Walupt Lake is a ribbon lake situated near the end of a long glacial valley. The main inflow to Walupt Lake is the perennial, snowmelt-fed Walupt Creek, which flows out of a long valley into the east end of the lake. Other small streamlets flow into the lake from the steep valley walls above. The lake's watershed encompasses of land in the southern Goat Rocks. Besides the lake itself, the watershed comprises forest and otherwise unproductive land.