Assessment of Reference Evapotranspiration Estimation Models

Reference evapotranspiration (ETo) is an important factor in estimating crop water requirement, water resource management and designing irrigation scheduling. This study matches the outputs of open pans and Blaney Criddle (BC) to CROPWAT irrigation simulation software using 20-year daily weather data of Auchi and its environs were acquired from the Nigeria Meteorological Station (NMET) as baseline weather dataset. Thus, the baseline weather data was reproduced using a general circulation model for data re-analysis. The accuracy of each model was evaluated using various statistical metrics. ETo estimated from the four models were compared with the CROPWAT model, an irrigation software program used for solar radiation (RS), reference evapotranspiration (ETo) and crop water requirement (CWR) calculations. Validation outputs have the correlation values (R2) of 0.587, 0.536, 0.511 and 0.513 for EToBC-ETo CROPWAT, EToBT-EToCROPWAT, ETo AUS-ETo CROPWAT, and EToUS-EToCROPWAT respectively. This result indicates a marginal good fit between the estimated Reference evapotranspiration (ETo) from each model and CROPWAT irrigation software. However, there were discrepancies between the simulated and computed reference evapotranspiration (ETo) for the model with Blaney Criddle and Australia pan having correlation (R2)) and bias value (AB) of 0.223; 0.241 and 2.30; 2.00 respectively. In conclusion, all the selected reference evapotranspiration (ETo) estimating models have strong capabilities of providing accurate outcome be useful for water resources and hydrological modeling.