Drylands (aridity index AI < 0.65) cover approximately 45% of the global land area and support over 3 billion people, making them a critical component of the Earth system. Severe water scarcity in these regions poses significant threats to human well-being and ecosystem health. Despite their high sensitivity to water scarcity, our understanding of long-term changes in surface water storage and their driving mechanisms remains limited. This knowledge gap is primarily due to the lack of high-quality data with sufficient spatiotemporal coverage and resolution.

To address these critical issues, a research team from the Institute of Geographic Sciences and Natural Resources Research (IGSNRR) of the Chinese Academy of Sciences (CAS) and their collaborators utilized multi-source remote sensing data to construct a monthly time series of water storage changes for 105,400 lakes and reservoirs in global arid regions from 1985 to 2020.

The results revealed that surface water storage in global drylands increased by 2.20 cubic kilometers per year, primarily driven by the construction of new reservoirs. While natural lakes and old reservoirs did not exhibit significant overall trends, they accounted for the surface water storage dynamics in 91% of the basins across arid regions.

Further analysis indicated that the long-term changes in the storage of these water bodies were predominantly associated with human activities, including anthropogenic climate warming and water resource management, rather than previously assumed precipitation changes.

“The study's primary contribution lies in providing observational data on long-term surface water storage changes in global drylands and attributing these changes to human activities. The study highlights a decoupling between surface water storage and precipitation in arid regions, posing new challenges to the sustainability of societies and ecosystems,” said Prof. ZHAO Gang.

“This decoupling underscores the role of global warming and human activities in driving long-term hydrological changes. Consequently, water resource management based solely on precipitation may overestimate or underestimate water availability. Instead, integrated water resource planning should consider climate, basin characteristics, and human activities to more accurately assess water availability,” he added.

Reference：

Zhao, G., Gao, H., Li, Y. et al. Decoupling of surface water storage from precipitation in global drylands due to anthropogenic activity. Nature Water 3, 80–88 (2025). https://doi.org/10.1038/s44221-024-00367-7.

The attribution of surface water storage changes to precipitation, watershed hydrology and human water management (Image by ZHAO Gang)