The Indus or Sindhu river is the longest and most important river in Pakistan. A part of India until the partition in 1947 it is said to be the source of the word Hindu. Originating in the Tibetan plateau in the vicinity of Lake Mansarovar, the river runs its course through Jammu and Kashmir in both Indian Kashmir and Northern Areas, flowing through the North in a southernly direction along the entire length of the country, to merge into the Arabian Sea near Pakistan's port city of Karachi.
The total length of the river is 3200 km (1988 miles). The river has a total drainage area exceeding 450,000 square miles. The river's estimated annual flow stands at around 207 cubic kilometres. Beginning at the heights of the world with glaciers, the river feeds the ecosystem of temperate forests, plains and arid countryside. Together with the rivers Chenab, Ravi, Sutlej, Jhelum, Beas and the extinct Sarasvati River, the Indus forms the Sapta Sindhu ("Seven Rivers") delta in the Sindh province of Pakistan. It has 20 major tributaries.
The ultimate source of the Indus is in Tibet where it begins at the confluence of the Sengge and Gar rivers that drain the Nganglong Kangri and Gangdise Shan mountain ranges. The Indus then flows northwest through Ladakh-Baltistan into Gilgit, just south of the Karakoram range. The Shyok, Shigar and Gilgit streams carry glacieral waters into the main river. It gradually bends to the south, coming out of the hills between Peshawar and Rawalpindi. The Indus passes gigantic gorges (15,000-17,000 feet) near the Nanga Parbat massif.
It swiftly flows across Hazara, and is dammed at the Tarbela Reservoir. The Kabul River merges with it near Attock. The remainder of its route to the sea is in plains of the Punjab and Sind, and the river becomes slow-flowing and highly braided. It is joined by Panjnad River at Mithankot. Beyond this confluence, the river, at one time, was named as Satnad River (sat = seven, nadi = river) as the river was now carrying the waters of Kabul River, Indus River and the five Punjab rivers. Passing by Jamshoro, it ends in a large delta to the east of Thatta.