The textile and fashion industry is one of the heaviest consumers of the world's water. It uses more than 79-trillion litres of water a year – enough to fill 31.6-million Olympic-sized swimming pools. The industry has a long supply chain – from production to retail – and each has an environmental impact. Take cotton, for example. Between 7,000 and 29,000 litres of water are used to produce 1kg of raw cotton, depending on where it's grown. One T-shirt can take up to 2,700 litres of water to make. That's enough drinking water for one person for 3 years.