According to WWF the only international agreement that offers a real chance of making progress in this area has been gathering dust since it was written up in 1997.
The vast majority of countries voted in favour of the UN Watercourses Convention when it was table 12 years ago, but only 16 have ratified it since, making it ineffectual.
WWF welcomed the fact that a further 14 countries had pledged to support the treaty at the Instanbul event but argued more needed to be done.
The UN Watercourses Convention provides a framework for common and cooperative management for the rivers, lakes, wetlands and aquifers crossing or forming international borders.
“If fully enacted it would provide a strong basis for sharing and caring for the water draining half the world’s land surface and vital to the water supplies of 40% of humanity,” said Flavia Loures, WWF international water law and policy senior programme officer.
“It is ironic in the extreme that with a World Water day themed around sharing transboundary waters the ministerial declaration to be issued that day takes great pains to avoid mentioning the only available instrument for global co-operation,” Ms Loures said.
President of environmental pressure group Green Cross International Alexander Likhotal added: “As climate change further exacerbates the water crisis, the difficulties and cost of expanding and sustaining water security will rise, and potentially very steeply.
“The risks from failing to act are increasingly understood to be high, and include economic instability, loss of quality of life and reversal of gains in poverty reduction, more frequent disaster and ecological degradation. Therefore, we are calling for a swift ratification of the Convention.”
David Gibbs