Groundwater: the resource and how it is assessed

Detail

1. What groundwater is

• Groundwater is fresh water stored under the ground. It sits in the tiny gaps (pores) between soil grains and in cracks in rock.
• Aquifer is a layer of rock or soil under the ground that can both hold groundwater and let it move in useful amounts. People reach it through dug wells, tube wells and borewells. Water can also flow out of it on its own into springs, streams and rivers [5].
• Worldwide, groundwater makes up nearly 99% of Earth's liquid fresh water [5].
• How groundwater is recharged (refilled):
• Rain falls, or water flows in rivers, canals, tanks and ponds.
• Some of it seeps (infiltrates) down through soil and rock.

• It fills the aquifer, and the water table (the top level of the saturated zone) rises.

• Why it matters: groundwater keeps many rivers flowing in the dry season. It also supports wetlands [5].

2. How much India has, and how much it uses

Measure	Figure	Year/source
Total replenishable groundwater	about 432 cubic km	NCERT, Class 12
Total annual groundwater recharge	446.90 BCM (billion cubic metres; 1 BCM = 1 cubic km)	DGWRA 2024 [2]
Annual extractable groundwater resource	406.19 BCM	DGWRA 2024 [2]
Annual extraction for all uses	245.64 BCM	DGWRA 2024 [2]
National stage of extraction	60.47%	DGWRA 2024 [2]

• The current recharge figure is 446.90 BCM (2024) [2] (NCERT: about 432 cubic km).
• India is the world's largest user of groundwater. In 2026, groundwater met:
• about 62% of irrigation needs (NCERT-era figure: over 60%),
• 85% of rural water use,

• 50% of urban water demand [5].

• Why use grew so fast: drilling and pumps became cheap. Even small farmers and poor households could then sink their own tube wells [5].

• Groundwater quality problems: water is polluted by mining, factory waste and farm chemicals. Some rocks also release arsenic and fluoride naturally [5].

3. Level of use by state (NCERT, Class 12)

Level of use	States	Why
Very high	Punjab, Haryana, Rajasthan, Tamil Nadu (highest in the south)	Rice-wheat farming through the Green Revolution, free or cheap power for pumps, dry climate (Rajasthan), few large rivers that flow all year (Tamil Nadu)
Moderate	Gujarat, Uttar Pradesh, Bihar, Tripura, Maharashtra	A mix of canal and well irrigation
Low	Chhattisgarh, Odisha, Kerala	Heavy rain, plenty of surface water, and hard rock that is hard to tap

• Use is high in the north-western basins (Indus and upper Ganga) and in parts of the south.
• Punjab case (NCERT, Class 8): tube-well irrigation for rice and wheat has made the water table fall quickly.

4. Aquifer geography: alluvium vs hard rock

Feature	Alluvial aquifers	Hard-rock aquifers
Where	Indo-Gangetic-Brahmaputra plains (Punjab, Haryana, UP, Bihar, West Bengal, Assam)	About two-thirds of India: Deccan Plateau (Maharashtra), Karnataka, Telangana, Tamil Nadu, Chhattisgarh, Odisha
Rock type	Thick, loose layers of sand, silt and gravel laid down by rivers	Basalt (Deccan Traps: hardened lava) and granite-gneiss (very old crystalline rock)
Where water is stored	In pores between grains, across a large volume	Only in the weathered top layer and in cracks (fractures)
Storage and yield	High. Big tube wells can pump for long periods	Low. Wells give little water
Under heavy pumping	The water table drops slowly but steadily (e.g. Punjab, Haryana)	Wells run dry fast, often within one dry season

• Hard-rock problem, step by step:
• Hard rock has very little pore space.
• Farmers pump out the shallow cracked layer, then drill deeper borewells.

• The deep rock holds almost no water, so wells fail. This drives farm distress in Telangana, Karnataka and Marathwada.

• High-resolution mapping: heliborne geophysical surveys (instruments flown on helicopters to "see" rock layers underground) have mapped 97,165 sq km in 92 blocks of Rajasthan, Gujarat and Haryana (as of January 2026) [5].

5. Dynamic Ground Water Resource Assessment (DGWRA)

• Dynamic Ground Water Resource Assessment is a yearly joint study by the Central Ground Water Board (CGWB) and the state groundwater departments. "Dynamic" means it measures only the part of groundwater that is refilled each year. It does not count the deep, old (static) store.
• Assessment unit: the block (most states), taluk (e.g. Karnataka, Gujarat) or mandal (Andhra Pradesh, Telangana).
• For each unit it estimates:
• total annual recharge (from rain, canals, tanks and return flow from irrigation),
• extractable recharge (recharge minus the water that must stay in the ground to keep rivers flowing),

• annual extraction for irrigation, homes and industry.

• Stage of extraction = (annual extraction ÷ annual extractable recharge) × 100.

• 2024 example: 245.64 ÷ 406.19 × 100 ≈ 60.47% [2].

• Monitoring network: 43,228 groundwater-level monitoring stations (January 2026) [5].

• The 2024 report was released by the Union Jal Shakti Minister on 31 December 2024 [2].

6. Categories of assessment units

• Over-exploited groundwater block: a unit where yearly extraction is more than yearly extractable recharge (stage above 100%). The aquifer is being drained faster than nature refills it.

Category	Stage of extraction	Units in 2024
Safe	up to 70%	73.4% of units [3]
Semi-critical	70-90%	711 (10.5%) [2][3]
Critical	90-100%	206 (3.05%) [2][3]
Over-exploited	above 100%	751 (11.13%) [2][3]

• A separate "saline" class covers units where the fresh groundwater is too salty to use.
• Trend from 2017 to 2024:
• over-exploited units fell from 17.24% to 11.13% [3],
• safe units rose from 62.6% to 73.4% [3],

• total annual recharge rose by about 15 BCM, and extraction fell by about 3 BCM [2].

• Where over-exploited units cluster:

• North-west: Punjab, Haryana, Rajasthan, Delhi (alluvial aquifers drained by rice-wheat and city demand; dry Rajasthan).
• South and west: parts of Tamil Nadu, Karnataka, Telangana and Gujarat (hard-rock aquifers with low storage, plus North Gujarat's alluvium).

7. National Aquifer Mapping and Management Programme (NAQUIM)

• National Aquifer Mapping and Management Programme (NAQUIM): a CGWB programme that maps each aquifer's extent (where it is and how deep), yield (how much water it gives) and quality. The maps are used to make aquifer-wise management plans with states and communities.
• NAQUIM 1.0 (2012-2023):
• Mapping scale was 1:50,000.
• Of India's area of about 33 lakh sq km, the mappable area of about 25 lakh sq km was fully covered by 31 March 2023. Steep hills, ice and similar areas cannot be mapped [5][4].

• Management plans were shared with state governments to carry out [4].

• NAQUIM 2.0 (2023 onwards):

• It collects finer, high-density data on water levels and quality.
• It gives scientific inputs down to Panchayat level [5].
• It focuses on water-stressed, coastal, urban, spring-shed (area that feeds a spring), mining, canal-command, deep-aquifer and poor-quality areas [5].
• Progress: 68 studies (38,600 sq km) in 2023-24 and 35 studies (21,524 sq km) in 2024-25. 40 studies (16,700 sq km) were under way in 2025-26 [5].

8. Law and governance

• Water is a State subject (Entry 17, State List). The Centre helps through the Ministry of Jal Shakti, the CGWB and the CGWA (Central Ground Water Authority) [5].
• Common-law rule: groundwater rights go with land ownership. A landowner can pump as much as they like, so there is no real limit on extraction.
• Model Groundwater Bills (2005, 2011, 2016) propose a public trust approach:
• Public trust means the state holds a shared resource for everyone, as a trustee (guardian), not as its owner.

• Under it, groundwater is treated as a common pool resource to be protected, conserved and regulated [6].

• 21 States/UTs have passed groundwater laws based on the Model Bill (as of January 2026). They include Bihar, Punjab, Haryana, Himachal Pradesh and West Bengal [5][6]. Many have set up state groundwater authorities.

• Related schemes:
• Atal Bhujal Yojana, launched 25 December 2019: community-led groundwater management in 7 states (Gujarat, Haryana, Karnataka, Madhya Pradesh, Maharashtra, Rajasthan, Uttar Pradesh), with an outlay of ₹6,000 crore. It also helps keep Jal Jeevan Mission water sources from running dry [5].
• Master Plan for Artificial Recharge to Groundwater 2020: about 1.42 crore rainwater-harvesting and recharge structures, to put about 185 BCM of water back into the ground [5].

Prelims Hooks

• NCERT puts India's replenishable groundwater at ~432 cubic km. DGWRA 2024 gives total annual recharge as 446.90 BCM and extractable resource as 406.19 BCM.
• Stage of extraction = extraction ÷ extractable recharge × 100. The national figure is 60.47% (2024).
• Category thresholds: Safe ≤70% · Semi-critical 70-90% · Critical 90-100% · Over-exploited >100%.
• Tamil Nadu is the southern state with the highest groundwater use. Kerala, Odisha and Chhattisgarh are low-use states. Trap: Bihar and UP are moderate, not very high.
• Over-exploited units fell from 17.24% (2017) to 11.13% (2024). Safe units rose from 62.6% to 73.4%.
• NAQUIM: run by CGWB, started 2012, scale 1:50,000, covered ~25 lakh sq km of mappable area by March 2023. NAQUIM 2.0 started in 2023 and works down to Panchayat level.
• Hard-rock aquifers (basalt, granite-gneiss) cover about two-thirds of India. Alluvial aquifers lie in the Indo-Gangetic-Brahmaputra plains.
• Groundwater meets about 62% of irrigation, 85% of rural and 50% of urban water needs (2026).
• Atal Bhujal Yojana covers 7 states. Punjab is not one of them, even though it is badly over-exploited.
• Model Groundwater Bill follows the public trust idea. 21 States/UTs have adopted it. Water is a State List subject.

Mains Points

• Over-extraction, cause → effect: free or cheap farm power, MSP-backed buying of rice and wheat, and cheap borewells lead to over-pumping. The result is a falling water table in Punjab, Haryana and Rajasthan, rising pumping costs, and arsenic and fluoride problems in some areas. Groundwater is the key buffer for farmers in India, so this threatens food and drinking-water security (GS-III).
• Geology decides how vulnerable an area is: alluvial plains have large storage but are being drained over time. Hard-rock regions (Deccan, Telangana, Karnataka) hold little water, so wells fail within a season. Each needs a different answer: crop diversification and power reform in alluvial areas, and recharge plus check dams in hard-rock areas (GS-I distribution, GS-III resources).
• Science-based management: the yearly DGWRA and NAQUIM's aquifer maps help target schemes such as Atal Bhujal Yojana, Jal Shakti Abhiyan and the 2020 Artificial Recharge Master Plan at stressed blocks. The 2017-2024 drop in over-exploited units shows these schemes can work.
• Legal gap: groundwater rights still go with land ownership, so extraction is effectively open-access. Moving to the public trust idea in the Model Bills, with community-level water budgeting, is needed for fair and lasting use (GS-III).