The news comes as South East England braces itself for a hosepipe ban following the worst drought to hit the country in 30 years and amid global concerns about water shortages.
Grayling won the brief after being approached by the WWC, co-organiser of the World Water Forum, with the agency’s corporate and public affairs teams in France and the UK reporting to the organisation's president Lowic Fauchon.
They agency teams will be working to raise awareness, attract participants and promote the council and its members during the sixth forum of its kind.
Currently a project brief, there will be the potential for a longer term contract.
Michael Murphy, Grayling global CEO, said: 'We are delighted to be part of the team as the World Water Council plans for the sixth World Water Forum.
'Grayling brings its specialist expertise in sustainability and environmental issues combined with our core strengths in comms, PR and social media. I have no doubt our team will bring real passion to the partnership in support of this global cause.'
The World Water Forum’s goal is to tackle the challenges of water issues and to raise it on the political agenda.
The event takes place every three years and gathers all stakeholders around local, regional and global issues. The 2012 Forum will take place in Marseilles on 12–17 March.