COMBINING REMOTE SENSING DATA AND A LAND SURFACE MODEL WITHIN A PHD PROJECT TO UNDERSTAND THE IMPACT OF IRRIGATION ON THE HYDROLOGICAL CYCLE

Human-induced changes on the hydrological cycle produce short-term impacts often larger than the effects of climate changes, even if they are not independent aspects. Among the anthropogenic activities that alter the natural hydrological cycle, the irrigation is the most impacting one. It is estimated that over 70% of global freshwater is used for irrigation practices (Foley et al., 2011). Despite the important implications of irrigation on water scarcity and food production, data on irrigation practices over large areas and for long periods are lacking, thus making difficult to obtain reliable information about where irrigation practices occur and how much water is used for them. This PhD project is aimed to evaluate the effects of the irrigation on the hydrological cycle over two pilot Mediterranean areas, the upper Tiber river basin in Italy and the Ebro river basin in Spain. The project is structured according to two main research lines; the first one consists in estimating the amount of water used for irrigation exploiting high resolution soil moisture products, the second one consists in evaluating the irrigation effects through simulations with SURFEX, the land surface model developed by Météo-France. In order to estimate the amount of water used for irrigation, the adapted SM2RAIN method (Brocca et al., 2018) will be applied. The capability of different satellite products to detect irrigation will be evaluated; preliminary tests carried out in the Catalan and Aragonese irrigation districts in Spain show promising results obtained with DISPATCH downscaled SMOS and SMAP surface soil moisture. Comparisons between satellite and modeled soil moisture represent an alternative method to estimate irrigation. The estimated amounts of irrigation water will be introduced in SURFEX simulations in order to represent a human-altered, real, scenario and to evaluate the effects of irrigation practices on the natural distribution of water in the study areas.