Indian River System (Drainage Systems of India)

• The Indian river system is the network of channels that carries the country’s runoff to the Bay of Bengal, to the Arabian Sea or into closed inland basins. Most rivers end in the Bay of Bengal, while a smaller group crosses the western part of the country to the Arabian Sea.
• Inland drainage marks the northern parts of the Aravalli range, parts of Ladakh and the arid Thar.
• All major rivers start in one of three main source regions:
  • The Himalaya and the Karakoram range
  • The Chota Nagpur plateau and the Vindhya and Satpura ranges
  • The Western Ghats
• Rivers are a working resource as well as a landscape: irrigation, water supply, industry, hydroelectricity, inland navigation and fisheries all rest on them, and river deposition built almost all of the country’s fertile plains.

Classifying India’s Drainage

Key Terms

• Drainage: the flow of water through well-defined channels. The network of those channels is a drainage system.
• Catchment area: the area from which a river collects its water.
• River basin: the whole area drained by a main river and its tributaries. The Ganga basin, for example, includes the areas drained by the Yamuna, Ghaghara, Gandak and Kosi.
• Watershed: used in two senses.
  • As a line, the water divide separating one basin from the next.
  • As an area, a small catchment within a basin. Watersheds are small and basins large, and each works as a unit, so both serve as micro, meso and macro planning regions, which is the basis of watershed management.
• River regime: the seasonal rise and fall of the water volume in a river.

Classification by Size of the Catchment Area

• Kanuri Lakshmana Rao grouped Indian basins by catchment area in the 1970s, and the grouping is still the standard one:

• Major basins are the Indus, Ganga, Brahmaputra, Mahanadi, Godavari, Krishna, Cauvery, Narmada, Tapi, Penneru, Brahmani, Mahi, Sabarmati and Luni.
  • They lie in wet country. Three systems fall north of the Tropic of Cancer, seven between the Tropic and 20°N, and four in the Peninsula.
  • Some geographers also count the Subarnarekha, Surma and Luni here. The Subarnarekha was left out by older tables that gave it about 19,300 sq km. The 2019 national assessment gives it 26,804 sq km, which clears the limit.
• Medium basins split by direction of flow: 19 west-flowing, 21 east-flowing and 4 in other directions.
• Minor basins sit in dry areas or along the coast, above all on the west, where the narrow plain between the Ghats and the sea keeps rivers short.
• The Central Water Commission (CWC) now reports water resources by 20 basin units, some of them groupings of smaller rivers.

Classification by Origin

• The Himalayan rivers: perennial. The Indus, the Ganga, the Brahmaputra and their tributaries.
• The Peninsular rivers: mostly non-perennial. The Mahanadi, the Godavari, the Krishna, the Cauvery, the Narmada, the Tapi and their tributaries.
• The scheme has one known weakness: it puts the Chambal, Betwa and Son, far older in age and origin, in the same systems as Himalayan-born rivers. It remains the most widely used basis all the same.

Classification by Type of Drainage

• The river systems can also be set out in four groups:
  • Himalayan rivers, Deccan rivers and coastal rivers, which all reach the sea.
  • Rivers of the inland drainage basin (endorheic basin).
• Inland drainage takes in much of the Rajasthan desert and some of Aksai Chin in Ladakh.
  • Streams such as those feeding Sambhar in Rajasthan are mainly seasonal and end in basins and salt lakes.
  • The Ghaggar is the chief inland river. It is seasonal, rises on the lower Himalayan slopes, runs along the Haryana–Punjab boundary and dies in the Rajasthan sands near Hanumangarh after about 465 km.
    • Its old dry bed can still be traced and once fed the Indus. Its bed widens to about 10 km in the rains. Main feeders are the Tangri, Markanda, Saraswati and Chaitanya.
  • Most streams on the western slopes of the Aravalli vanish soon after they reach the dry sands.
  • The Luni is the only sizeable river crossing the Thar. It never reaches the open sea and is lost in the marshes above the Rann of Kachchh (Kutch).

Classification by Orientation to the Sea

• Bay of Bengal drainage: rivers draining to the Bay, broadly east-flowing.
• Arabian Sea drainage: rivers draining to the Arabian Sea, broadly west-flowing.

• The Narmada and the Tapi (Tapti) run almost parallel to each other and flow west, against the general eastward tilt of the Peninsula. Between them lie valleys of alluvial soil with much teak forest. The Narmada is held among India’s holiest rivers.
• Area and water do not match. Older accounts send over 90% of the water to the Bay of Bengal.
  • The 2019 CWC basin figures add up to a lower share: about 77% to the Bay, about 21% to the Arabian Sea side and about 2% through minor rivers towards Myanmar and Bangladesh.
  • The west coast streams explain the gap. They drain only about 3% of the country but carry about 12% of its water in the CWC figures, against the 18% often quoted earlier.

Contribution of Water by Various Rivers

• Estimates have moved over time, and the Brahmaputra and Ganga have always led. The 2019 CWC figures count 30 years of data (1985–2015) and a national total of 1,999.20 billion cubic metres (BCM), against 1,858,100 million cubic metres (about 1,858 BCM) in the older count.

• The older 40% for the Brahmaputra is no longer supported. Its share now sits level with the Ganga’s, though from under a quarter of the Ganga’s area.
• The Indus figure covers only the Indian part of its basin.

Himalayan and Peninsular Rivers

How the Two Systems Differ

• The contrast needs one qualification: the Cauvery is nearly perennial, since its upper basin takes south-west monsoon rain and its lower basin the north-east monsoon rain. This is why it is among the best regulated rivers in the country.

Character of the Peninsular Drainage

• These rivers are far older than the Himalayan ones, have almost reached their base level and show the look of a worn-down, senile surface.
  • Gentle gradients mean low velocity and low carrying power, so the east-flowing rivers build big deltas.
  • The exceptions are steep tracts along faults, and superimposed or rejuvenated stretches marked by waterfalls: the Jog on the Sharavati (253 m, or 289 m in older accounts), Sivasamudram on the Cauvery (101 m), and Dhuandhar on the Narmada (15 m).
• Three directions of flow stand out:
  • South-east to the Bay: Mahanadi, Godavari, Krishna, Cauvery and smaller rivers.
  • West to the Arabian Sea: Narmada, Tapi and the Western Ghats streams.
  • North-east, into the Ganga and Yamuna: Chambal, Betwa, Ken, Son, Damodar.
• Evolution of the east-flowing rivers and their western counterparts:
  • The Sahyadri–Aravalli axis is taken as the old main divide. In one hypothesis, the Western Ghats once stood mid-way across a wider landmass, with drainage on either side, until the western half foundered in the early Tertiary.
  • Sagging of the northern Peninsula during the Himalayan collision opened the troughs the Narmada and the Tapi now occupy, so they did not carve their own valleys.
  • Darashaw Nosherwan Wadia (1975) added a slight eastward tilt of the block south of those cracks, which turned the drainage towards the Bay.
  • R. C. Mehdiratta (1962) objected that such tilting should have rejuvenated the rivers much more widely than the few waterfalls show.

River Regimes

• Himalayan regimes are both glacial and monsoonal, while most Peninsular regimes are monsoonal only.
• Differences among Peninsular rivers follow the season of rain in their basins.
• The hydrographs at four classical stations read as follows:

• Discharge is measured in cumecs (cubic metres per second) or cusecs (cubic feet per second).
• Implications for irrigation and power:
  • Himalayan rivers keep flow through the critical winter months, so canals work without big storage, though narrow valleys, seismicity and flat plains limit large reservoirs.
  • Peninsular rivers need monsoon water stored before dependable power or irrigation can be had.

Use of the Rivers

• Irrigation is the largest use. Older estimates put canal use at about 555,166 million cubic metres, about 30% of annual flow, out of a yearly precipitation of about 37,00,400 million m³.
• Hydroelectricity: in older estimates, 60% of river flow lies in Himalayan rivers, 16% in central Indian rivers and the rest in the Deccan, with an exploitable potential then assessed at about 41 million kW at 60% load factor.
• Navigation: the Ganga, Brahmaputra and Mahanadi are the chief navigable rivers. The Godavari, Krishna, Narmada and Tapi are useful only near their mouths. River transport declined with railways and roads, and with water withdrawals.

Drainage Patterns

• A drainage pattern is the geometric design formed by a river and its tributaries. It is set by slope, rock resistance, structure, climate and the geological history of the area.
• The patterns fall into two groups: those explained by the history of the river against the land, and those read from the shape of the network.

Patterns by the River’s History

Patterns by the Shape of the Network

• Dendritic: tree-like branching on uniform rock with little faulting. The term goes back to Israel Cook Russell (1898). Most rivers of the northern plain follow it.
• Trellis: main tributaries run parallel and secondary streams join them at right angles, on alternating hard and soft bands.
• Rectangular: right-angled bends and junctions set by joints and faults, less regular than trellis. Parts of the Vindhyan country show it.
• Radial: rivers run outwards from a central high.
  • The Amarkantak highland is the classic case, sending the Narmada and the Son in different directions. The Mahanadi, often added to this list, rises separately near Sihawa in Chhattisgarh.
  • Other examples are the Girnar hills and the Mikir hills.
• Centripetal: streams drain inwards to a lake or depression, as at Sambhar.
• Parallel: rivers run side by side down a steady slope, as on the western face of the Western Ghats.
• Annular: streams curve around a dome before joining the main river. It is rare in India.
• Barbed: tributaries still point the way the main river once flowed, as on the Arun, a Kosi tributary.
• Deranged: an unorganised net of streams and lakes on land recently left by ice, reported from glaciated Karakoram valleys.

Water Divides and Drainage Pattern

• The main Indian water divide runs about 2,736 km from Kanniyakumari along the Western Ghats, through the Ajanta, Maikala and Vindhya ranges and the Aravalli, to the Shiwalik hills near Haridwar.
  • It stands close to the west coast in the Peninsula. This single fact produces short, swift west-flowing streams and long east-flowing rivers.
  • Further north, the Delhi ridge separates the Indus and Ganga systems.
• A divide controls drainage in three ways: it decides the direction of flow, it fixes the size of basins on each side, and it sets the gradient the rivers work on.

Evolution of the Himalayan Drainage

Antecedent Origin

• Many Himalayan rivers predate the ranges they cross. They rise on the Tibetan side and cut across the whole mountain belt.
  • The gorges of the Indus, Satluj, Alaknanda, Gandak, Kosi and Brahmaputra are the main evidence.
  • These rivers held their courses as the land rose, deepening their beds while the banks climbed.
• Three features need explaining: long strike-parallel courses of the Indus, Satluj and Brahmaputra, deep transverse gorges, and upper tributaries that still flow west.

The Indo-Brahm or Shiwalik River Hypothesis

• Edwin Hall Pascoe (1919) and Guy Ellcock Pilgrim (1919) reached the same idea independently. Pascoe called the river the Indo-Brahm. Pilgrim called it the Shiwalik River, since its line matches the present Shiwalik hills.
• The river: after the Eocene gulf from Sind to the Nainital area withdrew, one master stream ran from Assam along the Himalayan foot to Punjab and on through Sind to the Arabian Sea. The Shiwalik deposits are read as its load.
• The break-up took place through Pleistocene upheaval in the western Himalaya, including the Potwar plateau, and headward erosion by its tributaries. It left:
  • The Indus and its five Punjab tributaries.
  • The Ganga and its Himalayan tributaries.
  • The Assam stretch of the Brahmaputra with its tributaries.
• Sinking of the Malda gap between the Rajmahal hills and the Meghalaya plateau then turned the Ganga and Brahmaputra towards the Bay of Bengal.
• The Yamuna is thought to have first belonged to the Indus side, perhaps through the Ghaggar or as a separate river to the Rann of Kachchh. Disturbance along the Aravalli axis later passed it to the Ganga.
• The Tibetan River: Pascoe also proposed a stream along the Tsangpo–Manasarovar–Satluj–Gartang–Indus trough, draining perhaps to an Oxus lake or through gaps such as the Photu Pass. Headward cutting by the Irrawaddy–Chindwin, Meghna–Brahmaputra, Satluj and Indus would have dismembered it.
  • Hellmut de Terra suggested that Karakoram and Ladakh rivers once ran south-east or east and were captured by the Dihang.
• Objections:
  • The Shiwalik beds do not need one river. Streams coming down from the Himalaya could have built them as a chain of fans.
  • M. S. Krishnan and N. K. N. Aiyengar (1940) rejected the river on geological and physiographic grounds.
  • The depositional history of the Ganga delta and Assam does not fit it.
  • The Tipam sandstones of Assam were laid in an estuary too close to the supposed headwaters.
  • The upper Satluj looks undersized in its canyon in the Nari Khorsum beds. Pascoe’s capture-and-loss account of it has found little support.

The Three Upheavals Account

• Enayat Ahmad (1965, 1971) tied drainage to the Himalayan uplift phases:

The Multiple River Hypothesis

• This view drops the single great river.
  • An Eocene sea reached Sind, Rajasthan and Punjab, then Jammu, Lansdowne and Nainital, as shallow-water beds at Lansdowne show. A ridge from the Aravalli marked its limit. A second ridge linked the Rajmahal hills and the Meghalaya plateau.
  • The first upheaval isolated this sea as a basin. The second formed a foredeep with many lagoons, filled by streams from both the Peninsula and the Himalaya. Their load is the Shiwalik sequence.
  • The foredeep opened east through the Rajmahal–Garo gap and west to the Arabian Sea. When the lagoons dried, separate transverse rivers became today’s drainage.

Current View

• The debate has moved to dating sediment grains by source. Two studies of the eastern Himalaya show the kind of evidence now used:
  • Karl Lang and Katharine Huntington (2014) found Tibetan zircons in Lower Siwalik rocks near the Siang, and read the Yarlung–Siang–Brahmaputra link as antecedent, in place by the Early Miocene.
  • Laura Bracciali and co-workers (2015) read similar evidence as an Early Miocene river capture.
• Both date the link well before the Pleistocene, so neither supports the classical late timing. The Indo-Brahm remains a historical hypothesis, not an established fact.

Shifting Courses and River Capture

• Capture happens when a stream eroding headward takes the upper waters of another river. Shifting is common on the plains, where rivers meander and straighten during floods.
• Reported cases, many of them inferred, include:
  • Saraswati–Ghaggar: its upper waters were lost, leaving the dry valley traced in Rajasthan.
  • Punjab rivers: the lower Indus ran well to the east in historical times; the Beas and Satluj have also changed their junctions.
  • Tista: turned east to the Brahmaputra after the floods of 1787.
  • Brahmaputra: moved from the old Mymensingh channel to the Jamuna course in the 18th and 19th centuries.
  • Tsangpo: classically taken to have drained to the Irrawaddy until captured.
  • Kosi: shifted west by more than 110 km over about two centuries, then jumped about 120 km east in August 2008.
• Causes include gentle slope, meandering, flood straightening, uplift of the Potwar plateau and Barind tract, and sinking of the Malda gap.

Major River Systems at a Glance

• Himalayan river systems: Indus, Brahmaputra, Ganga.
• Peninsular river systems: Godavari, Krishna, Cauvery, Mahanadi.
• West-flowing Peninsular river systems: Narmada, Tapi, Sabarmati and Mahi, and the Luni.

Indus River System

• It rises on the northern slopes of the Kailas (Kailash) range in Tibet, near Lake Manasarovar.
• It has many tributaries in India and Pakistan and runs about 2,880–2,897 km to the sea near Karachi, of which about 700 km is given as the Indian stretch in older accounts and 1,114 km in official texts that count the whole of Ladakh and Jammu and Kashmir.
• It enters Indian territory in Ladakh through a picturesque gorge and flows between the Ladakh and Zaskar ranges past Leh.
• In this region it takes the Zaskar, Shyok, Nubra and Hunza. The Nubra reaches it through the Shyok, and the Hunza through the Gilgit.
• It crosses the Himalaya in a gorge about 5,181 m deep near Bunji, north of Nanga Parbat, well upstream of Attock.
• The major tributaries in India are the Jhelum, Chenab, Ravi, Beas and Satluj (Sutlej).

Brahmaputra River System

• It rises in the Chemayungdung glacier area in south-west Tibet, close to Lake Manasarovar (Mansarovar). The Indus and Satluj start nearby. The lake is not itself the source.
• Length is usually given as 2,900 km. A 2011 Chinese Academy of Sciences study traced it from the Angsi glacier and got 3,848 km, slightly longer than its 3,600 km for the Indus.
• Most of its course lies outside India.
• As the Tsangpo it runs east along the Himalaya, makes a U-turn around Namcha Barwa, and enters Arunachal Pradesh as the Dihang.
• It flows through Arunachal Pradesh and Assam, gathering many tributaries, with a braided channel through most of Assam.
• In Tibet it carries less water and silt. In India it crosses very wet country, so it carries huge volumes and silt in the rains. It is among the country’s largest rivers by volume and causes severe floods in Assam and Bangladesh.

Ganga River System

• It starts as the Bhagirathi from the Gangotri glacier.
• Above Devprayag in Garhwal, the Mandakini, Pindar, Dhauliganga and Bishenganga join the Alaknanda, and the Bheling joins the Bhagirathi.
• The Pindar rises from the East Trisul (Trishul) and Nanda Devi area and joins at Karnaprayag. The Mandakini meets at Rudraprayag.
• From Devprayag, the united stream is called the Ganga.
• The Panch Prayag, where the Alaknanda meets:
  • Vishnuprayag: the Dhauli Ganga
  • Nandprayag: the Nandakini
  • Karnaprayag: the Pindar (Pinder)
  • Rudraprayag: the Mandakini
  • Devprayag: the Bhagirathi, forming the Ganga
• Principal tributaries are the Yamuna, Damodar, Sapta Kosi, Ramganga, Gomati, Ghaghara and Son. The river reaches the Bay of Bengal after 2,525 km.

Yamuna River System

• The Yamuna is the largest tributary of the Ganga in the northern plains.
• It rises at the Yamunotri glacier on Bandarpunch (Bandarpoonch) in Uttarakhand.
• Tributaries include the Sind, Hindon, Betwa, Ken and Chambal.
• The Tons is its largest Himalayan tributary. The Chambal is the longest overall.
• Its catchment reaches Delhi, Himachal Pradesh, Uttar Pradesh, Haryana, Rajasthan and Madhya Pradesh, as well as Uttarakhand.

Narmada River System

• A central Indian river rising at Amarkantak Hill in Madhya Pradesh.
• It traces the traditional frontier between North and South India.
• It is a major Peninsular river running east to west. Besides the Narmada, the Tapi does the same across the country, and the Mahi, Sabarmati and Luni also end on the west.
• It flows through Madhya Pradesh, Maharashtra and Gujarat and enters the Arabian Sea in Bharuch district, Gujarat.

Tapi River System

• A central Indian river and one of the main Peninsular rivers running east to west.
• It rises in the eastern Satpura in southern Madhya Pradesh.
• It flows west through the Nimar region of Madhya Pradesh, east Vidarbha and Khandesh in Maharashtra, in the north-west corner of the Deccan plateau, and south Gujarat, to the Gulf of Khambhat (Cambay).
• Its basin lies mostly in the eastern and northern districts of Maharashtra, with some districts of Madhya Pradesh and Gujarat.
• Main tributaries are the Waghur, Aner, Girna, Purna, Panzara and Bori.

Godavari River System

• The second-longest river course in India, after the Ganga, and known for its brownish water.
• It is also called Dakshin (South) Ganga or Vriddh (Old) Ganga.
• It is seasonal, low in summer and wide in the monsoon.
• It rises at Trimbakeshwar near Nashik (Nasik) in Maharashtra.
• It flows east for 1,465 km to the Bay of Bengal. Basin shares are given as Maharashtra 48.6%, Telangana 18.8%, Andhra Pradesh 4.5%, Chhattisgarh 10.9% and Odisha 5.7%, with Madhya Pradesh and a little of Karnataka making up most of the rest.
• It builds a fertile delta below Rajahmundry.
• Pilgrim centres include Nashik and Trimbak in Maharashtra and Bhadrachalam in Telangana.
• Tributaries include the Pranhita (Pranahita; Penganga, or Penuganga, and Wardha), Indravati, Bindusara, Sabari and Manjira.
• The Kovvur–Rajahmundry rail-cum-road bridge crosses it. It was long called Asia’s largest, a title now overtaken in India by Bogibeel (4.94 km, 2018) on the Brahmaputra.

Krishna River System

• One of India’s longest rivers, it rises at Mahabaleshwar in Maharashtra.
• It passes Sangli and ends in the Bay of Bengal.
• It flows through Maharashtra, Karnataka, Telangana and Andhra Pradesh.
• The Tungabhadra is the main tributary, formed by the Tunga and Bhadra from the Western Ghats.
• Others are the Dudhganga, Koyna, Bhima, Malaprabha (Mallaprabha), Dindi, Ghataprabha, Warna, Yerla and Musi.

Cauvery River System

• Known as the Ganga (Ganges) of the South (“Dakshin Bharat ki Ganga”).
• It rises at Talakaveri, a pilgrim and tourist site in the Western Ghats, in Kodagu district of Karnataka.
• It flows from Karnataka through Tamil Nadu to the Bay of Bengal, and has supported irrigation, old kingdoms and modern cities of the south.
• Tributaries are the Arkavathy, Shimsha, Hemavati, Kapila (Kabini), Honnuhole, Amaravati, Lakshmana Tirtha, Lokapavani, Bhavani and Noyyal.

Mahanadi River System

• An eastern Indian river rising near Sihawa in the Dhamtari area of Chhattisgarh, in the northern foothills of Dandakaranya. It is not a Satpura river, as sometimes stated.
• It flows east to the Bay of Bengal. Its basin is mainly in Chhattisgarh and Odisha (Orissa), with small parts in Jharkhand and Maharashtra.
• The Hirakud Dam stands on it.