ABSTRACT The existence of fewer gauging sites along with sparse network of rain gauges make the monitoring of floods difficult, especially over regions characterized with hydrologic heterogeneity. The availability of observations from satellite sensors makes it possible to study hydrological behaviour of such under-observed river basins. In this study, we explore the utility of GRACE derived terrestrial water storage estimates to monitor the flood events of varying magnitudes over the river basins on Indian Peninsula, that is known to be a region of high heterogeneity. We use terrestrial water storage estimates from Gravity Recovery and Climate Experiment (GRACE) satellite mission, rainfall and temperature data from India Meteorological Department (IMD), discharge data from Central Water Commission (CWC) and groundwater level data from Central Ground Water Board (CGWB) to evaluate and compare the variability of flood potential of six major river basins, which show unique hydrological characteristics. The flood potential is evaluated for these major basins in Peninsular India using Reager’s Flood Potential Index (FPI) and the skill of FPI is assessed over these basins, for the period from 2003 to 2016. Significant variations are observed in the terrestrial water storage and FPI estimates of these basins, which reflects the diverse hydrological behaviour of the basins. Mahanadi basin shows extremely high positive FPI values, while Cauvery basin shows extremely high negative values, thereby confirming their respective flood and drought prone characteristics. The ability of FPI is established especially for basins with discharge values higher than 2000 m3 s–1. Moreover, good accuracy (> 90%) is observed over Mahanadi, Godavari and Narmada basins that are exposed with frequent mild, moderate and severe floods, using the threshold values of FPI. Among all the basins, Mahanadi basin shows high threshold FPI values of 0.40, 0.32 and 0.27 for severe, moderate and mild floods respectively. Godavari and Narmada basins have relatively lesser thresholds. The FPI values corresponding to severe, moderate and mild floods for Godavari basin are 0.25, 0.14 and 0.09, while those for Narmada basin are 0.25, 0.11 and 0.04. We hence, conclude that the index has the ability to monitor different levels of floods, over basins exhibiting diverse hydrological characteristics. These observations establish that GRACE derived terrestrial water storage anomaly (TWSA) can be used for flood monitoring applications, when discharge data is rarely available and the incorporation of terrestrial water storage estimates with the rainfall data in hydrological modelling may greatly help in assessing hydrological extremes.

中文翻译：

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GRACE 在评估印度半岛河流域洪水潜力方面的潜力

摘要 测量站点较少，雨量计网络稀疏，使得洪水监测变得困难，尤其是在具有水文异质性特征的地区。卫星传感器的观测数据的可用性使得研究此类观测不足的河流流域的水文行为成为可能。在这项研究中，我们探索了 GRACE 推导出的陆地储水量估计值的效用，以监测印度半岛河流流域上不同规模的洪水事件，众所周知，印度半岛是一个高度异质性的区域。我们使用来自重力恢复和气候实验 (GRACE) 卫星任务的陆地储水量估算值、来自印度气象部门 (IMD) 的降雨和温度数据，中央水务委员会（CWC）的排放数据和中央地下水局（CGWB）的地下水位数据，以评估和比较六大流域洪水潜力的变异性，表现出独特的水文特征。使用 Reager 洪水潜力指数 (FPI) 评估了印度半岛这些主要流域的洪水潜力，并评估了这些流域 2003 年至 2016 年期间 FPI 的技能。 观察到陆地蓄水量和 FPI 的显着变化这些流域的估计值，反映了流域的不同水文行为。Mahanadi 盆地显示出极高的正 FPI 值，而 Cauvery 盆地显示出极高的负值，从而证实了它们各自的洪水和干旱易发特征。FPI 的能力尤其适用于流量值高于 2000 m3 s-1 的流域。此外，使用 FPI 的阈值，在频繁遭受轻度、中度和重度洪水的 Mahanadi、Godavari 和 Narmada 盆地中观察到了良好的准确度 (> 90%)。在所有流域中，马哈纳迪流域的重度、中度和轻度洪水的高阈值 FPI 值分别为 0.40、0.32 和 0.27。Godavari 和 Narmada 盆地的阈值相对较小。Godavari 流域严重、中度和轻度洪水对应的 FPI 值为 0.25、0.14 和 0.09，而纳尔马达流域的 FPI 值为 0.25、0.11 和 0.04。因此，我们得出结论，该指数能够监测表现出不同水文特征的流域的不同洪水级别。