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.     

Natal environments of age‐0 paddlefish in the middle Mississippi River inferred from dentary microchemistry

Effective management and conservation of riverine fish species relies on identification of habitats that contribute recruits to fish populations. Paddlefish are an important commercial and recreational species inhabiting North American large rivers. However, despite the knowledge of adult paddlefish movement patterns in large rivers, their principal natal environments and early life dispersal patterns remain unknown. Paddlefish dentary microchemistry can be used to identify natal environment of fish in large river networks such as the middle Mississippi River (MMR) and tributaries. The goals of this study were to (a) use dentary microchemistry (strontium:calcium ratios; Sr:Ca) to determine natal environment and potential drift for age‐0 paddlefish collected from the MMR and (b) assess whether MMR reach or year of collection influenced the percentage of recruits originating from different rivers. Age‐0 paddlefish were collected during 2010–2011 from two reaches of the MMR (upstream and downstream of the Kaskaskia River confluence). Water samples from the MMR and tributaries (upper Mississippi, Missouri, Illinois, Osage, and Kaskaskia Rivers) were collected during 2006–2016. Water Sr:Ca differed among rivers, enabling identification of natal environment for individual fish using dentary core Sr:Ca. The MMR (44–69% of fish sampled) and Missouri River (25–45% of fish sampled) were the primary natal environments for age‐0 paddlefish across both river reaches and collection years. The upper Mississippi River and smaller tributaries contributed few recruits (<13% of fish sampled). Conservation of paddlefish populations should include maintenance or improvement of connectivity between river reaches used for spawning and juvenile rearing and stock assessments of riverine paddlefish may need to be conducted at a riverscape scale because multiple rivers can contribute to paddlefish recruitment in a particular river reach.     

Investigating the role of refuges and drift on the resilience of macroinvertebrate communities to drying conditions: An experiment in artificial streams

Flow intermittence occurs in an increasing number of streams, due to climate change, local land‐use alteration and water abstraction. In particular, droughts represent a new element in Alpine river regimes, and their ecological consequences are poorly explored. We here used artificial streams to investigate the resilience of macroinvertebrates to drought in Alpine streams based on the presence of pools (i.e., refuges) and drift (i.e., recolonization). Three flumes were selected: 1 with permanent flowing water (Control), whereas the other 2 (Drift+Pools, Only Drift) were subjected to 2 consecutive drought‐rewetting phases. Moreover, to better monitor the recolonization pattern by drift, quantitative samples of drifting taxa were collected using an additional flume (Incoming Drift). The effects of droughts on benthic invertebrate communities and their recovery were assessed in terms of composition, structure, diversity, and stability. Droughts dramatically reduced the taxa richness, especially with regard to the most sensitive and specialized macroinvertebrates, such as Ephemeroptera, Plecoptera, and Trichoptera taxa. Macroinvertebrate assemblages of the flumes that experienced drying phases were dominated by few generalist taxa and showed a higher degree of dissimilarity. Overall, no significant differences were observed in relation to the presence of pools, suggesting a limited role of this habitat in the recovery process. This finding suggests that in shallow and fast‐flowing Alpine lotic ecosystems the drift rather than pool availability represents the main driver of the macroinvertebrate resilience to droughts and provides insights into factors that can facilitate the recovery of aquatic communities after droughts.     

Influence of habitat heterogeneity and bed surface complexity on benthic invertebrate diversity in a gravel‐bed river

Maintaining or restoring physical habitat diversity is a central tenet of sustainable river management, yet a link between habitat and ecological diversity in fluvial systems has long remained equivocal. The lack of consistent evidence partly reflects the problems of characterizing habitat in ways that are ecologically meaningful. This paper assesses the influence of habitat heterogeneity and complexity on macroinvertebrate assemblages in a mountain gravel‐bed river. With the use of 0.1‐m resolution data obtained from an acoustic Doppler current profiler, heterogeneity and complexity in hydraulic conditions and bed topography were characterized using 13 metrics applied to 30 areas, each 1 m², with an invertebrate sample collected from each area. Turnover of invertebrate taxa (i.e., β‐diversity) between sampled areas was rather limited, but observed differences in diversity were related significantly to several metrics of habitat heterogeneity. Invertebrate abundance was related to habitat diversity, patch size coefficient of variation, and patch size, whereas the Shannon diversity was related to the number of patches and patch size. None of the habitat complexity metrics accounted for a significant amount of observed variation in invertebrate communities between sampled areas. The paper demonstrates that high‐resolution data can help reveal relationships between habitat and benthic invertebrate diversity.     

Assessing the benefit of flow constraints on the drifting invertebrate community of a regulated river

The downstream effects of hydroelectric dam operations on the abundance and diversity of the macroinvertebrate drift community of a regulated river were compared to that of an unregulated river, longitudinally and across three seasons. The regulated river operated under minimum flow and ramping rate (rate of change of flow) restrictions resulting in a ‘modified peaking’ regime, which means the facility could still peak, but at a slower rate and may not reach maximum turbine flows in the short time typically required to respond to market energy demand. The unregulated river had no dams or other water control structures. There was a trend of increasing abundance and diversity with distance from the dam on the regulated river, with no discernable trend along the unregulated river. While feeding guild proportions did not vary along the unregulated river, within the regulated river feeding guild proportions changed longitudinally as scrapers and collector gatherers increased, and filterers and predators decreased with distance downstream. The regulated river had similar or higher abundance across all seasons, with lower diversity in the spring. Seasonal average discharge was found to be lowest in summer on both rivers, with the regulated river benefiting from a minimum flow to help maintain higher abundance and diversity. Overall, our examination of the drifting invertebrate community on a regulated river support that operational constraints associated with modified peaking regimes helped mitigate the typical negative effects associated with river regulation. Copyright © 2010 Crown in the right of Canada and John Wiley & Sons, Ltd.     

Influence of Channel Morphology and Flow Regime on Larval Drift of Pallid Sturgeon in the Lower Missouri River

The transition from drifting free embryo to exogenously feeding larvae has been identified as a potential life‐stage bottleneck for the endangered Missouri River pallid sturgeon. Previous studies have indicated that river regulation and fragmentation may contribute to the mortality of larval pallid sturgeon by reducing the extent of free‐flowing river available to free embryos to complete ontogenetic development. Calculations of total drift distance based on mean velocity, however, do not address the potential for complex channels and flow patterns to increase retention or longitudinal dispersion of free embryos. We use a one‐dimensional advection–dispersion model to estimate total drift distance and employ the longitudinal dispersion coefficient as a metric to quantify the tendency towards dispersion or retention of passively drifting larvae. We describe the effects of different styles of channel morphology on larval dispersion and consider the implications of flow regime modifications on retention of free embryos within the Lower Missouri River. The results illustrate the complex interactions of local morphology, engineered structures, and hydraulics that determine patterns of dispersion in riverine environments and inform how changes to channel morphology and flow regime may alter dispersion of drifting organisms. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.     

维持河流健康生命研究

河流与健康相结合是可持续发展和社会价值进步的必然结果,维持河流健康已成为河流管理的一个热点问题。河流是有生命的,类似于有机生命体的健康,我们可以用健康来描述河流的生态状况,河流健康概念寻求利用生物或生态评价方法来完善传统的物理一化学评价方法。河流健康的度量对象包括：堤岸、河床、河水感观、水质指标、水生无脊椎动物指标和鱼类指标等。河流健康评价指标应包括：生态指标、物理化学指标、社会经济指标和人类健康指标。要维持河流健康,应加强河流水资源配置、水质、河岸地和河道等4方面的管理。     

Evaluation of the Effectiveness of a Living Shoreline in a Confined,Non‐Tidal Waterway Subject to Heavy Shipping Traffic

River bank erosion is a point of concern along navigable waterways because it increases the likelihood of bank failure. In non‐tidal and restricted fetch waterways, bank failure is mainly the result of extreme weather events and ship wave action. To counteract progressive bank erosion, nature‐friendly bank protection (a ‘living’ shoreline) has been installed in a stretch of the Lys (Belgium). It consists of off‐bank timber piling, which separates the fairway from the shallow water riverine environment, and a reed belt, planted at the base of the vertical cut bank. To evaluate its effectiveness, short‐term and long‐term field studies were carried out. The long‐term topographic survey did not reveal a clear difference in bank erosion rates between the surveyed nature‐friendly protected and naturally eroding embayments. Horizontal bank retreat could however not be linked directly to occasional flooding events and frequent ship wave action, although the latter's influence was inferred qualitatively. Based on velocity and turbidity measurements, the short‐term study pointed out the importance of an individual ship's wave action on bed and bank erosion behind the off‐bank timber piling. All ships were able to resuspend sandy bed sediments; yet, only a significant higher sediment volume was transported because of shipping traffic of the European Conference of Ministers of Transport (ECMT) classes IV and Va. If ship wave energy exceeded 45 Jm^?2, silty bank particles were dislodged from the river bank. Although validation of the results by longer term assessments may complete the physical insight in river bank erosion, the study indicated that this particular bank protecting configuration does not provide sufficient protection against ship wave action and does not adequately prevent further bank erosion. Copyright © 2014 John Wiley & Sons, Ltd.     

The relationship between geomorphic river adjustment and management actions over the last 50 years in the Upper Hunter Catchment,NSW, Australia

The installation of 517 river works in the upper Hunter catchment, New South Wales over the last 50 years is linked to geomorphic river adjustment and flood history at catchment and reach scales. Nineteen types of works are classified into three categories consisting of engineering, heavy machinery and vegetation works. Since 1952, a transition in techniques has been detected from engineering‐based approaches, to river training/maintenance, to more ecosystem‐based approaches. From the 1950s to the mid‐1980s extensive river engineering was undertaken. Projects were concentrated along laterally unconfined rivers and were generally implemented after major phases of geomorphic river adjustment. Neither the type of river nor the type of river adjustment guided the implementation of differing management techniques or their distribution in the catchment. A blanket approach was adopted, applying the same types of works across all types of river. Emphasis was placed upon concerns for bank instability rather than bed instability. Hence in many cases, river works addressed the symptoms (i.e. bank erosion) rather than the underlying causes of river change (i.e. bed incision). Since the mid 1980s, techniques have evolved towards vegetation‐based procedures. The development of more effective river rehabilitation programmes requires that greater consideration is given to proactive strategies which build upon an understanding of geomorphic river adjustments at the catchment scale. Copyright © 2008 John Wiley & Sons, Ltd.     

Seasonal variation in the composition of the drift below a peaking hydroelectric project

We used 0.5 m diameter nets to sample the drift downstream from a peaking hydroelectric project on the Caney Fork River, Tennessee. The relative contribution of the terrestrial, lentic, and lotic environments to stream drift varied seasonally. Stream benthos (primarily Chironomidae and Lirceus fontinalis) occurred in the drift throughout the year; however, their relative importance varied seasonally. Daphnia sp. from the reservoir also occurred in the drift year round with the highest densities in fall and spring when they were the predominant species in the drift. In summer, terrestrial insects apparently utilized exposed portions of the river bed during periods of no power generation. In June as the river stage increased following initiation of generation, adult terrestrial insects became a major component of the drift. Threadfin shad (Dorosoma petenense) dominated the biomass in the drift during December. Although the importance of stream benthos to fish populations is generally recognized, the contribution of the terrestrial and upstream reservoir environments to the forage base in the tailwater may also be important and should be considered in developing management strategies for tailwater fisheries.     

A GIS‐based approach to mapping probabilities of river bank erosion: regulated River Tummel,Scotland

This study explores the use of Geographic Information Systems (GIS) techniques for mapping river channel planform change and bank erosion probability. The method used is primarily based on an approach developed by Graf (Graf, W.L. 1984. ‘A probabilistic approach to the spatial assessment of river channel instability’, Water Resour. Res., 20 (7), 953–962), which proposed that bank erosion probability could be determined for any given cell on a floodplain by taking into account (i) its distance laterally and in the upstream direction to the active river channel, and (ii) a value representing flood magnitudes for the given period. In this study, Graf's method is refined by using a GIS approach and by incorporating the influence of geomorphic variables, such as river bank morphology, sediment type and floodplain vegetation, on bank erosion rates. In addition, the technique is applied to a wandering gravel‐bed river of roughly 80 m width, representing a different type and size of river to that used in Graf's study. Thus, the wider applicability of the technique is tested. In addition, the analysis here covers only a short time scale (1988–1994) compared with that used by Graf. The high temporal resolution of this study is enabled by the use of aerial photography and also by the substantial channel changes that occurred within this time period as a result of several high magnitude flood events. The results of the study indicate the usefulness and validity of the approach, particularly with regard to floodplain erosion hazard mapping and the assessment of the effects of altered flood regimes and land use. Copyright © 2000 John Wiley & Sons, Ltd.     

Minor local effects of a River Thames power station on the macroinvertebrate fauna

In July 1996, a survey of the macroinvertebrate fauna of the River Thames was undertaken in the vicinity of Didcot A Power Station, which is located on the right (south) bank of the river. The aim was to determine whether short‐range biological effects could be detected due to abstraction and discharge of cooling water. Sampling zones were selected upstream of the abstraction point (zone A), between the abstraction and discharge point (zone B), and below the discharge point (zone C). Five pond‐net and five dredge sampling units were taken from each bank in each of zones A, B and C and analyses were undertaken at BMWP family level. A total of 46 BMWP families were captured during the survey. Marginal pond‐net samples from the left bank had a significantly higher mean number of BMWP taxa than those from the right bank. These differences are thought to be due to the greater diversity of macrophytes and substrata on the left bank. In addition, there were lower numbers of BMWP taxa on the right bank of zone C compared with zone B (but not zone A), probably due to poor quality habitat. When the fauna from dredge samples in ‘control’ zone A was compared with zone B, there was no evidence on either bank of a deleterious impact on the fauna in zone B. Comparison of dredge samples from zone C with those from zones A and B, revealed no statistically significant differences in the number of BMWP taxa between zones C and A or between C and B on either bank. However, the first two dredge sampling units from the right bank of zone C, immediately downstream of the discharge point, had just five and 12 BMWP taxa, respectively, compared with a range of 17–28 taxa in all other dredge samples (on either bank of the three zones). These results correlated with a local change in dominant substratum to sand and associated fine particles, and suggest a very localized effect of the discharge on river‐bed morphology and hence on the fauna of the right bank in zone C. Copyright © 2000 John Wiley & Sons, Ltd.     

New insights into larval lake sturgeon daytime drift dynamics

Drifting post yolk-sac (PYS) lake sturgeon Acipenser fulvescens larvae were believed to seek refuge in substrate during daytime although there were no data to support this theory. There is growing scientific literature on important habitat, such as for adults and where eggs are spawned and hatch, however a gap remains in understanding duration of drift for PYS larvae, especially during daytime. This study was undertaken to find drifting PYS lake sturgeon larvae during the day in the Sturgeon River, Michigan, a clear yet tannin-rich river with a well-studied self-sustaining population. River substrates were mapped, and light, velocity, and depth data gathered to describe ‘believed’ refuge for larvae during daylight. From 2013 through 2016 nighttime drift samples (n = 463) for PYS lake sturgeon larvae were complemented with 143 daytime kick net samples and 43 daytime drift sets. No drifting larvae were collected in the daytime kick nets covering a variety of substrate types while over 1,600 PYS larvae were captured in drift nets at night, and 34 were captured in daytime drift sets. These 34 PYS larvae were in the previously unsampled thalweg in ~5% of surface light and at velocities of 0.24 to 0.57 m/s. Data suggest that drifting PYS lake sturgeon larvae do not stop and seek refuge during daylight but rather drift quickly and continuously downstream until suitable habitat is encountered. Measures of light, depth, velocity and thalweg presence combined with LiDar and Sonar mapping will be critical to understanding river suitability and restoration success for this species.     

The effect of the Grand Ditch on the abundance of benthic invertebrates in the Colorado River,Rocky Mountain National Park

We investigate herein the hypothesis that there is a significant relationship between bed particle mobility and benthic invertebrate abundance in the gravel‐bed channel of the upper Colorado River in Rocky Mountain National Park. A large diversion channel called the Grand Ditch normally diverts a significant portion (～50%) of the annual snowmelt runoff from the watershed northward out of the basin. In May 2003, a ～30‐m section of the ditch was breached, contributing substantially to the magnitude and duration of discharge in the Colorado River until the ditch breach was repaired in July of that year. As a result, all grain sizes in the river channel were mobilized, which contrasted sharply with the minimal gravel transport experienced during the exceptional drought of the previous year. Benthic macroinvertebrates were collected in the field using a Surber sampler at the same six locations for both years, and the number of individuals of the orders ephemeroptera (mayflies), plecoptera (stoneflies), trichoptera (caddisflies) and diptera (e.g. chironomids) was counted in the laboratory. The total number of individuals was 240% higher in 2003, and the proportion of mayflies in the samples increased from 25% in 2002 to 40% in 2003. In 2003, samples were also taken immediately upstream and downstream of a large flow obstruction in the channel in order to further isolate the relative importance of sediment transport against other variables affecting the stream habitat. Numbers of individuals for all taxa collected (particularly ephemeroptera and plecoptera) were nearly an order of magnitude higher at the upstream site than at the downstream, protected location. These results have important implications for the ecosystem management of streams within Rocky Mountain National Park and elsewhere. Copyright © 2008 John Wiley & Sons, Ltd.     

GRADIENTS IN THE BIOPHYSICAL STRUCTURE OF URBAN RIVERS AND THEIR ASSOCIATION WITH RIVER CHANNEL ENGINEERING

Urban rivers are often engineered to increase flood conveyance and stabilize channel size and position. This paper analyses habitat surveys of 180 urban river stretches of differing engineering type from four river basins (river Tame, West Midlands, UK; tributaries of the lower river Thames, UK; river Botic, Prague, Czech Republic; river Emscher, North‐Rhine Westphalia, Germany). Kruskal–Wallis tests identify significant differences in extent and/or frequency of flow types, bank and bed physical habitats, and vegetation characteristics associated with different styles of engineering. Principal Components Analysis identifies four key environmental gradients in the data set: sediment supply and retention; extent and diversity of in‐channel vegetation and riparian trees; bed and bank sediment calibre; flow type energy and complexity. These gradients discriminate stretches of differing planform, cross section and reinforcement and are significantly correlated with indices of degree and type of bank and bed reinforcement, pollution and presence of alien nuisance plant species. The analytical results illustrate statistically significant associations between different styles and levels of engineering intervention and the number and nature of physical habitats present in urban rivers. The results provide a basis for filtering sites for potential remedial measures prior to site‐specific surveys and modelling, for comparing sites and for tracking trajectories of change at sites that are subject to changes in channel engineering. They provide evidence that river condition and degree of engineering are not inversely related in a simple linear way, and that engineering of urban river channels, in the form of mixed, patchy reinforcement can contribute a great deal to habitat diversity where other controls on flow heterogeneity are more difficult to manipulate. Copyright © 2011 John Wiley & Sons, Ltd.     

堤基渗透变形与计算分析

建立了渗透变形初期的完整井和非完整井理想模型 ,通过有限元计算描述了渗透变形的发展过程。完整井模型中的涌砂在平面上可以是不连续的 ,除涌水口附近的区域外 ,近河床处在一定范围也可发生渗透变形。涌砂主要来自于涌水口的临河侧 ,随着砂的不断涌出 ,渗透变形的发展呈条带状向堤岸方向扩展 ,在一定条件下可与近河床处的渗透变形区相连通形成集中渗漏通道。非完整井模型中涌砂向深部的扩展是趋缓的 ,并最终将停止。因此 ,完整井模型中的涌砂是发展性的 ,而非完整井模型中的涌砂是非发展性的。     

上荆江沙市至郝穴河段近期河床演变及过洪能力分析

在大量实测河道资料基础上，分析了上荆江临江河段演变的基本规律、发展趋势及河道过洪能力，通过分析上荆江主流变化与岸滩变化的关系，深泓纵向冲淤变化和护岸段近岸河床冲淤变化，初步预测了上荆江河道发展趋势，最近还分析了荆江近期过洪能力的变化，通过分析后认为在三峡工程建成之前，荆江仍然面临着大洪水的威胁，因此必须重视河道观测工作，因势利导加强河势控制工程，改善近岸河床冲刷的现状，保障荆江地区的安全。     

Evaluation of δD and δ18O as natural markers of invertebrate source environment and dispersal in the middle Mississippi River‐floodplain ecosystem

Movement of invertebrates among large rivers, tributaries, and floodplain lakes or dispersal of adult aquatic insects from riverine or floodplain habitats may provide important subsidies to food webs in receiving habitats. Intensive sampling at habitat interfaces and artificial labelling are two approaches to assess freshwater invertebrate dispersal, but these are difficult to implement at a landscape scale. Natural chemical tracers have been used to track dispersal of fishes and marine invertebrates, but the potential applicability of stable isotope ratios as natural tracers of invertebrate dispersal in freshwater environments has not been assessed. We evaluated stable hydrogen and oxygen isotopes (δD and δ¹⁸O) as natural markers of source environment and dispersal of macroinvertebrates in the middle Mississippi River, tributaries and floodplain wetlands. Water and invertebrates were collected from 12 sites during 2007–2008. Water δD and δ¹⁸O differed among the river, its tributaries, and floodplain wetlands and were strongly correlated with invertebrate δD and δ¹⁸O. Variability in invertebrate δ¹⁸O rendered it ineffective as an indicator of invertebrate source environment. Mean δD of Mississippi River invertebrates differed from δD of invertebrates from floodplain wetlands; δD distinguished invertebrates from these two environments with >80% accuracy. Neither δD nor δ¹⁸O of aquatic insects changed following emergence from their natal site. Preservation method (ethanol or freezing) did not affect invertebrate δD or δ¹⁸O. Invertebrate δD may be a useful natural tracer of natal environment and dispersal in the Mississippi River‐floodplain ecosystem and other freshwater systems where spatial variation in water δD is present. Copyright © 2010 John Wiley & Sons, Ltd.     

Using Large Climate Ensembles to Plan for the Hydrological Impact of Climate Change in the Freshwater Environment

We explore the use of large ensembles of climate scenarios to inform climate change adaptation in response to hydrological impacts on the freshwater environment, using a sensitive chalk river in south east England to illustrate the approach. The climateprediction.net experiment provides large ensembles of transient climate series from 1920 to 2080. We use 246 transient climate series in the CATCHMOD rainfall-run-off model to develop large ensembles of plausible river flows for the River Itchen. This transient ensemble allows the exploration of how flows may change through the twenty-first century, and demonstrates the range of possible consequences for freshwater ecosystems, based on invertebrate community impacts. Hydrological modelling of flow sequences including abstraction allows the continued effectiveness of river support from groundwater to be assessed. A new environmental impact matrix considers the response of the freshwater ecosystem in the Itchen, concentrating particularly on macro-invertebrates. Through the century increasing numbers of models fail the flow targets, with a minority of models suggesting flows that would lead to irreversible change to the invertebrate community. The large ensemble provides a richer picture of the range of possible change, allowing managers to explore a range of different responses. The approach used is illustrative, but demonstrates that large ensembles may be of great value in improving the understanding of the possible impact of climate change, provided that they can be communicated effectively to decision-makers.