Climate footprint in karst aquifers derived from time series and spatial data: the case of Orce-Maria (SE Spain)

摘要

The alignment of carbonates comprising the Orce and Maria mountain chains rides the surface hydrological divide between the catchment basins of the Guadalquivir River and the Segura River. They are influenced by Atlantic precipitation on the western side and Mediterranean on the eastern side. These circumstances cause differences in the precipitation recharge which are reflected in the groundwater, and they can be studied in the recharge response recorded not only in piezometers, but also in springs. The hydrochemical and isotopic characteristics of the groundwater can also be conditioned by these different climate environments. An analysis of piezometric and hydrometric series and of hydrochemical and isotopic data shows that the precipitation recharge with Mediterranean influence is predominant despite the fact that only 30 % of the outcrops are in that catchment basin. In the main discharge zones are springs in carbonate outcrops and in outcrops associated with Pliocene and Quaternary material. The data reveal a mixing of waters on the borders of the mountain chains deriving from the carbonate aquifer and from the Pliocene and Quaternary detrital sediments overlying the aquifers on its borders. There are differences between the chemical compositions of the water circulating through the Maria mountain and through Orce mountain carbonates, interpreted as the result of a greater or lesser presence of dolomites. The isotopic data can be used to identify water infiltrating from Mediterranean or Atlantic areas of influence. The values of delta O-18 are between -9.38 and -6.46, and in the case of delta H-2 between -61.73 and -44.46. In the Maria mountains (Mediterranean influence), the average is of -8.75 and -53.63, respectively, and of -9.01 and -59.41 in samples related to the carbonates of the Orce mountains (Atlantic influence). The mean for the deuterium excess is of 15.8 in the first case and 13.4 in the second one.