Climate-driven increases in crop water consumption in a Central Asian dryland catchment despite less water-intensive cropping

Dryland catchments are highly sensitive to climatic variability, with evapotranspiration dominating the water balance and strongly constraining water availability. In irrigated drylands, understanding how climate change and land-use transformations jointly affect crop water consumption is critical for sustainable water management. This study analyses long-term changes in agricultural water use in the Amu Darya Basin, the largest transboundary river basin in Central Asia and one of the world’s most water-stressed regions.

We classified annual crop cover and cropping practices from 1987 to 2019 using the Landsat archive at 30 m spatial resolution. These crop cover maps served as a consistent input for estimating crop water consumption using satellite-based estimates of actual evapotranspiration, again derived from Landsat imagery, and computed with the Operational Simplified Surface Energy Balance (SSEBop) model, a water–energy balance approach well suited for dryland environments. A decomposition approach was applied to disentangle the relative contributions of climate change and land-use change to observed evapotranspiration dynamics.

Results show that total crop water consumption increased by about 10% over the study period, while average water use per unit area rose by 18%. Rising temperatures and increasing atmospheric evaporative demand alone would have pushed up water consumption by 21%. In contrast, shifts toward less water-intensive cropping practices, most notably from water-intensive summer cotton to winter wheat, offset only around 3% of this increase. Climate-driven effects intensified after the early 2000s and were strongest in downstream areas, where water stress, salinity, and ageing irrigation infrastructure limit adaptive capacity.

The findings demonstrate that, in irrigated dryland catchments, land-use change and cropping adjustments alone cannot counteract the accelerating impacts of climate change on evapotranspiration. All evapotranspiration and land-use datasets generated in this study are openly accessible, supporting transparency, reproducibility, and future research in data-scarce dryland regions. Our results underscore the need to combine improvements in water-use efficiency with climate mitigation and basin-scale management to strengthen hydrological resilience under continued warming.