Thursday, June 5 is World Environment Day. To mark the occasion the United Nations Environment Program (UNEP) is calling for greater steps to safeguard the world's fresh water resources.

Finding fresh, clean water is already a problem for millions of people in the world. And it is a problem that kills.

The United Nations says water-related diseases kill a child every eight seconds and are responsible for 80 percent of all illnesses and deaths in the developing world. If people had access to clean water, U.N. officials say, most of these deaths could be prevented. But clean water is likely to become even rarer.

Officials at the U.N. Environment Program say that within 25 years, half the world's six billion people could have trouble finding fresh water for drinking and irrigation. They say steps must be taken now, starting with more effective measures to preserve and manage existing supplies of fresh water, to prevent a bad situation from getting worse.

A spokesman for the U.N. Environment Program, Michael Williams, says one of the reasons there is a health crisis in Africa is that many people do not have access to supplies of fresh water.

"They lead to a lot of health problems. The water quality is damaged by being polluted by human waste and other pollutants," he explained. "So, the problem is visible there day by day. And, the problem they will face is that there is a growing demand for more fresh water. And as new infrastructure is created and so forth, they will come into an impossible situation."

U.N. statistics show one person in six lives without regular access to safe drinking water.

Mr. Williams says fresh water supplies also are running out in wealthy countries. Although water there continues to flow out of the taps, he says much of the groundwater is being depleted.

"For many people, water has been considered essentially a free commodity. And, therefore, there has not been much incentive to use it efficiently," he said. " We certainly have the problem of infrastructure not receiving the necessary investments and therefore a lot of wastage as pipes leak and so forth. We see a lot of conflicts again over who politically controls water. So, for example, certain agricultural interests might have an advantage in using water for crops perhaps that are very water intensive and are being grown in dry countries."

Mr. Williams says human demands for water are also depleting the world's rivers and wetlands. And, this, he adds, will have a lasting impact on the world's biodiversity as many different kinds of migratory birds, fish and animals depend on these systems.