Hydrogeological Assessment and Modified Conceptual Model of a Dinaric Karst Island Aquifer

Josip Terzić,Tihomir Frangen,Jasmina Lukač Reberski,Staša Borović,Matko Patekar

doi:10.3390/w14030404

Abstract

Vis Island is situated in southern Croatia. The island is mostly composed of karstified carbonate rocks and belongs to the Dinaric karst region, which is a locus typicus of karst landforms. Located far from the mainland, Vis island has maintained a successful water supply from its own karst aquifer for decades. Hydrogeological research has been undertaken to protect this excellent karst aquifer by establishing sanitary protection zones and to explore the possibility of increasing the pumping yield. New groundwater velocity data obtained via a tracer test were in accordance with the rock mass hydraulic conductivity calculated from previous pumping tests. The hydrochemical interpretation indicated several different phenomena, from carbonate and sulfate rock dissolution to seawater mixing with groundwater. A conceptual model of the island’s aquifer was improved, and two main catchments were delineated according to tracer test results, and connected with the geological setting, hydrochemical data, and new climatological insights. Such an approach is applicable for similar karst aquifers, in which topographic and hydrogeological divides usually do not coincide.

Highlights

Karst rocks are among the most important aquifer formations in the world [1,2,3,4].Approximately half of the Croatian territory is part of the Dinaric karst region, which is characterized by very deep karstification that is predefined by tectonics and a differentiated dissolution of carbonate rocks [5]
Half of the Croatian territory is part of the Dinaric karst region, which is characterized by very deep karstification that is predefined by tectonics and a differentiated dissolution of carbonate rocks [5]
In addition to the methods described in detail below, the following general geological and hydrogeological methods were used in this research: (1) the reinterpretations of existing small-scale maps (1:50,000 and 1:100,000), with special attention given to aerial image interpretations in order to delineate karst poljes; (2) analyzing large scale (1:5000) geological and hydrogeological maps of the immediate hinterlands of wells and springs; (3) interpretation of existing groundwater level (GWL) data; (4) common interpretation of all results, including GIS visualization

Summary

Introduction

Karst rocks are among the most important aquifer formations in the world [1,2,3,4].Approximately half of the Croatian territory is part of the Dinaric karst region, which is characterized by very deep karstification that is predefined by tectonics and a differentiated dissolution of carbonate rocks [5]. The coastal and island aquifers involve further complexity due to the possibility of seawater intrusions [6]. As a consequence of Holocene changes in the global seawater level, the base of karstification in the Adriatic islands was much lower than it would have been according to the present sea level [7,8]. This means that aquifers can exist in much deeper zones, but it enables seawater intrusion into the karst underground via much deeper karst conduits and joints within the rock mass

Methods

Results

Discussion

Conclusion