Colonization of periodically inundated interstitial habitats of an alluvial pond by invertebrates

The interstitial fauna of an alluvial pond on the floodplain of the Adour River, South-west France was sampled over a period of 13 months. The pond was connected to the adjacent river through phreatic flow and its water level varied in an annual cycle related to the level of the river. Monthly samples were taken from fixed points along five transects across the pond. The littoral zone was sampled between +20 and ?80 cm from the substrate surface. From the seasonal variations in the distribution and abundance of invertebrates, the dynamics of their colonization and decolonization cycles could be elucidated and related to the variations in the groundwater level. Eight different colonization/decolonization cycles were determined, each one being characterized by a ‘typical’ common species. These included both passive and active movements in response to the changes in water level. Many taxa were shown to have behavioural strategies which altered according to the stages of their life cycles. Most aquatic invertebrates were adapted to move into the most stable conditions at a given time of the year. Certain terrestial species were also shown to tolerate short periods of immersion.     

Vegetation,river management and land use in the dutch rhine floodplains

The floodplains of the lower Rhine are situated in a densely populated area of the Netherlands. Although they are used intensively the floodplains still fulfill important ecological functions. The lower Rhine is the downstream sedimentation zone of the River Rhine and its floodplains are characterized by river-transported vascular flora originating from southern and eastern Europe. Using multivariate methods data from previously published work and field data on grasslands and former river beds have been analysed to determine trends in ecological changes. The consequence of continued sedimentation and decreased erosion is an increased drying out of the floodplains. Excavation and recultivation of formerly excavated land does not reverse the losses in flora and vegetation. Statistically there is a negative relationship between the characteristic flora and recultivated land. The natural transversal river gradient also disappears, together with its characteristic ecological diversity. Aquatic environments in the floodplains have been changed completely since regulation work started in the 19th century. Most former river beds have disappeared due to silting up. Data on short-term vegetation succession confirm the long term analysis of map data.     

Spatial distribution of interstitial assemblages in the floodplain of the rhǒne river

Interstitial invertebrate assemblages of the Rhǒne River were studied at the scale of the entire alluvial plain. Ten stations, located in five former channels, were sampled with a Bou-Rouch pump at 50 and 100 cm depth. The chemical characteristics of the interstitial water allowed the differentiation of stations without hydrological connections with the subterranean habitats, stations fed by surface water coming through the bank sediments and stations fed by true groundwater. The faunal assemblages reflect the difference between connected and isolated stations but did not demonstrate any differences related to the origin of the water. In fact the interstitial assemblages are distributed along a gradient from the margin of the floodplain (stations with a high physical stability associated with the absence of flood periods) to the area close to the main channel regularly influenced by floods. These results demonstrate that both groundwater characteristics and the position of the station in the floodplain influence the spatial distribution of interstitial fauna in the alluvial valley of the Rhǒne River.     

Cross-channel distribution patterns of zoobenthos in a regulated reach of the tennessee river

The importance of substrate type and water depth was investigated in a regulated reach of a large, navigable river in the U.S.A. Benthic grab samples were collected in June and August, 1989, along two shore-to-shore transects in the lower Tennessee River, approximately 1.5 km downstream from Kentucky Lock and Dam. Diversity, averaged over all samples, was not significantly different from June to August. River depth of our samples, which ranged from 3.1 m to 6.5 m, significantly influenced macroinvertebrate density but had no detectable effect on the total number of taxa collected. Densities of flatworms, Asiatic clams, snails, isopods, and mayflies increased significantly with increasing depth, whereas the abundance of native mussels (Unionidae) and caddisflies decreased with depth. Substrate type (sand through cobble) influenced both the total number of taxa and the total number of organisms collected. Sample areas dominated by cobble contained significantly fewer individuals than areas composed predominantly of gravel substrate. Asiatic clams, the single most abundant species collected, were consistently more numerous on intermediate substrate sizes. In contrast, densities of native mussels, snails, and mayflies were not correlated with bottom type. Sample areas included relatively little mud and sand, resulting in relatively low numbers of oligochaetes and midges in our collections.     

Characteristics of seston in a regulated Appalachian Mountain river,U.S.A

Six size classes of seston were collected seasonally from the New River, Virginia, U.S.A., during three flow regimes: low flow, discharge changes resulting from daily cycles of hydroelectric power generation, and naturally occurring storm discharge cycles. Seston concentration and particle shape, density, and settling velocity were measured for all size classes, seasons, and flow regimes. Seston concentration, density, and settling velocity varied significantly with size class, season, and flow regime. Total concentrations ranged from a low of 0.47 mg litre^?1 during autumn base-flow to a high of 92.6 mg litre^?1 during a winter storm. Mean seston densities ranged between 1.60 and 2.02 g cm^?1, which is much lower than previously published measurements for rivers, suggesting that seston in the New River may be mainly organic-inorganic aggregates. Mean seston settling velocity was lowest during low-flow and hydroelectric discharges (0.10 cms^?1) and highest during storms (0.19 cms^?1). Seston particle shape varied significantly only with size class. The inability of a commonly used transport equation to predict transport during most discharge conditions suggests that, in some systems, seston concentration and transport may be less a function of discharge and power than of long-term seasonal and short-term discharge cycle effects on the density and size characteristics of seston.     

A numerical tool to integrate biophysical diversity of a large regulated river: hydrobiogeochemical bases. The case of the Garonne River (France)

This article presents the bases of a hydrobiogeochemical model of the Garonne River (southwest France) which has been developed to integrate physical and biological processes during summer low‐water periods. The physical part of this model is composed of a one‐dimensional unsteady hydrodynamic model, allowing the resolution of the Saint‐Venant equations, and a transport model which simulates downstream changes in solute concentrations. Biogeochemical processes are considered through the definition of functional compartments which make up the channel bed. These different compartments are defined both by the organisms involved in the solute transformation processes and by the physical and hydraulic characteristics of their habitat. Integration of these functional compartments within the model required investigations at different scales. The scale at which biological processes take place ranges from millimetres to metres. The scale of a reach, at which organization of the functional compartments along the river can be linked to hydrodynamic and morphological characteristics, ranges from 500 m to several kilometres. The regional scale is that at which homogeneous reaches can be integrated. A feedback between numerical results and field experiments has allowed improvements to in situ measurement to increase modelling accuracy. For example, the model allows estimation of variables, such as fluxes, that are difficult to measure in situ. The developed model can integrate various functional compartments and their biogeochemical functioning. Two application examples, focused on dissolved inorganic nitrogen, are presented in order to illustrate the numerical tool functioning: integration of equations on nitrification processes in the water body, and integration of consumption/production terms on epilithic biofilm resulting from in situ experimental mean values. The model we have developed constitutes a promising analytical tool that will be able to integrate previous and future studies. Copyright © 2002 John Wiley & Sons, Ltd.     

人工阶梯 深潭改善下切河流水生栖息地及生态的作用

本文通过野外试验研究了人工阶梯深潭对下切河流水生栖息地及生态的作用，试验河段位于西南山区的吊嘎河上150m侵蚀下切严重的河段，布置15级人工阶梯，对水流 (水深、流速、水面宽、流量)、河床底质、河床微地貌和水生底栖动物物种及数量变化进行了5个月监测。试     

Juvenile masu salmon in a regulated river

We examined the relationship between the physical environment and habitat use of juvenile masu salmon, Oncorhynchus masou, in the Nobori River in Hokkaido, Japan to provide a perspective for the conservation of fish habitat in regulated streams. The study was undertaken during the autumn and winter, with an emphasis on the hierarchy of three spatial scales: microhabitat, channel‐unit and reach scales. The microhabitat‐scale analysis indicated juvenile masu salmon preferred a midstream habitat type, with a greater depth (Avg. ± SD: 35.4 ± 14.2 cm) and high (43.4 ± 23.1 cm s^?1) and uniform current velocities during the autumn, and a channel margin habitat type with a moderate current (about 20 cm s^?1) and submerged cover during winter. In addition, different cover types have different roles in determining juvenile salmon distributions during winter. Grass cover had extremely high carrying capacities, whereas coarse substrate cover provided winter habitat for larger juvenile salmon. Channel‐unit scale analyses showed that abundance of juvenile salmon tended to be higher in pools than runs in the autumn through winter. Reach‐scale analysis showed that abundance and mean body length of juvenile salmon significantly differed between differently regulated reaches during winter, associated with the dominant cover type in each reach. This study demonstrated that the habitat conditions determining juvenile masu salmon distribution differ according to the season and scale of analysis. Therefore, for conservation of fish communities, it is important to evaluate and conserve or create fish habitats in regulated reaches, with a focus on the hierarchy of spatial scales and seasonal differences. Copyright © 2007 John Wiley & Sons, Ltd.     

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.     

Habitat used by Macrhybopsis chubs associated with channel modifying structures in a large regulated river: implications for river modification

We examined use of channel modifying structures (CMS; e.g., engineered rock dikes, channel sandbars) and their associated smaller spatial‐scale habitats (SSH) on lower Missouri River, USA, by speckled chub (Macrhybopsis aestivalis), sicklefin chub (M. meeki) and sturgeon chub (M. gelida) from June through October, 2006 to identify important habitat characteristics that could aid conservation. We sampled chubs primarily in six CMS types: L‐dikes, wing‐dikes, kicker dikes, rootless dikes, channel sandbars and bank‐lines. Ninety‐three per cent of chubs were collected from L‐dikes, wing‐dikes and channel sandbars. Unidentifiable Macrhybopsis chubs (UHY) were less than 35‐mm TL, were collected early in the sampling season and were most associated with L‐dikes where mean bottom current velocity was slow (0.07 m/s). Chubs large enough to be identified to species were associated with large channel sandbars where mean bottom current velocity was faster (0.34 m/s). Chubs from wing‐dikes were more abundant in shallow water (<1.2 m deep) adjacent to bars than in deeper (>1.2 m deep), open‐water areas (p = 0.007). Month accounted for 54% and CMS with SSH 18% of explained variation in chub species distribution and abundance. Our results demonstrate that CMS in the contemporary lower Missouri River channel provide multiple habitats for multiple life‐stages of Macrhybopsis chubs (e.g., nursery and post‐nursery habitats). L‐ and wing‐dikes may provide surrogate nursery habitats for chubs where in‐channel slow‐velocity areas were lost after river channelization. Managing CMS to address life history stages and an ecologically appropriate proportion and distribution of dike to channel sandbar habitats may be critical for conservation of native Macrhybopsis chubs in lower Missouri River. Published in 2008 by John Wiley & Sons, Ltd.     

嫩江北引渠首江道整治的试验研究

拉哈渠首枢纽是黑龙江省嫩江干流上的一个重要的无坝引水工程， 近年来由于渠首江道的演变已严重影响引水。为此， 采用动床河工模型进行了较为深入地研究， 解决了模拟宽滩河道和在缺乏实测资料的情况下模拟推移质运动等技术难点， 揭示渠首河道的演变规律， 在大量方案试验的基础上， 提出了整治措施。     

裁弯河道内生物栖息地改造及生态流量估算EI北大核心CSCD

为探讨砾石群布置对裁弯取直河道内生物栖息地的改造效果,并估算改造河段的生态流量,以江西金沙溪为研究区域,选取鲢鱼为研究对象,采用正交试验法和数值模拟方法,研究了最优砾石群的布置形式,并采用生物栖息地法估算了河道内生态流量。结果表明:流量对裁弯河道生物栖息地加权可用面积(WAU)的影响最大,砾石堆积体边长次之,堆积体间距最小,单体砾石边长20 m、砾石间距9 m为最优砾石群布置形式;在原河道平滩流量条件下,裁弯取直后河道内WAU较原河道减小约30%,布置最优砾石群后,裁弯河道内WAU较原河道增加20%,生物栖息地自然化改造效果明显,且不影响河道行洪能力;原河道基本生态流量为50 m^(3)/s,目标生态流量为718 m^(3)/s,改造后裁弯河道基本生态流量为218 m^(3)/s,目标生态流量为618 m^(3)/s。     

Spring ecotone and gradient study of interstitial fauna along two floodplain tributaries of the river rhǒne,France

The hyporheic zone of two small tributaries of the upper Rhǒne River where they cross the floodplain (approximately 2 km wide) was studied. The streams originate in karstic areas which directly border the floodplain. The surveys were conducted at 11 sites along the course of the two tributaries at a depth of 50 cm in bed sediments. Ten litre samples were collected six times a year with a Bou-Rouch sampler. The paper examines the distribution of interstitial communities along two transverse (floodplain) profiles, defines the spring ecotone, analyses the heterogeneity, and underlines the importance of the tributaries in the functioning of the floodplain. A comparison between the spatial distributions of fauna and organic matter content along the two profiles underlines the important relationships between the groundwater and surface environment, and makes it possible to differentiate parts of the floodplain where the exchanges are most intense (interstitial spring, karst/floodplain interface). Along the longitudinal course of these streams, we observe the influence of groundwater circulation on community structure/i.e. the interactions between stream channel, alluvial aquifer and adjacent karstic aquifer.     

Ecological strategies successfully predict the effects of river floodplain rehabilitation on breeding birds

To improve the ecological functioning of riverine ecosystems, large‐scale floodplain rehabilitation has been carried out in the Rhine–Meuse Delta since the 1990s. This paper evaluates changes in abundance of 93 breeding bird species over a period of 10 years in response to rehabilitation, by comparing population changes in 75 rehabilitated sites with 124 non‐rehabilitated reference sites. Such quantitative, multi‐species, large‐scale and long‐term evaluations of floodplain rehabilitation on biodiversity are still scarce, particularly studies that focus on the terrestrial component. We try to understand the effects by relating population trends to ecological and life‐history traits and strategies of breeding birds. More specifically, we try to answer the question whether rehabilitation of vegetation succession or hydro‐geomorphological river processes is the key driver behind recent population changes in rehabilitated sites. Populations of 35 species have significantly performed better in rehabilitated sites compared to non‐rehabilitated floodplains, whereas only 8 have responded negatively to rehabilitation. Differences in effects between species are best explained by the trait selection of nest location. Reproductive investment and migratory behaviour were less strong predictors. Based on these three traits we defined eight life‐history strategies that successfully captured a substantial amount of variation in rehabilitation effects. We conclude that spontaneous vegetation succession and initial excavations are currently more important drivers of population changes than rehabilitation of hydrodynamics. The latter are strongly constrained by river regulation. If rehabilitation of hydro‐geomorphological processes remains incomplete in future, artificial cyclic floodplain rejuvenation will be necessary for sustainable conservation of characteristic river birds. Copyright © 2010 John Wiley & Sons, Ltd.     

Large wood aids spawning Chinook salmon (Oncorhynchus tshawytscha) in marginal habitat on a regulated river in California

To determine whether large wood (LW, ≥1‐m length, ≥10‐cm diameter) plays a role in Chinook salmon (Oncorhynchus tshawytscha) redd (i.e. egg nest) placements in a regulated, Mediterranean‐climate, medium‐sized river (where channel width is less than the upper quartile of length of potential instream wood pieces), characteristics of 527 large wood pieces, locations of 650 redds, and mesohabitat delineations (riffle, run, glide, pool) were collected during a spawning season along a 7.7 km reach directly below Camanche Dam on the Mokelumne River, CA. LW was regularly distributed across the study reach an average 70 LW pieces km^‐1. Some LW clustering was evident at islands and meander bends. Spawners built 85% of redds within one average channel width (31 m) of LW. Spawners utilized LW within a 10 m radius 36% of the time in the upper 3 km rehabilitated reach, and 44% of the time in the lower 4.7 km marginal habitat reach. A greater percentage of LW was utilized in riffles in the upper 3 km reach where 90% of redds were built, while a larger percentage of spawners used LW in riffles in the lower 4.7 km reach. LW‐redd interactions occurred at greater rates than by random chance alone in the lower 4.7 km reach, which implies that LW aids spawning in marginal habitats. River managers and salmonid spawning habitat rehabilitation (SHR) projects should take LW additions into consideration as an important component of river rehabilitation. Copyright © 2010 John Wiley & Sons, Ltd.     

Effects of gravel augmentation on macroinvertebrate assemblages in a regulated California River

Enhancement projects within anadromous salmonid rivers of California have increased in recent years. Much of this work is intended as mitigation in regulated streams where salmon and steelhead spawning habitat is inaccessible or degraded due to dams, water diversions and channelization. Little research has been done to assess the benefits of spawning habitat enhancement to stream organisms other than salmon. We monitored benthic macroinvertebrates at seven spawning gravel augmentation sites in the lower Mokelumne River, a regulated stream in the Central Valley of California. Placement of cleaned floodplain gravel decreased depths and increased stream velocities. Benthic organisms colonized new gravels quickly, equalling densities and biomass of unenhanced spawning sites within 4 weeks. Macroinvertebrate species richness equalled that of unenhanced sites within 4 weeks and diversity within 2 weeks. Standing crop, as indicated by densities and dry biomass, was significantly higher in enhancement sites after 12 weeks than in unenhanced sites and remained so over the following 10 weeks. Although mobile collector/browsers initially dominated new gravels, sedentary collectors were the most common feeding category after 4 weeks, similar to unenhanced sites. These data suggest that cleaned gravels from adjacent floodplain materials, used to enhance salmonid spawning sites, are quickly incorporated into the stream ecosystem, benefiting benthic macroinvertebrate densities and dry biomass. Copyright © 2005 John Wiley & Sons, Ltd.     

Benthic macroinvertebrate communities in nonregulated and regulated waters of the clearwater river,Idaho, U.S.A.

Benthic macroinvertebrates were examined over a two-year period in nonregulated, regulated, and semiregulated reaches of the Clearwater River in northern Idaho. Macroinvertebrate communities in the nonregulated reach above Dworshak Reservoir were taxonomically diverse at all stations. In contrast, the macroinvertebrate community in the regulated reach of the North Fork of the Clearwater River (NFCR) was severely altered with high macroinvertebrate abundance and low taxa richness (2 to 8 taxa). Orthoclad chironomids dominated this reach composing between 68 and 99 per cent of total benthic invertebrate numbers. The mayfly Ephemerella infrequens was the only other macroinvertebrate to be abundant in the regulated reach. The major factors contributing to the simplified macroinvertebrate community are reduced habitat diversity, fluctuating water levels, altered thermal regime, and possibly an altered food supply. The effects of the dam were mitigated in the semiregulated Mainstem of the Clearwater River (MSCR) due to the merger of a nonregulated fork entering 2.5 km downstream from the dam. The macroinvertebrate community in the semiregulated MSCR was more complex than the regulated reach with a community structure resembling that found above the reservoir.     

河床枯萎的临界阈研究

本文首先从河流地貌临界学说的观点出发, 解释了河床枯萎的概念. 然后, 以黄河下游近期河床演变特性为例, 阐释了河床枯萎的机理以及由此带来的"小水大灾"效应, 研究了造床流量、河相关系在新的水沙条件下的变化规律, 提出了枯萎造床流量的概念. 最后, 运用河道水沙数学模型, 初步探求了黄河下游河道萎缩的外部临界阈值.     

长江河道信息服务系统二维信息查询模块开发

介绍了长江河道信息服务系统二维信息查询模块的主要功能与特点.该模块将联动、缓冲区等多种思想和技术应用于查询系统中,不仅使系统的查询功能简单化,同时也很好的解决了用户对于设计洪水位、岸线利用等信息的实时性、随意性查询的需求.使得系统在满足基本属性查询的同时,又能通过一些专用菜单以及创新性的功能设计,对存储于数据库中的信息进行整合利用,具有便捷高效、功能全面、针对性强等特点.     

浦东机场跑道工程江砂开采及对河道的影响

为满足浦东国际机场工程建设需要,从有利于河势和航运等角度出发,选择了长江口南槽江亚南沙南侧、九段沙保护区外侧的砂源区作为工程采砂区,并拟定采砂方案。采用delft 3D模型分析采砂前后工程区附近的流场变化。并从河势、防洪、水环境、通航、航道和生态等方面分析了采砂对长江口南槽河段的综合影响,论证采砂的可行性。通过分析得出采砂对长江口河道基本无影响。