The northeast slopes of Big Indian Mountain drain into Elk Bushkill, thence into Esopus Creek, the Hudson River, and into New York Bay.

The north end of Big Indian Mountain drains into Shandaken Brook, thence into Dry Brook, the East Branch of the Delaware River, and into Delaware Bay.

The west side of Big Indian Mtn.

The southern slopes of Big Indian Mountain drain into Biscuit Brook and Pigeon Brook, thence into the West Branch of the Neversink River, and the Delaware River.

Big Indian Mountain is within the Big Indian–Beaverkill Range Wilderness Area, part of New York's Catskill State Park.