Tarbela Reservoir is long, with a surface area of . The reservoir initially stored of water, with a live storage of , though this figure has been reduced over the subsequent 35 years of operation to due to silting. The Maximum Elevation of the reservoir is 1550 feet (472.44 meter) above MSL and Minimum Operating Elevation is 1392 feet (424.28 meter) above MSL. The catchment area upriver of the Tarbela Dam is spread over of land largely supplemented by snow and glacier melt from the southern slopes of the Himalayas. There are two main Indus River tributaries upstream of the Tarbela Dam. These are the Shyok River, joining near Skardu, and the Siran River near Tarbela.