Groundwater

Also called: Groundwater resources · Topic: Water Resources of India: Availability, Use and Conservation · NCERT: Class 6, Ch 2 "Oceans and Continents"; Class 6, Ch 3 "Landforms and Life"; Class 8, Ch 1 "Natural Resources and Their Use"; Class 12, Ch 4 "Water Resources"

Meaning

Groundwater is fresh water stored under the ground in the tiny gaps (pores) between soil grains and in cracks in rock. It is held in layers called aquifers and refilled by rain and by seepage from rivers, canals, tanks and ponds.

It matters because India is the world's largest user of groundwater. It meets about 62% of irrigation needs, 85% of rural water use and 50% of urban water demand (2026) [5]. So it supports both food security and drinking water.

Explanation

How groundwater forms and is recharged (refilled)

• Recharge chain:
• Rain falls, or water flows in rivers, canals, tanks and ponds.
• Some of this water seeps (infiltrates) down through soil and rock.

• It fills the aquifer, and the water table (the top level of the ground that is fully soaked with water) rises.

• Aquifer is a layer of rock or soil under the ground that can both hold water and let it move in useful amounts. People reach it through dug wells, tube wells and borewells. Water also flows 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].
• Why it matters for rivers: groundwater keeps many rivers flowing in the dry season and supports wetlands [5].

Types of aquifers in India: alluvium vs hard rock

Feature	Alluvial aquifers	Hard-rock aquifers
Rock	Thick, loose sand, silt and gravel laid down by rivers	Basalt (Deccan Traps, which is hardened lava) and granite-gneiss (very old crystalline rock)
Water stored in	Pores between grains, across a large volume	Only the weathered top layer and cracks (fractures)
Yield	High. Big tube wells can pump for a long time	Low. Wells give little water
Under heavy pumping	Water table falls slowly but steadily	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 the wells fail.

How it is measured: Dynamic Ground Water Resource Assessment (DGWRA)

• DGWRA is a yearly joint study by the Central Ground Water Board (CGWB) and the state groundwater departments.
• "Dynamic" means it counts only the groundwater that is refilled each year. It does not count the deep, old (static) store.
• Assessment unit: block (most states), taluk (e.g. Karnataka, Gujarat) or mandal (Andhra Pradesh, Telangana).
• Extractable recharge = recharge minus the water that must stay in the ground to keep rivers flowing.
• Stage of extraction = (annual extraction ÷ annual extractable recharge) × 100.

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

• Categories of units (2024):

Category	Stage of extraction	Share of units
Safe	up to 70%	73.4% [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]

• An over-exploited unit takes out more water each year than nature puts back.
• A separate "saline" class covers units where the groundwater is too salty to use.
• Monitoring: 43,228 groundwater-level monitoring stations (January 2026) [5].

Quality and law

• Pollution: mining, factory waste and farm chemicals pollute groundwater. Some rocks also release arsenic and fluoride naturally [5].
• Water is a State subject (Entry 17, State List). The Centre helps through the Ministry of Jal Shakti, the CGWB and the Central Ground Water Authority (CGWA) [5].
• Common-law rule: groundwater rights go with land ownership. A landowner can pump as much as they like.
• Model Groundwater Bills (2005, 2011, 2016) use the public trust idea. This means the state looks after groundwater for everyone as a guardian, not as its owner. Groundwater is treated as a common pool resource (a shared resource) [6].

Where it occurs

• Very high use (NCERT, Class 12): Punjab, Haryana, Rajasthan and Tamil Nadu, which has the highest use in the south.

• The causes are rice-wheat farming from the Green Revolution, free or cheap power for pumps, a dry climate in Rajasthan, and few rivers that flow all year in Tamil Nadu.

• Moderate use: Gujarat, Uttar Pradesh, Bihar, Tripura and Maharashtra, which use a mix of canal and well irrigation.

• Low use: Chhattisgarh, Odisha and Kerala, which have heavy rain, plenty of surface water and hard rock that is difficult to tap.
• Alluvial aquifers: the Indo-Gangetic-Brahmaputra plains (Punjab, Haryana, UP, Bihar, West Bengal and Assam).
• Hard-rock aquifers: about two-thirds of India, including the Deccan Plateau (Maharashtra), Karnataka, Telangana, Tamil Nadu, Chhattisgarh and Odisha.
• Clusters of over-exploited units:
• North-west: Punjab, Haryana, Rajasthan and Delhi, where rice-wheat farming and city demand drain the alluvial aquifers.

• South and west: parts of Tamil Nadu, Karnataka, Telangana and Gujarat (hard rock, plus the alluvium of North Gujarat).

• Farm distress from failing wells: Telangana, Karnataka and Marathwada.

• Punjab case (NCERT, Class 8): tube-well irrigation for rice and wheat has made the water table fall quickly.
• Mapping and schemes:
• NAQUIM (National Aquifer Mapping and Management Programme), run by CGWB:
  • NAQUIM 1.0 (2012–2023) mapped aquifers at 1:50,000 scale. It covered the mappable area of about 25 lakh sq km by 31 March 2023 [5][4].
  • NAQUIM 2.0 started in 2023 and gives inputs down to Panchayat level [5].
• Heliborne geophysical surveys use instruments flown on helicopters to "see" rock layers under the ground. They have mapped 97,165 sq km in 92 blocks of Rajasthan, Gujarat and Haryana (January 2026) [5].
• Atal Bhujal Yojana (launched 25 December 2019, outlay ₹6,000 crore) supports community-led groundwater management in 7 states: Gujarat, Haryana, Karnataka, Madhya Pradesh, Maharashtra, Rajasthan and Uttar Pradesh [5].
• Groundwater laws based on the Model Bill: 21 States/UTs, including Bihar, Punjab, Haryana, Himachal Pradesh and West Bengal [5][6].

Don't confuse with

• Dynamic vs static groundwater: dynamic groundwater is the part refilled each year, and only this is counted in DGWRA. Static groundwater is the deep, old store below it.
• Aquifer vs water table: an aquifer is the rock or soil layer that holds the water. The water table is only the top level of the soaked zone.
• Total recharge vs extractable resource: total recharge is 446.90 BCM. Extractable resource (406.19 BCM) is lower because some water must stay underground to keep rivers flowing [2].
• Critical vs over-exploited: a critical unit uses 90–100% of its recharge. An over-exploited unit uses more than 100%.

Prelims Hooks

• Stage of extraction = extraction ÷ extractable recharge × 100. The national figure is 60.47% (2024) [2].
• Thresholds: Safe ≤70%, Semi-critical 70–90%, Critical 90–100%, Over-exploited >100%.
• Over-exploited units fell from 17.24% (2017) to 11.13% (2024), and safe units rose from 62.6% to 73.4% [3].
• Tamil Nadu is the highest groundwater user in the south. Trap: Bihar and UP are moderate users, not very high, while Kerala, Odisha and Chhattisgarh are low users.
• Atal Bhujal Yojana covers 7 states. Trap: Punjab is not included, even though it is badly over-exploited [5].
• Hard-rock aquifers (basalt and granite-gneiss) cover about two-thirds of India. Alluvial aquifers lie in the Indo-Gangetic-Brahmaputra plains.

Mains Points

• Over-extraction, cause and effect (GS-III):
• Causes: free or cheap farm power, MSP-backed buying of rice and wheat, and cheap borewells (drilling and pumps became cheap enough for small farmers) [5].

• Effects: water tables are falling in Punjab, Haryana and Rajasthan, pumping costs are rising, and some areas have arsenic and fluoride problems. This threatens food and drinking-water security.

• Geology decides how vulnerable an area is (GS-I and GS-III):

• Alluvial plains store a lot of water but are slowly being drained. They need crop diversification and power reform.

• Hard-rock regions (Deccan, Telangana, Karnataka) store little water, so wells fail within a season. They need recharge structures and check dams.

• Science, law and recharge as the policy response:

• DGWRA and NAQUIM maps help send schemes like Atal Bhujal Yojana to stressed blocks.
• The Master Plan for Artificial Recharge to Groundwater 2020 plans about 1.42 crore structures to put about 185 BCM of water back into the ground [5].
• Since rights still go with land ownership, extraction is effectively open to all. Moving to the public trust model of the Model Bills, with community water budgeting, is needed for fair and lasting use [6].

Related concepts

• Dynamic Ground Water Resource Assessment
• Over-exploited groundwater block
• National Aquifer Mapping and Management Programme

Read more

• Groundwater: the resource and how it is assessed