An estimation of groundwater type and origin of the complex karst catchment using hydrological and hydrogeochemical parameters: A case study of the Gacka river springs

Karst aquifers are heterogeneous terrains, where it is hard to assess any hydraulic parameter. Therefore, a multidisciplinary approach is necessary for research on karst aquifers. Catchment area of the Gacka river springs is typical Dinaric karst terrain built of karstified carbonates. Groundwater flow is mostly directed by preferential flow paths usually connected with main faults and fracture zones. In the presented case study structural geological and tectonic characteristics were defined. A recession diagram was created, and the water balance was calculated. Tracer-test data were also used for analysis. All these data were compared with the bulk hydrogeochemical and isotopic analyses of spring and surface waters. For this purpose, samples were obtained every month for one hydrological year at 17 sampling locations. Processing of all these data allowed a tenable definition of the Gacka spring catchment area

Definition of the river Gacka springs subcatchment areas on the basis of hydrogeological parameters

The river Gacka springs catchment area is located in the Dinaric karst, which is globally known as the locus typicus, or classical Karst. It is composed of four major and several minor karst springs of different discharge rates. The river Gacka springs are characterised by great discharge and exceptional quality, so the catchment area of the river is indicated in the Water Management Strategy (OFFICIAL GAZETTE NO. 91/08) as an area with strategically important eserves of drinking water for the Republic of Croatia. To determine the hydrogeological characteristics of he subcatchments of this large and complex aquifer system, hydrological and hydrochemical parameters were measured on the main springs. Data collected on the springs were analysed using the recession analysis by the „matching strip“ method, the statistical analysis of a time series of measured data both by autocorrelation (analysis of individual series) and by cross-correlation methods (analysis of interrelationships between time series), multivarilate statistical analysis (Factor Analysis) of hydrochemical parameters using the software package STATISTICA 6.0 (1998), and geochemical modelling of hydrochemical parameters using the NETPATH computer program. Interpretation of lithological, structural and tectonic characteristics of the rocks, together with tracing data and the applied analytical methods, allowed the springs catchment of the river Gacka to be divided into three subcatchments. The results of this study imply the necessity of a multidisciplinary approach to research. </p

"Novi onečišćivači" u podzemnim vodama Hrvatske - primjer projekata GeoTwinn i boDEREC-CE

Stanje vodnih resursa i pridruženih ekosustava je pod sve većim pritiskom onečišćenja nastalog kao posljedica neadekvatnih i nereguliranih ljudskih aktivnosti, čiji je utjecaj sve izraženiji gledano s aspekta posljedica promjena klimatskih uvjeta. Tehnološki razvoj analitičkih instrumenata i metoda omogućio je određivanje tzv. novih onečišćivača ( engl. emerging contaminants) odnosno spojeva koji do sada nisu uključeni u redoviti sustav monitoringa, a prepoznat je njihov ekotoksikoloski učinak. U širokom spektru utvrđenih spojeva najčešći su pesticidi, farmaceutici, proizvodi za osobnu njegu, industrijski aditivi i njihovi nusprodukti, dodaci hrani, nusprodukti tretiranja vode, surfaktanti, hormoni i dr. Značajke i uvjeti podzemnog toka i transporta novih onečiščivaća u kompleksnim krškim sredinama uz definiranje učinkovitih mjera (monitoringa, zabrane, prevencije i sl.) koje će ublažiti posljedice spomenutih negativnih utjecaja na stanje podzemnih vodnih resursa istražuju se u sklopu međunarodnih projekata GeoTwinn (Horizon 2020) i boDEREC-CE (Interreg Central Europe). Suradnja s renominiranim stručnjacima obogatit ce dosadašnje spoznaje hrvatskih partnera o ponašanju novih onečiščivaća u ovakvim okolišima te doprinijeti zaštiti i očuvanju podzemnih voda kao neophodnog i strateški važnog resursa pitke vode

Characterizing occurrence of emerging organic contaminants in Dinaric karst catchment of Jadro and Žrnovnica springs, Croatia

The occurrence of emerging organic contaminants (EOCs) was investigated in vulnerable Dinaric karst catchment of Jadro and Žrnovnica springs in Croatia, under varying flow conditions and across three different water resource types (groundwater, springs, and surface water). The maximal EOCs concentration in both springs were observed following autumn recharge events, while during peak discharge no detection above the limits of detection (LOD) was recorded due to dilution process. Contrarily to springs, groundwater from deep borehole exhibited highest total EOCs concentration under low flow conditions, underscoring the considerable karst aquifer vulnerability and its oligotrophic nature. The peak EOCs concentration in karstic Cetina River coincided with the river's lowest discharge. The highest mass flux of 1013 g/day was determined for very mobile pharmaceutical metformin detected in Cetina. The presence of potentially persistent to very persistent compounds, like DEET and 1H-benzotriazole, which exhibited highest detection frequencies across all sampling sites, was observed in association with varying hydrological conditions. Hypotheses regarding the occurrence of identified EOCs include surface contamination infiltrating directly through ponors and highly karstified areas, potential persistence in the epikarst and aquifer matrix, and site-specific contamination sources for compounds such as 1H-benzotriazole, gabapentin, and ketoprofen found in groundwater. To evaluate the risk of inadvertent human exposure to EOCs across various age groups, we utilized measured spring concentrations and calculated drinking water equivalent levels (DWEL), which ranged from 1.4 μg/L for cotinine to 503 mg/L for sucralose, both detected in Jadro spring. Although EOCs concentrations in ng/L are unlikely to pose a significant risk to healthy population, long-term exposure to EOCs mixture remains unknown. Given scarcity of research on EOCs in karst environments on both global and national levels, our study enhances comprehension of their occurrence and behaviour across different karst water resources that hold crucial importance for drinking water supply in regions like Dinarides

Groundwater level and electrical conductivity datasets acquired within pumping tests on Ilovik Island in Croatia

The small karst island of Ilovik is the most southern of inhabited islands in the Croatian part of the Adriatic Sea. During summer tourist season the number of inhabitants increases significantly, and securing the additional freshwater quantities was needed. Given the hydrogeological and geomorphological setting of the island, possibility of brackish groundwater exploitation was considered. Hence, borehole drilling accompanied with pumping tests at three specified locations was carried out. During the pumping tests in two campaigns, groundwater level was measured manually every 2 hours in boreholes, while groundwater electric conductivity and temperature were periodically measured in situ. The sea level was observed at the reference point located near port.Given dataset consists of electrical conductivity, temperature, groundwater and seawater levels. The research article connected with these data (Terzić et al., 2020) provides hydrogeological interpretation of brackish groundwater lens on small karst island

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

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

Emerging organic contaminants in karst groundwater: A global level assessment

A quarter of the world’s population uses groundwater from karst aquifers. A range of emerging organic contaminants (EOCs) are considered a potential threat to water resources and dependant ecosystems, and karst aquifers are the most vulnerable groundwater systems to anthropogenic pollution. This paper provides the first global compilation (based on 50 studies) of EOCs in karst aquifers and explores EOC occurrence and the use of EOCs to understand karst systems. Of the 144 compounds detected in the reviewed studies, the vast majority in karst groundwater are pharmaceuticals and pesticides. Maximum concentrations of compounds varied over five orders of magnitude, and nearly half of the detected compounds exceed 100 ng/L. Karst groundwater is shown to have lower frequency of detection and lower concentrations compared to surface waters and local shallow intergranular aquifers, but overall higher concentrations compared to other major aquifer types. A growing number of studies have demonstrated the utility of EOCs and some legacy compounds for groundwater quality assessment and as tracers for characterising karst systems. They can improve understanding of vulnerability, storage, attenuation mechanisms, and in some cases have been used to assist with catchment delineation. This is a growing research area for karst hydrogeology, and more research is needed to understand EOC contamination of karst aquifers, and to develop EOCs as tracers within karst to improve our understanding of this critical water resource