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

Systems Analysis of Zaragoza UWS
Guillermo Penagos
8. Sludge production
9. Nutrient recycling to agriculture
10. Heavy metals loads to agriculture
So far water withdrawal and water consumption have already been discussed, but
there is major component of water withdrawal which is not being considered by
Zaragoza municipality within its goals is groundwater, which is under the authority of
the Ebro River Confederation (CHE). Ground water is currently fulfilling 23% of water
requirements for Zaragoza city. Major consumers are industries not connected to
sewer system, corresponding to two paper mills owning private WWTPs.
Groundwater preservation is one of the criteria used to evaluate environmental
sustainability. Being relatively cheaper and usually of higher quality than surface
water, groundwater reserves are being over-exploited in several European countries,
leading to the drying up of spring waters, destruction of wetlands and saline intrusion
of aquifers in coastal zones (Hellstrom et al, 2004). All those problems have been
indeed taking place in Spain, and especially in the Ebro Delta, which is a Ramsar site
and it’s considered as the second most important natural reserve of the country
(CHE, 2007).
The role of groundwater extraction on the environmental impacts of Zaragoza city on
the Ebro Catchment is difficult to assess because this groundwater is not part of the
natural water cycle, but the result of inefficient use of water for irrigation upstream.
According to the Ebro River Working Group this artificial recharge is also feeding the
Ebro River flow (personal communication). Considering that 177,000 ha in Zaragoza
province are currently irrigated and percolation is around 10,000 m 3 ha -1 the influence
of Zaragoza upon this artificial aquifer is probably negligible, but this would require
further research.
In addition to quantity there is also a matter of quality that requires to be assessed
concerning groundwater. First, due to its origin, this groundwater is contaminated
with nitrates (Mema et al, 2006) and probably also with pesticides. Additionally there
is a contamination by persistent chlorinated substances in one of the largest
industrial polygon of Zaragoza city. This is consequence of the inadequate practices
of a large company that used to work there between 1976 and 1985; and it was
discovered in 2006 (CHE, 2006). The implications of speeding up the cycle of this
polluted groundwater in Zaragoza are still unclear. Zaragoza municipality and CHE
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