Prediction of Evapotranspiration With WEAP Model

ABSTRACT

With increase in population, there are challenges of utilizing the available natural resources effectively. Accurate estimation of crop water requirements depends on the precise determination of evapotranspiration. This study introduces an approach for predicting evapotranspiration using the Water Evaluation and Planning (WEAP) model. Although the FAO‐56 Penman–Monteith (FPM‐56) equation requires comprehensive meteorological data, WEAP operates with a simplified set of inputs like minimum and maximum temperatures, relative humidity, wind speed, solar radiation, and rainfall. The proposed method was applied to Nashik, India. The performance of the WEAP model was evaluated by comparing its results with those obtained from the FPM‐56 equation. Statistical indicators used for assessment included the coefficient of determination ( R ² ), root mean square error (RMSE), sum of square error (SSE), and mean absolute error (MAE), which were found to be 0.7874, 0.4009, 2.14, and 0.015, respectively. Additionally, monthly average ET ₀ values over the past 30 years, as estimated by WEAP, FPM‐56, and CROPWAT. WEAP and FPM‐56 showed comparable performance, whereas CROPWAT consistently overestimated ET ₀ . These findings indicate that FPM‐56 requires detailed meteorological parameters for prediction of evapotranspiration, whereas WEAP provides strong predictive capability for estimating future evapotranspiration with minimum data requirement and can serve as a reliable tool for water resource planning under climate change scenarios.