Macomb Mountain stands within the watershed of the Schroon River, which drains into the Hudson River, and into New York Bay.The east and northeast sides of Macomb Mtn. drain into West Mill Brook, thence into the Schroon River.The northwest sides of Macomb Mtn. drain into Lillian Brook, thence into the East Inlet of Elk Lake, source of The Branch of the Schroon River.The southwest side of Macomb drains into Slide Brook, thence into the East Inlet of Elk Lake.The southeast slopes of Macomb drain into Niagara Brook, thence into The Branch of the Schroon River.