A source to sink system describes the natural link between mountains, plains and deltas, by analysing the (re)distribution of material at shallow crustal depth and at the Earth's surface, exploring ...the links between coupled tectonic and surface processes. Sediment fluxes are the product of erosion and movement of material in and from sources (mountains), the transport and movement of sediments and solutes by river systems to the plains, and deposition and storage in sink zones. The ESF-EUROCORES TOPO-EUROPE SourceSink programme is a fully integrated research effort to significantly advance our predictive capabilities on the quantitative analyses of coupled active and past drainage systems by means of step-wise 4D reconstructions of sediments mass transfer, integrating geophysics, geology, geomorphology, state of the art high-resolution dating, and numerical and analogue modelling. The area selected for this programme is the Danube River Basin–Black Sea source to sink system, a world-class natural laboratory that is uniquely suited in the heart of Europe's topography, covering almost half of its surface, providing opportunities for excellent field sites to study in integration surface and subsurface data that cover the complete chain of source, carrier and sink. Quantifying and modelling the complete system in relation to the controlling parameters has resulted in significant understanding of forcing factors and linking temporal and spatial scales across multiple orogen and basin systems. This research has provided the opportunity to widen the geographical scope to other natural scenarios, where a number of mountain chains with similar geodynamic genesis separate sedimentary basins with comparable evolution.
► Defining the source–sink concept and an overview of current research in this field of study ► Linking spatial and temporal scales in the study of coupled orogen and basin dynamics ► The application of the Source to Sink concept to the Danube River–Black Sea Basin system ► Defining the links between basins and their integrated evolution across multiple systems.
Floodplain restoration measures are among the most well-known nature-based solutions for flood risk reduction but practitioners see their limitations in comparison to technical measures when ...considering both their effectiveness and profitability. The aim of this study is to show the co-benefits (besides flood risk reduction) of floodplain restoration and handle them in terms of monetized ecosystem services (ES). Our work focused on six ES groups for three study areas in the Danube catchment along the Krka, Morava, and Danube rivers. ES mapping through stakeholder engagement is also considered. We applied the methodologies suggested in the Toolkit for Ecosystem Service Site-Based Assessment (TESSA) complemented with alternative methodologies (e.g., questionnaires on social media). Results show annual combined benefits of floodplain restoration in a range from 237,000 USD2019 at Krka to 3.1 million USD2019 at Morava, suggesting the utility of ES assessment. The combination of stakeholder workshops and the TESSA guidelines, as well as the newly developed methods, were all central tools to provide decision-makers with arguments to use nature-based solutions for an integrated and holistic riparian land use management.
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.
The aim of this study was to assess the status of aquatic invasive alien species (IAS) in the shoreline zone of the Bulgarian sector of the Danube River, Danube tributaries, and adjacent standing ...water bodies in the frame of the Joint Danube Survey 4 (JDS4). Seven benthic macroinvertebrates and seven fish IAS were identified. The crayfish Faxonius limosus was frequently found and abundant in the tributaries. The mussels Corbicula fluminea, Dreissena rostriformis bugensis, and Sinanodonta woodiana dominated in the Danube River and the middle and lower reaches of the tributaries, while the fish Carassius gibelio, Perccottus glenii, and Lepomis gibbosus were most abundant in the standing water bodies. The integrated biocontamination estimated by taxonomic groups (crayfish, molluscs, and fish), sampling methods, and type of water bodies ranged from moderate in the shoreline zone of the Danube River, through moderate to high in the canals and lakes, to severe in the Danube tributaries and the reservoirs. The results demonstrate the importance of IAS in the assessment of the ecological status/potential of the water bodies in the DRB. The comprehensive evaluation of the aquatic IAS pressure will provide valuable information and support for the implementation of the national and EU IAS and water policies in the DRB.
Major river and flash flood events have accumulated in Central and Eastern Europe over the last decade reminding the public as well as the insurance sector that climate related risks are likely to ...become even more damaging and prevalent as climate patterns change. However, information about current and future hydro-climatic extremes is often not available. The Future Danube Model (FDM) is an end-user driven multi-hazard and risk model suite for the Danube region that has been developed to provide climate services related to perils such as heavy precipitation, heat waves, floods, and droughts under recent and scenario conditions. As a result, it provides spatially consistent information on extreme events and natural resources throughout the entire Danube catchment. It can be used to quantify climate risks, to support the implementation of the EU framework directives, for climate informed urban and land use planning, water resources management, and for climate proofing of large scale infrastructural planning including cost benefit analysis. The model suite consists of five individual and exchangeable modules: a weather and climate module, a hydrological module, a risk module, an adaptation module, and a web-based visualization module. They are linked in such a way that output from one module can either be used standalone or fed into subsequent modules. The utility of the tool has been tested by experts and stakeholders. The results show that more and more intense hydrological extremes are likely to occur under climate scenario conditions, e.g. higher order floods may occur more frequently. Keywords: Danube River basin, Flood risk, Climate services, Climate change
The nutrient loads transported by the Danube River to the Black Sea peaked around the late 1980s, causing massive hypoxia that was accompanied with a severe algae growth. Since then, emissions and ...loads have declined in response to the measures implemented in the Danube River Basin, together with the declining intensity of agriculture. The International Commission for the Protection of the Danube River (ICPDR) initiated Basin-wide activities to support national water policy-making to ensure both the sustainable development of wastewater infrastructure and agricultural production, and the effective protection of freshwater and marine ecosystems.
The Bednja River is the longest river flowing with its full course exclusively through Croatia and one of the largest right tributaries of the Drava River, which belongs to the Danube River basin. ...Due to the variety of habitats present within the course of the Bednja River, as well as older literature reports, it can be expected that this river harbors a high number of freshwater fish species and would likely benefit from conservation and preservation efforts. We compiled and analyzed the existing literature data on the Bednja River fish communities and performed field investigations at various localities on this river in order to describe the current structure of its freshwater fish fauna and monitor changes induced by human activities. Our results corroborate the presence of a rich and diverse fish community. Moreover, with 36 native species, the Bednja River harbors one of the richest fish communities in Croatia as well as in the Danube basin. Unfortunately, modifications of the native fish community were evident in the form of local extinctions, reductions in the population abundance of several native species and the presence of non-native species. Habitat degradation and fragmentation were identified as the most serious threats provoking negative effects on the native fish populations, followed by predatory and competitive effects of invasive species.
The present pilot study tested and validated the use of the ‘Invasive Alien Species in Europe’ smartphone app (IASapp) in the Lower Danube Region. The study was conducted in three stages: (1) Testing ...the effectiveness of the app in Bulgaria, Romania and Serbia by organizing information and field testing campaigns; (2) Improving and extending the functionality of the app and developing a list of the invasive alien species (IAS) of concern to the Danube River Basin (DRB); and (3) Testing the updated app during the Joint Danube Survey 4 campaign. Overall, 13 campaigns were carried out, during which seven aquatic IAS of EU concern and nine IAS relevant to the DRB were recorded. Currently, the developed new functionality of IASapp allows the recording of 64 IAS of DRB concern. The updated IASapp has an important role in increasing public awareness on IAS issues, as well as in enlarging the participation and output of citizen science in the IAS early detection, monitoring and reporting in the DRB. Therefore, the constant communication with existing stakeholder groups and establishment of new citizen science groups is crucial for increasing the effectiveness of using the IASapp in the Danube Region and tackling the IAS issues.
Wastewater treatment plants (WWTPs) represent an important input of contaminants in the environment. Therefore, it is critical to continuously monitor the performance of WWTPs to take appropriate ...action and avoid an influx of contaminants in the environment. In this study, a battery of seven in vitro bioassays covering a selected spectrum of toxicity effects is proposed for quality control of wastewater effluents. The bioassays address mixture toxicity, which is the combined adverse effect of multiple contaminants and can act as an early warning system. The proposed battery was applied to samples from 11 WWTPs of representative technology from the Danube River Basin (DRB). The order of toxic effects in terms of extent of exceedance of effect-based trigger values (EBTs) was PAH (PAH activity) > PXR (xenobiotic metabolism) > ERα (estrogenic activity) > PPARγ > Nrf2 (oxidative stress) > anti-AR > GR. A mitigation plan for WWTP operators based on EBT exceedance is proposed. This study demonstrates that the proposed effect-based monitoring battery is a complementary tool to the chemical analysis approach. A regular application of such time- and cost-effective bioanalytical tools in the WWTPs of the DRB is proposed to provide a ‘safety net’ for aquatic ecosystems.
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