Drainage in the Aral Sea basin

The intensity of irrigation in Central Asia requires artificial drainage in order to control waterlogging and salinization. There are about 5.35 million ha with a combination of surface drainage, and vertical and horizontal subsurface drainage. Of the five Central Asian republics, Uzbekistan is the country with the most significant artificially drained land, of approximately 1 million ha. There have been several innovations in drainage design in the region, in order to account for seepage from irrigation canals and upstream irrigated lands, percolation from excess irrigation water, groundwater fluxes to the root zone, and the accompanying salts moving into the crop root zone. Deeper subsurface drainage depths are considered essential for the control of waterlogging and salinity. There were significant investments in drainage in the region until the 1990s. However, with the collapse of the Soviet Union and the deterioration of economic conditions in Central Asia, investment in drainage declined. Drainage systems are no longer properly maintained and the areas suffering from salinization and waterlogging have been increasing. The drainage problems are compounded by the weakened institutional structure to successfully operate and maintain the drainage network. This paper addresses the technical and institutional improvements required to improve drainage performance, and stresses the importance of implementation of drainage with irrigation in the context of integrated water resources management. Copyright (C) 2007 John Wiley & Sons, Ltd.