The Indus River today flows mainly through the state of Pakistan, though its actual source is in Western Tibet. With a length of 1,800 miles (2,900 kilometers), the Indus River is one of the longest rivers in the world. It discharges into the Arabian Sea at Karachi.
The name Indus is the basis for the Roman name given to the Indian subcontinent - India, and is also the basis for the name given to modern India's largest religion - Hinduism. In Sanskrit the river is known as the Sindhu, which through Persian and Greek came down to the Romans as India.
A centre of ancient civilisation
The river valley is famed as the cradle of the enigmatic Indus Valley Civilisation. It is thought to have lasted from 4000-2500 BC, contemporary with Mesopotamia and ancient Egypt.
Major sites in the valley include the cities of Mohenjo-daro, and Harappa. These urban centres were planned, integrated townships set in a grid pattern, with drainage and other civic attributes associated with sophisticated urban civilisations.
Excavations began only in the 1920s, and initial theories suggested that the Indus Valley culture was largely dependent on riverine trade, and thus confined to the course of the Indus itself. Subsequent excavations in Pakistan, Afghanistan and Western India have extended its coverage to a vast tract of land extending from the fringes of Afghanistan to just north of Bombay (now known as Mumbai). As the script of the Indus civilisation has yet to be deciphered, and as only a small fraction of possible sites have been excavated, many facts are unsure. Early theories suggested the Indus Valley civilisation was destroyed by nomadic Aryan invaders sometime about 1500 BC. This is conjecture based on a belief that Aryan influences (and thus Hinduism) were largely pastoral, whereas the Indus Valley was largely urban.
The waters of the Indus are home to a variety of unique species, including the highly endangered Indus dolphin. Large dams across the river have affected its fragile ecosystem and the pressures of human population and industrialisation have taken their toll. Like the other major river systems of the subcontinent, the Indus, crucial to the irrigation of Punjab and Sindh provinces of Pakistan, is heavily-used, polluted and bedevilled by water disputes.