Water resources

1. Availability, distribution and water accounting

Water resources comprise surface water, groundwater and water stored as snow and ice. Rivers, lakes, wetlands and reservoirs provide surface supplies, while aquifers store groundwater. These sources are connected: infiltration recharges aquifers, and groundwater discharge sustains many rivers during the dry season. Consequently, groundwater pumping can reduce river baseflow even without direct abstraction from a river.

India receives approximately 4,000 billion cubic metres of annual precipitation, including snowfall, but this is not equivalent to usable freshwater. Evapotranspiration, rapid runoff, terrain, geological conditions and the timing of rainfall limit availability. The Central Water Commission’s 2019 reassessment estimated average annual water resources at about 1,999 BCM. This basin-scale estimate and the conventional utilisable-resource estimate of 1,123 BCM measure different things and should not be confused.

Rainfall is highly uneven. The western slopes of the Western Ghats and much of northeastern India receive abundant rainfall, whereas western Rajasthan and the rain-shadow interiors of the Deccan receive much less. Concentration of rain into a few months means that floods and seasonal scarcity can occur in the same region. Tamil Nadu also receives substantial rainfall during the October–December northeast monsoon.

Water stress reflects pressure on available water relative to demand. Under the commonly used Falkenmark indicator, annual availability below 1,700 cubic metres per person indicates stress, below 1,000 indicates scarcity, and below 500 indicates absolute scarcity. National averages conceal basin-level shortages, unreliable access and pollution. Physical availability therefore differs from the amount that people can safely and affordably obtain.

• BCM means billion cubic metres; one BCM equals one cubic kilometre.
• Renewable water is replenished through the hydrological cycle; it does not imply unlimited or uniformly available supply.
• Water withdrawal is abstraction from a source; consumptive use is the portion not promptly returned for reuse, especially through evapotranspiration.

2. Surface water, groundwater and water quality

Himalayan rivers generally receive both precipitation and snow or glacier melt, although the contribution varies greatly between basins. Peninsular rivers depend more strongly on seasonal rainfall and commonly exhibit larger seasonal flow variations. Reservoirs redistribute runoff across seasons and support irrigation, electricity generation and urban supply. Their effective capacity can decline through sedimentation, while evaporation causes additional losses.

The Indo-Gangetic-Brahmaputra alluvial plains contain extensive aquifers with considerable groundwater-storage potential. In much of peninsular India, crystalline hard rocks store groundwater mainly in weathered layers and fractures. Such aquifers often have limited and spatially variable storage. A borewell’s depth alone therefore does not guarantee a sustainable yield. Coastal aquifers face seawater intrusion when excessive pumping lowers freshwater pressure.

Groundwater over-extraction is particularly serious in parts of Punjab, Haryana, Rajasthan and other intensively cultivated or urbanised areas. The stage of groundwater extraction expresses annual extraction as a percentage of annual extractable groundwater resources. An assessment unit with extraction exceeding 100 per cent is classified as over-exploited. Nationally comfortable averages can coexist with severe local depletion.

Quality problems further reduce usable supplies. Arsenic contamination occurs in parts of the Ganga-Brahmaputra alluvial region; excessive fluoride occurs in several hard-rock terrains. Salinity affects coastal and arid areas, while nitrate contamination commonly reflects fertiliser use, sewage or other human inputs. Pathogens, untreated wastewater and industrial effluents also threaten water security. Geogenic contamination requires suitable treatment or alternative sources, not merely deeper drilling.

• An unconfined aquifer has a water table as its upper boundary; a confined aquifer lies beneath a relatively impermeable layer.
• Recharge structures must suit local geology and receive sufficiently clean water.
• Wetlands help moderate floods, retain pollutants and support biodiversity, but cannot absorb unlimited waste.

3. Agriculture, irrigation and competing demands

Irrigation reduces dependence on uncertain rainfall and enables multiple cropping, but its sustainability depends on crop choice, delivery systems and drainage. Canals serve extensive command areas but may suffer from conveyance losses and unequal distribution between head-end and tail-end farmers. Wells provide flexible, farmer-controlled irrigation, while tanks remain important in several peninsular landscapes.

Water-intensive paddy and sugarcane cultivation in water-stressed locations can create a mismatch between agricultural demand and local ecology. Assured procurement, electricity pricing, market access and perceived production risks influence farmers’ decisions. Crop diversification therefore requires reliable markets and institutional support rather than conservation appeals alone. Millets, pulses and suitable oilseeds can reduce irrigation demand in appropriate agroclimatic settings.

Drip irrigation applies water near the root zone; sprinklers distribute it under pressure. Both can improve application efficiency when appropriately designed. However, field-level savings do not automatically become basin-level savings: farmers may expand irrigated area, while reduced seepage may also reduce groundwater recharge. Excess irrigation without drainage can cause waterlogging and salinisation, lowering soil productivity.

• Demand management includes irrigation scheduling, soil-moisture conservation, mulching and agronomically appropriate crop choices.
• Environmental flows sustain river ecosystems and downstream functions; rivers cannot be treated solely as irrigation channels.
• Treated wastewater can substitute for freshwater in selected industrial and agricultural uses when quality standards and health safeguards are met.

4. Institutions, laws and major programmes

Entry 17 of the State List covers water supplies, irrigation, canals, drainage, embankments, water storage and water power, subject to Entry 56 of the Union List. Entry 56 concerns regulation and development of inter-State rivers and river valleys when Parliament declares Union control expedient in the public interest. Article 262 enables parliamentary provision for adjudication of inter-State water disputes and exclusion of court jurisdiction over specified disputes.

The Inter-State River Water Disputes Act, 1956 provides a statutory dispute-resolution framework. The Water (Prevention and Control of Pollution) Act, 1974 establishes mechanisms for preventing and controlling water pollution through pollution-control boards. The Central Water Commission deals with surface-water assessment and related technical functions; the Central Ground Water Board assesses and studies groundwater resources.

Pradhan Mantri Krishi Sinchayee Yojana, launched in 2015, promotes irrigation access and water-use efficiency through its programme architecture. Jal Jeevan Mission, launched in 2019, seeks functional household tap connections in rural areas, with emphasis on adequate quantity, prescribed quality and regular supply. Atal Bhujal Yojana promotes community-led groundwater management in selected water-stressed areas of seven states. Namami Gange combines pollution abatement with river-conservation measures.

• Atal Bhujal Yojana covers selected areas in Gujarat, Haryana, Karnataka, Madhya Pradesh, Maharashtra, Rajasthan and Uttar Pradesh.
• Jal Shakti Abhiyan: Catch the Rain promotes rainwater conservation and harvesting.
• A tap connection is an access indicator; lasting service also depends on source sustainability, maintenance and water quality.

5. Conservation and integrated management

Integrated water-resources management coordinates land, water and ecosystem management at an appropriate hydrological scale. Watershed treatment uses contour bunds, vegetative measures, check dams and soil conservation to slow runoff and improve infiltration. Traditional systems—including johads in Rajasthan, ahar-pynes in Bihar and eris in Tamil Nadu—illustrate locally adapted water management.

Urban priorities include protecting lakes and floodplains, restoring drainage channels, reducing distribution leakage and treating sewage. Floodplain encroachment and impermeable surfaces increase runoff and reduce recharge. Climate change adds uncertainty through changing rainfall intensity, drought risk and cryospheric changes. Resilience therefore requires diversified sources, credible water budgets, drought planning and transparent monitoring rather than dependence on a single large project.

• Supply augmentation and demand reduction should be planned together.
• River-linking proposals require basin-specific evaluation of ecological effects, displacement, costs and assumptions about surplus water.
• Participatory aquifer management connects individual pumping decisions with the shared nature of groundwater.

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