Water Resources of India: Availability and Utilisation

NCERT India: People and Economy — Unit III, Chapter 4 (Part 1)

Water: A Cyclic Resource Under Stress

Water is the most fundamental of all resources — without it, agriculture, industry, drinking, sanitation and ecosystems all collapse. Looking at the planet from space, it appears overwhelmingly blue: about 71 per cent of the Earth's surface is covered with water. Yet of this enormous quantity, only about 3 per cent is freshwater, and an even smaller fraction of that is effectively available for human use after we exclude polar ice, deep glaciers and inaccessible groundwater.

The availability of freshwater varies sharply across space and time. Some regions receive abundant monsoon rain in a few weeks, while others remain dry for most of the year. As populations rise and economies grow, the tensions and disputes over the sharing and control of this scarce resource have become contested issues among communities, regions and states. The careful assessment, efficient use and conservation of water are therefore essential to ensure development. This chapter discusses water resources in India — their geographical distribution, sectoral utilisation, and methods of conservation and management.

4.1 Water Resources of India

India occupies a striking position in the world's water statistics. The country has about 2.45 per cent of the world's surface area, holds 4 per cent of the world's water resources, but supports more than 17 per cent of the world's population. This mismatch — a small share of resources serving a large share of humanity — explains why water management is one of India's central development challenges.

The total water available from precipitation in the country in a year is about 4,000 cubic km. Out of this, the availability from surface water and replenishable groundwater taken together is 1,869 cubic km. However, only about 60 per cent of this can be put to beneficial uses because of topographical, hydrological and other constraints. Thus the total utilisable water resource^? in the country is only about 1,122 cubic km.

Surface Water Resources

There are four major sources of surface water^? in India: rivers, lakes, ponds and tanks. The country has approximately 10,360 rivers and tributaries longer than 1.6 km each. The mean annual flow in all the river basins of India is estimated at 1,869 cubic km. However, due to topographical, hydrological and other constraints, only about 690 cubic km — roughly 32 per cent of the available surface water — can actually be utilised.

The volume of water flowing in any river depends on the size of its catchment area (or river basin) and the rainfall it receives. Indian precipitation is highly uneven in space and is largely concentrated in the monsoon season. The Ganga, the Brahmaputra and the Indus have huge catchment areas. Because precipitation is relatively high in the catchments of the Ganga, the Brahmaputra and the Barak, these rivers — though they drain only about one-third of the total area of the country — carry about 60 per cent of the total surface water resources. Much of the annual flow in south-Indian rivers like the Godavari, the Krishna and the Kaveri has already been harnessed, but a great deal of work is yet to be done in the Brahmaputra and Ganga basins.

Groundwater Resources

The total replenishable groundwater^? resources of the country are about 432 cubic km. The level of groundwater utilisation is relatively high in the river basins of the north-western region and parts of south India. Groundwater utilisation is very high in the states of Punjab, Haryana, Rajasthan and Tamil Nadu. By contrast, states such as Chhattisgarh, Odisha and Kerala use only a small share of their groundwater potential, while Gujarat, Uttar Pradesh, Bihar, Tripura and Maharashtra withdraw at a moderate rate.

Lagoons and Backwaters

India has a vast coastline that is deeply indented in some states. Because of this irregular coast, a number of lagoons and lakes have formed where the sea meets the land. The states of Kerala, Odisha and West Bengal have vast surface water resources in these lagoons and backwaters. Although the water in these bodies is generally brackish (slightly salty), it is used for fishing and for irrigating certain salt-tolerant varieties of paddy, coconut and other crops.

4.2 Water Demand and Utilisation

India has traditionally been an agrarian economy: about two-thirds of the population depend on agriculture for their livelihood. So irrigation has always been the dominant claim on the country's water. From independence onwards, the development of irrigation has been a top priority of the Five Year Plans, and a series of multi-purpose river valley projects — the Bhakra-Nangal, Hirakud, Damodar Valley, Nagarjuna Sagar, Indira Gandhi Canal Project — have been built to harness rivers for irrigation, power and flood control.

As a result, India's water demand at present is dominated by irrigational needs. Agriculture accounts for the largest share of both surface and groundwater utilisation: it consumes about 89 per cent of the surface water and about 92 per cent of the groundwater withdrawn in the country. The industrial sector's share is limited to about 2 per cent of surface water and 5 per cent of groundwater. The domestic sector takes a higher share of surface water (about 9 per cent) than of groundwater. Looking ahead, with continued economic development, the shares of the industrial and domestic sectors are likely to rise, while the agricultural share is expected to fall.

Demand of Water for Irrigation

In agriculture, water is mainly used for irrigation. Irrigation is essential because rainfall in India is highly variable in space and time. Large tracts — the north-western plains and the Deccan plateau — are deficient in rainfall and prone to drought. Winter and summer are largely dry across most of the country, so it is impossible to practise agriculture without assured irrigation in those seasons. Even in well-watered states like West Bengal and Bihar, breaks in the monsoon or its outright failure create dry spells that damage standing crops.

Different crops have different water needs. Rice, sugarcane and jute require very large quantities of water that can only be supplied through irrigation. The provision of irrigation makes multiple cropping possible — that is, growing more than one crop on the same land in a year — and irrigated land has been found to give significantly higher yields than unirrigated land. Importantly, the high-yielding varieties (HYVs) of crops introduced in the Green Revolution^? need a regular supply of moisture, which only a developed irrigation system can guarantee. This is why the Green Revolution strategy has been most successful in Punjab, Haryana and western Uttar Pradesh — states with extensive irrigation networks.

In Punjab, Haryana and western Uttar Pradesh, more than 85 per cent of the net sown area is under irrigation. Wheat and rice are grown mainly with irrigation in these states. Of the total net irrigated area, 76.1 per cent in Punjab and 51.3 per cent in Haryana is irrigated through wells and tube-wells, indicating heavy reliance on groundwater. The over-use of groundwater has caused a decline in the water-table in these states. In some places like Rajasthan and Maharashtra, over-withdrawals have raised fluoride concentration in groundwater, and in parts of West Bengal and Bihar the same practice has increased arsenic concentration — with serious health consequences.

Emerging Water Problems: Per Capita Availability

The per capita availability of water in India is dwindling rapidly due to population growth. Available resources are also being polluted with industrial, agricultural and domestic effluents, further limiting the supply of usable water. The decline in per capita water availability^? is one of the clearest indicators of approaching water stress.

In 1951, when independent India's first census was taken, per capita annual water availability was about 5,177 cubic metres. By 2025 it is estimated to have fallen to about 1,341 m³, and projections suggest it will drop further to about 1,140 m³ by 2050. According to the international benchmarks of the Falkenmark Indicator, an annual availability below 1,700 m³ per person indicates water stress^?, and below 1,000 m³ indicates water scarcity^?. India has already crossed into the stress zone and is moving towards the scarcity threshold.

India's Frozen Reservoirs: Glaciers & Snowfields

Beyond rivers, lakes and groundwater, India has a vast frozen reserve of freshwater locked up in the Himalayan glaciers and snowfields. These act as natural water towers: they melt slowly through summer and feed the perennial rivers — the Ganga, the Brahmaputra and the Indus — long after the monsoon has retreated. The slow release of meltwater is what gives north-Indian rivers their year-round flow, in sharp contrast to the seasonal peninsular rivers like the Godavari and Krishna.

Putting It All Together