基于流域尺度的城市河流治理技术体系——以凉水河为例

城市河流作为城市的重要组成部分,对城市经济发展、市民安居有着巨大影响,但相当一部分城市河流或河段因遭受重污染,黑臭问题严重。河流治理领域自19世纪至今已有长足发展,治理理念从单纯的"水利工程治理"到"近自然河道治理工程"再向"基于流域管理的治理"转变。基于流域尺度的河流治理是复杂的系统工程,包括多方面内容,以凉水河流域为例加以阐述,其治理技术包含了高品质再生水处理技术、河道污水口除臭技术、促流净水技术和河坡植生增绿技术等。     

广州市城市河流低水位运行生态修复理念与实践

在系统分析城市河流治理突出难题的基础上，研究了低水位运行下底泥污染物生化降解机理及河流生态构建原理，创新提出了城市河流低水位运行生态修复理念。相对于高水位，低水位运行使河道水体光照、溶解氧、水温和水动力等条件明显改善，显著提升泥-水界面好氧硝化效率，快速消除底泥黑臭，并驱动底泥深层厌氧反硝化效应，实现污染底泥碳、氮、硫等耗氧物质同步去除，从而将底泥从污染“源”转变为“汇”，有助于上覆水体净化。此外，低水位运行有利于营造洲-滩-槽多样化生境，构建更为复杂的河流生态系统，显著提升城市河流污染“免疫力”。     

现代城市河道生态修复方法与实践

河道生态修复是河道污染治理的有效手段之一,其主要内容包括水质水文条件、河流地貌特征以及生物物种等方面的修复。文中通过分析现有城市河流生态破坏现状及其成因,在生态修复理论基础上,结合湖南张家界索溪河综合治理工程,分析说明河流生态修复方法的使用。     

国内外城市河流治理现状

在分析国内外城市河流治理思路转变的基础上,介绍了以日本、韩国、美国和欧洲国家为代表的国外城市河流治理现状及我国目前在城市河流治理领域的研究现状及治理实例,指出了我国与国外发达国家在河流生态修复的思路、技术和方法上的差距,认为今后我国城市河流治理应更多地考虑城市河流与周围区域的整体关系、与带动经济和满足居民生活需求等多目标相结合等问题。     

城市中小河流综合整治措施分析

以城市中的河流为研究对象,提出了城市中河流的整治不应只局限在防洪、排涝等传统水利的范围内,而应增加改善水质、清於、断面的生态系统恢复、打通因人为原因及城市建设填埋的断头河流、调整调度措施改变网河区内河流的水流方向、枯季为干枯的河流补水、增加河流水文化功能等多种措施,将城市中的河流治理成为不仅可以为城市减少灾害,同时又可...     

关于大沙河治理工程的思考

城市化后，河流的基本特性、功能以及河流进行空间管理的要求都发生了显著变化。本文根据深大沙河治理的实际情况提出现代治河工程的一些见解，以期达到对城市河流治理和管理更加科学合理。     

城市河流的治理与研究展望

城市河流是城市的灵气所在,在城市环境、生态、景观、文化等方面具有不可替代的作用。本文重点阐述了城市河流的基本功能、在城市发展中的地位、治理目标、关键技术问题以及需要开展的研究课题,是一篇综述性论文,对于我国城市河流的治理和研究有参考价值。     

沣渭新区河流综合治理浅谈

河流作为最重要的资源和环境载体,关系到城市生存,影响着城市发展,是影响城市风格和环境的重要因素。本文在对沣渭新区河流治理现状与存在问题分析的基础上,结合沣渭新区城市总体规划,提出几点在新形势下的河流治理思路。     

关于城市中小河流治理的思考

针对我国城市河流的治理现状以及国际上河流治理的发展趋势,提出城市河流治理的一些有效措施。     

试论在水生态保护与修复下的中小河流治理

中小河流治理是＂十二五＂期间的水利工作重点。目前我国中小河流治理过程中,出现了河道被渠化、硬化,河流生态系统被破坏;水资源被过分开发、河流生态需水不能保证;污水排放入河、水质严重污染等问题。针对相关问题,提出了城市河流治理过程中应减少河流的硬化、渠化,提倡建设生态河岸、控制向河流排放污水及注重后期监管等治理措施。     

Effect of urbanization on stream hydraulics

Urbanization results in major changes to stream morphology and hydrology with the latter often cited as a primary stressor of urban stream ecosystems. These modifications unequivocally alter stream hydraulics, but little is known about such impacts. Hydraulic changes due to urbanization were demonstrated using two‐dimensional hydrodynamic model simulations, comparing urban and non‐urban stream reaches. We investigated three ecologically relevant hydraulic characteristics: bed mobilization, retentive habitat, and floodplain inundation, using hydraulic metrics bed shear stress, shallow slow‐water habitat (SSWH) area, and floodplain inundation area. We hypothesized that urbanization would substantially increase bed mobilization, decrease retentive habitat, and due to increased channel size would decrease floodplain inundation. Relative percent area of bed disturbance was 4 times higher, compared with that of the non‐urban stream at bankfull discharge. SSWH availability rapidly diminished in the urban stream as discharge increased, with SSWH area and patch size 2 times smaller than the non‐urban stream for a frequently occurring flow 0.7 times bankfull discharge. Floodplain inundation decreased in frequency and duration. These results demonstrate changes in hydraulics due to urbanization that may impact on physical habitat in streams. New “water sensitive” approaches to stormwater management could be enhanced by specification of hydraulic regimes capable of supporting healthy stream habitats. We propose that a complete management approach should include the goals of restoration and protection of natural hydraulic processes, particularly those that support ecological and geomorphic functioning of streams.     

Distribution of heavy metals in freshwater ecosystem of a small stream impacted by urban drainage.

This paper focuses on the study of heavy metals' remobilisation possibilities and changes of distribution coefficients leading to remobilisation in a stream as a result of changing conditions caused by urban drainage. The paper also reports consequent changes of bioaccumulation coefficient for different species of the benthic community, which seems to be the best indicator of aquatic community quality in small urban streams. The paper presents results obtained during field monitoring as well as results obtained during laboratory experiment. The field monitoring identified in the study area (the Botic Creek) three heavy metals (Cu, Zn and Pb), which are the main sources of toxicological risk in this area. Based on the monitoring, these elements were used for laboratory experiment, where their behaviour during changing conditions was studied. The experiment shows that changing conditions in the stream, caused by urban drainage, significantly impact the fate of heavy metals in aquatic ecosystems and that these elements have different preferences to bind to a particular geochemical fraction of sediment, which consequently means different bioavailability.     

Ecological considerations in the development and application of instream flow-habitat models

Methodologies for recommending instream flows for protecting lotic ecosystems are evolving amid constructive criticism. During this period of change it is important that all concerned parties are aware of the ecological factors that control stream ecosystems and fish populations. Ecological factors relating to stream ecology, population dynamics, energetics, predation, and competition are reviewed to explain why indices of microhabitat availability are not expected to be consistent predictors of fish population density. Implications of these concepts for development and application of instream flow-habitat models for recommending instream flow regimes are discussed. Current ecological theory and empirical studies support the hypothesis that microhabitat availability may limit fish populations but not continuously. Therefore, assessments must consider the limiting habitat events as well as temperature and water quality constraints. Also, invertebrates and non-game fishes must be considered in instream flow assessments because of their importance in stream ecosystems.     

Two-dimensional physical habitat modeling of effects of habitat structures on urban stream restoration

River corridors, even if highly modified or degraded, still provide important habitats for numerous biological species, and carry high aesthetic and economic values. One of the keys to urban stream restoration is recovery and maintenance of ecological flows sufficient to sustain aquatic ecosystems. In this study, the Hongje Stream in the Seoul metropolitan area of Korea was selected for evaluating a physically-based habitat with and without habitat structures. The potential value of the aquatic habitat was ...     

Stay with the flow: How macroinvertebrate communities recover during the rewetting phase in Alpine streams affected by an exceptional drought

Droughts are affecting an increasing number of lotic ecosystems worldwide due to the combined effects of climatic and anthropogenic pressures. Unlike naturally intermittent rivers, where the drying phase is a part of the annual flow regime, water scarcity in Alpine rivers represents a relatively recent phenomenon and, therefore, a major threat for the biodiversity of these lotic ecosystems. However, Alpine stream community response to drought is still poorly investigated. Here, we assess the recovery of macroinvertebrates in two Alpine streams after a supraseasonal drought. As water returned, a total of 10 sampling sessions were carried out, and temporal patterns in diversity, density, and taxonomic composition of benthic communities, as well as in the percentage of functional feeding groups, were investigated. We found that the resistance of invertebrate communities in Alpine streams is generally low: drought markedly reduced the diversity and density of macroinvertebrates. Conversely, our results suggest that the passive dispersal by drift from the upstream river sections seems the most probable mechanism promoting the post‐drought recovery. Nevertheless, this resilience ability appears to be stream specific and influenced by intrinsic stream characteristics, including the flow permanence and distance from the nearest upstream perennial reach. This work sheds light on the ecological consequences of droughts on macroinvertebrate communities. As flow intermittency in Alpine areas is expected to intensify under current global change scenarios, results of this study provide important information to predict changes in the taxonomic composition and diversity of macroinvertebrate communities.     

Do existing ecological classifications characterize the spatial variability of stream temperatures in the Great Lakes Basin,Ontario?

Ecological classifications of stream ecosystems have been used to develop monitoring programs, identify reference and impacted systems, and focus conservation efforts. One of the most influential, but highly variable, components of stream ecosystems is water temperature but few geographically broad-scale and long-term programs exist to assess and monitor temperatures. This study evaluated if existing ecological classifications could be used to categorize the similarities and differences in stream temperatures across the Ontario portion of the Great Lakes Basin. Concordance between the spatial variability in temperatures and an existing ecological classification would support the use of that classification to define areas with similar temperatures, guide the development of a monitoring program, and inform management programs. The five classifications evaluated were the ecoregions and ecodistricts defined in the National Ecological Framework for Canada, the ecoregions and ecodistricts defined in the Ecological Land Classification of Ontario, and the aquatic ecosystem units defined in the Aquatic Ecosystem Classification (AEC) for the Ontario portion of the Great Lakes Basin. Hierarchical linear modelling and corrected Akaike Information Criterion indicated that the ecodistrict classifications characterized more of the spatial variability in temperatures than the ecoregion and AEC classification but temperatures were more variable among sites within classes than between classes. Therefore, none of the existing ecological classifications could be used to characterize thermal variability. Future research should examine if the inability of the existing classifications to capture the thermal variability translates into inaccurate classification of other ecosystem components such as water quality, and macroinvertebrate and fish assemblages.     

In‐stream construction‐induced suspended sediment in riverine ecosystems

Construction activities within the wetted‐perimeter of rivers, referred to as in‐stream construction, are prevalent economically and environmentally motivated activities having direct interactions with sensitive lotic environments. Currently, there is a paucity of research related to in‐stream construction activities and their effects on aquatic ecosystems. In‐stream construction‐induced suspended sediment may result in harmful effects to aquatic flora and fauna. Regulatory frameworks worldwide focus primarily on concentration, with limited consideration for duration and no consideration for spatial extents of suspended sediment exposures. This research develops theoretical concentration, duration, and spatial extent exposure risk relationships for riverine ecosystems to demonstrate the influence of each mechanism during typical in‐stream construction activities. To reduce exposure risk, concentration and duration may be considered pragmatically, based on anticipated activity characteristics and site conditions. Spatial exposure characteristics are important to consider, as illustrated by our finding that activities located near the channel centerline may result in greater exposure risk than similar activities conducted near the streambank. Current regulatory frameworks worldwide do not sufficiently consider all exposure risk mechanisms present during in‐stream construction‐induced suspended sediment releases, possibly inhibiting efforts to reduce adverse environmental effects. This research improves our understanding of suspended sediment in lotic environments and may help environmental managers better evaluate and manage in‐stream construction activities.     

Nature‐like fishways as compensatory lotic habitats

Damming of rivers disrupts migration of fish and results in lotic habitats being both scarcer and spaced further apart, ultimately affecting riverine fish communities. Nature‐like fishways are often designed as bypass channels, constructed with natural materials that reroute part of the water around weirs and dams, restoring longitudinal connectivity as well as forming nature‐mimicking habitats. We evaluated the potential of such bypasses to function as compensatory lotic habitats by comparing fish fauna in 23 bypasses to adjacent lotic stream habitats in a same‐river pairwise design. Bypasses were narrower, shallower, and less shaded than adjacent stream habitats, but very few significant differences could be detected in the fish communities, indicating the potential of such nature‐like fishways to constitute compensatory lotic habitats for fish. Analyses also indicated how bypass design may be altered to favour or disfavour certain target species. Generally, narrower and shallower bypasses with high gradient favoured brown trout (Salmo trutta), whereas European eel (Anguilla anguilla) were more abundant at sites with lower gradient. Finally, to increase the impact of these compensatory habitats on running water ecosystems, we suggest that the size of bypasses should be maximized in areas where natural stream habitats have been lost.     

Biological consequences of agricultural and urban land-use along the Maumee River,a major tributary to the Laurentian Great Lakes watershed

Many riverine systems are impacted by a combination of agricultural and urban land use. In this study, we assessed the impacts of high intensity agriculture and urban land use in the Maumee River, the largest Great Lakes tributary, using sunfish (Lepomis spp.). The land use gradient from agricultural headwaters to densely urban areas was hypothesized to be paralleled by a shift in the chemical signature and biological effects. We caged hatchery-reared sunfish at field sites and collected concurrently resident sunfish. We analyzed fish for alterations in morphological indices, hematological characteristics, and anatomical development. Water, sediment, and fish tissues were analyzed for pesticides, pharmaceuticals, and personal care products. Chemicals were detected in all samples, and no clear agricultural/urban distinction in water chemistry was apparent. We detected forty-three chemicals (19% of analyzed) in at least half of the water samples, and 101 chemicals (44%) in at least one water sample. The pesticides desethylatrazine (100% of samples) and heptachlor epoxide (89%), and pharmaceuticals iopamidol (100%) and sulfamethoxazole (89%) were frequently detected. Resident sunfish were more sensitive than caged sunfish, and both experienced elevated stress responses at urban sites. Declining biological indices suggest contaminant-related impairments which may have altered resource allocation and could have contributed to decreased sexual maturity. Agricultural, and especially urban, contaminants entering aquatic ecosystems as non-point sources affect sunfish biology through acute and chronic exposure. Natural resource managers are advised to broadly assess stressors prior to investing into stream restoration efforts.     

CATCHMENT CHARACTERISTICS AND PLANT RECRUITMENT FROM SEDIMENT IN STREAM AND MEADOW HABITATS

Streams and rivers constitute a dense network with a large interface to the surrounding landscape and are thus highly susceptible to anthropogenic pressures related to land‐use activities in adjacent riparian and upland areas. In the present study, we investigated the influence of catchment characteristics on potential propagule and species recruitment from sediment in lowland stream ecosystems. We tested the following hypotheses: (1) catchment characteristics affect species recruitment from stream sediment in both stream and riparian habitats and (2) recruitment of species associated with undisturbed fen‐meadow habitats is higher in places with natural vegetation in the riparian zones. A large number of wetland species emerged from the stream sediment and sediment recruitment and therefore can act as an important dispersal corridor for common species in stream ecosystems. The recruited propagules were dominated by terrestrial species, but amphibious and aquatic species also appeared, particularly in the artificial stream channels. These included among others species within the genera Ranunculus sp., Callitriche sp. and Potamogeton sp. The large between‐site differences in land‐use characteristics in the riparian zones of the studied stream reaches, both locally and along upstream reaches, were not reflected in species recruitment from the stream sediments. Thus, most recruited species were common and widely distributed, and they were dominated by species with ruderal and competitive life history strategies, whereas only few species associated with fen‐meadow vegetation were recruited. From these findings, we infer not only that hydrochorous dispersal of species can be a potential efficient dispersal vector in agricultural landscapes but also that limitations can exist as to which species can be recruited. We suggest that further studies are performed to elucidate this issue further. Copyright © 2012 John Wiley & Sons, Ltd.