In the not-too-distant future, the former Soviet Central Asia could be confronted with resource-based conflicts or even, as some observers have suggested, with a "water war." Water is the scarce commodity in a region that is rich in oil, gas, and mineral resources. Most of the water comes from two rivers, the Syr Darya and the Amu Darya. These feed the Aral Sea, previously the fourth largest inland fresh (actually brackish) water reservoir in the world. These rivers and their tributaries, together, form the Aral Sea basin. Since the 1960s, the Aral Sea has shrunk rapidly in surface area and in volume of water, representing "one of the world's worst ecological disasters." Increased demand for water for irrigation and hydroelectric power by the competing newly independent states, both upstream and downstream, is a potential source of interstate and even interethnic conflict. The latter could occur in the densely populated Ferghana Valley, where various countries such as Kyrgyzstan, Tajikistan, and Uzbekistan share common borders.