Laura Asensio

Groundwater resources in the Upper Guadiana Basin (Spain): a regional modelling analysis

The sustainability of groundwater resources has been a central issue in the Upper Guadiana Basin (Spain) since two of its primary aquifer units were declared overexploited at the end of the 1990s. Three hydrogeological aquifer units located to the north of the primary aquifers have rarely been studied because of their low economic value, despite a large part of the wetlands of La Mancha Húmeda Biosphere Reserve overlying the Basin. This report presents the foundations upon which conceptual and numerical models of the Upper Guadiana Basin are based. An evaluation of the sustainability of the groundwater use in Upper Guadiana Basin has been also carried out. The effect of five management options and a simplified climatic-change scenario have been considered for the three northern aquifers. A decrease in the net recharge, a change in river–aquifer interactions, and the total abstraction volumes authorised have been identified as the main factors to address in management planning. In addition, the expected recovery in the primary Western Mancha aquifer is shown to have little correlation with the total volume abstracted from the three northern tributary aquifers.RésuméLa pérennité des ressources en eau souterraine est une question centrale dans le Bassin Supérieur du Guadiana (Espagne) depuis que deux de ses principales unités aquifères ont été déclarées comme surexploitées à la fin des années 1990. Trois unités hydrogéologiques aquifères situées au Nord des aquifères principaux ont rarement été étudiées, en raison de leur faible valeur économique, en dépit du fait qu’une grande part des zones humides de la réserve de biosphère de La Mancha Húmeda recouvre ce bassin. Cet article présente les fondements sur lesquels les modèles conceptuel et numérique du Bassin Supérieur du Guadiana sont basés. Une évaluation de la pérennité de l’utilisation de l’eau souterraine du Bassin Supérieur du Guadiana a aussi été réalisée. L’incidence de cinq options de gestion et d’un scénario simplifié de changement climatique a été considérée pour les trois aquifères du Nord. Une diminution de la recharge nette, un changement des interactions rivière - aquifère et le total des prélèvements autorisés ont été identifiés comme les principaux facteurs à considérer en termes de planification de la gestion. De plus, on montre que la recharge estimée de l’aquifère principal de La Mancha Ouest est peu corrélée avec le volume total prélevé dans les trois aquifères tributaires du Nord.ResumenLa sostenibilidad de los recursos de agua subterránea ha sido un tema central en la Cuenca superior del Guadiana (España) puesto que dos de sus unidades primarias acuíferas fueron declaradas sobreexplotadas a fines de 1990. Tres unidades hidrogeológicas acuíferas situadas al norte de los acuíferos primarios han sido raramente estudiados debido a su bajo valor económico, a pesar de que una gran parte de los humedales de la Reserva de la Biósfera de La Mancha Húmeda yacen por encima de la cuenca. Este trabajo presenta los fundamentos sobre los cuales están basados los modelos conceptuales y numéricos de la cuenca superior del Guadiana. También se llevó a cabo una evaluación de la sostenibilidad del uso del agua subterránea en la cuenca superior del Guadiana. Se ha considerado el efecto de cinco opciones de manejo y un escenario simplificado de cambio climático para los tres acuíferos del norte. Se han identificado como los principales factores para guiar la planificación del manejo, la disminución en la recarga neta, un cambio en las interacciones río – acuífero, y el total de la extracción del volumen autorizado. Además, se muestra que la recuperación esperada en el acuífero primario de la Mancha occidental tiene poca correlación con el volumen total extraído de los tres acuíferos tributarios del norte.ResumoA sustentabilidade dos recursos hídricos subterrâneos tem sido uma questão central na Bacia do Alto Guadiana (Espanha), uma vez que duas das suas principais unidades aquíferas foram declaradas sobre-exploradas no final da década de 1990. Três unidades hidrogeológicas localizadas a norte dos principais aquíferos raramente têm sido alvo de estudos devido ao seu baixo valor económico, apesar de grande parte das zonas húmidas da Reserva da Biosfera de La Mancha Húmeda cobrir a Bacia. Este artigo apresenta os fundamentos nos quais se baseiam os modelos conceptuais e numéricos da Bacia do Alto Guadiana. Também se efetuou uma avaliação da sustentabilidade do uso da água subterrânea na bacia. Para os três aquíferos do norte foram considerados os impactos de cinco alternativas de gestão e um cenário simplificado de mudança climática. Identificaram-se os seguintes fatores principais a considerar no planeamento da gestão: uma diminuição da recarga eficaz, uma mudança nas interações rio-aquífero e nos volumes totais de captação autorizados. Além disso, a recuperação prevista no aquífero principal da Mancha Ocidental mostra-se pouco correlacionada com o volume total captado nos três aquíferos tributários no norte.

Underwater Monitoring of the Cracks Found in Santos Morcillo Lake, Central Spain

This technical note describes the installation and performance of eight vibrating wire crackmeters placed on the bed of Santos Morcillo Lake, Ruidera Lakes Natural Park, Central Spain. Waterproof crackmeters were used, and special attention was taken to anchor them to the bed of the lake. Data loggers were installed on upright posts above the lake water level, and continuous crack opening data were obtained. The data consistency is shown by the low deviation of the readings with respect to its trend, which, in turn, is well correlated with the overall hydrogeologic behavior of the system. The data indicates the correct performance of the measuring system. Therefore, at least for periods of up to 1 year (time window of the study presented here), waterproof crackmeters may be used with confidence in underwater conditions.

Enhanced electrokinetic remediation of polluted soils by anolyte pH conditioning

In the treatment of a polluted soil, the pH has a strong impact on the development of different physicochemical processes as precipitation/dissolution, adsorption/desorption or ionic exchange. In addition, the pH determines the chemical speciation of the compounds present in the system and, consequently, it conditions the transport processes by which those compounds will move. This question has aroused great interest in the development of pH control technologies coupled to soil remediation processes. In electrokinetic remediation processes, pH has usually been controlled by catholyte pH conditioning with acid solutions, applied to cases of heavy metals pollution. However, this method is not effective with pollutants that can be dissociated in anionic species. In this context, this paper presents a study of the electrokinetic remediation of soils polluted with 2,4-Dichlorophenoxyacetic acid, a common polar pesticide, enhanced with an anolyte pH conditioning strategy. A numerical study is proposed to evaluate the effectiveness of the strategy. Several numerical tests have been carried out for NaOH solutions with different concentrations as pH conditioning fluid. The results show that the anolyte pH conditioning strategy makes it possible to control the pH of the soil and, consequently, the chemical speciation of pollutant species. Thus, it is possible to achieve an important flux of pesticide into the anolyte compartment (electro-migration of anionic species and diffusive transport of acid species). This way, it possible to maximise the pesticide accumulation in this compartment, allowing a much more effective removal of pollutants from the soil than without the anolyte pH conditioning strategy.