Multidisciplinary investigations of a karst reservoir for managed aquifer recharge applications on the island of Vis (Croatia)

Abstract

Managed aquifer recharge (MAR) refers to a suite of methods by which excess surface water or non-conventional water is stored underground for subsequent recovery or environmental purposes. MAR solutions have been largely used in unconsolidated aquifers, while their application in karst aquifers is rare. This research presents the first results of a MAR viability study on the island of Vis, a small karstic island in the Adriatic Sea. Favorable geological and hydrogeological conditions enable the formation of karst aquifers, making the island autonomous in terms of water supply. The island’s main aquifer, exploited in the Korita well field, is protected from seawater intrusion by several hydrogeological barriers. However, climate change and high seasonal pressures related to tourism pose a threat to the future availability of freshwater. Multidisciplinary field and laboratory investigations were carried out to detail the geological and hydrogeological setting of the island and its groundwater resource. Field analyses consisted of groundwater monitoring and sampling, geophysical investigations (i.e., electrical resistivity tomography), and structural measurements. Laboratory analyses included measurements of principal cations and anions and tritium activity. Despite low precipitation during the observation period (September 2019 - December 2020), the groundwater resource at the Korita site showed stable trends of physico-chemical parameters with a good storage potential and a long-term reserve. Geophysical investigations evidenced a relatively homogeneous sequence of the rock mass at a larger scale, while structural analyses indicated the occurrence of E-W karstified and open fractures that could represent a preferential flow path in the carbonate aquifer. A MAR solution for the Vis island was proposed combining an infiltration pond scheme with the direct injection of the accumulated waters into the aquifer using available wells. The potential water source could be represented by the runoff collected in an old artificial channel and the associated pond system in Korita.

Hydrogeochemistry and Isotopic Composition of Waters in the Renella Cave (Central Italy): New Insights into Groundwater Dynamics

“…Hence, the overexploitation of these groundwater resources due to human activities is a global issue [13] and is further emphasized by climate change that modifies the hydrological cycle [14,15]. Investigation on karst groundwater is challenging due to significant karstification that determines distinctive heterogeneity and anisotropy of the aquifer's hydraulic properties [16,17]. The high effective infiltration rates and high flow velocities determine the rapid transfer of recharging waters into karst systems with very short water residence times, which results in their high vulnerability [18].…”

Multidisciplinary Research of Thermal Springs Area in Topusko (Croatia)

“…The major anion and cation composition of thermal water is graphically presented in the Piper diagram (Figure 3) [51]. All samples show Ca-HCO 3 hydrochemical facies [79], with a dominance of Ca 2+ cation followed by Mg 2+ , which is a characteristic of groundwater in carbonate aquifers [80][81][82]. The ion composition is almost constant over time, which indicates a large and stable hydrothermal system.…”

Feasibility Study of Managed Aquifer Recharge Deployment on the Island of Vis (Croatia)

“…The maximum pumping capacity at Korita is approximately 42 L/s from all wells, and the groundwater quality is excellent since the aquifer is protected from seawater intrusions by various hydrogeological barriers [18]. The wells K1 and B1 and the Pizdica spring in the western part of the island provide a total of approximately 5 L/s, and here the water quality is variable and mostly depends on the seasonal hydrological conditions [21]. In the last several years, the annual quantity of the abstracted groundwater has ranged from 300,000 to 450,000 m 3 , depending on the summer tourism demand, and there are 4150 registered water users on the island.…”

“…In this case, the MAR concept is based on the recharge of the karst aquifer by the infiltration pond method, commonly used to recharge unconfined aquifers. The aim of MAR is to enhance and secure the quantitative status of groundwater resources in a karst aquifer, which endures high stresses during the dry In particular, the island of Vis was chosen due to its autonomy in terms of water supp which is uncommon for most islands in the Adriatic and Mediterranean seas [18][19][20][21]. Ho ever, the karstic aquifer from which the groundwater is abstracted, as mentioned above under considerable stress during the dry summer season, and reductions for consum In particular, the island of Vis was chosen due to its autonomy in terms of water supply, which is uncommon for most islands in the Adriatic and Mediterranean seas [18][19][20][21].…”

“…The aim of MAR is to enhance and secure the quantitative status of groundwater resources in a karst aquifer, which endures high stresses during the dry In particular, the island of Vis was chosen due to its autonomy in terms of water supp which is uncommon for most islands in the Adriatic and Mediterranean seas [18][19][20][21]. Ho ever, the karstic aquifer from which the groundwater is abstracted, as mentioned above under considerable stress during the dry summer season, and reductions for consum In particular, the island of Vis was chosen due to its autonomy in terms of water supply, which is uncommon for most islands in the Adriatic and Mediterranean seas [18][19][20][21]. However, the karstic aquifer from which the groundwater is abstracted, as mentioned above, is under considerable stress during the dry summer season, and reductions for consumers have occurred on several occasions in the last decade.…”