The effect of an irrigation and hydroelectric reservoir on its downstream communities

The Cernadilla reservoir, located on the River Tera (northwest Spain, Duero Basin) is an oligotrophic reservoir with a capacity of more than 250 × 10⁶m³ and a depth of 70 m. The regulated flow pattern is characterized by higher summer flows, higher day flows than night ones, and lower weekend flows. The effects of this artificial flow regime on the stream ecosystem were evaluated by comparing the aquatic communities of an upstream station with those of three downstream stations, located at 1, 8, and 24 km from the dam. Physiocochemical characteristics of the water, fish and macrobenthic communities, and macrophytes were studied at each station. Summer water temperatures were significantly lower downstream of the reservoir. Macrophyte biomass, macrobenthic diversity, and richness were reduced below the dam. The trophic structure was changed by an increase of shredders and grazers. Fishery total biomass greatly fluctuated seasonally, but was higher above the reservoir than below it. However, in spring the trout populations were higher upstream because large numbers of spawning cyprinids from the reservoir invaded upstream reaches of the River Tera and displayed resident trout populations.     

Downstream effects of a new hydropower impoundment on macrophyte,macroinvertebrate and fish communities

The downstream effects of Valparaíso Reservoir (Río Tera, north-western Spain) on macrophyte, macroinvertebrate and fish communities are examined by comparing their respective structures before (1986) and after (1990-1991) the creation of this hydropower impoundment. A single sampling station was selected 2.4 km below the dam. Macrophytes significantly (p < 0.05) decreased their total biomass, although the species composition remained dominated by two species (Myriophyllum verticillatum and Ranunculus fluitans). The macroinvertebrate community, on the other hand, exhibited a significant (p < 0.05) decrease in taxonomic richness, total density and total biomass. In general, planarians, ephemer-opterans, coleopterans, plecopterans and trichopterans disappeared or decreased their abundances. Scrapers (as relative biomass) were the functional feeding group most adversely affected by the new flow regulation. With regard to the fish community, the most significant change was the absence of all resident coarse fishes (cyprinids, primarily) at the sampling site during the 1990 and 1991 sampling surveys. Conversely, salmonids (Salmo trutta) persisted; the trout population was dominated by individuals of the 0+ age group (? 1 year old) both before and after the construction of Valparaíso Dam. It is concluded that short-term flow fluctuations induced by hydroelectric power generation were the main factor causing the observed adverse effects. In this respect, some management measures to minimize these effects are recommended.     

闹得海水库库区及下游河道的变化

多沙河流上的滞洪水库，能强烈改变水流泥沙过程、水沙搭配关系，将大水泥沙转化为小水泥沙，淤坏河槽，改变泥沙淤积部位，改变河道特性。     

Impact of flood alleviation schemes on aquatic macrophytes

Geomorphological, engineering and ecological surveys were carried out at 18 flood alleviation schemes in the UK to evaluate their environmental performance. As no pre-scheme river corridor surveys had been carried out at any of the sites to enable the environmental impact to be directly assessed, controls were established in natural sections adjacent to five of the engineered reaches. A space–time substitution enables the pre-scheme conditions to be estimated for comparison with the engineered reach. The physical characteristics of the channel at bankfull conditions exert a strong influence on plant community composition. Paired assessments were carried out for engineered/control reaches on five rivers and this revealed which species and habitats were most affected by various engineering treatments. The general conclusion was that dredging, widening and straightening rivers reduces the number of desirable species, whereas two-stage channels and schemes involving the construction of flood banks at the edge of the meander belt maintained the richness and preserved and enhanced the occurrence of key species. Data from every cross-section, engineered and control reaches, enabled a model to be developed relating species occurrence to physical habitat features. This can be used to predict, at the stage of appraisal or design of a project, the likely response of the river to any particular engineering works. Given information on the existing condition in the river, it enables the environmental impact of the scheme, in terms of its effect on river bed plant species, to be assessed.     

碧流河水库下游洪水淹没损失计算

针对缺乏实测流量资料的水库下游河道,利用二维河网模型系统MIKE21,采用多种工况组合,模拟计算并分析了碧流河水库下游流域在拟定历史洪水条件下的淹没情况及经济损失.建模过程考虑水库调度与潮位等因素的影响;使用水库下游流域最新DEM数据与遥感数据,参考设计资料,并结合计算经验综合确定计算模型参数.     

漓江枯水期水库补水对下游水环境的影响

通过建立漓江流域水环境模型,模拟了青狮潭水库补水及非补水模式下,枯水期其下游河道内水环境变化情况。研究结果表明,与非补水模式相比,枯水期补水模式导致水库下游河道的水环境发生较大变化。从时间上看,青狮潭水库补水模式使得下游河道水位升高,水面扩大、流速增大,河道内水温增加,溶解氧浓度有所下降。对水环境影响较为强烈的时段为每年的10—12月,其中平水年的影响大于丰水年及枯水年;从空间上看,青狮潭水库补水模式对下游水环境的作用沿程逐渐减弱,但在影响较强的10—12月间,研究区域内的河道水环境很难通过自身恢复到原有状态。     

水库调度对大坝下游河道生态径流的影响

采用逐月频率计算法,分别计算水库修建前后河道生态径流,并对其变化情况进行比较,确定水库调度是否符合河道生态径流的要求。根据襄阳站水文资料对丹江口水库的调度进行分析,结果表明:丹江口水库目前的调度方式对汉江流域生态系统的影响比较大,提出了减小丹江口水库调度对汉江生态系统影响的措施:为减少这种影响,应以建坝前的最大、最小和适宜生态径流过程为准,对现有的调度规程进行适当修改,使以后运行的最小生态径流不小于建坝前的最小生态径流,最大生态径流不大于建坝前的最大生态径流过程,减小水库对生态系统的影响。     

旭龙水电站苏洼龙－穷得库段库岸稳定分析

苏洼龙－穷得库段位于金沙江旭龙水电站库尾一带,其地质条件极为复杂,25 km长的库段发育了大量洪积、冲积、崩坡积、冰积、滑坡体等第四系库岸,其库岸稳定性直接影响整个库区以及水库正常运行。通过对该段库岸各段的地质条件以及稳定性进行分析总结,得出库岸稳定性的影响因素,以此为水库区综合评价及正常蓄水位的选择提供地质参考。     

察尔森水库坝下建设区景观设计与构建

本文以水利部察尔森水库为例,根据景观生态学及景观构造分析方法,从环境教育与游乐休憩相结合,人与自 然的和谐共处的角度,对水库坝下游建筑区的景观生态类型进行了重新设计和构建。创造出近自然绿色景观空间格局。     

水库运行对下游岸边带植被和鱼类的影响

本研究选取了漓江下游的一段复式河道为例,建立了一维全河流和二维局部河段的水环境模型,并与基于元胞自动机的岸边带植被模型和基于个体的鱼类模型耦合,从岸边带植被变化和鱼类种群动态角度研究水库运行对河流水生态系统的作用。研究以优势种植物水蓼、刺果酸模和益母草为对象,模拟了自然条件和水库调节作用下三种植物空间格局的演变,并选取草鱼和鲫鱼为研究对象,研究水库运行对鱼类生长和分布的影响。通过模拟结果的对比分析,发现水库运行有利于益母草的生长与扩张,而不利于水蓼的生长,水位波动对水蓼生长以及维持岸边植物多样性有正面作用。此外,假设仅考虑水库运行造成的下游水流变化的作用,枯水期水库向河道补水对草鱼有一定的正面影响,对鲫鱼有轻微的负面影响;而在在4-5月,水库运行对两种鱼类都存在比较明显的负面影响。本文建立的模型方法可为河流优化管理及水库生态友好运行提供支持。     

龙背湾水电站超大型水库放空阀设计

现有技术设计的放空阀存在流量小、耐压低等诸多问题,难以作为龙背湾水库的主要放空设施。本文提供了一种能应用于各种大中型水库的大口径、耐中压的超大型水库放空阀的设计方案——直径3.0 m、耐压1.6 MPa的超大型水库放空阀,经过龙背湾水电站工程的使用,证明其具有结构简单,使用方便,适用范围广的特点。     

东江水库调节对其下游各级水库淹没的影响

河流梯级开发中，上游有龙头水库时，对下游调节作用较大。如湖南省东江水库系一大型多年调节水库，调节系数为１．３。考虑利用该库空闲库容容纳洪水，减少下泄流量，与区间洪水组合后，下游各梯级设计洪水在洪水标准低于３０年一遇时，其值比原设计小，相应回水降低，淹没损失减少，以东江下游乔口－遥田７个梯级为例，其中乔口，石面担，程江口，永兴，上堡等５梯级减少的淹没损失是原各梯级淹没损失的７８．７２％，经济效益显著     

大伙房水库下游河道非恒定流的特性分析

本文介绍了水库下游河道非恒定流试验的内容及对试验资料的规律分析方法,探讨了河道非恒定流的特性,并提出了计算放水波传播速度及径流过程的公式。     

River, reservoir and lake sediment contamination by heavy metals downstream from urban areas of Switzerland

This paper quantifies sediment contamination by heavy metals in four reservoirs and one lake located downstream from major urban areas in Switzerland. The waterbodies include the Wettingen Reservoir (located on the Limmat River downstream from Zürich), the Klingnau Reservoir (on the lower Aare River), the Wohlen Reservoir (downstream from Berne), the Verbois Reservoir (downstream from Geneva) and Vidy Bay (Lake Geneva, city of Lausanne). For all sediment cores and contaminants, a trend is observed from high contaminant values in the lower part of the cores, decreasing to lower concentrations in the upper part of the cores. However, for each site and each element, specific features are recognized. Applying the criteria of the Swiss ordinance on soil protection, all sediment cores must be classified as contaminated by one or more contaminants and at variable levels. From these data, it is concluded that: reservoirs and lakes located downstream from major urban centres in Switzerland have accumulated significant volumes of contaminated sediments in the past, representing the largest, but not the most intensely, contaminated sites on a national scale; the main environmental risk is remobilization of the contaminants and their return to the food chain, particularly by infiltration into the groundwater; and although the processes of remobilization are identified, the conditions of occurrence and the amplitude of the processes are still poorly known. Different options of reservoir and lake sediment management also are discussed and further research topics defined.     

某水库渗漏对下游温泉群的影响评价

某水电站建成蓄水后,库水是否会沿着断层F1向下游产生渗漏,从而改变顺断层发育温泉群的水量、水温和水质等要素成为制约工程建设的关键问题。有鉴于此,通过对温泉所处地区的区域地质条件、水化学及同位素特征的分析,阐明了温泉群的成因模式。在此基础上,采用地质分析与数值模拟相结合的方法,从定性和定量两个方面评价了库水渗漏对温泉的影响。结果表明:温泉群属上升泉,其形成与区域地下水的深循环有关,这一循环系统相对独立,只是在泉水上升排泄过程中,与浅层地下水发生了混合;水电站建成后,温泉仍会正常排泄;库水沿断层的渗漏对温泉群的水量、水温和水质基本无影响。     

Environmental issues of the three gorges project,China

This paper reviews several issues relating to the potential environmental impacts of a planned high dam at Three Gorges on the main course of the Changjiang (Yangtze River).     

索风营水电站库区左岸河间地块喀斯特渗漏勘察技术

喀斯特渗漏勘察是喀斯特地区水利水电工程建设项目勘测设计的重要内容,成果评价将对工程产生重大影响甚至制约到工程成立与否.文中以索风营水电站水库左岸河间地块的喀斯特水文地质勘察为实例,对有关勘察工作的技术路线、勘察技术、喀斯特水库渗漏评价方法及处理思路作相应的探讨.     

上游小水库溃坝对下游水库的影响

根据溃坝时间长短,溃坝的类型可分为瞬时溃坝和逐渐溃坝;根据溃坝缺口规模大小,可分为全部溃坝和足部溃坝.本文以瞬间全溃为例计算溃坝洪水及其对下游水库的影响.     

干旱区平原水库渗流及下游土壤盐渍化分析

为预测平原水库蓄水对下游生态环境的影响,在非饱和土力学理论的基础上,利用ABAQUS有限元软件模拟某大型平原水库蓄水后坝体坝基的稳定渗流形态,得到大坝下游的地下水埋藏深度,对比地下水临界深度,判断是否会出现土壤盐渍化现象。计算结果表明：①水库蓄水水位越高,渗流速度就越快,相应水库下游土壤盐渍化的范围也越广。②水库渗漏补充下游地下水,抬高地下水水位随着时间的推移最终会达到稳定状态,此时由水库蓄水引起的土壤盐渍化的程度和范围都达到极限。根据实际工程监测数据与本文计算结果中相对应部分的对比,证明所采用的方法基本可靠,可为平原水库周边土壤盐渍化的防治提供依据。