Systems Analysis of Zaragoza Urban Water - SWITCH - Managing ...

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Systems Analysis of Zaragoza UWS Guillermo Penagos 1 Introduction Approximately half of the world’s population is nowadays living in cities. This percentage is increasing and so is doing their demand for natural resources as well as their pollution loads to the environment. It is reasonable to assume that if cities can become sustainable then society as a whole will follow the tendency. A key aspect on sustainability of the cities is the urban water system (UNESCO, 1999; Hellstrom et al, 2004). A sustainable urban water system should provide its services while protecting human health and the environment, with an optimum use of scarce resources over a long term perspective (ASCE, 1998). There is a strong need of developing and implementing indicators that make the concept measurable by quantifying trends towards optimization, not just of existing water and wastewater technologies but of urban societies as a whole (Larsen and Guier, 1997). Along the whole urban water cycle, important impacts on the environment take place: water is consumed, as well as energy and chemical products. On the other hand organic matter, nutrients and persistent pollutants are entering the ecosystems. A quantification of all these negative effects upon the environment is considered to be a good indicator of environmental sustainability (Larsen and Guier, 1997; Varis and Somlyody, 1997; Lundin; 1999). This study aims to analyze the environmental performance of Zaragoza Urban Water System in Spain with regard to the use of natural resources and pollutant loads to the environment. The use of natural resources is assessed with regard to water withdrawal as well as energy and chemical products consumption. Considered pollution loads are atmospheric emissions, oxygen demands to the river, nitrogen, phosphorus and heavy metals. Such analysis will serve as baseline information for further assessment of sustainable development. This research work only deals with the operational aspects of the UWS and does not include construction, upgrading and demolition of infrastructure. The present research is included within the SWITCH project framework, program 1 which aims to assess the adjustability of Urban Water Systems to global change pressures from a strategic approach based on sustainability and risk assessment. 8
Systems Analysis of Zaragoza UWS Guillermo Penagos 2 Background Sustainability of Water resources is a concept that concerns all levels of planning and management, from local to global agendas. Since cities are major water consumers, sustainability of urban water systems is increasingly becoming a major issue, receiving considerable effort from researchers and managers in both developed and developing countries (Larsen and Guier, 1997; Varis and Somlyody, 1997; Lundin; 1999). Several research projects have taken place during the last decade, mostly in European Countries. But there are also international partnerships which have included studies upon model cities in Africa and Asia. The Swedish Urban Water Project Mistra deserves special recognition since it produced numerous publications, PhD thesis and reports concerning several aspects of Urban Water Systems not just for European, but also to Asian and African cities such as Calcutta and Cairo (Hellstrom et al, 2004). Approaches similar to Mistra are taking place at different scales in Australia, Germany, and Belgium (Lundie et al, 2004). Assessing sustainability of Urban Water Systems is a major task considering the high complexity of such a system. Decision-making needs to consider several aspects of health, environment, economy, socio-culture and technical function within a framework that includes interactions between users, organizations and technology. Important issues compromising sustainability in all these aspects are the efficient use of water and energy, the assessment for microbial risk, nutrient recycling and the emission toxic substances to the environment (Malmqvist and Palmquist, 2005, Jeppson and Hellstrom, 2002). The efficient use of water and energy is related to all processes taking place in the Urban Water System, the microbial risk is of primary concern for drinking water supply, nutrient recycling and toxic substances are related to wastewater treatment and sludge disposal. Nevertheless, several studies have proven that untreated storm water is a major responsible for hazardous emissions coming form cities. This fact along with the well known risks related to floods has increasingly turned the attention towards planning and management of storm water as a key element for Urban Sustainability (Jeppson and Hellstrom, 2002) 9
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