At the Rio+20 meeting, Deputy Prime Minister Nick Clegg and the UK government announced that the UK will accede to the UN Watercourses Convention to help ensure that the world's 263 international boundary crossing rivers are protected and peacefully shared.

The announcement, made by Clegg at Rio+20, means the UK will join the growing number of countries agreeing to accede to the convention. The UK's accession will bring the number of Parties to the Convention closer to the 35 required for the Convention to enter into legal force.

The announcement came just weeks after WWF's Living Planet Report showed that globally, biodiversity in tropical rivers has declined 70 percent since 1970 - a steeper fall than for forest or oceans.

"Congratulations to Nick Clegg and the UK government for taking this important step in protecting our world's precious freshwater supplies. Our rivers and lakes are the lifeblood of our planet, vital for much of the world's growing population and a critical resource for our precious wildlife," WWF-UK's CEO David Nussbaum said.

"This UN Convention will encourage countries to work together to share this finite resource and avoid potential water conflicts, brought about by increasing demand, and unavoidable impacts of climate change. We hope other countries will follow the UK's example to make sure the Convention comes into force," Nussbaum further said.

When ratified the UN Watercourses Convention will help to protect rivers such as the Mekong which, with its tributaries, flows through six countries including China, Burma, Lao PDR, Cambodia, Thailand, and Vietnam, supplying a large proportion of the world's freshwater fish catch.

''The UK has done well to support these vital UN principles for fair watersharing between states. Nowhere is this more critical than in the Middle East, where Iraqi farmers now suffer from massive water-diversion projects built upstream on the Euphrates, and decades of denial of access to the Jordan increases the strain for Palestinians and Lebanon," Mark Zeitoun, Director of the UEA Water Security Research centre said.

The UN Watercourses Convention is a flexible and overarching global legal framework that establishes basic standards and rules for cooperation between watercourse states on the use, management, and protection of international watercourses.

"By signing up to the UN watercourses convention the UK has signalled its intention to help countries and people across the globe who need it most take a vital step towards water security, a step that consistent with its firm leadership on global climate governance," Zeitoun said.