Author(s):
Cai, J.B. 
; Liu, Y. ; Xu, D. ; Paredes, P. ; Pereira, L.S.
Date: 2009
Persistent ID: http://hdl.handle.net/10400.5/4862
Origin: Repositório da UTL
Subject(s): soil water balance; wheat; evapotranspiration
Description
Abstract. Aiming at developing real time water balance
modelling for irrigation scheduling, this study assesses the
accuracy of using the reference evapotranspiration (ETo) estimated
from daily weather forecast messages (ETo,WF) as
model input. A previous study applied to eight locations in
China (Cai et al., 2007) has shown the feasibility for estimating
ETo,WF with the FAO Penman-Monteith equation using
daily forecasts of maximum and minimum temperature,
cloudiness and wind speed. In this study, the global radiation
is estimated from the difference between the forecasted maximum
and minimum temperatures, the actual vapour pressure
is estimated from the forecasted minimum temperature
and the wind speed is obtained from converting the common
wind scales into wind speed. The present application
refers to a location in the North China Plain, Daxing, for the
wheat crop seasons of 2005–2006 and 2006–2007. Results
comparing ETo,WF with ETo computed with observed data
(ETo,obs) have shown favourable goodness of fitting indicators
and a RMSE of 0.77mmd−1. ETo was underestimated
in the first year and overestimated in the second. The water
balance model ISAREG was calibrated with data from
four treatments for the first season and validated with data of
five treatments in the second season using observed weather
data. The calibrated crop parameters were used in the simulations
of the same treatments using ETo,WF as model input.
Errors in predicting the soil water content are small, 0.010
and 0.012m3 m−3, respectively for the first and second year.
Other indicators also confirm the goodness of model predictions.
It could be concluded that using ETo computed from
daily weather forecast messages provides for accurate model
predictions and to use an irrigation scheduling model in real
time
