FOLIA GEOGRAPHICA SERIES GEOGRAPHICA-PHYSICA Vol. XL 2009: 45–56 ISSN 0071-6715 DEVELOPMENT OF AN ALTERNATIVE SCENARIO IN A SMALL MEDITERRANEAN BASIN USING THE RAINFALL-RUNOFF SWAT MODEL Anna Maria De Girolamo 1 , Antonio Lo Porto 1 , Gerardina Santese 1,2 1 Water Research Institute – IRSA, Italian National Research Council – CNR, Bari, Italy annamaria.degirolamo@ba.irsa.cnr.it 2 University of Tuscia, Viterbo, Italy In recent decades, intensive agriculture and river engineering in the Candelaro Basin (Italy) have modified its natural character and hydrological processes. Many floods and landslide events have been recorded since 1919. his has had an enormous impact on crops, and buildings. Such events have also claimed human lives. In this paper, a management strategy based on the renaturalization of the main river is proposed. his strategy is in line with agricultural conservation practices and is aimed at mitigating the effects of extreme rainfall events and stabilizing the soil structure. he SWAT model was used to calculate surface runoff on a basin scale. Following model calibration and validation, a new scenario was simulated to analyze the effects of different management strategies on peak discharge reduction. Key words: SWAT model, rainfall-runoff modelling, alternative scenario 1. INTRODUCTION he hydrological response of a basin is a combination of several factors. B. Ambroise (1999) points out that climate forcing, background hydrological conditions and soil hydrological properties, in addition to topography, morphology, and land use, determine the active processes in a basin, as well as the intensity of, and interactions between, these factors. he resulting combination of hydrological processes generates a response that is characteristic both of the basin and of every rainfall event. he transformation of rainfall into runoff is a complex non-linear process which varies over time and space (Singh 1988). In recent decades, various models ranging from linear to non-linear, lumped to distributed, have been developed to describe the transformation of rainfall hyetographs to discharge hydrographs. he nature of a basin (size, location, slope, etc.) influences the choice of modelling approach. Human activity such as land management practices, the creation of impervious surfaces, the drilling of water wells, dam construction, and the channelization