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

Systems Analysis of Zaragoza UWS
Guillermo Penagos
treatment in Zaragoza requires large amounts of chemical reagents implying not jus
a high cost of water treatment, but also a risk to public health due to DBPs.
Shifting to a different raw water source and thereby reducing treatment cost and
improving water quality is a strong need for the city. From 2008 the city will receive
water from the Pyrenees, specifically from the Yesa reservoir which regulates the
Aragon River and is also used for irrigation and hydropower production. A significant
improvement of tap water quality for Zaragoza is expected from this new source. This
will be discussed further on in the Scenario Analysis section.
4.2.1.2 Storm water
Zaragoza is located in a semiarid region with an average precipitation of 270 mm per
year, which is concentrated within 70 to 80 days (see figure 4a, showing 2006 daily
based hydrograph as example). Precipitation per day in Zaragoza would rarely
exceed 20 mm and dry and wet periods are not quite distinct. However, highest
maximums and highest averages are reached in May and in September, but rarely
exceeding 50 mm per month. Lowest averages and lowest minimums are usually
reached in August and in December (see figure 4b).
Daily p recip itation for 2006 ( mm)
50
40
30
20
10
0
Total precipitation = 288 mm
Days with precipitation = 86
J F M A M J J A S O N D
Month
a
Month p recip itation (m m)
50
40
30
20
10
0
J F M A M J J A S O N D
Month
b
Figure 4. Annual precipitation hydrographs for Zaragoza.
4a. Daily based hydrograph for 2006
4b. Month averages. Error bars represent standard deviation
Source Local Agenda 21 Office of Zaragoza
Due to these hydrologic conditions storm water is not considered an issue by the
Municipality. Nevertheless eventual overflows of storm water are discharged directly
in the Ebro River without any treatment. Therefore Municipality is building two storm
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