Conveyance efficiency and irrigation water productivity under varying water supply conditions in arid lowlands of Central Asia

A proper assessment of the water allocation system and water–food production relationships is essential to identify water use reduction potentials and enhance crop water productivity in dry areas. However, limited data on crop-specific water uses and water losses in the system, especially in developing and transition countries, prevent consistent diagnosis of issues in water systems. A modeling framework based on maximum entropy approach was implemented here to simultaneously assess water system structure and ‘water use-crop production’ relationships. The framework allowed for the analysis of long-term changes in conveyance efficiency, crop-specific water application, and irrigation water productivity between 1980 and 2021 in the Khorezm region in the lower reaches of the Amu Darya Basin in Central Asia. The results showed that conveyance losses were more than 30% in the system, and approximately 40% of the water allocated to the region went to rice and cotton production, indicating the possibility of water use reduction in these three areas. Conveyance efficiency and cotton water productivity improved in drier years in the region, owing to the wide implementation of temporary and low-cost drought management measures. The expected increase in the frequency and magnitude of droughts may require long-term investment-demanding strategies for drought management to enhance the sustainable livelihoods in the region.