The Alas-Singkil drainage basin in northern Sumatera was studied to understand its size, shape, and river network. Data from Google Earth and field expeditions were used to analyze the watershed's characteristics. The Singkil watershed covers 12027.18 km2 and consists of 7 sub-watersheds. The main river is 368 km long and has a branching level of 4.76. The watershed has a peak discharge of 59,178 m3/sec.