Widespread Decline in Global Lake Water Storage Revealed

The amount of water stored in more than half of the largest lakes and reservoirs worldwide is declining, according to a new study. This drying is largely attributable to a warming climate and increased human impacts. The findings underscore the importance of accounting for these impacts in future surface water resources management strategies. Although they cover roughly 3% of the global land area, lakes hold 87% of Earth's liquid surface fresh water. These features also provide essential ecosystem services and are key components in global biogeochemical processes. Many of these benefits are modulated by lake water storage (LWS), which can naturally fluctuate in response to local precipitation. However, direct human activities, like damming and water consumption, as well as ongoing climate change, increasingly threaten these crucial water resources. While it's well known that the amount of water stored in some of the world's largest lakes and human-managed reservoirs has progressively declined over recent years, the drivers behind these losses – particularly those related to human impacts and climate change – are poorly understood at the global scale. Combining global satellite measurements with climate and hydrologic models, Fangfang Yao et al. built a global dataset of decadal-scale trends in LWS from 1992 to 2020 for nearly 2,000 of the world's largest lakes and reservoirs. Through their analysis, Yao et al. revealed a widespread decline in global LWS; according to the findings, 53% of these water bodies have experienced significant water losses over the last 28 years at a rate of roughly 22 gigatonnes (Gt) per year. The authors attribute much of the net volume loss in natural lakes to climate warming, increased evapotranspiration, and human water consumption, while sedimentation is to blame for storage loss in drying reservoirs. Yao et al. argue that the findings underscore the need for incorporating climate change and sedimentation impacts into sustainable water resources management. "Yao et al. estimated that nearly one-quarter of the world's population lives in a basin with a large, drying lake," writes Sarah Cooley in a related Perspective. "Considering the importance of these lakes for ecosystem services, water supply, irrigation, and/or hydropower, the potential consequences of lake drying are both locally and globally important."