Recent droughts have severely threatened water security in many regions worldwide. Reservoirs, designed to combat droughts and secure water supply partially, are reported failing to fill up to the total capacity due to severe droughts. How bad is climate affecting reservoir filling up on a global scale? This issue has not been studied. We present a big picture of reservoirs in crisis using satellite altimetry. Thanks to the unique characteristics of CryoSat-2, 525 reservoirs worldwide were investigated during 2010–2022. Results show that most reservoirs (93%) are found not fully filled up at least once. About 21% of reservoirs, which are mainly located in the Southern Hemisphere, show a significant decline in water levels. Moreover, about 20% of reservoirs with larger level fluctuations (>3 m) are located in less developed economies, indicating informed operation rules are needed. Further analyses indicate reservoirs are largely affected by extreme climate events, such as ENSO.

中文翻译：

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气候变化中的水库填满问题：来自 CryoSat-2 高度测量的见解

最近的干旱严重威胁了全球许多地区的水安全。据报道，旨在抗旱和部分保障供水的水库由于严重干旱而未能达到总容量。气候对全球范围内水库蓄水的影响有多严重？这个问题还没有研究过。我们利用卫星测高技术展示了处于危机中的水库的全貌。由于 CryoSat-2 的独特特性，2010 年至 2022 年期间对全球 525 个储层进行了调查。结果显示，大多数水库（93%）至少有一次没有完全填满。约21%的水库水位显着下降，主要位于南半球。此外，约 20% 水位波动较大（>3 m）的水库位于欠发达经济体，这表明需要明智的运行规则。进一步的分析表明，水库在很大程度上受到极端气候事件的影响，例如ENSO。