Calibration of the AquaCrop model for winter wheat using MODIS LAI images

In semi-arid environments vegetation density and distribution is of considerable importance for the hydrological water balance. A number of hydrological models exploit Leaf Area Index (LAI) maps retrieved by remote sensing as a measure of the vegetation cover, in order to enhance the evaluation of evapotranspiration and interception losses. On the other hand, actual evapotranspiration and vegetation development can be derived through crop growth models, such as AquaCrop, developed by FAO (Food and Agricultural Organization), which allows the simulation of the canopy development of the main field crops. We used MODIS LAI images to calibrate AquaCrop according to the canopy cover development of winter wheat. With this aim we exploited an empirical relationship between LAI and canopy cover. In detail Aquacrop was calibrated with MODIS LAI maps collected between 2008 and 2011, and validated with reference to MODIS LAI maps of 2013-2014 in Rocchetta Sant'Antonio and Sant'Agata, two test sites in the Carapelle watershed, Southern Italy. Results, in terms of evaluation of canopy cover, provided improvements. For example, for Rocchetta Sant'Antonio, the statistical indexes varyfrom r=0.40, ER=0.22, RMSE = 17.28 and KGE=0.31 (using the model without calibration), to r=0.86, ER = 0.08, RMSE = 6.01 and KGE 0.85 (after calibration).