 Mt.Tripyramid is drained on the west side by Slide Brook and Avalanche Brook, thence into the Mad River, Pemigewasset River, Merrimack River, and into the Gulf of Maine at Newburyport, Massachusetts.Tripyramid is drained on the east side by Sabbaday Brook, thence into the Swift River, Saco River, and into the Gulf of Maine at Saco, Maine.