This paper presents a state-of-the-art integrated model assessment to estimate the impacts of the 2°C global mean temperature increase and the 2061-2090 warming period on water scarcity in the Danube ...River Basin under the RCP8.5 scenario. The Water Exploitation Index Plus (WEI+) is used to calculate changes in both spatial extent and people exposed to water scarcity due to land use, water demand, population and climate change. Despite model and data uncertainties, the combined effects of projected land use, water demand and climate change show a decrease in the number of people exposed to water scarcity during the 2°C warming period and an increase in the 2061-2090 period in the Danube River Basin. However, the projected population change results in a decrease of exposed people in both warming periods. Regions with population growth, in the northwestern part of the Danube River Basin experience low water scarcity or a decrease in water scarcity. The largest number of people vulnerable to water scarcity within the Danube River Basin are living in the Great Morava, Bulgarian Danube and Romanian Danube. There, the combined effects of land use, water demand and climate change exacerbate already existing water scarce areas during the 2°C warming period and towards the end of the century new water scarce areas are created. Although less critical during the 2°C warming period, adjacent regions such as the Tisza, Middle Danube and Siret-Prut are susceptible to experience similar exposure to water scarcity within the 2061-2090 period. Climate change is the most important driver for the increase in water scarcity in these regions, but the strengthening effect of water demand (energy sector) and dampening effect of land use change (urbanization) does play a role as well. Therefore, while preparing for times of increased pressures on the water supply it would be advisable for several economic sectors to explore and implement water efficiency measures.
River sediments are a major source of metal contamination in aquatic food webs. Due to the ability of metals to move up the food chain, fishes, occupying higher trophic levels, are considered to be ...good environmental indicators of metal pollution. The aim of this study was to analyze the metal content in tissues of the common barbel (Barbus barbus), a rheophilous cyprinid fish widely distributed in the Danube Basin, in order to find out if it can be used as a bioindicator of the metal content in the river sediment. We analyzed bioavailable concentrations of 15 elements (Al, As, B, Ba, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Se, Sr, and Zn) in sediments of the Danube (D), the Zapadna Morava (ZM), and the Južna Morava (JM) using the inductively coupled plasma spectroscopy (ICP-OES). The barbel specimens were collected in the proximity of sediment sampling sites for the analysis of metals in four tissues, gills, muscle, intestine, and liver. The sediment analysis indicated that the ZM is the most polluted with Cu, Ni, and Zn compared to other two rivers. The JM had the lowest concentrations of almost all observed elements, while the Danube sediments were mainly characterized by higher concentrations of Pb. The fish from the ZM had the highest concentration of Cu and Ni in the liver and intestine, and of Zn in the muscle tissue, which was in accordance with the concentrations of these metals in the sediment. Scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDS) was used for further analyses of metal interactions with fish tissues. The results suggest that the barbel can potentially be used as a bioindicator of sediment quality with respect to metal contamination.
The objective of this study is to analyse the spatial variability of seasonal flood occurrences in the Upper Danube region for the period 1961-2010. The analysis focuses on the understanding of the ...factors that control the spatial variability of winter and summer floods in 88 basins with different physiographic conditions. The evaluation is based on circular statistics, which compare the changes in the mean date and in the seasonal flood concentration index within a year or predefined season. The results indicate that summer half-year and winter half-year floods are dominant in the Alps and northern Danube tributaries, respectively. A comparison of the relative magnitude of flood events indicates that summer half-year floods are on average more than 50% larger than floods in winter. The evaluation of flood occurrence showed that the values of seasonal flood concentration index (median 0.75) in comparison to the annual floods (median 0.58) shows higher temporal concentration of floods. The flood seasonality of winter events is dominant in the Alps; however, along the northern fringe (i.e. the Isar, Iller and Inn River) the timing of winter half-year floods is diverse. The seasonal concentration of summer floods tends to increase with increasing mean elevation of the basins. The occurrence of the three largest summer floods is more stable, i.e. they tend to occur around the same time for the majority of analysed basins. The results show that fixing the summer and winter seasons to specific months does not always allow a clear distinction of the main flood generation processes. Therefore, criteria to define flood typologies that are more robust are needed for regions such as the Upper Danube, with large climate and topographical variability between the lowland and high elevations, particularly for the assessment of the effect of increasing air temperature on snowmelt runoff and associated floods.
Scales and boundaries are integral components of environmental governance policies. These scales and boundaries – administrative, political or institutional – usually do not align with biophysical ...scales. For effective environmental governance, a key policy question is which scale to use when. This question, however, is often ignored due to the unavailability of the tools and data necessary for incorporating scale issues into policy design and implementation. In this paper, we introduce the concept of scale–descale–rescale (SDR) as a tool for policy analysis. 'scale' refers to the current scale of a policy; 'descale' refers to levels of scale that are higher and lower than the current scale; 'rescale' refers to the process of bringing all three scales together in order to examine their interactive impact. In this paper, we present an examination of the framing and implementation of the EU Water Framework Directive (WFD) in the Danube River Basin; we find that the current scale of the WFD design is at the river basin level while, at the same time, its implementation is expected to be carried out at the national and sub-river basin levels. To fully understand the efficacy of the WFD as a policy instrument, we first use the SDR tool to descale the design and implementation of the WFD at five scales: multinational, national, subnational, river basin and sub-river basin; we then rescale them in order to observe the overall impact. We find that in the Danube River Basin an interconnected web of scale issues is impacting and often obstructing effective implementation of the WFD.
The interannual and interdecadal distributions of the indices of large-scale atmospheric oscillations and the anomalies of precipitation and surface air temperature in the Danube River basin in ...winter during 1950–2010 are considered. The number of winters with positive and negative precipitation and air temperature anomalies observed during various combinations of the positive and negative phases of the North Atlantic and East Atlantic oscillations is determined. The influence of the North Atlantic and East Atlantic oscillations in various combinations of their phases on the variability of precipitation and air temperature anomalies in the winter months is estimated. The estimation is based on the calculated pair and multiple coefficients of correlation between the indices of atmospheric oscillations and precipitation and air temperature anomalies.
Brown trout of non-native lineages have been stocked into Croatian streams and rivers primarily to meet angler demand. The diet of brown trout in the Black Sea Basin of Croatia is poorly understood, ...and there are no studies examining feeding competition between the Atlantic (AT) and Danube (DA) lineages of brown trout and their hybrids (HY). The aim of this study was to examine the natural diet of brown trout of both lineages and their hybrids and to compare feeding overlap. Canonical correspondence analysis was used to investigate the relationships between feeding habits of fish from different streams and of different genetic origin. The differences in variation of the consumed prey items were analysed by canonical variate analysis, and diet overlap was assessed by the Schoener index. The results indicate that stocked brown trout (AT) adapt rapidly to new habitat and food, as revealed by the consumption of a wide range of available food items and competition for food and space by taking on the feeding behaviour of wild native conspecifics. Diet overlap was also detected between brown trout of the DA and AT lineages. This study highlights the need to implement control measures to preserve and protect the native diversity of this species.
A study of the environmental radioactivity in the Kopački Rit Nature Park, Croatia, is presented. This wildlife reserve is part of the Middle Danube River Basin, and it is exposed to various ...pollutants due to a number of human activities in the surroundings, where there is a nuclear power plant and also urban centres and areas of intense agricultural production. Results for the activity concentrations of soil and surface water samples do not indicate any elevated radioactivity level, which is confirmed by on-site measurements of ambient dose rate equivalent. An assessment of the radiological load on the local biota, carried out using the ERICA tool, implies an overall low radiological risk even if conservative values of the risk quotient are used. Therefore, human activities do not have a significant effect on the radiological load on the Kopački Rit area. A similar conclusion might be made with regard to numerous similar environments in the Middle Danube River Basin.
In this paper, we provide a Lagrangian analysis of the anomalies in the moisture transport during two important drought events (1989/1990 and 2003) configured over the Danube River Basin (DRB) ...region. Firstly, we identified the drought episodes that occurred over the DRB in the period of 1980–2014 through the Standardized Precipitation Evapotranspiration Index (SPEI). SPEI was calculated using monthly Climatic Research Unit (CRU) Time-Series (TS) Version 3.23 precipitation and potential evapotranspiration (PET) datasets with a spatial resolution of 0.5 degrees. The monthly SPEI-1 index was applied to identify the drought episodes and their respective indicators, including duration, severity, and intensity. Two significant drought events were selected: 1989/1990 (presenting dry conditions during October 1989–March 1990) and 2003 (presenting dry conditions during April 2003–September 2003). These events were associated with the two most severe SPEI-1 episodes identified over the DRB during 1980–2014. Then, an analysis of anomalies in the moisture transport was conducted in order to verify possible changes in the moisture supply from the climatological sources for the DRB during these episodes. The moisture transport analysis was performed through a Lagrangian approach, which uses the outputs of the FLEXiblePARTicle dispersion model FLEXPART integrated with one of the reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF): the ECMWF Re-Analysis (ERA)-Interim dataset. The DRB receives moisture from seven different moisture source regions: the North Atlantic Ocean (NATL), North Africa (NAF), the Mediterranean Sea (MED), the Black Sea (BS), the Caspian Sea (CS), the DRB, and Central and Eastern Europe (Rest of Land (RestL)). The analysis of drought events shows that the precipitation and moisture supply from the selected sources weakened mainly during both drought events. Anomalous subsidence and an increased PET also prevailed over the DRB during these SPEI-1 episodes. RestL and MED registered the most intensive reduction in the moisture supply over the DRB during both periods.
In this study, we investigate the sources of moisture (and moisture for precipitation) over the Danube River Basin (DRB) by means of a Lagrangian approach using the FLEXPART V9.0 particle dispersion ...model together with ERA-Interim reanalysis data to track changes in atmospheric moisture over 10-day trajectories. This approach computes the budget of evaporation-minus-precipitation by calculating changes in specific humidity along forward and backward trajectories. We considered a time period of 34 years, from 1980 to 2014, which allowed for the identification of climatological sources and moisture transport towards the basin. Results show that the DRB mainly receives moisture from seven different oceanic, maritime, and terrestrial moisture source regions: North Atlantic Ocean, North Africa, the Mediterranean Sea, Black Sea, Caspian Sea, the Danube River Basin, and Central and Eastern Europe. The contribution of these sources varies by season. During winter (October-March) the main moisture source for the DRB is the Mediterranean Sea, while during summer (April-September) the dominant source of moisture is the DRB itself. Moisture from each source has a different contribution to precipitation in the DRB. Among the sources studied, results show that the moisture from the Mediterranean Sea provides the greatest contribution to precipitation in the basin in both seasons, extending to the whole basin for the winter, but being more confined to the western side during the summer. Moisture from the Caspian and Black Seas contributes to precipitation rather less.
As a basis for future conservation activities, the genetic and external body morphology variability of the European mudminnow Umbra krameri, a highly endangered fish species in Serbia and in Bosnia ...and Herzegovina, was determined for existing populations with the use of molecular markers (mitochondrial and microsatellite DNA) and geometric morphometric methods. Mitochondrial DNA cytochrome b gene analysis revealed two previously undescribed haplotypes: Da1 (the Lugomir population from the Danube River basin) and Sa1 (the Bakreni Batar and the Gromiželj populations from the Sava River system), with a corresponding genetic distance of 0·7%. Paired values of FST and DAS distances for microsatellite marker data show that the difference between the Danube and the Sava populations is seven to nine times higher than the difference between the populations within the Sava River system. Geometric morphometric analyses also support a clear separation of the Lugomir population from the Bakreni Batar and the Gromiželj populations. The analysis of the body shape variation, however, indicates a significant difference between the two genetically indistinguishable Sava populations. The observed genetic and phenetic relationships of the analysed mudminnow populations most probably represent a consequence of historical, geographical and ecological factors. These results will offer guidelines for future protection, conservation and sustainable management of this species in the region.
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