Surface water is a key resource for a country with an agriculture-based economy. Afghanistan has four major river systems with substantial hydroelectric and irrigation potential.
The legendary Amu Darya (2400 km; "darya" means "river" in Dari), known as the Oxus in ancient times, runs through the northern plains. It is a navigable river, with tributaries originating in the Pamir Knot glaciers. It once fed the Aral Sea, but now often runs dry in its lower reaches due to excessive irrigation under Soviet administration.
The Kabul River (700 km), a major tributary of the Indus River, traverses the capital and crosses the eastern border into Pakistan. A water treaty assuring Pakistan a share of the Kabul's volume is currently being drafted, prior to the construction of a dam on Afghanistan's side of the border.
The capital's 3.1 million inhabitants depend on Kabul River for water. It ran dry during the recent five-year drought. Thanks to strong rains, it returned in 2003, heralding cleaner water and more electricity for an ever-growing population.
The Helmand River (1,150 km), fed by streams from the Hindu Kush, flows south and southeast into Iran. It drains 160,000 square km, and is used extensively for agriculture. Iran and Afghanistan are presently reviewing a water-sharing treaty, as the river is much needed for irrigation by both countries.
Finally, in northwest Afghanistan, the Hari Rud (1,130 km; "rud" means "river" in Farsi) irrigates the fertile Herat Valley, historically renowned for dense cultivation.
Drought has been frequent in Central and South Asia, so demand for water is high. Afghanistan shares its river systems with neighboring, lower riparian countries Tajikistan, Turkmenistan, Uzbekistan, Pakistan and Iran. Thus, irrigation and hydroelectric projects inside Afghanistan may affect the flow of water to those countries. Water sharing treaties, such as those being negotiated with Iran and Pakistan, aim to ensure a fair distribution of this precious resource to the region.