Hungarian Danube Research Articles

Quantification of bedload transport in the Hungarian Danube using multiple analysis methods

While bedload transport is crucial to river morphodynamics, quantifying it in large rivers, such as the Danube, poses significant challenges. The current study focuses on the gravel-dominated section of the Danube River in Hungary, where multiple methods have been concurrently applied to evaluate bedload transport. In a representative cross section of the river, the following methods were applied: (i) point-wise direct physical sampling using a BfG-type pressure difference sampler, quality controlled with a video camera mounted on the sampler; (ii) indirect acoustic-based analysis with an Acoustic Doppler Current Profiler (ADCP), evaluating the Bottom Tracking signal; and (iii) indirect acoustic and imaging-based method utilizing Acoustic Mapping Velocimetry (AMV). The ADCP method is calibrated using results from the physical sampling, while the AMV method relies on bedform tracking and is entirely independent from the two other techniques. The results from a series of measurement campaigns, covering a wide range of flow regimes, suggest a robust bedload rating curve for the study section, enabling the estimation of bedload yields and its relation to morphological changes. In addition, the applicability conditions of the implemented methods are discussed.

The Incision of the Riverbed on the Upper Hungarian Danube and the Rába, in the Region of the Confluence of the Moson-Danube

The phenomenon of bed subsidence on our channelised rivers is a well-known fact for a long time. In the upper reach of the Danube in Hungary, this process seems to have accelerated in recent decades due to the construction of hydroelectric power plants on the German, Austrian and Slovak sections of the river and other anthropogenic effects. As a result, similar processes are also present in the lower reach of the Moson-Danube and Rába rivers, which are hydromorphologically significantly influenced by the Danube. In our study, we quantify the magnitude and temporal changes of this phenomenon by examining the hydrological time series of the Danube between the gauging stations of Dévény and Komárom and of the Rába between Sárvár and Győr. We estimate its impact on floods, navigation and the safety of drinking water resources.

River regulation, infrastructure, and small-town modernity on the Hungarian Danube, 1870–1945

River regulation, infrastructure, and small-town modernity on the Hungarian Danube, 1870–1945

First report of molecular taxonomic analyses of European beaver metazoan parasites from Hungary

European beaver (Castor fiber L. 1758) is the biggest rodent species living in Europe. Beavers are semi-aquatic animals; they are defecating directly into the water; thus, they have an important role in spreading parasites related to water (e.g., protozoa and flukes). The first specimens of this once extinct rodent species in Hungary turned up in Szigetköz (upper flow of the Hungarian Danube) in 1991 dispersed from Austria. The reintroduction to Hungary started in 1996, and the population slowly increased in number up to around 4000 individuals, but the knowledge about their parasites is lacking. This is the first report on the metazoan parasites of beavers in Hungary and their molecular taxonomy. In the 5-year study, 47 beavers were trapped in four locations and euthanized with permission. Three different metazoan parasites were collected: larvae and adults of Platypsyllus castoris beetles, nymphs and adults of Schizocarpus sp. mites and eggs and adults of Stichorchis subtriquetrus flukes. From these three parasite species, molecular taxonomic studies were also carried out. The low number of metazoan parasites species detected in Hungarian beavers compared to other European countries (e.g., Poland) might be attributed to host population bottleneck effect during reintroduction. As parasites represent a significant component of the biodiversity and ecosystem, the conservation efforts should focus not only on host species but also on their parasites.

How Many Real Islands Have Existed along a Mid-Danube Section during the Past 250 Years?

The consequences of river regulation work and other human interventions from the past can still be followed and cause various effects on the Danube river, especially on the formation and state of the islands. We aimed to compile an inventory of the islands along the Hungarian Danube stretch between Vének (1797 rkm) and Budapest (1647 rkm) during the past 250 years, focusing on their landscape history. Real islands were defined as gravel bars that are permanently covered with pioneer woody vegetation, constantly surrounded by water (side-branch is not closed), and their surface remains unflooded at an average water level. We identified 123 real islands that existed on this 150 km long river stretch in the last centuries. These were real islands for a shorter or longer period between the 18th and the 21st century. A total of 66 of them existed at the same time about 200 years ago, i.e., before the large-scale water regulation works, while today this number is only 18, meaning that 73% of current potential Danube islands are at a stage of side-branch succession. Before the river regulation works, the natural successional changes of a real island occurred over hundreds of years, but today they happen rapidly. The formation of new islands became very limited compared to the past due to the lack of sediments and the altered river dynamics. In order to conserve this unique ecological corridor and green infrastructure element in the long run, and restore its damaged floodplain habitats, no more hard-tech interventions should be allowed in the fluvial system. These aspects need to be taken into consideration in decision-making processes with an integrated approach.

Rapid spread of a new alien and potentially invasive species, Clathrocaspia knipowitschii (Makarov, 1938) (Gastropoda: Hydrobiidae), in the Danube River

We examined the spread and distribution in the Danube River of a new alien gastropod species, Clathrocaspia knipowitschii (Makarov, 1938) (Gastropoda: Hydrobiidae: Caspiinae). First findings of this species for Hungary, Slovakia, Romania, Bulgaria and Serbia are presented. Clathrocaspia knipowitschii was initially found in 2013 in the Iron Gate stretch of the Danube River at the border between Romania and Serbia. In 2019 and 2020, the species was found at several sites in the lower Danube in Romania, Serbia and Bulgaria, and also upstream in the middle Hungarian Danube in high population densities. The species appears to have spread along more than 800 km in six years. This finding together with the available abundance data indicates that C. knipowitschii is potentially an invasive species, but further observations are needed.

A numerical modeling‐based predictive methodology for the assessment of the impacts of ship waves on YOY fish

AbstractThe effects of inland navigation on the aquatic ecosystem are numerous. One of the most relevant impacts from the ecohydraulic point of view is ship‐induced waves, resulting in the local and temporary alteration of the hydrodynamic regime, especially in shallow water areas. In this paper, a novel hydrodynamic modeling‐based evaluation framework is presented and tested for the prediction of habitat use and drift risk of juvenile fish during wave events of different intensities. A vertically resolved numerical wave tank was built up using field measurements of a real vessel‐generated wave event from the Hungarian Danube. High‐frequency pressure time series were utilized to numerically reproduce the phase accurate wave trains, while acoustic Doppler velocity time series were exploited for the verification of the model. Results of the spatiotemporally resolved hydrodynamic model were combined with data from the literature to explore a case study of juvenile Nase (Chondrostoma nasus). Results highlighted the significant horizontal extension (10–15 m) of the area exposed to decreased habitat suitability and increased drift risk. Moreover, the model revealed significant vertical variabilities in the investigated near‐bank area as well, emphasizing the relevance of depth resolved hydrodynamic modeling in ecohydraulic investigations.

Image-Based Bed Material Mapping of a Large River

The composition or bed material plays a crucial role in the physical hydromorphological processes of fluvial systems. However, conventional bed material sampling methods provide only pointwise information, which can be inadequate when investigating large rivers of inhomogeneous bed material characteristics. In this study, novel, image-based approaches are implemented to gain areal information of the bed surface composition using two different techniques: monocular and stereo computer vision. Using underwater videos, captured in shorter reaches of the Hungarian Danube River, a comparison of the bed material grain size distributions from conventional physical samplings and the ones reconstructed from the images is carried out. Moreover, an attempt is made to quantify bed surface roughness, using the so-called Structure from Motion image analysis method. Practical aspects of the applicability of image-based bed material mapping are discussed and future improvements towards an automatized mapping methodology are outlined.

The Ponto-Caspian mysid Paramysis lacustris (Czerniavsky, 1882) has colonized the Middle Danube

In 2017, the mysid Paramysis lacustris (Czerniavsky, 1882) was found for the first time in the Hungarian Danube section, representing the first psammo-pelophilous Ponto-Caspian peracarid colonizing the Middle Danube. In 2018, a brief survey focusing on this species revealed its presence in a more than 500-km-long river section spanning from Austria (Vienna, river km 1926) to Croatia (Batina, river km 1425). The largest populations of P. lacustris might be formed in reservoirs and slow-flowing stretches, where the appearance of the species might imply a considerable impact in connection with its zooplanktivorous feeding and important role in the diet of fish. Similar to all the other Ponto-Caspian peracarids that have crossed the Middle Danube, P. lacustris can reasonably be expected to continue its spread toward Western Europe in the future.

Long-term changes in copepods assemblages in the area of the Danube floodplain (Slovak–Hungarian stretch)

The present study investigates the relationship between hydrological connectivity and species diversity in a by-passed channel section, and in the adjacent water bodies of the Slovak–Hungarian Danube section (1,840.5–1,804.4 rkm). The study was designed to assess long-term temporal trends (from 1991 to 2013) in freshwater copepods assemblages and their ecological indices in different habitats of the Danube floodplain area. One of the purpose of this study was to monitor the species composition of copepods communities and ascertain their shift in various biotopes of the Danube floodplain system. Based on 23 years data, in the first step, the copepods habitat preferences using habitat values (HV) and indicator weights (IW), calculated from data collected over all the years of monitoring of planktonic communities of the Danube floodplain, were quantified. Subsequently, the floodplain index (FI) from a summary of the habitat values and indication weights of the current species was calculated, to evaluate changes in the connectivity of the anabranched section of the Slovak–Hungarian Danube. This confirmed the loss of active hydrological connectivity within the main river channel, ranging from the eupotamal to more or less isolated floodplain water bodies. Out of 50 recorded copepods species, 11 species manifest a preference for eupotamal habitats, 18 taxa preferred eupotamal B/parapotamal habitats and 21 species were found to prefer the plesiopotamal habitat type. The statistical analyses demonstrated that the structure of planktonic copepod communities in this area has changed since the Gabčíkovo hydropower plant was placed into operations. The NMDS analysis revealed shifts in the proportion of euplanktonic and tychoplanktonic species. Reversible community changes were found in the old river bed and in the eupotamal-B side arms.

Morphological Investigation of a Critical Reach of the Upper Hungarian Danube

The aim of this study is to analyze the current morphological changes and to predict the potential future trends of a critical reach of the upper Hungarian Danube River. In this section of the river the morphological features have undergone significant changes, mainly due to human impacts, such as the construction of the Gabcikovo hydropower plant close to the Slovakian border, or the river regulation measures with groin fields along the Hungarian reach. The morphological changes of the river inherently led to river management issues, e.g. the developed gravel bars caused problems for inland navigation. In order to reveal and understand the characteristic morphodynamic processes, results from past bed geometry surveys were assessed, moreover, extensive field measurement campaigns were carried out, including bathymetry survey, flow survey with fixed and moving Acoustic Doppler Current Profiler (ADCP), bed material sampling and bedload measurements. The utilization of up-to-date field data processing methods provided essential information on the current dominant morphological processes and finally, suggestions were made on the stability of the river planform.

Efektivita umelého vysadzovania jesetera malého (Acipenser ruthenus, Linneaus 1758) do slovensko­‑maďarského úseku Dunaja

Efektivita umelého vysadzovania jesetera malého (Acipenser ruthenus, Linneaus 1758) do slovensko­‑maďarského úseku Dunaja

A New Species of the Gobiidae Family in Transylvania Waters: Racer Goby (Babka gymnotrachelus, Kessler 1857)

The racer goby (Babka gymnotrachelus) is one of the well represented Ponto-Caspian goby species in most Danube Delta Biosphere Reserve lakes and channels, including Razim-Sinoe lagoon complex and lower sector of the Danube. Also, the presence of this species is noted in some lakes near Bucharest. The presence of this species in Transylvania has not been reported until now, when our team, while conducting ichthyologic investigations, captured seven specimens from Someș River and some of its tributaries, as follows: one specimen was caught in a channel adjacent to Țaga Mare Lake, one specimen was caught in Someşul Mare River (Mica village, Cluj County), two specimens were captured from the confluence of the Someşul Mic River and Fizeș River. Another two specimens were captured from Fizeş River (Fizeşu Gherlii village, Cluj County) and the last one was also caught from the Fizeş River (Sântioana village, Cluj County). It is possible that the species migrated in Someş Catchment from the Hungarian Danube sector, by the tributaries of Tisa River, or it might have originated from stocking material used in fish farms in Transylvania.The somatic, gravimetric and meristic measurements of the collected specimens were taken in the Acquaculture and Acquatic Organisms Phisyology laboratories from the University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca and correspond with those mentioned in the published literature regarding this species.

Trophic Status and Phytoplankton Limitation Conditions in a Few Bulgarian and Hungarian Danube River Wetlands

AbstractThe phytoplankton limitation conditions in a few Bulgarian and Hungarian wetlands and in two more sampling sites, one for each Danube stretch, were investigated by means of trophic state index of Carlson (1977) for phytoplankton chlorophyll-a (CHL), Secchi disk depths (SD), total phosphorus (TP), and total nitrogen (TN) concentrations. Phytoplankton of both river sites was not limited by non-algal turbidity, nor was they phosphorus and nitrogen limited. In summer months the studied wetlands were predominantly nitrogen limited, while in spring and autumn limitation by non-algal turbidity prevailed.

Bacterioplankton from Two Hungarian Danube River Wetlands (Beda-Karapancsa, Danube-Drava National Park) and its Relations to Environmental Variables

Abstract Seasonal and spatial distribution of bacterioplankton from two Hungarian oxbow lake type wetlands, Mocskos-Danube and Riha, was studied. They were both covered by macrophytes and they had different hydrological connectivity to the Danube. The six sampling campaigns from April to October 2014 included parallel samples from the Danube River at Mohács, Hungary. Bacterial abundance was the highest in spring and in Mocskos-Danube, followed by Mohács and Riha. Positive relationships existed between bacterioplankton and temperature on one hand and suspended solids, pH, PO4-P and chl-a on the other. Negative correlations were with DOC, dissolved oxygen and NH4-N.

Tectonic and climatic control on terrace formation: Coupling in situ produced 10Be depth profiles and luminescence approach, Danube River, Hungary, Central Europe

The terrace sequence of the Hungarian part of the Danube valley preserves a record of varying tectonic uplift rates along the river course and throughout several climate stages. To establish the chronology of formation of these terraces, two different dating methods were used on alluvial terraces: exposure age dating using in situ produced cosmogenic 10Be and luminescence dating. Using Monte Carlo approach to model the denudation rate-corrected exposure ages, in situ produced cosmogenic 10Be samples originated from vertical depth profiles enabled the determination of both the exposure time and the denudation rate. Post-IR IRSL measurements were carried out on K-feldspar samples to obtain the ages of sedimentation.The highest terrace horizon remnants of the study area provided a best estimate erosion-corrected minimum 10Be exposure age of >700 ka. We propose that the abandonment of the highest terrace of the Hungarian Danube valley was triggered by the combined effect of the beginning tectonic uplift and the onset of major continental glaciations of Quaternary age (around MIS 22). For the lower terraces it was possible to reveal close correlation with MIS stages using IRSL ages. The new chronology enabled the distinction of tIIb (∼90 ka; MIS 5b–c) and tIIIa (∼140 ka; MIS 6) in the study area. Surface denudation rates were well constrained by the cosmogenic 10Be depth profiles between 5.8 m/Ma and 10.0 m/Ma for all terraces. The calculated maximum incision rates of the Danube relevant for the above determined >700 ka time span were increasing from west (<0.06 mm/a) to east (<0.13 mm/a), toward the more elevated Transdanubian Range. Late Pleistocene incision rates derived from the age of the low terraces (∼0.13–0.15 mm/a) may suggest a slight acceleration of uplift towards present.

Freshwater mollusc assemblages and habitat associations in the Danube River drainage, Hungary

Abstract Native freshwater mollusc diversity has been declining over the past decades. For developing efficient conservation management plans for molluscs, it is especially important to identify areas with high native biodiversity. The River Danube is one of the most important freshwater ecosystems in Europe and should receive special attention. The main objective of this work was to characterize the composition, diversity and conservation status of freshwater molluscs occurring in the Hungarian Danube River Drainage in five river habitat types (main channel of the Rivers Danube and Tisza, side channels of River Danube, tributaries of Rivers Danube and Tisza). In total, 53 mollusc species were identified including 10 invasive species and 12 species of conservation concern. The main determining factors of mollusc composition were sediment characteristics, current velocity and oxygen content. Nitrate–nitrogen, ammonium–nitrogen, and calcium content also play a key role. Overall, density, species richness and diversity showed significant differences between habitat types. The highest diversity values were detected in the side channels, but the highest proportion of threatened species was observed in the tributaries. The highest number and proportion of invasive species was detected in the main channel of the Danube. Most of the recorded invasive species were previously documented in side channels and the adjacent wetlands, but did not invade the tributaries. Tributaries may provide refuges for native molluscs and could be considered as ‘source’ populations, which may be critically important in the regional maintenance of threatened species. Tributaries are still less disturbed and less invaded; and should be given priority in future conservation management plans. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Fish remains as a source to reconstruct long-term changes of fish communities in the Austrian and Hungarian Danube.

The main objective of this paper is to investigate how archaeological fish remains and written historical records can contribute to the reconstruction of long-term developments of fish communities along the Austrian and Hungarian Danube. Although such approaches are sensitive to various factors, the chronological subdivision and relative quantification of proxy data demonstrate environmental and faunal changes from Prehistory onwards. Intensification of fisheries, decline of large specimens and massive exploitation of small and young fish point to increasing pressure along the chronological sequence towards Early Modern times. One result of this impact was the establishment of regulations and laws to protect such fish. At the same time, the rise of aquaculture and common carp cultivation can be viewed as another upshot of human impact on the Danube’s environment. Finally, the massive import of salted marine fish reflects a compensation for the undersupply caused by overexploitation of the Danube fish fauna and points to the growing demand for fish as food in late medieval and Early Modern times.

Spatial distribution of bivalves in relation to environmental conditions (middle Danube catchment, Hungary)

The spatial distribution of bivalves in relation to environmental conditions was studied along a second- and third order stream — medium-sized river (River Ipoly) — large river (River Danube) continuum in the Hungarian Danube River system. Quantitative samples were collected four times in 2007 and a total of 1662 specimens, belonging to 22 bivalve species were identified. Among these species, two are endangered (Pseudanodonta complanata, Unio crassus) and five are invasive (Dreissena polymorpha, D. rostriformis bugensis, Corbicula fluminea, C. fluminalis, Anodonta woodiana) in Hungary. The higher density presented by Pisidium subtruncatum, P. supinum, P. henslowanum and C. fluminea suggests that these species may have a key role in this ecosystem. Three different faunal groups were distinguished but no significant temporal change was detected. The lowest density and diversity with two species (P. casertanum and P. personatum) occurred in streams. The highest density and diversity was found in the River Ipoly, in the side arms of the Danube and in the main arm of the Danube with sand and silt substrate, being dominated by P. subtruncatum and P. henslowanum. Moderate density and species richness were observed in the main arm of the Danube with pebble and stone substrate, being dominated by C. fluminea and S. rivicola. Ten environmental variables were found to have significant influence on the distribution of bivalves, the strongest explanatory factors being substrate types, current velocity and sedimentological characteristics.

The importance of clonal selection of grapevine and the role of selected clones in production of healthy propagating stocks

Genetical alterations and phytosanitary status promote the variability and modify the appearance of vine. Old vine varieties in old vineyards are highly variable and well adapted to selection. Clonal selektion is based on a visual performance: valuable individuals (clones) are picked out according to visible symptoms or characters. The genetical stability of clones is proved by testing the vegetatively propagated progenies on the basis of morphological and molekular (SSR, AFLP, SMPL, RAPD) markes. Authors take great care of the visual phytosanitary selection as part of the clonal selection being the oreliminary step to develop pathogen-free propagation stocks. In Serbia (Vojvodina) the selection breeding has been carried on for several decades resulted in comparative clone trials with home and imported clones of Welsch Riesling, Chardonnay, Pinot gris, White Riesling. Among the clones of home selection SK.54 Welsch Riesling clone is the most valuable. Its clearing from pathogene is being carried on in an interregional IPA programme (HUSRB/0901/214/123) in Kecskemét. In Kecskemét, the centre of the Hungarian Danube vine region 5 vine clones have been registered (Cegléd szépe K.73, Irsai Olivér K.11, Kövidinka K.8, Hárslevelû K.9, Pannónia kincse K.56). Besides them 18 virus-tested clones have also been qualified.Works aiming at their complete exemption are going on in order to obtain clones free of propagation wood-borne diseases.