During winter, the irrigation canals and the riverbed were frozen and could not handle the larger volumes of w ater releases. This caused flooding and the need to divert water to the Arnasay depression further to the w'est of the river and away from the Aral Sea. The lake formed by such water releases was called Aydarkul. This has aggravated the ecological situation in the lower reaches of Syr Darya Basin (Schmidt-Soltau, 2004).