Respuesta hidrológica del sistema kárstico Güixas-Rebeco ante las precipitaciones (Villanúa, Pirineo Central)

Resumo

The Güixas-Rebeco caves (~1000 m a.s.l) represent the discharge sector of the karstic system located in the Collarada massif (Villanúa, Central Pyrenees). Güixas is a show cave, while Rebeco is usually visited by cavers. Both caves present upper entrances which act as a trop-plein. In 2017 several pressure sensors were installed to control water level fluctuations, as well as pluviometers in the high altitudes (~1700 and 2600 m a.s.l) of the massif to control rainfall inputs. Water flow was punctually estimated using salt gauging techniques. Floods in the caves affect to the touristic visits and make impossible the entrance in Rebeco cave. The water rises through a -14 m siphon flooding the touristic area. Tracer experiments not showed the hydrological connexion between caves. Water level monitoring shows similar responses linked to the rainfall events in both systems. The flow rates of ~ 900 l/s in the tourist gallery of the Güixas concur with water ascents through the upper entrance of the Rebeco. This flow rate corresponds with rainfalls around 60 mm, with a response of 8 hours. Floodings increase during spring, when snow melting is added to the rainfall amount. Moreover, daily water level fluctuations are observed in relation with snowmelt, reaching the maximum water level during the nights. The response of both caves should be related to the amount and mode of water inputs in the system, the amount of water retained and the water lost. This study is the first step for the quantitative paleoflood reconstruction based on stalagmites.