Dinaric Karst Research Articles

Drastic hydrological changes caused by hydroelectrical development in karst: a case of the karst river Zrmanja (Croatia)

This paper has analysed changes in the hydrological regime along the karst river Zrmanja (the Dinaric karst of Croatia) caused by operation of the reversible or pumped-storage hydroelectric power plant Velebit (RHEPP Velebit), which started operations in 1985. The total river length from the spring to the mouth in the Adriatic Sea is 70 km. Discharges along the whole river course are monitored at nine hydrological gauging stations. For all nine analysed stations, the decrease of the mean annual discharges starting from 1985 has proven to be statistically significant. However, it should be stressed that the Zrmanja River natural regime is extremely complex due to a deep, well developed and generally undiscovered subsurface karst morphology and its influence on regional surface and groundwater circulation. The influence of RHEPP Velebit operation on the maximum annual discharges is not statistically significant. Statistically significant decrease on the minimum annual discharges is observed at only one gauging station located at the Zrmanja River downstream of the Razovac Reservoir. At the same time, climatological changes have been monitored in the analysed area. It has been established that there has been an annual increase in air temperature since 1988 and an annual decrease in rainfall since 1983. A general conclusion is that the decrease in the mean annual discharges along the Zrmanja River is mainly caused by the RHEPP Velebit operation and only in a smaller degree by climatological changes. On the basis of the available data it was not possible to separate precisely the influences of these two factors.

Karst spring catchment: an example from Dinaric karst

Definition of karst spring catchment or basin area and boundaries belongs to one of the greatest prob- lems of karst hydrology and hydrogeology, not adequately solved until now. This paper tries to address main problems in defining this crucial parameter. The theoretical aspect of this issue is discussed in the first two chapters. We have presented the example of the catchment area and bound- aries definition for the karst spring Zrnovnica catchment in Dinaric karst. Topographic catchment area of the Zrnov- nica Spring is 8.4 km 2 . The significant discrepancy in size of the hydrological-hydrogeological and topographical catchment is very common characteristic for the springs located in the karst areas. In the case of the Zrnovnica Spring, the hydrogeological catchment is at least seven times larger than topographic. Two following simple hydrological methods are used in order to calculate its hydrologic-hydrogeologic catchment: (1) the relationship between mean annual discharges and annual rainfall falling on the catchment, and (2) the Turc method. It is estimated that hydrogeologic catchment area of the Zrnovnica karst spring is much larger and very probably ranges between 60 and 80 km 2 . These values represent first rough assessment, which should be confirmed by more detailed interdisci- plinary investigations. According to the performed tracing tests, it seems that the catchment spreads on the north-east from the topographic catchment and that the Zrnovnica Spring karst aquifer is fed by groundwater overflow from the neighbouring more abundant karts spring Jadro.

An example of karst catchment delineation for prioritizing the protection of an intact natural area

The karstic spring Perucac as the main drainage area of the Tara Mt. in western Serbia was studied in order to assess its discharge regime, water reserves, and to delineate its catchment area. The spring is located in the northeastern, inner zone of the classic Dinaric karst, which is characterized by a dominant extension of highly karstified Triassic limestones, a poorly developed hydrographic network with many ponors, and dense forests. Tara Mt. is one of five national parks in Serbia. The goal of the project was to identify a high-priority protection zone within the preserved natural area which is also well known and actively used for tourism and recreation purposes. Based on data on the discharge regime of the Perucac Spring, and by applying the multiple non-linear correlation method, the size of the direct catchment area was assumed to be 79.3 km2, which was 5–18 % larger than that estimated by previous surveys. Proposal to extend preserved natural area and to include sanitary protection zone of the Perucac spring as well as to establish a common monitoring system for biodiversity and water has been made. In this way, not only native plants and animals but also their habitats would be better protected from potential pollution.

The Morphology of Male Gonads of the Neotenic Cave Salamander (Proteus anguinus)

Proteus anguinus is a cave‐dwelling urodele amphibian that is endemic to underground waters in Dinaric karst regions of Central Europe. It is an obligate neotene, with a very long life span and late sexual maturity. The reproductive period is a‐seasonal and lasts at least 30 years with each female laying eggs at intervals of 6 ‐ 12.5 years. The objective of this study was to describe the morphology of the testes of Proteus for better understanding of the reproductive strategy of this neotenic cave amphibian with the long‐term goal of establishing a facility for captive breeding. The testes used for this research were removed from our permanent collection of archived specimens. At least three morphological forms of testes are present independent of the size of the specimens, most likely representing phases of maturation of the gonads. The internal histological structure the testis is a simple cystic type of cyts enclosed in lobules with synchronous maturation of the germ cells within each cyst. The development of cysts inside a particular lobule is either synchronous or asynchronous. Spermatogenesis progresses in caudo‐cephalic direction of the testis as well as in proximal‐distal direction in relation to internal collecting ducts and appears to be independent of the seasons of the year. We can conclude that the reproductive peculiarities in Proteus probably reflect the fact that it lives in a relatively stable habitat with environmental conditions that are conducive to a‐seasonal reproductive cycles, similar to tropical salamanders. This research was supported by a grant from the Ministry of Higher Education, Science and Technology, Republic of Slovenia (P1–0184).

Geomorphological significance of the palaeodrainage network on a karst plateau: The Una–Korana plateau, Dinaric karst, Croatia

Karst plateaus often have a complex geological and geomorphological history. It is widely accepted that their development requires a long period of karst denudation. This study reconstructs the palaeodrainage network of a karst plateau, analyses its properties and establishes its geomorphological significance. The main purpose of this research was to deepen our understanding of a key stage in the evolution of karst plateaus — the transition from a fluvial land surface to one dominated by karst surface processes. The study was conducted on a large part of the Una–Korana plateau, the largest plateau in the Dinaric karst. The majority of the plateau is made of carbonate rocks of Triassic, Jurassic and Cretaceous age that set the conditions for the development of the karst. We have reconstructed the palaeodrainage network based on 1:25,000 topographic maps with 10m contours. The transition of the surface drainage network to the underground karst drainage network is still in progress, so, depending on the degree of karstification, the drainage network was divided into three categories: active, dry and relict. It was found that 90.5% of the pre-existing drainage network has undergone some degree of karstification. The active surface drainage network gradually shifted to a dry network, then to a relict network. The surface drainage network is gradually replaced by a dense network of dolines. Today, the flat and karstified inter-fluvial area is drained underground towards the main watercourses and these drain the entire region over the surface towards the Pannonian basin. This is the largest known karst palaeodrainage network in the Dinaric karst that has been reconstructed in this way.

Hydrogeology of the Skadar Lake basin (Southeast Dinarides) with an assessment of considerable subterranean inflow

The Skadar Lake basin is located in the south-eastern part of the classical Dinaric karst region (northern Mediterranean). This region is well known for its highly developed karst and the presence of all types of karstic features. In addition to the high degree of karstification, the advantage of Skadar Lake’s catchment area in terms of water resources is also reflected in the following factors: a large amount of precipitation, scarcity of soil and vegetation cover, favourable geological and geomorphological conditions for karst aquifer discharge, the isolation of the Skadar basin from the influence of the Adriatic Sea and an availability of water for simple abstraction. For the purposes of a more complete determination of the water balance of Skadar Lake, among other undertakings, it has been necessary to determine the groundwater inflow to the lake through numerous sublacustrine springs (vruljas). By using thermal infrared satellite and terrestrial imaging, the locations of the largest sublacustrine springs have been detected and their yield assessed by means of water balance calculation after the application of the KARSTLOP method. The mean annual groundwater inflow to the lake, from the south-western edge only, is 9.86 m3/s. The total outflow of water from the lake through the Bojana River is around 304 m3/s. The coincidence of several important natural factors leads to the large average specific yield (surface and subsurface) in the Skadar Lake catchment area (54 l/s/km2), which makes this region one of the richest areas of freshwater in the world.

Morfogeneza kr�kih polja na otoku Visu, Hrvatska

Karst poljes are the most characteristic feature of Dinaric karst area. The number of poljes identified on the island of Vis (Croatia) differs according to the various authors who have studied the island. Considering the various existing definitions of polje in previous studies, in this paper we propose a set of criteria for identifying poljes in karst terrain using Geographic Information System. This enabled the identification of six poljes on the Vis Island, whose formation is predetermined by tectonic structures. Moreover, processes are frequently inferred by neotectonic (both uplift and subsidence) according to the analysis of longitudinal and transverse profiles gradients affecting balance of these morphologies. Since they are not hydrologically active in present hydrological conditions, poljes on Vis Island can be considered to be paleo - overflow or structural poljes.

Morphological study of Red lake in Dinaric karst based on terrestrial laser scaning and sonar system

Red Lake (Dinaric karst, Croatia) is an exceptional karst phenomenon, worldwide known for its beauty and extreme depth. Even so, through the history of Red Lake’s research there were many controversies in the conclusions and the theories concerning its genesis, geomorphology and hydrology. The aim of this work is to give an overview of existing findings about Red Lake as well as to present the newest research results gained with the help of emerging technologies based on terrestrial laser scanning and hydro acoustics. The measuring was conducted during September 2013. A new generation of equipment developed to advance the geoscientific research was deployed during the field work. The gathered data enabled a thorough analysis which led to new important findings on Red Lake. Deployment of Remotely operated underwater vehicle (ROV) equipped with imaging sonar resulted in the first hydro acoustic survey of the lake. Some of the results confirmed the already known and well documented characteristics of Red Lake whereas others disputed the widely accepted assumptions in the scientific community and the general public. The presented research generated, for the first time, a DEM for Red Lake which allowed a good estimate on the lake’s volume. For the recorded maximum water level at 311 m a.s.l. the volume of water stored is 8.24 x 106 m3. A temperature profile of the lake was recorded during the field work and it offered an insight on possible water mixing through karst conduits near the surface of the water. The application of TLS and ROV sonar systems considerably improved the understanding of Red Lake’s morphology.

Vulnerability and protection aspects of some Dinaric karst aquifers: a synthesis

The present paper aims to address the sustainable management issues of karst water sources in Slovenia and Croatia. It focuses on the Mediterranean part of the Dinaric karst, which holds important groundwater reserves. The importance of selected karst aquifers for water supply is presented. In addition, national drinking water management strategies are examined to synthesise the issues relating to the exposure of groundwater to contamination and over-exploitation. Finally, the most significant problems, pressing needs and challenges are identified. These depend predominantly on revision of existing drinking water protection strategies and integration of karst-specific provisions, aspects of over-exploitation and proper water quality control. The need for harmonised multi-country policies regulating resource abstraction and contamination issues is stressed.

Karst of eastern Herzegovina, the Dubrovnik littoral and western Montenegro

As the region of Eastern Herzegovina and the Boka Kotorska (Kotor Bay) area is one of the most highly karstified areas in the world, its hydrogeological properties, typical for karst, are extremely exposed. The main erosion base-levels for surface and underground waters of that region are: the Neretva River valley in the west, the Adriatic Sea and Dubrovnik littoral in the south and Boka Kotorska in the east. At the same time it belongs to one of the most investigated karst regions in the world known as the Dinaric Karst. The basic theories related to the nature of karst are based on the multidisciplinary and long-lasting investigation of this particular region. World famous karstologists such as Cvijic, Grund, Katzer and many others created crucial theories of karstology based on investigations and analysis of the Dinaric Karst. Many large and successfully constructed structures (dams, reservoirs and tunnels) of the region also became the basis for the development of engineering karstology. Massive karst investigation works were also performed during the twentieth century. The accumulated data and knowledge have been presented at many scientific conferences and has also appeared in many publications. The text below presents in brief, the general natural properties of the region and represents only a small part of the available data.

Japage: udornice na Kupreškem polju, Bosna in Hercegovina

Kupreško polje se nahaja na dinarskem krasu v zahodni Bosni in Hercegovini. V bližini severovzhodnega roba polja leži skupina udornic, ki se imenujejo japage. Rezultati raziskave so pokazali, da je razporeditev te skupine udornic pogojena s kamninsko sestavo, ki je vplivala na razvoj jamskega sistema, ki spodkopava material pod udornicami. Prisotnost spodkopavanja in prav tako površinske rečne akumulacije sta bistveno vplivala na oblikovanost dnov udornic.

Freshwater biodissolution rates of limestone in the temperate climate of the Dinaric karst in Slovenia

Dissolution rates in two freshwater karst systems were determined by using tablets of dense micrite–biopelmicrite Cretaceous limestone. Submerged limestone tablets in riverbeds were subjected to a natural gradient from complete darkness to direct sunlight. Higher light rates significantly (p<0.05) increased the epilithic biomass of phototrophs and the overall dissolution rates, which were highest at the Unica spring (−49.2μma−1), but the exact portion of light-dependent dissolution remains elusive. In the karst river Unica, with its big fluctuations in environmental parameters (e.g., discharge), light rates can be used in estimating the dissolution rates enhanced by phototrophs. Natural biofilms in aquatic systems have important implications for landform evolution, and the impact on limestone dissolution rates is comparable with rates of debris falling from steep slopes.

Karst hydrogeology/hydrology of dinaric chain and isles

This paper gives a comprehensive explanation of the hydrogeological and hydrological characteristics of different water occurrence, which exists in the extremely complex Dinaric karst system. The area and boundaries of the Dinaric karst have never been precisely determined. It covers about 60,000 km2 stretching the length of the eastern coast of the Adriatic Sea, from the Bay of Trieste in the north, to the Drim River basin in the south, and the Western Morava River valley in the east. Due to very high infiltration rates, overland and surface flows are rare in comparison with non-karst terrains. The Dinaric karst is an extremely heterogeneous medium which can be explained only by the use of a great number of measurements points and by continuously monitoring and measuring different parameters. The hydrogeological and hydrological regime of all water phenomena in the Dinaric karst depends mostly upon the interaction between groundwater and surface water. The dominant flow of the groundwater contained in the Dinaric karst is towards the Adriatic Sea through rivers and many permanent and intermittent coastal and submarine springs. The paper presents many examples of karst water phenomena from the Dinaric karst: (1) springs (Jadro, Ombla and Crnojevica Springs); (2) open streamflows (Ljubljanica, Pazincica, Dobra, Lika, Gacka, Krka, Zrmanja and Cetina Rivers); (3) lakes and wetlands (Cerknica, Vrana, Plitvice, Vransko, Red and Blue Lakes); and (4) coastal and island karst (Brac Island).

Aquatic insects along environmental gradients in a karst river system: A comparative analysis of EPT larvae assemblage components

Studying the response of assemblages either tonatural or human induced environmental gradients is challenging due to spatial and temporal heterogeneity in river systems. This study identified the relationship between environmental variables, as well as sampling date, and Ephemeroptera (E), Plecoptera (P), Trichoptera (T) assemblages in a karst river system. Each assemblage component (E, P, T, EP, ET, PT, and EPT) is analyzed separately. Ten direct influential variables (water depth, water temperature, current velocity, dissolved oxygen concentration, oxygen saturation, pH, nitrate concentration, total solids, and total suspended solids) and sampling date were considered in order to identify environmental gradients after removal of the effect of stream size and habitat heterogeneity; both parameters were used as covariables. Thus, the observed effects of selected 10 variables were those that were not explained also by Strahler stream order and habitat heterogeneity. Examination of the EPT assemblage characteristics using the non-parametric Kruskal–Wallis test showed significant spatial variations in richness/diversity metrics (number of EPT taxa, Shannon–Wiener diversity) but not in functional metrics (Gatherers/Collectors, Grazers, and Scrapers). The temporal variation in all metrics was substantial. Assemblage variances (R 2 ) and adjustedassemblagevariances (R 2 adj )of>35% and>20%,respectively, were obtained. Main environmental gradients representing hydrogeology and eutrophication as well as hydraulic and oxygen gradient for EPT assemblages were recognized. It appears that eutrophication is the key ecological factor for most assemblage components in a Dinaric karst river system, although Plecoptera assemblages were best explained by temperature regime and oxygen conditions. This studysuggeststhatavariationinthediversity betweenE,P,andTtaxainfluences anassemblage– environment relationship. Environmental variables that were best predictors for assemblages with more than one insect group were associated with assemblages with high diversity. This study provides methods and approaches to recognize the main factors determining biotic assemblages’ structures in Dinaric karst river systems and thus provides a basis to develop appropriate biodiversity conservation policies.

Hydrogeological properties of a complex Dinaric karst catchment: Miljacka Spring case study

Miljacka is a karst spring situated in Dalmatia, Croatia. The interpretation of the Miljacka Spring catchment area boundary has repeatedly changed in the past, and the main conclusions of previous studies were that the spring, which is located in the Krka River canyon, receives all of its water from another karst river, Zrmanja. Here, we review a new hypothesis that the Miljacka Spring receives some of its water from the Krka River. It was not possible to verify the hypothesis by solely studying the geological composition, structural–tectonic relations and tracer test results. Therefore, a hydrochemical study was performed to confirm the hypothesis. By studying the geological composition, it was found that part of the catchment area of the Krka River is built of evaporites (gypsum and anhydrite), which are different in their mineral composition than carbonates, the usual rock mass of the Dinaric karst. The hydrochemical model was made using the NETPATH-WIN and PHREEQC software packages. The mixing model results confirmed the hypothesis that the Miljacka Spring waters come from both the Zrmanja (including smaller proportion of precipitation infiltrated directly in the karst aquifer) and Krka rivers. This case study shows the great importance of the application of hydrochemical investigations in karst hydrogeology, where research is often difficult due to the complexity of the groundwater system.

Magnetic spherules in sediments of the karstic Dobra River (Croatia)

Purpose The paper describes an unusual finding of magnetic particles in stream sediments of the karstic Dobra River (Croatia). It aims to investigate the magnetic susceptibility properties of river sediments and to find links with their mineralogical and chemical composition. The goal of our research was to suggest the possible origin of magnetic particles in the river sediments within the Dinaric karst region, which to our knowledge was not exposed to metal manufacturing processes.

Geochemical and stable isotopic variability within two rivers rising under the same mountain, but belonging to two distant watersheds

Complementary geochemical and stable isotope investigations of the Gorski Kotar karst aquifer system in western Croatia were obtained for the first time, to answer the question whether both studied rivers drain the same aquifer system or not. The two main rivers, the Kupa and the Rječina, rise under the same mountain range, but belong to two different watersheds (Black Sea and Adriatic Sea). The karst aquifer of Gorski Kotar is a potentially important source of drinking water for two neighboring countries, Croatia and Slovenia (Central and South Europe), and is strongly influenced by both Mediterranean and continental weather conditions. It is a part of the Dinaric karst, which is “locus typicus” for karst worldwide and one of the most typical karst areas in the world.To answer the main question of our research, baseline data were thoroughly collected comprising stable isotopes, concentration of dissolved and total trace metals in water, and multi-elemental analyses of river sediments, together with other physical-chemical parameters (pH, dissolved oxygen, electric conductivity and temperature). Total dissolved solid (TDS) was not measured but estimated as (EC) 0.67. Such multi-technique approach was applied for the first time in the Dinaric karst systems.Multi-elemental analysis of fine sediment fraction (<63μm) of eight samples was performed by ICP-MS. Elemental composition of sediments is quite different in the two studied river valleys, which indicates different origin of their waters. Also, concentrations of selected metals were compared with existing sediment quality criteria and anthropogenic influence is evaluated and discussed.Analytical results of major ions determined in three springs (Kupa spring, Rječina spring, Zvir spring in the City of Rijeka) were used to construct a Piper diagram, which showed that they are of a Ca–Na–HCO3–Cl type. The highest concentration of Mg is present in the Kupa spring, while the highest concentrations of Na and Cl are present in the Zvir spring. Groundwaters are underlain by limestone, less by dolomite and are under a maritime influence. There is a big difference with the main groundwater types reported in North Africa, i.e. in the south Mediterranean Sea, where two main groundwater types are Na–Cl and Ca–SO4–Cl.Concentrations of total and dissolved fractions of trace metals in surface water samples were determined by voltammetry and compared to the European Water Framework Directive values. Concentrations of total Pb and Zn are significantly higher in the water of the Kupa spring than the Rječina spring, suggesting that the karst water bodies of the two springs are not of the same origin.In addition, stable isotope composition (deuterium and oxygen-18) was determined in the spring waters sampled during low and high water conditions. Due to the significant difference in oxygen isotope-ratios it was concluded that the karst reservoir for the Kupa and Rječina springs is not identical.The results obtained from the combination of physical–chemical, geochemical (water and sediment) and isotope multi-technique analyses pointed out that even though the springs of the Kupa and Rječina rivers originate from the same mountain range, they do not drain the same karst aquifer.

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.

Hydrology of Blue Lake in the Dinaric karst

AbstractThe aim of this paper is to analyse hydrological measurements obtained from Blue Lake located near the town of Imotski (Croatia), during the period from 6 November 2009 at 10:26 h to 4 September 2010 at 03:26 h (7230 h or 302 days). The water depth, water temperature and electrical conductivity of the water were continuously measured during this period. The measurements were obtained with a CTD DIVER (Schlumberger Water Services). The instrument was fixed at the bottom of Blue Lake, which means that all the measured data refer to a single point of measurement. The data represent the first systematic and continuous monitoring of the hydrological parameters of this fascinating karst phenomenon. The hydrological analysis also involved daily rainfall data and daily mean air temperatures recorded at the nearby Imotski meteorological station. The rate of water level rise and fall and the hourly and daily average inflow and outflow into and from the lake were calculated using the available data. The analysis led to the conclusion that Blue Lake is mainly recharged by water coming from the karst aquifer, the dimensions and the characteristics of which have not yet been adequately studied. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Evolutionary history of relict Congeria (Bivalvia: Dreissenidae): unearthing the subterranean biodiversity of the Dinaric Karst

BackgroundPatterns of biodiversity in the subterranean realm are typically different from those encountered on the Earth’s surface. The Dinaric karst of Croatia, Slovenia and Bosnia and Herzegovina is a global hotspot of subterranean biodiversity. How this was achieved and why this is so remain largely unresolved despite a long tradition of research. To obtain insights into the colonisation of the Dinaric Karst and the effects of the subterranean realm on its inhabitants, we studied the tertiary relict Congeria, a unique cave-dwelling bivalve (Dreissenidae), using a combination of biogeographical, molecular, morphological, and paleontological information.ResultsPhylogenetic and molecular clock analyses using both nuclear and mitochondrial markers have shown that the surviving Congeria lineage has actually split into three distinct species, i.e., C. kusceri, C. jalzici sp. nov. and C. mulaomerovici sp. nov., by vicariant processes in the late Miocene and Pliocene. Despite millions of years of independent evolution, analyses have demonstrated a great deal of shell similarity between modern Congeria species, although slight differences in hinge plate structure have enabled the description of the two new species. Ancestral plesiomorphic shell forms seem to have been conserved during the processes of cave colonisation and subsequent lineage isolation. In contrast, shell morphology is divergent within one of the lineages, probably due to microhabitat differences.ConclusionsFollowing the turbulent evolution of the Dreissenidae during the Tertiary and major radiations in Lake Pannon, species of Congeria went extinct. One lineage survived, however, by adopting a unique life history strategy that suited it to the underground environment. In light of our new data, an alternative scenario for its colonisation of the karst is proposed. The extant Congeria comprises three sister species that, to date, have only been found to live in 15 caves in the Dinaric karst. Inter-specific morphological stasis and intra-specific ecophenotypic plasticity of the congerid shell demonstrate the contrasting ways in which evolution in the underground environments shapes its inhabitants.