Sawant et al. (2025) Estimation of Reference Evapotranspiration Using Empirical Methods and Cropwat 8.0 Model for the Sangli District Maharashtra India

Identification

• Journal: PLANT ARCHIVES
• Year: 2025
• Date: 2025-09-10
• Authors: Mrunal P. Sawant, Komal G Rokade, Prasanna B. Khaire
• DOI: 10.51470/plantarchives.2026.v26.supplement-1.138

Research Groups

• Department of Soil & Water Conservation Engineering, Dr. ASCAET, Mahatma Phule Krishi Vidyapeeth, Rahuri, District – Ahmednagar, Maharashtra, India

Short Summary

This study estimated reference evapotranspiration (ET₀) for the Sangli district, Maharashtra, India, by comparing nine empirical methods against the FAO Penman-Monteith equation implemented in CROPWAT 8.0, identifying the most accurate methods for regional irrigation planning. The Schendel method demonstrated the highest accuracy in matching Penman-Monteith estimates, followed by the Hargreaves-Samani method.

Objective

• To estimate reference evapotranspiration (ET₀) for the Sangli district, Maharashtra, India, using nine empirical methods and the CROPWAT 8.0 model.
• To compare the performance of these empirical methods against the FAO Penman-Monteith equation (used by CROPWAT 8.0) to determine the most suitable approach for the region's specific agro-climatic conditions.

Study Configuration

• Spatial Scale: Sangli district, Maharashtra, India (area: 8601.5 km²). Located between 16°45' and 17°33' N latitude and 73°41' and 75°41' E longitude.
• Temporal Scale: Historical meteorological data, analyzed on a monthly basis. The specific period of historical data is not explicitly stated, but it covers a sufficient duration to derive average monthly values.

Methodology and Data

• Models used:
  • CROPWAT 8.0 model (utilizing the FAO Penman-Monteith equation as the standard reference).
  • Nine empirical methods: Hargreaves-Samani, Hargreaves-Samani Droogers and Allen, Schendel, Global Radiation, Temperature Radiation, Rs-Radiation, Stephens-Stewart, McGuinness and Bordne, and Abtew.
• Data sources:
  • India Meteorological Department (IMD).
  • Key meteorological parameters: average minimum and maximum air temperatures (degrees Celsius), average relative humidity (percent), wind speed (kilometers per day, converted to meters per second for SI), sunshine duration (hours), average solar radiation (watts per square meter or megajoules per square meter per day), and precipitation (millimeters).
  • Average air temperature: 26–27 °C (max 35–38 °C, min 10–12 °C).
  • Average relative humidity: 50–80 %.
  • Wind speed: 6–10 km/h (1.67–2.78 m/s).
  • Annual precipitation: 500–700 mm.

Main Results

• All nine empirical methods provided reasonable ET₀ estimates, but with significant variations compared to the Penman-Monteith method.
• The Schendel method demonstrated the highest accuracy in matching Penman-Monteith estimates, with a regression slope of 1.5388 and an intercept of -0.5799.
• The Hargreaves-Samani method also performed well, yielding a regression slope of 0.8663 and an intercept of -0.214.
• The Abtew method exhibited the highest regression coefficient (R²) value of 0.3377, followed by Schendel (0.329) and Hargreaves-Samani Droogers and Allen (0.304).
• The McGuinness and Bordne method showed the lowest R² value (0.1126), indicating weaker predictive performance.
• The study confirmed that empirical methods can serve as viable alternatives for ET₀ estimation when complete meteorological data required for the Penman-Monteith equation are unavailable.
• The CROPWAT 8.0 model was found to be effective for precise crop water requirement estimation.

Contributions

• Provided a comprehensive comparative analysis of nine empirical reference evapotranspiration (ET₀) estimation methods against the FAO Penman-Monteith standard for the specific agro-climatic conditions of the Sangli district, Maharashtra, India.
• Identified the most suitable empirical methods (Schendel and Hargreaves-Samani) for the region, offering practical alternatives for ET₀ estimation in data-scarce environments.
• Emphasized the critical importance of selecting regionally appropriate ET₀ estimation methods for accurate irrigation planning and sustainable water resource management in water-stressed agricultural areas.

Funding

No specific funding projects, programs, or reference codes were mentioned in the provided paper text.

Citation

@article{Sawant2025Estimation,
  author = {Sawant, Mrunal P. and Rokade, Komal G and Khaire, Prasanna B.},
  title = {Estimation of Reference Evapotranspiration Using Empirical Methods and Cropwat 8.0 Model for the Sangli District Maharashtra India},
  journal = {PLANT ARCHIVES},
  year = {2025},
  doi = {10.51470/plantarchives.2026.v26.supplement-1.138},
  url = {https://doi.org/10.51470/plantarchives.2026.v26.supplement-1.138}
}