Medicine Lake

An extensive system of interconnected caves and channels beneath Medicine Lake, in Jasper National Park, creates a remarkable annual cycle. In the summer the lake fills, but by autumn the lake drains through holes in the lake bottom into one of the largest subsurface river and cave systems in the world.

Medicine Lake was formed when a major rockslide from the nearby Colin Range tumbled into Maligne Valley, damming the flow of much of Maligne River. The only outlets for the water became holes in the lake bottom, called sinkholes, located along the northwest and northeast shores. The water now drains through these into subsurface river channels at an incredible rate of 24,000 litres per second!

Depending on the season, Medicine Lake has the reputation of being either one of the largest or smallest lakes in Jasper National Park. In the spring, runoff exceeds the drainage capacity of the sinkholes and the lake fills to a depth of 18 metres. By autumn, more water drains out through the holes than flows into the lake and Medicine Lake slowly dwindles. All that is left is a tiny stream trickling across the mudflat.