Drainage Systems of India: Himalayan and Peninsular Rivers

What a drainage system is

A drainage system is the network of channels through which rivers carry water from an area. The area drained by one river and its tributaries is its drainage basin or catchment, and the high ground separating two basins is a water divide. India's rivers are usually grouped into two systems that differ in age, origin and behaviour: the Himalayan rivers and the Peninsular rivers. About 77 per cent of India's drainage area drains into the Bay of Bengal and about 23 per cent into the Arabian Sea. The Delhi ridge, the Aravallis and the Sahyadri form the main water divide between the two.

Drainage patterns

A river is called antecedent if it existed before the mountains rose and kept cutting down as they rose – the Indus, Sutlej and Brahmaputra (Tsangpo–Dihang) are classic examples, cutting deep gorges through the Himalaya. A river that follows the slope of a new landform is consequent.

Himalayan vs Peninsular rivers

The Indus system

The Indus rises near Lake Mansarovar in Tibet (Bokhar Chu glacier), flows north-west through Ladakh, cuts a deep gorge near Gilgit, and enters Pakistan. Its total length is about 2,880 km, of which roughly 1,114 km lie in India. Its main tributaries:

• Right bank: Shyok, Gilgit, Hunza, Kabul, Kurram.
• Left bank (the five rivers of Punjab): Jhelum (rises at Verinag, flows through Wular Lake), Chenab (largest, formed by Chandra and Bhaga), Ravi, Beas (rises near Rohtang, joins Sutlej at Harike) and Sutlej (rises at Rakas Tal near Mansarovar, enters India through Shipki La; Bhakra–Nangal dam).

Under the Indus Waters Treaty (1960), brokered by the World Bank, India got the eastern rivers (Ravi, Beas, Sutlej) and Pakistan the western rivers (Indus, Jhelum, Chenab), with India allowed limited non-consumptive use such as run-of-the-river hydropower. In April 2025, after the Pahalgam terror attack, India announced it was holding the treaty "in abeyance".

The Ganga system

The Ganga begins as the Bhagirathi at the Gangotri glacier (Gaumukh); it meets the Alaknanda at Devprayag to take the name Ganga. Its length in India is about 2,525 km and its basin covers about 8.6 lakh square kilometres in India – the largest river basin in the country, spread over 11 states.

The Alaknanda itself collects the Dhauliganga and Vishnuganga (at Vishnuprayag), the Pindar (at Karnaprayag), the Mandakini (at Rudraprayag) and the Nandakini (at Nandprayag) – the Panch Prayag.

• Left-bank tributaries (from the Himalaya): Ramganga, Gomti, Ghaghara, Gandak, Kosi ("Sorrow of Bihar", because of frequent course changes and floods), Mahananda.
• Right-bank tributaries: the Yamuna (from Yamunotri; the longest tributary, joining at Prayagraj) with its own tributaries Chambal, Sindh, Betwa and Ken from the peninsula; and the Son, which rises at Amarkantak.

Below Farakka, the main stream enters Bangladesh as the Padma, while the Bhagirathi–Hooghly distributary flows past Kolkata. The Padma joins the Brahmaputra (called Jamuna there) and then the Meghna, forming the Sundarbans delta.

The Brahmaputra system

The Brahmaputra rises in the Chemayungdung glacier near Mansarovar and flows east across Tibet as the Tsangpo. Near Namcha Barwa it takes a sharp U-turn and enters Arunachal Pradesh as the Siang or Dihang. In Assam it is joined by the Dibang and Lohit and becomes the Brahmaputra, a braided river that carries a huge load of silt and floods often. Its tributaries include the Subansiri (left in Arunachal, hosting a major hydro project), Manas, Teesta and the Kameng. It has a total length of about 2,900 km. China's announced mega-dam on the Yarlung Tsangpo in Medog (construction began in 2025) is a concern for India and Bangladesh.

The Peninsular rivers

East-flowing rivers (form deltas):

West-flowing rivers (form estuaries):

• Narmada – rises at Amarkantak, flows west through a rift valley between the Vindhyas and Satpuras; marble rocks and Dhuandhar falls at Jabalpur; Sardar Sarovar dam.
• Tapi – rises at Multai in Betul, flows through a parallel rift valley; Surat lies on it.
• Sabarmati, Mahi and Luni (inland, ends in the Rann of Kachchh), plus many short swift rivers of the Western Ghats such as the Sharavati (Jog Falls), Mandovi and Periyar.

Why drainage matters

Rivers decide where people farm and settle, where cities grow, and where dams can generate power. India uses a large share of its surface water for irrigation, but storage is uneven: the Ganga–Brahmaputra basins hold most of the water while western and southern basins face scarcity. This mismatch drives proposals such as the Interlinking of Rivers programme – the Ken–Betwa link was the first project to start (foundation stone laid in December 2024). Floods in the Ganga–Brahmaputra plains, droughts in the peninsula, pollution (the Namami Gange programme), and inter-state water disputes (Kaveri, Krishna, Mahadayi) are all linked to the nature of these drainage systems.

Lakes, waterfalls and river regimes

India's lakes have very different origins. Glacial lakes such as Tso Moriri and many high tarns lie in the Himalaya; Wular in Kashmir is a tectonic lake and one of the largest freshwater lakes in Asia; Lonar in Maharashtra was formed by a meteorite impact in basalt; Sambhar and Didwana are inland salt lakes of Rajasthan; Chilika, Pulicat and Vembanad are lagoons or backwaters along the coasts; and Kolleru is a freshwater lake between the Godavari and Krishna deltas. Many artificial reservoirs such as Gobind Sagar (Bhakra) and Nagarjuna Sagar are now just as important for water supply.

The regime of a river is the pattern of its flow through the year. Himalayan rivers have two peaks – early summer, when snow melts, and the monsoon months – so they never dry up. Peninsular rivers rise sharply in the monsoon and shrink in the dry season, which is why reservoirs are vital in the plateau. The Kaveri is an exception because it receives rain from both monsoons. Waterfalls on plateau rivers, such as Jog (Sharavati), Shivasamudram (Kaveri), Dhuandhar (Narmada) and Hundru (Subarnarekha), mark the edges of hard rock and are used for hydropower.

Mains practice question

Compare the characteristics of the Himalayan and Peninsular river systems. How do these differences affect their utility for irrigation, navigation and hydropower? (250 words)

Answer framework

• Intro: two systems, 77:23 split of drainage.
• Differences: source, perennial vs seasonal, age, course, mouth.
• Utility: Himalayan – irrigation canals, navigation (NW-1), large hydro potential but silt and seismic risk; Peninsular – reservoirs, delta irrigation, falls for power; seasonal limits.
• Conclusion: integrated basin management, interlinking with caution.