The Himalayas are critical for supplying water for ∼2 billion people who live downstream, and available water is highly sensitive to climate change. The role of the groundwater system in sustaining the northern Himalayan rivers remains unknown, and this compromises Asia's future water sustainability. Here, we quantify the spatiotemporal contribution of groundwater to river flows in the Yarlung Zangbo Basin (upper reaches of Brahmaputra). Our results show that the groundwater recharge represents ∼23% of mean annual precipitation, translating into ∼30 km³/yr of baseflow, which contributes ∼55% of the total river discharge in the upstream reaches to ∼27% in the downstream reaches. The percentage of groundwater contribution is inversely related to topographic steepness and total precipitation, with the steepest topography and highest precipitation in the eastern Himalayas. This study fills a knowledge gap on groundwater in the Himalayas and is a foundation for projecting water changes under climatic warming.

中文翻译：

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地下水在维持喜马拉雅北部河流中的作用

喜马拉雅山对于向约20亿下游人供水是至关重要的，而且可用水对气候变化高度敏感。地下水系统在维持喜马拉雅北部河流中的作用仍然未知，这损害了亚洲未来的水可持续性。在这里，我们量化了雅鲁藏布江盆地（雅鲁藏布江上游）地下水对河水流动的时空贡献。我们的结果表明，地下水补给量约占年平均降水量的23％，转化为约30 km ³/ yr的基流，约占上游河道总流量的55％至下游河道的〜27％。地下水贡献的百分比与地形的陡度和总降水量成反比，喜马拉雅东部的地形最陡，降水最多。这项研究填补了喜马拉雅山脉地下水的知识空白，为预测气候变暖下的水变化奠定了基础。