Channel response to sediment replenishment in a large gravel‐bed river: The case of the Saint‐Sauveur dam in the Buëch River (Southern Alps,France)

The Saint‐Sauveur dam was built in 1992 in the middle section of the Buëch River. Downstream of the dam, a channel incision by several meters was observed. A gravel replenishment operation was planned in order to restore the active channel. An equivalent of two times the mean annual bedload‐transport capacity (43,500 m³) was replenished downstream of the dam in September 2016. The aim of this paper is to quantify morphological change associated with sediment remobilization in order to evaluate the efficiency of the restoration works. The monitoring was based on a combination of (a) change detection using sequential high‐resolution digital elevation models (from airborne LiDAR data), (b) bedload tracing using active ultrahigh‐frequency radio‐frequency identification technology, and (c) complementary field surveys of channel grain‐size distribution and morphology for bedload‐transport computation. Field monitoring allows us to capture a net aggradation along a 2‐km reach after the first post‐replenishment flood. A sediment balance analysis was performed to back‐calculate bedload supply coming from the sluicing operation during the flood. Although the sediment replenishment operation clearly had a positive impact on the morphological conditions of the starved river reach, the effective bedload supply from artificial berms (22,650 m³) was insufficient to initiate substantial channel shifting along the restored reach and a subsequent amplification of the sediment recharge. The combination of high‐resolution topographic resurveys and sediment tracing was successful to evaluate the downstream propagation of sediment replenishment effects.     

淡水环境中微塑料的分布及生物毒性研究进展

塑料污染问题已经成为影响水生生态的世界性难题,微塑料作为一种新型污染物,其对水生生态安全的影响也愈发突出.对国内淡水环境中微塑料的分布状况进行归纳总结,对其分布、来源及影响因素进行分析;同时,归纳总结微塑料对淡水生物(淡水藻类,淡水浮游动物,鱼类等)的毒害作用研究进展,讨论微塑料对淡水水生生物造成的危害,对未来微塑料的...     

浅谈土工试验中室内大型剪切与小型剪切试验

以实际工程为例 ,对土工试验中室内大型剪切与小型剪切试验进行了比较分析 ,提出了两种试验结果的适用条件。     

The effects of drying and re‐flooding on nutrient availability in ephemeral deflation basin lakes in western New South Wales,Australia

We examined the response of nutrient concentrations to the drying and re‐flooding of ephemeral deflation basin lakes (EDBL) in western New South Wales, Australia. As lakes dried total nitrogen (TN) and total phosphorus (TP) concentrations increased. TN concentrations increased more quickly and TP concentrations increased more slowly than could be attributed to evaporation alone. This suggested that additional nitrogen was being sequestered from the atmosphere or sediments and that some phosphorus loss to the sediments was occurring. Concentrations of nitrogen oxides (NOx) and filterable reactive phosphorus (FRP), however, declined as lakes dried, suggesting a tighter coupling of nutrient release and uptake mechanisms. Inorganic nutrient concentrations rose sharply in response to re‐flooding in all lakes. Evidence is provided to suggest that post‐flood nutrient pulses are the net result of both riverine inputs and sediment releases and that the relative significance of either may be influenced by regulation. Copyright © 2002 John Wiley & Sons, Ltd.     

Advection,growth and nutrient status of phytoplankton populations in the lower River Murray,South Australia

To investigate the link between river flow, nutrient availability and development of algal blooms, growth rates of the major phytoplankton species were examined in situ in the lower River Murray, South Australia over the 1994/1995 summer. Eight sites were selected over a 54 km reach between Lock 1 and Nildottie and growth rates estimated by monitoring mean cell density in time‐aligned parcels of water as they travelled downstream. Discharge at Lock 1 during the period of study (3000–5000 ML day⁻¹) typified summer entitlement flows to South Australia. A large, shallow floodplain lake (lagoon), with an hydraulic connection to the river, supported a large population of cyanobacteria in summer, but inputs to the main channel did not substantially affect the abundance and composition of river phytoplankton. Mean net growth rates of Anabaena circinalis and A. flos‐aquae f. flos‐aquae were 0.132 and 0.176 day⁻¹, respectively, although individual rates varied from positive to negative. In contrast, the mean growth rate of the filamentous diatom Aulacoseira granulata was −0.15 day⁻¹, reflecting a decrease in population size with advection downstream. Mean cell densities of the three species did not exceed 5000 cells mL⁻¹ throughout the study. Growth bioassays conducted in the laboratory indicated that nitrogen was often the nutrient limiting algal growth, although it was not established whether nitrogen was limiting in situ. A conceptual model is presented, linking these findings with those of other work on the lower River Murray, to summarize the physical and chemical environmental factors governing the abundance of cyanobacteria in this reach of the river. Copyright © 2000 John Wiley & Sons, Ltd.     

乌鲁木齐河流冰椎的形成特征及其分布

通过对河冰椎多年系统观测，对比分析其形成和发育大致经过冰椎形成、发育、稳定、融化冻结和消亡５个阶段；出山口以上冰椎储量通常可达１７８２×１０６ｍ３，折合径流量为１５３１×１０６ｍ３；冰椎与稳定负温期的积温－ｔ℃及水源补给形式有较高的相关性，为人工调蓄利用冰椎提供了科学依据     

Genetic variability and population structure of dorada (Brycon moorei sinuensis Dahl) in the Sinú River, Córdoba, Colombia

Six microsatellite loci, isolated for Piaractus mesopotamicus (Characidae, Serrasalminae) were used to evaluate the genetic variability of the dorada (Brycon moorei sinuensis, Characidae, Bryconinae) population in the Sinú River, Córdoba, Colombia, and to facilitate management recommendations for this species. The six loci were polymorphic, with an average of 9.25 alleles for dimeric loci (Pme2, Pme4, Pme5 and Pme20), and five alleles for trimeric loci. Tests for linkage disequilibrium were used to determine that the six loci had an independent distribution. The observed heterozygosities were lower than the expected ones for all loci, and the population was not in Hardy–Weinberg equilibrium because of heterozygote deficiency. F‐statistics indicated inbreeding and a low population substructure. The homogeneity of the population was confirmed by high values of genetic flux and an agglomerated representation of the individuals, based on factor correspondence analysis. Recent bottlenecks were detected for three sample sites under the assumption of an infinite allele mutation model. Proposals for the management of the dorada population are made and validated with a genetic simulation.     

Factors affecting the distribution and abundance of aquatic plants in a navigable Lowland river; the River Nene,England

Investigations were conducted into the causes of a decline in the abundance of rooted aquatic plants in the River Nene. These were formerly troublesome to navigation and obstructed summer storm flows and were regularly cut by Anglian Water until 1976. After 1977 plant growth caused only localized problems so cutting ceased. An investigation into the causes of the plant decline was initiated in order to provide predictions for management decisions about the future use of machinery and personnel. It was concluded that there was a natural loss of plants by scouring in the abnormally high flows of 1976/7 winter. The regular pattern of maintenance dredging, which had been implemented following water industry reorganization in 1974, was shown to suppress abundance for at least five years after dredging. These two sequential events had lowered abundance over the navigable Nene to levels which no longer warrant weedcutting.     

贵州省2009—2010年特大干旱灾害成因、特点及影响浅析

通过对2009—2010年贵州省特大干旱灾害灾情统计数据的分析,从本次干旱灾害成因、旱情特点、旱情缓解过程的时序变化及其对经济社会各方面的影响等进行了定量或定性的阐述。结果表明,本次干旱灾害综合了主客观两方面的原因,旱灾除了具有贵州省一般干旱灾害所具有的特点外,还呈现出持续时间更长、范围更广、旱情更重、危害更大等特点,同时表现出人饮对干旱灾害的敏感性最强的特点。从旱情、旱灾认识以及抗旱减灾对策等层面提出了意见和建议。     

Identification of processes regulating the colour and colour change in an oligotrophic,hardwater, groundwater‐fed lake,Blue Lake,Mount Gambier,South Australia

Blue Lake, located in Mount Gambier, South Australia, is the only known global example of a lake that annually changes colour in the blue end of the spectrum. A series of experiments, including Secchi depth readings, in situ spectroradiometric analysis and spectrophotometric analysis of water samples, were designed to identify the factors affecting the colour of Blue Lake and the processes that regulate these factors. Based on the results of these experiments, the processes controlling the colour and colour change in Blue Lake are described and quantified. Blue Lake colour was observed to change between AS 2700 Aqua during winter (April through to October) and Blue Bell during summer (December through to February). The colour change in Blue Lake is measurable and reflects primarily the regulation of the concentration of humic substances in the upper part of the lake by calcite precipitation. The calcite precipitation is driven by degassing of carbon dioxide from the epilimnion of the stratified lake in summer. The humic substances co‐precipitate with the calcite. Photodegradation of the humic substances may also occur.     

滃江流域“94.6”“10.5”暴雨洪水对比分析

2010年北江支流滃江遭遇1964年以来最大洪水,通过＂94.6＂＂10.5＂暴雨洪水对比,分析了滃江流域暴雨洪水的特性、演变规律及变化特点,对有效监控暴雨洪水、正确指挥防汛、提高对该地区暴雨洪水规律和形成机制的认识,对防洪减灾具有一定的参考价值。     

A 12‐month sediment and nutrient budget in a floodplain reach of the River Adour,southwest France

The sediment and nutrient budget in the floodplain reach of the River Adour in southwest France has been examined over a 1‐year period (1991–1992). Outputs of total suspended matter, dissolved inorganic nitrogen (i.e. nitrate+ammonium ions) and dissolved inorganic phosphorus (DIP) and particulate phosphorus (PP) have been compared with inputs. Alternating phases of mobilization and retention are observed for all the elements considered. Low water periods in summer allowed retention of both soluble material (24–26% for inorganic nitrogen) and suspended matter (9–19%). However, mobilization of PP associated with suspended matter transport during these periods. Elevated discharges associated with increased rainfall during the autumn period induced significant mobilization for all elements. In contrast, the winter flood event gave rise to a retention of particulate material (i.e. suspended matter and PP, 11% and 26%, respectively), but a loss of soluble materials (5% for inorganic nitrogen and 186% for DIP). The spring flood event produced retention for particulate materials (26%) while inducing losses of inorganic nitrogen (9%) and gains of DIP (7.4%). These results are related to riparian vegetation and the dynamics of nutrient cycling within the floodplain. Copyright © 2000 John Wiley & Sons, Ltd.     

Hydrogeomorphic and Biotic Drivers of Instream Wood Differ Across Sub‐basins of the Columbia River Basin,USA

Instream wood promotes habitat heterogeneity through its influence on flow hydraulics and channel geomorphology. Within the Columbia River Basin, USA, wood is vital for the creation and maintenance of habitat for threatened salmonids. However, our understanding of the relative roles of the climatic, geomorphic, and ecological processes that source wood to streams is limited, making it difficult to identify baseline predictions of instream wood and create targets for stream restoration. Here, we investigate how instream wood frequency and volume differ between seven sub‐basins of the interior Columbia River Basin and what processes shape these differences within these sub‐basins. We collected data on wood volume and frequency, discharge and stream power, and riparian and watershed forest structure for use in modelling wood volume and frequency. Using random forest models, we found that mean annual precipitation, riparian tree cover, and the individual watershed were the most important predictors of wood volume and frequency. Within sub‐basins, we used linear models, finding that some basins had unique predictors of wood. Discharge, watershed area, or precipitation often combined with forest cover, riparian conifer, and/or large tree cover in models of instream large wood volume and frequency. In many sub‐basins, models showed at least one hydrologic variable, indicative of transport competence and one ecological variable, indicative of the reach or upstream watershed's capability to grow measurable instream wood. We conclude that basin‐specific models yield important insights into the hydrologic and ecological processes that influence wood loads, creating tractable hypotheses for building predictive models of instream wood. Copyright © 2015 John Wiley & Sons, Ltd.     

Impact of Drought on Diatom Communities and the Consequences for the use of Diatom Index Values in the River Maureillas (Pyrénées‐Orientales,France)

In the context of climate change, with an increase in the incidence of seasonally dry streambeds, we examined the impact of drought, and its duration, on the structure of diatom communities and the consequences of this on diatom index values (Biological Diatom Index; Specific Polluosensitivity Index) in the Mediterranean river Maureillas. The effects of several durations of droughts or low flow events (1, 2 and 4 weeks) on diatom‐dominated biofilms were studied by removing pebbles from the river and comparing the growing communities after rewetting with those of control biofilms (pebbles left in the streambed) and with those of newly formed biofilms (cleaned‐up pebbles). Sampling was performed six times during the 28‐day rewetting phase. We determined the specific composition of diatom communities, the mortality rate after rewetting, and the Biological Diatom Index and Specific Polluosensitivity Index scores for each sample, distinguishing between potentially living diatoms (full frustules with chloroplasts) and dead diatoms (empty frustules). Our results showed a notable and durable impact of even short drought on diatom communities. The different trajectories of biofilm communities observed between the types of pebbles showed the importance of the biofilm history for the community structure. This should be taken into account to improve the sampling practices used for monitoring. We also observed a stable mortality rate whatever the drought duration was. Diatom index values were stable despite the observed impact of treatment on diatom communities. These results emphasize the reliability of the diatom index to evaluate biological quality according to European requirements. In addition, the distinction of empty and full frustules did not induce significant differences, but it may reduce biases in interpretation. Copyright © 2014 John Wiley & Sons, Ltd.     

基于耦合模型的安康库区水温水质影响研究

河流上筑坝发电将对水温、水质等生态环境产生影响。该文建立了三维水温水质耦合模型,以汉江上游安康水电站为例,选取COD(化学需氧量)和氨氮为水质指标,利用实测的水温、水质数据率定参数,对比分析单独计算和耦合计算其坝前垂向水温的差异性,模拟"引汉济渭"工程实施后逐月水温水质分布,总结耦合计算其库区水温、水质的变化规律。研究结果表明,耦合计算坝前垂向水温较单独计算反应灵敏,与库区实测水温更接近;耦合计算坝前水温在3月至9月呈弱分层状态,其余月份呈混合状态;对比不同年份的水电站下泄水温与坝址处天然水温可知,枯水年对水温影响最大,平水年次之,丰水年影响最小;坝前垂向氨氮、COD的分布规律基本与实测水温分布规律一致,受温度异重流影响,耦合计算的COD、氨氮分布规律与实际情况更相符合。     

Impact of a 100‐year flood on vegetation,benthic invertebrates,riparian fauna and large woody debris standing stock in an alpine floodplain

This paper investigates the impact of a 100‐year flood in May 1999 on community composition and large woody debris standing stock in an alpine floodplain (Isar, Germany). Detailed pre‐flood data sampled from 1993 to 1998 are compared with the situation directly after the flood. In those parts of the Isar floodplain mainly covered with pioneer vegetation prior to flooding, the coverage of unvegetated gravel bars increased by 22% following the flood. However, the flood did not remove larger amounts of older successional vegetation stages (willow thickets, floodplain forest). No significant changes in the benthic invertebrate fauna were recorded. The lowest densities of riparian ground beetles (Carabidae) within the study were recorded one month after the flood. Two months later, the ground beetle densities increased to the highest values ever recorded, indicating the ground beetle's high potential for recolonization. These results highlight the degree of resilience of both the aquatic and the riparian invertebrate fauna. The flood also caused a significant increase in large woody debris standing stock; in one section the number of logs increased tenfold and the volume increased by a factor of 20, leading to the assumption that most woody debris in alluvial flood‐plains is provided by catastrophic events. Copyright © 2004 John Wiley & Sons, Ltd.     

The spatial and temporal distribution of metals in an urban stream: A case study of the Don River in Toronto,Canada

Widespread growth of cities, the association of trace metals with urban runoff, and the potentially deleterious effect of metals on aquatic ecology have made it important to understand the distribution and transport of metals through surface water channel networks. The Don River in Toronto, Canada has been identified as an Area of Concern for pollution to Lake Ontario, with historically high levels of metal contamination. Sampling programs are sparse, therefore a model is needed to understand the spatial and temporal variability of metals in the river network. The objectives of the current study are to: i) describe the sampled spatial and temporal variability of metals in the Don River and ii) develop a modelling strategy to describe within flood metal transport dynamics. A model setup tool is developed that links Storm Water Management Model (SWMM) with the Environmental Fluid Dynamics Code (EFDC) to allow a seamless transition from catchment hydrology to in-stream hydraulic and chemical processes. Results show that lead pollution in the Don River is decreasing, likely as a result of policy changes and sediment dredging in the mouth of the river. However, zinc and copper pollution are increasingly problematic, with copper exceeding recommended lower guidelines, particularly during floods. Model results confirm that most of the sediment and metals are transported in relatively short bursts within longer flood durations and are stored in depositional hotspots within the Lower Don River. A better monitoring strategy is needed to understand and more accurately parametrize these processes in an urban river system.     

气候变化和人类活动对滦河下游地区水资源变化影响分析

通过对滦河下游地区气温、降水、地表水资源量、水资源总量、地下水水位等系列的变化分析,认为降水变化是造成滦河流域下游水资源年际波动性变化的主要因素,但造成流域水资源量显著下降的主要影响因素是人类活动的影响,包括以农业灌溉为主的水资源利用、土地利用活动对流域水资源的间接影响,以及向外流域持续调水等因素的直接影响。     

Multi‐scale modelling of land‐use change and river training effects on floods in the Rhine basin

Land‐use changes effects on floods are investigated by a multi‐scale modelling study, where runoff generation in catchments of different sizes, different land uses and morphological characteristics are simulated in a nested manner. The macro‐scale covers the Rhine basin (excluding the alpine part), the upper meso‐scale covers various tributaries of the Rhine and three lower meso‐scale study areas (100–500 km²) represent different characteristic land‐use patterns. The main innovation is the combination of models at different scales and at different levels of process representation in order to account for the complexity of land‐use change impacts for a large river basin. The results showed that the influence of land‐use on storm runoff generation is stronger for convective storm events with high precipitation intensities than for long advective storms with low intensities. The simulated flood increase at the lower meso‐scale for a scenario of rather strong urbanization is in the order of 0 and 4% for advective rainfall events, and 10–30% for convective rain storms with a return period of 2–10 years. Convective storm events, however, are of hardly any relevance for the formation of floods in the large river basins of Central Europe, because the extent of convective rainstorms is restricted to local occurrence. Due to the dominance of advective precipitation for macro‐scale flooding, limited water retention capacity of antecedent wet soils and superposition of flood waves from different tributaries, the land‐use change effects at the macro‐scale are even smaller, for example at Cologne (catchment area 100 000 km²), land‐use change effects may result in not more than 1–5 cm water level of the Rhine. Water retention measures in polders along the Upper and Lower Rhine yield flood peak attenuation along the Rhine all the way down to the Dutch border between 1 and 15 cm. Copyright © 2007 John Wiley & Sons, Ltd.