拆坝对河流生态环境影响利弊研究综述

为研究拆坝对生态环境影响的利弊,介绍了拆坝对水文情势、泥沙输运、河道地貌、河道水质、栖息地质量及生物多样性等生态的影响,综述了拆坝后河道物理化学及重要生态特性之间响应关系的研究进展。拆坝对生态环境的影响具有时空复杂性,且各生态因子相互影响;水文情势的变化是所有生态响应的触发条件,泥沙输运是生态响应的关键性因子。为了河道长期连续性的开发与利用,研究泥沙输运及泥沙污染物的释放规律,预测拆坝后河道水质时空变化过程,分析流域尺度上生态系统之间的响应关系等对拆坝的评估决策十分重要。     

山区河流修复中生态地貌设计与实践

河流生境是河流生物和物理环境的自然联系,直接或间接影响着河流生态系统动态,地貌修复在河流生境中具有极为重要的地位。对湖北香溪河流域兴山县古夫河段,以河流地貌重构为核心,河流水文连通性、河道栖息地的多样化、河流水质等方面为目的进行了生态修复;在修复区采取了多种工程措施(阶梯生态堰、浅滩、深潭、心滩、边滩等);通过数值模拟和现场监测,对研究河段的生境、水文、水质指标进行了分析。结果显示:生态修复后河道景观多样性指数显著提高;流速多样性增加,跌水后的流速增加为原来的1.6倍,而深潭区的流速则相对减小,形成了不同的流场类型;河道平均过水面积显著提高,为原来的2.6倍,提高了河流的联通性;河道溶解氧含量提升效果明显,尤其是实施了工程措施的位置,跌水上下游溶解氧分别为87.9%和95.6%,河流水质明显提高,河流生境的改善为生物物种的恢复提供了条件。     

退役坝拆除现状及其影响研究进展综述

我国降等与报废水库逐年增加,大坝退役拆除成为必然趋势。针对退役坝拆除问题,从各国拆坝数量、拆坝地区分布、拆坝原因和拆坝相关政策入手,对国内外大坝拆除现状进行分析总结,并对拆坝后对生态环境和社会经济产生的影响进行综述。研究发现国内外关于拆坝影响研究多为定性分析,缺少定量分析和一套切实可行的计算方法,且多为单因素研究,缺乏综合影响因素评估分析。由此展望未来的拆坝影响研究中应由定性分析向定量分析转变,并耦合水动力、泥沙、生物响应、水生环境等多方面因素,构建拆坝影响的综合评估体系。     

三峡库区水环境保护与生态修复初步研究

分析三峡工程对库区水环境和水生态的影响,主要有:库内水温分层、水污染及富营养化问题、泥沙淤积以及对陆生生态和水生生态的影响。提出加强库区城镇污水处理、控制城镇发展和农村面源污染、排污口综合整治、水华控制,加强水质监测与管理等水环境保护措施;陆生生态与生物多样性保护,水域生境保护与修复,珍稀、特有物种资源保护,水库生态调度和建立自然保护区(点)等水生态保护与修复措施。     

水库排沙对下游河流鱼类影响研究进展

水库排沙对减轻水库淤积、延长水库寿命和恢复河流泥沙连续性等方面有着重要意义,但是水库进行水力排沙时水库下游河流水体的物理和化学性质的变化可能对鱼类等水生生物产生不利影响,严重时出现死鱼现象.国内外水库排沙时期下游河道含沙量及其颗粒级配、溶解氧浓度、污染物等水质变化对鱼类影响研究表明,微颗粒泥沙淤堵鱼鳃影响其摄入氧气功能和水体溶解氧下降是影响鱼类的两个主要因素,且含沙量及其持续时间、颗粒级配等对鱼类影响机理不同.最后展望了我国今后水库排沙对下游河流鱼类研究内容.     

三门峡水库运行方式对库区湿地生态系统影响研究

在河流上大规模筑坝拦截河流水量。是河流生态环境受人为影响最显著、最广泛、最严重的事件之一，是河流生态系统研究的热点问题。本文通过对三门峡库区湿地生态系统的水文、物种、水质等因素的调查和分析，研究水库运行水位变化对湿地生态系统的影响．为恢复和维持河流生态系统健康提供依据。研究发现，降低运行水位，库区水环境状况有进一步恶化的可能，对库区供水水质安全和下游黄河水质安全有不利影响；低水位运行时。库区湿地面积大幅度减少，库区湿地保护区生态需水补给受阻，湿地生境状况出现不利变化。部分湿地将丧失原有的生态功能；库区栖息地环境发生变化，直接影响珍稀物种的生存。鉴于生态问题的复杂性．需要对三门峡运行水位的生态效应进行长期、全面研究，促进对水利工程造成的生态问题的认识．以便采取有效的控制措施和对策。     

北运河生态健康快速评价研究

为进一步探究现阶段北运河健康现状,采用北运河河流快速评价方法和SPSS多元统计方法中相关性分析,对北运河山区和平原段河流健康进行评价,结果表明:河流快速评价方法可操作性强、便捷高效,在本研究中基本能够简洁、准确地反映北运河健康状况,适合专业、非专业人员对城市河流生态健康评价的早期快速判断,具有一定的推广应用价值;SPSS相关性统计结果显示北运河健康指数(RHI)与河流快速评价体系中一级指标生物、物理化学、水文地貌指标显著相关(P0.01),与二级指标中植被、河道、物理、化学指标显著相关(P0.01),表明该快速评价指标体系能很好地识别北运河表征河流健康的影响因子;北运河属于亚健康河流,表现出山区河流生态等级较高、平原河流生态等级较低的特征,山区河流后期生态修复指标应以水量、水质及生物多样性等为主,平原河流生态修复指标多考虑水生指示性物种、水质、植被及景观。该研究可为流域河道管理部门提供参考。     

基于分布式水文模型的水库生态调度方案 修正研究——以双峰寺水库为例

结合下游生态环境用水要求,使用分布式水文模型模拟双峰寺水库调度前后坝址下游的水文循环过程,指出了规划阶段水库调度存在的生态问题,进而修正调度方案并分析采用生态调度修正方案后对武烈河下游水文情势及坝址下游河流生态环境需水的影响。模拟结果表明：在修正后的水库生态调度方案下,双峰寺水库建成运行后,库区段流速从库尾至坝前断面不断减小;水库下泄流量大于坝址处多年平均流量的10%。而且,水库建成后防洪能力提高;75%保证率年份和特枯年份均可保证地下水位。     

基于和谐理念水库调度方式的研究

现行水库调度方式对河流健康的环境影响主要有:改变河道形态、拦水拦沙影响上游与河口环境、阻隔河流系统的空间联系、影响流域陆地水文条件、库岸滑塌、影响地下水和流域的水质、改变流态影响水温和加剧污染等。对河流健康的生态影响主要有:减少流域生态物种、威胁河口湿地上的生态物种、阻隔鱼类洄游路线、影响水生物的生命周期等。提出了和谐理念水库调度措施:实施水位优化调度、分层分段泄水保障水质、结合防洪适时适量泄水改善库内水质、分层放水以消除水库下游水温异常、人造小洪峰以满足下游生物繁衍需求等。     

中小河流河道治理及生态修复措施分析

北方地区大部分中小河流在中上游兴建水库后,对下游河道产生河道萎缩、干化、植被退化等影响,另外河道内存在违建、排污、非法挖采等乱象,河流生态遭受严重破坏。以太谷县为例,70年代大兴水利建设,修建水库。水库下游河道存在堵塞、萎缩、无尾、无序排倒、挖采等问题。文中探索采用河道疏浚连通、新型护岸等措施修复河流生态,实现河道生态环境的可持续发展,有效制止生态环境的持续恶化,平衡河流开发与保护,构建河流生态新格局。     

PHYSICAL AND PLANT COMMUNITY CONTROLS ON NITROGEN AND PHOSPHORUS LEACHING FROM IMPOUNDED RIVERINE WETLANDS FOLLOWING DAM REMOVAL

Dam removal has emerged as a critical issue in water resources engineering and management. Of particular concern in many regions of the USA is the effect of dam removal on downstream water quality and potential methods of decreasing sediment and nutrient loading to downstream reaches. Rapid revegetation of reservoir sediments has been suggested as a means of reducing the impact of dam removal, although little data exist about the role of vegetation in controlling the downstream release of sediment or nutrients. This study investigated an impounded riverine wetland complex on the Little River, North Carolina, before and after the removal of a low‐head dam. We quantified the leaching of interstitial nitrogen (N) and phosphorus (P) to the adjacent river channel during reservoir dewatering and, through experimental manipulations, isolated the difference between physical (soil) and biological (plant) controls on N and P leaching from dewatering impoundment sediments. We found that the rate and the quantity of N and P leaching from impounded dewatering sediment are predominately controlled by sediment porosity and specific yield. Although vegetation controls on N and P leaching were statistically significant during the first growing season following dam removal, vegetation is likely to be more important as a long‐term control on sediment and nutrient loads. Our results suggest that the initial release of N and P from a dewatered reservoir will be difficult to control but that vegetation may play an important long‐term role. Copyright © 2011 John Wiley & Sons, Ltd.     

水库运行对下游河道水环境影响的一维-二维耦合水环境模型

以广西漓江为实例,建立了全河流一维和局部河段二维水环境模型,并通过实际观测数据对模型的参数进行了率定。该模型耦合了水动力学过程及生态学过程,可对水库运行造成的河道水流条件的改变给下游的水生态系统造成的影响进行定量评价。其中的一维模型分析全河段水环境变化趋势,二维模型分析关键区间水环境的特点,并为后续的生物栖息地模型的应用奠定基础。分析了典型水文年中自然径流和青狮潭水库调水两种运行模式下下游河道关键水环境因子的变化。模拟结果表明水库运行在平水年的影响大于丰水年和枯水年,局部浅水区的变化大于深水区,年内枯水期(10—12月)的影响大于年均值,而且这些变化沿程逐渐减弱。     

河流水电开发对生态环境的影响及其对策研究

河流水电开发在缓解水资源和电能短缺问题的同时,对库区及其下游的生态环境也带来了一些负面效应.这些影响主要体现在:(1)工程施工恶化周边生态环境;(2)水库蓄水导致库区生态变迁;(3)引水式电站改变坝下缺水段生境特征;(4)河流水沙变化破坏下游河道及河口区的水-盐、水-沙平衡.针对水电开发所带来的这些问题,提出了几条应对措施,以弱化其负面影响.这些措施包括:(1)进行流域开发规划,重视水电开发规划的环境影响评价工作;(2)优化工程设计,预防或减少水土流失;(3)加强工程环境监理,明确环境管理职责;(4)加强水电建设项目的生态化;(5)优化水库运行管理,减轻生态冲击.     

Physical and Biological Responses to an Alternative Removal Strategy of a Moderate‐sized Dam in Washington,USA

Dam removal is an increasingly practised river restoration technique, and ecological responses vary with watershed, dam and reservoir properties, and removal strategies. Moderate‐sized dams, like Hemlock Dam (7.9 m tall and 56 m wide), are large enough that removal effects could be significant, but small enough that mitigation may be possible through a modified dam removal strategy. The removal of Hemlock Dam in Washington State, USA, was designed to limit channel erosion and improve fish passage and habitat by excavating stored fine sediment and reconstructing a channel in the former 6‐ha reservoir. Prior to dam removal, summer daily water temperatures downstream from the dam increased and remained warm long into the night. Afterwards, a more natural diel temperature regime was restored, although daily maximum temperatures remained high. A short‐lived turbidity pulse occurred soon after re‐watering of the channel, but was otherwise similar to background levels. Substrate shifted from sand to gravel–cobble in the former reservoir and from boulder to gravel–cobble downstream of the dam. Initially, macroinvertebrate assemblage richness and abundance was low in the project area, but within 2 years, post‐removal reaches upstream and downstream of the dam had diverse and abundant communities. The excavation of stored sediment and channel restoration as part of the dam removal strategy restored river continuity and improved benthic habitat while minimizing downstream sedimentation. This study provides a comparison of ecological effects with other dam removal strategies and can inform expectations of response time and magnitude. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.     

拆坝对河流生态系统的影响及评估方法综述

为研究拆坝对河流生态系统造成的影响,从短期和长期两个时间尺度综合分析了河流水文情势、地形地貌、岸边带植物、鱼类和底栖动物等关键生态因子对拆坝的响应,并总结了目前拆坝对生态系统影响的两种主要评估方法。认为根据实际拆坝情况进行评估和基于数值模型进行预测两种评估方法中,实地观测是最直接、最有说服力的研究方法,但受成本和一些不可控因素限制;数值模拟具有速度快、费用低、无比尺影响等优点,可对拆坝影响进行预测,为管理者提供参考,但精度和准确性有待提高。指出后续研究中应综合考虑拆坝过程中各生态因子间的耦合效应,需对不同拆坝时机和分阶段拆坝方式对河流生态系统的影响进行深入研究。     

Low-head dam removal increases functional diversity of stream fish assemblages

Despite the growing number of dam removals, few have been studied to understand their impacts on stream fish communities. An even smaller proportion of dam removal studies focus on the impacts of low-head dam removals, although they are the most common type of dam. Instead, the majority of removal studies focus on the impacts of larger dams. In this study, two previously impounded Illinois Rivers were monitored to assess the impacts of low-head dam removal on the functional assemblage of stream fishes. Study sites were sampled each fall from 2012–2015 (pre-dam removal) and 2018–2020 (post-dam removal) in three locations: the tailrace, impoundment, and river channel. Fishes were aggregated into habitat and reproductive guilds, relating community changes to habitat, environmental metrics, and stream quality. Prior to removal, the slackwater guild was the most prevalent habitat guild throughout both rivers, while nest builders and benthic spawners were the most abundant reproductive guilds. During the two years following removal, fish assemblage throughout both rivers shifted to a more evenly distributed representation of habitat and reproductive guilds, while restoration of lotic habitat conditions increased, as surface water temperatures decreased and QHEI, IBI, and dissolved oxygen increased. This shift in environmental metrics and increase in overall stream quality increased, particularly in the formerly impounded reaches, indicate diminished habitat homogeneity, and a shift towards natural habitat diversity. This habitat diversification likely led to the restoration of a range of potential niches, thereby increasing the array of guild types inhabiting these rivers, while simultaneously preventing single-guild dominance.     

水库溃坝洪水数值模拟及下游风险评价

以锦屏二级水库为例,利用DAMBRK和一维水动力模型模拟多种组合工况下水库溃坝和洪水演进过程,并对计算得到的溃口流量及下游洪水演进结果进行分析。根据溃坝洪水模型计算获得的水库下游地区洪水淹没情况,综合考虑洪水的危险性、暴露性和易损性,利用模糊综合评价法对水库下游8个重要乡镇进行了洪水风险评价,评价结果可以为该流域进行安全应急预案制定、洪水灾害风险管理等提供技术参考。     

河流保护与生态修复

分析了堤防和水坝对河流造成的负面影响:切断了河流横向和纵向的生态联系,造成水文循环短路和绝缘,河流被台阶化、节点化,从而破坏了水滨生物栖息地和水生生态系统。从河流保护概念性范围出发,分析了河流在横向、纵向、垂向以及时间维度上的水文循环和生态联系。指出恢复河流生态系统的根本思想在于推动和恢复河流在空间和时间的4维尺度上的水文循环和生态联系,避免河流水文循环短路或绝缘。总结了国内外关于河流生态修复的措施,即在河流横向营造生物栖息地、湿地、林地、深潭和浅滩等,在河流纵向补偿流量和洪水过程,重建生物栖息地和水库消落带,闸坝处建造鱼道和鱼梯等。