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1.
The ecosystem concept should be reappraised as a basic model for rivers, with regard for flow as an organizing variable. This would facilitate comparisons between the large rivers of humid climates, where flow regimes are comparatively regular, and those of arid and semi-arid areas, where river regimes are highly variable. Ecosystem processes might be modelled by combining the river continuum and flood pulse concepts, with refinements to accommodate a complex flood pulse (e.g. variations in stage amplitude, timing, duration, rates of rise and fall). Patch boundaries (ecotones) such as the riverine littoral zone warrant close study because they strongly influence the structure and dynamics of the ecosystem. The general model needs a quantitative basis, perhaps focused on the balance of processes involved in the physical transport and biological transformation of carbon. The ultimate test of such a model will be in its capacity to predict the effects of flow regulation. Further development, however, is limited by data. In both research and management monitoring programmes need to be established to provide information and to develop a sustained, comprehensive approach to dryland rivers as ecosystems. 相似文献
2.
Glenn R. McGregor 《河流研究与利用》2019,35(8):1119-1140
Over the last few decades as hydrologists have slowly raised their line of sight above the watershed boundary, it has become increasingly recognised that what happens in the atmosphere, as a major source of moisture for the terrestrial branch of the hydrological cycle, can strongly influence river dynamics at a range of spatial and temporal scales. Notwithstanding this, there is still a tendency for some in the river research community to restrict their gaze to the river channel or floodplain. However, Geoff Petts, the person to which this special issue is dedicated, understood well and widely encouraged a holistic view of river catchment processes. This included an acknowledgment of the role of climate, in its broadest sense, in shaping what happens within and without the river channel. The purpose of this paper therefore is to offer a broad overview of the role of some aspects of climate science in advancing knowledge in river research. Topics to be addressed include the role of climate in influencing river flow regimes, a consideration of the large‐scale climate mechanisms that drive hydrological variability within river basins at interannual to decadal timescales and atmospheric rivers and their link to surface hydrology. In reviewing these topics, a number of key knowledge gaps have emerged including attributing the causes of river flow regime changes to any one particular cause, the nonstationary and asymmetric forcing of river regimes by modes of climate variability and establishing links between atmospheric rivers, and terrestrial river channel processes, fluvial habitats, and ecological change. 相似文献
3.
The aim of this study was to identify whether environmental flows released into two lowland rivers (the Glenelg and Wimmera Rivers, western Victoria, Australia) during the spring to autumn period had successfully ameliorated the negative effects of multiple human impacts. Macroinvertebrates and a range of physico‐chemical variables were sampled from three reaches in each river. Both rivers were sampled during three environmental release seasons with average‐sized releases (1997–1998, 1998–1999 and 2001–2002) and two drought seasons with limited releases (1999–2000 and 2000–2001). The effects of releasing average‐sized environmental flows on macroinvertebrates and physico‐chemical variables were assessed by comparison with data from the two drought seasons. For the Glenelg River, data from a reference season prior to the release of environmental flows (1995–1996) was also compared to data from the five environmental flow seasons. Multivariate analyses revealed four pieces of evidence indicating that the release of environmental flows effectively slowed the process of environmental degradation in the Glenelg River but not in the Wimmera River: (1) the magnitude of the river discharge was dependent on the size of environmental flow releases; (2) in the Wimmera River, water quality deteriorated markedly during the two drought seasons and correlated strongly with macroinvertebrate assemblage structure, but this was not observed in the Glenelg River; (3) the taxonomic composition of the macroinvertebrate assemblages among contrasting flow release seasons reflected the severe deterioration in water quality of the Wimmera River; (4) despite two drought seasons with minimal environmental flow releases, the macroinvertebrate assemblage in the Glenelg River did not differ from the average‐release seasons, nor did it return to a pre‐environmental flows condition. Therefore, it appears that environmental flow releases did sustain the macroinvertebrate assemblage and maintain reasonable water quality in the Glenelg River. However, in the Wimmera River, release volumes were too small to maintain low salinities and were associated with marked changes in the macroinvertebrate assemblage. Therefore, there are multiple lines of evidence that environmental flow releases of sufficient magnitude may slow the process of degradation in a regulated lowland river. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
4.
Maintaining the natural complexity of water temperature regimes is a key to maintaining diverse biological communities. Insect communities, food webs, and fish respond to the magnitude and duration of water temperature fluctuations. Disruption of these natural patterns has the potential to alter physiological processes, behavioural adaptations, and community structure and dynamics. We analysed multiple >300‐day time series of water temperature from the Willamette River basin, Oregon, to assess the impact of large multi‐purpose dams on water temperature variability at temporal scales ranging from 1 to 32 days, short temporal scales that are commonly ignored. We applied wavelet analysis to quantify the variability of water temperature at multiple temporal scales simultaneously. We compared water temperature regimes above and below dams and before and after dam construction. The advantages of wavelet analysis are the ability to examine all temporal scales simultaneously and independently as well as the ability to preserve the temporal context of the wavelet coefficients. We were able to detect significant (p < 0.0001) reductions in water temperature variability, defined as the variability of the wavelet coefficients, as a result of dams at the 1‐, 2‐, 4‐, and 8‐day scales. There were no significant differences in water temperature variability between managed and natural flows at the 16‐ and 32‐day scale (p = 0.80). In addition to the well‐documented effects of dams on seasonal patterns in water temperature or on water temperature extremes, our results demonstrate that dams have significantly muted the small temporal scale variance in water temperature patterns to which many organisms may have been adapted. Conserving or restoring natural temperature patterns in rivers will require attention to these small‐scale complexities. Published in 2007 by John Wiley & Sons, Ltd. 相似文献
5.
The Peace–Athabasca Delta (PAD) in northern Canada is one of the world's largest freshwater deltas. Concern developed over the ecological health of this system in the early 1970s following regulation of its main headwater tributary, the Peace River. Continued drying of the delta into the 1990s resulted in the initiation of two major science programs, the Northern River Basins Study and the Peace–Athabasca Delta Technical Studies. Recognizing the importance of water to restoring and maintaining biological productivity and diversity of the PAD, a series of studies was initiated to explain the reasons for the protracted drying and to design methods to restore flooding. These studies demonstrated that open‐water floods from the Peace River were unlikely to flood the ecologically sensitive perched basins within the PAD. Moreover they discovered that most large‐scale overbank flooding resulted from ice‐jams formed during spring break‐up. Increases in freeze‐up ice levels due to enhanced winter flows from the reservoir and a decrease in spring snowmelt runoff from downstream tributaries were suggested as being responsible for a decline in the frequency and severity of ice‐jam floods. Based on results from numerical modelling studies of ice‐jams, a flow augmentation strategy was designed to aid the formation of ice‐jams near the PAD. Results of a test trial based on this strategy are presented. An update is also provided about ecological studies conducted since the delta was recharged by floodwaters in 1996. Copyright © 2002 Environment Canada. Published by John Wiley & Sons, Ltd. 相似文献
6.
塔里木灌区引水前后环境流特性变化 总被引：1，自引：0，他引：1
基于水文改变指标基本分析方法,筛选建立了环境流评价指标,着重分析了塔里木灌区引水对塔里木河干流阿拉尔和新渠满断面环境流变化的影响。结果表明:在灌区大量引水灌溉前后,干流两个主要水文站的环境流组成分别呈现出不同程度的变化,环境流组成趋于单一化;各水文站的流量事件以枯水流量事件为主;引水对特枯流量事件、高流量脉冲事件和大洪水事件的影响较大。结合环境流指标和生态系统响应关系,制定了面向生态的水资源优化调度方案,为流域生态治理和水量分配提供了参考。 相似文献
7.
Abstract This paper presents a first attempt to estimate the volume of water required for the maintenance of freshwater-dependent ecosystems at the global scale. This total environmental water requirement consists of ecologically relevant low-flow and high-flow components and depends upon the objective of environmental water management. Both components are related to river flow variability and estimated by conceptual rules from discharge time series simulated by the global hydrology model. A water stress indicator is further defined, which shows what proportion of the utilizable water in world river basins is currently withdrawn for direct human use and where this use is in conflict with environmental water requirements. The paper presents an estimate of environmental water requirements for 128 major river basins and drainage regions of the world. It is shown that approximately 20 to 50 percent of the mean annual river flow in different basins needs to be allocated to freshwater-dependent ecosystems to maintain them in fair conditions. This is unlikely to be possible in many developing countries in Asia and North Africa, in parts of Australia, North America, and Europe, where current total direct water withdrawals (primarily for irrigation) already tap into the estimated environmental water requirements. Over 1.4 billion people currently live in river basins with high environmental water stress. This number will increase as water withdrawals grow and if environmental water allocations remain beyond the common practice in river basin management. This paper suggests that estimates of environmental water requirements should be the integral part of global water assessments and projections of global food production. 相似文献
8.
Solomon S. Henson Dylan S. Ahearn Randy A. Dahlgren Erwin Van Nieuwenhuyse Kenneth W. Tate William E. Fleenor 《河流研究与利用》2007,23(2):185-200
Controlled water releases from reservoirs (i.e. artificial floods) are used as a management technique to remove fine sediments and detrital materials from spawning gravels, mobilize gravel bars and clear encroaching brush from stream banks. The effects of a managed release event on water quality were investigated on the lower Mokelumne River in the western Sierra Nevada, California. The managed release was characterized by an increase in flow over a 4‐day period (from 11 to 57 m3 s−1). Automatic pump samplers were used to collect samples for water quality from 0.7, 16.4, 37.4 and 54.4 km below Camanche Dam. These sampling sites provided water quality data for three distinct stream reaches: a gravel and sand‐textured substrate reach (0.7–16.4 km), a reach characterized by lentic conditions associated with a small reservoir (16.4–37.4 km), and fine sand and silt‐textured substrate reach (37.4–54.4 km). Water samples were analysed for total suspended solids (TSS), total nitrogen, ammonium (NH4‐N), nitrate (NO3‐N), total phosphorus, soluble reactive phosphorus (SRP), dissolved organic carbon (DOC), foecal coliforms and E. coli. Chemographs for all constituents exhibited spikes in concentration with each increase in streamflow for the rising limb. Fluxes of TSS, total P and total N released from the 0.7 to 16.4 km reach were 322, 0.32 and 0.70 Mg, respectively. The small reservoir acted as a sink for particulate materials retaining about 50% of TSS, 48% of total P and 43% of total N. However, the reservoir acted as a source of dissolved nutrients (NO3‐N = 0.28 Mg and SRP = 0.055 Mg). The stream reach below the reservoir (37.4 to 54.4 km) was a source of particulate materials, dissolved nutrients and bacteria, possibly due to agricultural and urban inputs. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
9.
W. J. Young B. C. Chessman W. D. Erskine T. A. Raadik D. J. Wimbush J. Tilleard A. J. Jakeman I. Varley T. J. Verhoeven 《河流研究与利用》2004,20(6):733-750
A rapid process of water reform in Australia has seen governments rely heavily on ‘expert’ or ‘scientific’ panel advice for river condition and environmental flow assessments. These multi‐disciplinary teams of scientists have enabled a quick and relatively inexpensive injection of science into what is often a data‐poor decision process. However, expert panels suffer from several important drawbacks including a lack of transparency and repeatability, and unquantified uncertainty. In the case of the Snowy Mountains hydro‐electric scheme, a government initiative to corporatize the government‐owned authority led to the establishment of the Snowy Water Inquiry (SWI) that was required by law to propose and evaluate (within a six month period) a range of options for future river regulation, diversion and environmental flows. A Scientific Reference Panel (SRP) was therefore established to assess current (1998) river condition and to assess the likely environments benefits of a range of environmental flow options. The SRP attempted to overcome a number of the typical shortcomings of the expert panel approach by (i) integrating available data with expert opinion in its assessments, and (ii) developing a composite River Condition Index (RCI) underpinned by a conceptual framework that links habitat and biotic condition and comprises several sub‐indices that translate qualitative assessments (relative to a pre‐disturbance reference condition) into numeric values in a transparent and repeatable manner. The SRP estimated the level of uncertainty associated with its various assessments, and used these to quantify uncertainty estimates on RCI values. In this paper the RCI is described and its use is illustrated through presentation of the assessments of current (1998) river condition and the associated uncertainty analyses that were made for the rivers in the Snowy Mountains area. The results suggest that in spite of high levels of uncertainty associated with individual assessments, the SRP was able to demonstrate significant difference in current condition between rivers, and in likely future condition between different environmental flow scenarios. Although further investigations and lengthy negotiations occurred subsequent to the SWI to achieve corporatization, the environmental assessments made in the SWI provided the most comprehensive source of information available to governments and the community regarding the likely environmental outcomes of the proposed changes. Subsequent to the SWI the scenario‐based approach to environmental flow assessment has become increasingly common internationally, and major Australian river condition assessments have adopted a similar conceptual framework to the RCI. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
10.
黄河下游引黄灌区水沙调控模式及其特点分析 总被引：1，自引：0，他引：1
黄河挟带大量泥沙,沿岸地区进行引水灌溉不能忽略引入泥沙的处理问题。自20世纪50年代黄河下游发展引黄灌溉事业以来,目前不同灌区已基本形成适宜自身地理特点和灌溉需求的引水输水类型和入渠泥沙处理方式。本文根据引黄灌区所处河道位置和地域条件,结合灌区灌溉类型和泥沙处理方式,归纳提出了4种黄河下游引黄灌区水沙调控模式,即,沉沙输水模式、输水沉沙模式、分水滞沙模式和输水输沙模式;根据不同水沙调控模式的形成条件、调控效果和存在的水沙问题,分析了适合不同水沙调控模式的输水输沙关键技术和重点调控目标,分别为沉粗排细调控、远距离输沙调控、分沙入支渠调控和泥沙入田调控;泥沙远距离分散输送技术是实现灌区水沙资源优化配置的重点。 相似文献
11.
受传统用水习惯的影响,在库水日趋缺乏的情况下,三坝灌区的区间水引用仍不能广泛开展,严重制约了农业和灌区的发展.文中对灌区供水现状进行了分析,并提出通过配套工程、科学引导来实现对水资源的合理利用,从而有效促进农业生产,取得良好的经济和社会效益. 相似文献
12.
Considerable attention has been paid to the downstream effects of reservoirs on the ecology of rivers, streams and wetlands. However, most reservoirs were constructed well before ecological concerns became prominent. Little attention has been given to the question of what extent existing structures and management systems can accommodate changes. The paper discusses this matter and a range of associated issues. It is concluded that many problems can be rectified by structural means but that such rectification will be very expensive. While based primarily on Australian systems, the conclusions and examination are considered to be globally applicable. 相似文献
13.
小浪底水库调水调沙对黄河下游河道冲淤的影响分析 总被引：1，自引：1，他引：1
分析了自2002年起小浪底水库每年实施调水调沙在黄河下游河道冲刷中的作用,指出小浪底水库调水调沙有利于下游河道冲刷,但通过资料分析,冲刷的幅度有逐年变小的趋势,为此,恰当地评价当前调水调沙的作用十分必要. 相似文献
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The Basic Flow is a methodology used to calculate environmental flow needs for river regulation. It has gained increased recognition in Spain for hydrological planning. It is based on the study of irregularities in hydrological series of daily mean flows using the simple moving average model as a tool to extract the relevant information. The Basic Flow Methodology (BFM), beyond providing a unique minimum flow value, constitutes a complex management proposal for regulated rivers which includes other management aspects affecting the biological functioning of a river (such as the necessity of flow variability, bankfull flows or varying flow rates) through the establishment of monthly instream flow requirements. This paper presents a practical application of the BFM in the Silvan stream, a natural mountain stream impacted by a hydroelectric regulation project. Results are discussed in terms of physical habitat created and compared to those obtained from the application of another method based on the Instream Flow Incremental Methodology, using a set of computer programs (RHYHABSIM) for physical habitat simulation. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
16.
现代城市河流治理备受关注,除了要满足防洪排涝要求,保护河道的自然风貌,美化环境,也要符合生态的科学性原则[1],该文通过室内水槽模型试验,对城市河道修建挡水建筑物后在3种不同流量下水流特性变化进行实验研究。通过分析作者认为开口坝更有利于河道的流动水不给,且产生多级流速带,故可适应不同水生生物的生存,开口坝更利于坝体的稳定。本试验能为兼顾生态的城市河道治理提供依据。 相似文献
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Many river restoration projects are focusing on restoring environmental flow regimes to improve ecosystem health in rivers that have been developed for water supply, hydropower generation, flood control, navigation, and other purposes. In efforts to prevent future ecological damage, water supply planners in some parts of the world are beginning to address the water needs of river ecosystems proactively by reserving some portion of river flows for ecosystem support. These restorative and protective actions require development of scientifically credible estimates of environmental flow needs. This paper describes an adaptive, inter‐disciplinary, science‐based process for developing environmental flow recommendations. It has been designed for use in a variety of water management activities, including flow restoration projects, and can be tailored according to available time and resources for determining environmental flow needs. The five‐step process includes: (1) an orientation meeting; (2) a literature review and summary of existing knowledge about flow‐dependent biota and ecological processes of concern; (3) a workshop to develop ecological objectives and initial flow recommendations, and identify key information gaps; (4) implementation of the flow recommendations on a trial basis to test hypotheses and reduce uncertainties; and (5) monitoring system response and conducting further research as warranted. A range of recommended flows are developed for the low flows in each month, high flow pulses throughout the year, and floods with targeted inter‐annual frequencies. We describe an application of this process to the Savannah River, in which the resultant flow recommendations were incorporated into a comprehensive river basin planning process conducted by the Corps of Engineers, and used to initiate the adaptive management of Thurmond Dam. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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The magnitude, timing and duration of precipitation events can vary considerably across spatial and temporal scales. In lotic ecosystems, such differences in precipitation patterns can strongly influence water availability, which in turn affects the population dynamics of stream biota. Connectivity flow thresholds were developed for the movement of juvenile steelhead trout using hydraulic modelling for 37 coastal California streams. Spatial patterns in magnitude, and spatiotemporal patterns in duration and timing of flows meeting threshold levels were analysed using long‐term flow gaging data. Flow thresholds for the movement of juvenile steelhead through riffle sites varied from 0.06 (San Luisito Creek, Elder Creek) to 0.82 (Redwood Creek) cms (cubic meters per second). Flow thresholds increased positively with mean bankfull width, indicating that more water is required for fish movement in wider streams. Precipitation was a dominant driver of flow duration, with flows meeting thresholds longer in wetter regions of the state when compared with drier regions. On the rising limb of the hydrograph, the onset of meeting flow thresholds was influenced by stream width, with thresholds being met earlier in wider streams when compared with narrower streams. On the receding limb of the hydrograph, flow threshold timing was influenced by precipitation, with flows remaining above the threshold later in wetter regions when compared with drier regions. Based on these findings, we recommend that the management of aquatic resources for a broad range of objectives consider regional scales that account for local patterns in precipitation, channel form and prevailing water year conditions to accommodate California's wide spatiotemporal diversity of water availability. 相似文献