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

Abstract

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.

Identification of Aquifer Recharge Sources as the Origin of Emerging Contaminants in Intensive Agricultural Areas. La Plana de Castellón, Spain

“…Before 1970, the amount of groundwater pumped in the Rambleta area was approximately 5 million m 3 /y. This pumping water reached a maximum in the mid-nineties with a total extraction of approximately 25 million m 3 /y; however, this value was progressively decreasing after this peak and has reached 14 million m 3 /y in recent years [40]. The causes of the decreasing need for groundwater extraction were as follows: (1) the irrigation system was modernized and optimized and (2) due to loss of groundwater quality, the reclaimed water from the Vall de Uxó WWTP, located 2 km SSW from the study area, supplied a few irrigation ponds and other facilities for agricultural irrigation purposes.…”

“…The different studies conducted in the southern part of La Plana de Castellón aquifer provide details of the geology [41] and the hydrogeology [42,43]. Specific topics have also been addressed, such as studies on salinization, seawater intrusion, and groundwater contamination (e.g., by heavy metals, EC, and nitrate) [28,39,40,[44][45][46][47][48][49].…”

“…It is a tectonic basin formed during the Tertiary as a result of the Neogene distension that generated a complex of horsts and grabens that continue beneath the sea. In the Rambleta area, two formations are recognized: upper and lower detrital aquifers-the upper detrital aquifer (UDA) and the lower detrital aquifer (LDA)-respectively [40]. The UDA (80-90 m depth) consists of conglomerates, sands, and gravels, with a significant proportion of fines.…”

“…The contour lines of the groundwater heads ( Figure 2) show two minima, one in the west and the other in the center of the area. These two depressions modify the natural groundwater flow direction and have caused a notable increase in seawater intrusion due to a significant upconing process [40].…”

“…Maps of chlorides (up) and nitrates (down) concentrations in the Rambleta area, October 2012 (modified from[40]). …”