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

Systems Analysis of Zaragoza UWS
Guillermo Penagos
for precipitation might have completely different hydrographs that, may or may not,
lead to sewer overflows. Finally the expected inflow to WWTPs used for storm water
calculation is not a reliable value due to the lack of data concerning parasite flows to
the sewer system from irrigation channels and overflows from breaking pressure
tanks. Therefore the pollution loads from storm water presented here are not to be
interpreted as actual impacts but rather as potential scenarios. Further studies for
Zaragoza concerning this matter are required.
5.5 Drivers for sustainable urban water planning and management
With this overview of current situation of water management in Zaragoza it is now
valid to discuss the drivers that will contribute to define the future of water
management in the city. There are some internal drivers that are under the control of
Zaragoza planning, such as urbanization, population increase and availability of
funds. But cities are far from being isolated systems and they are in fact very much
affected by local, national and global processes at environmental, social, political and
economical level. Therefore a more comprehensive analysis it is important to widen
the perspective both in geography and time. Major external drivers for water
management in Zaragoza that have been considered here are National Policies
(National Plan on Energy and National Irrigation Plan) and Climate change.
The concern of Zaragoza about water withdrawal makes sense since between 30-
60% of Spain is at immediate risk from desertification and the Ebro Valley at Aragon
is already the driest inland region of Europe (UNCD, 2007). Under current trends is
very possible that Zaragoza will still continue to reduce its fresh water withdrawal via
infrastructure upgrading. However, if a further reduction is pursued then additional
strategies will be required. Ongoing strategies in Zaragoza also aim to optimize water
use for landscaping, but this use only represents 5% of total water requirements
(including groundwater). Therefore such strategy is probably not going to have a
significant effect. Presently domestic consumption is already 110 l person -1 day -1 ,
which is already a low consumption. On the other hand, industrial consumption in
Zaragoza is approximately the 40% of total water requirements (including
groundwater). In this report industrial water recycling is proposed as a suitable
alternative to continue reducing water withdrawal. This alternative has not been
considered by the city yet because extracting ground water is technically more
feasible and economically cheaper. However this seems to be the only possibility to
continue reducing water consumption, considering the constraints of reducing
domestic consumption already have.
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