Evaluating the Effects of Culvert Designs on Ecosystem Processes in Northern Wisconsin Streams

Culvert replacements are commonly undertaken to restore aquatic organism passage and stream hydrologic and geomorphic conditions, but their effects on ecosystem processes are rarely quantified. The objective of this study was to investigate the effects of two culvert replacement designs on stream ecosystem processes. The stream simulation design, where culverts accommodate bankfull width and streambeds are reconstructed through the culvert, was compared with the bankfull and backwater design, where streambeds were left to fill naturally, as well as to non‐replaced culverts. We predicted that stream simulation culverts would best preserve water velocity and coarse particulate organic matter (CPOM) retention within the culvert relative to upstream reaches, and that both replaced culvert styles would exhibit rates closer to upstream reaches than non‐replaced culverts. In addition, we predicted that ecosystem processes (CPOM retention, transient storage and nutrient uptake) would be similar in reaches upstream and downstream of both replaced culvert styles, because both designs are constructed to maintain stream slopes and bankfull widths through the structure. We found that stream simulation design better maintained CPOM retention through culverts compared with non‐replaced and bankfull and backwater design culverts, but observed no differences in ecosystem processes between reaches located upstream or downstream of replaced culverts. Although the stream simulation design requires additional streambed construction relative to the bankfull and backwater design, this step may lead to additional improvement if maintaining ecological conditions through the culvert is an important restoration goal. Copyright © 2017 John Wiley & Sons, Ltd.     

Responses of macroinvertebrate communities to river restoration in a channelized segment of the Shibetsu River,Northern Japan

The effects of restoration of channel meandering and of groyne structures on physical variables and river‐dwelling macroinvertebrates were examined in a lowland river, the Shibetsu River in Northern Japan. The lowland segment of the Shibetsu River, which previously meandered, was straightened by channelization and groynes installed on some portions of the channelized reach. In 2002, the channelization works were partly reversed to improve the degraded river ecosystem. Physical environment variables and macroinvertebrate community structure and composition were compared among reconstructed meanders and channelized reaches with and without groynes. The shear stress of the river edge in reconstructed meanders and groyne reaches was lower than that in a channelized reach. In addition, the edge habitat near the stream bank created by the reconstructed meander and groyne reaches had higher total density and taxon richness of macroinvertebrates than those of the channelized reach. Restoration provided a relatively stable edge habitat, contributing to the recovery of macroinvertebrate communities in such channelized lowland rivers. The placement of groynes can be an effective method of in‐stream habitat restoration for macroinvertebrates. Copyright © 2006 John Wiley & Sons, Ltd.     

Vertical distribution of coarse particulate organic matter in river bed sediments (Morava river,Czech Republic)

The vertical and temporal distribution of coarse particulate organic matter (CPOM) larger than 1 mm from 0 to 70 cm depth within the substrate was observed at two different sites along a riffle in the River Morava. Samples of hyporheal sediments were taken by inserting a steel cylinder and a special grab. The amount of CPOM was determined by combustion. The maximum amount of CPOM was found at a depth of 30-40 cm; lower levels of CPOM were observed in deeper horizons. The average amount of CPOM in 10cm layers (volume 1582.9 cm³) was 232.2 gm^?3 at station A and 691.3 gm^?3 at station B. The content of CPOM showed a maximum during the summer.     

The distribution and management of channelized streams in Denmark

The Danish Watercourse Law of 1982 states that major river works and maintenance procedures must be planned and undertaken with regard to water quality and the physical form of the river channel. Fluvial geomorphology is an essential component of alternative procedures of river management which work with nature rather than against it. A survey of Danish stream channels has been produced by collating data obtained from maps, field surveys and engineering documents. This indicates that 97.8 per cent of Danish watercourses have been artificially straightened and that only 2.2 per cent (880 km) have natural morphological characteristics. The density of channel works is 300 times greater than in the U.S.A. and 15 times greater than in England and Wales. It is suggested that since there are only a few naturally sinuous channels in Denmark these should be given special consideration with regard to stream management practices. Measurements undertaken at approximately 300 sites in Denmark indicate five major processes of adjustment within straightened reaches. These adjustments include degradation of the channel bed with associated bank slumping, armouring of the bed, the development of a sinuous thalweg by the deposition of sediment at low gradients, and restoration of meanders. Channel stability is related to specific stream power and the results may be useful in predicting potential adjustments following channel straightening. Deposition in natural reaches below straightened channels often obliterates pool and riffle sequences but several channel adjustments may provide a greater variability of physical habitats than the initial uniform straightened channel; their significance for the biology of the watercourse is best considered before traditional management practices are carried out to control the adjustment.     

芦苇占优势农田溪流营养盐滞留能力分析与评估

2014年9月—2015年4月,在合肥地区二十埠河流域的某一典型农田源头溪流段,选择以Na Cl为保守示踪剂,NH4Cl和KH2PO4为添加营养盐,采用恒速连续投加的方式,开展了7次野外现场示踪试验。在此基础上,利用OTIS模型和营养螺旋原理,从机制层面分析和评估芦苇占优势农田源头溪流氮磷营养盐滞留能力和滞留特征。结果表明,该芦苇占优势渠段的比值As/A明显超过一般源头溪流水体,暂态存储对于营养盐滞留有较大影响;NH4+和SRP的暂态存储区营养盐一阶吸收系数都较主流区高一个数量级,且所有吸收系数均为正值,表明芦苇占优势渠段具有氮、磷"汇"的功能;NH4+吸收长度明显低于SRP,特别是冬季和初春,意味着溪流对于NH4+的滞留能力超过SRP;NH4+和SRP的总滞留率分别为14.46%和10.73%,生物滞留率平均值分别为9.17%和3.67%;主流区流动水体和暂态存储区对于NH4+滞留的平均贡献率分别为43.12%、56.88%;对于SRP滞留的平均贡献率分别50.13%、49.87%。     

Land‐use effects on water quality of a first‐order stream in the Ozark Highlands,mid‐southern United States

Urban and agricultural land uses can alter the natural hydrologic conditions of streams and rivers and often degrade water quality. In the Ozark Highlands of the mid‐southern United States, the climate, topography, soil properties, karst limestone geology, agricultural practices and rapid urbanization make water quality of particular concern due to the increased potential for water quality degradation by contaminant leaching to groundwater and runoff to surface waters. The objective of this study was to evaluate the effects of season (i.e. dry/cool and wet/warm) and riparian land use (i.e. urban, grazed pasture, ungrazed pasture, wetland, cultivated agriculture and grassland) on surface water quality in a first‐order stream within a diverse agricultural watershed in the Ozark Highlands. Water samples were collected twice a month within each land use during base‐flow conditions from October 2006 through October 2007. Samples were also collected periodically during storm‐flow conditions from October 2006 through December 2007. The greatest in‐stream pH was adjacent to the grazed pasture. In‐stream NO₃‐N concentrations were greatest adjacent to the cultivated agriculture and grassland during the dry/cool season (i.e. October 2006 to March 2007) and averaged 2.67 mg L^?1. In‐stream soluble reactive P (SRP) concentrations were greatest adjacent to the grassland during the wet/warm season (i.e. April 2007 to October 2007) and averaged 0.81 mg L^?1. Concentrations of SRP, K, Mg and Zn were greater during storm‐ than base‐flow conditions and in‐stream As concentrations frequently exceeded 0.01 mg L^?1. Discharge and in‐stream NH₄‐N concentrations were unaffected by land use or season and averaged 0.003 m³ s^?1 and 0.10 mg L^?1, respectively, across all land uses and seasons. Results of this study clearly demonstrate the significant effect of adjacent land use on in‐stream water quality of a first‐order stream in a diverse agricultural watershed and highlight the importance of managing upstream land use in order to regulate downstream water quality. Copyright © 2010 John Wiley & Sons, Ltd.     

保山北庙水库集水区5种森林类型枯落物持水特性研究

利用样方调查法、烘干法、浸泡法分析了云南省保山市北庙水库集水区纯云南松、纯人工桉树林、混交林Ⅰ(云南松+桉树混交林)、混交林Ⅱ(云南松+华山松+杉木+青冈栎混交林)和纯华山松5种森林类型枯落物的持水能力。结果表明:5种森林类型枯落物蓄积量都较小,最大为7.27 t/hm²,最小为4.51 t/hm²;枯落物未分解层和半分解层持水量随着浸泡时间增加,在8 h时平均持水量分别为5.22,5.83 t/hm²,24 h时分别为5.69,6.26 t/hm²;吸水速率随着浸泡时间减少,在8 h时平均吸水速率分别为0.65,0.73 mm/h,到24 h时分别为0.24,0.26 mm/h,且均是半分解层＞未分解层;纯华山松和混交林Ⅱ 2种森林类型枯落物持水性能优于其他3种森林类型。研究结果可为水源区植被恢复、选择最佳树种、合理配植森林类型、森林涵养水源提供科学依据。     

桉树人工林对林区水库黑水的影响

以桉树人工林区水库———南宁市天雹水库周边种植的桉树、马尾松两种主要树种为研究对象,分别对比其凋落叶在蒸馏水、水库表层水样、水库底层水样浸泡下的水质特征,并结合2018年春(3月)、夏(7月)、秋(11月)、冬(12月)4个季节对水库近桉树林与马尾松林径流入库区水质情况,分析桉树凋落叶对林区水库黑水的影响。结果表明:桉树浸泡液呈现黄棕色甚至黑褐色,色度显著大于马尾松浸泡液,其单宁酸与溶解性有机碳(DOC)质量浓度分别达到1.14 mg/L和46.40 mg/L,均较马尾松高,水体色度与DOC、单宁酸均呈显著正相关关系,相关系数分别为0.83和0.94;近桉树林区库区的水体的有机质和Mn质量浓度也高于近马尾松林区库区;桉树凋落叶与缺氧的水库底层水体混合后,Fe、Mn质量浓度升高,分别达到1.21 mg/L和2.09 mg/L。     

Mesoscale river restoration enhances the diversity of floodplain vegetation

Effective river restoration aims for the recovery of ecosystem functions by restoring processes and connectivity to the floodplain. At the straightened lowland river Stör in northern Germany, a sequence of 15 new meanders was created in 2008, with wavelengths up to 70 m. The newly created areas within the meander bends range in size from 215 to 1,115 m² and function as a series of 15 restored floodplain sites, which are subject to succession. After 7 years of restoration measures, we investigated the vegetation dynamics on the (a) restored floodplains and compared them with adjacent floodplain sites that were used as (b) low‐intensity grazed grassland or as (c) abandoned grassland. We analysed the species diversity, functional vegetation parameters, and plant communities of 200 plots within the floodplain area of the three floodplain types and of 246 plots at their river banks. Plant species diversity and composition differed with respect to restoration measure and site management. Restored floodplains revealed a higher coverage in species of wet grasslands and softwood forests and higher species diversity than abandoned grasslands. Grazed grasslands showed the highest species number and coverages of pioneer vegetation. The banks indicated fewer differences in species composition between floodplain types. The construction of restored floodplains revealed greater overall plant diversity due to promoting the development of typical floodplain vegetation. Shallow meanders with increased flooding intensity and the creation of a varying microreliefs are recommended as combined river/floodplain measures in order to foster processes and connectivity between valley components.     

多级拦水堰坝调控农田溪流营养盐滞留能力的仿真模拟

为揭示多级拦水堰坝对于低等级小河流营养盐滞留能力的影响,以巢湖流域某一典型的农田源头溪流为对象,在野外示踪实验和计算机模拟的基础上,针对构建的多级简易水坝,采用暂态存储和营养螺旋指标,仿真模拟多级拦水堰坝对于氮磷营养盐滞留能力的调控效果。结果表明:多级拦水堰坝Darcy-Weisbach阻力系数明显超过无堰坝情形,但其弗劳德数Fr和雷诺数Re则较无堰坝情景低些;多级拦水堰坝相应的交换长度Ls值较无堰坝情景低1~2个数量级,水力持留因子Rh则较无堰坝情景明显增大,表明多级拦水堰坝使溪流的暂态存储能力得到很大提升;在多级拦水堰坝情景下,NH4+和PO43-的吸收长度Sw均有大幅度的下降,其中NH4+削减幅度达70.27%~89.47%,PO43-为75.59%~81.92%;不仅如此,在多级堰坝情景下,NH4+和PO43-的物质传输系数Vf、吸收速率U均显著增大,表明多级拦水堰坝可以有效提高农田溪流氮磷营养盐的滞留潜力。     

Role of the floodplain and riparian zone in suspended matter and nitrogen retention in the adour river,south-west France

The retention capacity of the floodplain and riparian zone for suspended matter and nitrogen has been investigated in the Adour River, a seventh order stream in south-west France. Suspended matter and nitrogen fluxes through a 25 km meandering stretch of the river were measured during two flood events and compared with the amount of sediment trapped in the riparian zone (1.1 km²) and the major floodplain (16.8 km²) of the studied area. It was estimated that the floodplain and the riparian zone together retained between 10 and 20% of the suspended matter entering the stretch under study during the two main floods (138 700 Mg). Moreover, they retained about 11% of the total particulate nitrogen fluxes (640 Mg). Although the riparian zones are 15 times smaller than the major floodplain, the total suspended matter and particulate nitrogen deposition were, 50 and 17 times, respectively, larger in the riparian zone. The results obtained on the Adour River floodplain show that large river systems should not be considered only as export systems as riparian zones can retain a significant amount of suspended organic and mineral matter during floods.     

Use of a flow deflector to protect rheophilic fish spawning grounds during hydropeaking

Rheophilic fishes are one of the ecological groups of fishes declining most quickly in number due to various habitat modifications and discharge regulations. Artificial rapid increases and decreases in discharge (hydropeaking) can cause severe damage to the eggs of rheophilic fishes. We investigated whether the effects of a water increase in hydropeaking on a spawning ground may be mitigated by a deflector installed at the top of the weir that diverts flow to other sections. At the research site, rheophilic asp (Leuciscus aspius) spawn annually in early spring, and their success might be affected by hydropeaking, with base discharge ranging from 3 to 7 m³ × s⁻¹ and peak discharge ranging from 16 to 25 m³ × s⁻¹ occurring 4 to 7 times during the asp spawning season and egg development period. To protect the adhesive eggs from detachment during peak discharge, a flow deflector (a wooden wall at the selected part of the weir) was installed to regulate discharge on the protected spawning ground. This measure allowed normal discharge under base flow conditions. During peak flow, a significant portion of the additional water was directed to the part of the river channel where egg abundance was lower and to the mill channel, where asp spawning was not present. While the total discharge increased 4.1 times compared to the base flow, the water discharge in the protected spawning ground increased only 2.7 times. This resulted in more than half of the asp eggs being retained in the protected channel. Although the use of such a measure is limited to specific local conditions where eggs are located just downstream of the weir, it can be a valid solution in highly fragmented rivers with hydropeaking and can lead to higher recruitment of rheophilic fishes.     

Modelling Temperature,Body Size,Prey Density,and Stream Gradient Impacts on Longitudinal Patterns of Potential Production of Drift‐Feeding Trout

In this study, we modelled idealized stream reaches using empirical hydrodynamic and bioenergetic parameters to predict how rainbow trout production depends on physical and biological variations across a downstream gradient, and we compared these downstream effects in a low and high‐gradient stream reach. We found that longitudinal production potential (i.e. net rate of energetic intake per 100 m of stream length) generally increased with increasing stream size when stream gradient was low. This was not the case, however, for high‐gradient streams, wherein maximum longitudinal production potential was associated with middle or low stream size (Q_MAD = 2.5 to 25 m³ s^?1). Areal production potential (net rate of energetic intake per m² of wetted stream bed) reached a maximum at low stream size (Q_MAD = 2.5 m³ s^?1) with both high and low gradients. We also showed that high stream temperature and low drift density could potentially cause adult rainbow trout to be excluded from stream reaches with high flow. The models presented here have a stronger mechanistic basis for predicting fish production across heterogeneous stream environments and provide more nuanced predictions in response to variation in environmental features than their physical habitat‐based predecessors. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of rainfall and beaver dams on upstream movement of spawning Atlantic salmon in a restored brook in Nova scotia,Canada

In a restored, third‐order stream in northern Nova Scotia, Canada, we used redd counts over 12 years to examine the influence of beaver dams and the timing and intensity of autumn rains on spawning activity of Atlantic salmon. Most beaver dams in most years had no detectable effect on the distribution of spawning redds, but in 2004 the density of redds downstream from a three‐dam complex was significantly greater than that above, suggesting the dams were a barrier to many fish. A second complex of dams blocked salmon passage completely in 2003 and 2004 until they were notched to provide access upstream. The length of stream used by salmon for spawning was linearly correlated with total precipitation in the basin in October plus November (R² = 0.60), to a ceiling of 325 mm, above which the fish had access to the entire brook, if beaver dams were notched. Number of redds in the whole brook was strongly correlated (R² = 0.94) with the coefficient of variation (CV) of daily rainfall in October, but only for 7 of 11 years. This relationship disappeared when the impassable beaver dam complex failed in 2005, allowing salmon free access to 4 km of the upper brook. Variation in rainfall, and hence discharge, in this flashy brook evidently influences migration and spawning of Atlantic salmon in conjunction with channel blocking by beaver dams. Copyright © 2009 John Wiley & Sons, Ltd.     

Lithological controls influence river form in contrasting sub-catchments: The Scamander and Avenue Rivers,Tasmania

Bedrock influence on river channel form is difficult to assess, with many catchments dominated by glacial erosion and with blanketing sediments from both pluvial and fluvial sources. The Scamander catchment in Tasmania lacks glacial history and features two bedrock-confined sub-catchments of similar area and maximum flow length, but one dominated by Mathinna Group sedimentary rocks, and the other with large areas in granite lithology. Lithology types, stream network parameters and near stream slope angles were analysed using geographical information systems, and results of stream cross sections, channel form and planforms were compared for each lithology. Results showed that granite features low gradient, shallow streams with channel slope cross sections of <10°. Granite channels are irregular and dominated by large boulders that create channel roughness and resist incision. Weathering products of coarse quartz sand provide anchorages for in-channel vegetation. By contrast, sedimentary Mathinna Group rocks feature steeply incised trough-like channels, with near-channel hillslope gradients mostly between 30° and 50°. Rectangular blocks disintegrate to gravel cobbles on the channel bed, providing poor anchorage for vegetation. Mathinna lithology influences steep, low roughness channels, and stable, incised recurved meanders formed by river interaction with vertical layers of resistant rock. The resistant bedrock lithology is demonstrated in this study to influence varied river planforms, near-channel slope gradients, channel sediments and cross sections.     

Structural and functional changes of tropical riffle macroinvertebrate communities associated with stream flow withdrawal

Tropical island streams worldwide are threatened by existing or proposed dams and diversions that remove freshwater for human use; yet, there have been few studies that address the effects on aquatic communities. The objective of this study was to quantify changes in tropical macroinvertebrate communities associated with stream flow withdrawal. Benthic macroinvertebrates were collected from riffle habitats located above and below a stream diversion on Maui, Hawaii, from June to August 2000. Native and introduced taxa were identified from both locations. The most dominant taxon was midges (Diptera: Chironomidae) followed by two introduced caddisflies, Cheumatopsyche analis (Banks) (Trichoptera: Hydropsychidae) and Hydroptila potosina (Buenoa‐Soria) (Trichoptera: Hydroptilidae). A native shrimp, Atyoida bisulcata, and beach fly, Procanace sp. (Diptera: Canacidae), were either eliminated from or significantly reduced below the diversion. Mean total macroinvertebrate densities were greater above (13 357 individuals/m²) the diversion compared to below (10 360 individuals/m²). Mean total macroinvertebrate biomass was significantly reduced by 60 per cent below the diversion, but specific taxa did not show this effect. These results suggest that diverted stream flow limited macroinvertebrate colonization and growth, expressed as reduced community density and biomass, which may alter the structure and function of other trophic levels within tropical stream food webs. Copyright © 2008 John Wiley & Sons, Ltd.     

The importance of streamlining in influencing fish community structure in channelized and unchannelized reaches of a prairie stream

Channelized and unchannelized sections of a prairie stream in northwestern Iowa were compared to determine how differences in microhabitats affected fish species abundance and diversity and the incidence of streamlined species. Channelized sections had significantly more fish per unit area (P < 0.05) but significantly less biomass (P < 0·05). Green sunfish (Lepomis cyanellus) and stonecats (Noturus flavus) were common in the unchannelized sections but rare or absent in the channelized ones. Small native minnows (Cyprinidae), especially the bigmouth shiner (Notropis dorsalis), dominated channelized sections. Species diversity was lower in channelized sections, but differences were not statistically significant (P = 0·06). Family diversity was significantly lower in channelized sections (P < 0·05). Channelized sections exhibited less heterogeneity of widths, velocities and substrates and contained more stremlined forms than did unchannelized sections. Unchannelized sections, characterised by greater diversity of velocities and substrate types, supported more centrarchids and ictalurids, fishes that are not optimally streamlined. Although many other factors besides streamlining influence the fish community structure in streams, in reaches without refuges from the current, streamlining may be a factor determining which species persist there.     

基于雪岭云杉树轮的阿克苏河干流冬季径流重建

基于阿克苏河上游高山区采集的雪岭云杉树轮样芯构建了雪岭云杉树轮宽度年表,结合阿克苏河干流径流数据解析了雪岭云杉长期生长与阿克苏河干流径流关系,并重建了阿克苏河干流1813—2015年冬季径流序列。结果表明:利用雪岭云杉树轮宽度年表重建的阿克苏河干流1813—2015年冬季径流序列模拟值与实测值吻合度较高,重建径流序列稳定可靠;1813—2015年阿克苏河干流冬季多年平均流量为82.19 m~3/s,共出现5次持续丰水期和3次持续枯水期,最长的枯水段持续17年(1943—1959年);阿克苏河干流冬季径流变化存在51 a、29 a、16 a周期,第一主周期为51 a。     

The introduction of woody debris into a channelized stream: effect on trout populations and habitat

Large woody debris was explored as a method of restructuring channelized streams to improve salmonid habitat. Whole trees were inserted in sections along a 2 km reach of a channelized stream to determine if large woody debris: (1) increased the abundance and biomass of brown (Salmo trutta) and rainbow trout (Oncorhynchus mykiss); (2) had an effect on physical habitat features; and (3) provided trouts with additional habitat. Trout populations and stream morphology were monitored before and after the introduction of woody debris and compared to control sections lacking woody debris. Abundance and biomass of both brown and rainbow trout increased in the treatment section compared to the control. Maximum and standard deviation of fish total length increased in all sections during summer months. The number of individuals and the standard deviations of total lengths decreased in the control section in winter, but increased in the treatment section. Mean water velocities decreased and number and volume of pools increased in treatment sections. Brown and rainbow trouts sought woody debris structures for cover. We conclude that large woody debris can serve as a method of reconstructing channelized streams to improve salmonid habitat. Copyright © 2002 John Wiley & Sons, Ltd.     

Cascade Dam-Induced Hydrological Disturbance and Environmental Impact in the Upper Stream of the Yellow River

The construction of a dam converts the natural streamflow to human control. It is necessary to learn the accumulated effect of cascade dams on hydrological characteristics, sediment and nutrient pollution discharge. The current research describes the analysis and simulation of streamflow, sand concentration and nutrient pollutant discharge alterations caused by the construction of a cascade of eight dams along the Longliu section of the upper stream of the Yellow River. The analysis shows that the maximum monthly streamflow difference between the inlet and outlet of the Longliu section decreased from 430 to 115 m³/s, after the appearance of the cascade dams between 1977 and 2006. In the same period, the correlation coefficient (R ²) of monthly streamflow between the inlet and outlet of Longliu dropped from 0.959 to 0.375. The peak of streamflow shifted from June to May and October. The difference in sand concentration between two sections decreased from 0.52 to 0.39 kg/m³, which was the direct consequence of the operation of the reservoirs. The R ² value of sand concentrations of the inlet and outlet were also reduced from 0.504 to 0.356. A t-test analysis indicates that the original hydrological nature was significantly disturbed by the cascade dams. The influence of the dams on nutrient pollutant transport was simulated by the SWAT model. This simulation suggests that the cascade dams decreased the discharge of total nitrogen and total phosphorus from 15.4 × 10³ t and 1,996 t to 0.4 × 10³ t and 328 t, respectively. In conclusion, the accumulated impact of cascade dams on streamflow, sand concentration and nutrient pollutant discharge were analyzed, which were helpful for understanding the environmental features of the entire watershed.