Short-term forecasting of daily crop evapotranspiration using the ‘Kc-ETo’ approach and public weather forecasts

Abstract

ABSTRACTShort-term forecasting of daily crop evapotranspiration (ETc) is essential for real-time irrigation management. This study proposed a methodology to forecast short-term daily ETc using the ‘Kc-ETo’ approach and public weather forecasts. Daily reference evapotranspiration (ETo) forecasts were obtained using a locally calibrated version of the Hargreaves-Samani (HS) model and temperature forecasts, while the crop coefficient (Kc) was estimated from observed daily ETo and ETc. The methodology was evaluated by comparing the daily ETc forecasts with measured ETc values from a field irrigation experiment during 2012–2014 in Yongkang Irrigation Experimental Station, China. The overall average of the statistical indices was in the range of 0.96–1.27 mm d−1 for the mean absolute error (MAE), 1.53–2.55 mm d−1 for the mean square error (MSE), 1.77–2.30 mm d−1 for the normalized mean square error (NMSE), 27.5–29.4% for the mean relative error (MRE), 0.71–0.44 for the correlation coefficient (R) and 0.46–0.05 for the mean square error skill score (MSESS). Sources of error werewere Kc estion, temperature forecasts and HS model that does not consider wind speed and humidity, and.the largesourceof error is Kc determination, which suggested that care should be taken when forecasting ETc with estimated Kc values in the study area.