No abstract

A methodology is described for understanding the interaction of karstic aquifers with allogenic rivers, where little information is available. This methodology includes conventional hydrogenology methods tracer tests and measurements of flow into, out of and circulating within the karstic system. The method is designed to understand the hydrogeological behaviour of a river in sufficient detail, given a short study period. The methodology is applied to a karstic system in Spain, obtaining useful, quantitative results for a hydrological year, such as an estimate of the water balance, differentiation between autogenic and allogenic natural recharge, relationship and connection between the river and the aquifer, and measurements of infiltration capacity in watercourses under different hydrological situations. The paper deals with a useful example that could be applied to other rivers and aquifers where few data are available. It can be applied to aquifers under a natural regime and Mediterranean climate.

The present PhD Thesis aims mainly at studying the natural recharge and hydrodynamics of the Cañón del río Lobos (the Lobos River Canyon) karstic aquifer.This aquifer has an emerging surface of 164 km2, and peripheral basins of less permeable terrain with an extension of 197 km2, where the allogenic rivers that infiltrate into the karst come from. The karstic aquifer is defined by a hydrostratigraphic unit of limestone from the Upper Cretaceous 240 meters thick, which rests on an impermeable base of marls belonging to the same geologic period. The geometry of the aquifer has the following orientation: W.NW.-E.SE; and the aforementioned marls form its lateral limits too. The circulation of subterranean water, which was verified by tracers, makes its way through the ample syncline nucleus towards the home stretch of the Lobos River, where the Manantial de la Galiana is, being the main upwelling of the system. The speed of this subterranean water, which was obtained by the use of tracers as well, varies from 500 to 3.000 m/d, with respect to the proximity of the Manantial de La Galiana and with respect to the hydrologic regime. The high speeds we find here indicate a El drenaje subterráneo en el acuífero kárstico del Cañón del río Lobos (Soria-Burgos)