Das et al. (2026) Projecting evapotranspiration pattern over Lower Gangetic Plains of India with special reference to pre-monsoon and post-monsoon seasons

Identification

• Journal: MAUSAM
• Year: 2026
• Date: 2026-01-01
• Authors: Abhilashaa Das, Saon Banerjee, Sarathi Saha
• DOI: 10.54302/17rh9b48

Research Groups

• Department of Agricultural Meteorology and Physics, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, India

Short Summary

This study projects future potential evapotranspiration (PET) and effective rainfall (ER) patterns over the Lower Gangetic Plain (LGP) of India using an ensemble of three Global Circulation Models (GCMs) under RCP 4.5 and RCP 8.5 scenarios for mid-century (2030-2050) and late-century (2070-2090). The findings indicate a general increase in PET and a decrease in the "ER - PET" value, signaling a rising demand for irrigation water, particularly under the high-emission RCP 8.5 scenario.

Objective

• To assess the outcomes of Hargreaves-Samani (H/S), Turc, and Makkink methods in relation to the FAO Penman-Monteith (PM) method for PET estimation.
• To observe the variation of future PET and effective rainfall for projected climatic scenarios of RCP 4.5 and RCP 8.5.
• To assess the trend of the difference between effective rainfall and PET for both scenarios to understand future irrigation requirements.

Study Configuration

• Spatial Scale: Lower Gangetic Plain (LGP) in India, specifically six stations in West Bengal (Bolpur, Burdwan, Canning, Hooghly, Howrah, Kalyani), covering an area of approximately 81,000 km².
• Temporal Scale: Baseline period (2010-2020), mid-century (2030-2050), and late-century (2070-2090).

Methodology and Data

• Models used:
  • Global Circulation Models (GCMs) ensemble: GFDL-ESM2G, HadGEM2-ES, and MIROC5.
  • Downscaling tool: MarkSim DSSAT Weather File Generator.
  • Potential Evapotranspiration (PET) estimation methods: Hargreaves-Samani (H/S), Turc, and Makkink.
  • Reference PET for validation: FAO Penman-Monteith (PM) method.
  • Effective Rainfall (ER) calculation: U.S.D.A. Soil Conservation Service (SCS) method.
• Data sources:
  • Simulated climatic parameters (temperature, solar radiation, rainfall) for future scenarios derived from the MarkSim GCM - DSSAT Weather File Generator (IPCC CMIP5 data).
  • Observed climatic data for the baseline period (2010-2020) from the meteorological observatory maintained by the All India Coordinated Research Project on Agrometeorology (AICRPAM).

Main Results

• The Makkink method demonstrated the best performance for PET estimation, showing the lowest Mean Bias Error (0.12 mm), Root Mean Square Error (0.56 mm), and Percent BIAS (4.17%) when compared to the FAO Penman-Monteith method.
• Mean daily temperature is projected to increase across the century, ranging from 1.76 °C to 1.9 °C under RCP 4.5 and 3.96 °C to 4.22 °C under RCP 8.5 by the late-century. Kalyani showed the highest mean temperature rise (almost 3.5 °C) in the late RCP 8.5 pre-monsoon scenario.
• Ensemble total PET for the LGP is projected to increase:
  • Under RCP 4.5: approximately 2.02 mm per year (mid-century) and 0.88 mm per year (late-century).
  • Under RCP 8.5: approximately 2.29 mm per year (mid-century) and 3.02 mm per year (late-century).
• Highest monthly PET values were consistently recorded in May, while January showed the lowest. Monsoon months exhibited the highest increment in PET throughout the century.
• Rainfall projections showed no uniform trend; RCP 4.5 indicated an overall increasing trend (approximately 5.5%), whereas RCP 8.5 showed a decreasing trend. Kalyani experienced the maximum decline in precipitation (22.8%) under RCP 8.5.
• The "ER - PET" value is projected to decrease over the timeframe, indicating a higher demand for irrigation water. Kalyani is simulated to exhibit the highest difference between ER and PET.
• Hydrologic extremes are anticipated under RCP 8.5, with dry periods becoming drier and wet periods becoming wetter, leading to potential flood and drought events.

Contributions

• This study is the first published research to project future evapotranspiration patterns specifically for the Lower Gangetic Plain region of India, addressing a significant knowledge gap.
• It provides valuable insights for effective crop planning and water management strategies in a data-scarce region, particularly concerning irrigation requirements under changing climatic conditions.
• The research highlights the potential for increased water scarcity and the need for adaptive measures in agricultural practices to support optimum production and ensure economic viability.

Funding

• Department of Science and Technology (DST), Government of India, through the Inspire Fellowship program.

Citation

@article{Das2026Projecting,
  author = {Das, Abhilashaa and Banerjee, Saon and Saha, Sarathi},
  title = {Projecting evapotranspiration pattern over Lower Gangetic Plains of India with special reference to pre-monsoon and post-monsoon seasons},
  journal = {MAUSAM},
  year = {2026},
  doi = {10.54302/17rh9b48},
  url = {https://doi.org/10.54302/17rh9b48}
}