Indus River

Trans-Himalayan river of southern Asia.

It is one of the world's longest rivers, with a length of 1,800 mi (2,900 km). Its annual flow of 272 billion cu yd (207 billion cu m) is twice that of the Nile. It rises in southwestern Tibet and flows northwest through valleys of the Himalayas. After crossing into the Kashmir region, it continues northwestward through the Indian-and Pakistani-administered areas and then turns south into Pakistan. Swelled by tributaries from the Punjab region, including the Jhelum, Chenab, Ravi, Beas, and Sutlej rivers, it widens and flows more slowly. It has supplied water for irrigation on the plains of Pakistan since early times.

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▪ river, Asia

Introduction

 great trans-Himalayan (Himalayas) river of South Asia and one of the longest rivers in the world, having a length of 1,800 miles (2,900 kilometres). It has a total drainage area of about 450,000 square miles (1,165,500 square kilometres), of which 175,000 square miles lie in the Himalayan mountains and foothills and the rest in the semiarid plains of Pakistan. The river's annual flow is about 272 billion cubic yards (207 billion cubic metres)—twice that of the Nile and three times that of the Tigris and Euphrates combined. The river's name comes from the Sanskrit word sindhu (“river” or “stream”). It is mentioned in the Rigveda, the earliest (c. 1500 BC) chronicles and hymns of the Aryan peoples of ancient India, and is the source of the country's name.

Physical features

      The river rises in southwestern Tibet at an altitude of about 18,000 feet (5,500 metres). For about 200 miles it flows northwest, crossing the southeastern boundary of Jammu and Kashmir at about 15,000 feet. A short way beyond Leh, in Ladākh, it is joined on its left by its first tributary, the Zāskār. Continuing for 150 miles in the same direction, the Indus is joined by its notable tributary the Shyok on the right bank. After its confluence with the Shyok and up to the Kohistān region, it is fed by mighty glaciers on the slopes of the Karakoram Range, the Nānga Parbat (Nanga Parbat) massif, and the Kohistān highlands. The Shyok, Shigar, Gilgit, and other streams carry the glacial waters into the Indus. Since the present-day precipitation of snow in this region is not sufficient to feed these great rivers of ice, it is fairly certain that the giant ice streams of the Karakoram are survivors of the last ice age of the Himalayas.

 The Shigar joins the Indus on the right bank near Skārdu in Baltistān. The Gilgit, farther down, is another right-bank tributary, joining it at Bunji. Some miles farther downstream, the Astor River joins as a left-bank tributary. The Indus then flows west, crosses the Kashmir border, and turns south and southwest to enter Pakistan. There it skirts around the Nānga Parbat massif (26,660 feet) in gorges as deep as 15,000 to 17,000 feet and 12 to 16 miles wide. Trails cling grimly to precipitous slopes overlooking the river from elevations of 4,000 to 5,000 feet.

      After emerging from this region of high altitude, the Indus flows as a rapid mountain stream between the Swāt and Hazāra areas in Pakistan until it reaches the reservoir of Tarbela Dam. The Kābul River joins the Indus just above Attock, where the Indus flows at an elevation of 2,000 feet and is crossed by the first bridge carrying rail and road. Finally, it cuts across the Salt Range near Kālābāgh to enter the Punjab Plain.

      The Indus receives its most notable tributaries from the eastern Punjab Plain. These five rivers—the Jhelum (Jhelum River), the Chenāb (Chenāb River), the Rāvi (Rāvi River), the Beās (Beas River), and the Sutlej (Sutlej River)—give the name Punjab (“Land of Five Rivers”) to the land shared between Pakistan and India.

      After receiving the waters of the Punjab rivers, the Indus becomes much larger and, during the flood season (July–September), is several miles wide. It flows there at an elevation of about 260 feet. Its slow speed at this stage results in its accumulated silt being deposited on its bed, which is thus raised above the level of the sandy plain; indeed, most of the plain in Sindh has been built up by alluvium laid down by the Indus. Embankments have been built to prevent flooding, but occasionally these give way, and large areas are destroyed by inundation. Such floods occurred in 1947 and 1958. During heavy flooding the river sometimes changes its course.

      Near Thatta (Tatta) the Indus begins its deltaic stage and breaks into distributaries that join the sea at various points south-southeast of Karāchi. The delta covers an area of 3,000 square miles or more and extends along the coast for about 130 miles. The uneven surface of the delta area is marked by a network of existing and abandoned channels. The coastal strip, from about 5 to 20 miles inland, is flooded by high tides.

Hydrology

      The principal rivers of the Indus River system are snow-fed. Their flow varies greatly at different times of the year: the discharge is at a minimum during the winter months (December to February), there is a rise of water in spring and early summer (March to June), floods occur in the rainy season (July to September), and occasionally there are devastating flash floods. The Indus and its tributaries receive all their waters in the upper hilly parts of their catchments. Therefore, their flow is at a maximum where they emerge out of the foothills, and little surface flow is added in the plains, where much loss of water occurs because of evaporation and seepage. On the other hand, some water is added by seepage in the period after the monsoon months. In the main stream of the Indus, the water level is at its lowest from mid-December to mid-February. After this the river starts rising, slowly at first and then more rapidly at the end of March. The high-water level usually occurs between mid-July and mid-August. The river then falls rapidly until the beginning of October, when the water level subsides more gradually. Annually, the Indus carries about 144 billion cubic yards—slightly more than half of the total supply of water in the Indus River system. The Jhelum and Chenāb combined carry roughly one-fourth; and the Rāvi, Beās, and the Sutlej combined constitute the remainder of the total supply of the system.

      There is considerable physiographic and historical evidence to prove that since the dawn of civilization—at least since the days of Mohenjo-daro culture, 4,000 years ago—the Indus, from the southern Punjab to the sea, has been shifting its course. It is confined between limestone ridges at Rohri-Sukkur, but thereafter it has wandered, shifting generally to the west, particularly in its deltaic sector, so that about 200 years ago it began to flow into the Rann of Kachchh (Kutch). In upper Sindh the Indus has shifted westward a distance of about 10 to 20 miles in the last seven centuries. The river is now held back to some extent by higher ground from Sehwān to Thatta at the head of the delta, but the possibility of future shifting cannot be ruled out. There is also evidence of the shifting of the Chenāb, Rāvi, Beās, and Sutlej rivers during the historical period.

Climate

      From its source to its mouth, the annual rainfall in the Indus region varies between 5 and 20 inches (125 to 500 millimetres). Except for the mountainous section of Pakistan, the Indus valley lies in the driest part of the subcontinent. Northwestern winds sweep the upper Indus valley in winter and bring 4 to 8 inches of rainfall—vital for the successful growing of wheat and barley. The mountainous region of the valley receives precipitation largely in the form of snow. A large amount of the Indus' water is provided by melting snows and glaciers of the Karakoram, Hindu Kush, and Himalayan mountains. The monsoon rains (July to September) provide the rest of the flow. The climate of the Indus valley ranges from that of the dry semidesert areas of Sindh and lower Punjab to the severe high mountain climate of Kohistān, Hunza, Gilgit, Ladākh, and western Tibet. January temperatures there are below freezing point in the north, while July temperatures reach a maximum of about 100° F (38° C) in Sindh and Punjab. Jacobābād, one of the hottest spots on Earth, is situated west of the Indus River in upper Sindh and often records summer maximums of 120° F (49° C).

Plant and animal life

      There is a close relationship between climate and vegetation in the Indus valley. In the lower Indus region of Sindh, desert conditions prevail 10 to 25 miles away from the river, and the area is dominated by sand and poor grass cover. Irrigation by floods or canals permits some cultivation. In upper Sindh and Punjab, overgrazing and felling timber for fuel has led to destruction of much of the natural vegetation. Further, prolonged human interference with natural drainage and deforestation on the Shiwāliks has led to marked deterioration in groundwater conditions and so in vegetation. It appears that in prehistoric and earlier historic times the middle Indus region was more wooded than it is at present: accounts of Alexander the Great's Indian campaigns (c. 325 BC) and records of Mughal hunts in the 16th century and after suggest considerable forest growth. Even today, in the Indus Plain not far from the river, there are thorn forests of open acacia and bush and undergrowth of poppies, vetch, thistles, and chickweed. Near the river are stretches of tall pampalike grass, and streams and canals are often lined with tamarisk trees and some dense scrub, but there is nowhere a natural forest. Efforts at reforestation in some parts of the Thal area in the Punjab east of the Indus have been successful. Cultivated areas close to the river have many trees, and the strip below the mountains has something of the appearance of parkland. Coniferous trees abound in the northern areas of the Indus region.

      The Indus is moderately rich in fish. The best-known variety is called hilsa and is the most important edible fish found in the river. Thatta, Kotri, and Sukkur, all in Sindh, are important fishing centres. Between the Swāt and Hazāra areas the river is noted for trout fishing. Fish farming has become important in the reservoirs of dams and barrages. Near the mouth of the Indus—for about 150 miles along the coast—there are numerous creeks and a shallow sea beyond. The area is rich in marine fish, the most important catches including pomfrets and prawns, which are obtained from November to March. A modern fish harbour has been built near the port of Karāchi, providing cold storage and marketing. An export trade in prawns has developed, and sea fish are marketed in different parts of Pakistan.

The people

      Peoples living along the upper reaches of the Indus (e.g., Tibetans, Lādakhī, and Bāltī) show affinities with Central rather than South Asia. They are of Asiatic stock, speak Tibetan languages, and practice Buddhism (although the Bāltī have adopted Islām). Pastoralism is important in the local economy. In the main Himalayan ranges, areas drained by the headwaters of the major Indus tributaries form a transitional zone where Tibetan influences mingle with those of the Indian pahāṛī (hill) region.

      Elsewhere in the Indus valley the inhabitants are of Indo-European descent and are Muslims, reflecting repeated incursions of peoples entering the Indian subcontinent from the west over several millennia. The rugged mountains of western Kashmir are inhabited by Dardic-speaking groups (Kafīr, Kohistānīs, Shīnās, and Kashmirī Gūjar), whose languages, like most in the region, are Indo-European in origin. In the Hunza River valley, the long-lived Burusho speak a language (Burushaskī) that has no known ties to other languages in the area. These groups combine herding with irrigation-based cultivation.

      Pathans, speaking Pashto and closely related to the tribes of Afghanistan, are found in northwestern Pakistan. The Yūsufzai are the largest of the Pathan tribes, others being the Afrīdī, Muhmand, Khattak, and Wazīr. In the mountainous tribal areas of Pakistan's North-West Frontier Province, the fiercely independent Pathans retain their traditional tribal structure and political organization.

      West of the Indus River, the lands stretching from Quetta to the Makrān coast form the territory of the Balochi tribes. Speaking a language derived from Old Persian, the Balochi are a nomadic people, herding camels, cattle, sheep, and goats, although some have adopted settled agriculture. Nomadic Brāhūī tribes around Kalāt appear to be remnants of an earlier immigrant group from the Mediterranean region, who since have been supplanted by more recent migrants into the Indus valley. Brāhūī is a Dravidian-based language related to those of southern India.

      The well-watered northern Indus plains are settled by agricultural groups who speak Punjabi and related dialects and who form the most numerous of the Indus valley peoples. Language, race, and tribal organization play a less important role in differentiating groups there. The major distinguishing feature among Punjabi peoples is caste, although without the religious and ritual connotations of the Hindu system. Muslim Jats and Rajputs are important Punjabi communities.

      The lower Indus valley is inhabited by agricultural peoples who speak Sindhi and related dialects. Many cultural traits in the region appear to be of considerable antiquity, and the Sindhi pride themselves on their regional distinctiveness. Karāchi, though in Sindh, is predominantly an Urdu-speaking city settled by Punjabis and muhajir, immigrants from India who arrived in Pakistan after partition of the subcontinent in 1947.

The economy

Irrigation

      Irrigation from Indus waters has provided the basis for successful agriculture since time immemorial. Modern irrigation engineering work commenced around 1850, and large canal systems were constructed by the British administration. In many cases old canals and inundation channels in Sindh and Punjab were revived and modernized; thus the greatest canal irrigation system in the world was created. At partition in 1947, the international boundary between India and West Pakistan cut the irrigation system of the Bāri Doab and the Sutlej Valley Project, originally designed as one scheme, into two parts. The headwork fell to India while the canals ran through Pakistan. This led to a disruption in the water supply in some parts of Pakistan. The dispute that thus arose and continued for some years was resolved through the mediation of the World Bank by a treaty between Pakistan and India (1960) known as the Indus Waters Treaty. According to this agreement, the flow of the three western rivers of the Indus basin—the Indus, Jhelum, and Chenāb (except a small quantity used in Kashmir)—is assigned to Pakistan, whereas the entire flow of the three eastern rivers—the Rāvi, Beās, and Sutlej—is reserved exclusively for India.

      In India a number of dams, barrages, and link canals have been built to distribute water from the eastern Indus tributaries to the Punjab and neighbouring states. The Harike Barrage, at the confluence of the Beās and Sutlej, channels water into the Indira Gandhi (Rājasthān) Canal, which runs for some 400 miles to the southwest to irrigate some 1.5 million acres (607,000 hectares) of desert in western Rājasthān. The main canal was completed in 1987.

      Pakistan has diverted water from its western rivers to replace reduced flows in the Sutlej Valley Project region. A number of new link canals and barrages have been completed by the Pakistan Water and Power Development Authority. The biggest of these link canals is the Chashma-Jhelum link joining the Indus River with the Jhelum River, with a discharge capacity of some 21,700 cubic feet (615 cubic metres) per second. Water from this canal feeds the Haveli Canal and Trimmu-Sidhnāi-Mailsi-Bahāwal link canal systems, which provide irrigation to the Multān and Bahāwalpur divisions in the lower Punjab.

      The Indus Waters Treaty also made provision for the construction of two major dams in Pakistan. The Mangla Dam on the Jhelum River, near the town of Jhelum, has a crest length of about 10,300 feet and a maximum height of more than 450 feet and is one of the largest rolled earth-fill dams in the world. Mangla Reservoir, created by the dam, is 40 miles long and has an area of 100 square miles. The project also generates some 800 megawatts of hydroelectricity. The reservoir is being developed as a fishing centre and a tourist attraction as well as a health resort.

      A second gigantic project is the Tarbela Dam on the Indus, 50 miles northwest of Rāwalpindi. The dam, of the earth- and rock-filled type, is 9,000 feet long and 470 feet high, and its reservoir is 50 miles long. The dam's generating capacity is some three times that of the Mangla Dam, and its total potential is considerably greater.

      On the Indus itself there are several important headworks, or barrages, after the river reaches the plain. In the mountainous region the principal waterways west of the Indus are the Swāt Canals, which flow from the Swāt River, a tributary of the Kābul River. These canals help in the irrigation of the two chief crops of the area, sugarcane and wheat. The Warsak multipurpose project on the Kābul River, about 12 miles northwest of Peshāwar, provides irrigation for food crops and fruit orchards in the Peshāwar valley and is designed to produce 240,000 kilowatts of electricity. In the plains region the Kālābāgh, or Jinnah, Barrage controls the system of canals in the Thal Project, the development authority for which was set up in 1949. The project irrigates a former desert area. It is an integrated project aimed at extending agriculture, developing rural industry, and promoting the settlement of population in villages and towns. Farther downstream is the Chashma Barrage. Still farther the Taunsa Barrage, designed for the irrigation of land in the Dera Ghāzi Khān and Muzaffargarh districts, also produces about 100,000 kilowatts of electricity. Within the Sindh there are three major barrages on the Indus—Guddu, Sukkur, and Kotri, or Ghulām Muḥammad. The Guddu Barrage is just inside the Sindh border and is some 4,450 feet long; it irrigates cultivated land in the region of Sukkur, Jacobābād, and parts of Lārkāna and Kalāt districts. The project has greatly increased the cultivation of rice, but cotton also has become a major crop on the left bank of the river and has replaced rice as a cash crop. The Sukkur Barrage was built in 1932 and is about one mile long. The canals originating from it serve a cultivable area of about five million acres of land producing both food and cash crops. The Kotri Barrage, also known as the Ghulām Muhammad Barrage, was opened in 1955. It is near Hyderābād and is nearly 3,000 feet long. The right-bank canal provides additional water to the city of Karāchi. Sugarcane cultivation has been extended, and crop increases have been achieved in the cultivation of rice and wheat.

      Experience in the Indian subcontinent and elsewhere has shown that canal irrigation, unless carefully controlled, can cause much damage to the cultivated land. The water in the unlined canals seeps through the soil and raises the water table so that the soil becomes waterlogged and useless for cultivation. As irrigation by canals has expanded in the Indus and its tributary lands, in some areas underground water has appeared on the surface to form shallow lakes. Elsewhere the water has evaporated in the intense summer heat, leaving behind layers of salt that make crop production impossible. Steps have been taken to provide adequate drainage systems to avoid waterlogging and salt buildup.

Navigation

      Until about 1880 the Indus and the other Punjab rivers carried some navigation, but the advent of the railways and expansion of irrigation works has eliminated all but small craft that ply the lower Indus in Sindh. There are fishing boats on the lower Indus, and the upper reaches of rivers and canals above the first railway crossing are now used for floating timber down from the foothills of Kashmir.

Nafis Ahmad Deryck O. Lodrick

Additional Reading

Descriptions of the Indus are found in surveys of the corresponding regions, such as H.T. Lambrick, Sind: A General Introduction, 2nd ed. (1975); Richard F. Nyrop (ed.), Pakistan: A Country Study, 5th ed. (1984); and Kazi S. Ahmad, A Geography of Pakistan, 3rd ed., rev. by K.U. Kureshy (1972). Works on the Indus itself include Jean Fairley, The Lion River: The Indus (1975), a history of civilization in the Indus valley and of its discovery and exploration; Aloys Arthur Michel, The Indus Rivers: A Study of the Effects of Partition (1967), a discussion of the problem of water resources in the Indus valley; Nazir Ahmad and Ghulam Rasul Chaudhry, Irrigated Agriculture of Pakistan (1988); A.H. Siddiqi, “Society and Economy of the Tribal Belt in Pakistan,” Geoforum, 18(1):65–79 (1987); and Geoffrey Moorhouse, To the Frontier (1984), a descriptive work.Deryck O. Lodrick

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