The lack of in-situ hydrological observations, especially in remote and developing areas, is one of the main challenges of drought monitoring. This paper proposes a novel drought index, the Standardized River Stage Index (SRSI), based on data retrieved from satellite altimetry missions. The novelties of the SRSI are that it can quantitatively monitor drought of river water deficits at multiple timescales and that it does not require in-situ observations. The Mekong River is used as the case study to demonstrate and validate the SRSI calculated from the multi-mission satellite altimetry data (Envisat and Jason-2/3). The log-logistic distribution is best fitted for SRSI calculation for the highest goodness-of-fit for river stages for the Mekong River. The comparison with the Standardized Streamflow Index (SSI) from the in-situ discharge observations shows that the SRSI can reasonably capture the drought of river water deficit. It is effective in identifying the timing and intensity of severe drought events, such as the 2019 Thailand drought. The SRSI is also compared with the Standardized Precipitation Evapotranspiration Index and the GRACE Drought Index in revealing drought features such that the river water deficit of Mekong River has time lags of 2 to 3 months for precipitation deficits and water storage deficits. Hence, the SRSI is more suitable for monitoring drought of river water deficit, because it directly links to the streamflow via physical stage-discharge relationship. Overall, the SRSI provides an effective indicator of drought of river water deficit when in-situ observations are unavailable. It can serve in the real-time drought early warning in remote and developing areas.

缺乏现场水文观测，特别是在偏远和发展中地区，是干旱监测的主要挑战之一。本文基于从卫星测高任务中检索到的数据，提出了一种新的干旱指数，即标准化河流水位指数 (SRSI)。SRSI 的新颖之处在于它可以在多个时间尺度上定量监测河流缺水的干旱，并且不需要现场观测。湄公河被用作案例研究，以演示和验证根据多任务卫星测高数据（Envisat 和 Jason-2/3）计算的 SRSI。对数逻辑分布最适合 SRSI 计算，以获得湄公河河流水位的最高拟合优度。与原位流量观测的标准化径流指数（SSI）的比较表明，SRSI可以合理地反映河流缺水的干旱情况。它可以有效地确定严重干旱事件的时间和强度，例如 2019 年泰国干旱。SRSI 还与标准化降水蒸散指数和 GRACE 干旱指数进行了比较，以揭示干旱特征，例如湄公河的河流缺水有 2 到 3 个月的降水亏缺和蓄水亏缺的时滞。因此，SRSI 更适合监测河流缺水的干旱，因为它通过物理阶段-流量关系直接链接到河流流量。全面的，当无法进行现场观测时，SRSI 可提供河流缺水干旱的有效指标。可用于边远地区和发展中地区的实时干旱预警。