Yamuna & water
What is groundwater extraction?
Stage of groundwater extraction is how much of the water that refills an aquifer each year is taken back out of it each year, as a percentage. Under 70 per cent an area is classed Safe; above 100 per cent the aquifer is being spent rather than used, because the balance comes out of storage that does not refill. Delhi's figure is 92.1 per cent, against a national average of 60.6.
A budget, not a level
The number is not how much water is down there. It is what share of the annual income is being drawn.
The Central Ground Water Board assesses each block, mandal or taluk separately — 6,762 of them nationally — and for each one estimates two quantities: how much water recharges the aquifer in a year, and how much is extracted from it. The ratio is the stage of extraction, and the category follows from the ratio.
This makes it a flow measurement, not a stock one. An area at 60 per cent is living on its income. An area past 100 per cent is drawing down a balance accumulated over centuries, and the drawdown is invisible until a borewell stops producing and has to be deepened.
Neither figure is metered. CGWB estimates both by a published methodology and calls them assessments, which is the honest description. They are the official numbers and the best that exist; they are not meter readings, and this site marks them accordingly.
- Assessment unit
- A block, mandal or taluk — the geography the category is assigned to. Delhi has 34.
- Stage of extraction
- Annual extraction divided by annual extractable resource, as a percentage.
- Over-Exploited
- Extraction past 100 per cent of annual recharge. The aquifer is being spent.
- bcm
- Billion cubic metres. The unit the national water budget is written in.
Where the lines are drawn
CGWB assigns a category from the ratio. Two of the four lines below are thresholds; the rest are Delhi's own figures against them.
Safe — below this share of annual recharge
70 %
CGWB categorisation, Dynamic Ground Water Resources 2025
Over-Exploited — above this share
100 %
CGWB categorisation, Dynamic Ground Water Resources 2025
Delhi, stage of extraction
92.1 %
CGWB, assessment year 2025
India, stage of extraction
60.6 %
CGWB, assessment year 2025
Delhi assessment units not classed Safe
27 of 34
CGWB, assessment year 2025
Delhi units Critical or Over-Exploited
21 of 34
CGWB, assessment year 2025
India, annual extraction
247.18 bcm
CGWB, assessment year 2025
Delhi at 92.1 per cent is below the Over-Exploited line as a whole and well above the Safe one, and the aggregate hides the distribution: ten of its thirty-four units are individually Over-Exploited. A city-wide average conceals an emptying aquifer the same way a city-wide air figure conceals a bad monitor.
This is not a legal limit in the sense the air standards are. Nobody is prosecuted at 101 per cent. It is a published categorisation with statutory consequences attached in places — extraction permissions, notified areas — rather than a notified standard.
How to read it against the river
Surface water and groundwater are one system, and Delhi's numbers only make sense together.
A city whose river is unusable for most of its length gets its water from somewhere. Part comes from upstream abstraction at Wazirabad — which is why the Delhi stretch has almost no flow left — and part comes from underneath. The two numbers are describing one shortage from two directions.
The assessment is annual and the category is sticky. A unit does not move between Safe and Critical on a wet monsoon; it moves when the multi-year balance moves, which is the right timescale for the thing being measured and a poor one for noticing an emergency.
Recharge is itself affected by what is built on top. Paving a floodplain removes the surface that fed the aquifer beneath it, so extraction and recharge are not independent variables.
What this number cannot tell you
- It cannot tell you how much water is left. It is a rate, not a stock, and CGWB does not publish an aquifer volume.
- It cannot tell you about quality. Salinity, nitrate, fluoride and arsenic are separate assessments, and a Safe unit can be undrinkable.
- It cannot be read at street level. The unit is a block; a single failing borewell is invisible in it and so is a single recovering one.
- It is estimated, not metered. Both terms of the ratio are assessments by a published method.
Where this comes from
Every figure above is read out of one of these, at the address printed beside it.
- National Compilation on Dynamic Ground Water Resources of India, 2025 Central Ground Water Board, Ministry of Jal Shakti · Published November 2025 — every figure above
- Dynamic Ground Water Resources of India Central Ground Water Board · The annual series and its methodology
Reuse freely — CC BY 4.0. The grant covers this page. Each source above keeps its own terms, which is why every one of them is named.
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