Lake McDonald is the largest of Glacier's many long lakes. NPS / Jacob W. Frank. Thanks to past ice-ages, Glacier has lots of water. Of the over 700 lakes within Glacier National park, 131 are named. Glacier's water can be considered the headwaters of the entire continent. From Triple Divide Peak, a droplet can theoretically split three ways and eventually make it to the Pacific, Atlantic, and Hudson Bay watersheds.