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三峡水库运行后长江中游洪、枯水位变化特征 总被引：3，自引：2，他引：1
流域大型水库蓄水后,坝下游河道调整过程中的洪、枯水位变化,对下游水安全、水生态和水资源利用影响甚大.利用1955-2012年长江中游各水文站水位、流量等资料,采用改进的时间序列分析方法,对三峡水库运行前后长江中游洪、枯水位变化特征进行了研究,结果表明:三峡水库蓄水前长江中游洪、枯水位变化的周期长度分别为9~14、11~15 a,在假设三峡水库运行后水位无趋势性变化的前提下,估算得到的水位变化周期长度基本在20 a以上,蓄水前的自然周期性已被打破,枯水位发生趋势性下降且无复归迹象,而洪水位波动周期虽有所延长,但上升幅度未超过历史波动变幅,仅可确定洪水位没有明显的下降趋势.三峡水库蓄水后坝下游长距离冲刷,枯水河槽冲刷量占平滩河槽的比例逐年增加,累计至2013年已达91.5%,是枯水位下降的主控因素.河槽冲刷导致的床沙粗化增加了河道床面阻力,高程在平滩水位附近的滩体上覆盖的大量植被增加了水流流动阻力,同时大量航道整治、护岸、码头等工程主体部分布设在枯水位以上,综合因素作用使得洪水河槽阻力增加.三峡水库蓄水后,虽然枯水期流量补偿作用显著削弱了枯水位下降的效应,但枯水位下降事实已经形成,不利于航道水深的提高及通江湖泊枯水期的水量存蓄,洪水位未明显下降,同级流量下的江湖槽蓄量不会明显调整. 相似文献
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三峡水库156m蓄水前后澎溪河回水区藻类多样性变化特征 总被引：3，自引：2，他引：1
为了解156 m蓄水前后三峡水库次级河流藻类多样性变化特征,对2007年7月至2008年1月澎溪河回水区的藻类种群结构的变化进行连续监测.基于三峡水库水位调度特点,将监测期划分为蓄水前、中、后三个时段,即7-9月、10月、11月至翌年1月,应用Shannon-Weaver多样性指数H’对藻类多样性进行评价,通过Connell中度扰动假说理论结合优势藻种探讨蓄水过程水动力变化及藻类多样性的变化特征.结果表明:2007年7-9月蓄水前H’均值为3.466±0.317,10月蓄水期则降为3.246±0.338,而11月蓄水后高水位阶段H’均值上升为3.431±0.352.蓄水前澎溪河回水区具有河流型特征,流量与降雨作为主要的物理扰动因子影响水体扰动强度,进而引起多样性变化.10月蓄水期间水位突升、流量骤降导致水体扰动强度加剧,较蓄水前藻类多样性下降.自11月蓄水后的高水位阶段,降雨较小、流量趋于稳定,水体扰动降低,多样性回升并维持在相对稳定的状态. 相似文献
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三峡水库举世瞩目,是长江保护与治理的关键性枢纽工程,水库自2003年蓄水运行后库区水沙条件均发生了显著改变,对库区水生态环境产生了深远影响。本文系统综述了三峡水库蓄水运行后库区的水流动力特性和泥沙淤积特性,总结了蓄水后水库的新水沙运动情况;从水库蓄水运行后水质参数特征,营养物质、重金属和典型有毒有机污染物的赋存特征等方面,分析了三峡水库库区新水沙变化条件下的水环境响应特征;基于水库蓄水前后浮游植物、底栖动物等重点生物群落的现存量和群落特征变化规律,探索了三峡水库新水沙变化条件下库区的水生态响应特征;最后对未来三峡水库运行下的水生态环境效应研究提出展望,本文可为三峡水库水生态环境保护科学研究和管理提供新的认识和决策参考。 相似文献
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三峡工程蓄水对洞庭湖水情的影响格局及其作用机制 总被引：13，自引：12，他引：1
三峡工程建成投入运行后,汛末蓄水将使坝下河湖水情发生变化,长江中下游秋季来水减少成为常态.为客观分析三峡蓄水对洞庭湖水情的影响分量、空间格局及其作用机制,选取三峡工程典型的蓄水过程,运用长江中游江湖耦合水动力学模型计算了因上游来水变化引起的洞庭湖水情时空变化.结果表明:1)三峡汛末蓄水对洞庭湖水位影响具有明显的"北高南低,东强西弱"的格局,即东洞庭湖最为显著、南洞庭湖东部和西洞庭湖北部次之,南洞庭湖西部和西洞庭湖南部最小.2)洲滩湿地受蓄水影响最明显的主要为东洞庭湖、南洞庭湖和湖泊洪道两侧的条带状洲滩.3)三峡蓄水对洞庭湖水位的影响机制有二:长江干流水位快速消落加速湖泊水体下泄以及削减长江三口分流补给湖泊的水量. 相似文献
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从2003年开始，中国三峡水库将进入蓄水期。到2009年，从长江中段起大约600km长的广阔区域内注水，三峡水库将蓄水40km^3。蓄水过程代表着地球物理学的“控制实验”为详细研究经典的正向／反向模拟地表荷载问题提供了独一无二的机会。尽管Wang(2000)研究了局部尺度的大荷载效应，但我们的目标是从数百千米向上游更长的空间尺度，重点在通过新近发射的GRACE卫星可检测到的随时间变化的重力信号。该卫星寿命期为5年(至2007年)，将跨越主要蓄水期。我们采用PREM弹性地球模型用格林函数法所得结果表明，大地水准面高度的年增加值在直到20阶球谐函数的尺度上都高于GRACE卫星的观测灵敏度，而5年周期的累积增加值则在直到50阶球谐函数的尺度上(相当于波长800km)都高于观测灵敏度。 相似文献
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[专稿]近年长江中下游径流节律变化、效应与修复对策 总被引：1，自引：0，他引：1
近十余年长江上游大量兴建大型水库,蓄水、调节和拦沙对中下游河川径流和泥沙产生了深刻影响.河川径流减少,径流季节提前,伏秋（特别是10月）流量显著降低、变差系数增大,97%严重干旱频率情景变成80%~85%.同时,宜昌和出海输沙量分别减少93%和70%,中下游河槽冲刷下降1~3 m,三峡蓄水后仅13年清水冲刷幅度和范围已超过三峡预期30年的冲刷上限,目前仍呈加速趋势.干流各站平均水位下降2~4 m,与此同时河道同流量洪水位反而升高.水库调节是水位降低的主要原因,河道冲刷更加剧水位降低,当前水位变化对防洪和生态都不利.汛后流量和干流水位提前降低使洞庭湖和鄱阳湖（两湖）提前干枯、松滋等"三口"入湖水量减少,伏秋高热季节两湖生态环境面貌发生了根本变化.汛后流量减少甚至显著增加长江大通十月流量小于15000 m3/s几率和上海长江水源受咸潮影响风险,10月咸潮入侵变成最严重时段必须引起高度重视.我们认为,径流和径流节律变化是当前长江生态环境最主要问题之一.建议以"水资源工程"重新定位上游大型工程、以"水资源优先"优化流域管理和切实回归既定三峡工程运行原则等统一调度和改善中下游水情;通过水库挖泥等措施修复长江物质通量,抑制中下游剧烈冲刷和稳定河流格局;加强中下游蓄滞洪区等防洪能力建设,为最大限度降低上游水库防洪和蓄水压力创造条件;主要通过改善上游水库调度维护两湖环境条件,"引清水入洞庭"和"增加供水设施建设"加强两湖适应能力.这是长江修复和保护重点. 相似文献
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洞悉长江洞庭湖汇流河段的水文关系及其变化规律对确保长江中下游的防洪安全至关重要.为了掌握汇流河段水文特征演变情况,本文结合汇流河段处监利、城陵矶、螺山等国家重要水文控制断面的近百年水文资料,通过M-K检验、Morlet小波分析等方法研究了该河段逐日水位、流量等水文数据,分析了汇流河段年内分配、年际变化、变化趋势、突变点及变化周期等水文特征,并探讨了具体成因.研究结果表明:①长江与洞庭湖汇流河段年最高水位一般出现在7月,年最低水位一般出现在1、2月;②汇流河段年径流量主要集中在59月,占年径流总量的63.64%~73.44%;③近50年城陵矶水位高、中、低水分别约抬升0.98、0.56、1.46 m;④近10年城陵矶与监利年径流比降至0.66.⑤在长江中下游水利开发历程中,经突变检验表明,下荆江裁弯取直和三峡蓄水175 m对江湖水文特征的影响较为明显.⑥城陵矶站和螺山站的年径流量、水位平均周期约为16 a,监利站的年径流量、水位平均周期约为8 a.⑦19542017年间,汇流比最大值一直在降低,其发生时间在逐渐提前.以上成果为深入研究流域复杂的江湖演变规律提供了科学参考. 相似文献
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三峡水库以及上游江段形成的河—库生态系统与长江中下游洞庭湖和鄱阳湖的江湖生态系统都是四大家鱼的重要栖息地,有相似性也有差异.2017年7—8月在三峡水库、洞庭湖和鄱阳湖利用地笼、虾笼、高网和迷魂阵采集草鱼和鲢幼鱼样本,观测耳石日轮,分析三峡水库和通江湖泊草鱼和鲢幼鱼的繁殖时间和早期生长特征及差异,探讨相应的保护措施.结果显示,三峡水库、洞庭湖和鄱阳湖采集草鱼幼鱼的孵化日期分别为4月24日—5月25日、5月21日—6月26日和5月4日—5月28日;鲢幼鱼的孵化日期分别为4月10日—6月12日、5月25日—6月19日和5月9日—6月12日.三峡水库、洞庭湖和鄱阳湖草鱼样本的体长增长率分别为1.04、1.84和1.64 mm/d,微耳石的沉积率分别为3.41、5.41和4.77μm/d;鲢幼鱼的体长增长率分别为1.10、2.87和1.96 mm/d,微耳石沉积率分别为2.96、7.17和4.57μm/d.洞庭湖草鱼和鲢的体长增长率和耳石沉积率均显著大于三峡水库;鄱阳湖鲢的体长增长率和耳石沉积率均显著大于三峡水库,而草鱼的体长增长率和耳石沉积率则与三峡水库没有显著差异.结果表明,三峡水库蓄水后长江中游干流草鱼和鲢的繁殖时间明显滞后;洞庭湖和鄱阳湖的草鱼和鲢幼鱼生长更快.目前,长江全面禁渔正在逐步实施,预期将对恢复鱼类资源起到重要的作用.除了全面禁渔之外,还建议保护和修复鱼类栖息地;减少江湖阻隔,灌江纳苗;增殖放流亲鱼;开展生态调度,促进鱼类繁殖. 相似文献
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Introduction During and before the construction of the Three Gorges Project, the annual observation was continuously undertaken by the Three Gorges gravity observation network established around the head area of the reservoir (the section between Sandouping and Badong). This network has pro-vided substantial high precise data related to seismic activity. However, the annual gravity survey together monitoring of the existed observation stations can hardly effective monitor some potential sei… 相似文献
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Large water‐sample sets collected from 1899 through 1902, 1907, and in the early 1950s allow comparisons of pre‐impoundment and post‐impoundment (1969 through 2008) nitrogen concentrations in the lower Missouri River. Although urban wastes were not large enough to detectably increase annual loads of total nitrogen at the beginning of the 20th century, carcass waste, stock‐yard manure, and untreated human wastes measurably increased ammonia and organic‐nitrogen concentrations during low flows. Average total‐nitrogen concentrations in both periods were about 2.5 mg/l, but much of the particulate‐organic nitrogen, which was the dominant form of nitrogen around 1900, has been replaced by nitrate. This change in speciation was caused by the nearly 80% decrease in suspended‐sediment concentrations that occurred after impoundment, modern agriculture, drainage of riparian wetlands, and sewage treatment. Nevertheless, bioavailable nitrogen has not been low enough to limit primary production in the Missouri River since the beginning of the 20th century. Nitrate concentrations have increased more rapidly from 2000 through 2008 (5 to 12% per year), thus increasing bioavailable nitrogen delivered to the Mississippi River and affecting Gulf Coast hypoxia. The increase in nitrate concentrations with distance downstream is much greater during the post‐impoundment period. If strategies to decrease total‐nitrogen loads focus on particulate N, substantial decreases will be difficult because particulate nitrogen is now only 23% of total nitrogen in the Missouri River. A strategy aimed at decreasing particulates also could further exacerbate land loss along the Gulf of Mexico, which has been sediment starved since Missouri River impoundment. In contrast, strategies or benchmarks aimed at decreasing nitrate loads could substantially decrease nitrogen loadings because nitrates now constitute over half of the Missouri's nitrogen input to the Mississippi. Ongoing restoration and creation of wetlands along the Missouri River could be part of such a nitrate‐reduction strategy. Published 2013. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
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Seismic analysis of the Xiluodu reservoir area and insights into the geometry of seismogenic faults 
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下载免费PDF全文 The Xiluodu (XLD) reservoir is the second largest reservoir in China and the largest in the Jinsha River basin. The occurrence of two M > 5 earthquakes after reservoir impoundment has aroused great interest among seismologists and plant operators. We comprehensively analyzed the seismicity of the XLD reservoir area using precise earthquake relocation results and focal mechanism solutions and found that the seismicity of this area was weak before impoundment. Following impoundment, earthquake activity increased significantly. The occurrence of M ≥ 3.5 earthquakes within five years of impoundment also appear to be closely related to rapid rises and falls in water level, though this correlation weakened after five years because earthquake activity was far from the reservoir area. Earthquakes in the XLD reservoir area are clustered; near the dam (Area A), small faults are intermittently distributed along the river, while Area B is composed of multiple NW-trending left-lateral strike-slip faults and a thrust fault and Area C is composed of a NW-trending left-lateral strike-slip main fault and a nearly EW-trending right-lateral strike-slip minor fault. The geometries of the deep and the shallow parts of the NW-trending fault differ. Under the action of the NW-trending background stress field, a series of NW-trending left-lateral strike-slip faults and NE-trending thrust faults in critical stress states were dislocated due to the stress caused by reservoir impoundment. The two largest earthquakes in the XLD reservoir area were tectonic earthquakes that were directly triggered by impoundment. 相似文献
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《Limnologica》2017
Environment conservation of the Three Gorges Reservoir (TGR) requires reliable assessment of fish resources and variation of their distribution. The goal of this study was to determine the best season and the diurnal period to estimate fish density in the TGR using acoustic surveys as a monitoring tool. To find out diurnal migration pattern of fishes in the TGR, we conducted reduplicated 24-h hydroacoustical surveys in the forequarter of the TGR, which covered different habitats (mainstream, tributary bay), seasons (summer, winter) and years (2012–2015). Measurements were performed using SIMRAD EY60 split beam echosounder with frequency 120 kHz. Additionally, zooplankton and environmental parameters were measured. The results showed more than ten times differences between the day and night fish density estimates, probably resulting either from the horizontal migrations between the littoral and open water or vertical migrations. Differences were higher during winter than during summer, and higher in the tributary bay than in the mainstream. Clear vertical migrations were observed both in the tributary bay (amplitude 15 m) and in the mainstream (amplitude 35 m), but only during winter time. Inter-annual estimates of fish density showed generally decreasing trend with years. especially well pronounced in the tributary bay. We also observed high seasonal and diurnal variability in fish distributions, which can significantly affect the accuracy and precision of biomass estimate, indicating importance of choosing appropriate timing for fish monitoring. According to our results, in order to receive the most reliable estimates of fish density in the TGR, hydroacoustic surveys should be performed during summer at night time. 相似文献
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三峡库区的入侵鱼类及库区蓄水对外来鱼类入侵的影响初探 总被引：2，自引：0，他引：2
三峡水库已于2010年10月完成175 m的蓄水目标,蓄水后三峡库区形成一个生态位严重空缺的人造湖泊生态系统.近年来,库区及长江上游外来入侵鱼类呈增长态势,已发现外来入侵鱼类23种,且部分已处于种群数量暴发阶段.水库蓄水初期营养盐输入增加和初级生产力的提高通常也利于广适性鱼类和外来种的生存,对外来鱼类的入侵和种群数量的扩散暴发产生一定的促进作用.外来鱼类在生态位竞争上与土著鱼类相比处于明显优势地位,可能将严重危害三峡库区的渔业资源及其水域生态系统的安全.因此,对于三峡库区的鱼类入侵及其所带来的相关效应等问题,应引起密切关注和重视,尽早建立三峡库区入侵鱼类的预警和防治体系,严格评估人为引种活动,深入研究外来鱼类得以成功入侵的原因与机理. 相似文献
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由于自然和人为因素的影响,三峡水库鱼类资源一直在发生变化,为掌握三峡水库蓄水后典型支流香溪河鱼类群落的现状及历史变化,于2020年7月—2021年4月使用多网目复合刺网和地笼对香溪河鱼类群落进行实地采样,并结合历史数据进行比较分析。研究期间共采集到鱼类55种,隶属于7目14科,鲤科鱼类种类数最多,以杂食性鱼类和湖泊定居性鱼类为主,优势种为贝氏?(Hemiculter bleekeri)、短颌鲚(Coilia bratchygnahus)、似鳊(Pseudobrama simoni)和翘嘴鲌(Culter alburnus),其相对重要性指数(IRI)分别为5502、3828、2567和1109。鱼类物种多样性指数在春季最高,夏季最低。刺网单位捕捞努力量渔获个体数和单位捕捞努力量渔获量在夏季最高,冬季最低。与三峡水库蓄水前相比,香溪河鱼类中长江上游特有鱼类减少4种,外来鱼类增加3种。湖泊定居性种类持续增加,喜流水性种类减少,鱼类优势种发生较大变动。2020—2021年香溪河鱼类组成与1987年的相似性指数为0.29,与2012—2013年的相似性指数为0.53,反映三峡水库蓄水前后香溪河... 相似文献