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Over the past fifty years, thermal waters with temperatures of up to 65 °C have served as the basis for heating, health and recreational tourism in Topusko town. Natural thermal springs with temperatures of up to 53°C, which emerge in the discharge area of the Topusko hydrothermal system, are located at the junction of two major tectonic units: the SW margin of the Pannonian Basin System and the Dinarides. Initial research data were very scarce, so the presented results comprise the most recent findings gathered in the scope of the HyTheC research project. Hydrochemical and geothermometric research of thermal waters was done together with the application of geophysical investigations to improve the existing conceptual model of the Topusko hydrothermal system. The two main objectives of the presented work are the hydrogeochemical characterisation of the naturally emerging thermal waters and the identification of a fault damage zone in the spring area by electrical resistivity tomography. The hydrogeochemical facies Ca-HCO3 of thermal water was determined, the equilibrium reservoir temperature was estimated to be 88 °C using a SiO2-quartz geothermometer, and the assumed fault damage zones were identified for the first time in the discharge area of thermal springs.

Topusko hydrothermal system is located at the junction of two major tectonic units: the southwestern margin of the Pannonian Basin System (PBS) and the Dinarides. The PBS is known for its high geothermal gradient and surface heat flow. Thus, the north-eastern part of Croatia has favorable geothermal characteristics (average geothermal gradient 49 °C/km ; average surface heat flow 76 mW/m2), where natural thermal water springs, with temperatures up to 65 °C, emerge at two dozen localities. In the past fifty years, these waters served as a basis for developing tourism and health care centers. In the last forty years thermal water has also been used for heating in the city of Topusko. Thermal springs are part of hydrothermal systems, including recharge areas in the mountainous hinterlands of the springs, geothermal aquifers – in Croatia mostly Mesozoic carbonate rocks, and discharge areas in places with favorable structural characteristics of higher permeability. Refining of the available conceptual model will be based on multidisciplinary research which is currently underway. Hydrogeological, geothermal, hydrogeochemical, structural, and geophysical investigations and remote sensing will be used to construct an improved conceptual model. Its physical validity will be tested through numerical simulations supported by 3D geological reconstructions and local hydrogeological and thermal parameterization of the hydrostratigraphic units. Sustainable use of natural thermal springs cannot be planned or ensured without understanding at the system level. Having good conceptual and numerical models enables the delineation and protection of recharge areas and the determination of sustainable pumping rates. Preliminary results of ongoing research will be presented: geochemical characterization of thermal water, stabile and radioactive isotope signatures, geothermometry, as well as the identification of fault damage zones in the spring area using electrical resistivity tomography.

The Golubinka spring is a typical coastal karst spring. It is situated in Northern Dalmatia, Croatia. The groundwater springs through the cave system, while most of the catchment area is built of karstified limestones. Geophysical research ; electrical tomography profiles have been done to improve understanding of the springs’ nearby outflow system. In the paper, these findings have been compared with hydrochemical circumstances and previous conceptual models, and they pointed out a few relevant facts. There are several karst conduit systems at the end of the catchment, connected or not with the previously explored cave systems. A conceptual model was improved based on the detailed hydrogeological map of the spring’s second sanitary protection zone and new findings obtained by electrical resistivity tomography. The research was conducted within the Interreg Adrion project MUHA (Multihazard framework for water-related risks management) because it was the project’s pilot area in Croatia. The explorations' main goal was to better understand hydrogeological circumstances in this very complex Dinaric karst system. The spring is coastal, and seawater penetration into its aquifer happens periodically. The spring is also a public water supply extraction site, and its protection significantly depends on the geological structure and rock mass karstification. MUHA project targets several types of hazards and risks that affect potable water resources and water-related issues (accidental pollution, flooding, drought, and failure of critical infrastructure due to earthquakes). Seawater influence on the Golubinka spring water is highly connected with drought events and pumping for water supply. These main hazards decrease groundwater pressure in the karst aquifer and allow seawater intrusions. Conceptual modeling and a better understanding of the spring’s nearby hinterland can lead to engineering solutions, such as corrections of the pumping regime and/or relocating the extraction site in the future.

The increase in thermal water utilisation is foreseen by many European and Croatian strategic documents regulating energetics, tourism, environmental protection and sustainable development.Croatian Geological Surveywishesto establisha multidisciplinary group for hydrothermalsystems research, which will contribute to responsible geothermaldevelopment in our countrythrough a 5-year research project HyTheC which started in 2020.Pannonian part of Croatia has favourable geothermal characteristics and natural thermal water springs emerge at two dozen localities, with temperatures up to 65 °C. These waters have been used for millennia, and in the past fifty years they are a basis forthe development oftourism and health care centres[1]. As their water demand increased, higher quantities were abstractedand additional intake structures and wells were constructed.Thermal springs are part of hydrothermal systems which include: recharge areas in the mountainous hinterlands of the springs ; geothermal aquifers (in Croatia mostly Mesozoic carbonate rocks[2]) in which water resides and gets heated due to heat flow from the Earth ; and discharge areas in places with favourable structural characteristics of higher permeability.The continuous functioning of such systems depends on a delicate balance between groundwater flow velocities, precipitation/dissolution processes and structural framework.In order to maintain that balance and use thermal water resources in a sustainable manner, a system-level understanding is required.Multidisciplinary methodology (structural geology, hydrogeology, geothermal, hydrogeochemical and geophysical research and remote sensing) will be used to construct conceptual models of systems, perform 3D geological modelling, hydrogeological and thermal parametrisation of the geological units involved in the thermal fluid flow, and conduct numerical simulations of system functioning in undisturbed conditions and with different extraction scenarios.Thismethodology will be tested in three pilot areasin Croatia where thermal water is used(Daruvar, Hrvatsko zagorjeand Topusko).These three areas have a different level of initial data availability and it shall therefore be determined which methodology and order of applicationof different methods should be applied while researching the systems with considerable existing data, medium amount of data and very scarce data, respectively.

Hydrothermal resources have been used for tourism and energy purposes in Pannonian part of Croatia for decades. Due to favourable geothermal and structural characteristics, natural thermal water springs emerge at two dozen localities, with temperatures up to 65 °C. Thermal springs are part of hydrothermal systems (HTS) which include: recharge areas in the mountainous hinterlands of the springs ; geothermal aquifers (in Croatia mostly Mesozoic carbonate rocks) in which water resides and gets heated due to heat flow from the Earth ; and discharge areas in places with favourable structural characteristics of higher permeability. The continuous functioning of such systems depends on a delicate balance between groundwater flow velocities, precipitation/dissolution processes and structural framework. The increase in thermal water utilisation is foreseen by many European and Croatian strategic documents regulating energetics, tourism, environmental protection and sustainable development. Sustainable utilisation of thermal water resource from natural springs demands understanding on a system level. It is necessary to investigate the whole cycle ‐ from recharge to discharge of the systems. Multidisciplinary methodology (structural geology, hydrogeology, geothermal, hydrogeochemical and geophysical research and remote sensing) will be used to develop and physically validate the conceptual models of HTSs, perform 3D geological modelling, hydrogeological and thermal parametrisation of the geological units involved in the thermal fluid flow, and conduct numerical simulations of system functioning in undisturbed conditions and with different extraction scenarios. The aim is to delineate geothermal resources, locate aquifers or structures that may control aquifers, or assess the general properties of the HTS. Methodology will be applied to three HTS pilot areas in the Pannonian part of Croatia, all of which are well known for the utilisation of their thermal water resources: Daruvar, Hrvatsko zagorje and Topusko. These three systems have a different level of initial data availability and it shall therefore be determined which methodology and order of application of different methods should be applied while researching the systems with considerable existing data, medium amount of data and very scarce data, respectively.

Managed aquifer recharge (MAR) refers to a suite of methods by which excess surface water is diverted underground where it is stored for subsequent recovery. Although MAR has a long history of implementation in aquifers with intergranular porosity, its application in the karst environment presents major challenges due to the high heterogeneity of karst aquifers (Dillon et al., 2019). This research was focused on conducting a MAR feasibility study on the island of Vis, a small karstic island in the Croatian part of the Adriatic Sea, where favorable geological and hydrogeological conditions enabled the formation of high-quality karst aquifers, making the island autonomous in terms of water supply. The island’s main aquifer is protected from seawater intrusions by several hydrogeological barriers, however, climate change and high seasonal pressures related to tourism pose a threat to the future availability of freshwater. To investigate whether a MAR operation is feasible and suitable for the karst aquifer on Vis, detailed field and laboratory investigations were carried out. Field investigations included in-situ measurements of physicochemical parameters on water samples from springs and boreholes, groundwater monitoring (conductivity, temperature, and water levels), geophysical methods (ERT, magnetotellurics, and seismic refraction), and structural measurements. Laboratory analyses included measurements of stable water isotopes, principal cations and anions, tritium activity, and analyses of stable isotopes from dissolved sulphates. The results corroborated the available conceptual model of the water resources detailing the geometry of the carbonate aquifer and of the fracture systems driving the water circulation. A 3D numerical model (FEFLOW) of the island will be developed to simulate various scenarios of climate change, with and without MAR. The integration of the obtained results with historical data and previous research will be used for implementing efficient and sustainable management of the karst aquifer through MAR or alternative solutions on Vis island.

Bezubost se danas uspješno rješava sa pokrovnom protezom retiniranom ili poduprtom implantatima. Ona predstavlja zamjenu za konvencionalnu potpunu protezu. Pokrovna proteza na implantatima značajno poboljšava kvalitetu života. Tijekom razvoja dentalne implantologije, razvijale su se različite makro i mikro karakteristike dentalnih implantata, a samo određene su prisutne još i danas. One utječu na preživljavanje implantata. Makro karakteristike podrazumijevaju makro dizajn, dakle oblik i geometriju implantata, a mikro karakteristike podrazumijevaju površina implantata i tehnike njene obrade. One su važan faktor u osiguravanju uspješne osteointegracije. Omogućavaju adheziju stanica na površinu implantata, veći kontakt kost - implantat i ubrzavaju osteointegraciju, koja je ključ dugoročnog uspjeha implantata. Danas se koriste uglavnom cilindrični implantati s navojima, a površine implantata se modificiraju na različite načine kako bi se postigla odgovarajuća hrapavost. Tehnike modifikacije površine implantata mogu biti aditivne i ablativne. Ablativne tehnike danas prevladavaju. Određene karakteristike implantata važno je imati na umu kako bi se terapija pokrovnom protezom na implantatima prilagodila pacijentu i kako bi se konačni ishod terapije učinio predvidljivijim. Stopa preživljavanja implantata pod pokrovnom protezom je visoka, ali treba uzeti u obzir da na nju mogu utjecati brojni drugi faktori vezani uz sam implantat kao i oni vezani uz pacijenta, a ne samo makro i mikro karakterstike implantata. Today, edentulism is successfully solved with an implant supported or retained overdenture. It is a replacement for the conventional complete denture. An implant overdenture significantly improves the quality of life. During the development of dental implantology, various macro and micro characteristics of dental implants were developed, but only some are still in use today. They affect the survival of implants. Macro characteristics imply macro design, i.e. the shape and the geometry of the implant, while micro characteristics imply the surface of an implant and the techniques of its modification. Both are important factors in ensuring successful osseointegration. They enable cell adhesion to the implant surface, larger bone-implant contact, and an acceleration of osseointegration, which is the key to the long-term success implants. Cylindrical threaded implants are the ones mostly used today, and their surface is modified in various ways to achieve the appropriate roughness. Implant surface modification techniques in current use are additive and ablative, with the ablative technique being the most prevalent today. In order to adapt the implantoprosthetic overdenture therapy to an individual patient, and to make the final outcome of the therapy more predictable, it is important to keep those implant characteristics in mind. The survival rate of implants under an overdenture is high but it should be taken into consideration that it can be influenced by a number of other factors related to the implant itself, as well as by those related to the patient, and not solely by the macro and micro characteristics of the implant.

Bezubost se danas uspješno rješava sa pokrovnom protezom retiniranom ili poduprtom implantatima. Ona predstavlja zamjenu za konvencionalnu potpunu protezu. Pokrovna proteza na implantatima značajno poboljšava kvalitetu života. Tijekom razvoja dentalne implantologije, razvijale su se različite makro i mikrokarakteristike dentalnih implantata, a samo određene su prisutne još i danas. One utječu na preživljavanje implantata. Makrokarakteristike podrazumijevaju makro dizajn, dakle oblik i geometriju implantata, a mikrokarakteristike podrazumijevaju površina implantata i tehnike njene obrade. One su važan faktor u osiguravanju uspješne osteointegracije. Omogućavaju adheziju stanica na površinu implantata, veći kontakt kost - implantat i ubrzavaju osteointegraciju, koja je ključ dugoročnog uspjeha implantata. Danas se koriste uglavnom cilindrični implantati s navojima, a površine implantata se modificiraju na različite načine kako bi se postigla odgovarajuća hrapavost. Tehnike modifikacije površine implantata mogu biti aditivne i ablativne. Ablativne tehnike danas prevladavaju. Određene karakteristike implantata važno je imati na umu kako bi se terapija pokrovnom protezom na implantatima prilagodila pacijentu i kako bi se konačni ishod terapije učinio predvidljivijim. Stopa preživljavanja implantata pod pokrovnom protezom je visoka, ali treba uzeti u obzir da na nju mogu utjecati brojni drugi faktori vezani uz sam implantat kao i oni vezani uz pacijenta, a ne samo makro i mikrokarakterstike implantata.

Introduction: There are different fluoride regimens aimed to reduce caries during orthodontic treatment with fixed appliances. Due to unpredictable compliance, there is a need for a long-term low-dose fluoride release delivery system. The aim of this study was to evaluate reported fluoride regimes in current use. Materials and Methods: The literature search with keywords „fluoride release orthodontic“was reached through PubMed website (US National Library of Medicine, National Institute of Health). The literature search with keywords „polycaprolactone fluoride“ was done through the same website, as well. Results: A total of 132 published studies reported fluoride use during orthodontic treatment with fixed appliances. Twenty five studies were dealing with wire corrosion and ion release, reviews and other topics, and were excluded from further analysis. One hundred and seven studies used 6 different sources of fluoride for orthodontic treatment with fixed appliances. The most used were orthodontic adhesives (70%) followed by topical fluorides (10%), elastomeric ligatures (7%), fluoride sustained release devices (6%), removable appliances and retainers (5%) and coated wires or brackets (2%). The literature search on polycaprolactone fluoride revealed 18 relevant studies. Among those, there were stuides about developing new clinical applications of polycprolactone flouride, with existing laboratory methods for incorporation and release of fluorides in/from polycaprolactone flouride. Conclusions: Intraoral fluoride release delivery systems take a small part in caries prevention. There is a need for improvement of existing and development of new fluoride release delivery systems. Polycaprolactone is promising material for sustained fluoride release.

Environmental tracers in ground water are naturally present substances and physical properties of the water that are depended on flow properties and processes happening within the groundwater flow system. Monitoring of such tracers in karst spring water enables insight in characteristics of typically extremely heterogeneous and complex karst groundwater systems. Commonly used environmental tracers include electrical conductivity, temperature, turbidity, ionic composition, stable isotopes of water, organic carbon, nitrates, etc. These tracers provide valuable information regarding infiltration mechanisms, epikarst function, mean groundwater transit times, dynamics of fast and slow flow, etc (TRČEK & ZOJER, 2010). Air saturation in spring water is not commonly monitored parameter in hydrogeological studies, although supersaturation with air, or “excess air”, is a phenomenon which periodically or permanently occurs on some karstic springs (SURBECK, 2005 ; HEATON & VOGEL, 1981). On the other hand it is a very important parameter for fish farming, as oversaturation with gases can cause fatal “gas bubble disease” in fish (MACHOVA et al., 2017 ; WEITKAMP & KATZ, 1980). Therefore, fish farming community is well aware of this phenomenon. Krbavica spring, situated near Krbavsko polje in Croatian Lika region, is known among local population as inadequate for fish farming although it is a permanent spring with a relatively stable discharge even in draught periods. Bubble formation is visible in a spring pool during the most of the year. The spring is captured for public water supply, and monitoring program on it was established to investigate properties of the karst system which feeds it. Among other natural tracers, dissolved oxygen, as an indicator of “excess air” in spring water, was also monitored in high temporal resolution. Monitoring data shows that oxygen saturation is in clear relation to discharge dynamics. During peaks in hydrograph values of oxygen saturation temporarily dropped, followed by maximum values with delay of several days. Increased oxygen saturation was interpreted as an increased proportion of flow through narrow fractures in a vadose zone in a closed flow conditions. Air bubbles captured in water infiltrating to narrow fractures gradually dissolve due to pressure rising and isolation from the atmosphere. In contrary, water flow through larger, karstified fractures and conduits in vadose zone is in open flow conditions, i.e. water pressure is equilibrated with the atmospheric pressure. Therefore, drops in oxygen oversaturation during hydrograph peaks are interpreted as a consequence of increased flow through larger openings within the vadose zone. Flow through narrower fractures is most intense after the rainfall events, when pressure rising in fractures mobilises water. In order for groundwater to remain oversaturated, conduits within the deeper parts of the system that drain water to the spring should be dominantly phreatic, i.e. situated completely below the groundwater level. It can be concluded that monitoring of air saturation in spring water can provide valuable information on the processes within the system, especially if it is combined with monitoring of discharge dynamics and additional tracers.

Monitoring of various natural tracers in a spring water provide insight in groundwater flow characteristics and processes happening within the karst hydrogeological system. Electrical conductivity, temperature, turbidity, stable isotopes, organic carbon, nitrates, etc. are more and more commonly monitored on karst springs in order to provide information on infiltration mechanisms, epikarst function, mean groundwater transit times, interrelation and dynamics of fast and slow flow, etc. Supersaturation of gases or “air excess” in spring water is a phenomenon which occurs periodically or permanently in some karstic springs. Fish farming literature is well aware of this phenomenon, as gases oversaturation can cause fatal “gas bubble disease” in fish. In contrary, this phenomenon was very rarely investigated within the karst hydrogeological research. Some of the karst springs in Dinaric karst of Croatia are known among local community as occasionally fatal for fish due to gas oversaturation, but this was never monitored or researched in more detail. Krbavica Spring in Lika Region of Croatian Dinaric karst is captured for the local water supply. In a spring capture reservoir bubble formation is visible with variable intensity during different periods of the year. Within the monitoring program of multiple natural tracers in spring water, high temporal resolution monitoring of dissolved oxygen was established. Dissolved oxygen was monitored as an indicator of excess air in spring water. Preliminary analysis and interpretation of the observed data points to the gas oversaturation as a good indicator of flow characteristics within the system, e.g. indicator of “closed flow” through fractures of the vadose zone, as well as flow through dominantly phreatic conduits in the deeper parts of the system.

Tracing tests are one of the most powerful tools in investigation of karst system hydrogeological properties (GOLDSCHEIDER & DREW, 2007). Tracing typically consists of injection of artificial tracer in a system of karst conduits and afterward monitoring of tracer concentration in discharging water of selected springs. Therefore, it directly reveals underground flow directions, velocities and dispersion within the system. However, considerably different results obtained from repeated tracings of the same sinkhole are common in karst areas (e.g. KUHTA et al., 2010 ; STROJ et al., 2010). Significant differences are commonly present in apparent groundwater velocities and dispersion, and sometimes even in groundwater directions. Inconsistencies in results of the repetitive tests are usually interpreted as a consequence of different hydrologic conditions within the system during performance of the tests. However, methodology of tracer monitoring in Croatia significantly evolved during 1980s: from detection of tracer using quartz lamp to detection using a laboratory spectrofluorometer. If properly used, spectrofluorometer enables much lower detection limit, i.e. much more reliable tracer detection at low concentrations. In recent years usage of field fluorometers also enabled high temporal resolution of sampling, and consequently determination of very detailed tracer concentration curves. Typically, tracer concentration curves show characteristic and relatively regular shapes, regardless if they are single or multi peaked. Therefore, highly irregular shape of tracer curves obtained by quartz lamp at concentrations close to detection limit gives rise to doubt in positive tracer detection. Within the karstic catchment of the Gacka river springs, several tracing tests were carried out over the time period from 1950s till present. Present knowledge about this regional and complex karst system is largely based on the results of these tests. Recently, a multi-tracer test in medium-low water conditions was performed. Usage of field fluorimeters together with hydrological monitoring enabled acquiring detailed tracer concentration and recovery curves. Despite relatively high tracer recovery, apparent ground flow velocities were much lower in comparison to the previous results. Comparison of results obtained in medium-low flow and in high flow conditions is particularly valuable for comprehensive estimation of karst system properties. Determined flow directions were quite different in comparison to some of the older results (reviewed in PAVIČIĆ, 1997), while they were consistent with more recent ones (KUHTA et al., 2010 ; KUHTA & FRANGEN, 2013). It can generally be concluded that caution is needed during interpretation of relatively old tracing test results considering determined tracer concentrations to detection limit ratio and concentration curve shape.

Vodonosnik zahvaćen na crpilištu Sikirevci pripada strateškim zalihama podzemnih voda Republike Hrvatske. Za uspješno gospodarenje ovim važnim rezervama nužno je poznavati dinamiku podzemne vode u vodonosnom sustavu u postojećim uvjetima na temelju koje se može analizirati ponašanje sustava u različitim budućim scenarijima. Cilj provedenih istraživanja usmjeren je na detaljno istraživanje hidrodinamičkih značajki zahvaćenog vodonosnog sustava, definiranje napajanja vodonosnog sustava te porijekla i starosti podzemne vode. Kao alat za određivanje napajanja istraživanog vodonosnog sustava korišten je trodimenzionalni numerički model. U radu je prikazan postupak izrade konceptualnog modela te izrada i kalibracija numeričkog modela vodonosnog sustava. Model je kalibriran za razdoblje od pet i pol godina na temelju izmjerenih razina podzemne vode te je postignuto vrlo dobro podudaranje mjerenih i izračunatih vrijednosti. U sklopu terenskih istraživanja prikupljeni su uzorci podzemne vode, oborina i rijeke Save te su napravljene analize stabilnih izotopa kisika i vodika, tricija te osnovnih fizikalno- kemijskih pokazatelja. Izotopna i hidrokemijska istraživanja pomogla su u izradi konceptualnog modela. Koncentracije tricija u podzemnoj vodi pokazale su da je vrijeme zadržavanja vode dulje od 65 godina, što se slaže s rezultatima provedene simulacije trasiranja čestica. Hidrokemijska istraživanja su također pokazala da su u vodonosnom sustavu brzine toka razmjerno niske, što uzrokuje dugo zadržavanje vode u podzemlju. Analiza bilance mase pokazala je da infiltracija oborina predstavlja glavni izvor obnavljanja podzemne vode na području modela, što je potvrđeno rezultatima analiza stabilnih izotopa kisika i vodika. Pražnjenje podzemnih voda odvija se u rijeku Savu, osim u razdobljima visokih vodostaja kada Sava napaja vodonosnik. Iako je u prirodnim uvjetima rijeka Sava hidraulička granica, modeliranje je pokazalo da već kod relativno niskih crpnih količina od 200 L/s dolazi do toka podzemne vode ispod rijeke iz susjedne BiH, što upućuje na prekogranični karakter istraživanog vodonosnog sustava. Količine dotjecanja trebale bi se potvrditi kalibracijom desne obale Save, što nije bilo moguće zbog nepostojanja podataka o razinama podzemne vode na tom području., The aquifer captured on the wellfield Sikirevci is a part of the strategic water reserves of the Republic of Croatia. For effective management of these important water reserves it is necessary to know the dynamics of groundwater flow in the aquifer system under existing conditions which enables us to analyze the behavior of the system in a variety of future scenarios. The aim of the planned research is focused on a detailed study of hydrodynamic characteristics of the captured aquifer system, on defining recharge and also the origin and age of groundwater. Three-dimensional numerical model was used as a tool of defining recharge of the investigated aquifer system. This paper describes the process of developing a conceptual model and the development and calibration of numerical model of groundwater system. The model was calibrated for a period of five and a half years on the basis of measured groundwater levels and very good agreement between measured and calculated values was achieved. During field works the samples of groundwater, rainfall and river water were collected and the analysis of stable isotopes of oxygen and hydrogen, tritium and physico-chemical parameters were conducted. Isotopic and hydrochemical research helped in the development of a conceptual model. The concentrations of tritium in groundwater showed that the residence time of water is more than 65 years, which is consistent with the results of the simulation of particle tracking. Hydrochemical studies have also shown that flow rates in the aquifer system are relatively low, causing long residence time of water. Mass balance analysis showed that the infiltration of rainfall is the main source of groundwater recharge in the area of the model. The same was confirmed by the results of the analysis of stable isotopes of oxygen and hydrogen. The groundwater discharges in the Sava river, except during periods of high water levels when Sava river recharges the aquifer. Although the Save river forms hydraulic boundary in natural conditions, modeling results have shown that even relatively low pumping rates of 200 L/s cause the flow beneath the river from the neighbouringh Bosnia and Herzegovina to occur. This suggests transboundary character of the investigated groundwater system. The amount of inflow should be confirmed with the calibration of the right bank of the Sava river, which was not possible due to lack of groundwater levels data in that area.

According to the EU Water Framework Directive, groundwater has a good status if anthropogenic changes do not significantly endanger surface waters connected to them and do not significantly harm terrestrial ecosystems dependent on them. A status assessment of groundwater bodies (GWB) from the standpoint of groundwater-associated aquatic ecosystems (GWAAE) and groundwater-dependent terrestrial ecosystems (GDTE) was made for Croatian Waters (Hrvatske vode) and needs of River Basin Management Plan for the period 2016 – 2021. GWAAE and GWDTE were isolated, and a methodology for a status assessment of associated groundwater was defined. The methodology for risk assessment indicates failure to achieve a good status if the groundwater status is not satisfactory or a risk of failure to achieve the goal of "preventing status deterioration" if the groundwater status is satisfactory, but there is large pressure on the groundwater. The interconnection of groundwater with surface waters is characteristic of almost all GWBs in Croatia. In karst areas, groundwater-dependent aquatic ecosystems (springs and speleological objects) predominate, while in the Pannonian part of Croatia, there are groundwater-dependent terrestrial ecosystems. The groundwater status and risk assessment were analysed from two standpoints – the quantity and quality of groundwater. On the basis of the proposed methodologies in all GWBs, the status was defined as good. One GWB was marked as being at risk. The reliability of these assessments is often low because of low data availability. A proposition for research monitoring was developed, with the purpose of more thoroughly defining the groundwater status with dependent ecosystems in the future.

U ovom radu opisane su najčešće korištene metode (Hazen, Beyer, USBR, Slichter, Terzaghi i Kozeny Carman) za izračun hidrauličke vodljivosti pijesaka. Ukazano je na česte pogrješke kod korištenja navedenih metoda. Sve navedene metode su testirane na uzorcima sa pokusnih polja u sjevernoj Hrvatskoj i ocijenjene.

U radu su opisana hidrogeološka obilježja Dravskog bazena na području između Koprivnice i Đurđevca i prikazani rezultati simulacije toka podzemne vode u uvjetima intenzivnog crpljenja. Na razmatranom području akumulirana je znatna količina podzemne vode koja se obnavlja infiltracijom padalina. Zaključeno je da crpljenje većih količina vode od postojećih neće negativno utjecati na okolne ekosustave.

Redox processes affect the chemical quality of groundwater in an aquifer and can mobilize or immobilize heavy metals which occur naturally in the aquifer materials. Determining types of redox processes that occur in the aquifer and understanding how they affect concentrations of heavy metals are essential to assessing and describing the groundwater quality. In the alluvial aquifer of the Drava River which consists of Quaternary and Upper Miocene deposits (gravel, sand, silt, clay), elevated concentrations of heavy metals have been observed in the Koprivnica region. The groundwater is mainly used for water supply of the town Koprivnica and surrounding settlements. In order to determine hydrochemical processes controlling the groundwater quality, groundwater samples were collected from piezometric wells in monthly campaigns (from July 2013 till November 2014) and analysed in the Hydrochemical laboratory at Croatian Geological Survey. It was observed that in waters with higher concentrations of dissolved oxygen and nitrates, lower concentrations of iron and manganese were measured. In waters with higher concentrations of iron and manganese, lower concentrations of dissolved oxygen and nitrates were measured. The aquifer matrix contains silicate and carbonate minerals, organic materials, and sulphide minerals such as pyrite. The hydrochemical interpretation and geochemical modelling using NETPATH_WIN and PHREEQCI showed that during the oxidation of organic matter and pyrite, reduction of dissolved oxygen is observed. Since oxygen tends to be consumed along the aquifer, under the anoxic conditions, the next most energetically favourable available electron acceptor is nitrates. Because of these processes iron and manganese concentrations are higher and dissolved oxygen and nitrates are very low. Moreover, it was observed that, in the circumstances, when oxygen and nitrates were consumed next electron acceptors were manganese (IV), ferric iron and sulphates.

Analizom postojećih podataka i provedenih terenskih istraživanja izrađen je konceptualni model šireg područja crpilišta Sikirevci. Za izradu konceptualnog hidrogeološkog modela korišteni su svi dostupni podaci: istražna bušenja, pokusna crpljenja, vodostaj rijeke Save te razine podzemne vode u piezometrima. Definirana je geološka podloga modela, hidrogeološki parametri vodonosnika te rubni uvjeti modela. Razine podzemne vode i režim rada crpilišta kontinuirano se prate od 2007. godine, što predstavlja neizostavnu podlogu za kalibraciju matematičkog modela i simulaciju različitih scenarija režima rada crpilišta.

Ugradnja automatskih mjerača omogućuje kontinuirano mjerenje razine podzemne vode. Time se ostvaruje dovoljno velik broj pouzdanih izmjerenih vrijednosti za identifikaciju lokalnih gubitaka zdenca kombiniranjem Jacobove i Thiemove jednadžbe. Uvrštavanjem primjerene vrijednosti iznosa lokalnih gubitaka, kolebanja koeficijenta formacijskih gubitaka nestaju, a njegova vrijednost prati pravac s laganim trendom rasta

Buduće crpilište regionalnog vodovoda kod Đurđevca smješteno je 1.5 km sjeverozapadno od grada Đurđevca i 3.9 km od postojećeg crpilišta Đurđevac uz južni rubni dio Dravskog bazena. Analizom podatataka pokusnog crpljenja pomoću nekoliko metoda zaključeno je da prosječna vrijednost transmisivnosti vodonosnika iznosi oko 0.06 m2/s, a hidrauličke vodljivosti oko 0.001 m/s. Ocrt hidroizohipsi ukazuje na tok podzemne vode prema istoku u skladu s regionalnim ocrtom razina podzemne vode. Kakvoća podzemne vode zadovoljava uvjete zdravstveno ispravne vode za piće. Visoki iznosi hidrogeoloških parametara vodonosnika upućuju na mogućnost zahvaćanja znatne količine podzemne vode koju treba definirati daljnjim istraživanjima.

Na hidrogeološke odnose na području Baranje danas utječu pomaci strukturnih jedinica koji su započeli u pliocenu, a posebno su izraženi tijekom kvartara. U litologiji ovog područja dominira jedan ili najviše dva sloja jednoličnog srednjozrnastoga pijeska koji mjestimice prelazi u sitnozrni pijesak, a mjestimice u šljunkoviti pijesak. Spomenute strukture odnosno njihov utjecaj odražava se i na prirodnu kakvoću podzemne vode, koja se razlikuje s obzirom na pojedine epizode izdizanja i spuštanja naslaga što je utjecalo na oksidacijske odnosno reduktivne uvjete taloženja

Crpilište Ravnik nalazi se u zapadnom dijelu Savskog bazena i smješteno je između jugozapadnih padina Moslavačke gore i autoputa Zagreb - Slavonski Brod. Prosječna godišnja crpna količina je oko 62 l/s. Podzemna voda prirodno sadrži visoke koncentracije mangana i željeza zbog čega se voda prerađuje. Eksploatacija podzemne vode uzrokovala je razmjerno velika sniženja razine vode u crpnim zdencima što je tumačeno precrpljivanjem vodonosnika. Matematičkim modeliranjem strujanja podzemne vode provedenim prije 15-ak godina utvrđeno je da se vodonosnik napaja infiltracijom padalina koja iznosi 14-15% prosječnih godišnjih padalina. U radu je prikazano današnje stanje razina podzemne vode na crpilištu i stanje crpnih zdenaca.

Prema geotektonskoj klasifikaciji Dravski bazen pripada južnom rubnom dijelu Panonskog bazena. Karakterizira ga razmjerno velika debljina istaloženih kvartarnih naslaga unutar kojih je formiran vodonosnik intergranularne poroznosti sa znatnim količinama akumulirane podzemne vode. Sedimentacijski je materijal iz izvorišnog područja prenošen prvenstveno rijekom Dravom, premda se ne može zanemariti i donos iz južnih i sjevernih predjela. Debljina vodonosnika se povećava u smjeru istoka, a u istom se smjeru postupno smanjuje i prosječna veličina zrna zbog pada energije vodenog toka. U zapadnim predjelima prevladava u litološkom sastavu vodonosnika šljunak s različitim udjelima pješčane komponente (BABIĆ et.al., 1978 ; MILETIĆ et.al. 1973 ; URUMOVIĆ et.al., 1990 ; LARVA, 2008). U središnjem se predjelima lateralno i vertikalno smjenjuju šljunak i pijesak, a od Suhopolja nizvodno dominira srednjozrnati do sitnozrnati jednolični pijesak (BABIĆ et.al., 1978 ; MILETIĆ, 1969 ; MILETIĆ et.al. 1973 ; PRELOGOVIĆ & VELIĆ, 1988). Mjestimice se i u zapadnim predjelima unutar šljunčanih naslaga nalaze pješčani slojevi kao posljedica povremenog pada energije vodenog toka. U krovini vodonosnika većinom se nalaze slabopropusne glinovito-prašinaste naslage. Na krajnjem zapadnom dijelu njihova debljina često ne prelaze 1 m a mjestimično u cijelosti izostaju ili se sastoje isključivo od humusnog materijala (URUMOVIĆ et.al., 1990 ; MARKOVIĆ, 2007 ; LARVA, 2008). Idući prema istoku debljina im se povećava i mjestimično iznosi više od 30 m (BABIĆ et.al., 1978 ; MILETIĆ et.al., 1973). Geološki i hidrogeološki uvjeti su utjecali na kemizam podzemnih voda na području Dravskog bazena. Promatrajući osnovni ionski sastav podzemne vode motrenog područja pripadaju od Ca-HCO3, do CaMg- HCO3 hidrokemijskom facijesu u zapadnom i središnjem dijelu bazena što je posljedica dominatnog otapanja karbonatnih minerala (kalcit i dolomit). U istočnom dijelu bazena podzemna voda pripada CaMg-HCO3, MgCa-HCO3, CaMgNa-HCO3 i NaCa- HCO3 hidrokemijskim facijesima. Hidrokemijski facijes upućuje na dominantan utjecaj otapanja karbonatnih minerala u vodonosnicima, međutim ukazuje i na ionsku zamjenu Ca2+ (iz vode) i Na+ (iz minerala glina) u vodonosniku. Koncentracije sulfata i klorida na cijelom području su ispod MDK vrijednosti, koje za navedene ione iznosi 250 mg/l. U zapadnom dijelu bazena (šira okolica grada Varaždina i Čakovca), u prvom vodonosniku, koncentracije nitrata prelaze MDK vrijednost 50 mg/l, te prosječna vrijednost iznosi 75 mg/l. U drugom vodonosniku, koncentracije nitrata su daleko ispod MDK vrijednosti i prosječna vrijednost iznosi 19, 8 mg/l. Visoke koncentracije nitrata su posljedica uporabe prirodnih i umjetnih gnojiva (MARKOVIĆ, 2007). Povremeno u tom području zamjećuju se i visoke koncentracije amonijaka, ortofosfta i nitrita (MARKOVIĆ, 2007). Visoke koncentracije nitrata zabilježene su i u plitkim vodonosnicima središnjeg dijela bazena. U smjeru istoka koncentracije nitrata znatno opadaju i prosječne vrijednosti iznose 2, 8 mg/l. Međutim u ovom području u pojedinim vodonosnim horizontima su povišene koncentracije Fe, Mn, As, Zn, Pb i NH4+ . Njihovo podrijetlo je prirodno i nije inducirano antropogenom aktivnošću

Crpilište Livade nalazi se u sjeverozapadnom dijelu Baranje i koristi se kao izvorište vodoopskrbe Belog Manastira. Za promatrano područje, kao i za cijelu Baranju karakteristično je da se na površini nalaze pretežito kvartarne naslage. Obnavljanje podzemnih voda u ovim se predjelima odvija infiltracijom padalina u polupropusne površinske naslage. Voda se crpi iz kvartarnog vodonosnika koji je izgrađen od sitno do krupnozrnatog pijeska uz nešto valutica šljunka u donjem dijelu. U ovom diplomskom radu načinjena je reinterpretacija pokusnog crpljenja zdenca izvedenog 1979. godine. Prema podacima pokusnog crpljenja identificirani su hidrogeološki parametri vodonosnika i krovinskog vodozadržnoga sloja po Hantushovoj metodi točke infleksije. Pritom je radi pojednostavljenja zanemaren učinak kolebanja razine vode u pokrovnome sloju. Na području crpilišta Livade izražena je relativno dobra ujednačenost transmisivnosti vodonosnika, pa vrijednosti hidrogeoloških parametara identificirane na temelju provedenog pokusnog crpljenja dobro izražavaju hidrauličko ponašanje vodonosnika. Podaci o crpnim količinama na crpilištu Livade i podaci o razvitku stanja razina podzemnih voda potvrđuju učinkovito obnavljanje podzemnih voda na ovom području.