A comparison between Swat and a distributed hydrologic and water quality model for the Camastra basin (Southern Italy)

Over the last twenty years, the contribution of diffuse sources to the surface waters pollution has increased, despite several decades of research on agricultural management practices to minimize water pollution. The main purpose of this research is to make a comparison between Swat and a distributed hydrologic rainfall-runoff model applied to the Camastra river basin. The hydrologic and water quality distributed model, based upon a spatial discretization of the territory into elementary square cells, schematises the main hydrological processes of degradation and transport of nutrients, performed on a control volume build on the single cell. For the evaluation of the local generation of surface, sub-surface and groundwater run-off has been used an evolution of the WetSpa (Yongbo and De Smedt, 2000) distributed hydrologic model, coupled with a procedure for the nitrogen alteration and transport assessment. Preprocessing and following visualization of outputs has been carried out using GIS software. The study area is the 350 km2 of the Camastra lake basin (Southern Italy). The water quality data used for the model calibration have been collected in a monitoring campaign performed by the ARPAB (Basilicata Region Environmental Protection Agency). Two simulations over the identical time period have been conducted in the same region by using the developed model and the SWAT model The comparison shows the difficult of SWAT to give good simulations of the stream flows and reservoirs balance, that make complicated the use of the SWAT model to modelling water balance and water quality in the study region.