Drainage and siphoning of a karstic spring: a case study

Abstract

The Fuentetoba Spring, with a mean flow of 210 L s-1, releases the discharge from an aquifer that comprises three hydraulically-connected synclines. The spring has a very irregular flow of between 8 L s-1 and 3,400 L s-1 due to the predominant water circulation that is non-Darcian turbulent flow as an underground torrent in the vadose zone, as well as through well-developed karstic conduits in the phreatic and epiphreatic zones, as attested to by speleological explorations. The long response times to recharge by the Fuentetoba karstic system, seen in the spring´s hydrograph, are controlled by regional factors. Nevertheless, certain responses that have very long time lags under high water conditions might be governed in the final stretch of the flowpath by mechanisms of pressure or siphoning of the floodwave, and perhaps by constrictions or plugs of sediment in the conduits.