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Drainage patterns and the Indus system

Drainage of India · Part 1 / 4 · Fact-checked on 8 November 2026 · how we check

Written with AI from the sources listed at the bottom of this page, then fact-checked by a separate AI.

What drainage basins and water divides are; the dendritic, trellis, rectangular, radial and centripetal patterns; Himalayan and peninsular rivers compared and the antecedent rivers; the Indus and its tributaries the Jhelum, Chenab, Ravi, Beas and Satluj, with the projects on them; and the Indus Waters Treaty of 1960 and its abeyance in 2025.

The physiography chapter described the shape of India's land; this chapter follows the water that runs over it. In geography, drainage means the flow of water through well-defined channels, and the term used for one main river together with every stream that empties into it a drainage system. Just as India has two great landforms, it has two families of rivers: Himalayan rivers that rise in young mountains still being pushed up, and peninsular rivers that run across an ancient, worn-down plateau. Rivers decide where crops can be irrigated, where dams can make power, where cities and ports grow and where floods strike, and sharing their water is a frequent cause of disputes between states and between countries. This part sets out the basic ideas and patterns, compares the two families and then traces the westernmost Himalayan system, the Indus, with the treaty that divides its water.

The whole area whose rainfall and snowmelt end up in one river is that river's drainage basin, and the high ground that separates one basin from the next is a water divide. A raindrop falling on one side of a divide reaches one river; a drop on the other side reaches another. Between the Indus and Ganga systems the separating ground in north India rises so little that a traveller would hardly notice it; the divide runs near Ambala in Haryana, and it decides the fate of nearby rivers: those of Punjab drain to the Indus, while the Yamuna, lying just east of it, joins the Ganga. In the Peninsula the main divide is the Western Ghats: rain on their eastern side travels hundreds of kilometres to the Bay of Bengal, while rain on the western side drops quickly to the Arabian Sea. No basin in India is bigger than the Ganga's, which takes in about one-fourth of the country, and most of India's land drains towards the Bay of Bengal rather than the Arabian Sea.

Seen from above, streams join in shapes that reveal the rocks beneath them. On ground of one even type, such as the soft alluvium of the Northern Plains, nothing steers a tributary one way or another, so the streams spread out like the twigs and boughs of a tree; geographers name this the dendritic pattern, and it is the commonest one in India. Where bands of hard and soft rock run in parallel folds, the main streams carve their valleys along the weaker bands and the side streams meet them nearly square-on, giving a trellis pattern. If the bedrock is split by joints and faults meeting at right angles, streams follow these lines of weakness and turn in sharp, square bends, producing a rectangular pattern. When streams spread out like the spokes of a wheel from a high central point, the pattern is radial; Amarkantak is the classic Indian case, sending the Narmada westward and the Son north-eastward. The reverse, streams running inward into a central basin, is a centripetal pattern, seen around Loktak lake in Manipur. The table below sets these side by side.

The two families of rivers differ in almost every way. Himalayan rivers are fed by both melting snow and monsoon rain, so most are a perennial river that flows all year, swelling in summer. They are young and vigorous: in the mountains they cut deep V-shaped valleys and gorges, and on the plains they meander, shift their beds and build huge deltas; their basins are very large. Peninsular rivers depend on rain alone, so many shrink greatly or dry up in the hot season. They flow over hard, ancient rock in broad, shallow valleys, have gentle, graded profiles and fixed courses, and drain smaller basins. Some Himalayan rivers are older than the mountains themselves. The Indus, the Satluj and the Brahmaputra were already flowing before the Himalaya started to rise; as the land lifted, they kept cutting down just as fast and so stayed on their original courses; each is therefore an antecedent river, which explains the spectacular gorges where they cross the main ranges.

Of the major Himalayan rivers, the Indus lies farthest west. Its source is in Tibet near Lake Mansarovar, on the northern side of the Kailash range; from there it heads north-west into Ladakh and passes Leh along a long hollow that separates the Ladakh range from the Zaskar range. In these mountains it receives the Zaskar near Leh and, further downstream in the part of Ladakh under Pakistan's control, the Shyok, which carries the waters of the Nubra, and the Gilgit. Near Nanga Parbat, at the western end of the Himalaya, it swings south and cuts a gorge thousands of metres deep before entering the plains of Pakistan. There it is joined by the combined flow of the five rivers of Punjab, the Panjnad, near Mithankot, and it finally reaches the Arabian Sea through a delta near Karachi. The name India itself comes, through Persian and Greek, from the old name of this river, Sindhu.

Two large tributaries drain Jammu and Kashmir. The Jhelum rises at a spring at Verinag at the foot of the Pir Panjal, flows north-west through the Kashmir valley past Srinagar and through Wular lake, and then cuts a deep gorge out of the valley into Pakistan, where it joins the Chenab near Jhang. The Chenab is born at Tandi in Lahaul, Himachal Pradesh, where the Chandra and Bhaga join, and the name Chandrabhaga, used for its upper course, comes from these two headwaters. It flows through Jammu and Kashmir in deep gorges, where the Salal and Baglihar hydropower projects stand, and enters Pakistan. By volume it is the largest tributary of the Indus. Its gorge near Reasi is crossed by the Chenab rail bridge, opened in 2025 on the line that links the Kashmir valley to the rest of India's railway network and described as the world's highest railway arch bridge.

The other three rivers of Punjab rise in Himachal Pradesh. The Ravi starts in the Kullu hills west of the Rohtang Pass, flows through the Chamba valley, forms part of the India-Pakistan border and joins the Chenab in Pakistan. Rising at Beas Kund near the Rohtang Pass, the Beas flows south past Manali through the Kullu valley; lower down the Pong dam holds it back, and it ends by merging with the Satluj at Harike in Punjab; it is the only one of the five rivers that lies wholly within India. The Satluj rises at Rakas Tal near Mansarovar in Tibet, flows west roughly parallel to the Indus, and enters India through the Shipki La pass, cutting through the Himalayan ranges as an antecedent river. In Himachal Pradesh the Bhakra dam holds its waters in the Gobind Sagar reservoir. Below Harike the combined Satluj forms a stretch of the border before entering Pakistan, where the five rivers unite as the Panjnad.

Punjab's name means 'land of five waters', and its rivers made it one of the most intensively irrigated regions in the world. The land between each pair of rivers is a doab, and the canals that run across these doabs turned semi-arid plains into wheat and rice fields. After 1947 the eastern rivers became the backbone of India's own irrigation network. The Bhakra-Nangal project on the Satluj, one of independent India's first large multipurpose projects, supplies water and power to Punjab, Haryana and Rajasthan. The Pandoh dam on the Beas sends part of its water through tunnels into the Satluj, linking the two rivers. Starting at the Harike barrage at the Beas–Satluj confluence, the Indira Gandhi Canal runs for hundreds of kilometres to the south-west to bring water to the Thar desert of Rajasthan, where it has brought farming to once barren land but also problems of waterlogging and salinity.

Partition in 1947 drew the border across this river system, leaving the headwaters in India and most of the irrigated plains in Pakistan. After years of talks brokered by the World Bank, the two countries signed the Indus Waters Treaty at Karachi on 19 September 1960. It gives the waters of the three eastern rivers, the Ravi, Beas and Satluj, to India for unrestricted use, and the three western rivers, the Indus, Jhelum and Chenab, to Pakistan, while allowing India limited uses of the western rivers, such as domestic use, some irrigation and run-of-river hydropower that does not store large volumes. A Permanent Indus Commission, with a commissioner from each side, shares data and meets regularly. The treaty survived several wars, though Pakistan has objected to Indian projects such as Kishanganga and Ratle. In April 2025, after a terrorist attack at Pahalgam, India announced that it was holding the treaty in abeyance.

Putting the pieces together: the shape of the land and the type of rock decide how rivers join and which way they run, while the source of water, snow and rain or rain alone, decides whether they flow all year. The Indus system shows the Himalayan family at its clearest. Its rivers rise among glaciers, keep flowing through the dry season, cut gorges as antecedent rivers, and then spread out over flat plains where canals can lead their water far from the channel. It also shows how a river system crosses borders: one country holds the mountains and the other much of the plain, so water becomes a matter for treaties and diplomacy. Part 2 moves east to the Ganga and the Brahmaputra, the two systems that drain the greater part of north and north-east India and end in the world's largest delta.

Exam traps

• Do not picture a mountain wall between the Indus and Ganga systems: their water divide is a barely raised strip of plain near Ambala. In the Peninsula the main water divide is the Western Ghats.
• Antecedent rivers (Indus, Satluj, Brahmaputra) are older than the Himalaya and cut gorges as the mountains rose; do not confuse 'antecedent' with 'perennial'.
• Radial drainage flows OUT from a height (Amarkantak: Narmada and Son); centripetal drainage flows IN to a basin (Loktak). Students often swap them.
• The Beas is the only one of the five Punjab rivers lying wholly in India; it joins the Satluj at Harike. The Satluj and the Indus both rise in Tibet.
• Chandra plus Bhaga, uniting at Tandi in Himachal Pradesh, make the Chenab, which carries more water than any other tributary of the Indus. The Jhelum rises at Verinag and flows through Wular lake.
• Under the Indus Waters Treaty the EASTERN rivers (Ravi, Beas, Satluj) went to India and the WESTERN rivers (Indus, Jhelum, Chenab) to Pakistan, with limited Indian use. The Chenab is a western river even though it rises in India.
• The treaty was signed in 1960 at Karachi with the World Bank's help; India held it in abeyance in April 2025. It is not the Simla Agreement (1972) or the Tashkent Declaration (1966).
• Bhakra dam (Gobind Sagar) is on the Satluj; Pong dam is on the Beas; Salal and Baglihar are on the Chenab; Kishanganga is on a tributary of the Jhelum.

Recap

• A drainage basin is the area a river drains; a water divide separates basins (Indus-Ganga near Ambala; the Western Ghats in the Peninsula).
• The Ganga basin is India's largest; most of India drains to the Bay of Bengal.
• Patterns: dendritic (uniform rock), trellis (folded rock), rectangular (joints), radial (out from Amarkantak), centripetal (into Loktak).
• Himalayan rivers: snow and rain, perennial, gorges, meanders, deltas, big basins. Peninsular rivers: rain-fed, seasonal, graded valleys, fixed courses.
• Antecedent rivers: Indus, Satluj, Brahmaputra, older than the Himalaya.
• Indus: Tibet near Mansarovar, Ladakh between Ladakh and Zaskar ranges, gorge near Nanga Parbat, Panjnad at Mithankot, sea near Karachi.
• Jhelum: Verinag, Srinagar, Wular. Chenab: Chandra and Bhaga at Tandi, largest Indus tributary, Chenab rail bridge (2025).
• Ravi: Chamba. Beas: Beas Kund, Kullu, wholly in India, joins the Satluj at Harike. Satluj: Rakas Tal, Shipki La, Bhakra.
• Indus Waters Treaty, 1960: eastern rivers to India, western to Pakistan; Permanent Indus Commission; held in abeyance by India in April 2025.

Practice questions

Sources

• Central Water Commission, Ministry of Jal Shakti, and India-WRIS: river basin atlas of India, basin areas, water divides and the Indus basin — https://cwc.gov.in
• Survey of India, Department of Science and Technology: physical map of India showing the courses of the Indus and its tributaries — https://surveyofindia.gov.in
• Geological Survey of India, Ministry of Mines: geology and structure of the Himalaya and the Peninsula, and the gorges of the antecedent rivers — https://www.gsi.gov.in
• NHPC Limited and Bhakra Beas Management Board (Ministry of Power): Salal, Baglihar, Kishanganga and Ratle projects; Bhakra dam and Gobind Sagar, Pong dam, the Beas-Satluj link through Pandoh — https://www.bbmb.gov.in
• Press Information Bureau, Ministry of Railways: the Chenab rail bridge on the Udhampur-Srinagar-Baramulla rail link, opened June 2025 — https://pib.gov.in
• Water Resources Department, Government of Rajasthan: the Indira Gandhi Canal from the Harike barrage, command area, waterlogging and salinity — https://water.rajasthan.gov.in
• The Indus Waters Treaty, 1960, between India and Pakistan (signed at Karachi, 19 September 1960), with the World Bank as signatory for certain purposes — https://www.mea.gov.in/bilateral-documents.htm?dtl/6439/Indus
• Ministry of External Affairs and Press Information Bureau: decision of the Cabinet Committee on Security of 23 April 2025 to hold the Indus Waters Treaty in abeyance — https://www.mea.gov.in