Spatial characterization of the seawater upconing process in a coastal Mediterranean aquifer (Plana de Castellón, Spain): evolution and controls

In this contribution, we describe the formation and evolution of the upconing process in a Mediterranean coastal aquifer. The study area has experienced severe salinization over the last 40 years because of intensive exploitation of groundwater. We used historical and current records of piezometric levels and chloride concentrations to trace the development of the salinization of the aquifer. We defined the 3D shape of the saline wedge from the spatial distribution of chloride concentrations and vertical well logs of electrical conductivity using monitoring network data. Upconing first appeared in the early 90s and has continued until the present day. In this study, we examined the intensity of the upconing process. Dry periods and the associated increases in pumping caused the advance of seawater intrusion. The sharp reduction in groundwater withdrawals over the last 10 years has caused the saline wedge to move backwards, although the ongoing pumping and the climate conditions mean that this retreat is quite slow

Elementos minoritarios y traza en la masa de agua subterranea 080.021 (Plana de Castelló). Origen y procesos asociados

El acuifero costero de la Plana de Castelló presenta unas características hidrogeoquimicas de gran complejidad, como consecuencia de la de la superposición de procesos tanto naturales como antrópicos, como son la intrusión marina, la contaminación de origen agrícola e industrial y la descarga de aguas sulfatadas desde los acuíferos triásicos de borde. De ellos, el que condiciona en mayor grado las características físico-químicas del agua subterranea es, sin duda, la intrusión marina, que es notable en la mitad meridional y en el extremo septentrional de la Plana. El más relevante proceso modificador asociado a la mezcla de agua dulce y agua salada es el intercambio iónico, que afecta principalmente al calcio y al sodio, y no tanto al magnesio, cuya aparente ganancia está relacionada con aportes de agua de recarga lateral subterranea desde los acuiferos triásicos de la Serra d'Espadà este mismo mecanismo es el responsable del aumento de sulfatos que se acompaña de aportes de litio, estroncio y boro. Las mayores concentraciones se encuentran en los alrededores de la población de Xilxes, donde parecen existir flujos locales intensos, probablemente asociados a altos estructurales del sustrato triásico. Se ha detectado la presencia de elementos minoritarios y traza en concentraciones apreciables. Estos elementos son boro, estroncio, litio, manganeso, hierro, bario,arsénico, selenio, vanadio, flúor, mercurio y cromo. Algunos de estos elementos tienen clara procedencia geoquímica pero otros pueden estar asociados a procesos contaminantes

Characterization of the Salinisation Processes in Aquifers Using Boron Isotopes; Application to South-Eastern Spain

Use of δ11B provides a solid tool for discriminating hydrogeochemical processes in complex coastal aquifers. Its efficiency increases markedly when it is applied along with other major or minor constituents. Nevertheless, various factors may affect its interpretation: the presence of clays, which favour adsorption and desorption, the influence of wastewaters, and even the presence of geothermalism. The δ11B has been applied to the study of a series of aquifers in south-eastern Spain: Castell de Ferro (Granada), Campo de Dalías, Lower Andarax and Sorbas (Almería), all of which are complex and heterogeneous. The results obtained demonstrate that the concentration of Br, the SO4/Cl and Cl/Br ratios are good indicators of marine intrusion. Inland some negative values of δ11B (−16.7 and −8.1‰) are related to a geothermal influence (34.8 and 51.5°C). The boron solubility is directly related to temperature favours boron mobilization, even from the associated metapelitic deposits. The difference in the boron isotope content in two carbonate units must be caused by the different composition of the carbonate rocks, as well as a long residence time