A Regional Perspective: Introduction to the Case Studies from Spain & Mexico
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23 Chapter 2 A regional perspective: introduction to the case studies from Spain & Mexico This chapter introduces the case studies that provide the real-world context for the consideration of the topic of this report. Following the presentation of the economic methodology in Chapter 3, economic and financial data drawn from these cases studies is used in Chapter 4 to provide a practical illustration of how the analysis can be carried out, with some indicative results. Case material is drawn from five regions of Spain and Mexico (Table 2.1). Mexico: Case studies Mexico City & Tula Valley Guanajuato City & La Purísima irrigation module. Durango City & Guadalupe Victoria irrigation module. The sites were chosen to indicate both the potential and the practical difficulties arising in water recycling, whether of treated (reclaimed) or untreated wastewater. All the sites have the potential for “win-win” outcomes, in the sense that water recycling can benefit two or more of the parties to the transaction, taken to be urban water authorities (“cities”), farmers, and environmental custodians for the sake of this discussion. Several types of “win-win” projects are represented in the case studies: ¾farmers cede their freshwater rights to cities in return for assured supplies of reclaimed water containing nutrients (Sant Feliu, El Prat, Durango); ¾farmers accept reclaimed water as a complement or alternative to pumping of depleting aquifers, giving them greater reliability and cost savings, with environmental gains (Tordera Delta); ¾the provision of reclaimed water and (untreated) wastewater to agriculture as a solution for urban wastewater treatment and disposal, as well as offering benefits to farmers (Mexico City/Tula, Guanajuato/La Purisima, Gava-Viladecans pre- 1986). Although the principal motives of these various arrangements differ, each offers potential benefits to all three stakeholders mentioned above. The attraction of these arrangements TABLE 2.1 to the farmers is normally the security Case material sites of supply of the effluent water, its Spain: Case studies: fertilising properties, and any savings Llobregat Delta in their own groundwater pumping. Sant Feliu de Llobregat El Prat de Llobregat The appeal of such projects to cities Gavà-Viladecans may be their access to extra fresh Tordera Delta and Costa Brava water at lower costs than they would Blanes otherwise pay, or the opportunity to Castell-Platja d’Aro dispose of wastewater (treated or not) Mexico: Case studies more advantageously than otherwise. Mexico City & Tula Valley The environment is also a potential Guanajuato City & La Purísima irrigation module beneficiary where, for example, it is Durango City & Guadalupe Victoria irrigation module 24 The Wealth of Waste: The economics of wastewater use in agriculture under pressure from development causing over-exploited aquifers, low river levels, depleted wetlands, or coastal saline intrusion in aquifers. In such cases regional authorities responsible for environmental status (environmental custodians) have a direct interest in effluent reuse – either for release into natural water courses (subject to local laws and regulations), or because it allows less abstraction from rivers or aquifers. 2.1 SPAIN: LLOBREGAT DELTA 2.2.1 Site features The Llobregat River basin is situated in the NE part of Spain adjacent to Barcelona, the capital city of Catalonia (Map 2.1). In recent decades, the river Llobregat has been highly polluted by industrial and urban wastewaters, and by surface runoff from agriculture. This river experiences periodic floods and droughts which lead to frequent morphological variations in the river bed and to modifications in its banks. The river Llobregat has two main tributaries, the Cardener River and Anoia River, and all three receive effluent from various sewage treatment plants and industrial effluent, treated and untreated. Furthermore, the occurrence of natural salt formations which are mined in the basin (at Cardona, Súria and Sallent) have been causing an increase in water salinity. The delta of Llobregat River lies to the south of Barcelona city and covers about 100 square kilometres. In spite of its close proximity to the city, it is a valuable natural habitat. Its wetlands are of international importance for wildlife and form a critical wintering ground for many migratory birds. The delta aquifer is one of the most important freshwater resources for the Barcelona region, with a groundwater capacity of 100 Mm3/yr., used by numerous industries, agriculture, and the metropolitan area of Barcelona and surrounding towns. The fertile delta farmland supports intensive agriculture supplying the local market. Since the 1960s, the delta’s land has been under constant pressure from Barcelona’s urban and industrial expansion. Catalonian’s most important logistics and transportation facilities - port, airport, motorway network and railways - have gravitated to the area. The recent port extension forced a southward movement of the river entrance to the sea. Less than 5% of the original wetlands in the area now remain and in some municipalities half of agricultural land has been lost in the last decade. By the end of the 1980s, the Llobregat River was one of the most polluted and degraded in Western Europe. Overexploitation of the underground water had led to salinization of the aquifer, rendering 30% unusable. Since 1991 with the European Directive on Urban Wastewater, a comprehensive programme of wastewater treatment has been implemented along the river and the situation has improved dramatically. New wastewater treatment plants with tertiary facilities have been built, while a water reclamation programme has been planned and implemented to address water shortages and the increasing water demand from all sectors. The entire watershed, including the metropolitan area of Barcelona, depends on water resources from both local and remote sources that are highly variable. When the flow from the Llobregat River is insufficient, more water has to be conveyed from the Ter River to the Llobregat watershed. Aquifer withdrawals are also affected by the water quality of the Llobregat River - if water quality is poor, surface water has to be mixed with more groundwater in order to be treated for domestic use. The water supply for the Barcelona Metropolitan area currently comes from three sources: the Ter River supply (c. 50%); the Llobregat River (c. 40%) through 2 water treatment plants (Sant Joan Despí and Abrera); and groundwater from several wells (c. 10%). A new seawater desalination plant will shortly start operating, with a capacity of 60 Mm3/year. Chapter 2 - A regional perspective: introduction to the case studies from Sapin & Mexico 25 MAP 2.1 Llobregat river basin / -MPCSFHBU 3JWFS $BSEFOFS 3JWFS " "OPJB 3JWFS # B $ C % #BSDFMPOB ,JMPNFUFST 26 The Wealth of Waste: The economics of wastewater use in agriculture Infrastructure exists to prevent excessive pollution of the river by intercepting specific effluents, such as the channels receiving treated urban wastewater from Rubí and those collecting brine from the salt-mine sites (Figure 2.1). Apart from these, there is a major irrigation channel on the right side of the river, the Canal de la Dreta, which provides water extracted from the middle course of the river to horticulture. On the left side of the river the Infanta Canal was also built for irrigation purposes, but now its main role is to divert treated wastewater from industries and towns away from the river so as to improve the latter’s water quality. The aquifer is used mainly for irrigation, having a lower salinity than the river, except in the areas with seawater intrusion. The Llobregat River is the main source of irrigation water, via the Canal de la Dreta, and a small amount via the Canal de la Infanta. At present, in drought conditions, the extraction of the Llobregat aquifers exceeds the natural recharge of 5.6 Mm3/yr. This over-exploitation has led to a new policy aimed at restoring the river basin’s natural state based partly on the reclamation and reuse of treated wastewater. 2.1.2 Wastewater treatment In the study area there are two main wastewater treatment plants (WWTPs): The Sant Feliu de Llobregat WWTP and El Prat de Llobregat WWTP, both with tertiary treatment – see Map 2.2. A third WWTP operates on the western edge of the delta at Gavà-Viladecans, which is discussed below. Effluent from the Sant Feliu de Llobregat WWTP is fully treated to tertiary levels and available for use in irrigated agriculture. The effluent volume - around 19 Mm3/ yr – can be transferred to the Canal de la Dreta to be used for irrigation purposes on FIGURE 2.1 Deflection channels in the lower Llobregat River course -24 423 25" 2UBÓTRIBUTARY !NOIARIVER !NOIADEFLECTIONTO2UBÓTRIBUTARY #ANALDE#APDEVILLAI&ERRERI-ORA #ANALDELA$RETA CONNECTIONCANAL #ANALDE"Y PASS 3&, )NFANTACANAL (IGHWAYCANAL %4!0 'OVERNADORCANAL -24-ARTORELL 25"2UBÓ 2IU,LOBREGAT 3&,3ANT&ELIUDE,LOBREGAT 4234ERRASSA %4!0DE3ANT*OAN$ESPÓ Chapter 2 - A regional perspective: introduction to the case studies from Sapin & Mexico 27 MAP 2.2 Wastewater treatment plants Source: Food and Agricultural Organizatin of the United Nations (2008) the right side of the Llobregat delta. The effluent is usually mixed with well water in order to reach an acceptable water quality for irrigation purposes. The irrigated areas are located in Sant Viçenc dels Horts, a village in the north part of the delta. Currently, only a small proportion of the effluent is actually used by farmers (about 0.2 Mm3/yr), who view it as a last resort to be used in drought periods when sufficient fresh water is not available. El Prat de Llobregat WWTP, with a wastewater generation of around 120 Mm3/yr, is one of the biggest treatment plants not only in Spain but in the whole of Europe. The treatment plant, serving more than 2 million inhabitants, generates 4.5 Mm3/yr of wastewater treated to tertiary levels that can be used to supply the ecological flow of the lower part of the Llobregat river, and to provide water for agricultural irrigation and to supply water to wetlands in the river deltaic areas.