The Seton Portage River is the main source of natural inflow to Seton Lake, and is primarily fed by Anderson Lake but also by Whitecap Creek, which has its origin on the east slopes of Whitecap Mountain, the highest in the Bendor Range, and by Spider Creek, which has its origin on the north slopes of an unnamed summit to the south of Seton Lake, which happens to be the highest of the Cayoosh Range which lines the south flank of the valley.