Hydrological analysis of the Upper Tiber River Basin, Central Italy: a watershed modelling approach

"Quantification of the various components of hydrological processes in a watershed remains a challenging topic as the hydrological system is altered by internal and external drivers. Watershed models have become essential tools to understand the behavior of a catchment under dynamic processes. In this study, a physically-based watershed model called Soil Water Assessment Tool (SWAT) was used to understand the hydrologic behavior of the Upper Tiber River Basin, central Italy. The model was successfully calibrated and validated using observed weather and flow data for the period of 1963–1970 and 1971–1978 respectively. Eighteen parameters were evaluated and the model showed high relative sensitivity to groundwater flow parameters than the surface flow parameters. Analysis of annual hydrological water balance was performed for the entire upper Tiber watershed and selected sub-basins. The overall behavior of the watershed was represented by three categories of parameters governing surface flow, sub-surface flow and the whole basin response. The base flow contribution has shown that 60% of the stream flow is from shallow aquifer in the sub-basins. The model evaluation statistics that evaluate the agreement between the simulated and observed streamflow at the outlet of a watershed and other three different sub-basins has shown coefficient of determination (R2) from 0.68 to 0.81 and Nash Sutcliffe Efficiency (ENS) between 0.51 and 0.8 for the validation period. The components of the hydrologic cycle showed variation for dry and wet period within the watershed for the same parameter sets. Based on the calibrated parameters the model can be used for prediction of the impact of climate and land use changes and water resources planning and management"