A geological rarity, Medicine Lake is perhaps best described as a sinking lake that has holes in the bottom and functions rather like a plugless bathtub. In summer, when the run-off is high, the lake fills more quickly than it can drain away, and the body of water appears deep and expansive. In winter, as the run-off slows, the water empties, causing the lake to shrink to the size of a small stream.
What bewildered Aboriginals and other early visitors was the apparent lack of any water outlet. In fact, the water flows out of the lake via a series of small holes on its floor, before passing into a complex underground cave system. The river then re-emerges 16km (10 miles) downstream near Maligne Canyon. In the 1950s a ferry service across the lake was briefly attempted, but efforts to plug the holes with sandbags, mattresses and bundles of magazines all proved futile.
