Quantifying water volumes of small lakes in the inner Aral Sea Basin, Central Asia, and their potential for reaching water and food security

In the inner Aral Sea Basin of Central Asia, numerous small lakes scattered over the irrigated landscape supply diverse ecosystem services for humans and nature. This study aimed to estimate the water volumes and assess the potentials of these small lakes for instance as irrigation reserve during the ever-recurring periods of water scarcity in the ecologically endangered Amudarya Delta. Bathymetric measurements gathered in the Khorezm region, Northwest Uzbekistan, permitted developing a statistical relationship between the surface and volume of the lakes. Landsat satellite data enabled for classifying the water bodies and hence deriving lake volumes over the study area. In 2002, the lakes stored ~0.032 km³ water during the winter season, but ~0.057 km³ during the main, 5–6 months spanning irrigation period. The area-wide increase in lake volumes during the irrigation period underlined the magnitude to which the currently practiced, inefficient use of irrigation water, produces excess water that in turn contributes to the existence of the small, mesotrophic lakes. Based on crop water requirements, calculations showed that the reuse of lake water may compensate for water-scarce situations, albeit to a certain extend only. An increased share (13 % above average) of water-intensive rice fields in the vicinity of the lakes substantiated that some lakes are already used in this way. It is argued that, in case of sufficient water quality, as indicated by other studies, more targeted exploration of such lake water can help simultaneously both, increasing food and water security of the households surrounding the lakes and safeguarding a supply to maintain different ecosystem functions. Integrated management of all water resources may reduce excess irrigation water supply to the region, which in turn may lessen the dependency of Central Asian downstream countries on transboundary water and supply water resources for the ecosystems in the river deltas.