Integrated modelling of the influence of urbanizationand climate change on river water quality

Climate change is one of the most important drivers modifying the hydrologic and environmentalcharacteristics of natural catchments. When dealing with the quality of natural waters, these factorsshould be weighed up against anthropogenic factors that may increase or decrease the effect ofclimatic modifications. However, a detailed and more generalised analysis of such environmentalimpacts at a relatively small scale is currently lack. This paper aims to fill this gap. The use of aholistic approach is also required by the EU Water Framework Directive, which prescribes integratedanalysis for river basin management in order to meet environmental and ecological objectives. In orderto 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 wasused 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 atvarious reaches is analysed by ‘locating’ a new development on an urban catchment. River waterquality is used as a feedback mechanism to constrain the scale of the new development withindifferent thresholds in order to ensure compliance with water quality standards. The analysis has beenapplied to an experimental natural catchment: the Nocella catchment, which is a partially urbanisednatural catchment located in the north-western part of Sicily, Italy.