The drainage system refers to the flow of water through well-defined channels forming a network. Indian rivers exhibit diverse drainage patterns based on landform evolution, rock structure, and geological history.

India’s drainage system is shaped by physiography, slope, rock structure, and climatic conditions. Major patterns include dendritic, trellis, rectangular, radial, parallel, and centripetal. Drainage is classified based on orientation (Bay of Bengal vs Arabian Sea), origin (Himalayan vs Peninsular), and type (sea-draining vs inland). This system sustains agriculture, water supply, hydropower, and ecosystems.

The Himalayan Rivers originate from glaciers of the Hindu-Kush Himalaya, often called the 'Third Pole'. These rivers are perennial, fed by melting snow, rainfall, and groundwater, and are older than the Himalayas themselves, as shown by the deep antecedent gorges they cut through.

The Indus is one of the world's largest river basins, originating from the Kailash Range near Mansarovar Lake in Tibet. It flows through India (Ladakh), Pakistan, and finally discharges into the Arabian Sea near Karachi. It sustains millions of people across South Asia and is central to the Indus Valley Civilization and the Indus Water Treaty.

The Jhelum River originates from Verinag spring at the foothills of the Pir Panjal in Kashmir. It flows through Wular Lake and Srinagar, joins the Kishanganga, and flows into Pakistan where it merges with the Chenab at Trimmu. It is vital for Kashmir’s ecology, irrigation, and hydroelectric power, and has strategic significance under the Indus Water Treaty.

The Chenab River, formed by the confluence of the Chandra and Bhaga rivers near Bara Lacha Pass, is the largest tributary of the Indus. It flows through Himachal Pradesh, Jammu & Kashmir, and enters Pakistan, where it joins the Sutlej at Panjnad. The Ravi River, originating from the Kullu Hills near Rohtang Pass, flows through Himachal Pradesh and Punjab before merging with the Chenab in Pakistan. Both rivers are vital for irrigation, hydropower, and have strategic importance under the Indus Water Treaty.

The Beas River, originating near Rohtang Pass, flows entirely within India across Himachal Pradesh and Punjab before joining the Sutlej at Harike. It is the only Indus river system river confined entirely to India. The Sutlej, the longest of the five Punjab rivers, originates near Mansarovar-Rakas Lake in Tibet, enters India through Shipki La, and later joins the Chenab via Panjnad. Both rivers are vital for irrigation, hydropower, and are regulated under the Indus Water Treaty.

The Ganga is India’s lifeline river, originating from the Gangotri glacier (Bhagirathi) and Satopanth glacier (Alaknanda) before merging at Devprayag. Flowing 2,525 km through northern India and Bangladesh, it sustains agriculture, supports nearly 40% of India’s population, and is revered as sacred. Despite its immense socio-cultural, ecological, and economic significance, it faces critical challenges of pollution, overuse, and climate change.

After entering Bangladesh, the Ganga is renamed the Padma. It merges with the Jamuna (Brahmaputra distributary) and later with Meghna, before forming the Meghna estuary in the Bay of Bengal. This final course creates one of the most fertile and densely populated regions of the world, the Ganga–Brahmaputra–Meghna Delta.

The Ganga is India’s most important river system, originating from the Gangotri glacier (Bhagirathi) and flowing southeast for 2,525 km before discharging into the Bay of Bengal. It supports the largest alluvial plain of the world and is culturally revered as ‘Ganga Mata’.

The Yamuna is the westernmost and longest tributary of the Ganga. Originating from the Yamunotri glacier in the Banderpunch range, it flows for 1,376 km before joining the Ganga at Prayagraj. It is culturally revered and economically vital, supporting several major cities along its course.

The Chambal is a major right-bank tributary of the Yamuna, originating from the Janapao Hills in the Malwa Plateau. Known for its badland topography, the river flows through Madhya Pradesh and Rajasthan before joining the Yamuna in Uttar Pradesh. It is significant for irrigation, hydro-power, and unique ravine landscapes.

The Sind River is an important right-bank tributary of the Yamuna, originating from the Vidisha Plateau in Madhya Pradesh. Flowing for about 470 km, it plays a vital role in irrigation, agriculture, and regional water supply. The river also supports hydropower and local ecosystems through projects like the Manikheda Dam.

The Betwa and Ken rivers are significant right-bank tributaries of the Yamuna, flowing through Madhya Pradesh and Uttar Pradesh. Both rivers support irrigation, agriculture, and hydropower projects in the drought-prone Bundelkhand region, making them vital for water security and development.

The Son and Damodar rivers are important tributaries of the Ganga system, playing key roles in irrigation, hydropower, and flood control. While Son flows as a major right-bank tributary of Ganga, Damodar flows into the Hooghly and has been historically known as the 'Sorrow of Bengal' due to devastating floods.

The Ramganga and Ghaghara are important left-bank tributaries of the Ganga, contributing significantly to the river's flow in the northern plains. While Ramganga originates in the Garhwal hills, Ghaghara rises near Mansarovar and carries a large volume of water into the Ganga.

Saryu and Gandak are significant Himalayan tributaries contributing to the Ganga system. While Saryu joins the Ghaghara, Gandak directly flows into the Ganga. Both rivers are vital for irrigation, culture, and regional agriculture.

Burhi Gandak and Kosi are important tributaries of the Ganga system in Bihar. While Burhi Gandak is a relatively smaller river rising from the Sumesar hills, Kosi is a powerful trans-boundary river notorious for floods and channel shifts, earning the title 'Sorrow of Bihar'.

The Brahmaputra is one of the world’s largest rivers, originating in the Chemayungdung glacier of the Kailash Range. Known as Tsangpo in Tibet, Dihang in Arunachal Pradesh, and Jamuna in Bangladesh, it plays a vital role in the hydrology, culture, and economy of South Asia.

Majuli is the largest river island in the world, located on the Brahmaputra River in Assam. Known for its unique cultural heritage and environmental significance, Majuli is a vital hub of Assamese Neo-Vaishnavite culture founded by Srimanta Sankardev.

Peninsular India, forming an irregular triangular plateau, is drained by ancient rivers older than the Himalayan ones. These rivers display maturity with broad, shallow valleys, fixed courses, and distinct delta or estuary formations.

The present drainage system of Peninsular India was shaped by three major geological events: subsidence of the western peninsula, rise of the Himalayas with rift valley formation, and tilting of the peninsular block towards the southeast. These events directed most rivers eastward into the Bay of Bengal, with Narmada and Tapti as notable west-flowing exceptions.

The Mahanadi and Godavari are two significant east-flowing rivers of Peninsular India, draining into the Bay of Bengal. While the Mahanadi flows through Chhattisgarh and Odisha forming fertile deltas, the Godavari, also called Dakshin Ganga, is the largest peninsular river with an extensive drainage basin across multiple states.

The Krishna River, the second-largest east-flowing river of Peninsular India, rises from Mahabaleshwar in the Western Ghats and flows eastward into the Bay of Bengal. With an extensive basin across Maharashtra, Karnataka, and Andhra Pradesh, it supports major irrigation projects and forms a vital part of peninsular water resources.

The Cauvery River, rising from Tala Cauvery in the Brahmagiri hills of Karnataka, is a significant east-flowing peninsular river. Flowing through Karnataka and Tamil Nadu, it is vital for irrigation, hydro-power, and cultural heritage. It forms the famous Sivasamudram Falls and the riverine island of Srirangam before discharging into the Bay of Bengal.

Apart from the major east-flowing rivers like Mahanadi, Godavari, Krishna, and Cauvery, several smaller rivers such as Brahmani, Subarnarekha, Baitarani, Budhabalanga, Vamsadhara, and Penneru also drain into the Bay of Bengal, supporting regional agriculture and ecosystems.

Narmada and Tapti are the two major west-flowing rivers of Peninsular India. Both rivers traverse through rift valleys and drain into the Arabian Sea, forming estuaries. Narmada is the largest west-flowing river, while Tapti is considered its ‘twin’.

The Luni is the largest river system of Rajasthan. Originating near Pushkar, it flows as an ephemeral river through arid regions before ending in the Rann of Kutch. It is formed by the confluence of Saraswati and Sagarmati branches at Govindgarh.

The Sabarmati River, named after the Sabar and Hatmati streams, originates from the Mewar region in the Aravalli range and flows into the Gulf of Khambhat. It is an important river of western India, passing through major cities like Ahmedabad and Gandhinagar.

The Mahi River, originating from the Vindhyas, uniquely crosses the Tropic of Cancer twice before draining into the Gulf of Khambhat. Along with it, several short west-flowing rivers from the Western Ghats such as Kalinadi, Sharavati, Mandovi, Zuari, Bharathapuzha, and Pamba also drain into the Arabian Sea. These rivers, despite carrying significant water resources, do not form deltas due to steep slopes, short courses, and strong tidal action.

The Himalayan rivers and Peninsular rivers differ in origin, basin size, drainage type, flow nature, landforms, and maturity. While Himalayan rivers are perennial, large, and youthful forming big deltas, Peninsular rivers are mostly seasonal, smaller, mature, and form both deltas (east-flowing) and estuaries (west-flowing).

Several Indian rivers have been in recent news due to infrastructure projects, environmental concerns, cultural events, and river revival initiatives. Key rivers include Sabarmati, Narmada, Bedti-Varada, Pranhita, and Sukapaika.