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<p>Drought, a multifaceted natural hazard, arises not only from extended periods of below-average precipitation, but also from anthropogenic exploitation of terrestrial water storage (TWS), and is affecting the agriculturally intensive Ganga-Brahmaputra Basin (GBB). Hence this study explores the drought scenario of GBB using a combined drought index which uses both precipitation and GRACE-derived total water storage anomaly (TWSA) as the indicators. Furthermore, the relative contribution of TWSA and precipitation anomaly is envisaged in this research to quantify the dominant contributor of drought in the basin. The results reveal a marked decline in TWSA across all sub-basins, with the Upper Ganga Basin (UGB) and Yamuna-Chambal Basin (YCB) exhibiting the sharpest declines of -2.622&#xa0;cm/year and − 2.116&#xa0;cm/year, respectively, largely driven by unsustainable groundwater extraction and climatic variability. In contrast, the Lower Ganga Basin (LGB) and Brahmaputra Basin (BB) experience slower declines in TWSA, at -0.840&#xa0;cm/year and − 1.065&#xa0;cm/year, owing to their distinct aquifer characteristics and higher precipitation levels. The Combined Climatologic Deviation Index (CCDI), used to identify the drought scenario of the basins, showed significant parts of YCB and UGB faced the most severe long-duration droughts. Relative importance analysis underscores the dominant role of TWSA in shaping drought severity, with greater influence than precipitation anomalies in UGB and YCB, while LGB and BB have much influence on precipitation. Drought propagation times representing catchment response vary significantly among basins, with UGB and YCB exhibiting rapid response to input precipitation (5–6 months), while LGB shows a slower response (6–7 months). BB, benefiting from higher rainfall, experiences a much shorter propagation time (2–3 months). This study concludes since TWSA is the dominant contributor in drought manifestations for UGB and YCB, their rapid decline has plunged the basin into long term droughts.</p>

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Combined hydro-meteorological drought assessment of Ganga-Brahmaputra Basin: insights of the control of total water storage anomaly in drought occurrence

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  • 发表日期：

    2026年3月11日

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  • Subimal Nandi,
  • Suvro Aon,
  • Shoubhik Sen,
  • Sujata Biswas

摘要

Drought, a multifaceted natural hazard, arises not only from extended periods of below-average precipitation, but also from anthropogenic exploitation of terrestrial water storage (TWS), and is affecting the agriculturally intensive Ganga-Brahmaputra Basin (GBB). Hence this study explores the drought scenario of GBB using a combined drought index which uses both precipitation and GRACE-derived total water storage anomaly (TWSA) as the indicators. Furthermore, the relative contribution of TWSA and precipitation anomaly is envisaged in this research to quantify the dominant contributor of drought in the basin. The results reveal a marked decline in TWSA across all sub-basins, with the Upper Ganga Basin (UGB) and Yamuna-Chambal Basin (YCB) exhibiting the sharpest declines of -2.622 cm/year and − 2.116 cm/year, respectively, largely driven by unsustainable groundwater extraction and climatic variability. In contrast, the Lower Ganga Basin (LGB) and Brahmaputra Basin (BB) experience slower declines in TWSA, at -0.840 cm/year and − 1.065 cm/year, owing to their distinct aquifer characteristics and higher precipitation levels. The Combined Climatologic Deviation Index (CCDI), used to identify the drought scenario of the basins, showed significant parts of YCB and UGB faced the most severe long-duration droughts. Relative importance analysis underscores the dominant role of TWSA in shaping drought severity, with greater influence than precipitation anomalies in UGB and YCB, while LGB and BB have much influence on precipitation. Drought propagation times representing catchment response vary significantly among basins, with UGB and YCB exhibiting rapid response to input precipitation (5–6 months), while LGB shows a slower response (6–7 months). BB, benefiting from higher rainfall, experiences a much shorter propagation time (2–3 months). This study concludes since TWSA is the dominant contributor in drought manifestations for UGB and YCB, their rapid decline has plunged the basin into long term droughts.