Effects of elevated water temperature on fish and macroinvertebrate communities below small dams

Many studies have investigated the ecological changes that occur below dams that release cold, hypolimnetic water, but very few studies have looked at the effects of the release of warm, surface waters. The effect of small, surface release dams on downstream thermal regimes is a major habitat concern for many cold‐water systems, however. The objective of this study was to examine the effects of summer temperature increases due to impoundment on downstream fish and macroinvertebrate communities in cold‐water streams. We sampled fish, macroinvertebrates and habitat upstream and downstream of dams on ten rivers during the summers of 1998 and 1999. Changes in mean summer temperature downstream varied from a cooling of 1 °C to an increase of more than 5 °C. Increasing temperatures downstream coincided with lower densities of several cold‐water fish species, specifically brown trout (Salmo trutta), brook trout (Salvelinus fontinalis) and slimy sculpin (Cottus cognatus) while overall fish species richness increased downstream. Density of mottled sculpin (Cottus bairdi), another cold‐water species, was not related to temperature changes below the dams. Macroinvertebrates showed shifts in community composition below dams that increased temperature. This study provides information useful for determining the extent of impact of these small, surface release dams, which are abundant across the country. Copyright © 2003 John Wiley & Sons, Ltd.     

小水电的生态与环境问题及对策

随着我国小水电建设规模日益加大，开发速度不断加快，小水电的生态与环境问题日益凸现，引起了社会的广泛关注。小水电有哪些生态与环境的效益和损害？与大中型水电项目有哪些区别？如何应对小水电的生态与环境问题？根据多年从事小水电开发和环境管理的经验，对这些问题提出了对策设想。     

Predicted impacts of proposed hydroelectric facilities on fish migration routes upstream from the Pantanal wetland (Brazil)

There are 104 hydroelectric facilities proposed to be installed in the watersheds that feed the Pantanal, a vast floodplain wetland located mostly in Brazil. The Pantanal is host to 23 long‐distance migratory fish species that ascend upland tributaries to spawn. A Geographic Information System was used to predict the impact of hydroelectric dams on potential migration routes for these species. Both anthropogenic (hydroelectric dams) and natural barriers were included in the analysis. Natural barriers were identified by river slope. Critical river slopes of 10 and 25%, above which fish were predicted to be incapable of ascending, were modeled as natural barriers. Based on this model, we show that between 2 and 14% of rivers in the Pantanal watershed are naturally blocked to fish migration. An additional 5 to 9% of rivers are currently blocked due to 35 existing hydroelectric facilities. If all proposed dams are built, the area flooded by new reservoirs will triple and the river kilometers blocked will double, blocking 25 to 32% of the river system to fish migration. The Taquari and Cuiabá River sub‐basins will be the most impacted, each having more than 70% of their rivers blocked. The impact of individual proposed facilities on the loss of migration routes is related to their proximity to existing barriers. Fourteen of the proposed dams are upstream from existing barriers and will therefore not further restrict long‐distance fish migration routes while proposed dams are predicted to close an additional 11,000 to 12,000 km of river channels.     

径流引水式小水电生态-发电协同优化模型及应用

以湟水河流域的湟乐水电站为例,基于自然水流范式计算河道内适宜生态流量和生态基流,以生态流量为主要约束建立径流引水式小水电生态-发电协同优化模型,利用NSGA-Ⅱ算法得到引水发电流量的Pareto解,研究成果对指导径流引水式小水电的生态调度和运行管理具有重要指导价值。结果表明：滑动t检验法诊断西宁水文站年径流量时间序列的突变点是2000年,经还原后得到1956—2000年多年平均天然径流量为41.3 m³/s;适宜生态流量在年内枯水期、平水期和丰水期展布的同期比分别是0.60、0.41和0.42,达到了“极好”标准;以传统Tennant法“一般”标准确定的非汛期生态基流为4.13 m³/s、汛期生态基流为12.4 m³/s;采用生态-发电协同优化模型计算多年平均来水条件下湟乐水电站的年发电量为634.29×10⁴ kW·h,枢纽下泄流量均满足减水河段生态流量需求;多年来水条件下湟乐水电站等效减排6 323.9 t CO₂,电站的减排生态效益为188.45×10⁴     

水利水电工程对鱼类的影响及保护措施

主要介绍水利水电工程建设对鱼类产卵、鱼类栖息地、鱼类洄游、鱼类区系等的影响,及水利水电工程导致的下泄水温、气体过饱和对鱼类的影响,同时介绍过鱼设施、人工增殖放流等保护措施;阐述水电工程对鱼类产卵的影响,提出根据不同鱼类的洄游时间、产卵和孵化条件要求,因时因地选取不同的引水方式组合,如底层取水、表层取水、中下层组合取水、...     

横断山区水电开发对鱼类资源多维影响及其保护措施研究进展

横断山区水系发达,河流众多,岭谷高差悬殊,复杂的地质环境造就了鱼类物种的多样性,同时丰富的水能资源形成了目前我国最大的水电能源基地。近年来,梯级电站密集建设改变了该区域水流、水温、水质、水域空间等多方面生态水文条件,对当地鱼类种群资源造成深远影响。本文基于横断山区水电开发及鱼类资源的现状,系统归纳了水电开发引起的生态水文要素变化和鱼类栖息过程受到胁迫的内在关系,回顾了国内外研究者在鱼类资源保护各个角度上提出的研究方法和应对措施,并提出了下一阶段研究的重点和具体方向。研究可为梯级水电开发下的鱼类资源保护提供理论支撑。     

汶川地震后震区水电站险情排查及应急处置工作概述

对汶川地震后震区水电站受损情况做了简要介绍,对震区水电站采取的险情排查、特种检查和应急处置工作做了进一步阐述,作者建议认真总结这次抗震救灾中水电站排险的经验教训,结合在后恢复重建.建立科学的水能开发和管理模式.     

The impacts of dams on local livelihoods: a study of the Bui Hydroelectric Project in Ghana

The construction of the Bui Dam was expected to boost socio-economic development in Ghana. This article examines the impacts of the project on the livelihoods of the local people. Data were collected using a mixed-research approach and a case-study design. The study finds that, while there have been significant improvements with respect to resettlement and compensation issues as compared to the earlier dam projects in Ghana, there are still some shortfalls. It is recommended that agriculture be improved by providing extension services and inputs to improve food security and the economic status of the local people.     

Linking flow alteration with fish assemblage structure in a river regulated by a small hydropower project in the Western Ghats of Karnataka,India

Small hydropower projects (SHPs) are promoted as low-impact alternatives for large hydropower. SHPs are generally commissioned on small- to medium-sized mountainous rivers, often in biodiverse regions, with backing in the form of subsidies, facultative policies and exemption from impact assessments as they are considered ‘green’. However, the ecological impacts of SHPs are understudied especially in highly seasonal tropical streams of Western Ghats of India, a global biodiversity hotspot and a distinct freshwater fish eco-region. We compared SHP-affected segments of a dammed and an undammed river in the Western Ghats of Karnataka, to assess how altered flow regime affects seasonal variability in habitat and water quality, and influences fish assemblage structure. We found that flow alteration by the SHP varied between different segments of the dammed river and with season. Furthermore, the nature of flow alteration influenced habitat variability, water quality and fish assemblage response in the dammed river. We observed that the dewatered segment of the dammed river experienced a lotic to lentic shift in habitat and water quality, which favoured fish species with eurytopic affinities. Fluctuating flows in the downstream segment subdued natural variability in flow regime and created novel habitats and water-quality conditions, affecting fish assemblages. The upstream segment of the dammed river retained natural variability in habitat and water quality, but did not mimic the undammed river in terms of fish composition. We also observed potential constraints on recruitment for migratory species of fish in the dammed river. Based on our results, we suggest how the placement of dewatered segment, and timing the closure of SHP operation in dry season based on ecological thresholds are potential solutions to mitigate the impacts of the SHPs. Furthermore, we recommend effective impact assessments, and adaptive management with active interventions to maintain genetic and ecological connectivity, as key to enhance the sustainability of the SHPs.     

Adverse ecological effects of small hydropower stations in the Czech Republic: 1. Bypass plants

Adverse effects of 23 bypass- or mill stream-type small hydropower stations (SHPSs) have been studied by traditional benthological and ichthyological techniques. Four locations, if available, were distinguished for each SHPS: the natural flow sections (NFS) above and below the SHPS area, the mill stream or diversion channel bringing water to the turbine, and the reduced discharge section (RDS) of the former stream course. Most SHPSs took a high percentage of the stream discharge (turbine intake capacity was usually bigger than average yearly discharge of the stream at a given point). Despite this, the decrease in the stream-wetted area was relatively low (usually 0–30%). The changes of benthic communities did not show any distinct trend explicable by the SHPS operation. Mechanical damage of fish by turbines was found rather rarely with SHPSs. The diverting weir (which usually distributes the discharge between the RDS and the mill stream), in combination with the abstraction of water for SHPSs, was an important migration barrier for resident fish in 30% of SHPSs. Water abstraction causes succession from large-bodied fish species (adult brown trout, chub, dace, grayling, etc.) towards small-bodied fish (trout fry, minnow, bullhead, stone loach, gudgeon). Average individual weight and fish biomass decreased four times in RDSs. Fish biomass losses exhibit significant negative relationships to the ratio of turbine intake capacity and stream discharge. Several mitigation measures are suggested. © 1997 John Wiley & Sons, Ltd.     

浅谈广西小水电的生存与发展

论述小水电在地方经济发展中的地位和作用，指出广西一些小水电发展中存在的问题，提出今后小水电发展的建议。     

小水电梯级开发河段地貌单元识别与异质性分析

河流地貌单元的科学分类与识别有利于准确定位水生生物栖息地,为科学评估小水电生态影响、开展受损河流生境修复提供依据。本文根据长江一级支流大宁河1972—2016年水文数据,利用累积距平、滑动T检验、IHA-RVA等方法确定了2个水文突变点,并分析对比了变异前、变异阶段Ⅰ和变异阶段Ⅱ3个不同阶段的水文改变程度;在归纳前人分类体系的基础上,依据水文改变程度较低时段下的实地调研观测数据,结合地貌单元过程-形式关系,确定了研究区域自上游至下游R1—R8河段地貌单元的类型及其空间分布,并引入地貌单元丰富度指数(R)、密度指数(D)和多样性指数(H_d)3个指标对研究河段地貌异质性进行了定量评价。结果表明,与变异前相比,变异阶段Ⅰ、变异阶段Ⅱ各月份水文改变度的平均值为15.53%、24.42%;R1—R4(小水电梯级开发河段)的R、D、H_d的平均值均小于R5—R8(较为自然段),分别相差9%、32.1%、17.2%,小水电梯级开发河段的地貌异质性有待提高。该研究定量评价了河段的地貌异质性,可从河流地貌角度为小水电分类整改工作提供决策支持。     

岳西县小水电站碳交易潜力分析研究

为了研究山区小水电站碳减排能力,以安徽省岳西县 132 座小水电站为研究对象,计算分析了全县小水电站碳减排能力和碳交易潜力,提出了通过集体成立碳交易管理公司等形式,积极纳入碳交易市场,增值创收,探索山区小水电新出路。     

调压室对水电站输水系统小波动过渡过程的影响

为了减小水电站输水系统过渡过程中产生的水锤压力,常常会在输水系统中设置调压室。通过基于不考虑水体弹性的理论推导以及考虑水体弹性的数值模拟,对无调压室及有调压室两种方案下输水系统小波动的过渡过程进行比较分析,以便较为全面地对设置调压室或不设置调压室是否会对水电站输水系统小波动的过渡过程产生影响展开研究。研究结果表明：在相同布置条件下,无调压室及有调压室两种方案的输水系统的小波动过渡过程均是稳定的;设置有调压室的输水系统小波动的过渡过程要优于未设置调压室的输水系统小波动的过渡过程。从研究结果来看,设置调压室对水电站输水系统的小波动过渡过程具有改善作用。     

大渡河干流水电开发中鱼类保护对策及建议

基于大渡河干流梯级环境影响报告书、鱼类栖息地保护规划等资料,系统地梳理了不同时期主要梯级水电站建设采取的主要鱼类保护措施,并结合流域鱼类、珍稀保护鱼类分布格局,从流域水生态系统整体保护角度出发,分析了干流梯级水电站鱼类保护措施存在的主要不足,提出了需要优化水生态系统保护措施、统筹考虑鱼类增殖放流的种类和规模及建立流域层面水生态系统保护模式等对策和建议。本研究对于促进流域水生态系统保护具有重要的借鉴作用。     

Cumulative effects of dams on migratory fishes across the conterminous United States: Regional patterns in fish responses to river network fragmentation

Globally, dams fragment river networks, threatening migratory fishes which require access to distinct habitats to complete their life cycles. Efforts to understand how cumulative effects of multiple dams affect migratory fishes across large regions, such as a country or continent, could help to identify locations for connectivity-enhancing actions to conserve migratory fishes. To address this, we evaluated cumulative effects of dams on migratory fishes in rivers across nine ecoregions of the conterminous USA. First, using fish data from thousands of sites (N = 45,989), we summarized ecoregional patterns in assemblages, quantifying the number of migratory species comprising assemblages, showing the prominence of potamodromous species across the large region as well as differences in migratory life history traits among ecoregions. Next, we compared the importance of a set of river network fragmentation metrics that captured influences of multiple dams in networks versus other anthropogenic landscape stressors and natural landscape factors that impact migratory fishes by ecoregion. We found that migratory fishes were more sensitive to cumulative dam effects than other stressors including urbanization and agriculture in the eastern USA. To further identify specific effects of environmental variables on potamodromous fishes, we conducted Boosted Regression Trees analysis in the eastern ecoregions. Our results suggested that the key natural influences on river fishes included catchment area as well as river baseflow and air temperature, suggesting that migratory fishes may be affected by changing climate. Additionally, we found that downstream dams were more influential than other human stressors to potamodromous fishes, underscoring the importance of enhancing connectivity within river networks to conserve migratory fishes. Collectively, our results provide new insights in identifying threats to migratory fish species across the USA, providing information that can aid in conserving this vulnerable but ecologically and socioeconomically important group of fishes.     

Bringing back ecological flows: migratory fish,hydropower and legal maladaptivity in the governance of Finnish rivers

ABSTRACT

Historically, Finnish rivers supported vital populations of migratory salmonids. Presently, these species are more or less endangered due to extensive damming and hydropower production. In this article, we study the main legal and scientific drivers for re-evaluating some of the existing hydropower operations in Finland. We argue that there is a need for re-evaluation on the basis of legal obligations stemming largely from EU law and new scientific knowledge. Theoretically, our setting opens up a classical adaptive governance problem in how to address laws and past decisions that are based on outdated assumptions about the functioning of social-ecological systems.     

Effects of dams in river networks on fish assemblages in non‐impoundment sections of rivers in Michigan and Wisconsin,USA

Regional assessment of cumulative impacts of dams on riverine fish assemblages provides resource managers essential information for dam operation, potential dam removal, river health assessment and overall ecosystem management. Such an assessment is challenging because characteristics of fish assemblages are not only affected by dams, but also influenced by natural variation and human‐induced modification (in addition to dams) in thermal and flow regimes, physicochemical habitats and biological assemblages. This study evaluated the impacts of dams on river fish assemblages in the non‐impoundment sections of rivers in the states of Michigan and Wisconsin using multiple fish assemblage indicators and multiple approaches to distinguish the influences of dams from those of other natural and human‐induced factors. We found that environmental factors that influence fish assemblages in addition to dams should be incorporated when evaluating regional effects of dams on fish assemblages. Without considering such co‐influential factors, the evaluation is inadequate and potentially misleading. The role of dams alone in determining fish assemblages at a regional spatial scale is relatively small (explained less than 20% of variance) compared with the other environmental factors, such as river size, flow and thermal regimes and land uses jointly. However, our results do demonstrate that downstream and upstream dams can substantially modify fish assemblages in the non‐impoundment sections of rivers. After excluding river size and land‐use influences, our results clearly demonstrate that dams have significant impacts on fish biotic‐integrity and habitat‐and‐social‐preference indicators. The influences of the upstream dams, downstream dams, distance to dams, and dam density differ among the fish indicators, which have different implications for maintaining river biotic integrity, protecting biodiversity and managing fisheries. Copyright © 2010 John Wiley & Sons, Ltd.     

Technologies for the study of hydropeaking impacts on fish populations: Applications,advantages, outcomes,and future developments

Dam construction and streamflow regulation are increasing throughout the world, with impacts in impounded aquatic ecosystems. Hydropower dams, some of them causing a phenomenon called “hydropeaking” during their operation, are known for having a variety of impacts on downstream aquatic biota, particularly fish, and respective habitat. This can result in significant changes, from the community (e.g., fish assemblage structure) to the individual level (e.g., physiological and behavioural adjustments). Researchers and managers involved in the assessment of hydropeaking impacts must be resourceful and use methods that allow their precise evaluation, from large to fine-scale habitat and biological responses. In the last decades, technological advances allowed for the development of techniques and instrumentations that are increasingly being used in hydropeaking impact and mitigation assessments. This paper aims to provide a review, to researchers and managers interested in this field, of some of the most innovative methods and techniques, involving technology, that are available to study hydropeaking effects on downstream ecosystem, particularly from a fish perspective. We discuss the fundamentals behind such techniques, their advantages, and disadvantages, while also providing practical examples of their application and of the type of results that can be obtained. We finish by discussing some of the shortcomings of these methods and how related technology can evolve to solve current limitations.