Two and a half years of one person’s drinking water fits inside a single plain cotton T-shirt.
That is the arithmetic behind a figure that gets quoted constantly, usually as 2,500 litres a shirt, sometimes as 2,700. It traces back to a detailed accounting of cotton’s water use by Ashok Chapagain and colleagues at the UNESCO-IHE Institute for Water Education, whose tally for a 250 gram T-shirt came to 2,720 litres. Roughly 1,230 litres of that is irrigation water, 1,110 litres is rain absorbed by the crop, and 380 litres is the volume needed to dilute the pollution generated along the way.
Where the litres actually go
Strip out the dilution component and the shirt still carries about 2,340 litres, most of it drunk by the plant well before anyone spins a thread.
Cotton is a thirsty crop with an unfortunate habit of being grown in dry places. Chapagain’s report cited industry figures putting about 53 per cent of the world’s cotton area under irrigation, and that irrigated share produced 73 per cent of the global crop. Egypt, Uzbekistan and Pakistan carried much of it, along with China’s Xinjiang province, where the entire cotton area is irrigated.
Rivers that pick up the tab
What does that look like on the ground? WWF, which has run cotton programmes with farmers in Pakistan and India for two decades, estimates that 97 per cent of the Indus is now spoken for by crops like cotton. Its list of freshwater systems damaged by cotton irrigation and runoff runs from the Aral Sea to the Indus Delta to Australia’s Murray-Darling.
The Aral is the extreme case. Once the fourth largest inland sea on the planet, it has shrunk to about a tenth of its former volume in less than a generation, according to the Environmental Justice Foundation. Soviet planners began diverting the Amu Darya and Syr Darya, the rivers that feed it, to grow cotton in the desert, and their successors kept doing so after independence.
Every shirt is a water export
Nobody in Berlin or Melbourne is pumping that water, which is rather the point. The European Environment Agency estimates that around 85 per cent of the blue water used to produce textiles bought by EU households is consumed outside Europe, mostly in Asia. Researchers call the transferred footprint virtual water: the product crosses the border, while the depleted river or aquifer stays behind.
Chapagain’s team put numbers on that for the years 1997 to 2001. Uzbekistan was irrigating cotton with 14.6 cubic kilometres of surface and groundwater a year and exporting three of those cubic kilometres, in virtual form, to European consumers. On their accounting, shoppers in the EU25 were unwittingly responsible for about a fifth of the Aral Sea’s disappearance. That is one study using one window of trade data, but the mechanism has not changed.
Efficiency rose, consumption rose faster
A global modelling study led by Betelhem Demeke and published in Cleaner Production Letters in 2024 tracked the crop from 1972 to 2018 and found the average footprint per tonne of fibre dropped by 43 per cent, thanks mostly to better yields, cultivars and fertiliser. Cotton got substantially more efficient. Total water use still rose 5 per cent, and the irrigation component rose faster still, up 17 per cent on its own. The portion drawn from rivers and aquifers already stretched past their limits climbed from 59.3 to 70.9 cubic kilometres a year.
Around 71 per cent of that unsustainable volume left its country of origin embedded in traded cotton, with the United States, Pakistan and India together responsible for more than 60 per cent of it.
India carries the largest single share of the crop’s global water use, and reporting by Mongabay India puts that share at 38 per cent. The same coverage flagged an awkward result from research across four Indian states, including Maharashtra: drip irrigation can lift total water use rather than lower it, because farmers who save water tend to plant more.
Drip lines, flax and the limits of a tighter tap
Pakistan shows what better plumbing can and cannot fix. Researchers writing in Water Conservation Science and Engineering traced the country’s cotton chain from field to finished cloth and arrived at 22,596 cubic metres of water per tonne of fabric, with irrigation and pollution dilution outweighing rainfall. Drip systems, they calculated, could cut the crop-growing portion by nearly half. Their verdict on the chain as a whole was blunter: economically viable, environmentally and socially not.
Demeke’s group ended up somewhere similar and suggested a different plant entirely, running flax through the same model and finding it needs a fraction of the water for the same weight of fibre.
Which leaves the headline figure doing less work than it appears to. A 2,500-litre shirt grown under a capped, metered water entitlement is a different transaction from a 2,500-litre shirt drawing irrigation water from an overexploited Maharashtra aquifer. Even a licence is no guarantee, as the Murray-Darling shows. Same garment, same rack, same price tag. The bill lands on a river the shopper has never heard of.
