Alternatives in water resources management in Marina Baja district (Alicante province, Spain)

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1 Alternatives in water resources management in Marina Baja district (Alicante province, Spain) S. Castaño, J.M. Murillo, L. Rodríguez Hernández Instituto Geológico y Minero de España, Spain Diputación Provincial de Alicante, Spain ABSTRACT A water resources simulation model has been applied in Marina Baja district, in Alicante province, as support to water management. In fact, a not planned, conjunctive use system for water supply, working for several decades, does exits in this area. The results of the different alternatives simulated in the model should help decision-makers to improve district water resources management. INTRODUCTION In some Spanish regions with limited water resources, users have exploited both underground and surface waters when they have had troubles in water supply and, of course, streams, reservoirs and aquifers have existed near demands. No specific conjunctive use policy has usually had in the long term planning of water resources among the objectives of national water management [Sánchez González and Murillo, 997]. In Marina Baja district, in Alicante province, there is currently a system of conjunctive use of its water resources which works well since 97 decade [Sánchez González, 98; Sahuquillo, 98]. That system (Fig. ) is being modified according to the users needs and the socioeconomic development of the district. Water resources related conflicts are becoming frequent due to the characteristics of the temporal allocation of surface-water resources, the limitations of surface and underground water storage and explotation, as well as the behavior of different kinds of demands [Castaño et al., ]: urban and turist demands (4 Mm /a), being Benidorm the most important, and irrigation demand ( Mm /a) [Castaño and Murillo, 999b]. The main components of the system (Fig. ) are two relatively small reservoirs. Guadalest reservoir has a maximum capacity about Mm, and it stores water resources from the northwestern area of the district. The maximum capacity of Amadorio reservoir is about 6 Mm and its catchment basin is in the southwestern zone of the district. Currently, these reservoirs are used mainly for urban supply even though they were built for irrigation. Natural water resources of the reservoir basins, analyzed applying a modified version of Témez s rainfall-runoff model [Estrela, 997], are irregular in time. The mean inflow in Guadalest reservoir is 8 Mm /a, even though it can vary between. and Mm /a [Castaño and Murillo, 998a]. The mean inflow to Amadorio reservoir is 6 Mm /a, varying between. and 9 Mm /a [Castaño and Murillo, 999a]. The

2 streamflows in both basins are very irregular and usually simultaneous [Castaño et al. ]. Figure - Geographic situation of Marina Baja and main components of the integrated water resources system. There are two aquifers with an important role in water exploitation in the system since 97 decade. The Beniardá aquifer is upstream from Guadalest reservoir, where the pumped water is stored. The Algar aquifer is the most important source of groundwater in Alicante province and is drained by several springs; their mean total discharge is Mm /a, but it varies between and 8 Mm /a [Castaño and Murillo, 998b]. These springs are used mainly for irrigation, but part of the flow is diverted for urban supply and stored in the Guadalest reservoir. Moreover, in lowflow periods, the Algar aquifer is pumped to the channel of Algar River and the water is used as the natural discharges. Then, two subsystems can be defined for water supply: Algar-Guadalest and Amadorio. The use of groundwater as Guadalest reservoir input permits since a longtime a higher regularity in releases, which are used mainly in urban and tourist supply (Fig. ).

3 8 7 Controlled releases (m /month) Inflows from springs and aquifer in Algar pumping station Inflows from Beniardá aquifer pumpings oct-67 sep-7 sep-77 sep-8 oct-87 sep-9 sep-97 Time Figure - Releases from Guadalest reservoir. Notice increase in regularity after groundwater became one of its inputs (after Castaño et al., ). There are other aquifers in the system (Fig. ) but they only supply a few specific municipalities. Only Polop aquifer, used in Polop and La Nucía, bears some importance because of its central situation in the system and its possibilities for artificial recharge. In addition, some tests have been made to study the use of groundwater from Sella aquifer as inputs in Amadorio reservoir [Castaño and Murillo, 999a]. The Canal Bajo del Algar channel interconnects both Algar-Guadalest and Amadorio subsystems, carrying not used water from the first one to the second one, where is stored. This channel currently carries up to 6 L/s of water when it was built for 5 L/s. Moreover, two ensembles of pipelines ( Conducción General de Guadalest and Conducción General de Amadorio ) link reservoirs to the urban demands. The one from Guadalest supplies the largest number of demands. Some of the farmers associations use reclaimed treated urban wastewater while municipal suppliers use high quality water initially assigned to irrigation. Four wastewater treatment plants work in the general system. The average reclaimed water is different in each one: 75% of consumed water in Benidorm, Alfaz del Pi and Costa de Finestrat, 65% in Villajoyosa, 5% in Altea and 5% in La Nucía [Castaño and Murillo, 999b]. OBJECTIVE AND METHODOLOGY The attempt to decide the allocation among various conflicting uses is one of the main objectives of water resources managers [Grigg and Labadie, 978]. This objective has been applied for optimizing the water resources of Marina Baja, but the

4 model also considers changes in water sources, infrastructures and operating rules in system. So, a management simulation model has been used as a tool to know the system response to those different alternatives. The complex conjunctive use system of Marina Baja has been analyzed using SIMGES [Andreu and Capilla, 99], a general water resources management simulation program developed by the Water Resources Management Group (Departamento de Ingeniería Hidráulica y Medio Ambiente de la Universidad Politécnica de Valencia). Some different simulations, corresponding to different contexts in the system have been established. Thus, it is possible to take into account many alternatives for the utilization of Marina Baja district water resources. The results could be used by decisions-makers to adopt the most beneficial actions for the district. The initial scenario A- considers the current situation of the water resources system (Fig. ). Next, several extreme changes of that scenario have been modeled according to some future projects of the water managers. Finally, previous alternatives have been partially combined in another one that could be more practical to increase the supply reliability of most of demands, optimizing the water resources of the district. The main characteristics of those scenarios are described in Table. Table - Main characteristics of the scenarios of the Marina Baja water resources system simulated using the SIMGES program. Scenario Main characteristics A Current situation A A with constraints on groundwater pumping A A + Improvements in infrastructures connecting main subsystem A A + Sella aquifer pumping A4 A + Constant water transfer from Júcar management system ( Mm /a) A5 A4 + New demands (9.5 Mm /a) A6 A + Increase in wastewater reclamation (% of urban supply) A7 A + Saving water policy (% of demands) A8 A + Artificial recharge of Polop aquifer A9 A + Variable water inputs + Saving water (5% of demands) + Increase in wastewater reuses (9% of urban supply) Alternatives have been simulated for 7-years (from water year until water year). The natural inflows to the system have been assessed for this period where most of usual hydrological situations (droughts and exceptional runoffs) are represented. RESULTS The main results for the different simulations are summarized in Table and Fig. 4. This one displays irrigation and urban supply reliability, and calculated water volume that reaches the final nodes of the model (Mediterranean Sea). Some of the simulated alternatives yield almost complete supply reliability (see A4 and A5 in Fig. 4). They consider water transfer from Júcar River to Amadorio reservoir. The results of the simulation of that alternatives show considerable loss in superficial water resources to Mediterranean Sea and small needs in groundwater pumping, thus decreasing the importance of current regulation of this kind of water resource.

5 Amadorio reservoir Villajoyosa wastewater treatment plant Amadorio catchment basin 5 Orcheta Orcheta aquifer pumping 5 LEGEND Reservoir Water resources input Aquifer Demand Water reclamation Conduit Conduit with loss of water Aquifer-conected conduit Node End node Amadorio River 8 Torres pumping station 4 5 Villajoyosa urban Villajoyosa irrigation Guadalest Reservoir basin Beniarda R Polop 5 aquifer Polop pumping Beniarda aquifer Guadalest reservoir 9 Benidorm urban Cala de Finestrat urban Guadalest R. 8 Callosa urban Polop urban 5 7 Polop irrigation Callosa 9 4 irrigation 4 6 La Nucia urban 8 Benidorm wastewater T.P La Nucia La Nucia irrigation wastewater T.P. 4 Rampuda dam 7 Canal Bajo Algar 4 Alfaz del Pi urban Algar aquifer Algar aquifer pumping 7 Algar pumping station 8 Algar River 9 Alfaz del Pi irrigation Benidorm irrigation Peña Alhama Mandem aquifer pumping station 9 4 Algar R. Altea wastewater Peña Alhama pumping treatment plant 4 Algar-Bolulla basin 4 Altea urban Altea irrigation Amadorio R. Figure - Initial scenario (A) in the simulation of water resources of Marina Baja district. Table. Main results of the management simulations of Marina Baja district water resources system. Total demand Mean deficit Months with empty reservoir (%) Mean pumping rates Mean water outputs Mean external water transfer Scenario (Mm /a) (Mm /a) Amadorio res. Guadalest res. (Mm /a) (Mm /a) (Mm /a) A A A A A A A A A A Other alternatives with partial operational modifications do not yield a significant increasing of the supply reliability. The simulated scenario A, which considers improvements in hydraulic infrastructures, yields higher urban supply reliability than alternative A. Yet, similar results have been reached increasing both wastewater reuse (alternative A6) and water saving (A7). The simultaneity in natural inflows of main regulation elements (reservoirs and El Algar pumping station) does not allow increasing the storage of

6 water in the system. In the two last alternatives (A6 and A7) deficits of irrigation demands decrease as the reliability grows. Demand water supply 99 Reliability in water volume (%) A A A A A4 A5 A6 A7 A8 A9 Scenario Water outputs from the system 5 Water outputs (Mm /a) 5 5 A A A A A4 A5 A6 A7 A8 A9 Scenario Figure 4 Summarized results of irrigation and urban supply reliability and output of water resources towards Mediterranean Sea.

7 Pumping in Sella aquifer to store the groundwater in Amadorio reservoir (alternative A) only increases water resources regulation of Amadorio subsystem but not the water resources of the system. Moreover, artificial recharge of Polop aquifer when inflows exceed storage capacity of Guadalest reservoir (alternative A8) does not cause that reliability are higher because water could only be injected in periods of maximum inflows, when groundwater stored in the aquifer is at its maximum too. Surely, the most adequate simulated alternative for a high supply reliability with an optimal profiency of the own water resources of Marina Baja district (Table and Fig. 4) is that considering mainly water saving policies and the use of other alternative sources for irrigation, such as the wastewater reuse or the pumping of low quality water from some aquifers for other urban uses different to human consumption. Needs of external water transfer are reduced to few periods, but the monthly required volumes reach relatively high values. Moreover artificial recharge, planned groundwater resources use and maintenance of currently deteriorated infrastructures will increase the system efficiency. Acknowledgements The authors are thankful to the Consorcio para Abastecimiento y Saneamiento de la Marina Baja, to the Confederación Hidrográfica del Júcar, to the Universidad Politécnica de Valencia and the municipalities and farmers associations for helpful data and advice. References Andreu, J. and Capilla J., El modelo de gestión de cuencas SIMGES In: J. Andreu (ed.), Conceptos y métodos para la planificación hidrológica, 98-, CIMNE, Barcelona, 99. Castaño, S. and Murillo, J.M., Cálculo de las aportaciones naturales al embalse de Guadalest, ITGE and DPA Tech. Rpt. H.6-.98, 998a. Castaño, S. and Murillo, J.M., Cálculo de las aportaciones naturales a la estación de impulsión de El Algar, ITGE and DPA Tech. Rpt. H.6-.98, 998b. Castaño, S. and Murillo, J.M., Cálculo de las aportaciones al embalse de Amadorio, ITGE and DPA Tech. Rpt. H.6-.99, 999a. Castaño, S. and Murillo, J.M., Estimación de las demandas agrícola y urbana en la Marina Baja, ITGE and DPA Tech. Rpt. H.6-.99, 999b. Castaño, S.; Murillo, J.M. and Rodríguez Hernández, L, Establecimiento de reglas de operación y recomendaciones de gestión de los recursos hídricos de la Marina Baja de Alicante mediante el empleo de un modelo matemático de simulación conjunta Boletín Geológico y Minero, (-), 95-8,. Estrela, T., Formulación teórica del Modelo Témez. Calibración de parámetros In: Master en Hidrología General y Aplicada del CEDEX. Área de Hidrología Superficial II, tomo III, 8p., 997.

8 Grigg, N.S. and Labadie, J.W., Introduction In: Management of water resources: A system approach. English lectures, Colorado State University, Fort Collins,.-., 978. Sahuquillo, A., La utilización conjunta de aguas superficiales y subterráneas como paliativo de la sequía, Hidrogeología y Recursos Hidráulicos, 7, 5-8, 98. Sánchez González, A., Sobre las posibilidades de explotación del embalse subterráneo drenado por las fuentes del Algar (Alicante), Tech. Rpt. 4/8, 98. Sánchez González, A. and Murillo, J.M., Integración de los acuíferos en los sistemas de explotación, Servicio de Publicaciones del Ministerio de Medio Ambiente, Madrid, 4 p., 997. Keywords: Conjunctive use, Marina Baja, simulation models, water resources management. Corresponding author: Silvino Castaño Castaño, Dirección de Hidrogeología y Aguas Subterráneas, Instituto Geológico y Minero de España, C/ Ríos Rosas,, 8-Madrid, Spain. s.castano@igme.es José Manuel Murillo Díaz, Dirección de Hidrogeología y Aguas Subterráneas, Instituto Geológico y Minero de España, C/ Ríos Rosas,, 8-Madrid, Spain. jm.murillo@igme.es Luis Rodríguez Hernández, Departamento de Ciclo Hídrico, Excma. Diputación Provincial de Alicante, Avda. Orihuela, 8, 6-Alicante, Spain.