Displacement characteristics and prediction of Baishuihe landslide in the Three Gorges Reservoir

In order to reach the designated final water level of 175 m, there were three impoundment stages in the Three Gorges Reservoir, with water levels of 135 m, 156 m and 175 m. Baishuihe landslide in the Reservoir was chosen to analyze its displacement characteristics and displacement variability at the different stages. Based on monitoring data, the landslide displacement was mainly influenced by rainfall and drawdown of the reservoir water level. However, the magnitude of the rise and drawdown of the water level after the reservoir water level reached 175 m did not accelerate landslide displacement. The prediction of landslide displacement for active landslides is very important for landslide risk management. The time series of cumulative displacement was divided into a trend term and a periodic term using the Hodrick-Prescott(HP) filter method. The polynomial model was used to predict the trend term. The extreme learning machine(ELM) and least squares support vector machine(LS-SVM) were chosen to predict theperiodic term. In the prediction model for the periodic term, input variables based on the effects of rainfall and reservoir water level in landslide displacement were selected using grey relational analysis. Based on the results, the prediction precision of ELM is better than that of LS-SVM for predicting landslide displacement. The method for predicting landslide displacement could be applied by relevant authorities in making landslide emergency plans in the future.

Status of two Coreius species in the Three Gorges Reservoir,China

Dam construction alters natural flow regimes which,in turn,cause significant changes in fish communities during and after impoundment. The construction of the Three Gorges Reservoir,from impoundment of the Changjiang(Yangtze) River,China,may have affected native fish species. Thus,the status of two lotic freshwater fish species,Coreius heterodon and C.guichenoti,were monitored in the Three Gorges Reservoir,including fish abundance,individual composition,growth,condition,and mortality. Data on both species were gathered from upstream,midstream and downstream areas of the reservoir and,where available,from studies published before and after dam construction. Lower abundance,slower growth,a less diversified age structure,poorer fish condition(indicated by hepatosomatic index) and higher mortalities were recorded in sites nearest the dam compared with upstream areas. Furthermore,after final impoundment,individual Coreius species inhabiting the area changed,with young individuals becoming more abundant,while upstream of the reservoir the two Coreius species became smaller at a given age. The results show that the status of the two Coreius species was subject to dramatic changes after impoundment.

Tectonic environment and cause of earthquakes in the Three Gorges reservoir area

Seismotectonics in the Three Gorges reservoir area is investigated by using the P-wave tomography with earthquakes that occurred before the impoundment of the reservoir. The result indicates that most of these events occurred in or around the velocity-gradient belts between high-velocity and low-velocity anomalies. These belts have similar characteristics to buried-fauh zones. Stresses generated by movement of partially molten upper-mantle materials and thermal stress may have jointly contributed to the seismic activities along the faults and such buried faults, and possibly activated new earthquake ruptures.

The effect of large reservoirs impoundment to the spatial and temporal variations of regional crustal deformation in Hubei Province, China

The total capacity of Three Gorges Reservoir（TGR） and Danjiangkou Reservoir（DJR） is large and has significant seasonal fluctuations, which give rise to crustal instability. In this research, we focus on studying the temporal and spatial variation of crustal deformation in Hubei Province caused by reservoir impoundment of TGR and DJR.The Digital Elevation Model, historical hydrological information, GPS monitoring data and load-induced deformation model are combined to monitor the crustal deformation. The modeled results indicate that in the trapezoidal area between the TGR and DJR, the average vertical deformations at different latitudes have different variation tendencies. The vertical deformation modulus and fluctuation amplitude are larger at the latitude of 33 N/32.5 N from 2003 to 2006 and at the latitude of 31 N/32.5 N from 2008 to 2014, while the latter are much larger than the former. Moreover, from2008 to 2014, the frequency and the intensity of seismic activities are all enhanced significantly in this region. The modeled results at the GPS sites are consistent with the vertical displacement of GPS monitoring results in trends and the waveform. It can be inferred that the seasonal deformation is elastic. The horizontal deformation components have the same variation trends with that at each GPS monitoring station,which demonstrates that the whole region is moving toward the southeast. The spatial variation of crustal deformation demonstrates that the impoundment of TGR in2003 causes significant vertical displacements, with the maximum modulus of 32 mm downward located in Xiangjiang River＇s estuary. When the water storage increases, the maximum value will become larger, and the location will move toward the upstream.Besides, the earthquakes occurred more frequently in the region with maximum deformation modulus.

The analysis on reservoir sediment deposition and downstream river channel scouring after impoundment and operation of TGP

According to the measured data after impoundment and operation of the Three Gorges Reservoir,the reservoir sediment deposition and downstream river channel scouring are described briefly and compared with the research results achieved in the demonstration stage.It is indicated through analysis that the reservoir sediment deposition and downstream river channel scouring during 8-year impoundment and operation are still within the original forecast,so the original forecasting results are feasible.The further observation and comparison should be conducted because the comparison between the observed data and the original forecast is not so sufficient in time and the prototype observation and related research work should be strengthened in the future.

近62 a三峡地区区域性暴雨过程气候特征及长期变化规律

【目的】充分认识三峡地区区域暴雨过程的气候特征及长期变化规律对于科学防汛以及合理利用水资源具有重要意义。【方法】基于三峡地区33个国家级气象观测站1961—2022年逐日降水量资料和目前重庆市气候中心业务采用的区域性暴雨过程监测指标,对三峡地区区域性暴雨过程进行客观识别,并利用多种数理统计方法分析区域性暴雨过程的气候特征和长期变化规律。【结果】结果表明:(1)三峡地区近三分之二的暴雨以区域性过程形式出现,平均每年区域性暴雨过程有8.4次,主要出现在5—9月,尤以6—7月为集中发生时段。区域性暴雨过程首次开始日期多年平均为5月8日,末次结束日期为9月17日。平均每次过程的暴雨覆盖范围为8.6站,持续时间1.3 d,平均暴雨强度为74.7 mm/d。(2)三峡地区区域性暴雨过程年频次存在2~3 a和8 a左右的变化周期,年平均区域性暴雨过程覆盖范围存在4~6 a和8~11 a周期变化。(3)近62 a三峡地区区域性暴雨过程的首次开始日期显著提前,末次结束日期无明显变化,发生期显著变长;发生频次没有明显变化趋势、平均持续时间、平均覆盖范围、平均综合强度也均没有明显变化趋势,但平均暴雨强度呈增强趋势。(4)近62 a,三峡地区区域性暴雨过程的各项指标均未发生突变现象。【结论】研究成果为三峡地区防汛减灾、水资源管理以及回应三峡工程对局地气候影响的社会关切等提供科学支撑。

三峡库区蓄水前后夏季小时降水变化特征

利用国家气象信息中心小时降水资料,结合三峡库区地形的多样性,分析了库区蓄水前(1992—2002年)和蓄水后(2003—2021年)夏季(6—8月)小时降水时空变化以及不同类型强降水事件(HRE)变化特征。结果表明:蓄水后小时降水的降水量和频次减少,而强度增加;降水变化存在明显的地理分布规律,降水量、频次、强度在库区中北部增加,且多位于长江以北地区;降水量、频次在库区西南部减少,强度在库区中南部和西北部减弱,且多位于31°N以南。蓄水前后小时降水的日变化峰值时间位相的空间差异程度表现为降水强度>降水量>降水频次;蓄水后降水量、频次、强度呈增加趋势的站点增多,且降水量和强度的日变化峰值时间位相在高海拔山区具有位相前移特征。蓄水前后各等级小时降水的降水概率和降水占比变化不明显,其中降水概率在(0.1,0.5)mm等级最大,≥20 mm等级最小;降水占比在(1,5)mm等级最大,(0.1,0.5)mm等级最小,≥20 mm等级约为15%。蓄水后小时降水的日变化特征更加明显,其中≥20 mm等级的小时降水量和频次的双峰结构更为突出,其他等级的小时降水量和频次的峰值时间范围有扩大趋势,而各等级小时降水强度的次日尺度波动更频繁。蓄水前后HRE均是短历时型最多,长历时型最少,且短历时型HRE多开始于下午,中历时型和长历时型HRE多开始于夜间;蓄水后有利于HRE维持,短历时型HRE在中午和下午开始的概率增加,中历时型和长历时型HRE在清晨开始的概率增加。

基于谈判博弈的三峡梯级蓄水期多目标调度

汛后蓄水期是三峡梯级防洪向兴利调度转换的重要时间窗口,不合理的蓄水调度将对梯级防洪、发电兴利、生态效益造成不利影响。本文以发电量最大、防洪库容占用比最小以及修正流量偏差最小作为三峡梯级蓄水期调度目标构建优化调度模型,进而引入谈判博弈模型将各个调度目标作为不同谈判主体,通过逐步缩减各调度目标期望效益值进行多轮谈判,最终得到纳什均衡调度方案。实例计算表明,应用谈判博弈模型能够求解得出三峡梯级蓄水期不同调度主体的最优蓄水调度方案,同时该蓄水调度方案也能够达到其他调度主体期望效益值,被其他目标主体所接受。研究成果可为三峡梯级多目标调度决策提供新的思路。

Monthly change of community structure of zoobenthos in Xiangxi Bay after impoundment of the Three Gorges Reservoir,China

Xiangxi Bay,a typical bay of the Three Gorges Reservoir(TGR)in China,was formed in June 2003 after the impoundment of the TGR.We investigated the community structure of zoobenthos in Xiangxi Bay from August 2003 to August 2004.Benthic abundance and biomass were calculated per unit area of sediment.A total of 26 taxa were identified.They included two families of Lamellibranchia(7.7%of the total taxa number),two families of Oligochaeta(50%),Chironomidae(38.5%),and one other animal(3.8%).The average density and biomass were 276 ind./m2 and 0.301 g/m2,respectively.Oligochaetes and chironomids constituted the major groups,and Limnodrilus hoffmeisteri,Procladius sp.,Branchiura sowerbyi,Tubificidae sp1.and Polypedilum scalaenum group sp.were the common taxa in this reservoir system.Among them,L.hoffmeisteri and Procladius sp.were the dominant species,and contributed 37.0%and 28.3%of the total density,respectively.The standing crop of zoobenthos in Xiangxi Bay was relative low,compared with other similar reservoirs.Our studies demonstrate that the standing crop increased gradually with time.The total density and biomass in August 2004 were 8.8 and 14.3 times those of the initial impoundment,separately.Oligochaetes did not become the sole dominant group,indicating that the sediment loading in Xiangxi Bay may be not serious.

考虑碳减排的水库多目标提前蓄水调度研究

针对当前的水库提前蓄水调度研究尚未考虑碳减排问题,本文基于水库碳排放和有机碳埋藏因子法,构建了考虑碳减排的水库提前蓄水调度模型,采用基于熵权重的逼近理想解排序法(TOPSIS)对提前蓄水调度方案进行了多目标评价,以优选调度方案,在三峡水库开展了实例研究。研究结果表明:三峡水库从9月1日起蓄,于9月30日逐步蓄至167 m的调度方案最优,相较于原设计方案,在不增加防洪风险的前提下,多年平均发电量增加29.91亿kW·h(8.80%),弃水量减少26.03亿m^(3)(27.51%),碳排放量减少69.26亿g(3.94%),有机碳埋藏量增加1.93亿g(1.28%),温室气体的CO_(2)碳当量减少235.48亿g(3.85%),提前蓄水方案可显著提升三峡水库发电量、供水保障能力和减少碳排放量。本研究为水库提前蓄水的水碳协同调度提供了技术支撑。

高洪水期运行水位对三峡水库泥沙淤积的影响

三峡水库泥沙问题直接关系到水库库容的长效保持。选取典型高洪水期,基于数值模型探究入库水沙量级、水沙异步及运行水位对三峡库区沙峰输移和淤积排沙的影响。结果表明:入库洪峰的增大抑制了涪陵沙峰比的衰减,并导致更多泥沙输运至坝前,使得坝前沙峰降幅受运行水位的抬升更为显著;变动回水区较常年回水区更易受到入库水沙异步影响,且随着来沙系数的增大,由低水位抬升时淤积占比更高;水库排沙比受入库水沙异步影响有限,且随着入库洪峰、沙峰的增大,排沙比增加的同时对运行水位抬升导致的衰减更为敏感。研究成果初步揭示了入库水沙异步及运行水位对库区沙峰运动与淤积的影响,可为三峡水库汛期优化沙峰排沙调度提供参考。

三峡库区航道维护性疏浚技术方案分析

针对175 m试验性蓄水初期泥沙淤积碍航问题,结合实测水文、河道地形资料、2010—2022年度三峡库区航道维护性疏浚方案,对三峡库区近十年来的航道条件变化、滩险碍航成因及疏浚技术进行全面分析。结果表明:通过适当增加挖槽水深、“疏堵”结合等方法,可利于卵石输移、保持航道稳定,疏浚效果显著。在疏浚时机方面,有效结合三峡水库调度及疏浚滩险特点,合理安排施工时机,既提高施工效率,又可缓解施工与通航矛盾。

Influence of the impounding process of the Three Gorges Reservoir up to water level 172.5m on water eutrophication in the Xiangxi Bay

The water level of the Three Gorges Reservoir(TGR) rose to 172.5 m in two stages from September to November,2008.The hydrodynamic parameters and water quality parameters(e.g.flow velocity,temperature,turbidity and nutrient content) had been continuously monitored to reveal the influence of the impounding process of the TGR on the water eutrophication in the Xiangxi Bay(XXB).The maximal daily rise of the water level of the TGR was about 2.38 m.The water exchange between the mainstream(the Changjiang River) and the XXB of the TGR was enhanced by density current,and its main characteristics were a density-stratified flow in different directions.The water exchange reduced the differences of the water quality parameters(for example,temperature,turbidity,nutrient level,pH,etc.) between the mainstream and the XXB during the impounding process.Meanwhile,the water stability index in the mainstream remained small but it was lowered in the XXB.The main causes included the dilution by water of lower concentration of the chlorophyll a(Chl.a) entering from the mainstream,the decline of the water stability,and the increase of suspended silt,which induced the Chl.a to decrease in the XXB during the impounding process.The grade of the water eutrophication changed from middle eutrophic level to mesotrophic state in the process.However,as available nutrients were imported into the XXB from the mainstream during the impounding process the risk of water eutrophication increases in the XXB in the future.

Distribution and sources of polycyclic aromatic hydrocarbons and phthalic acid esters in water and surface sediment from the Three Gorges Reservoir

After the impoundment of the Three Gorges Reservoir（TGR）, the hydrological situation of the reservoir has changed greatly. The concentration and distribution of typical persistent organic pollutants in water and sediment have also changed accordingly. In this study, the concentration, distribution and potential sources of 16 polycyclic aromatic hydrocarbons（PAHs） and 6 phthalic acid esters（PAEs） during the water drawdown and impoundment periods were investigated in water and sediment from the TGR. According to our results, PAHs and PAEs showed temporal and spatial variations. The mean ΣPAH and ΣPAE concentrations in water and sediment were both higher during the water impoundment period than during the water drawdown period. The water samples from the main stream showed larger ΣPAH concentration fluctuations than those from tributaries. Both the PAH and PAE concentrations meet the Chinese national water environmental quality standard（GB 3838-2002）. PAH monomers with 2–3 rings and 4 rings were dominant in water, and 4-ring and 5–6-ring PAHs were dominant in sediment. Di-n-butyl phthalate（DBP） and di-2-ethylhexyl phthalate（DEHP）were the dominant PAE pollutants in the TGR. DBP and DEHP had the highest concentrations in water and sediment, respectively. The main source of PAHs in water from the TGR was petroleum and emissions from coal and biomass combustion, whereas the main sources of PAHs in sediments included coal and biomass combustion, petroleum, and petroleum combustion. The main source of PAEs in water was domestic waste, and the plastics and heavy chemical industries were the main sources of PAEs in sediment.

华西秋雨与梅雨对三峡水库蓄水调度影响分析

长江中下游梅雨和上游华西秋雨分别发生于三峡水库主汛期前、后两个时期,是判断洪水遭遇与蓄水时机的重要依据。分析了梅雨和秋雨的时空分布特征、三峡水库7 d和15 d洪量系列的汛期分期及其对汛末蓄水的影响。结果表明:长江中下游梅雨发生在三峡水库主汛期前,长江上游华西秋雨最早8月21日开始;梅雨最晚8月8日结束,出梅后,长江中下游防洪压力减轻,三峡水库可提前释放城陵矶防洪库容;三峡水库8月29日进入后汛期,洪水量级适中,可考虑提前蓄水以充分利用秋汛洪水资源。综合梅雨、秋雨和三峡汛期分期的关键时间节点,在确保防洪安全的前提下,建议三峡水库自8月8日起实行汛期运行水位动态控制和提前蓄水调度。

基于流固耦合理论的巴东黄土坡滑坡地震响应研究

为研究三峡蓄水对湖北巴东黄土坡滑坡地震稳定性的影响,基于流固耦合理论建立二维有限差分数值模型。在计算无水(蓄水前)及有水(175 m实验性蓄水)条件下滑坡体场地地震动、应力响应及孔隙水压力差异特征的基础上,进一步给出滑坡体安全系数时程,探讨在蓄水与水库地震共同作用下的滑坡体稳定性及成因机理。结果表明:1)无水条件下滑坡体上硬层与下硬层的地震动峰值加速度放大系数约为1.33及3.31,具有显著的场地放大效应及软弱夹层消能减震作用;2)瞬时地震荷载下,由于滑坡体上下硬层之间非协调性变形与非快速排水的共同作用,软弱层超孔隙水压力快速形成,并呈现出阶段性积累上升趋势,伴有瞬时放大特征。

三峡水库香溪河鱼类群落结构特征及历史变化

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鱼类群落结构差异明显。建议加强河流自然生境修复、保护土著鱼类并严格防控外来鱼类,以促进鱼类资源多样性恢复,维护水域生态系统稳定。

基于蓄能指标的梯级水电站蓄水调度研究

优化梯级水电站汛末蓄水调度可提高流域水资源利用效率。现有基于水库水量占比的蓄满率评价指标,未考虑梯级水电站间的水力和电力联系,难以有效表征蓄水效益。为此,提出了一种基于蓄能的梯级水电站蓄水效益评价指标,以梯级水电站蓄水期发电量与期末蓄能最大为目标函数,构建了梯级水电站蓄水优化调度模型,采用逐次逼近动态规划算法优化水库群蓄水调度,并以清江梯级水电站为例验证模型应用效果。实例计算表明:与常规调度相比,基于蓄能指标的优化调度年均总发电量可增加3%;与传统基于蓄满率指标的调度相比,基于蓄能指标的调度可更全面地得到非劣解集。研究成果可为梯级水电站蓄水调度提供技术支撑。

基于长方体模型的大型水库重力变化效应分析——以三峡水库蓄水过程为例

大型水库由蓄水造成的水体质量的增加将对地球内部构造等产生影响,而地球内部构造的改变将会引起重力变化。三峡库区蓄水后形成的河道水库所引起的巨大水体负荷必然会对这种重力变化响应更明显。为了研究这种重力变化的程度,推导了长方体的重力变化公式,将其用于模拟计算三峡水库在不同蓄水高度下水体荷载变化对地面站的重力影响,同时考虑土壤水变化的影响,并将远处的重力变化内插到水库周边作为其他因素的影响。结果表明:长方体重力变化公式在蓄水过程中造成的重力变化的模拟中有较好的计算结果,在众多影响因素中,蓄水的影响占主要部分,加入土壤水变化的影响和远处重力变化内插至水库周边作为其他因素影响后,计算精度有了一定的提高,对较近站点处在3个时间段的平均绝对误差分别从7、 10.4和6.5μGal提高到4.3、 8.1和6.1μGal。

金沙江下游梯级水库运行后三峡水库高洪水期入库水沙特性

泥沙淤积问题直接影响着三峡水库的使用寿命及综合效益的发挥,研究其入库水沙特性对于解决水库泥沙淤积问题具有重要意义。根据水文站实测数据,分析了三峡水库入库水沙输移特性及来源组成变化,重点研究了金沙江下游梯级水库运行后的三峡水库高洪水期入库水沙特性。结果表明:2003-2021年,三峡水库入库泥沙集中于汛期的高洪水期,2013年以后该现象更为显著,泥沙来源也由金沙江为主转变为嘉陵江为主。寸滩站洪峰流量高于50000 m^(3)/s的高洪水期三峡入库沙量显著大于30000~50000 m^(3)/s区间的高洪水期,三峡水库泥沙调度关键在于上游发生编号洪水期间。三峡水库上游沱江或嘉陵江等支流发生流域性大洪水时,易引起高洪水期入库水沙出现“小水大沙”的特点。金沙江下游梯级水库运行后,三峡水库高洪水期入库泥沙大幅减少,中小洪水调度期间泥沙淤积量也大幅减小。研究结果可为三峡水库的泥沙精细化调度和长期高效使用提供基础数据支撑。