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

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.
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