An overview of river health assessment: philosophies, practice, problems and prognosis

1. Philosophically, the term ‘river health’ is useful because it is readily interpreted by the general public and evokes societal concern about human impacts on rivers. The common goal of achieving healthy rivers unites ecologists and the general public because the value of the ecologists’ contributions is clear (and, hence, funded). The difficulty arises in the choice of relevant symptoms because there is a wide variety that can be measured with varying accuracy at a broad range of spatial scales. These indicators may respond to impacts at different time scales, and no single indicator is a ‘silver bullet’ that reveals river health unequivocally. 2. In practice, choice of indicator often shows personal bias, technical considerations, and constraints of knowledge. Selection of appropriate spatial and temporal scales for these measures is crucial. Although most measurements are spot samples (e.g. concentration, abundance, species richness), assessment of river health based on changes in ecological processes such as post-disturbance recovery rate or nutrient spiralling lengths may be more suitable in some cases. 3. Problems include validation of the indicator, its response time at a range of scales, and the reliability of its measurement. Assessment of river health should be accurate, timely (warning of deterioration instead of waiting until the patient is terminal), rapid (so that the response is swift), and inexpensive. The connectedness of running waters with their floodplains and catchments must be explicitly recognized. Hydrological and geomorphological modifications of rivers usually affect their health by severing or impairing the linkages, and the ‘cure’ may lie in addressing these causes. Often, we need landscape-level data for management because this is the scale where cumulative effects of impacts are evident. 4. The prognosis is uncertain. We need to explore further the use of integrative measures of river health, and focus on establishing a link between the measure and impaired ecological integrity. Ecosystem-level variables (e.g. estimates of production or respiration) show promise and recent technological advances make these more accessible. Data analytical approaches (e.g. multimetric vs. predictive models) need further debate but must not overlook the importance of high quality and relevant input data. Appropriate choice of indicators, rigorous sampling and analysis, and careful data interpretation must be matched with effective communication to policy-makers and the public. When this occurs, the concept of ‘river health’ becomes more than just a rhetorical tool.‘     

Measuring riparian condition: A comparison of assessments by landholders and scientists

Summary   To a large extent, the condition of riparian areas in Australia is determined by the management actions of private landholders. In this study, we discuss findings from our research in the Goulburn Broken Catchment comparing landholder and scientist assessments of the condition of riparian areas. We interviewed 33 landholders and undertook ecological condition assessments at 38 sites on privately managed river frontages. Using mail survey data that included landholder assessments of riparian condition, we were then able to compare landholder and scientist assessments. Despite substantial effort in this catchment to improve riparian condition, the riparian zones sampled were generally in poor condition. Landholder and scientist assessments of ecological condition showed a significant positive correlation. This indicated broad agreement, despite some substantial differences in assessment of some components of the condition score. Disparities between scientist and landholder assessments were related to the estimation of native ground cover, leaf litter cover and tree canopy continuity within riparian zones. The capacity of this simple assessment tool to differentiate varying levels of riparian zone degradation demonstrates the potential utility of mailed, self-assessment surveys to inform management programs and decisions about the allocation of resources for restoration efforts.     

Biological assessment of European lakes: ecological rationale and human impacts

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AusRivAS: using macroinvertebrates to assess ecological condition of rivers in Western Australia

1. AusRivAS (Australian River Assessment Scheme) models were developed, using macroinvertebrates as indicators, to assess the ecological condition of rivers in Western Australia as part of an Australia-wide program. The models were based on data from 188 minimally disturbed reference sites and are similar to RIVPACS models used in Britain. The major habitats in the rivers (macrophyte, channel) were sampled separately and macroinvertebrates collected were identified to family level. 2. Laboratory sorting of preserved macroinvertebrate samples recovered about 90% of families present when 150 animals were collected, whereas live picking in the field recovered only 76%. 3. Reference sites clustered into five groups on the basis of macroinvertebrate families present. Using seven physical variables, a discriminant function allocated 73% of sites to the correct classification group. A discriminant function based on seven physical and two chemical variables allocated 81% of sites to the correct group. However, when the same reference sites were re-sampled the following year, the nine variable discriminant function misallocated more sites than the seven variable function, owing to annual fluctuations in water chemistry that were not accompanied by changes in fauna. 4. In preliminary testing, the wet season channel model correctly assessed 80% of reference sites as undisturbed in the year subsequent to model building (10% of sites were expected to rate as disturbed because the 10th percentile was used as the threshold for disturbance). Nine sites from an independent data set, all thought to be disturbed, were assessed as such by the model. Results from twenty test sites, chosen because they represented a wide range of ecological condition, were less clear-cut. In its current state the model reliably distinguishes undisturbed and severely disturbed sites. Subtle impacts are either detected inconsistently or do not affect ecological condition.     

Assessment of river condition at a large spatial scale using predictive models

1. RIVPACS-type predictive models were developed at a relatively large spatial scale for the Australian state called New South Wales (NSW, 801 428 km²). Aquatic macroinvertebrate samples and physical and chemical data were collected from 250 reference sites (little affected by human activities) and 23 test sites (with known human impacts) throughout NSW in autumn and spring 1995 and identified mostly to family level. Reference sites were grouped based on their macroinvertebrate data using classification (UPGMA) and ordination techniques. Relationships between macroinvertebrate and environmental data were established using principal axis correlations and stepwise multiple discriminant function analysis. models for predicting invertebrate assemblages were developed separately for edge and riffle habitats for autumn and spring data sets and for combined autumn and spring data sets. 2. Sites in the lowland sections of the western flowing rivers were characterized by low taxonomic richness and were distinct from the sites in the eastern part of the state. Sites on the western slopes of the Great Dividing Range in southern and northern NSW mostly fell into separate groups. In eastern NSW, site groups did not represent a north, central and south division. Sites on highland streams, coastal fringe streams and large rivers mostly formed distinct groups, but most of the sites on east-flowing rivers fell into large site groups that did not have clear geographic boundaries. 3. Environmental variables that were strongly correlated with ordinations of macroinvertebrate presence/absence at sites were water temperature, altitude, longitude and maximum distance from source. The predictor variables determined by DFA for the six models created included alkalinity, altitude, location (longitude and/or latitude), stream size and substratum composition. These are generally in common with the variables determined for other large geographic areas in Australia and the United Kingdom. 4. Model outputs from reference sites suggest that, among the six models, the riffle model combining autumn and spring is likely to give the most reliable predictions. The combined edge model also performed well but refinements are needed for single season models to provide reliable outputs. 5. Combined season models both for riffles and for edges detected biological impairment at all but one of the test sites. Single season riffle models also detected impairment while single season edge models characterized sites as unimpaired despite other models’ indications of impaired fauna. Riffle models may be more sensitive than edge models but the sampling of riffles is often limited by flow. Edge habitats are available at most sites but there may be few riffles in floodplain rivers. Available resources, desired model sensitivity, and river type should be considered jointly to determine the most useful habitat to sample.     

Water and habitat quality assessment in the Honi and Naro Moru rivers,Kenya, using benthic macroinvertebrate assemblages and qualitative habitat scores

An assessment of water and habitat quality, based on macroinvertebrate assemblage indices and qualitative habitat scores (QHS), was undertaken in the Honi and Naro Moru rivers, Kenya, in 2011. The two rivers are important as water sources for the local communities and as habitat for organisms such as invertebrates in the national parks there. The Naro Moru upstream site (QHS: 83%) is unmodified, with minimal human influence. The Honi downstream site and the Naro Moru midstream and downstream sites experienced moderate to large modifications in habitat and biota (QHS: 40–80%). South African scoring system (SASS) scores ranged from 43 (Naro Moru downstream) to 165 (Honi upstream), and there was a decrease in SASS scores with distance downstream. Based on the multimetric index (MI), the Honi and Naro Moru upstream and midstream sites have good water quality (MI: 0.6–0.8), whereas the Honi midstream and downstream sites, and the Naro Moru downstream site, have moderate water quality (MI: 0.4–0.6). Human activities had a negative effect on water quality and habitats. Preventive and conservation measures should be taken in the usage of the Naro Moru and Honi rivers.     

The importance of physical habitat assessment for evaluating river health

1. Physical habitat is the living space of instream biota; it is a spatially and temporally dynamic entity determined by the interaction of the structural features of the channel and the hydrological regime. 2. This paper reviews the need for physical habitat assessment and the range of physical habitat assessment methods that have been developed in recent years. These methods are needed for assessing improvements made by fishery enhancement and river restoration procedures, and as an intrinsic element of setting environmental flows using instream flow methods. Consequently, the assessment methods must be able to evaluate physical habitat over a range of scales varying from the broad river segment scale (up to hundreds of kilometres) down to the microhabitat level (a few centimetres). 3. Rapid assessment methods involve reconnaissance level surveys (such as the habitat mapping approach) identifying, mapping and measuring key habitat features over long stretches of river in a relatively short space of time. More complex appraisals, such as the Physical Habitat Simulation System (PHABSIM), require more detailed information on microhabitat variations with flow. 4. Key research issues relating to physical habitat evaluation lie in deciding which levels of detail are appropriate for worthwhile yet cost-effective assessment, and in determining those features that are biologically important and hence can be considered habitat features rather than simple geomorphic features. 5. The development of new technologies particularly relating to survey methods should help improve the speed and level of detail attainable by physical habitat assessments. These methods will provide the necessary information required for the development of the two-and three-dimensional physical and hydraulic habitat models. 6. A better understanding of the ways in which the spatial and temporal dynamics of physical habitat determine stream health, and how these elements can be incorporated into assessment methods, remains a key research goal.     

Prediction and assessment of local stream habitat features using large-scale catchment characteristics

1. Knowledge of what a habitat should be like, in the absence of the effects of human activities, is fundamental to local stream habitat assessment. It has been suggested that stream habitats are influenced by large-scale catchment features. This study aimed to identify these relationships so that local-scale habitat features could be predicted from larger-scale characteristics.
2. Fifty-one reference sites from the Upper Murrumbidgee River catchment, south-eastern Australia, were classified on the basis of the local features of their stream habitat. Large-scale variables, namely catchment area, stream length, relief ratio, alkalinity, percentage of volcanic rocks, percentage of metasediments, dominant geology and dominant soil type, provided sufficient information for classifying 69% of reference sites into appropriate reference site groups.
3. A model created using these large-scale catchment variables was able to predict the local habitat features that were expected (E) to occur at a site in the absence of the effects of human activities. These were compared with observed (O) local habitat features to provide an observed-to-expected (O/E) ratio, an assessment score of the habitat at a site. The departure of this ratio from 1 enables identification of those sites that may be impacted. A list of habitat features that are expected at a site can provide targets for habitat restoration or enhancement.
4. For impacted sites, when habitat assessment from the habitat predictive model was compared with biological assessment from the Australian River Assessment System (AUSRIVAS) predictive model, it was possible to identify whether habitat degradation or water quality degradation was the cause of biological impairment. Such assessment may make it possible to identify rehabilitation goals relevant to the biota.     

Distribution and risk assessment of heavy metals in river surface sediments of middle reach of Xijiang River basin,China

Xijiang River is the main surface water source in Guangxi province, South China. This study was carried out to investigate the distribution and potential ecological risks of seven heavy metals (Cu, Pb, Zn, As, Cd, Ni, and Cr) in surface sediments in Xijiang River basin. The results illustrated that the average concentrations of Zn, Pb, Cd, Cu, As, Ni, and Cr were 483.9, 207.5, 13.35, 23.50, 312.1, 28.75, and 50.62 mg/kg, respectively. Among them, Zn, Pb, Cd, and As were the major heave metals with concentration exceeding Class 3 threshold value of Chinese national standard. The result also showed samples with high ecological risk were mainly located in the upstream of Xijiang River basin as Diaojiang River, Hongshui River, Jincheng River, and Dahuan River. Based on the pollution risk assessment, the area manifested composite pollution of heavy metals in the sediments, signifying As, Pb, and Cd as the dominant heavy metals, and there were high ecological risk in sediments for these metals. According to correlation matrix and factor analysis (FA), the seven heavy metals were divided into three types/classes, Cd, as and Zn attributed by anthropogenic sources, natural sources corresponds for Ni and Cr while both natural and anthropogenic sources were attributed to Cu.     

Management options for river conservation planning: condition and conservation re-visited

1. Systematic conservation planning is a process widely used in terrestrial and marine environments. A principal goal is to establish a network of protected areas representing the full variety of species or ecosystems. We suggest considering three key attributes of a catchment when planning for aquatic conservation: irreplaceability, condition and vulnerability. 2. Based on observed and modelled distributions of 367 invertebrates in the Australian state of Victoria, conservation value was measured by calculating an irreplaceability coefficient for 1854 subcatchments. Irreplaceability indicates the likelihood of any subcatchment being needed to achieve conservation targets. We estimated it with a bootstrapped heuristic reserve design algorithm, which included upstream–downstream connectivity rules. The selection metric within the algorithm was total summed rarity, corrected for protected area. 3. Condition was estimated using a stressor gradient approach in which two classes of geographical information system Layers were summarised using principal components analysis. The first class was disturbance measures such as nutrient and sediment budgets, salinisation and weed cover. The second class was land use layers, including classes of forestry, agricultural and urban use. The main gradient, explaining 56% of the variation, could be characterised as agricultural disturbance. Seventy‐five per cent of the study area was classified as disturbed. 4. Our definition of vulnerability was the likelihood of a catchment being exposed to a land use that degrades its condition. This was estimated by comparing land capability and current land use. If land was capable of supporting a land use that would have a more degrading effect on a river than its current tenure, it was classified vulnerable (66% of the study area). 79% of catchments contained more then 50% vulnerable land. 5. When integrating the three measures, two major groups of catchments requiring urgent conservation measures were identified. Seven per cent of catchments were highly irreplaceable, highly vulnerable but in degraded condition. These catchments were flagged for restoration. While most highly irreplaceable catchments in good condition were already protected, 2.5% of catchments in this category are on vulnerable land. These are priority areas for assigning river reserves.     

基于压力-状态-响应和物元可拓模型的城市河流健康评价

城市河流作为人类活动和自然过程相互作用强烈的区域,承受着人类资源开发利用和污染物排放的压力,但近些年来随着对河流健康的重视,针对城市河流实施了大量的生态治理措施。综合考虑人类正负面影响对河流健康状态的影响,进行河流健康状态的评价,对于城市河流的修复效果检验和管理保护具有重要意义。以南京市鼓楼区典型城市河流西北护城河为研究区,根据河流周边土地利用类型、物理形态差异及城市管网分布将其划分为6个河段,考虑人类修复措施对河流健康水平的影响,构建了基于压力-状态-响应(Pressure-State-Response,PSR)模型的城市河流健康评价指标体系,采用物元可拓模型确定了河段健康等级,并根据各等级综合关联度之间的距离判断河流健康水平的发展趋势。结果表明:压力、状态以及响应准则层的权重分别为0.458、0.311、0.231,压力指标为影响城市河流健康水平的主要因素;西北护城河6个河段的健康水平表现出较强的空间异质性,河段A-F的健康等级分别为中等、健康、亚健康、中等、亚病态和病态,流经公园绿地的河段健康水平明显高于流经居民住宅区的河段,河段B、C、D的健康水平有进一步提升的趋势,而河段A、E、F的健康状态则有进一步恶化的趋势,需要进行重点关注。     

生态风险评价研究进展

20多年来,生态风险评价研究经历了从环境风险到生态风险到区域生态风险评价的发展历程,风险源由单一风险源扩展到多风险源,风险受体由单一受体发展到多受体,评价范围由局地扩展到区域景观水平.区域生态风险评价就是大尺度上研究复杂环境背景下包含多风险源、多风险受体的综合风险研究.目前,区域生态风险评价的理论框架已经搭建起来,统计方法多采用相对评价法.区域生态风险评价未来的发展方向为继续加强实验和野外调查,进一步减小不确定性,逐步解决尺度推移问题.区域生态风险评价必须与经济、社会、文化相结合,才能充分发挥它在管理决策中的作用.     

流域生态系统补偿机制研究进展

生态补偿是近年来生态环境管理领域的一个新发展起来的方向和热点,尤其在我国,生态补偿受到学者和政府部门的高度关注,其研究和实践进展迅速。流域是完整的地理与生态系统区域,是实施生态保护和生态补偿的典型单元。从流域角度研究和实施生态系统保护,可以最好体现生态系统的完整性和生态要素的综合性。流域生态补偿机制研究是当前生态经济研究的前沿命题。系统梳理和全面总结了流域生态补偿研究的国内外进展与应用案例,总结了当前流域生态补偿研究存在的主客体界定、补偿原则、措施短效性等方面存在的主要问题,提炼概述了流域生态补偿研究的理论分析框架,并就流域生态补偿确定方法、补偿途径等关键问题进行了探讨。结合水权交易与水市场、流域社会化管理等问题,对流域生态补偿的未来研究趋势进行了展望。     

An ecological risk assessment for the impacts of offshore wind farms on birds in Australia

An ecological risk assessment, based on life-history and behavioural attributes of 273 bird taxa, was used to identify which of those taxa are at high risk from negative interactions with offshore wind farms in Australia. The marine area of Australia was divided by state/territory boundaries perpendicular to the coast into eight regions, with Western Australia further divided into north and south, and a Bass Strait region bounded by the Victoria coast and the north coast of Tasmania. These regions were subdivided into coastal, inshore and offshore sub-regions and a risk summary for all bird taxa occurring in each of these sub-regions produced. In coastal and inshore sub-regions of Bass Strait, South Australia and Tasmania, the species with the highest risk scores were Orange-bellied Parrot Neophema chrysogaster, Furneaux White-fronted Tern Sterna striata incerta, Swift Parrot Lathamus discolor, Shy Albatross Thalassarche cauta, Far Eastern Curlew Numenius madagascariensis and Anadyr Bar-tailed Godwit Limosa lapponica anadyrensis. In offshore sub-regions in southern Australia, the highest risk species were all albatrosses, comprising Northern Royal Diomedea sanfordi, Eastern Antipodean D. antipodensis antipodensis, Gibson's D. antipodensis gibsoni, Wandering D. exulans, Amsterdam D. amsterdamensis and Grey-headed Albatross T. chrysostoma. Compared to onshore installations, there are logistical challenges to quantifying the potential and realized impacts of offshore wind farms that require different approaches to data collection and analyses. The extensive development of offshore wind farms in the Northern Hemisphere provides examples of best and emerging approaches to quantify and mitigate negative impacts of offshore wind farms that can be applied in an Australian context. Despite differences in the species involved, the same approaches to identifying high-risk species and to the monitoring and mitigation of negative impacts should be applied in a coordinated, regional-scale approach to the development of offshore wind farms in Australia.     

定量评价人类活动对净初级生产力的影响

以人类活动为主导的城市扩张和土地覆被变化对城市生态环境产生了重要影响,并与气候变化共同影响植被净初级生产力(NPP),但目前从时空尺度上脱离气候干扰仅以人类活动为主导因素来定量分析其对植被NPP影响的研究尚不充分.本研究以广州市为研究区,利用CASA模型估算2001—2013年实际净初级生产力(NPP_act),结合CHIKUGO模型估算得到的潜在净初级生产力(NPP_p)计算因土地覆被变化导致的NPP损失(NPP_lulc),并建立相对贡献指数(RCI)定量分析和评价在城市扩张过程中人类活动对NPP的影响.结果表明:2001—2013年间,广州总体及其5片区NPP_act和NPP_lulc分别呈减少和增加趋势,并存在明显的空间差异性;RCI呈明显增加趋势,东北片区RCI值最低,为0.31,表明气候变化是其NPP变化的主要原因,其他4个片区的RCI值均高于0.5,说明4个片区人为干扰严重,人类活动是其NPP减少的主导因素;广州市及其5片区的RCI变化斜率均大于0,人类活动对植被的干扰逐年增强,北部片区RCI变化斜率值最大(0.693),人为干扰增加趋势最明显.     

Synergistic impacts of sediment contamination and dam presence on river functioning

1. Dam presence is commonly associated with strong accumulation of polluted sediments. In spite of this context of multiple stressors, physical effects are often solely considered in the ecological assessment of the dam impacts. 2. We studied four ‘reservoir/downstream reach’ systems differing in levels of sediment contamination in reservoirs. Using assemblages and biotrait (i.e. ecological or biological attribute) responses of macroinvertebrate communities and leaf litter breakdown, we examined the individual effects and potential interactions between sediment contamination and dam presence along the gradient of ecotoxic pressure. 3. Leaf breakdown rates ranged from 0.0044° per day in the most contaminated reservoir to 0.0120° per day in the reference reservoir. Comparisons of community trait profiles among reservoirs highlighted a gradient of trait responses to sediment contamination. 4. In the absence of toxic contamination, the dam‐induced modifications in biotraits of invertebrate assemblages were not related to a reduction of leaf litter breakdown. Conversely, contaminated sediment in reservoir induced strong functional disturbances (i.e. bioecological shifts and reduction of leaf litter breakdown) downstream of dams. 5. Key biotrait categories positively related to leaf litter breakdown rate have been identified. They corresponded mainly to shredders and/or small‐sized (<0.5 cm) insects, using aquatic (e.g. crawlers) or aerial (e.g. fliers) active dispersal strategies. In addition, trait categories positively correlated to contamination level have been considered as ‘response’ traits. They corresponded to large‐sized (>4 cm) species, having several generations per year (polyvoltin), using asexual reproduction and/or disseminating by drift (aquatic, passive). 6. In the current context of ecological continuity restoration, this study has identified the risks associated with the presence of historical contamination in the run‐of‐river reservoirs for downstream ecosystem health.     

着生藻类和浮游藻类在三峡库区河流健康评价中的适宜性比较研究

藻类对水体环境变化敏感,其种类和数量与环境因素有密切联系并因环境的变化而发生变化,因此藻类常作为河流健康评价的指示生物。水体中的藻类根据生活习性不同分为着生藻类和浮游藻类,在河流健康评价中,以往的工作中有的采用浮游藻类用于河流健康评价,有的采用着生藻类用于评价,但浮游藻类和着生藻类究竟何者用于河流健康评价更适宜,抑或是二者在用于评价的适宜性上没有明显差别,迄今为止未开展过深入研究。选择三峡库区内的两条河流嘉陵江和乌江作为研究对象,于2015年9月,在两条河流上共布设11个研究断面,对嘉陵江、乌江的水环境理化因子、着生藻类和浮游藻类群落进行调查研究,应用着生藻类生物完整性指数(Periphytic algal index of biological integrity,Pe-IBI)和浮游藻类生物完整性指数(Phytoplankton index of biological integrity,Ph-IBI),并结合水体综合污染指数(Comprehensive pollution index,CPI),对嘉陵江、乌江的健康状况进行评价。研究结果表明,采用着生藻类生物完整性评价(Pe-IB...     

河流生态系统健康研究现状与展望——基于文献计量研究

河流生态系统健康是生态系统服务供给和流域可持续发展的基础,亟需从其内涵、影响、评价等方面进行系统归纳。运用文献计量梳理国内外文献,归纳了河流生态系统健康在河流自身、人类需求、管理目标3个方面的内涵;并从人类活动、土地利用、河流生境、水质、水量、气候变化等几个方面归纳了影响河流生态系统健康的主要因素和机理;明确了现有的河流生态系统健康评价方法,包括指示生物法、综合指标法、数学模型法等,总结了它们的优缺点和适用范围。最后,从河流生态系统健康的概念内涵、评价指标和水陆耦合等方面提出了存在的问题,建议进行流域整体的河流生态系统健康评价、跨区域的综合评价对比、多学科评价指标、河流廊道等几个方面的深入研究。