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Abstract

A study published by Benfratello in 1961 proposed a practical method for calculating irrigation deficit in agricultural regions based on environmental forcings and field capacity. Because of its straightforward nature and minimal input requirements, Benfratello's method can be regarded to as an effective tool for evaluating the impacts of anthropogenic, climatic, and land use changes on soil water balance and irrigation deficit. This approach is effective both for climatic and real-time assessment of the irrigation deficit and it has been until now widely applied in semiarid areas of southern Italy. In previous works, we presented a GIS-based application of Benfratello’s method to assess the monthly irrigation deficit and its interannual variability in the Capitanata agricultural district (Apulia region, southern Italy).In this contribution, we present a GIS-based application of a later classical development of Benfratello’s method, given by Melisenda (1964), in order to define a water-availability index to characterize the climatic proneness to water scarcity. This index is the ratio between the difference of precipitation and maximum evapotranspiration in the wet and dry seasons respectively and it can be used to straightforwardly estimate the annual water deficit. As a result, we present the map of Melisenda’s Index and of the water deficit for the Capitanata region in comparison with other aridity indices as the ones proposed by De Martonne and Budyko, in present and future climatic conditions according to IPCC scenarios RCP4.5 and RCP8.5.