Basin-scale water resources assessment in a sicilian basin under climate change scenarios using the conceptual model TOPDM

Climate change resulting due to the greenhouse effect is expected to have great implications for hydrological cycle and for existing surface and groundwater resources systems. The effects of climate variability and climate change have to be fully considered in current water management and planning, since water availability, quality and streamflow are very sensitive to changes in temperature and precipitation regimes. 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. The analysis of the climatic forcing trend provided the parameters needed in order to generate synthetic climate forcing series through the use of stochastic approaches. The hydrological model has been used to estimate the basin water balance components and the surface and groundwater availability 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 basins provided some important conclusions about the implications of climate change in the Southern part of Italy. Results show 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 a temperature trend as well. Therefore the climate change, occurring as precipitation amount reduction and temperature rise, could exacerbate the water resources stresses in the area of study, in which water scarcity is already an important issue for water resource management.