Abstract
The hydraulic phenomenon of upwelling groundwater flow affecting the karst area of the Grassano-Telese springs (southern Italy) has been investigated through piezometric measurements, discharge, and chemical–physical monitoring of springs, radon activity included. Locally, both large karst springs and sulfurous thermal springs are closely located, and raise several questions on their origin. In this study, the phenomenon of the upwelling flow is supported by different types of evidences: Amazing density of sinkholes connected to hypogenic speleogenesis processes, constancy of temperature, and hydraulic conductivity of spring water, change of radon activity during the hydrological year, increasing of the hydraulic head with depth. Numerical code provides an estimation of the upwelling phenomenon in an unconfined aquifer feeding the karst springs, using MODFLOW tools. Based on the results reached, the phenomenon of the upwelling flow is able to explain the hydrological processes observed in the Telese karst area.
Highlights
Karst systems are able to concentrate in a restricted zone, the discharge area, the drainage of a wide groundwater catchment [1,2,3]
The upwelling phenomenon that affects some basal karst springs can be associated to the regional groundwater model [5,6,7], in which descendant and ascendant flows characterize the recharge and discharge area, respectively
A very high concentration of karst closed depressions were observed for the carbonate relief of Montepugliano, especially inside the central and western sector; in addition, a main alignment of sinkholes was observed in NW–SE direction, parallel to the Montepugliano ridge direction, where a probable tectonic line is present
Summary
Karst systems are able to concentrate in a restricted zone, the discharge area, the drainage of a wide groundwater catchment [1,2,3]. A single or a group of karst springs are located, which originate or feed rivers. Karst aquifers can be characterized by a high transmissivity and a high capacity to store large volumes of water, which allow a deep-water circulation generating ascendant flows in the discharge zones, where basal springs are located [4]. The upwelling phenomenon that affects some basal karst springs can be associated to the regional groundwater model [5,6,7], in which descendant and ascendant flows characterize the recharge and discharge area, respectively. Fiorillo et al [4]
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