Surface Water Resources of India

India accounts for roughly 2.45% of the world’s land area, 4% of the world’s water resources, and nearly 18% of the global population. The total water potential of India is estimated at 1,869 cubic kilometers (km³) per year, but due to topographical, hydrological, and socio-ecological constraints, only about 1,123 km³ (690 km³ from surface water and 433 km³ from groundwater) is utilizable. Surface water resources are distributed across rivers, lakes, ponds, tanks, and wetlands, heavily dependent on the Southwest and Northeast monsoons.

Major River Basins and Surface Water Potential

The Central Water Commission (CWC) divides India into 20 river basins. These are broadly categorized into Himalayan Rivers, Peninsular Rivers, and West-flowing Ephemeral Rivers.

Himalayan River Systems

The Indus, Ganga, and Brahmaputra systems carry about 60% of the total surface water potential of the country.

• The Brahmaputra Basin: Possesses the highest average annual runoff among all Indian rivers, accounting for nearly 31% of India’s total surface water potential, despite having a relatively smaller catchment area within Indian territory.
• The Ganga Basin: Features the largest catchment area in India, covering approximately 26% of the country’s landmass and supporting the highest population density.
• The Indus Basin: Crucial for the northwestern states; its water availability within India is governed strictly by the provisions of the Indus Waters Treaty (1960).

Peninsular River Systems

Peninsular rivers are non-perennial, rain-fed systems with high seasonal fluctuations in discharge.

• East-flowing Rivers: Godavari, Krishna, Mahanadi, and Cauvery drain into the Bay of Bengal. The Godavari is the largest peninsular river basin, often referred to as the Dakshin Ganga.
• West-flowing Rivers: Narmada and Tapi drain into the Arabian Sea through estuaries rather than deltas. Numerous swift, short west-flowing streams originating in the Western Ghats carry significant water volume during the monsoon but lack storage capacity.

Catchment Area and Average Annual Yield by Basin

The following data highlights the disparity between catchment area and actual water availability across major Indian river basins:

Lakes and Wetlands as Surface Water Reservoirs

Lakes and wetlands serve as vital natural sponges, regulating microclimates, recharging local aquifers, and acting as surface water storage units during peak monsoonal floods.

Classification and Distribution of Lakes

• Freshwater Lakes: Primarily concentrated in the Himalayan region (e.g., Wular Lake and Dal Lake in Jammu & Kashmir, Loktak Lake in Manipur). Wular Lake is one of the largest freshwater lakes in Asia, formed due to tectonic activity and fed by the Jhelum River. Loktak Lake is famous for its floating islands called phumdis and hosts the Keibul Lamjao National Park.
• Brackish/Saline Lakes: Predominantly found in arid regions and coastal plains. Chilika Lake (Odisha) is India’s largest coastal lagoon and the second-largest coastal lagoon in the world. Pulicat Lake (Andhra Pradesh/Tamil Nadu border) and Sambhar Lake (Rajasthan)—India’s largest inland salt lake—are critical surface water features.
• Oxbow Lakes: Formed by meandering rivers in the Indo-Gangetic plains. Kanwar Lake (Kabartal) in Bihar is Asia’s largest freshwater oxbow lake, formed by the meandering of the Gandak River.

Wetlands and the Ramsar Convention

Wetlands cover approximately 4.63% of India’s geographical area. As of recent hydrological records, India has designated over 80 sites as Wetlands of International Importance under the Ramsar Convention.

• The Montreux Record: A register of wetland sites on the List of Wetlands of International Importance where changes in ecological character have occurred, are occurring, or are likely to occur. Currently, two Indian sites are on the Montreux Record: Keoladeo National Park (Rajasthan) and Loktak Lake (Manipur). Chilika Lake was placed on the record but later removed due to successful rehabilitation efforts.
• Coastal Wetlands: Mangroves, coral reefs, and estuaries (e.g., Sundarbans in West Bengal, Bhitarkanika in Odisha) serve as barrier systems protecting inland surface water from salinity intrusion.

Irrigation and Surface Water Utilization

Agriculture consumes approximately 89% of the total recorded surface water drawdowns in India, followed by domestic use (7%) and industrial requirements (4%).

Modes of Surface Irrigation

• Canal Irrigation: Represents the second largest source of irrigation in India after groundwater. It is highly developed in the northern plains due to the perennial nature of the rivers and the soft, alluvial soil structure. Major projects include the Indira Gandhi Canal Project (Rajasthan), which draws water from the Harike Barrage at the confluence of the Satluj and Beas rivers.
• Tank Irrigation: Predominantly practiced in the Peninsular plateau region (including Andhra Pradesh, Tamil Nadu, and Karnataka). The hard, undulating rocky terrain makes canal excavation difficult, and the non-perennial nature of rivers necessitates localized storage in depressions.

Major Multipurpose River Valley Projects

These projects manage surface water for irrigation, flood control, and hydroelectric power generation:

• Bhakra-Nangal Project: Built across the Satluj River; its reservoir, Gobind Sagar, supplies irrigation to Punjab, Haryana, and Rajasthan.
• Damodor Valley Corporation (DVC): Modeled on the Tennessee Valley Authority (USA), it controls floods and provides irrigation in Jharkhand and West Bengal across the Damodar River and its tributaries (Barakar, Konar).
• Hirakud Dam: Constructed across the Mahanadi River in Odisha, it is one of the longest earthen dams in the world, addressing the historic flood issues of the coastal delta.
• Nagarjuna Sagar Project: Built across the Krishna River in Andhra Pradesh and Telangana, supporting extensive canal networks in the eastern Deccan.

Institutional Framework and Inter-State Water Disputes

Surface water management in India faces legal and administrative complexities due to its transboundary nature across state lines.

Constitutional Provisions

• Seventh Schedule Entry 17 (State List): Governs water supplies, irrigation, canals, drainage, embankments, water storage, and water power within a state’s boundary.
• Seventh Schedule Entry 56 (Union List): Empowers the Central Government to regulate and develop inter-state rivers and river valleys to the extent declared by Parliament.
• Article 262: Provides that Parliament may by law provide for the adjudication of any dispute or complaint with respect to the use, distribution, or control of the waters of any inter-state river or river valley, explicitly barring the Supreme Court from initial jurisdiction in these specific disputes.

Prominent Inter-State Water Disputes

• Cauvery Water Dispute: Involves Karnataka, Tamil Nadu, Kerala, and Puducherry.
• Krishna Water Dispute: Involves Maharashtra, Karnataka, Andhra Pradesh, and Telangana.
• Mahadayi/Mandovi Dispute: Involves Goa, Karnataka, and Maharashtra.
• Sutlej-Yamuna Link (SYL) Canal Dispute: Involves Punjab and Haryana concerning the sharing of Ravi-Beas waters.

Key Facts and Hydrological Trivia for Prelims

• National Waterway 1 (NW-1): Runs from Prayagraj to Haldia across the Ganga-Bhagirathi-Hooghly river system, covering 1,620 km.
• The National River Linking Project (NRLP): Managed by the National Water Development Agency (NWDA), it aims to transfer water from surplus basins (like the Brahmaputra and Ganga) to deficit basins via two components: the Himalayan Component and the Peninsular Component. The Ken-Betwa link project is the first operational project under this initiative.
• Composite Water Management Index (CWMI): Released periodically by NITI Aayog to assess and improve performance in efficient management of water resources across states.
• National Water Mission: One of the eight missions under the National Action Plan on Climate Change (NAPCC), targeting an increase in water use efficiency by 20%.