Sistemas de flujo subterráneo regional en el acuífero carbonatado mesozoico de la sierra de Cameros. Sector oriental

Abstract

The hydrogeologic conceptual model of the thermal springs of Baños de Fitero (Navarra) and Arnedillo (La Rioja) is studied. These springs are located in the eastern part of the Cameros Chain, in the contact among the Iberian Chain and the Ebro Basin materials, in the basins of the Alhama and Cidacos rivers respectively. These springs have their origin in regional groundwater flows through the materials of the marine Jurassic (especially of the lower Lías) that constitute a karstified carbonate aquifer. The main discharges of this aquifer take place in the contact among these materials -included in the Cameros unit- and the Ebro Basin materials in the points in which the river crosses the cited contact. The annual mean resources have been evaluated in 5.41 hm³/year for the Cidacos river and 3.52 hm³/year in the case of the Alhama river, that include thermal as not thermal contributions. These springs have fixed chemical composition, predominantly characterized by sodium chloride content, associated with high contents in ions, constant and high emergency temperature and low content in tritium, overall indicative of the presence of a regional groundwater flow. In the regional context is evidenced a regional groundwater flow system, from calcium bicarbonate of low mineralization water to calcium-sulphate water and to sodium- chloride, very mineralized and thermal water. The topography and the contrast of permeabilities (aquitard/aquifer) imply the existence of local flow systems in the aquitard and a regional system through lower aquifer that acts as «main drain» of the upper materials. The geothermal gradient in the discharge zones is more high than the mean geothermal gradient.