Modifications in Water Resources Availability Under Climate Changes: A Case Study in a Sicilian Basin

Climate variability due to the greenhouse effect has important implications on hydrological processes and water resources systems. Indeed, water availability, quality and streamflow are very sensitive to changes in temperature and precipitation regimes whose effects have to be fully considered in current water management and planning. International literature proposes several models, attempting to assess accurately the available water resources under stationary and changing climatic conditions at different spatial and temporal scales. In order to assess the potential impacts of climate change on surface and groundwater resources water availability in a Southern area of Italy, a conceptual hydrologic model, the TOPDM, was applied at daily scale to simulate the hydrological processes in the Belice river basin, located in Sicily and which feeds an artificial lake. The analysis of climatic forcings trend provided the parameters needed in order to generate synthetic climate forcing series through the use of the AWE-GEN, an hourly weather generator, able to reproduce the characteristics of hydro-climatic variables and their statistical properties. The hydrological model was used to estimate the basin water balance components and the surface and groundwater availability, at annual and monthly scale, in a no trend scenario, representing the current climate conditions, and in three different groups of scenarios, in which a decrease of precipitation, an increase of temperature, and a combination of these effect were reproduced. The application of TOPDM to the test basin provided some important conclusions about the implications of climate change in the Southern part of Italy. Results showed that runoff and evapotranspiration reflect variations in precipitation and in temperature; in particular the negative trend in precipitation determines a decrease in surface and groundwater resources, and this effect is intensified in the scenarios that include an increase in potential evapotraspiration as well. The consequences of changes on water supply system were also analyzed through a simple balance evaluation of the lake water reservoir, in order to assess the possible impacts on the resource managements. Results indicated an exacerbation of the water resources stresses, in which water scarcity is already an important issue for water resource management. The analysis provides useful information about the quantification of the potential effects of climate change in the area of study, in order to develop new strategies to deal with these changes.