G. Rana et al., A MODEL FOR PREDICTING ACTUAL EVAPOTRANSPIRATION UNDER SOIL-WATER STRESS IN A MEDITERRANEAN REGION, Theoretical and applied climatology, 56(1-2), 1997, pp. 45-55
In this paper a model for estimating actual evapotranspiration is deve
loped and tested for field crops (grain sorghum and sunflower) maintai
ned under water stress conditions. The model is based on the Penman-Mo
nteith formulation of ET in which canopy resistance (r(c)) is modeled
with respect to the crop water status and local climatological conditi
ons. The model was previously tested on reference grass; in this last
case no reference was made to soil water conditions and r(c) was model
ed only as a function of climatological parameters. Here r(c) is expre
ssed as a function of available energy, vapour pressure deficit, aerod
ynamic resistance and crop water status by means of predawn leaf water
potential. Results, obtained with various crop water stress intensiti
es, show that, on a daily scale, calculated ET is 98% and 95% of the m
easured ET for sorghum and sunflower respectively. The correlation bet
ween daily calculated and measured ET is very high (r(2) = 0.95 for so
rghum and r(2) = 0.98 for sunflower). On an hourly scale, the model wo
rks very well when the crops were not stressed and during the senescen
ce stage. In case of weak and strong stress the model has to be used w
ith some precautions.