Showing papers in "River Systems in 2003"
TL;DR: In this article, an overview of recent progress in Europe and North America structured along the following main questions: "Where are we heading, i.e. what are our references and how can we translate them into realizable end-points?" and "How should we integrate rehabilitation into future river management to efficiently achieve our goals?"
Abstract: The physical degradation of large regulated rivers in Europe and North America and the need for rehabilitation have become issues since the 1980s. Over the past years we have greatly increased our understanding of the ecological functioning of natural rivers, evaluated the ecological impacts of river regulation, and established various approaches for river rehabilitation and restoration. Complete restoration of large rivers may be a utopian idea because of the manifold functions they serve. It is not surprising, therefore, that rehabilitation attempts so far have only recovered stretches or certain features of rivers. The steps to he taken now are to share our expertise on river functioning, river management and rehabilitation, and to put this expertise into practice. This paper gives an overview of recent progress in Europe and North America structured along the following main questions: ○ Where are we heading, i.e. what are our references and how can we translate them into realizable end-points ○ What is our experience with past attempts of rehabilitation, and how can we best assess our past and future achievements? ○ How should we integrate rehabilitation into future river management to efficiently achieve our goals, i.e. where are the joint opportunities and opposing interests with other functions? ○ How do we optimize and prioritize our efforts to maximize ecological outcome, and in which form should those benefits be demonstrated? Following this analysis, we address management needs and make recommendations for a future research agenda on rehabilitation of large regulated rivers. Our goal is to incorporate a general understanding of large river functioning into the practice of river rehabilitation by: (a) defining tangible and attainable endpoints deduced from ecologically intact or pristine references either derived from reconstruction of historic conditions or from spatial analogues; (b) developing prognostic tools to link abiotic processes and patterns and biotic response at the appropriate spatial and temporal scales; and (c) optimizing rehabilitation within the multitude of functions large rivers fulfil and considering the heavily modified condition of most regulated large rivers. To achieve success in rehabilitation projects, all stakeholders should make better use of existing knowledge when they plan, execute and evaluate river rehabilitation. Well-documented pilot studies should be exploited since they give room for more adventurous rehabilitation not only along the same river but also elsewhere.
62 citations
TL;DR: In this paper, a new method was developed to assess the ecological status of river/floodplain systems based on the requirements of biological assessment laid down in the EU Water Framework Directive, and therefore focused on water bodies and their environs while neglecting truly terrestrial floodplain sections.
Abstract: A new method was developed to assess the ecological status of river/floodplain-systems. The approach is based on the requirements of biological assessment laid down in the EU Water Framework Directive, and, therefore, focuses on water bodies and their environs while neglecting truly terrestrial floodplain sections. The following indicator groups have been integrated: molluscs, caddisflies, dragonflies, amphibians, and fish. These groups were chosen to describe species associations representative of all types of floodplain waters along the gradient of hydrological connectivity. Key element of the procedure is the Floodplain Index, which is calculated for each site investigated on the basis of species-specific habitat values expressing the species' habitat preferences. Since species compositions vary according to the hydrological conditions, the water bodies of an investigation area can be characterized according to the index values. The distribution of the index values shows if and to which extent the degree of lateral connectivity is disturbed in the floodplain area. The assessment of the ecological status is based on a comparison between a river-type-specific reference condition and the status quo. The method is presented with an example from a Danube floodplain area in the north of Vienna (Austria).
56 citations
TL;DR: In this paper, the authors combined multi-attribute value theory (MAVT) with stakeholder classification to estimate the conflict potential for different rehabilitation alternatives at the Thur River in Switzerland, and the results indicate that such a combination of methods can help to identify potential conflicts and create alternatives that are likely to have a higher degree of consensus.
Abstract: The decision making process in river rehabilitation is complex. It is characterized by multiple objectives, multiple stakeholders and a high uncertainty in the outcome. Multi-criteria decision making approaches can offer helpful methods when faced with the problem of conflicting objectives and uncertain outcomes. However, there is a lack of tested methods to incorporate stakeholder values explicitly in decision making. The current study combines multi-attribute value theory (MAVT) with stakeholder classification to estimate the conflict potential for different rehabilitation alternatives at the Thur River in Switzerland. We elicited values from representatives of eight major stakeholder groups and classified the stakeholder groups based on their influence potential. The results indicate that such a combination of methods can help to identify potential conflicts and create alternatives that are likely to have a higher degree of consensus. In our case study, a potential consensus solution consisted of seeking to achieve a combination of different objectives, including improvement in ecological status and flood protection as well as preservation of agricultural activity. The proposed solution would not result in maximum gain for ecological status and flood protection, however river rehabilitation would still achieve major improvement compared to status quo, and conflict potential is estimated to be significantly lower in comparison to other alternatives.
49 citations
TL;DR: Two methods using submerged macrophytes to assess and monitor changes in the nutrient status of running waters are described.
Abstract: Submerged macrophytes respond to changes in the nutrient concentrations in their environment. In contrast to diatoms e.g., submerged macrophytes are capable of taking up nutrients from both the sediment pore water and the overlying water. Therefore, macrophytes can provide a more comprehensive assessment of river ecosystems. Two methods using submerged macrophytes to assess and monitor changes in the nutrient status of running waters are described.
46 citations
TL;DR: Benefit-cost analyses were performed for several scenarios of dyke relocation and indicated a positive benefit-cost ratio even for the scenario with the highest costs, and future perspectives of rehabilitation for the Middle Elbe River are discussed.
Abstract: Based on an overview of the present state of the Middle Elbe River and existing management objectives concerning nature protection, navigation, and flood control, we describe conflicting goals. Regarding the course and structure of the river channel and floodplain, we will propose strategies and measures for integrated river management. We will focus on several scenarios of dyke relocation, which have been studied from a hydrological, ecological, and socioeconomic point of view. The retention effect of dyke relocation depends nor only on the spatial situation (e.g., river section, area size), but also on the type of measure (controlled retention in storage holders or dyke relocation). Socioeconomic studies have shown a willingness by society to pay for dyke relocation amounting to about 108 million?.a -1 . The economic value of floodplain rehabilitation due to nutrient removal is assessed at 7 million?. annually. Benefit-cost analyses were performed for several scenarios of dyke relocation and indicated a positive benefit-cost ratio even for the scenario with the highest costs. Finally, we report on experiences concerning administrative aspects of implementation of measures and discuss future perspectives of rehabilitation for the Middle Elbe River.
43 citations
TL;DR: In this article, the role of in-channel retention for phytoplankton development and a reopened side-arm and the floodplain for the phosphorus dynamics is discussed in the Austrian Danube downstream of Vienna.
Abstract: Nutrient storage and transformation as well as aquatic production are key ecosystem functions and are related to areas of higher retention in the river corridor. The significance of retention as a main element for understanding ecosystem processes becomes apparent in regulated rivers where both retention and hydrologic connections between the main channel and its slackwater areas and the adjacent riverine landscape have markedly decreased. We give some evidence that in-channel structures and side-arms are important slackwater areas below bankfull level in a braided, anabranched river section, the Danube downstream of Vienna. In that stretch the role of in-channel retention for phytoplankton development and a reopened side-arm and the floodplain for the phosphorus dynamics is discussed. The transformation of phosphate is related to phytoplankton development and increased connectivity below bankfull enhances the transformation capacity of the reopened side-arm. The rate of deposition during floods is still the decisive process in terms of annual total phosphorus budgets and is presented for the years 1997-2002. Up to 1 % of the total annual load transported is retained in the floodplain area. Rehabilitation efforts, like those along the Austrian Danube, which increase the hydrological exchange with slackwater areas, will enhance nutrient processing and the production of autochthonous POM and thereby, also re-establish these ecosystem functions on a larger scale than the local measures.
32 citations
TL;DR: Two-dimensional and three-dimensional numerical models are applied to natural and rehabilitated river systems, i.e. the Rhine (the Netherlands), Allier (France) and Volga (Russia), showing that vegetation has a pronounced effect on flow patterns and morphological developments in rivers.
Abstract: Numerical simulations of the effects of vegetation on flow and morphology are helpful to understand the behaviour of natural rivers and to predict the developments of rehabilitated rivers. However, some fundamental problems remain in modelling these interactions. This paper describes the application of two-dimensional and three-dimensional numerical models to natural and rehabilitated river systems, i.e. the Rhine (the Netherlands), Allier (France) and Volga (Russia). The results show that vegetation has a pronounced effect on flow patterns and morphological developments in rivers. This can be subdivided in remote effects and local effects. Further analysis of the model results shows a fundamental shortcoming in the mathematical modelling of the effects of vegetation on the local sediment transport capacity. Traditional approaches to modelling vegetation roughness yield erroneous results in combination with common sediment transport equations. Therefore, research focuses on the development of new model approaches to accurately simulate the influence of vegetation on flow and morphology.
28 citations
TL;DR: In Switzerland the river rehabilitation potential is very high and extensive flood protection programmes with elements of river rehabilitation are being carried out, supported by a comprehensive transdisciplinary research project focusing on four main rehabilitation related topics.
Abstract: In Switzerland the river rehabilitation potential is very high. Approximately 25,600 km of streams and rivers require rehabilitation (43 % of the total stream/river length). In order to improve habitats, connectivity, biodiversity and ecological services, large financial resources are needed in the near future. For social acceptance at an early phase clear ecological and societal goals must be set and the involvement of stakeholders ensured. Along the Rivers Rhone and Thur extensive flood protection programmes with elements of river rehabilitation are being carried out. These are supported by a comprehensive transdisciplinary research project focusing on four main rehabilitation related topics: decision-making processes associated with rehabilitation programmes, local river widenings as principal rehabilitation measures, rehabilitation in river sections impacted by hydropeaking, and success evaluation after the completion of rehabilitation.
23 citations
TL;DR: A weight of evidence approach reveals that invertebrates, small mammals and birds of prey are at risk due to metal exposure and Comparisons of measured and predicted cadmium concentrations in various species show that available models may overestimate as well as underestimate exposure risks.
Abstract: Ambitious international action programmes and ecological rehabilitation projects have improved the environmental quality of riverine habitats along the Rhine branches in the Netherlands (rivers Waal, Neder-Rijn and IJssel). A major problem that remains to be solved is the contamination that over the last century has been accumulated in river sediments and deposits. Respectively, 65, 45 and 35 % of soil samples from floodplains along the rivers Waal, Neder-Rijn and IJssel exceed environmental quality standards for one or more contaminants (mainly metals). Storing or cleaning of contaminated sediments goes with high remediation costs and impedes ecological rehabilitation projects. Physical reconstruction measures may alter exposure of organisms to contaminants, e.g. by changing the bioavailability through transitions of terrestrial to aquatic habitats and vice versa. The question arises whether contaminants accumulated in river sediment and deposits will hinder the recovery of riverine biodiversity. The present paper gives an account of various approaches for ecological risk assessment of contaminated floodplain soils and focuses on effects of metal contamination (mainly cadmium) on riverine biodiversity. A weight of evidence approach reveals that invertebrates, small mammals and birds of prey are at risk due to metal exposure. Comparisons of measured and predicted cadmium concentrations in various species show that available models may overestimate as well as underestimate exposure risks. Site-specific exposure models should take into account spatial and temporal variability of exposure. GIS-based ecological risk assessment and site-specific risk maps offer river managers opportunities to delineate high-risk areas and to balance costs and ecological benefits of soil sanitation measures in river rehabilitation projects. New approaches to the remediation of floodplain soil contamination are briefly discussed.
23 citations
TL;DR: In this paper, the authors focused on the Lower Volga, a large low-gradient sand-bed river with a bank-full discharge of about 10.000 m 3 s -1.
Abstract: In recent years, the concept of 'Cyclic Floodplain Rejuvenation' (CFR) has been adopted as a guiding principle for ecological rehabilitation in combination with flood protection of the lower Rhine and Meuse rivers in The Netherlands. This concept is based on erosion and sedimentation processes in natural fluvial systems that periodically reset the morphological and vegetation succession of the river floodplain. In regulated and harnessed river systems, controlled and artificial rejuvenation of floodplain habitats could be an interesting approach to solve the nature-flood protection dilemma. This, however, requires thorough understanding of the natural dynamics of lowland rivers and the bio-geomorphologic interactions on floodplains. These have been studied in a joint project of Dutch and Russian research institutes along the Allier River (France) and the Lower Volga (Russian Federation), which are considered semi-natural references for the lower Meuse and Rhine rivers. The present study focused on the Lower Volga, a large low-gradient sand-bed river with a bank-full discharge of about 10.000 m 3 s -1 . It is a 300-km long single to multi-channel system characterized by natural morphology of meandering alluvial rivers. The flood plain is about 30 km wide, with mostly natural vegetation and some extensive land use. Morphological changes over the past decennia were reconstructed, and succession schemes of morphology and associated vegetation types were established. This was achieved using aerial photographs, old river maps, satellite images, and morphological mapping and vegetation surveys in the field. The results revealed different rejuvenation cycles for different morphological units, each with a characteristic vegetation succession scheme. From these, guidelines for artificial CFR of the lower Rhine were derived.
21 citations
TL;DR: Considering their high diversity in floodplain areas, both in absolute numbers and in betadiversity, and high number of preferential species in the Dutch Rhine branches, aculeate wasps, Apidae and Carabidae seem to be the most suitable of the studied groups for assessment of the heterogeneity of floodplain ecosystems.
Abstract: In 2001 and 2002 a survey has been carried out on several taxonomic invertebrate groups in five floodplain areas along the river Waal in the Netherlands. Studied groups are: aculeate wasps (Hymenoptera: Chrysididae, Crabronidae, Tiphiidae, Pompilidae, Sphecidae, Vespidae), Apidae s.l. (Hymenoptera), Carabidae (Coleoptera), Mollusca (only terrestrial species), Odonata, Orthoptera, Syrphidae (Diptera). The study focused on sand dunes, high river banks, grasslands and marshes. The aim of the study was to compare the investigated invertebrate groups in terms of betadiversity to determine their sensitivity for heterogeneity of floodplain ecosystems. The results have been analysed in combination with the faunistic database of EIS (European Invertebrate Survey) - the Netherlands. Based on this database, species were selected of which at least 5 % of their distribution is situated in the Dutch Rhine branches ('preferential species'). Considering their high diversity in floodplain areas, both in absolute numbers and in betadiversity, and high number of preferential species in the Dutch Rhine branches, aculeate wasps, Apidae and Carabidae seem to be the most suitable of the studied groups for assessment of the heterogeneity of floodplain ecosystems. In aculeate wasps and Apidae, the highest diversity occurs in high parts of the floodplains. In Carabidae and Syrphidae with aquatic larvae, the highest diversity occurs in low parts of the floodplains.
TL;DR: In this article, a method for characterizing historical fish species composition was proposed to evaluate available historical information, to characterize historical changes of fish communities, and to derive semi-quantitative fish-faunistic references.
Abstract: This study aims to implement a method for characterizing historical fish species composition. Historical data on fish communities and human alterations of rivers have been extracted from a broad range of historical sources as well as archaeological studies. Two large lowland river systems in Germany, Elbe and Oder, serve as an example to summarize and evaluate available historical information, to characterize historical changes of fish communities, and to derive semi-quantitative fish-faunistic references. It is recommended to date the historical baseline for fish-faunistic references back to the year 1850, before the large river regulations of the 19 th century had a negative effect on fish, and before numerous neozoans spread out. The reference fish communities exemplified for the bream region of the rivers Elbe and Oder comprise 42 fish species, each with a rough but calibrated description of relative species abundance integrating 300 years of fish records. According to our fish-faunistic reference, slow-flowing metapotamal river stretches are characterized by a) about 36-37 % of rheophilic fish, b) about 10-12 % of lithophilic and 9-10 % psammophilic spawners, c) a high species diversity (H' = 2.90-2.93), and d) a relatively even dominance structure. A consistent methodological approach to develop fish-faunistic references for various river types is a prerequisite for fish-based assessment of ecological integrity of river systems and, thus, for the implementation of the new EU Water Framework Directive (WFD) (2000/60/EG).
TL;DR: In this article, the authors describe various types of rehabilitation measures deduced from historical references of alluvial Danube river sections, which mainly involve improving the riparian zones, small-scale widenings and mitigating the river continuum both at tributary confluences and in the main channel.
Abstract: The 350 km long Austrian Danube River is characterized by a natural sequence of constrained and alluvial sections. Its hydromorphological character has been changed severely by systematic channelization since the mid-19 th century and hydropower plant construction since the 1950s. An ecological assessment of the Danube River, especially regarding the fish fauna, clearly shows the present deficits compared with the Leitbild (high ecological status) according to the Water Framework Directive of the EU. Intensive human uses constrain implementing comprehensive rehabilitation programs to achieve a good ecological status. Since approx. 80 % of the river length can be provisionally classified as heavily modified water bodies due to chains of impoundments, an adapted Leitbild approach for the development as well as the evaluation of mitigation measures has to be elaborated to achieve a good ecological potential. The range of Leitbild-specific rehabilitation measures is generally restricted within impoundments, in particular in alluvial sections. The most favourable opportunities are present at the heads of reservoirs, where dynamic hydromorphological conditions remain. In constrained sections, rehabilitation measures mainly involve improving the riparian zones, small-scale widenings and mitigating the river continuum both at tributary confluences and in the main channel. In alluvial sections the main focus is on re-establishing lateral and longitudinal connectivity as well as fluvial dynamics. Against this background the present paper describes various types of rehabilitation measures deduced from historical references of alluvial Danube river sections.
TL;DR: These investigations provided abundant data on the types of communities, their floristic composition, distribution, and ecology as well as on production capacities of macrophytic vegetation, indicating the necessity of monitoring its ecosystems.
Abstract: The first investigations of macrophytic flora and vegetation colonizing the flowing Djerdap reservoir were started four years ago. A particular emphasis has been placed on the river Danube stretch between the islet of Zilovo and the mouth of the river Nera (river-km 1090 and 1075), given that the shallow parts of this stretch are already overgrown with macrophytes. These investigations provided abundant data on the types of communities, their floristic composition, distribution, and ecology as well as on production capacities of macrophytic vegetation. The results of these investigations enable an assessment of the current and future condition of the Djerdap reservoir, indicating the necessity of monitoring its ecosystems.
TL;DR: In this paper, the authors present a synopsis of the rivers Rhine and Danube in Europe, connected by the Rhine-Main-Danube waterway, and discuss the ongoing and future restoration programmes.
Abstract: This paper presents a synopsis of the rivers Rhine and Danube in Europe, connected by the Rhine-Main-Danube waterway. Their morphological destruction and subsequent ecological impacts are documented, and the ongoing and future restoration programmes are discussed. While the River Rhine has improved significantly in water quality and still is channelized to a large extent (despite considerable restoration), the River Danube features more near natural stretches and flood plains while still being largely polluted in the middle and lower parts. In both catchments, the goals of research/management are unlimited fish migration (e. g., salmon in the Rhine, and sturgeon in the Danube), some gravel and sediment transport, the conservation/restoration of flood plains as hot spots of biodiversity and flood retention areas, and the sustainable development of the river basin. While the River Rhine authorities (including five countries) are advanced in the political process of river basin management, the River Danube authorities (including 16 countries) still must find a harmonized cooperation.
Abstract: Large rivers are conduits for nutrients and sediments from continents to the sea, but can also support productive fisheries within river-floodplain ecosystems. To assay sources of organic matter important for fisheries in the lower Mississippi River, we measured concentrations and stable isotope values of particulate organic carbon and nitrogen over a 2+ year period at Baton Rouge, Louisiana. Mixing models indicated average concentrations of 73 and 38 μmol C/l as soil carbon and labile carbon, respectively, with labile carbon composed of a mixture of phytoplankton and bacteria. The average carbon isotope value for transported soil was -22.2 ‰, similar to recent marine sediment values. The combination of high concentrations of labile carbon and high throughput indicates a potentially rich production regime for floodplain food webs linked to the Mississippi River.
TL;DR: In this article, a cost-effective monitoring program based on registration of by-catches from commercial (fykenet) fishermen carried out since 1993 in the Rhine and Meuse in the Netherlands reveals that the population levels of many rare (mainly red list) species show increasing trends, demonstrating the improvement of the ecological quality of Rhine this article.
Abstract: The Dutch lowland rivers Rhine and Meuse have lost much of their natural character and many species of riverine fish have become rare or extinct due to water pollution, habitat loss, and exploitation over the last century. Since the 1980s, management measures have been taken to improve water quality and to restore habitats and fish migration opportunities. Rehabilitation includes amongst others enhancing the active floodplain dynamics through (re)connecting isolated floodplain waters to the main river channel. Fish passages along weirs and sluices have been constructed and, at dammed estuaries, discharge regimes will be adjusted to facilitate fish migration. There are several lines of evidence that these measures have contributed to a rehabilitation of riverine fish populations. Studies in newly created side channels demonstrate the enhancement of nursery habitat. A cost-effective monitoring programme based on registration of by-catches from commercial (fykenet) fishermen carried out since 1993 in the Rhine and Meuse in the Netherlands reveals that the population levels of many rare (mainly red list) species show increasing trends, demonstrating the improvement of the ecological quality of Rhine and Meuse. Rehabilitation of the floodplain function and reducing the impact of hydromorphological barriers could further enhance fish populations at the river basin level. The response of different fish species to river rehabilitation has been variable and may have different causes. We conclude that fish community changes are sensible indicators of ecological rehabilitation when the response time (≥ 10 years) is taken into account, which requires long-term monitoring.
TL;DR: This work uses the experience on the Hudson River estuary, New York (USA), to illustrate some important interactions that link alien species and river restoration.
Abstract: The large-river ecosystems that are the subject of restoration efforts also typically are heavily invaded by alien species. We use our experience on the Hudson River estuary, New York (USA), to illustrate some important interactions that link alien species and river restoration. Most obviously, restoration may be aimed at controlling populations of undesirable alien species. Alien species like common reed (Phragmites communis), water-chestnut (Trapa natans), and purple loosestrife (Lythrum salicaria) have been the targets of eradication programs in the Hudson. Such eradication efforts sometimes are poorly motivated, have non-target effects, have had mixed success in controlling the target species, or are entirely infeasible. Second, the presence of alien species may complicate restoration programs designed to address other goals. The presence of alien species may limit the range of available options, make the results of restoration activities more difficult to predict, and make it difficult to define or reach reference conditions. Finally, restoration programs may bring in or favor alien species. For example, materials used in restoration projects may be contaminated with the propagules of alien species. Consequently, restoration projects in large rivers often are intertwined with alien species in one way or another.
TL;DR: Overexploitation and habitat degradation are the major threats for Danubian sturgeons, and the enforcement and implementation of strict fishing regulations, supplementing stocking programmes, and last but not least river restoration are recommended as the most effective management strategies.
Abstract: This paper compiles an extensive literature study (REINARTZ 2002) on the biology, ecology and status of the Danubian sturgeon species, as well as possibilities for their conservation and restoration. Only four out of six acipenserid species, that were native to the Danube River Basin, still reproduce in the Lower Danube River. In the Upper and Middle Danube River, migratory sturgeons have become extinct. Survival of the only true potamodromous sturgeon species in the Danube, the sterlet (Acipenser ruthenus), depends solely on stocking in the Upper Danube. Overexploitation and habitat degradation are the major threats for Danubian sturgeons. Hence, the enforcement and implementation of strict fishing regulations, supplementing stocking programmes, and last but not least river restoration are recommended as the most effective management strategies. In particular, the existing dams along the Danube River and major tributaries must be made passable for the migrating sturgeons. Telemetry and molecular genetics may help to elucidate the natural behaviour and range of sturgeon habitats. Sound scientific research must be the foundation of sustainable sturgeon management.
TL;DR: Comparisons of species composition and abundance of macrophytes of the River Ižica between the years 1996 and 2000 indicate a higher level of eutrophication in 2000.
Abstract: This paper presents a comparison of species composition and abundance of macrophytes of the River Ižica between the years 1996 and 2000. In both surveys 24 species of macrophytes were identified in the river. At the very source some species, characteristic of moderate nutrient concentrations habitats (Berula erecta, Callitriche cophocarpa and Veronica anagallis-aquatica) were found along with some species characteristic of moderately eutrophic habitats (Cladophora sp., Elodea canadensis). Species characteristic of nutrient-rich habitats (Nuteum lutea, Potamogeton pectinatus, and Sagittaria sagittifolia) occurred mainly in the middle and lower parts of the river. Changes in the abundance and distribution indicate a higher level of eutrophication in 2000. Cladophora sp., Nasturtium afficinale, Nuphar lutea, and Sagittaria sagittifolia were more abundant, whilst Batrachium trichophyllum, Berula erecta, Scirpus lacustris, Sparganium emersum, Callitriche cophocarpa and Elodea canadensis were less common.
TL;DR: In this paper, the 19 th century pattern of geomorphology, natural vegetation, and land use was reconstructed using old river maps and historic water level data, and guidelines for floodplain restoration targets and landscaping measures were given at the scale of the river reaches.
Abstract: Ecological restoration of the lower Rhine and Meuse floodplains aims at improvement of biodiversity and enhancement of natural hydro-morphodynamics, this within the constraints of safety and navigability. Restoration plans, the choice of landscaping measures, and the eco-morphological targets should account for the natural differences in morphodynamics and ecological patterns along the rivers. To achieve this, the hydro- and morphodynamics as well as the landscape pattern that existed in historic times - before the main regulation works in 1850 - served as a reference. Bio-geomorphological characteristics were determined of 20 to 30-km river reaches along the lower Rhine and Meuse, including the estuary. Using old river maps and historic water level data the 19 th century pattern of geomorphology, natural vegetation, and land use was reconstructed. Quantitative hydro-morphological parameters (width-depth ratio, specific stream power, Shields parameter, water level fluctuations) were determined for 12 river reaches. From these, the downstream charges along the river reaches were assessed, landscape types were related to hydro-morph/)dynamic processes, and characteristic processes and landscape patterns for different reaches were identified. Using these results, guidelines for floodplain restoration targets and landscaping measures were given at the scale of the river reaches.
TL;DR: According to the electron microscopic investigations biofilms containmany bacteriy on frustules of the diatoms, their surfaces serve as habitats for different bacteria, and the bacteria attached to surfaces are metabolically more active than planktonic forms.
Abstract: Epilithic microbial communities which colonize and grow on gravel, pebbles and rocks are important in the nutrient cycling of aquatic environments and are responsible for processes like self-purification of the water, degradation of organic materials and xenobiotics. Thus, the metabolic activity of biofilms have deep influence on the water quality. The bacteria attached to surfaces are metabolically more active than planktonic forms. Among algae the diatoms are found to be dominant in the epilithic communities of the River Danube. According to our electron microscopic investigations biofilms contain many bacteria on frustules of the diatoms, their surfaces serve as habitats for different bacteria. Artificial matglass substrata were submerged in the water of the River Danube at 50-60 cm water depth at 1669 river km, at the study site of God (Hungary). Parallels were taken on the 6 th day of incubation, and the biofilm washed into diatom growth medium. This sample was used to isolate diatom associated bacterial strains. Representative strains were selected by ARDRA analysis, and were identified by 16S rDNA sequence comparisons. Specific bacteria selected on surfaces of cultivated diatoms were species typically isolated from aquatic environments (Pseudomonas putida, Caulobacter crescentus), facultative methylotrophic or/and H 2 autotrophic bacteria (Xanthobacter autotrophicus, Ancylobacter aquaticus, Hydrogenophaga sp.), N 2 fixers (Xanthobacter autotrophicus, Ancylobacter aquaticus, Azospirillum spp.) and bacteria usually characteristic in soils (Bosea thiooxidans, Rhizobium sp., Afipia genosp., Bacillus insolitus, Microbacterium lacticum).
TL;DR: The Rhine-Meuse estuary is potentially one of the most important wetland areas in the Netherlands, but since the Middle Ages it has been subjected to excessive influence from human activities, and therefore habitat rehabilitation has become effective.
Abstract: The Rhine-Meuse estuary is potentially one of the most important wetland areas in the Netherlands, but since the Middle Ages it has been subjected to excessive influence from human activities. Marshes have been convened into agricultural land, harbours, and cities. Estuarine dynamics were minimized for storm surge protection, and the estuary became heavily polluted. Since the late seventies water quality has improved, and therefore habitat rehabilitation has become effective. To achieve a healthier ecosystem a program of remedial action has been launched. Some elements, such as the protection of valuable wetlands against erosion, have been almost completely realized. In the nineties, the management strategy changed direction towards the restoration and enhancement of ecological functions, rather than being confined exclusively to the protection of existing values. The main issue became the restoration of estuarine processes. This can be achieved through the modification and management of the Haringvliet sluices, and by creating conditions that assist ecological rehabilitation. Greater emphasis is given to the restoration of tidal and river dynamics in polders by replacing the dike further inland. These projects are in many respects different from the nature conservation works, and therefore require a different, more process oriented approach. The main challenge is to find a compromise between ecological values and multiple human uses and demands upon the water system, such as safety from flooding, recreational use, agriculture, and housing projects on the waterfronts.
TL;DR: The above data suggest a promising role of these species in organic fertilizer (compost) production, feeding of herbivorous fishes, and in lowering the aquatic ecosystem nutrient load directly impeding eutrophication.
Abstract: Vegetation of five small water basins of the Becej fishpond complex (Yugoslavia) was surveyed. Phytocoenological features, abundance, covering and sociality served the basis for giving special attention to the four macrophytic species being dominant in the basins. All the four belong to a high emergent plant group (Phragmites australis TRIN. ex STEUD., Typha angustifolia L., T. latifolia L., and Schoenoplectus lacustris (L.) PALLA.). Total ash content and content of macro- (N, P, K) and microelements (Fe, Mn, Zn) were assessed. The highest ash values were obtained with rhizome and root. Also, significant macro- and microelement data were recorded in four analysed plant organs (rhizome and root, stem, leaf, and inflorescence). The highest nitrogen content (2.31 ± 0.12 %) was recorded in Ph. australis inflorescence, high phosphorus levels in T. latifolia inflorescence (0.29 ± 0.00 %), while the highest potassium content was found in Sch. lacustris leaves (13.83 ± 0.08 g kg -1 ). The highest micronutrient values were obtained with rhizome and root. The above data suggest a promising role of these species in organic fertilizer (compost) production, feeding of herbivorous fishes, and in lowering the aquatic ecosystem nutrient load directly impeding eutrophication.
TL;DR: The study demonstrates the need for an integrated interdisciplinary approach to river restoration and suggests full meander integration is recommended as the best solution for lowland rivers, such as the Morava, which actively transport bed material load.
Abstract: Modifications to large active rivers to aid navigation, reduce flood risk, improve land drainage or generate hydroelectric power have adversely affected river habitats and the hydrological connectivity between the river and its floodplain. Consideration of natural river processes helps to identify sustainable rehabilitation options within constraints imposed by the need to maintain required river functions and any restrictions imposed by space limitations due to floodplain development. A brief review of rehabilitation opportunities for active lowland rivers constrained by river functions is presented. This approach is used to identify suitable rehabilitation measures for two lowland meandering Slovak rivers, the Morava and Hron, which have been significantly influenced by engineering works. Both rivers differ in hydrological, morphological and ecological characteristics. Previous rehabilitation efforts based on locally targeted ecological and landscape restoration measures have actually exacerbated ecological degradation due to their failure to consider the abiotic processes which control river morphology. For rehabilitating cut-off meanders, full meander integration is recommended as the best solution for lowland rivers, such as the Morava, which actively transport bed material load. On the Hron River, an alternative method for improving the water regime and ecological quality of cut-off meanders is required due to engineering constraints. The study demonstrates the need for an integrated interdisciplinary approach to river restoration.
TL;DR: Results show that modified groynes can increase hydro-morphological dynamics, and thus, provide suitable habitats for B. velox, G. flavipes and other characteristic species.
Abstract: River regulation measures, such as groynes, severely alter hydro-morphological dynamics and subsequently habitat characteristics of riverbanks. In this study the influence of different groyne forms along the River Elbe on groyne field habitats was assessed using carabid beetle and macrozoobenthos assemblages prior to and after groyne adjustment. For analysis, 51 carabid species (n = 12,203), and 21 macrozoobenthos taxa (mean abundance 91.6 individualsm -2 ) were assessed. Species of both groups were significantly correlated with soil texture and reacted sensitively to hydro-morphological changes. The ground beetle Bembidion velox and the dragonfly Gomphus flavipes serve as indicator species for river-banks along the River Elbe. These autochthonous species are strongly adapted to sandy habitats and have become rare in German floodplains. Results show that modified groynes can increase hydro-morphological dynamics, and thus, provide suitable habitats for B. velox, G. flavipes and other characteristic species.
TL;DR: In this paper, the authors determined which are the characteristic algal communities coating the stems of Scirpus califomicus (MEY) STEUD in the Rio de la Plata.
Abstract: The objective of this study is to determine which are the characteristic algal communities coating the stems of Scirpus califomicus (MEY) STEUD in the Rio de la Plata. Taxonomic composition, disposition of the algae in the biofilm, spatial patterns of abundance and species diversity and life-form strategies were analysed. Samples of periphyton were taken in winter and spring 1999 and summer and autumn 2000, at five sampling sites. Physical-chemical characteristics were measured in summer and autumn 2000. Ten stems of the bulrush were cut randomly and the bottom 15 cm kept and put into a flask with distilled water. The biofilm was removed by brushing, integrating the material collected in each sampling site. The algae that comprised the biofilm analysed showed a simple architecture consisting of a layer dominated mainly by biraphid diatoms, with planktonic diatoms and/or filamentous chlorophytes entrapped in the surface film. The matrix analysed in this study corresponds to early stages of succession characterized by R-selected taxa, considered to be pioneer species and good colonizers in a disturbed system. During spring, winter and autumn, diatoms were dominant, but with different species compositions, while in summer green algae were abundant. The epiphyton of the bulrushes studied was characterized by a low proportion of epiphytic specimens sensu strictu (adnate, stalked and erect forms) exhibiting a high proportion of immigrants from the benthos and plankton.
TL;DR: A few of the ways river science is supporting river science to improve management strategies, influence the vast array of public and private institutions working in this basin, and more effectively direct the allocation of public dollars to conservation are explored.
Abstract: Ten years ago, The Nature Conservancy, recognizing the importance of large rivers to the biodiversity of the Midwest region of the United States, began a major conservation project on the Lower Illinois River. Since then the scope of the project has been expanded to incorporate a basin approach centered on the Upper Mississippi River and intended to rehabilitate ecosystems and abate threats at key sites that cross several spatial scales. A particular emphasis is on spatial strategies that result in cumulative downstream benefits. The use of the best available science, applied in an adaptive and accountable manner, is a fundamental principle of The Nature Conservancy and the Upper Mississippi River Project. This paper briefly explains the mission and work of The Nature Conservancy and then explores a few of the ways we are supporting river science to improve management strategies, influence the vast array of public and private institutions working in this basin, and more effectively direct the allocation of public dollars to conservation.
TL;DR: The results indicate that climate change has a significant impact on several characteristic riverine ecotopes and therefore on the ecological quality of floodplains, however, the effect of natural land use is more dramatic and may therefore compensate for some of the negative effects of climate change.
Abstract: Climate change, resulting in changes in temperature, precipitation, river discharge regime and sea level rise, may affect the ecosystems of the large rivers of the Netherlands in this century. This note discusses the method used to assess the impact of climate change on riparian ecosystems along the large rivers and presents the results of an application for the rivers Rhine and Meuse in the Netherlands. For this purpose, the effects of different climate change and land use scenarios on characteristic ecotopes have been compared with the current situation. The climate change scenarios were derived from the temperature rise estimation of the Intergovernmental Panel on Climate Change (IPCC). These have been translated into a sea level rise and changes in river discharge regime using results from earlier climate studies. Flood durations were derived by combining current contour maps of altitude and future sedimentation loads. For each type of ecotope a transition matrix has been developed to relate changes in flood duration and land use to changes in the types of ecotopes. The results indicate that climate change has a significant impact on several characteristic riverine ecotopes and therefore on the ecological quality of floodplains. However, the effect of natural land use is more dramatic and may therefore compensate for some of the negative effects of climate change.
TL;DR: This is the first quantitative survey of aquatic vegetation in the main channel of the River Danube near Baja (southern Hungary) in the Gemenc National Park and in an irrigation and drainage canal system on the left bank of the river.
Abstract: Aquatic vegetation was surveyed in the main channel of the River Danube near Baja (southern Hungary) in the Gemenc National Park and in an irrigation and drainage canal system on the left bank of the river. The main river was species-poor, compared to the oxbows and the canals, in which more species and much greater plant mass developed. Characteristic features were identified with regard to Relative Plant Mass, a measure of dominance, and the Mean Mass Index, which indicates the distribution pattern of species in a system. This is the first quantitative survey, which may form the baseline for future comparative investigations of the development of the aquatic vegetation in this section of the River Danube.