* World Water Day raises debate on climate change
* Environmentalists see water supplies decreasing
* Some push a "blue" policy agenda
By Deborah Zabarenko, Environment Correspondent
WASHINGTON, March 22 (Reuters) - If water is the new oil, is blue the new green?
Translation: if water is now the kind of precious commodity that oil became in the 20th century, should delivery of clean water be the same sort of powerful political force as the environmental movement in an age of climate change?
And, in another sense of green, is there money to be made in a time of water scarcity?
The answer to both questions, according to environmental activists watching a global forum on water, is yes.
The week-long meeting in Istanbul ends Sunday, which is International World Water Day, an annual United Nations event that began in 1993 to focus attention on sustainable management of fresh water resources.
The yearly observance recognizes water as an absolute human need: people can live as much as 30 days without food but only seven without water. How long can a person live without oil?
More than a billion people lack access to clean water, and 2.5 billion are without water for sanitation, with 80 percent of all disease borne by dirty water.
This may seem ironic, since Earth is literally a blue planet when seen from space -- most of it is covered in water. But what humans need is water that is fresh and clean, and most of Earth's water is salty or dirty.
What was clear at this year's World Water Forum in Turkey was the notion that clean, fresh water supplies are waning due to a warming world.
"As climate change accelerates and we see a changing hydrological cycle, diminishing access to resources, there are direct human impacts that are water-related," said Jonathan Greenblatt, a professor at the University of California-Los Angeles who advised the Obama transition team on civic engagement and national service.
If sea levels rise as scientists predict, coastal regions may see increased salination of aquifers -- natural underground reservoirs -- which will affect access to fresh water in those areas, Greenblatt said.
In some areas, such as central China, desertification is occurring directly outside Beijing, with desert-like conditions coming to areas that were once fertile, he said.
"In the same way that climate change has become part of the conversation ... the agenda of legislators and policymakers, I think blue needs to be part of the agenda," Greenblatt said, using "blue" as shorthand for water.
There is a high return on investment in clean water projects, the World Health Organization reported: every $1 spent on water and sanitation can bring economic benefits averaging between $7 and $12.
Healthcare agencies could save $7 billion a year, employers could gain 320 million productive days a year for workers in the 15-to-59 age range, there could be an extra 272 million school attendance days annually and an added 1.5 billion healthy days for children under the age of 5, WHO said.
In dollars and cents, an investment of $11.3 billion a year could yield a payback of $83 billion a year in increased productivity and health, the Natural Resources Defense Council said in its blog written from the forum, here
"As many have pointed out in this week's debates, this payback makes a very strong argument in favor of promoting safe water and sanitation in these difficult financial times," the council's Melanie Nakagawa wrote.
The water forum does not go far enough in making this a top agenda item, the conservation group WWF International said.
"...(I)t is the well-managed or restored river systems that cope best with climate change impacts we are seeing now and those that are yet to come," James Leape, the group's director general, said in a statement. "This is clearly an issue of water management, but the ministerial declaration flowing from the World Water Forum is more a collection of platitudes than a plan for action."
So does the world really need a water day?
Maybe not, said Susan Keane, a public health expert with the Natural Resources Defense Council.
"I don't know why anyone should need to be reminded of this, because it's so obviously important and so obviously solvable," Keane said by telephone. "The answer really is people are blind to the obvious. It's not sexy."
(Editing by Eric Beech) (For more Reuters information on the environment, see blogs.reuters.com/environment/ )