The southeast and west sides of Wallface Mountain drain into the southern Indian Pass Brook, thence into Henderson Lake, the source of the Hudson River, which drains into New York Bay. The northern slopes of Wallface Mountain drain into the northern Indian Pass Brook, thence into the West Branch of the Ausable River, into Lake Champlain, thence into Canada's Richelieu River, the Saint Lawrence River, and into the Gulf of Saint Lawrence.