Application of the SWAP model to predict impact of climate change on soil water balance in a Sicilian vineyard

In Sicily, the increasing scarcity of quality water is leading to irrigation with saline water in soils having a considerable susceptibility to salinization and degradation. In this paper, water flow and solute transport in a Sicilian irrigated soil was simulated by using the SWAP model, and the simulated results compared to measured values of soil moisture and salinity. The investigation was carried out in a vineyard located in Sicily (Mazara del Vallo, Trapani) within the framework of the Project Evolution of cropping systems as affected by climate change (CLIMESCO). The soil hydraulic parameters were obtained by inverse method based on multi-step outflow experiments. The results obtained using field measurements from two soil profiles showed that SWAP provided reliable predictions of water content, θ, and of electrical conductivity of saturated extract, ECsat. The effect of climate change on soil water balance was predicted by application of SWAP under the soilcrop and irrigation management conditions currently practiced in the vineyard. Simulations were carried out with climatic data generated by the statistical downscaling process based on the global CGM HADCM3 for two IPCC scenarios (A2 and B1) and for the 2070-2100 time interval. The two mentioned IPCC scenarios (A2 and B1) were then compared to a third reference scenario (BASELINE) obtained by using the climatic data recorded from 1951 to 2004. The results indicated that the only significant effect of climate change was to shorten and to advance the crop cycle length, which decreased of 16 and 27 days respectively in B1 and A2 compared to values obtained for the BASELINE scenario. Further application of SWAP carried out simulating an advance in the irrigation starting time according to the advance in the crop cycle indicated that this could be considered a kind of adaptation strategy to be applied in the future in the vineyard to counterbalance the impact of climate change. This means that in the future farmers might be likely to anticipate the irrigation season in order to avoid anysignificant reduction in the crop productivity.