Integrated modelling of the influence of urbanization and climate change on river water quality

Climate change is one of the most important drivers modifying the hydrologic and environmental characteristics of natural catchments. When dealing with the quality of natural waters, these factors should be weighed up against anthropogenic factors that may increase or decrease the effect of climatic modifications. However, a detailed and more generalised analysis of such environmental impacts at a relatively small scale is currently lack. This paper aims to fill this gap. The use of a holistic approach is also required by the EU Water Framework Directive, which prescribes integrated analysis for river basin management in order to meet environmental and ecological objectives. In order to quantify the impact of anthropogenic (urbanization, increased population, higher water demand, etc.) and climatic changes on river water quality, an existing integrated urban wastewater model was used to predict water flow and quality in the sewer system, treatment plant and receiving water body. The impact on combined sewer overflow discharges, treatment plant effluent, and within the river at various reaches is analysed by ‘locating’ a new development on an urban catchment. River water quality is used as a feedback mechanism to constrain the scale of the new development within different thresholds in order to ensure compliance with water quality standards. The analysis has been applied to an experimental natural catchment: the Nocella catchment, which is a partially urbanised natural catchment located in the north-western part of Sicily, Italy.