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Systems Analysis of Zaragoza UWS Guillermo Penagos 4.4.3.3.5 Effect of water recycling on pollution loads to the Ebro River Under the assumptions previously described it is expected that 14% larger pollution loads will be dumped into 14% less sewage volume by 2020. Hence BOD, nutrients and heavy metals will be 28% more concentrated in the sewage. If industrial water recycling is considered then pollutant concentrations in sewage will increase 30% for 10% recycling and 37% for 30% strategy. As consequence of this increased concentration in the inflow, higher removal efficiency at WWTPs would be expected. In order to calculate how much this increasing efficiency would be a regression analysis between pollutant concentrations and removal efficiency was performed for all WWT facilities in Zaragoza. However, no significant correlation was found (r 2 = 0.028, data not shown). Therefore, the assumption is made here that with the current WWT technology and current societal production and consumption patterns, pollution loads to the Ebro River will increase 14% by 2020, even if unaccounted water is reduced and even if industrial water is recycled. 4.4.3.4 Assessment of water quantity and quality for Zaragoza in the future Considering the figures previously described for Sc3 concerning upstream water use and the effect of climate change upon water availability in the Ebro catchment. An assessment of the risk for water availability in Zaragoza was performed. Here an additional scenario for the year 2060 was projected. From figure 24 it is evident that Zaragoza can relay on Yesa reservoir as raw water source for the years to come since Zaragoza requirements projected by the year 2060 with increasing population and no water recycling are well below the projected capacity of the reservoir, even under the worst climate change and water extraction scenario. 52
Systems Analysis of Zaragoza UWS Guillermo Penagos 450 Current 2020 2060 Zaragoza in 2060 400 Water (million m 3 ) 350 300 250 200 150 100 50 0 oct nov dec jan feb mar apr may jun jul aug sep Month Figure 24. Current and projected water storage regimes for Yesa reservoir on a hydrologic year basis under Sc3 scenario. Regimes also include the expected increase in water demand for agriculture as planned by the National Irrigation Plan (Sc3). In this analysis total Zaragoza requirements are included, even those that are currently fulfilled from groundwater. The reason is that National Irrigation Plan also considers the need of upgrading current irrigation technologies to minimize loses. This will reduce the groundwater recharge in Zaragoza and the water table might eventually drop so that it is not that feasible anymore. In such scenario, either the whole city becomes dependent on tap water or the activities that currently use groundwater will turn to the Ebro River, whose discharge will be already considerably reduced by that time. Water quality of Yesa reservoir is more difficult to project. However it is possible to consider TP concentrations as reference point. Current Yesa average TP concentrations on year basis are 21 ug/l. If current inputs are expected to remain constant, then by 2020 average TP concentrations might rise to around 40 ug/l and 60 ug/l by 2060. This situation encompassed with increasing temperature and radiation (due to climate change) would increase the risk for the reservoir to experience algal blooms, which might negatively affect water supply quality for Zaragoza. 53
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