Water scarcity: causes and measures

Detail

What water scarcity means

• Water scarcity means there is less usable water than people need for drinking, cooking, farming and industry.
• The paradox: water is plentiful and renewable because the water cycle refills it every year. Yet many places in India still lack enough of it.
• Two reasons it becomes scarce:
• Natural: the amount of water changes from season to season and from year to year with the rain. In India most rain falls in the four monsoon months.

• Human, and more important: Class 10 NCERT stresses that scarcity comes less from low rainfall and more from over-exploitation (taking out more than nature puts back), excessive use and unequal access among social groups. Rich farmers and housing societies can dig deeper wells, while poorer groups cannot.

• A NCERT prediction (Class 10) says nearly two billion people would face absolute water scarcity by 2025.

Main causes of scarcity

Driver	How it creates scarcity
Large, growing population	More water is needed at home, and more water is needed to grow more food
Irrigated agriculture	The largest user of water. Dry-season (rabi) crops are watered from private wells and tubewells
Industrialisation	Factories use large amounts of water. They also need electricity, and much of it comes from hydropower (dams)
Urbanisation	Cities grow fast. Housing societies and colonies pump their own groundwater through borewells, so the water table falls

• Irrigation → groundwater fall chain:
• Food demand rises → farmers grow a second or third crop in the dry season.
• Rain is absent in that season → private tubewells pump groundwater.

• Pumping is faster than recharge (rainwater seeping back into the ground) → the water table (the top level of underground water) falls → wells dry up.

• Groundwater status in figures (CGWB, Dynamic Ground Water Resource Assessment 2024):

• Total annual groundwater recharge: 446.90 BCM (billion cubic metres). Annual extractable resource: 406.19 BCM. Annual extraction for all uses: 245.64 BCM [5].
• Stage of groundwater extraction (extraction ÷ extractable resource × 100) for India: 60.47% (2024) [5].
• Of 6,746 assessment units (blocks, mandals, talukas), 751 (11.1%) are over-exploited and 4,951 (73.4%) are safe (2024). The over-exploited share fell from 17.24% in 2017 to 11.13% in 2024 [5].
• Categories: Safe ≤70%; Semi-critical >70–90%; Critical >90–100%; Over-exploited >100% [5].
• Punjab: extraction of 26.27 BCM against an extractable resource of 16.80 BCM, so the stage of extraction is 156.36%. Rajasthan: 147.11% (latest CGWB assessment) [6]. Both states take out far more than the rain puts back. Class 8 NCERT uses Punjab as its example of falling groundwater.

Scarcity of quality (qualitative scarcity)

• Qualitative scarcity: water is present but unfit to use because it is polluted by domestic sewage, industrial waste, chemicals or agricultural run-off.
• Class 10 Exercise 1(i): a high-rainfall region can still be water-scarce if:
• it has a very large population that needs more water than it has, or

• its water is polluted.

• Scarcity is therefore about quantity and quality together, not about rainfall alone.

Per capita water availability

• Per capita water availability is the amount of water available for each person in a year, measured in cubic metres (m³). Total water stays about the same, so this figure falls as the population grows. Class 12 NCERT says it is "dwindling day by day".

Year	Per capita availability (m³/person/year)
1951	5,177
2001	1,816
2011	1,545
2021	1,486
2031 (projected)	1,367

• These are the official Ministry of Jal Shakti figures. The ministry says the fall is caused by the increase in population [2].
• India crossed the 1,700 m³ stress line between 2001 and 2011, so the country is now water-stressed [2].

Falkenmark indicator

• Falkenmark indicator (Malin Falkenmark, a Swedish hydrologist, 1989): it measures how much renewable water each person gets in a year and sorts countries or basins into bands.

Band	Water per person per year
No stress	above 1,700 m³
Water stress	below 1,700 m³
Water scarcity	below 1,000 m³
Absolute scarcity	below 500 m³

• The Government of India uses the same 1,700 m³ (stress) and 1,000 m³ (scarcity) cut-offs [2].
• India as a whole is water-stressed. Several river basins are already water-scarce:
• Sabarmati (rises in the Aravallis in Rajasthan and flows through Gujarat into the Gulf of Khambhat),
• Pennar (Karnataka and Andhra Pradesh, flows into the Bay of Bengal),
• the west-flowing rivers of Kutch and Saurashtra (Gujarat, an arid area with short seasonal rivers),

• Cauvery (rises at Talakaveri in the Brahmagiri hills of Karnataka, flows through Tamil Nadu into the Bay of Bengal, and is the subject of a long inter-state dispute).

• Pattern: most scarce basins are in the rain-shadow and semi-arid parts of the west and south Peninsula, where rain is low and population and irrigation demand are high.

Day Zero: scarcity in cities

• Day Zero: the day a city's taps run dry because its reservoirs fall below the level from which water can be supplied.
• Cape Town (South Africa), 2018: after a multi-year drought, the city narrowly avoided Day Zero through strict water rationing.
• Chennai (Tamil Nadu), June 2019: the city's four main reservoirs dried up.
• Chennai gets high annual rainfall, but mostly from the north-east monsoon (October–December).
• That monsoon failed → the reservoirs were not refilled.

• Built-over wetlands and lakes could no longer store rain or recharge groundwater → the crisis got worse. This shows that mismanagement, not low rainfall, causes scarcity.

• Bengaluru (Karnataka), 2024: severe shortage as thousands of borewells failed when the groundwater fell.

• NITI Aayog, Composite Water Management Index (CWMI), June 2018:
• It said India is facing the worst water crisis in its history, with nearly 600 million people under high to extreme water stress [3][4].
• It warned that 21 major cities (including Delhi, Bengaluru, Chennai and Hyderabad) could run out of groundwater by 2020. The government later noted that this estimate counted only annual recharge and extraction and left out water in deeper aquifers (water-bearing rock layers deep underground) [4].

• CWMI has 9 sectors and 28 indicators. They include groundwater, restoring water bodies, irrigation, farm practices, drinking water, and policy and governance [3].

• The other face of the same problem: cities that run dry in summer also flood in the monsoon (Chennai in 2015, Bengaluru in 2022). Lakes, drains and floodplains have been built over, so rain cannot soak in or be stored. Lost lakes cause both urban flooding and Day Zero (see human-settlements).

Measures to meet scarcity

• Conservation and management (Class 10 NCERT): protect water bodies from pollution, cut waste, and share water fairly between social groups.
• Regulate groundwater pumping: match extraction to recharge, especially in over-exploited blocks of Punjab, Haryana and Rajasthan [5][6].
• Rainwater harvesting: collect rain from rooftops and catchments and send it into the ground to raise the water table.
• Efficient irrigation: since agriculture uses the most water, saving water in farming saves the most overall.
• Treat and reuse wastewater to solve quality scarcity in cities.
• Revive urban lakes and wetlands to hold monsoon water. This cuts both floods and Day Zero risk.

Prelims Hooks

• Falkenmark indicator (1989): <1,700 m³ = stress, <1,000 m³ = scarcity, <500 m³ = absolute scarcity (per person per year).
• India's per capita water availability: 5,177 m³ (1951) → 1,545 m³ (2011) → 1,486 m³ (2021) → 1,367 m³ (2031, projected). India is water-stressed, not yet water-scarce, at the national level.
• Largest consumer of water in India: irrigation (agriculture), not industry or domestic use.
• CGWB stage of extraction categories: Safe ≤70%, Semi-critical 70–90%, Critical 90–100%, Over-exploited >100%. National average 60.47% (2024).
• Punjab (~156%) has a higher stage of groundwater extraction than Rajasthan (~147%). Both are over-exploited.
• Trap: a high-rainfall region can be water-scarce, because of a large population or polluted water. Chennai in 2019 is the example.
• Day Zero pairs: Cape Town, 2018 (avoided); Chennai, June 2019 (reservoirs dry); Bengaluru, 2024 (borewells failed).
• CWMI is published by NITI Aayog (June 2018). It has 9 sectors and 28 indicators and warned that 21 cities could run out of groundwater by 2020.
• Water-scarce basins: Sabarmati, Pennar, Cauvery, west-flowing rivers of Kutch–Saurashtra.

Mains Points

• Scarcity is mostly man-made (GS-I/III): over-exploitation, excessive use and unequal access matter more than rainfall. Pumping beyond recharge has left 751 blocks over-exploited (2024), mainly in the north-west (Punjab and Rajasthan above 140%). This threatens food security in the Green Revolution belt.
• Population pressure and falling per capita availability: availability fell from 5,177 m³ (1951) to about 1,486 m³ (2021) as population grew, pushing India below the Falkenmark stress line. Semi-arid basins (Sabarmati, Pennar, Cauvery, Kutch–Saurashtra) are already scarce. This feeds inter-state disputes such as the one over the Cauvery.
• Urban water paradox (GS-III, disasters): Chennai (2019) and Bengaluru (2024) show Day Zero and urban floods sharing one root cause: encroached lakes, wetlands and drains plus unregulated borewells. Fixes include rainwater harvesting, lake revival, wastewater reuse and groundwater regulation.
• Quality as scarcity: polluted surface water and groundwater turn plentiful water into unusable water. Water policy must therefore cover pollution control as well as supply.