Modeling diffuse pollution loading into a Mediterranean lagoon: Development and application of an integrated surface–subsurface model tool

A fast growing economy and a more demanding population in Europe is leading to increasing socio-economic pressures and large-scale land use and landscape changes are taking place. An increasing pressure is put on water resources and conflicts are arising for water distribution among different stakeholders, and degradation of water quality is exacerbating the problem. To this purpose a modeling procedure was developed to evaluate and predict the surface and subsurface water quality and quantity as affected by anthropogenic activities in the Bonello watershed (Italy). The model (Integrated Surface and Subsurface model, ISSm) is composed by the hydrological model (Swat), the groundwater models (ModFlow and Mt3Dms) and the in-stream water quality model (Qual2E). The model application gave good results in predicting, water and nutrients leaching from surface to the aquifer, groundwater dynamics, aquifer interactions with the stream system, and surface water and nutrient fluxes at the watershed outlet. It proved to be an adequate tool for scenario analysis in watershed with heavily regulated channel flow.