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<p>This study investigates the impacts of climate change on hydrometeorological components and extreme events in the Kosi River Basin, a climate-sensitive region of the Central Himalayas, under SSP2-4.5 and SSP5-8.5 scenarios. The SWAT hydrological model was applied using bias-corrected outputs from five CMIP6 global climate models. The model was calibrated and validated at Betalghat and Ranman gauging stations, yielding satisfactory performance (R² = 0.67 (0.61) and NSE = 0.62 (0.56) at monthly scale). Climate projections indicate a substantial increase in basin-averaged maximum temperature, rising from 38.4&#xa0;°C during the baseline period to 41.6&#xa0;°C (SSP2-4.5) and ~ 43.2&#xa0;°C (SSP5-8.5) by the end of the century. This warming leads to increased evapotranspiration (up to + 12.92%), reducing water availability. Despite an increase in precipitation under SSP5-8.5, groundwater recharge shows a significant decline (up to -23.76%), while surface runoff increases (+ 20.14%), indicating a shift in hydrological partitioning toward rapid surface flow. As a result, total water yield decreases (up to -6.61%), highlighting a critical paradox in basin response to climate change. The Standardized Precipitation Index (SPI) analysis indicates an increase in the frequency and intensity of drought events under future scenarios. These findings underscore the need for integrated water resource management strategies to address emerging hydro-climatic risks in Himalayan headwater basins.</p>

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Modeling climate-induced changes in hydrometeorological components and analyzing future extreme weather events using SPI in the Kosi River Basin, Uttarakhand

  • 期刊论文

  • 发表日期：

    2026年4月30日

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  • Biswajit Das,
  • Sumit Sen,
  • Sandipan Mukherjee

摘要

This study investigates the impacts of climate change on hydrometeorological components and extreme events in the Kosi River Basin, a climate-sensitive region of the Central Himalayas, under SSP2-4.5 and SSP5-8.5 scenarios. The SWAT hydrological model was applied using bias-corrected outputs from five CMIP6 global climate models. The model was calibrated and validated at Betalghat and Ranman gauging stations, yielding satisfactory performance (R² = 0.67 (0.61) and NSE = 0.62 (0.56) at monthly scale). Climate projections indicate a substantial increase in basin-averaged maximum temperature, rising from 38.4 °C during the baseline period to 41.6 °C (SSP2-4.5) and ~ 43.2 °C (SSP5-8.5) by the end of the century. This warming leads to increased evapotranspiration (up to + 12.92%), reducing water availability. Despite an increase in precipitation under SSP5-8.5, groundwater recharge shows a significant decline (up to -23.76%), while surface runoff increases (+ 20.14%), indicating a shift in hydrological partitioning toward rapid surface flow. As a result, total water yield decreases (up to -6.61%), highlighting a critical paradox in basin response to climate change. The Standardized Precipitation Index (SPI) analysis indicates an increase in the frequency and intensity of drought events under future scenarios. These findings underscore the need for integrated water resource management strategies to address emerging hydro-climatic risks in Himalayan headwater basins.