Of these 48 countries, 40 are either in the Near East and North Africa or in sub-Saharan Africa. Over the next two decades population increase alone—not to mention growing demand per capita—is projected to push all of the Near East into water scarcity. By 2050 the number of countries facing water stress or scarcity will rise to 54, and their combined population to 4 billion people—40% of the projected global population of 9.4 billion (69, 181).

The Near East and North Africa. The 20 countries of the Near East and North Africa face the worst prospects. The Near East is the most water-short region in the world. In fact, the entire Near East "ran out of water" in 1972, when the region's total population was 122 million, according to Tony Allan, a University of London expert on water resources (117). Since then, the region has withdrawn more water from its rivers and aquifers every year than is beingreplenished. Currently, for example, Jordan and Yemen withdraw 30% more water from groundwater aquifers every year than is replenished (49, 138). Also, Israel's annual water use already exceeds its renewable supply by 15% (139).

Saudi Arabia presents one of the worst cases of unsustainable water use in the world. This extremely arid country now must mine fossil groundwater for three-quarters of its water needs. Fossil groundwater depletion in Saudi Arabia has been averaging around 5.2 billion cubic meters a year (139).

Of 14 countries in the Near East, 11 are already facing water scarcity (139). In five of these countries the populations are projected to double within the next two decades. Water is one of the major political issues confronting the region's leaders (117). Since virtually all rivers in the Near East are shared by several nations, current tensions over water rights could escalate into outright conflicts, driven by population growth and rising demand for an increasingly scarce resource (139).

Four Gulf states—Bahrain, Kuwait, Saudi Arabia, and the United Arab Emirates—have so little freshwater available that they resort to desalinization, the costly conversion of sea water into freshwater. Without desalinization, the Gulf states would be unable to support anywhere close to their current populations. Bahrain's population depends completely on desalinization of seawater from the Gulf. It has virtually no freshwater at all (157). Desalinization, however, is far too expensive and impractical for most water-short countries, not to mention land-locked countries, either today or in the foreseeable future.

Sub-Saharan Africa. Much of sub-Saharan Africa is facing serious water constraints (59, 61). Nearly 200 million people live in Africa's water-stressed countries. While only 6 million live in countries facing water scarcity, rapid population growth will make this problem worse. By 2025 as many as 230 million people will be living in African countries facing water scarcity (59, 61). Another 460 million will be in water-stressed countries of Africa.

Water problems within countries. Parts of many large countries, such as India, China, and the United States, would be considered to face water stress or water scarcity if calculations were made regionally rather than nationally. Already, 19 major Indian cities face chronic water shortages (109). India as a whole is expected to enter the water-stress category by 2025.

China, which has 22% of the world's population but only 7% of all freshwater runoff, will narrowly miss the water stress category's cutoff point of 1,700 cubic meters per capita in 2025 (138). China's freshwater supplies have been estimated to be capable of sustainably supporting 650 million people—only half of the country's current population of 1.2 billion (149). Despite periodic flooding in the south, along the Yangtze River, China faces chronic freshwater shortages in the northern part of the country affecting—92 million people in the Hai river basin alone (15, 69). Many of China's cities, including Beijing, face critical water shortages. The water table under Beijing has been dropping by roughly two meters per year, and one-third of the wells have dried up.

Even in the US, which has plenty of water on a national basis, groundwater reserves are being depleted in many areas. Overall, groundwater is being used at a rate 25% greater than its replenishment rate (133). In the western part of the country, groundwater aquifers are being depleted at even faster rates in some areas. In particular, the huge Ogallala aquifer, which underlies parts of six states and irrigates 6 million hectares, has been overexploited. In some regions half of its available water has been withdrawn (183).