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1.
D. J. Booker 《水文研究》2003,17(3):577-599
In urban rivers, flow regime and channel morphology are the drivers of physical habitat quality for aquatic species. Peak discharges are increased at high flows as a result of impermeable catchments and channel engineering for flood protection schemes. Hazardous conditions and flashy hydrographs mean that measurement of velocities at high flows is a difficult task. This research uses a three‐dimensional computational fluid dynamics (3D‐CFD) model to simulate hydraulic patterns in two urban river channels. A 3D‐CFD code, called SSIIM, was used to simulate hydraulic conditions in two engineered river reaches of the River Tame, Birmingham, UK. These two sites represent channels with different levels of engineering. Models were calibrated and tested using field measurements. Results show that modelled water surface levels and velocity profiles are well simulated. Calibrated roughness heights are compared with those derived from field measurement of sediment size. Numerical experiments are used to assess the relationship between grid resolution in the vertical dimension and the form of the modelled velocity profiles. Biologists have used laboratory experiments to determine maximum sustainable swimming speeds (MSSS) of fish, often in order to assess what level of a particular pollutant may be tolerable. In this work, simulations of high‐flow hydraulic patterns are used to compare velocity patterns with fish MSSS. Results show that when the water levels rise to fill the first channel of the two‐stage channels at the sites, which occurred 16 times in 2000, MSSS are surpassed in the majority of available habitat, suggesting that excessive velocities at high flows are one factor that limits fish habitat. A comparison between the two reaches shows that there is less available habitat in the more modified reach. Conclusions suggest that an approach that integrates water quality issues and physical channel characteristics must be taken in river rehabilitation schemes, as improvements to water quality alone may not be sufficient to improve habitat quality to the desired level. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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3.
David A. Reid Marwan A. Hassan Stephen Bird Robin Pike Peter Tschaplinski 《地球表面变化过程与地形》2020,45(2):295-311
Stream channel morphology forms the template upon which hydraulic aspects of aquatic habitat are created, yet spatial and temporal variability in habitat imposed by changing morphology is not well understood. This paper presents a conceptual model linking sediment supply patterns to spatial and temporal variability in channel form and aquatic habitat. To evaluate this model, change over time in three habitat variables is quantified using a 2D hydrodynamic modeling approach. A 45-year record of topographic data from Carnation Creek, a catchment in coastal British Columbia, is used for the flow modeling. Using the Nays2DH modeling platform, water depths and velocities are simulated in eight channel segments located at different positions relative to locations of historical colluvial input using seven flow levels ranging from 3% to 400% of mean annual discharge (0.02 to 3.31 m s ). Results indicate that habitat availability changes through time as a result of sediment supply-driven changes to channel morphology and wood loads, but patterns in habitat vary as a function of dominant channel segment morphology. Spatial and temporal variability in morphology also influences the relationship between habitat availability and river discharge, leading to non-stationary habitat-discharge rating curves. When habitat areas are predicted by applying these curves to daily flow series spanning annual dry seasons, over 50% of the variance in cumulative seasonal habitat area can be explained by year-to-year changes in channel morphology and wood loading, indicating that changing morphology is an important factor for driving temporal habitat variability. This variance is related to the morphological variability of a channel segment, which in turn is associated with the segment position relative to zones of colluvial input. Collectively, these results suggest that variability in habitat is impacted by channel morphology, and can be evaluated partly on the basis of a channel's sediment supply regime. © 2019 John Wiley & Sons, Ltd. 相似文献
4.
Environmental flow (e-flow) assessment is essential for the ecological protection and restoration of lake-marsh systems. Previous studies on e-flow assessment for lake-marsh systems focused on lake-marsh systems with natural seasonal hydrological patterns (i.e., low water level in winter and high water level in summer). However, they have not considered lake-marsh systems with reverse seasonal hydrological patterns (i.e., high water level in winter and low water level in summer). The reverse seasonal hydrological patterns impose seriously negative impacts on waterbirds, because the hydrological patterns could lead to limited plant germination in spring and massive plant death in summer, leaving few plants available as food for waterbirds in winter, and could consequently reduce the sheltering and forageable areas for waterbirds. This study took Hongze Lake Wetland National Nature Reserve in China as the study area. Based on the habitat requirements of waterbirds, the sheltering and forageable areas for waterbirds under different water-depth and aquatic plant distribution scenarios were calculated. By exploring the impacts of reverse seasonal hydrological processes on waterbird habitats, we determined the necessary e-flows for lake-marsh systems with reverse seasonal hydrological patterns to meet the needs of waterbird habitat. The results showed that the water level of Hongze Lake should be controlled to 13.0–13.1 m in March, 12.5–12.6 m in July, and 12.9–13.0 m in October, which can meet the needs of waterbirds for both shelter and foraging. 相似文献
5.
为了解南水北调中线干渠浮游植物群落的时空格局,自2018年8月开始分4个季度对干渠沿程的11个样点进行采样调查,同步开展水环境调查;共检出浮游植物7门83属145种,物种丰富度上,硅藻种类数最多,绿藻和蓝藻分别占第2和第3位,且春季>秋季>冬季>夏季;优势种包括极小曲丝藻(Achnanthidum minutissimum)、桥弯藻(Cymbella sp.)、空星藻(Coelastrum sphaericum)、衣藻(Chlamydomonas sp.)等(优势度Y>0.02);全年叶绿素a浓度为(4.09±2.89)μg/L,细胞密度为(6.79±7.15)×106cells/L,夏季细胞密度显著高于其他季节,以绿藻、蓝藻为主,其他季节以硅藻、绿藻为主;空间上,细胞密度从南到北呈递增趋势,穿黄工程后显著高于穿黄工程前;RDA与多元线性回归分析显示:水温和营养盐是影响群落结构的关键因素,其次是流量和流速,这些因子成为群落时空格局的决定因子;NMDS与聚类分析显示:时间变化对于群落结构产生的影响比空间变化更为显著.本研究确认了跨流域长距离输水的中线干渠中浮游植物群落的显著时空异质性;鉴于流速、流量对群落的决定作用,建议在输水管理中加强生态调度技术研究,以调控浮游植物群落,保障水质稳定. 相似文献
6.
纳木错水温变化及热力学分层特征初步研究 总被引：3，自引：3，他引：0
水温变化是湖泊的重要物理特性,对湖泊的水质特征、湖水能量循环、水生生态系统研究具有重要意义.基于不同季节的实地观测资料,分析青藏高原高海拔、深水大湖纳木错的水温变化特征及季节差异,并着重分析湖水热力学分层的季节变化.结果显示纳木错中部、东部两个湖盆冬季封冻,夏季存在稳定分层,春、秋季混合,是一个典型双季对流、完全混合型湖泊.但两个湖盆水温变化与热力学分层又有各自的特征,东部浅湖盆湖水在春季升温快,夏季分层与秋季翻转均比中部湖盆早,且秋季翻转时水温也比中部湖盆高.初步分析认为两个湖盆不同的湖盆形状及水深分布可能是造成其热力学特征差异的主要原因. 相似文献
7.
In this research we evaluate the effects of the method used for estimating the potential surface available for benthic macroinvertebrates in macrophyte and unvegetated habitats on several metrics and habitat preference of aquatic macroinvertebrates in the upper catchment of the Henares River (Guadalajara, Central Spain). Three sampling sites were selected: a well-preserved stream (site A), a stream with no wood riparian vegetation (site B), and a straightened and deforested reach (site C). Two habitats were selected in each site: unvegetated habitat (i.e., substrata without macrophytes) and macrophyte habitat (i.e., substrata covered by macrophytes). In each habitat, six macroinvertebrate samples (including all macrophytes or mineral particles) were collected using a Hess sampler. Diversity and density of major families were referred to the surface of the Hess sampler (=Hess surface method) and to the actual surface of either mineral particles or macrophytes (=actual surface method). In general, for the actual surface method, biomass, richness, dominance, and diversity metrics were higher in the mineral habitat than in the macrophyte habitat. This trend was different for the Hess surface method. In general, densities turned out to be higher in the unvegetated habitat than in the macrophyte habitat when using the actual surface method, but the reverse occurred when using the Hess surface method. This fact is relevant for river biomonitoring, especially when reaches with different dominant substrates (macrophytes vs mineral) are compared using just one of the methods. It is concluded that the macrobenthic metrics and density values are influenced by the method used to estimate the potential available surface for aquatic macroinvertebrates. 相似文献
8.
Krista L. Jones Geoffrey C. Poole William W. Woessner Matt V. Vitale Brian R. Boer Scott J. O'Daniel Steven A. Thomas Brook A. Geffen 《水文研究》2008,22(13):2105-2113
Across 1·7 km2 of the Umatilla River floodplain (Oregon, USA), we investigated the influences of an ephemeral tributary and perennial ‘spring channel’ (fed only by upwelling groundwater) on hyporheic hydrology. We derived maps of winter and summer water‐table elevations from data collected at 46 monitoring wells and 19 stage gauges and used resulting maps to infer groundwater flow direction. Groundwater flow direction varied seasonally across the floodplain and was influenced by main channel stage, flooding, the tributary creek, and the location and direction of hyporheic exchange in the spring channel. Hyporheic exchange in the spring channel was evaluated with a geochemical mixing model, which confirmed patterns of floodplain groundwater movement inferred from water‐table maps and showed that the spring channel was fed predominantly by hyporheic water from the floodplain aquifer (87% during winter, 80% during summer), with its remaining flow supplied by upslope groundwater from the adjacent catchment aquifer. Summertime growth of aquatic macrophytes in the spring channel also influenced patterns of hyporheic exchange and groundwater flow direction in the alluvial aquifer by increasing flow resistance in the spring channel, locally raising surface water stage and adjacent water‐table elevation, and thereby altering the slope of the water‐table in the hyporheic zone. The Umatilla River floodplain is larger than most sites where hyporheic hydrology has been investigated in detail. Yet, our results corroborate other research that has identified off‐channel geomorphic features as important drivers of hyporheic hydrology, including previously published modeling efforts from a similar river and field observations from smaller streams. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
9.
《Limnologica》2021
Ecological restoration of eutrophic lakes using aquatic macrophytes is an important and practical technology. Here, we investigated the response of phytoplankton and zooplankton to a large-scale 2015-built aquatic macrophyte enclosure (AME, 200,000 m2) screened of by a PVC net in Baima Lake, a eutrophic lake, from spring to autumn of 2019. AME significantly improved water quality by increasing water transparency, and reducing total nitrogen, total phosphorus, and chlorophyll-a content during the growing season. AME significantly decreased phytoplankton abundance and biomass and marginally increased zooplankton abundance and biomass. Phytoplankton and zooplankton communities were closely related to environmental factors, such as water temperature, conductivity, total phosphorus, chemical oxygen demand, and chlorophyll-a inside and outside the AME. The zooplankton:phytoplankton biomass ratio inside was slightly higher than outside the AME. Zooplankton and phytoplankton biomass were significantly positively correlated inside and outside the AME, as were chlorophyll-a and total phosphorus. We found phosphorus to be a key factor limiting primary productivity in Baima Lake, and that bottom-up effects were the main driver to control phytoplankton in the AME. Using aquatic macrophytes to reduce nutrient loads is an effective way to manage eutrophication in Baima Lake. 相似文献
10.
The aim of the study was to evaluate pattern of the aquatic macrophyte species distribution along the Danube fluvial corridor in Slovakia, and to identify the impact of environmental abiotic parameters on macrophyte species diversity. Field sampling was performed in the period 1999–2005 from the boat. Aquatic habitats were divided into 365 survey unit (SU). The survey of aquatic macrophytes and abiotic parameters followed the European standard approach EN 144184 2003. The plant mass estimate (PME – a semi-quantitative estimation of the amount of individual species in a SU, which takes into account three-dimensional development of plant stands) was estimated according to a five-point-scale in each SU; environmental pattern, were assessed over six abiotic parameters (river km, bank type, sediment type, flow velocity class, land-use type, and heavily man-modified water bodies). Altogether, four hydrologic connectivity types of aquatic habitats were distinguished: the Danube River, Open Arms, Separated Arms, and Seepage Water-bodies.
In total, 54 aquatic macrophytes were recorded for the whole data set of the Danube fluvial corridor. The PME data of true aquatic macrophytes and the length of SUs created a basis for numerical derivates, relative plant mass (RPM), mean mass indices (MMT, MMO) and the distribution ratio (d).
The results correspond with comparable studies on this topic: the highest macrophytes species diversity occurred in Separated Arms. On the contrary, macrophytes had the lowest richness in the Danube River main channel, although their diversity was slightly higher in heavily man-modified water bodies (such as the hydropower plant's reservoir and the abandoned main channel of the so-called Old Danube). Our results suggest that the lateral connectivity types of the river water bodies, primarily characterised by different hydrologic dynamics and human impact expressed as land-use types are responsible for the variability of aquatic macrophyte assemblages along the Danube corridor in Slovakia. 相似文献
11.
明渠输水系统的着生藻类异常增殖会淤塞拦污栅,降低明渠输水能力,并增加清理工作压力。目前,有关着生藻类对水动力的响应研究多在天然河流、湖泊中开展野外原型观测,针对混凝土衬砌表面着生藻类的水动力研究仍然少见。由于混凝土基质与泥沙基质的显著差异,着生藻类在衬砌明渠和自然水体中对水动力的响应特性不同。为探究水动力对明渠着生藻类生长及群落结构的影响,特开展明渠中着生藻类的培养观测及水动力冲刷实验。通过分析着生藻类叶绿素a含量、群落结构、无灰干重、细胞密度等指标,以探究不同基质粗糙度、不同生长阶段的着生藻类对不同水动力条件的响应。结果表明:着生藻类建群过程具有3个明显阶段,分别为迟滞期、指数生长期、稳定期;随着流速增大,着生藻类生物量先上升后下降,当流速v>0.6 m/s时,着生藻类的生长被显著抑制;冲刷流速增大至v=0.8 m/s的2天后,着生藻类生物量显著减少,群落多样性下降。在着生藻类建群迟滞期(实验中约3周),该阶段提高流速对着生藻类生物量的冲刷剥离效果最明显;基质粗糙度越小,着生藻类建群迟滞期越长,通过水力冲刷的除藻效果越明显。本研究探索了不同水动力条件下明渠着生藻类的响应规律,有... 相似文献
12.
种植水生植物,尤其是沉水植物,是目前广泛应用于受损水体的最主要的生态修复方法之一. 研究不同生长型沉水植物组合对水体理化因子的影响及营养物质的去除效率可为受损水生生态系统修复提供重要的科学依据. 本研究以我国水体修复中常用的3种不同生长型沉水植物苦草(Vallisneria natans)、黑藻(Hydrilla verticillata)和穗状狐尾藻(Myriophyllum spicatum)为研究对象,采用1种生长型种植和2种生长型及3种生长型混种模式,研究不同生长型沉水植物组合及其不同生长阶段对实验系统水质指标及氮、磷等营养物质去除率的影响. 结果表明,所有植物组合处理均显著提高了系统中总氮、总磷和氨氮去除率; 在实验前中期总氮、总磷和氨氮去除率最高. 从本实验受试物种组合来看,1种和2种生长型组合比3种生长型组合具有更高的生物量累积量和总氮去除率. Pearson相关性分析显示,实验系统中的pH、DO浓度与植物总生物量呈显著正相关,总氮、总磷、氨氮浓度均与植物总生物量呈显著负相关. 建议在受损浅水水生态系统修复过程中,根据生态修复不同阶段考虑不同生活型、生长型和功能群的水生植物组合; 在生态修复过程中需加强管理,如水生植物收割等,才能达到最好的修复效果. 相似文献
13.
Christopher J. Mellor Stephen J. Dugdale Grace Garner Alexander M. Milner 《水文科学杂志》2017,62(4):499-514
The impact of climate change on Arctic rivers is expected to be severe. There is therefore a need for greater understanding of Arctic river temperature processes. This study quantifies the spatio-temporal variability of water temperatures in the Kårsa River, Sweden. Water temperature was monitored over two summers within the main proglacial channel and within braids fed by different sources. Longitudinal and lateral temperature patterns were assessed in relation to prevailing hydro-meteorology. Temperature metrics in the main channel increased with distance downstream but were moderated by a large lake, while temperatures in the braids were dependent upon channel source. The high temperature standard deviation and inter-site differences within the braids highlight the importance of braided channels for creating thermal habitat heterogeneity. Temperatures were dependent on hydro-meteorological conditions, with sensitivity to air temperature maximized during cooler, rainy conditions. These results shed new light on Arctic river temperature patterns and their controlling processes. 相似文献
14.
滇池东北部沿岸带生态修复技术研究及工程示范——生态修复目标的确定及其可行性分析 总被引：8，自引：0，他引：8
连续6年对星湖仙女湖区水生植被种类、分布、生物量、水体状况进行了调查研究;共采集到水生植物24种,隶属于18科23属,可分为挺水植被、漂浮植被、浮叶植被和沉水植被4种生活型和8个植物群丛,其中苦草群丛占水生植被生物量70％以上,密齿苦草为绝对优势种;2004年与1999年比较,星湖仙女湖水体叶绿素a增加142％,透明度下降54％,水生植被盖度和生物量减少99％,水生植被群落结构趋于简化、多样性下降;星湖仙女湖水生植被发生逆向演替的主要原因是水体污染负荷增加和渔业生产的影响,削减污染负荷和控制渔业生产是促进星湖仙女湖水生植被恢复的重要途径． 相似文献
15.
N. P. Smith 《Ocean Dynamics》2004,54(3-4):435-440
Current meter and temperature data were collected over a 402-day period from an outer shelf and a tidal channel study site in the Exuma Cays, Bahamas. The shelf width is less than 2 km, and floods and ebbs through a nearby tidal channel extend across the entire shelf and reduce coherence of wind forcing and along-shelf flow. The data are used in perturbation analyses to investigate the across-shelf turbulent transport of heat and momentum over seasonal time scales. Data show a net landward transport of both heat and momentum over the course of the study, but the perturbation products contain distinct seasonal cycles. In fall and winter months, across-shelf heat and momentum fluxes are landward, while during spring and summer months fluxes are seaward. Comparison of shelf-water temperature with the temperature of bank water leaving on the ebb suggests that seasonal cycles of across-shelf heat and momentum in shelf waters are influenced by the seasonal export of relatively warm and cool water from Great Bahama Bank.Responsible Editor: Iris Grabemann 相似文献
16.
Oliver Miler Ismail Albayrak Vladimir Nikora Matthew O’Hare 《Aquatic Sciences - Research Across Boundaries》2014,76(4):465-481
Biomechanical properties and morphological characteristics of stems of eight species of submerged aquatic plants were studied to analyse (1) differences between river and lake specimens, (2) seasonal differences between winter/spring and summer/autumn specimens, and (3) change of biomechanical properties and morphological characteristics along the stems. The data show that river macrophytes display not only characteristic biomechanical traits and morphological characteristics specific to their hydraulic habitats, but also distinctive temporal changes due to seasonally varying water temperature, flow velocity, and growth phase. Furthermore, the data reveal differences between lake and river specimens that could be explained by wind exposure of the lake sampling sites and the species-specific flow requirements of the river macrophytes. Biomechanical properties and morphological characteristics varied along the stem with larger cross-sections and a higher resistance against tension and bending forces at the bottom compared to the top parts, being similar for both lake and river specimens. The acquired and analysed stem biomechanical and morphological data contribute to the plant biomechanics database to underpin a wide range of studies in aquatic ecology, river and wetland management. 相似文献
17.
《Limnologica》2017
Knowing the aquatic resources, such as emerging insects, that are entering terrestrial systems is important for food web and conservation studies, especially when water availability or quality is limited. Even though studies concerning benthic macroinvertebrates are numerous, insect emergence from lakes is less studied.To understand if water parameters (e.g., water temperature, oxygen concentration etc) determine insect emergence and the possible seasonal differences, we collected emergent insects from three different lakes in South Germany, during three seasons. We searched for common patterns of insect emergence at the three lakes. Moreover, the relative contribution of insects of aquatic origin to aerial flying arthropods was assessed, with collecting aerial flying arthropods at the shore.Chironomidae constituted the highest number of emerged insects in all lakes, however different patterns of emergence occurred in each lake (unimodal vs. bimodal) with different season-dependent times for the emergence peaks (spring, summer, beginning of autumn). Aquatic insects constituted a considerable proportion (at least 17%) of the aerial flying arthropods at the shore. The variation in insect emergence was explained by water temperature, however not by other water parameters or the nutrient values. Seasonal and spatial differences in insect emergence, should be considered when investigating aquatic-terrestrial interactions and designing conservation plans. A total biomass of up to 1.8 g m−2 of emerging insects from the littoral zone of Lake Constance can enter the terrestrial system in a year. We also provide length-dry weight relationships for emerged (adult) Chironomidae. These equations are useful to estimate the dry insect biomass from length data and currently such data lack for adult aquatic insects. 相似文献
18.
Stephanie Bond Mike J. Kirkby Jean Johnston Alistair Crowle Joseph Holden 《水文研究》2020,34(18):3777-3791
There is considerable interest in how headwater management may influence downstream flood peaks in temperate humid regions. However, there is a dearth of data on flow velocities across headwater hillslopes and limited understanding of whether surface flow velocity is influenced by seasonal changes in roughness through vegetation cycles or management. A portable hillslope flume was used to investigate overland flow velocities for four common headwater grassland habitats in northern England: Low-density Grazing, Hay Meadow, Rank Grassland and Juncus effusus Rush pasture. Overland flow velocity was measured in replicate plots for each habitat, in response to three applied flow rates, with the experiments repeated during five different periods of the annual grassland cycle. Mean annual overland flow velocity was significantly lower for the Rank Grassland habitat (0.026 m/s) followed by Low-density Grazing and Rushes (0.032 and 0.029 m/s), then Hay Meadows (0.041 m/s), which had the greatest mean annual velocity (examples from 12 L/min flow rate). Applying our mean overland flow velocities to a theoretical 100 m hillslope suggests overland flow is delayed by >1 hr on Rank Grassland when compared to Hay Meadows in an 18 mm storm. Thus grassland management is important for slowing overland flow and delaying peak flows across upland headwaters. Surface roughness was also strongly controlled by annual cycles of vegetation growth, decay, grazing and cutting. Winter overland flow velocities were significantly higher than in summer, varying between 0.004 m/s (Rushes, November) and 0.034 m/s (Rushes, June); and velocities significantly increased after cutting varying between 0.006 m/s (Hay meadows, July) and 0.054 m/s (Hay meadows, September). These results show that seasonal vegetation change should be incorporated into flood modelling, as cycles of surface roughness in grasslands strongly modify overland flow, potentially having a large impact on downstream flood peak and timing. Our data also showed that Darcy-Weisbach roughness approximations greatly over-estimated measured flow velocities. 相似文献
19.
20.
《Limnologica》2020
Oxygenated streambeds are considered a key requirement for the successful recruitment of stream fauna, including highly endangered freshwater pearl mussel Margaritifera margaritifera. Excessive amounts of fines impede exchange between open water and interstitial, leading to colmation and low oxygen levels in the juvenile habitat. Understanding the dynamic relationship between sediment delivery, transport, deposition and remobilization in relation to anthropogenic drivers is still poorly understood, yet is essential for conservation and restoration.This study analysed spatiotemporal sediment dynamics and interstitial habitat quality in five pearl mussel streams at the border region between Bavaria, Saxony and the Czech Republic during 2018 and 2019, comparing extremely dry periods with higher discharge events caused by snow melt and rainfall. Physicochemical habitat conditions within the streambed and sediment deposition were recorded in high spatial resolution along the stream courses, with a particular focus on the effects of tributaries and outflows of man-made fishponds.Habitat conditions were unsuitable for juvenile pearl mussels at the majority of sites, indicated by pronounced differences in physicochemical parameters between open water and the substrate, independent of discharge conditions. Sediment deposition varied markedly between discharge events, in terms of both the quality and quantity of deposits. Snow melt resulted in the highest sedimentation rates, but the smallest proportion of fine particles. During low flow conditions, fine sediment deposition was highly variable, ranging from 0.048 to 4.170 kg/week/m², mostly independent of flow velocity. High spatiotemporal variation was observed within and amongst stream systems, revealing different longitudinal patterns of fine sediment deposition, with catchment land use as the main driver. Temporal variability in sediment deposition was mainly associated with the discharge condition while abiotic parameters varied mainly with season.The high site-specificity of sedimentation rates and substrate conditions in response to different discharge events highlights the importance of an adapted conservation management which considers anthropogenic effects at the local scale. 相似文献