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

ABSTRACT

Short-term forecasting of daily crop evapotranspiration (ET_c) is essential for real-time irrigation management. This study proposed a methodology to forecast short-term daily ET_c using the ‘K_c-ET_o’ approach and public weather forecasts. Daily reference evapotranspiration (ET_o) forecasts were obtained using a locally calibrated version of the Hargreaves-Samani (HS) model and temperature forecasts, while the crop coefficient (K_c) was estimated from observed daily ET_o and ET_c. The methodology was evaluated by comparing the daily ET_c forecasts with measured ET_c 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 K_c estion, temperature forecasts and HS model that does not consider wind speed and humidity, and.the largesourceof error is K_c determination, which suggested that care should be taken when forecasting ET_c with estimated K_c values in the study area.

KEYWORDS:

• Crop water requirement
• irrigation forecasting
• irrigation scheduling
• crop coefficient
• FAO56 Penman Monteith method

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [91647204];Ministry of Science and Technology of China, National Key Research & Development (R&D) Plan [2017YFC0403206];