Water Reuse Case Studies in Spain No. 3 Universidad Politécnica de Cataluña STORAGE OF RECLAIMED WATER April 2007 Introduction de Álava et al., 1995) as a coordinated response to the water demands of urban, This study case describes the initiatives industrial, and agricultural users in the taken in Vitoria-Gasteiz, Spain by several Vitoria region. The main objectives of the Irrigation Districts and the Álava Regional plan were 1) to improve water supply Government to build the Azúa Valley reliability, 2) to decrease flooding risks, Lake for storing reclaimed water and 3) to ensure the environmental produced during the winter season as to protection of tributary streams. be able to use it for agricultural and landscape irrigation during the summer The main objective of this case study is to season. This text is an excerpt of the present the role of the Azúa Valley Lake paper presented at the International as an essential component of the IWRR Symposium on Dams in the Societies of Plan of Vitoria-Gasteiz, with particular the XXI Century, Barcelona, 18 June emphasis on: 1) the quality of the 2006 (Mujeriego and López, 2006). reclaimed water that will be stored in it, 2) the environmental and economic Scope and Purpose benefits that will be derived for the region, 3) the improvement in water The city of Vitoria-Gasteiz is the capital of supply reliability that will provide to the both the Álava Foral Territory and the current water supply system, 4) the Regional Government of the Basque reduction of flooding risks associated Country in Spain. With a population of with current management policies for 220,000 inhabitants, it includes a very surface water supply reservoirs, and 5) diverse industrial activity that contributes the definition of those water quality about 30% of its wastewater flows. The management strategies to be followed city of Vitoria-Gasteiz shares its water for maintaining the aesthetic and supply system with the city and the environmental status of the reclaimed regional area of Bilbao, with a water stored in the lake. population close to 1 million inhabitants, through the conjunctive use of the water Water Resources and Water Uses reservoirs of the Zadorra River, with a total useful capacity of 180 hm3. Table CS3-1 summarizes the storage capacity of the Zadorra river reservoirs The urban water supply requirements of and the water demands of the Bilbao and Vitoria-Gasteiz have been surrounding populated areas. Table CS3- exceeding the storage capacity of the 1 clearly shows two basic and important existing reservoirs in a steady increasing facts: 1) the flows provided by the manner during the last decades. This reservoirs are devoted exclusively to situation has prompted the need for the urban water supply and to preservation current water users to provide additional of the rivers’ environmental conditions, water resources, particularly by Vitoria- and 2) the annual water demands Gasteiz, the user with the largest deficit. corresponding to those two uses exceed An Integrated Water Reclamation and the useful capacity of the reservoirs. Reuse (IWRR) Plan for Vitoria-Gasteiz was prepared by the Álava Regional This inadequate water supply reliability, Government in 1992 (Diputación Foral historically estimated at a minimum Water reuse case studies in Spain, No. 3 2 deficit of 20 hm3 per year, has resulted in supply dams, using the pumping serious coordination difficulties over the stations and the pipelines of the last decades for the Inter-regional existing irrigation network. Watershed Agency (Confederación 3. To use reclaimed water for Hidrográfica del Ebro, CHE), the Regional landscape irrigation of parks and Governments of Álava and Vizcaya, the public gardens in the city of Vitoria- City Councils affected, and the Irrigation Gasteiz. Table CS3-2 shows that Districts in the area. landscape irrigation in Vitoria- Gasteiz represents more than 10% of the city’s surface water supply. Table CS3-1. Available water resources and water When the currently proposed new allocations from the Zadorra River reservoirs. landscape areas become active in Reservoir capacity the forthcoming years, that fraction 3 Urrunaga 67 hm will reach an estimated 15% value. Ullibarri 139 hm3 3 Total 206 hm Water Reclamation Authorized maximum volume 180 hm3 Current allocations Water supply to Bilbao 145 hm3 The water reclamation facility of Vitoria- Water supply to Vitoria 25 hm3 Gasteiz began operating in 1995, and has a capacity of 35,000 m3/day, In-stream flows of the Zadorra y Santa 3 30 hm 3 Engracia Rivers equivalent to 12 hm /year. That water Total 200 hm3 volume is sufficient to irrigate 10,000 ha of agricultural land during the summer season. The edaphic characteristics of the Planned Water Reuse and Integrated agricultural areas of the Vitoria region Water Resources Management render summer irrigation a suitable practice under a schedule of once every The Irrigation Districts affected, in three consecutive years. This practical cooperation with the CHE and the Álava requirement results in an agricultural Regional Government, have been surface area actually irrigated during a implementing since 1996 an Integrated summer season close to 3,300 ha, just Water Reclamation and Reuse Plan, with about one third of the 10,000 ha the following main objectives: available to the Irrigation Districts. 1. To use reclaimed water for irrigation of 10,000 ha of several Table CS3-2. Surface water consumption for urban food crops, including orchards and water supply and landscape irrigation in the city of raw eaten vegetables. Irrigation Vitoria-Gasteiz. Urban started in 1996, and covered Landscape Urban 3 Year 3 irrigation, hm area, ha supply, hm initially a surface area of 4,000 ha. (% total use) The additional 6,000 ha began 2003 460 24.6 3.1 (13) irrigation with surface water during 2002 437 24.6 2.5 (10) the summer of 2005, waiting for 2001 402 25.2 2.8 (11) the corresponding volumes of 2000 402 24.8 2.5 (10) reclaimed water that would be stored in the Azúa Valley Lake, by 1999 400 24.5 2.4 (10) the end of 2006. 1998 380 25.3 2.0 (7,9) 2. To replace a fraction of the in- stream ecological flows currently provided from the surface water The water reclamation plant of Vitoria- reservoirs by the corresponding Gasteiz was designed according to the flows of reclaimed water, with the quality criteria for reclaimed water quality level required for included in the Title 22 of the California supporting fish life, namely Water Code (Asano, 1998, Asano et al. salmonid and cyprinid waters 1991). Planned water reuse for (European Council, 1978). Those agricultural irrigation was designed replacement flows would be according to the guidelines and technical introduced just below the water criteria included in the Guidance Manual 3 Storage of reclaimed water prepared by the California State Water off-stream storage reservoir, shaped by Resources Control Board (Pettygrove and two earth dams that form an artificial Asano, 1984; Mujeriego, 1990). lake with a capacity of 7 hm3. The lake has been designed and built according The optimal operation of the water to the environmental requirements reclamation plant was limited by the applicable to a high value natural ability of the irrigation system to store the landscape environment. The lake is reclaimed water produced during the located 75 m over the water level of the fall-winter-spring seasons. The flow nearby surface water reservoirs of the capacity of the water reclamation plant Zadorra River, and just about 2 km from allows irrigation of a maximum of 4,000 them. This topographic situation offers a ha (1,300 ha effective) under continuous unique condition to contemplate the operation during the summer season. possibility for future water contributions However, storing the reclaimed water from the Azúa Valley Lake to the Ullibarri produced during the rest of the year reservoir, after applying the water would provide enough water to irrigate purification processes that may be up to 10,000 ha (3,300 ha effective). To considered necessary at that time. achieve that objective, the IWRR Plan of Vitoria-Gasteiz included the construction of an off-stream reservoir, where Table CS3-4. Physico-chemical quality of reclaimed reclaimed water could be stored during water produced at the water reclamation plant of Vitoria-Gasteiz, from 1996 to 2006. the fall-winter-spring season, and Turbidity < 2 NTU Boron < 1.50 mg/l subsequently used for irrigation during Electrical < 1,000 µS/cm Cadmium ND the summer season. Table CS3-3 conductivity summarizes the water flow provisions Ammonia 1.5-19 mg N/l Chromium < 0.02 mg/l included in the IWRR Plan of Vitoria- nitrogen Gasteiz. BOD5 < 5 mg/l Copper < 0.05 mg/l NO3 2-15 mg/l Mercury ND COD < 20 mg/l Nickel < 0.40 mg/l Table CS3-3. Integrated Water Reclamation and Reuse Oxygen Plan for Vitoria-Gasteiz. < 7 mg/l Lead ND demand Capacity and Uses Objectives Selenium ND Reclamation capacity (2003) 12.00 hm3/year Agricultural uses (2003) 2.40 hm3/year Zinc < 0.40 mg/l 3 Agricultural uses (2006) 7.00 hm /year ND : non detectable, lower than 0.01 mg/l Storage capacity 7.00 hm3/year Existing irrigation network 350 km pipelines Table CS3-5. Organic and microbiological quality of reclaimed water produced at the water reclamation plant of Vitoria-Gasteiz, from 1996 to 2006. Tables CS3-4 and CS3-5 show the water Bromodichloromethane < 5 µg/cm quality achieved by the water Bromoform 1 µg/l reclamation plant of Vitoria-Gasteiz since Chloroform < 30 µg/l 1996, when it became operational. Dibromochloromethane < 1.0 µg/l Reclaimed water satisfies the quality Chlorophenols Non detectable Total coliforms Absence/100 ml criteria specified by the Title 22 of the Helminth eggs Absence/500 ml California Water Code (Asano et al.