MACROINVERTEBRATE COMMUNITIES OF THE DOUBS RIVER PRIOR TO COMPLETION OF THE RHINE–RHONE CONNECTION

The Rhine–Rhône connection project concerns the part of the Doubs River between Montbéliard and Dôle (France), i.e. downstream from the confluence of the Allan River. In order to update our knowledge of the benthic macroinvertebrate communities of the Doubs River, three types of aquatic environments of this hydrosystem were sampled (main channel, backwaters and the Freycinet canal). Hydraulic characteristics are the most explanatory environment variables of lotic macroinvertebrate distribution of the Doubs hydrosystem. The aquatic fauna of the Doubs River is varied due to the diversity of biotopes, microhabitats and current velocities. The lotic aspect is well defined. Rheophilic taxa are present in the main stream in riffle areas or located downstream from weirs where the current velocity is rapid (>75 cm s⁻¹). The physics of flow (‘stream hydraulics’) create the richness of habitats and thereby the biological diversity. Backwaters have a relatively high richness, similar to that of stations in the main stream located in the same sector. Conservation management must be oriented towards the present ecological situation of the Doubs River, i.e. that of a lotic ecosystem with active connections with its backwaters. The primary goal from a conservation perspective must be the maintenance and the improvement of areas highly sensitive to disturbances.     

Invertebrate drift patterns in a regulated river: dams,periphyton biomass or longitudinal patterns?

Macroinvertebrate drift was sampled at 15 sites along the Tongariro River, New Zealand above and below two hydroelectric dams. Sixty‐seven invertebrate taxa were collected in the drift. Trichoptera (31) were the most diverse, followed by Diptera (13), Ephemeroptera (8) and Plecoptera (8). However, chironomidae were the numerically dominant taxa in the drift throughout the river and represented over 80% of all animals collected. Of these, Orthocladiinae and Diamesinae were the most abundant. Taxonomic richness declined with distance downstream and peaked at sites with intermediate levels of periphyton biomass. The per cent of Ephemeroptera, Plecoptera and Trichoptera (EPT) was 3–4 times higher in the unregulated section of the river and declined exponentially with both distance downstream and increase in periphyton biomass, but densities were similar along the river. Of the measured environmental variables periphyton biomass was most closely linked with drift community structure. Periphyton biomass was six times higher in the lower section of the river than the upper unregulated section. The autocorrelation between periphyton biomass and distance downstream complicates the interpretation of results. However, because of the distinct differences between above and below dam sections of river in periphyton biomass and the strong link between it and invertebrate drift we suggest that the alteration of flow patterns by the hydroelectric dams and the associated shift in periphyton biomass is the most likely explanation for invertebrate drift patterns in the river. Copyright © 2009 John Wiley & Sons, Ltd.     

Are protected areas effective in preserving Alpine stream morphology and biodiversity? A field study in the oldest Italian National Park

Global changes and local pressures related to the exploitation of water resources are significantly reducing streams' biodiversity and threatening their ecological balance. This trend concerns both the lowland rivers flowing in densely populated areas and the mountain headwaters, where the effects of global change are dramatically evident and often accompanied by alterations in river hydro-morphology. From mountains to lowlands, regulation and morphological alterations such as bank reinforcement, water abstractions, dams, and weirs are among the most significant threats for river ecosystems. Protected areas and especially large national parks constitute an effective strategy to face the loss of biodiversity, but little is known about their effectiveness regarding lotic environments. To examine the recent trend in aquatic communities in Alpine protected areas, we carried out biological sampling of benthic communities and hydro-morphological status assessment in 12 high-altitude streams within the oldest Italian National Park, that is, the Gran Paradiso National Park, located in the heart of the Western Alps, and we compared results with a previous survey performed in 2005, by keeping the same experimental design. Our results detected minimal changes in the hydro-morphology of the studied watercourses. Biomonitoring indices associated with benthic communities likewise did not provide evidence of significant differences. Conversely, diatom communities were more uniform in 2020 compared to 2005, and a slight species turnover occurred over the 15-year interval. Despite this, our findings underline the effectiveness of protected areas for the conservation of running water environments because they limit hydro-morphological alterations, thus increasing the resilience of aquatic communities to climate change.     

The impact of river regulation on the lotic macroinvertebrate communities of the lower rhǒne,France

Channelization and the construction of 12 dams on the Lower Rhǒne during the last 30 years increased the morphological and biological effects of 19th century embanking along the river. These trends were demonstrated on the main channel, i.e. the central axis of the alluvial floodplain, by the synchronic study of the benthic macrofauna of six lowhead hydroelectric impoundments. The variability of the most significant taxa was investigated by an ANOVA, and the data-samples matrix was processed with a Principal Components Analysis in order to analyse the communities organization and their significance. The benthic macroinvertebrate communities of the channel include some lentic potamic species topographically related with this kind of river (metapotamon), as well as eurytopic and pollution-tolerant species. Thus, the Lower Rhǒne has become a slow potamic river, in the same way as other large mid-European rivers. Flow velocity appears to be the most important structural factor in a large regulated river. The homogeneity of the macroinvertebrate communities and the absence of longitudinal typology show that, in a very intensely regulated river, the River Continuum Concept is too theoretical, and the disturbing effects of dams on longitudinal changes and species response to regulation must be taken into account.     

荆江河道水流运动特性研究

利用长江防洪实体模型,全面系统地对荆江不同流量条件下的各水力要素进行测量,并结合三峡水库蓄水以来的水沙、地形资料,分析了荆江河段水流运动的基本规律和近期变化的特点,在此基础上对荆江不同河道整治方案进行了研究,并针对不同河型提出了具体的河势控制措施。研究成果表明 : 通过试验分析较详细地掌握了荆江水面纵比降、断面宽深比、流速分布及水流动力轴线变化等水力要素变化的特点,揭示了荆江河段水流运动规律,并为河道（航道）整治工程提供了科学依据。     

WEIR POOL SURCHARGE AND A CORRESPONDING INCREASE IN ALGAL BIOFILM COMMUNITY DIVERSITY IN THE LOWER RIVER MURRAY,SOUTH AUSTRALIA

Lowland rivers impounded by weirs are often operated to provide stable water levels. In the lower River Murray, stable water levels promote algal biofilms dominated by stalked diatoms, filamentous green algae and Cyanobacteria. In summer 2005–2006, the Lock 5 weir pool was surcharged for environmental benefit. Algal biofilms grown on artificial substrates were compared to the following year when the water level remained stable. On both occasions, substrates were fixed at 300‐mm depth in the river channel and a connected wetland. During the surcharge, additional floating substrates were deployed to control for the change in water level. The algal communities that developed during both years were dominated by diatoms. A greater diversity in the biofilm community was evident during the 4‐month surcharge when compared with the following year. This was due to a much greater change in algal biofilm community composition over the 4 months of the surcharge, compared with biofilms grown during a period of stable water level, when the community changed little after 1 month. The lack of difference between fixed and floating substrates suggests that the change in water level was not responsible for the difference between the surcharge and stable level biofilms. Possible reasons for the difference between years include light, nutrients and water temperature. Although the effect of the surcharge could not be definitively defined, these results provide some evidence that weir pool surcharge may be used to improve algal biofilm diversity when compared with the current stable water level regime. Copyright © 2011 John Wiley & Sons, Ltd.     

新安江河段行洪流量的分析

分析新安江、兰江、富春江不同频率设计洪水及洪水组合,根据新安江水库目前上、下游状况及规划工况拟定各种调洪方式,进行新安江水库洪水调度计算,综合确定新安江河段流量,为建德市城市防洪工程建设提供依据。     

The distribution and macrofauna of ponds in stretches of an alpine floodplain differently impacted by hydrological engineering

The purpose of this study was to describe the impact of hydrological engineering on distribution, morphology and macrofaunal community composition of ponds in an alpine floodplain. The study was conducted in 1995 with the study sites being located on the Isar floodplain (Bavaria, Germany). The density of ponds was highest in a bypassed section of the floodplain with a residual flow regime and unrestricted peak floods (up to 40 ponds per river kilometre). In a channelized section and downstream of a reservoir, density was much lower. In 1995, about one third of the ponds were removed by floods or dried out in summer. About the same fraction was generated as a result of flood events. The composition of the macroinvertebrate and vertebrate faunas of 59 ponds was investigated. Cluster analysis classified the ponds into four groups. One of the faunal types was limited to ponds generated by the 1995 floods, where only a few predominantly rheophilic species occurred. The other types represented older successional stages and were inhabited by more species‐rich faunas composed mainly of Odonata, Heteroptera and Coleoptera. In the channelized stretch of the Isar floodplain, and downstream of the reservoir only a single pond was generated by the 1995 floods; this caused a lower abundance and diversity of pond types. Copyright © 1999 John Wiley & Sons, Ltd.     

长江环境流量问题及管理对策

基于国内外环境流量研究成果和实践经验,以及长江生态环境敏感区与河道内水生生物特点,对我国环境流量的定义及内涵进行了论述,对长江存在的环境流量问题进行了分析,并在此基础上提出了保证环境流量实现的工程和非工程措施。研究表明：生态监测、流域规划、水库联合调度及生态补偿机制等非工程措施是保证环境流量实现的关键。     

Use of mesohabitat‐specific relationships between flow velocity and river discharge to assess invertebrate minimum flow requirements

The benthic macroinvertebrate community in the sixth order lowland River Spree (Germany) was investigated in order to assess ecological effects of a flow reduction. The benthic habitat was composed of visually distinguishable mesohabitats. Eight mesohabitats were delineated, Dreissena‐bank, unionid mussel bed, rip‐rap, coarse woody debris (CWD), alder roots, stable sand, shifting sand and mud. The mesohabitats differed in their physical structure and hydraulic nature. These functional habitats were partly inhabited by distinct invertebrate assemblages. The use of mesohabitat‐specific relationships between flow velocity and discharge seemed the most appropriate approach in order to assess the impact of flow reduction on lotic fauna. In combination with the species‐specific optima and tolerances for flow velocity, this approach can be used to develop a minimum flow level that mitigates the effects of flow reduction and enables the persistence of rheophilic invertebrates in their specific mesohabitat. Copyright © 2001 John Wiley & Sons, Ltd.     

深圳河一、二期河道治理后水沙特性变化分析

深圳河一、二期河道治理工程塑造了新的河道形态,改变了深圳河潮流特征和泥沙输移特性.实测资料分析表明,深圳河治理后,河道阻力大大减小,潮波易于上溯,有利于涨潮流挟带泥沙进入深圳河而不利于落潮流将泥沙挟带出河口.这一变化将对深圳河的河道冲淤产生根本影响.