Himalayan and Peninsular Rivers

The present drainage system of India is a result of a long evolutionary process spanning different geological eras. It is broadly divided into the Himalayan Drainage System and the Peninsular Drainage System, separated by the Indo-Gangetic alluvium.

Evolution of Himalayan Drainage

The geological evolution of Himalayan rivers is linked to the collision of the Indian plate with the Eurasian plate during the Tertiary period.

• The Indo-Brahma River Hypothesis: Geologists suggest that during the Miocene period, a mighty river called the Indo-Brahma or the Shiwalik river flowed longitudinally along the entire longitudinal extent of the Himalayas from Assam to Punjab, eventually discharging into the Gulf of Sindh.
• Disruption of the Indo-Brahma River: This mega-river was later dismembered into three distinct systems due to two major geological events: the Pleistocene upheaval of the Western Himalayas (including the Potwar Plateau/Delhi Ridge), which acted as a water divide between the Indus and Ganga systems, and the down-faulting of the Malda Gap (between the Rajmahal Hills and Meghalaya Plateau), which diverted the Ganga and Brahmaputra towards the Bay of Bengal.

Evolution of Peninsular Drainage

The Peninsular drainage system is much older than the Himalayan system and has evolved through three major geological events:

• Subsidence of the Western Flank: During the early Tertiary period, the western margin of the Peninsular block subsided below the sea, disrupting the symmetrical plan of the rivers on either side of the original western ghats watershed.
• Upheaval of the Himalayas: The violent folding of the Himalayas subjected the northern flank of the Peninsular block to subsidence, resulting in trough faulting. The Narmada and Tapi rivers flow through these structural rift valleys (fault troughs).
• Slight Tilting of the Peninsular Block: The entire Peninsular block tilted slightly from the north-west to the south-east, causing the orientation of the major drainage systems towards the Bay of Bengal.

Structural and Geomorphic Differences

Himalayan Rivers

• Nature of Flow: Perennial in nature, fed by both glacial meltwater during summer and rainfall during the monsoon season.
• Geomorphic Stage: Youthful stage; these rivers actively perform lateral and vertical erosion, creating deep V-shaped valleys, gorges, rapids, and waterfalls in their upper courses. Upon entering the plains, they form depositional features like ox-bow lakes, broad floodplains, braided channels, and massive deltas.
• Catchment Area: Possess very large basins and expansive catchment areas (e.g., the Ganga basin covers roughly 26% of India’s landmass).
• Flexibility of Course: Highly prone to meandering and shifting courses due to the loose, unconsolidated nature of the alluvial soils in the plains.

Peninsular Rivers

• Nature of Flow: Non-perennial or seasonal; completely dependent on monsoon rainfall. Rivers shrink significantly or dry up during the summer months.
• Geomorphic Stage: Mature, graded stage; these rivers have reached their base level of erosion. Their valleys are broad, shallow, and largely devoid of youth-stage features like deep gorges.
• Catchment Area: Relatively smaller, fixed basins bound by hard cratonic hard-rock topography.
• Flexibility of Course: Characterized by fixed, stable, and straight courses because they flow through hard, unyielding crystalline bedrock that prevents meandering.

Comprehensive Major River Systems

The Himalayan River Systems

• The Indus System: Originates from the Bokhar Chu glacier near Lake Mansarovar in Tibet (where it is called Singi Khamban). It enters India in Ladakh and flows through the Zanskar and Ladakh ranges. Its major Himalayan tributaries are the Shyok, Gilgit, Zanskar, and Hunza. It enters Pakistan after cutting a deep gorge through the Nanga Parbat massif. The five main left-bank Panjnad tributaries are:
  • Jhelum: Originates at Verinag; flows through Wular Lake; forms a meandering path in the Kashmir valley.
  • Chenab: Formed by the confluence of the Chandra and Bhaga rivers at Tandi near Keylong (Himachal Pradesh); it is the largest tributary of the Indus by volume.
  • Ravi: Originates near the Rohtang Pass in the Kullu hills; flows between the Pir Panjal and Dhauladhar ranges.
  • Beas: Originates from the Beas Kund near Rohtang Pass; lies entirely within Indian territory.
  • Satluj: Originates from the Rakas Tal in Tibet (where it is called Langchen Khambab); enters India through the Shipki La pass.
• The Ganga System: Formed by the confluence of the Alaknanda (originating from Satopanth glacier) and Bhagirathi (originating from Gangotri glacier at Gaumukh) at Devprayag.
  • Right-bank Tributaries: Yamuna (longest tributary, originates at Yamunotri, joins at Prayagraj), Son (originates at Amarkantak), and Punpun.
  • Left-bank Tributaries: Ramganga, Gomti (perennial plain-origin river), Ghaghara, Gandak, Kosi (known as the “Sorrow of Bihar” due to frequent course shifts), and Mahananda.
• The Brahmaputra System: Originates from the Chemayungdung glacier near Lake Mansarovar in Tibet, where it flows parallel to the Himalayas as the Yarlung Tsangpo. It enters India via a deep gorge at Namcha Barwa in Arunachal Pradesh, where it is called the Siang or Dihang. It is joined by the Dibang and Lohit to form the Brahmaputra in the Assam Valley.
  • Key Tributaries: Subansiri, Kameng, Manas, Sankosh, and Teesta (Right Bank); Burhi Dihing, Dhansiri, and Kopili (Left Bank). It forms Majuli, one of the world’s largest inhabited riverine islands.

The Peninsular River Systems

• East-Flowing Peninsular Rivers (Bay of Bengal Drainage):
  • Mahanadi: Originates from the Sihawa highlands in Dhamtari district of Chhattisgarh; flows through Odisha. Major tributaries include Seonath, Hasdeo, Mand, Ib, Jonk, and Tel.
  • Godavari (Dakshin Ganga): The largest Peninsular river system. Originates at Trimbakeshwar near Nashik in Maharashtra. Its vast basin is shared by Maharashtra, Telangana, Andhra Pradesh, Chhattisgarh, and Odisha. Major tributaries include Pravara, Purna, Manjra, Penganga, Wardha, Wainganga, Indravati, and Sabari.
  • Krishna: Second-largest east-flowing peninsular river. Originates near Mahabaleshwar in Maharashtra. Major tributaries include Koyna, Ghataprabha, Malaprabha, Bhima, Tungabhadra, and Musi.
  • Cauvery (Kaveri): Originates at Talakaveri in the Brahmagiri hills of Karnataka. It is a unique peninsular river because its upper catchment receives rainfall from the South-West Monsoon and its lower catchment receives rainfall from the North-East Monsoon, making it semi-perennial. Major tributaries include Harangi, Hemavati, Shimsha, Arkavati, Lakshmantirtha, Kabini, Bhavani, and Amravati.
• West-Flowing Peninsular Rivers (Arabian Sea Drainage):
  • Narmada: Originates from the western flank of the Amarkantak Plateau. It flows through a structural rift valley between the Vindhyan range (north) and Satpura range (south). It forms the Dhuandhar Falls near Jabalpur and creates a broad estuary at its mouth instead of a delta.
  • Tapi (Tapti): Originates in the Multai reserved forest in the Betul district of Madhya Pradesh. It flows parallel to the Narmada in a rift valley south of the Satpura range.
  • Luni: The largest river system of the Thar desert in Rajasthan. Originates near Pushkar in two branches (Saraswati and Sabarmati) and terminates in the marshy grounds of the Rann of Kutch (Inland drainage).

Comparative Parameter Summary

Strategic Hydrological Concepts for Prelims

• Water Divides of India: The main water divide in India is formed by the block mountain line extending through the Western Ghats, Aravali Range, and the Delhi Ridge. A secondary divide separates the Ganga basin from the Indus basin in the north and the Mahanadi/Godavari basins from the Narmada/Tapi basins in Central India.
• The Antecedent Nature of Himalayan Gorges: The Indus Gorge (Gilgit), the Shipki La Gorge (Satluj), and the Dihang Gorge (Brahmaputra) prove that these rivers are older than the mountain ranges themselves. They maintained their paths by matching the rate of vertical downcutting with the rate of tectonic uplift of the mountains.
• Why West-Flowing Rivers Do Not Form Deltas: Rivers like the Narmada and Tapi flow through hard rock rift valleys, which means they carry a negligible amount of alluvial sediment load. Furthermore, the steep gradient of the Western Ghats gives these rivers a very high velocity when meeting the Arabian Sea, washing away any accumulated material into the deep oceanic drop-off.
• River Regimes: The structural pattern of the seasonal flow of water in a river channel is its regime. Himalayan rivers show a dual-peak regime (one in spring due to snowmelt, one in August due to monsoons), whereas Peninsular rivers show a single-peak regime strictly matching the monsoon hydrograph.