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<p>Probable Maximum Precipitation (PMP) is a critical design parameter for dams, spillways, and flood-control infrastructure, yet its response to future climate change remains uncertain across Indian river basins. This study assesses historical (1971–2022) and future (2023–2100) PMP in the Mahanadi basin using a modified Hershfield framework applied to India Meteorological Department observations and bias-corrected projections from five Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models under two Shared Socioeconomic Pathways: SSP126 and SSP585. A basin-specific composite enveloping curve was developed to refine the Hershfield frequency factor <i>K</i>, and Annual Maximum Precipitation Series (AMPS) were analysed for near- (2023–2050), mid- (2051–2075), and far-future (2076–2100) periods to represent early-, mid-, and late-century climate conditions. Results show a consistent basin-wide decline in PMP in a range of − 32 to − 65% relative to the historical baseline, even as short-duration and annual extremes intensify. Under SSP126, ensemble-mean PMP changes remain modest and spatially limited to 250–400&#xa0;mm, whereas SSP585 produces substantial amplification and expansion of high-PMP zones, with far-future ensemble values exceeding 400–450&#xa0;mm. AMPS remain stable under SSP126 but strengthen progressively under SSP585, reaching 180–220&#xa0;mm in the far future, with interannual variability exceeding 100–120&#xa0;mm. These contrasting behaviours shows declining PMP but intensifying and more volatile extremes which indicate a structural shift in rainfall dynamics under high-emission futures. The findings underscore the need to revise PMP-based design standards with climate-responsive safety margins, and the methodology offers a transferable framework for broader climate impact assessments in monsoon-dominated basins.</p>

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Modified Hershfield based estimation of probable maximum precipitation under future climate scenarios in the Mahanadi basin

  • 期刊论文

  • 发表日期：

    2026年5月13日

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  • Syed Khateeb Ahmad,
  • Md Masood Zafar Ansari,
  • Zulfequar Ahmad,
  • Pradeep Kumar Garg,
  • Pramod Kumar Sharma

摘要

Probable Maximum Precipitation (PMP) is a critical design parameter for dams, spillways, and flood-control infrastructure, yet its response to future climate change remains uncertain across Indian river basins. This study assesses historical (1971–2022) and future (2023–2100) PMP in the Mahanadi basin using a modified Hershfield framework applied to India Meteorological Department observations and bias-corrected projections from five Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models under two Shared Socioeconomic Pathways: SSP126 and SSP585. A basin-specific composite enveloping curve was developed to refine the Hershfield frequency factor K, and Annual Maximum Precipitation Series (AMPS) were analysed for near- (2023–2050), mid- (2051–2075), and far-future (2076–2100) periods to represent early-, mid-, and late-century climate conditions. Results show a consistent basin-wide decline in PMP in a range of − 32 to − 65% relative to the historical baseline, even as short-duration and annual extremes intensify. Under SSP126, ensemble-mean PMP changes remain modest and spatially limited to 250–400 mm, whereas SSP585 produces substantial amplification and expansion of high-PMP zones, with far-future ensemble values exceeding 400–450 mm. AMPS remain stable under SSP126 but strengthen progressively under SSP585, reaching 180–220 mm in the far future, with interannual variability exceeding 100–120 mm. These contrasting behaviours shows declining PMP but intensifying and more volatile extremes which indicate a structural shift in rainfall dynamics under high-emission futures. The findings underscore the need to revise PMP-based design standards with climate-responsive safety margins, and the methodology offers a transferable framework for broader climate impact assessments in monsoon-dominated basins.