International Hydrological Programme
Arab States
More than 85% of the Arab region is classified as arid and hyper arid, receiving an average annual rainfall of less than 250 mm. The average annual precipitation for the Arab nations varies considerably, between 18 mm/year in Egypt and the Gulf countries and 827 mm/year in Lebanon.
The renewable freshwater availability in the Arab region is estimated at about 338 km³/year. More than 55% of this amount originates from outside the region. The water availability in this region has played a very dominating role in determining human activities, settlements, socio-economic interactions and growth. The Nile River hosted one of the greatest civilizations on Earth, as did the Euphrates and Tigris rivers. The ancient Yemeni civilization is closely tied to water resources availability, and its declination is historically related to the destruction of the ancient Maareb Dam.
Due to the scarcity of water resources in the region, non-conventional water supplies have been widely adopted in the form of desalination plants, and wastewater reuse programmes.
A number of international rivers exist in this region. These include the Nile River (Burundi, Congo, Egypt, Eritrea, Ethiopia, Kenya, Rwanda, Sudan, Tanzania, Uganda) and its tributaries, Senegal River (Guinea, Mali, Mauritania, Senegal), the Juba and Shebeli rivers (Ethiopia, Kenya, Somalia), the Tigris and Euphrates (Syria, Turkey, Iran, Iraq), and their tributaries.
About 20 different aquifer systems prevail throughout the asian Arabian countries and comprise semi-confined/shallow aquifers, and deep confined aquifer systems of different geological formation. Eight of these basins are considered as shared aquifers.
