HYDROGEOLOGICAL RELATIONS ON KARSTIFIED ISLANDS - VIS ISLAND CASE STUDY

Na primjeru otoka Visa prikazan je pristup hidrogeološkim istraživanjima na većim jadranskim otocima. Infiltracija, nakupljanje i istjecanje podzemnih voda odvijaju se u okršenoj stijenskoj masi. Hidrogeološki odnosi su uvjetovani geološkom građom terena, a pritom se ističe posebna važnost postojanja potpune hidrogeološke barijere u komiškom zaljevu, te relativne barijere u području krških polja. Radi rasvjetljavanja hidrogeoloških odnosa tijekom istraživačkih radova 1999. i 2000. godine, uz korištenje prethodnih rezultata, načinjena je opsežna strukturnogeološka razrada terena koja je uz ostala hidrogeološka istraživanja pomogla u identifikaciji oblikovanja i održavanja ovog krškog vodonosnika. Prikazan je i orijentacijski izračun hidrauličke vodljivosti stijenske mase i razina njegove primjenjivosti na ovakvim terenima. Na temelju svih tih metoda došlo se do zaključka kako se na otoku Visu slana morska voda ne proteže ispod cijelog otoka, već poput klina prodire u unutrašnjost po relativno nepropusnoj podlozi, a njena dubina može se procijeniti na više desetaka metara ispod današnje razine mora. Na temelju takvih zaključaka i vodeći računa o hidrološkoj bilanci, može se očekivati ostvarivost povećanja crpnih količina na viškome vodocrpilištu "Korita", kao i izvedba dodatnih zdenaca.An approach to the hydrogeological investigations on Adriatic islands is presented on the Island of Vis case study. Infiltration, accumulation and discharge of the groundwater occur in karstified rock mass. Hydrogeological relations are mostly a consequence of the geological setting, because of the complete hydrogeologic barrier in Komiža bay, and relative barrier in the area of karst poljes. Significant research was performed in the 1999 – 2000 period aimed of better understanding of hydrogeological relations. These investigations, as well as reinterpretation of some previously known data, included structural geology, hydrogeology, hydrology and hydrochemistry. Approximate rock mass hydraulic conductivity calculation is also shown, as well as level of its usability in such terrain. Based on all these methods, it is possible to conclude that on the Island of Vis there is no saline water present underneath the entire island. There is only a saline water wedge which is formed on the top of relatively impermeable base rock, some few tens of meters under recent sea level. With such a model, and taking in account the hydrological balance, it is possible to conclude that there is possibility of higher amount of groundwater exploitation then it is today

Hydrogeological Relationships of the Golubinka Karst Spring in Ljubač Bay, Dalmatia, Croatia

The Golubinka spring is a typical karst spring situated in northern Dalmatia, Croatia. The catchment area is mostly composed of limestones of the Cretaceous and Palaeogene, with some dolomitic parts. Hydrogeological barriers are composed of flysch or Quaternary sediments, and most of them are “hanging” barriers, so that the karst water can flow underneath. Many spelaeological features in the vicinity of the spring point to a typical karst conduit flowing under ground. This has been proven by tracer tests, because a connection exists to the periphery of the catchment with an apparent velocity of 8.1 cm/s. The whole area is situated in the Mediterranean climatic belt, so the precipitation distribution is quite unfavourable – summers are long, hot and dry. This is why the summer seasons usually end with sea water intrusion into the aquifer with a significant increase in chloride ion concentration. Since the spring is capped for water supply, there is a bulk monitoring system established. The data obtained were processed by means of multivariate analysis, and three main types of quality deterioration were recognized. The first is connected with pollution from agriculture and inhabited areas without sewage, the second represents occasional sea water intrusions, while the third relates to heavy rainfall events accompanied by turbidity and pollution. Together with the other conclusions, these results should have a practical purpose primarily in the matter of water protection

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

Hydrological analysis of the karstic Čikola River

U radu je izvršena hidrološka analiza procesa koji se odvijaju duž toka rijeke Čikole koristeći mjerene podatke protoka na tri vodomjerne postaje (Ružić, Drniš i Ključice), oborine mjerene na četiri postaje (Knin, Drniš, Otavice i Muć), i temperature zraka mjerene na meteorološkoj postaji Drniš. Ovaj članak predstavlja novu obradu hidrologije krške rijeke Čikole. Ustanovljeno je da na dionici rijeke između postaja Drniš i Ključice postoje značajniji gubitci vode tijekom sušnog razdoblja. Čini se da između postaja Ružić i Drniš gubitaka poniranja vode u krško podzemlje nema ili su rijetki i neznačajni. Ustanovljeno je da su presušivanja vode na dionici Čikole od Ružića do Drniša nešto češća u posljednjih petnaestak godina, ali tu činjenicu tek treba potvrditi pouzdanijim mjerenjima. Utvrđeno je da izvor Čikole spada u krške izvore s ograničenim maksimalnim izlaznim kapacitetom. Primjenom metode Turca procijenjeno je da površina sliva rijeke Čikole do postaje Ružić iznosi oko 300 km2.The paper describes a hydrological analysis of the processes occurring along the course of the Čikola River based on discharge measurements at three water gauging stations (Ružić, Drniš and Ključice), precipitation measurements at four stations (Knin, Drniš, Otavice and Muć) as well as air temperatures measurements at the meteorological station Drniš. The paper presents new considerations regarding the hydrology of the karst river Čikola. It has been established that the river section between the stations Drniš and Ključice shows signifi cant water losses in the dry period. It appears that that the losses due to water sinking into the karstic underground are absent or rare and insignifi cant in the area between the stations Ružić and Drniš. It has been further established that water drying out in the Čikola section from Ružić to Drniš is slightly more frequent in the past fi fteen years; however, this fi nding should be verifi ed by more reliable measurements. It has been determined that the Čikola source is a karstic spring with a limited maximal output capacity. By implementing the Turc method, it has been estimated that the surface of the Čikola river basin to the station Ružić equals approximately 300 km2

Hydrological analysis of the karstic Čikola River

U radu je izvršena hidrološka analiza procesa koji se odvijaju duž toka rijeke Čikole koristeći mjerene podatke protoka na tri vodomjerne postaje (Ružić, Drniš i Ključice), oborine mjerene na četiri postaje (Knin, Drniš, Otavice i Muć), i temperature zraka mjerene na meteorološkoj postaji Drniš. Ovaj članak predstavlja novu obradu hidrologije krške rijeke Čikole. Ustanovljeno je da na dionici rijeke između postaja Drniš i Ključice postoje značajniji gubitci vode tijekom sušnog razdoblja. Čini se da između postaja Ružić i Drniš gubitaka poniranja vode u krško podzemlje nema ili su rijetki i neznačajni. Ustanovljeno je da su presušivanja vode na dionici Čikole od Ružića do Drniša nešto češća u posljednjih petnaestak godina, ali tu činjenicu tek treba potvrditi pouzdanijim mjerenjima. Utvrđeno je da izvor Čikole spada u krške izvore s ograničenim maksimalnim izlaznim kapacitetom. Primjenom metode Turca procijenjeno je da površina sliva rijeke Čikole do postaje Ružić iznosi oko 300 km2.The paper describes a hydrological analysis of the processes occurring along the course of the Čikola River based on discharge measurements at three water gauging stations (Ružić, Drniš and Ključice), precipitation measurements at four stations (Knin, Drniš, Otavice and Muć) as well as air temperatures measurements at the meteorological station Drniš. The paper presents new considerations regarding the hydrology of the karst river Čikola. It has been established that the river section between the stations Drniš and Ključice shows signifi cant water losses in the dry period. It appears that that the losses due to water sinking into the karstic underground are absent or rare and insignifi cant in the area between the stations Ružić and Drniš. It has been further established that water drying out in the Čikola section from Ružić to Drniš is slightly more frequent in the past fi fteen years; however, this fi nding should be verifi ed by more reliable measurements. It has been determined that the Čikola source is a karstic spring with a limited maximal output capacity. By implementing the Turc method, it has been estimated that the surface of the Čikola river basin to the station Ružić equals approximately 300 km2

EXAMINING THERMAL CONDUCTIVITIES OF SHALLOW SUBSURFACE MATERIALS FOR GROUND SOURCE HEAT PUMP UTILIZATION IN THE PANNONIAN PART OF CROATIA

Termogeološka i hidrogeološka svojstva plitkoga podzemlja u hrvatskome dijelu Panonskog bazena (PBS) istraživana su u kontekstu njegova korištenja za postavljanje sustava dizalica topline s tlom kao izvorom topline (GSHP). Provedene su detaljne determinacije bušotinskih jezgara, uzorkovanja te mjerenja toplinskih parametara za sedam bušotina s četiriju lokacija različitih geoloških obilježja. Sabrani su rezultati ukupno 418 mjerenja provedenih na 82 uzorka sedimenata i stijena te su analizirani u kontekstu postojećih zbirki vrijednosti toplinskih vodljivosti sedimenata i stijena iz Njemačke i Švicarske, koje se često koriste za dimenzioniranje bušotinskih izmjenjivača topline (BHE) i u drugim državama. Utvrđena je razlika u toplinskim vodljivostima između istovrsnih sedimenata i stijena koji potječu iz različitih geoloških sredina. Takvi rezultati upućuju na potrebu razvoja lokalnih setova podataka koji bi omogućili točnije dimenzioniranje izmjenjivača topline. U četirima su bušotinama provedena i testiranja toplinskoga odziva tla (TRT-ovi) te su njihovi rezultati uspoređeni s rezultatima dobivenim direktnim mjerenjem na uzorcima. Usporedba pokazuje da u situacijama kada postoji značajan tok podzemne vode (u krupnije zrnatim sedimentima) mjerenja na uzorcima sistemski podcjenjuju vrijednosti toplinske vodljivosti u odnosu na realno mjerilo, dok su razlike manje kod sitnije zrnatih sedimenata. Zbog toga je pri postojanju značajnoga toka podzemne vode obavezno provoditi TRT-ove, dok se u suprotnome za manje sustave može primjenjivati i analogija s objavljenim podatcima o toplinskim vodljivostima. Važno je imati zbirke takvih podataka zbog slučajeva kada TRT nije ekonomski isplativ. Vrijednosti koje se navode u ovome radu mogu poslužiti kao smjernice za odgovarajuće dimenzioniranje GSHP sustava s ciljem postizanja boljih indikatora, osobito za manje sustave u Hrvatskoj te na drugim geološki usporedivim lokacijama u PBS-u.Thermogeological and hydrogeological properties of the shallow subsurface in the Croatian part of the Pannonian Basin System (PBS) were investigated in the context of its utilization for ground source heat pump (GSHP) systems installation. Detailed borehole core determinations, sampling and thermal conductivity measurements were conducted for seven boreholes at four locations in diverse geological settings. Results of 418 measurements conducted on 82 sediment and rock samples were compiled and analysed in the context of existing collections of thermal conductivities from Germany and Switzerland which are frequently utilized for borehole heat exchanger (BHE) dimensioning in other countries. Discrepancies have been detected between thermal conductivity data from different geographical regions and geological settings. These results imply that local data sets should be further developed to enable accurate BHE sizing. In four of the boreholes thermal response tests (TRTs) were also conducted so the results were compared to direct measurements on samples. The comparison demonstrated that in the environments with significant groundwater flow (coarser-grained sediments) the laboratory measurements systematically underestimated natural-scale thermal conductivities, while the discrepancies were low in finer-grained sedimentary environments. That is why in the presence of significant groundwater flow the TRTs are recommended for all installations, while at locations with low flow velocities the analogy to values cited in data collections can be used for small-scale installations. It is important to have the collection of measurements for local materials in cases when thermal response testing would not be economically feasible. The values reported in this paper can be a guideline for proper GSHP system dimensioning in order to achieve better performance, especially of small-scale systems in Croatia and other geologically comparable localities in the PBS area

Određivanje rasipne reaktancije armaturnog namota sinkronog generatora pomoću signala magnetske indukcije u zračnom rasporu

A new procedure for the armature leakage reactance of the synchronous generator determination is proposed. The procedure is based on measurement of the phase displacement between the fundamental harmonics of the armature voltage and the generator air gap flux density. The accuracy of the algorithm for the phase displacement determination, which is based on Discrete Fourier Transform (DFT), is proved by the laboratory measurement first. After that, measurements on the synchronous generator in HEPP Peruća on Cetina River in Croatia are performed. Two sensors are used for the air gap flux density measurement: the Hall sensor and the measuring coil. To prove the proposed procedure, on the same generator the applied voltage test with rotor removed is performed, too. It is proved that a measuring coil can not be used as the flux density sensor because of the system error due to the air gap field harmonics. On the other hand, when the Hall sensor is used one should pay attention to the voltage noise due to the armature reaction fundamental harmonic. This voltage noise can be minimized by performing measurement at a particular operating point of the generator. The theoretical criterion for determination of this particular operating point is defined in this paper.Definiran je postupak za identifikaciju rasipne reaktancije armaturnog namota koji se temelji na mjerenju faznog pomaka između armaturnog napona i magnetske indukcije u zračnom rasporu generatora. Točnost algoritma za određivanje faznog pomaka, koji se temelji na primjeni diskretne Fourierove transformacije, provjerena je mjerenjima u laboratorijskim uvjetima. Nakon toga provedena su mjerenja na generatoru snage 26 MVA u HE Peruća na rijeci Cetini, Republika Hrvatska, pri čemu su korištena dva senzora magnestke indukcije: mjerni svitak i Hallova sonda. U svrhu eksperimentalne provjere istraživanog postupka na istom generatoru proveden je i pokus s izvađenim rotorom. Pokazano je da se u identifikacijskom postupku ne može koristiti mjerni svitak zbog sustavne pogreške koju uzrokuju prostorni harmonici polja u zračnom rasporu. S druge strane, kod primjene Hallove sonde velik utjecaj na točnost mjerenja može imati smetnja koju izaziva osnovni harmonik reakcije armature. U radu je dana teorijska analiza na temelju koje je pokazano da se može odabrati radna točka generatora u kojoj se ta smetnja minimizira

Characterization of lactic acid bacteria isolated from Bosnian artisanal dry fermented sausage sudzuk) during fermentation

Bosnian sudzuk is a dry fermented sausage produced in a rural household near the town of Visoko in central Bosnia and Herzegovina. This kind of sausage was manufactured only from beef and spices in a traditional way without the addition of a starter cultures. To identify lactic acid bacteria (LAB), a total number of 160 LAB strains were isolated from five samples of Bosnian sudzuk collected over 28 days of fermentation. Preliminary identification by phenotypic tests and 16S rDNA sequencing were performed for all 160 of the LAB isolates. Identification of LAB strains from traditionally produced Bosnian sausage at the species level revealed the presence of six genera: Lactococcus sp., Enterococcus sp., Leuconostoc sp., Lactobacillus sp., Pediococcus sp. and Weissella sp.. Among the 15 distinct species identified, the species Lactobacillus plantarum, Leuconostoc mesenteroides, Lactococcus lactis, Enterococcus faecalis and Enterococcus durans were present throughout the entire process of fermentation. Leuconostoc mesenteroides, Lactobacillus plantarum and Lactococcus lactis prevailed, with 21.8%, 19.3% and 13.1%, respectively, of total LAB strains during the entire fermentation process. Significant negative correlations (r = 0.892 and r = 0.829, respectively) between the presence of Weissella sp. and Lactobacillus sp., and between the presence of Weissella sp. and Lactococcus sp. were recorded. Lactobacillus plantarum, Enterococcus durans and Leuconostoc mesenteroides were the best producers of aromogenic compounds while 32.3% of Lactobacillus plantarum and 28.6% of Leuconostoc mesenteroides were produced exopolysaccharides

Travel intentions in pandemic circumstances - the case of Balkan tourists

Examination of tourist behaviour during and after the crisis is of great importance for understanding and coping with the harmful effects of the crisis. The study aims to discover the impact of perceived risks, health status, and travel experience on proximal travel intentions during the Covid-19 outbreak. Perceived risks that coronavirus brought reshaped the collective awareness and altered typical travel habits. The research involved 1109 respondents from four Balkan countries who participated in an online survey at the first peak of the pandemic (April 2020). According to the results, perceived risk negatively influenced travel intentions. The study presumed the positive influence of previous travel experience on travel intentions and indicated its negative impact on risk perception. Results showed that subjective health condition positively affected travel intention and had no significant effect on risk perception. The profound uncertainty that the tourism sector experienced is primarily reflected in an immense impact on the travel possibilities and changes in tourist preferences. This study offers an insight into peoples’ travel intentions influenced by a global health crisis, reflecting specific risk negation when it comes to the timing of after-crisis travel plans