, which serves as the recharge area. Groundwater flow divides and clay aquitard beneath the lake prevent basin losses due to groundwater seepage. Lake losses are primarily due to evaporation. The Brokenhead wetland source aquifer was determined to be independent of Gull Lake. Quarries were mostly located outside the Gull Lake catchment but were heavily concentrated on the Brokenhead wetland source aquifer. Quarrying had remained above the water table and did not appear to have impacted lake or wetland hydrology.
Results were presented in the form of an atlas, as a reference tool for local water managers.