Business leaders from 45 companies, including Levi Strauss and H&M, have committed to improve their water management practices and are calling on governments to step up their efforts to tackle the global water crisis.

The chief executives attending the Rio 20 Earth Summit taking place in Rio de Janeiro in Brazil this week are backing the UN Global Compact's 'CEO Water Mandate.'

Efforts to expand their own water-management practices have seen Levi Strauss reduce the amount of water used to create its products - including a new method to produce jeans that uses significantly less water. This year, Levi's made more than 13m Water<Less products and saved over 172m litres of water.

Likewise, by 2020 H&M aims to source all its cotton from sustainable sources (organic cotton, Better Cotton, and recycled cotton) which require less water, pesticides and fertilizers. H&M is also in the process of developing a holistic water strategy in collaboration with WWF with the aim of integrating good water stewardship principles into core activities.

The companies also want governments to make more effort to develop policies and incentives to improve water productivity and efficiency in all sectors, establish a fair and appropriate valuation of water, and increase investment in infrastructure to improve water delivery.

The UN estimates around 800m people in the world lack access to safe drinking water, and 2.5bn lack basic sanitation - and that two-thirds of humanity will live in water-stressed regions by 2025.