Garagum Canal, irrigation and drinking-water conduit, Turkmenistan, the longest canal in the former Union of Soviet Socialist Republics (USSR) and one of the longest in the world. The Garagum Canal extends 1,400 km (870 mi) from its headworks on the Amu Darya River to the town of Krasnovodsk on the Caspian Sea. About 1100 km (about 682 mi) of the canal, from the Amu Darya to the town of Gazanjyk, is uncovered. The remaining section to Krasnovodsk is an enclosed aqueduct. The construction of the canal from the Amu Darya to Ashgabat, the capital of Turkmenistan—a distance of 793 km (about 492 mi)—took only eight years (1954-1962) to complete. The remaining portion was finished in 1986. Almost half of the length of the canal is navigable by small rivercraft.

The water of the Garagum Canal is used primarily for irrigation; the canal is also an important source of drinking water. Cotton is the most important irrigated crop in the region. The irrigated lands fed by the Garagum Canal are the most productive in Turkmenistan and comprise one of the largest cotton-growing regions in the world.

Waterlogging and secondary salinization are major problems in areas adjacent to the canal, as most of the canal remains unlined. The canal is also the greatest single contributor to the desiccation of the Aral Sea; it receives the largest amount of water among all the irrigation structures in the Aral Sea basin. Compounding the problem, water diverted to the canal is not returned to the Aral Sea. Irrigated lands of the canal zone are at a lower elevation than the Aral Sea, making the return of used irrigation water to the Aral prohibitively expensive.