共查询到20条相似文献，搜索用时 31 毫秒
1.
2.
The aim of the study was to evaluate pattern of the aquatic macrophyte species distribution along the Danube fluvial corridor in Slovakia, and to identify the impact of environmental abiotic parameters on macrophyte species diversity. Field sampling was performed in the period 1999–2005 from the boat. Aquatic habitats were divided into 365 survey unit (SU). The survey of aquatic macrophytes and abiotic parameters followed the European standard approach EN 144184 2003. The plant mass estimate (PME – a semi-quantitative estimation of the amount of individual species in a SU, which takes into account three-dimensional development of plant stands) was estimated according to a five-point-scale in each SU; environmental pattern, were assessed over six abiotic parameters (river km, bank type, sediment type, flow velocity class, land-use type, and heavily man-modified water bodies). Altogether, four hydrologic connectivity types of aquatic habitats were distinguished: the Danube River, Open Arms, Separated Arms, and Seepage Water-bodies.
In total, 54 aquatic macrophytes were recorded for the whole data set of the Danube fluvial corridor. The PME data of true aquatic macrophytes and the length of SUs created a basis for numerical derivates, relative plant mass (RPM), mean mass indices (MMT, MMO) and the distribution ratio (d).
The results correspond with comparable studies on this topic: the highest macrophytes species diversity occurred in Separated Arms. On the contrary, macrophytes had the lowest richness in the Danube River main channel, although their diversity was slightly higher in heavily man-modified water bodies (such as the hydropower plant's reservoir and the abandoned main channel of the so-called Old Danube). Our results suggest that the lateral connectivity types of the river water bodies, primarily characterised by different hydrologic dynamics and human impact expressed as land-use types are responsible for the variability of aquatic macrophyte assemblages along the Danube corridor in Slovakia. 相似文献
3.
The present study focuses on the analysis of dryness/wetness conditions in the Danube River catchment area from 1901 to 2013 based on reanalysis data. The spatio‐temporal variability of dryness/wetness conditions is analyzed by means of the Standardized Precipitation Index (SPI) for an accumulation periods of 6 months. To characterize the spatial variability of SPI6 at monthly time scales, an empirical orthogonal function (EOF) analysis was applied. The leading mode of SPI variability captures in‐phase variability of SPI over the entire catchment area of Danube River. The leading mode of dryness/wetness variability was found to be strongly related to the different phases of the Arctic Oscillation. The second and third modes of variability show a more regional character of the dryness/wetness variability over the Danube River catchment area. Based on a composite map analysis, between the time series corresponding to the first three leading modes of dryness/wetness variability and the geopotential height at 850 mb and precipitation totals, it is shown that dryness (wetness) conditions over the Danube catchment area are associated with an anticyclonic (cyclonic) circulation, transport of dry (humid) air towards the Danube catchment area and reduced (enhanced) number of rain days. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
4.
The long‐term trends of yearly discharge time series and runoff variability at seven stations along the River Danube are identified. The results of statistical analysis of discharge time series indicate the period around the year 1860 was the driest decade in central and eastern Europe since 1840. In these years, the mean annual air temperature in central Europe was lower by about 1 °C compared with the 1990s. It is important to notice that the two driest decades (around 1860s and 1990s) of the instrumental era occurred in very different temperature conditions. The 28–31 years; 20–21 years; 14 years, as well as 4·2, 3·6, and 2·4 years fluctuations of annual discharge in the River Danube were found. Also, the long‐term streamflow prediction based on stochastic modelling methods is treated. Harmonic models and the Box–Jenkins methods were used. The predictions of yearly River Danube discharge time series were made for two decades ahead. From the stochastic models it follows that the annual discharge in the Danube at Turnu Severin station should reach its local maximum within the years 2004–06. The period 2015–19 should be dry. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
5.
Models for predicting river water quality could assist protection and utilization of water resources under alternative management strategies. The model of the water quality characteristics of the Danube is based on an ecosystem approach. Considered are all waste water discharges and inflow of tributaries among the catchment area. The identification of model parameters is realized according to the method of integral transformation. For the performance of the model a computer program was elaborated. It is applied in predicting the water quality of the Danube considering almost 20 indicators for the abiotic and biotic parameters of river ecosystem. 相似文献
6.
160 taxa of macrozoobenthos were recorded in the Danube River (R. km 1880-1704) riparian zone. Many typical Danubian and Pontocaspian representatives were found. The Slovak section of the Danube represents the border between its epipotamal and metapotamal stretches with different flow velocity and other environmental variables related to it. This paper characterises some abiotic ecological factors influencing the distribution of benthic taxa in five sampling sites along the longitudinal profile of the Danube. The benthic community composition was more strongly influenced by hydrological parameters than by oxygen and temperature regimes, as well as by the water quality conditions. In other words, the bottom substrate, flow velocity, water level fluctuation and discharge changes had the predominant effect on the taxocoenoses of macrozoobenthos. Three characteristic groups of macrozoobenthic organisms were recorded, as far as corresponding trophic guilds are concerned. Shredders and scrapers predominated in high flow velocity conditions with coarse substrate particles. Collectors of fine organic matter preferred slow-flowing conditions caused by damming or by a reduction of current due to the presence of bedrock. Filterers prevailed in the lower section of the Danube stretch monitored. Predators occurred independently of the environmental variables studied. 相似文献
7.
The regularities of surge-induced water level variations in the Danube mouth are considered. The recurrence of level rises and drops in the near-shore mouth zone is evaluated. The regularities of the propagation of surge-induced level variations into the delta and over the near-delta reach of the Danube are established. The magnitude of positive and negative surges in the delta and the extent of their propagation are shown to depend on the surge phenomena in the offshore zone and the Danube water discharge.Translated from Vodnye Resursy, Vol. 32, No. 1, 2005, pp. 35–47.Original Russian Text Copyright © 2005 by Isupova, Mikhailov, Morozov. 相似文献
8.
F. Lszl 《洁净——土壤、空气、水》1989,17(4):453-463
Summary: In Hungary a large proportion of the drinking-water demand is met by bank filtration. Especially the middle section of the Danube stretch is used for drinking-water supply, also for the capital Budapest (310 · 106 m3/a). The considerable pollutant load imported, anyhow, is increased by several Hungarian sources of contamination. The Danube has such a high self purifying capacity that, among other things, the annual COD-Mn load by the city of Budapest amounting to 140,000 t is degraded to such a level that the export of organic pollutants in the Danube from Hungary is not greater than the import. Heavy metals get into the bank filtrate through organic complexing agents. Also organochlorine compounds and their precursors were quantitatively determined. In Budapest water is treated with ozone, activated carbon and open high-rate filtration. 相似文献
9.
The article discusses the considerable changes in hydrometeorological conditions that occurred in the Danube River basin over
the period from the late XX century to the early XXI century. Mention is made of the air and water temperature rise, softening
of ice conditions, and, above all, the noticeable increase in the river water runoff. Particular attention is given to the
recent extreme hydrological events in the Danube River basin: the disastrous rainfall flood that occurred in August 2002,
the extremely high spring-summer floods in 2006 and 2010, and the extraordinary low-flow period in summer 2003. The meteorological
reasons for these events have been analyzed. Specific features in the development and transformation of flood waves along
the Danube River are discussed in detail, including the impact of the Iron Gate-1 Reservoir on these processes. 相似文献
10.
The effect of sediment yield of a stream and the energy of sea waves on the formation of bars and their dynamics at nontidal river mouths is demonstrated. Data on variations in the hydrological regime of the Potapovskii and Bystryi branches in the Danube Delta and the morphodynamics of their bars are given. Major problems of mathematical modeling of the formation and progradation of mouth bars into the sea are discussed. An analytical expression is obtained for the shape of the foreset slope of a bar, which moves over a constant-slope seabed. The results of simulation were checked against data on the Potapovskii and Bystryi branches in the Danube Delta. 相似文献
11.
Identification of extreme events using drought indices and their impact on the Danube lower basin discharge 
下载免费PDF全文
下载免费PDF全文 In this study extreme droughts and extremely wet periods in the Danube upper and middle basin (DUMB) have been highlighted with specific indices. The most widely used indices have been considered to estimate both the dry and wet phenomena severity and the frequency or spatio‐temporal extension. The climatic condition of 15 meteorological stations situated in the Danube basin has been evaluated using four indices: Palmer Drought Severity Index (PDSI), Palmer Hydrological Drought Index (PHDI), Weighted PDSI (WPLM) and Palmer Z‐index (ZIND). The four indices have been analysed separately for each of the four seasons between 1901 and 2000. First the internal structure of the time series of the four indices has been analysed separately. Then the overall temporal characteristic has been analysed by means of the principal component of the Multivariate Empirical Orthogonal Functions decomposition of the four indices (PC1‐MEOF). For the discharge in the Danube lower basin, station Orsova has been chosen, representing an integrator of the discharges from the DUMB. A very close connection has been found between Palmer indices and Danube discharge in all seasons (with correlation coefficients greater then 0.80) excepting the spring season. A classification in five classes of both the four indices separately and the PC1‐MEOF has been achieved in order to highlight extreme events. The impact of phenomena quantified by Palmer indices in DUMB upon discharges in Danube lower basin is evident. It was demonstrated in this study that the Greenland‐Balkan Oscillation (GBO) influences the south‐east European hydro‐climatic regime more than the North Atlantic Oscillation (NAO) Index. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
12.
《水文科学杂志》2013,58(4)
Abstract Abstract The construction of the Gabcikovo hydropower plant and the diversion of the Danube River over 25 km into an artificial channel in 1992 influenced the groundwater regime of the region considerably. Statistical and geostatistical methods are used to quantify changes of different groundwater characteristics on the Hungarian side of the river based on observations in the time period 1960–2000. External drift kriging was used to interpolate groundwater levels and the other related variables. While mean groundwater levels did not change appreciably, there are significant changes in the variability. Standard deviations of the groundwater levels and the amplitude of the annual cycle decreased near the old river bed of the Danube. The water-level fluctuations of the Danube have a decreased influence on the groundwater dynamics. Interrelationships between water levels in wells have also changed. 相似文献
13.
《Limnologica》2017
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. 相似文献
14.
ABSTRACTThe aims of this study are to investigate the influence of large-scale atmospheric circulation quantified by indices such as the North Atlantic Oscillation index (NAOI), the Greenland-Balkan Oscillation index (GBOI) and blocking-type indices on the Lower Danube discharge. We separately analysed each season for the 1948–2000 period. In addition to the statistical linear procedure, we applied methods to quantify nonlinear connections between variables, as mutual information between predictors and predictand, using Shannon’s information entropy theory. The nonlinear correlation information between climate indices and discharge is higher than that obtained from the linear measure, providing more insight into real connections. Also, the non-stationarity of the link between variables is highlighted by spectral coherence based on wavelet analysis. For the physical interpretation, we analyse composite maps over the Atlantic-European region. The most significant influence on the discharge of the Lower Danube Basin is given by the GBOI and blocking-type atmospheric circulation over Europe. 相似文献
15.
16.
K. Cehak 《Journal of Hydrology》1973,20(1):65-82
The flood data of five stations in the East Alps with relatively long observation series are represented by means of Fisher-Tippett II or III distributions. The observations of the longest observation periods are fitted well by the type II curves. A comparison of calculations with only a part of the observations shows that the magnitude of the curvature parameter k of the Fisher-Tippett curves increases with increasing observation period. The series at hand are not long enough to see if there is a convergence to a limiting value of k.A trend test showed an increasing trend in all of the Danube stations after about 1860 and nearly no trend at all in the observations from the southern rivers.The variance spectra yielded the result that the series may be considered as realizations of autoregressive processes of the first order. Superposed to the red-noise spectra there are waves with periods of 2.35 and 8 years in the case of the Danube stations and with 5.7 and 6.7 years in the case of the southern rivers. 相似文献
17.
Water level variations in the Kiliya Branch of the Danube Delta over the period of 40 years (1958–1997) were analyzed. These level variations were subdivided into three components related to long-term variations of the share of the branch runoff and its redistribution within a year resulting from the Danube flow regulation; subsidence of deltaic deposits; and backup caused by the rising Black Sea level. It was revealed that, during the low-flow period, this backup had propagated to the river mouth at a distance of 160 km. 相似文献
18.
Flow–duration curves (FDCs) are essential to support decisions on water resources management, and their regionalization is fundamental for the assessment of ungauged basins. In comparison with calibrated rainfall–runoff models, statistical methods provide data-driven estimates representing a useful benchmark. The objective of this work is the interpolation of FDCs from ~500 discharge gauging stations in the Danube. To this aim we use total negative deviation top-kriging (TNDTK), as multi-regression models are shown to be unsuitable for representing FDCs across all durations and sites. TNDTK shows a high accuracy for the entire Danube region, with overall Nash-Sutcliffe efficiency values computed in a leave-p-out cross-validation scheme (p equal to one site, one-third and half of the sites), all above 0.88. A reliability measure based on kriging variance is attached to each interpolated FDC at ~4000 prediction nodes. The GIS layer of regionalized FDCs is made available for broader use in the region. 相似文献
19.
ABSTRACTFlow–duration curves (FDCs) are essential to support decisions on water resources management, and their regionalization is fundamental for the assessment of ungauged basins. In comparison with calibrated rainfall–runoff models, statistical methods provide data-driven estimates representing a useful benchmark. The objective of this work is the interpolation of FDCs from ~500 discharge gauging stations in the Danube. To this aim we use total negative deviation top-kriging (TNDTK), as multi-regression models are shown to be unsuitable for representing FDCs across all durations and sites. TNDTK shows a high accuracy for the entire Danube region, with overall Nash-Sutcliffe efficiency values computed in a leave-p-out cross-validation scheme (p equal to one site, one-third and half of the sites), all above 0.88. A reliability measure based on kriging variance is attached to each interpolated FDC at ~4000 prediction nodes. The GIS layer of regionalized FDCs is made available for broader use in the region. 相似文献
20.
M. V. Mikhailova 《Water Resources》2006,33(5):523-534
Sediment balance at river mouths—a physical basis of delta dynamics—is considered. The specific features of relationships between sediment balance components at a mouth of a river are established for a stable, rising, or dropping sea level. The development of the delta of the Chilia branch at the Danube mouth is considered as an example of delta dynamics under the conditions of a relatively stable sea level. The evolution of the Sulak delta in the Caspian Sea with a highly variable level is considered as an example of delta dynamics in the case of a considerable rise and drop of water level in the water body. The anthropogenic reduction of sediment runoff of the rivers (by a factor of two in the Danube, and by a factor of nine in the Sulak) is taken into account. The relationship between the sediment runoff of a river and the volume of the “backwater prism” that formed due to sea level rise is shown to be the key factor in the development of delta in the case of sea level rise. In the case of a drop in the sea level, the relationship between the “active” and “passive” progradation of the delta into the sea is determined by the sediment runoff of the river, the rate of sea level drop, and the bed slope in the coastal area of the nearshore zone. 相似文献