The Indus River is the lifeline of Pakistan. Without the Indus and its tributaries, the land would have turned into a barren desert long ago. The Indus originates in Tibet from the glacial streams of the Himalayas and enters Pakistan in the northeast. It runs generally southwestward the entire length of Pakistan, about 2,900 km (1,800 mi), and empties into the Arabian Sea. The Indus and its tributaries provide water to two-thirds of Pakistan. The principal tributaries of the Indus are the Sutlej, Beas, Chenab, Ravi, and Jhelum rivers. In southwestern Punjab Province these rivers merge to form the Panjnad (“Five Rivers”), which then merges with the Indus to form a mighty river. As the Indus approaches the Arabian Sea, it spreads out to form a delta. Much of the delta is marshy and swampy. It includes 225,000 hectares (556,000 acres) of mangrove forests and swamps. To the west of the delta is the seaport of Karachi; to the east the delta fans into the salt marshes known as the Rann of Kutch.