Furthermore, only five countries in Africa are expected to attain the target of reducing by half the proportion of the population without sustainable access to basic sanitation by 2015, the deadline of the Millennium Development Goals (MDGs), a series of targets agreed to by all countries and leading development institutions to meet the needs of the world's poorest.

The Africa Water Atlas, compiled by UNEP at the request of the African Ministers' Council on Water, also maps out new solutions and success stories on water resources management from across the continent.

It contains the first detailed mapping of how rainwater conservation is improving food security in drought-prone regions. Images also reveal how irrigation projects in Kenya, Senegal and Sudan are helping to improve food security.

Some of the most arresting images in the Atlas, which was launched during Africa Water Week in Addis Ababa, the Ethiopian capital, include green clouds of eroded soil and agricultural run-off in Uganda, pollution from oil spills in Nigeria, and a three-kilometre segment of the Nile Delta that has been lost to erosion.

Prepared in cooperation with the African Union, the European Union, the United States Department of State and the United States Geological Survey, the 326-page Atlas gathers information about the role of water in Africa's economies and development, health, food security, transboundary cooperation, capacity building and environmental change in one comprehensive and accessible volume.

"The dramatic changes sweeping Africa, linked with both positive and negative management of this continent's vital water resources, is graphically brought home in this Atlas," said Achim Steiner, the UNEP Executive Director.

"From the dams triggering erosion on the Nile Delta to pollution in the Niger River Basin, the way infrastructure development or uncontrolled oil spills are impacting the lives and livelihoods of people are all brought into sharp relief. But so too are the many attempts towards sustainable management of freshwaters - for example, the controlled releases from dams on Chad's Logone River that are restoring in part the natural flooding cycles leading to the recovery of economically-important ecosystems.

"I am sure that the 'before and after images' presented in this Africa Water Atlas can also catalyze both greater awareness of the challenges and the choices and decisive, restorative and sustainable action on the ground," added Mr. Steiner.

The Africa Water Atlas also draws attention to Africa's "water towers", which are sources for many of Africa's trans-boundary rivers and contribute immensely to the total stream flow of African major rivers. They supply life-giving resources and services in downstream areas such as water for hydropower, wildlife and tourism, small-and large-scale agriculture, municipalities and ecosystem services.

The Atlas shows that most of these water towers, from the Middle Atlas Range in Morocco through to the Lesotho Highlands in southern Africa, are under extreme pressure as a result of deforestation and encroachment.