TheIndus Basin is the part ofAsia drained by theIndus River and its tributaries. The basin covers an area of 1,120,000 km2 (430,000 sq mi)[1][a] traversing four countries:Afghanistan,China,India, andPakistan, with most of the area lying predominantly in the latter two countries.
The Indus River has two main tributaries: thePanjnad—formed by successive confluences ofSutlej,Beas,Ravi,Jhelum, andChenab Rivers—and theKabul, containing the waters of theSwat andKunar Rivers, as well as others. The Indus and Sutlej originate on theTibetan Plateau, the Ravi, Beas, Chenab and Jhelum originate in the Indian westernHimalayas, and the Kabul and its tributaries originate in theHindu Kush of eastern Afghanistan and northern Pakistan.
The Indus Basin lies in four countries: Pakistan, India, China, and Afghanistan. The largest portion of the basin, at 47%, lies in Pakistan while India contains the second biggest share at 39%. China and Afghanistan contain the remaining 14%.[3][4] The Indus Basin spans the length of Pakistan, constitutes a majority (65%) of its area and forms part of all provinces and territories of the country:Punjab,Sindh,Khyber Pakhtunkhwa,Balochistan,Azad Jammu and Kashmir, andGilgit-Baltistan, with all except Sindh and Balochistan located entirely within the basin. In India, the Indus Basin forms around 14% of the country but makes up the bulk of thenorthwestern part of the country including thestates andunion territories ofPunjab,Himachal Pradesh,Jammu and Kashmir,Ladakh,Haryana, and westernRajasthan.
The Indus Basin consists of various topographical regions. A large part of thedrainage basin is mountainous, and around 40% of its area lies above an elevation of 2,000 m (6,600 ft).[4] The basin can be divided into two wide physiographic divisions: the upper basin consisting of the mountainous regions of the Himalaya,Karakoram, Hindu Kush,Shiwalik,Suleiman, andKirthar ranges; and the lower basin consisting of theIndus Plains including the alluvial plains of thePunjab and Sindh.[3] Most of the basin is arid or semi-arid, with the exception of the Himalayan foothills which receive significant rainfall.
The basin contains the largest amount of perennialglacial ice outside of the polar regions.[1] A majority of the runoff in the Indus drainage basin comes frommeltwater—glacial melt contributing 41% andsnowmelt providing 22%—of the Himalaya, Hindu Kush and Karakorum mountains.[5] Rainfall contributes the remaining. On average, a little over half of the entire annual flow is received within the three months from July to September, whenmonsoonal rains combine with meltwater.[6] As a result, the region has historically seen substantial flooding in the summer months.[7]
The Indus drainage supports some 237 million people. Pakistan contains a majority of the people living in the Indus Basin (around 61% of total) most of whom heavily depend on its rivers for their water needs. India contains another large portion (35%) of the Indus Basin's population. The remaining 4% live mostly in Afghanistan, representing a little less than a quarter of the country's population.[2] The Indus Basin is the second mostwater stressed basin of the world.[8]
93% of the water of the Indus Basin is used for irrigation of agricultural land.[9] Many of the rivers of the Indus River system are dammed to create large reservoirs of water: in India the Satluj river is dammed atBhakra creating theGobind Sagar reservoir, the Beas atPong creating theMaharana Pratap Sagar reservoir and the Ravi atThein creating the Ranjit Sagar reservoir; while in Pakistan the Jhelum river is dammed atMangla and the Indus is dammed atTarbela andChashma creating the Mangla,Tarbela and Chashma reservoirs respectively. The water from these reservoirs as well as from various barrages are diverted to irrigate 26 million hectares (mha) of agricultural land, 16 mha in Pakistan and 10 mha in India.[10]
