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February 7, 2025

Decoupling of water storage and rainfall in drylands highlights human impact

The attribution of surface water storage changes to precipitation, watershed hydrology and human water management. Credit: Zhao Gang
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The attribution of surface water storage changes to precipitation, watershed hydrology and human water management. Credit: Zhao Gang

Drylands, characterized by an aridity index (AI) below 0.65, cover about 45% of the Earth's land and support more than 3 billion people. Severe water scarcity in these areas poses significant risks to human well-being and ecosystems. However, our understanding of long-term changes in surface water storage and their causes is limited due to insufficient high-quality data with adequate 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 changes for 105,400 lakes and reservoirs in global from 1985 to 2020. Their study was in Nature Water.

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. Although natural lakes and old reservoirs did not exhibit significant overall trends, they accounted for the water storage dynamics in 91% of the across arid regions.

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

This study provides observational data on long-term surface water storage changes in global drylands and attributes 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, first author of the study.

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 take into account climate, basin characteristics, and human activities to more accurately assess water availability.

More information: Gang Zhao et al, Decoupling of surface water storage from precipitation in global drylands due to anthropogenic activity, Nature Water (2025).

Journal information: Nature Water

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Surface water storage in global drylands has increased by 2.20 km3 per year, mainly due to new reservoir construction. This change is largely driven by human activities, such as climate warming and water management, rather than precipitation. The findings highlight a decoupling between water storage and rainfall, suggesting that water resource management should consider climate, basin characteristics, and human influence for accurate assessments.

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