In The Guardian's article Cotton production linked to images of the dried up Aral Sea basin, it's claimed that organic cotton uses less water than conventional cotton.
“Conventional cotton (as opposed to organic cotton) has got to be one of the most unsustainable fibres in the world,” says fashion designer and environmentalist Katharine Hamnett. “Conventional cotton uses a huge amount of water and also huge amounts of pesticides which cause 350,000 farmer deaths a year and a million hospitalisations.”
Hamnett advises another key step - phasing out conventional cotton and investing instead in its far more sustainable counterpart: organic cotton.
The environmental impact of losing the Aral Sea is not yet known, what we do know is that the cotton that destroyed it, is cotton picked by forced labour and destined for European shops. This is the reality of a subcontracted deregulated industry not bound by any global environmental or minimum wage legislation.
The article makes some claims that I regard as very serious and very plausible - that Soviet and post-soviet countries use forced labour in picking cotton (addressed here), and have ruined the Aral Sea.
However, I'm rather doubtful about their claim that organic cotton uses less water. The Guardian's biography of the article's author indicates that she has written about capitalism and fashion previously, and been involved in various political campaigns, but doesn't mention a university-level science education. The person being quoted, Katherine Hamnett, is a fashion designer and environmentalist, which is someone who cares about the environment but isn't necessarily a knowledgeable expert about the environment or farming. The article doesn't describe how organic cotton uses less water than conventional farming. Also, the article is funded by industry, though they claim that they retain editorial independence for this article.
It's plausible that some farmers of cotton may use less water than other farmers of cotton, but does organic cotton use less water than conventional cotton?