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

Systems Analysis of Zaragoza UWS
Guillermo Penagos
5 Discussion
The main goal of water management in Zaragoza in the recent years has been to
reduce fresh water withdrawal below 65 million m 3 year -1 . The time horizon for this
goal was the year 2010 but it has been already achieved in 2006. In addition to this,
unaccounted water in Zaragoza has been significantly reduced along these years
from 40 to 32%, but it still remains too high and the volume of actual leakages is still
unknown. This particular aspect is to be assessed by the SWITCH project in
Zaragoza as a demo activity. However it is possible to say that water supply is
significantly and consistently improving in the city. The open question now is whether
this improving makes the urban system as a whole more sustainable.
5.1 Sustainability of UWS
The starting point for assessing sustainability of urban water systems is a definition of
the basic services the system is supposed to provide, before start looking for
alternatives to improve existing technology (Larsen and Gujer, 1997). The services
the urban system should meet are basically three:
• Reliable supply of safe water to all residents for drinking,
hygiene and household purposes
• Safe transport and treatment of wastewater
• Adequate drainage of impervious areas
Zaragoza UWS is currently providing these basic services. However in a second
level, there are some requirements for such services to be considered sustainable
that also need to be assessed. Lundin (1999) propose the following list:
a. Technical performance: defined as the degree of effectiveness (degree of
goal achieving) and efficiency (resource optimization).
b. Reliability, flexibility and adaptability: defined as the capacity of continuing on
providing the service when unexpected events occur, encompassed with the
potential for the system to change.
c. Durability: referring to infrastructure
d. Environmental protection: pollutant emissions as low as required to maintain
the quality of the environment (atmosphere, aquatic ecosystems and soil)
e. Cost-effectiveness: cost recovering of the service and affordability of
investments
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