Benefit evaluation of the Three-Gorges Reservoir migration by an assessment index model based on analytic hierarchy process

An assessment index model was established to evaulate the benefit of the Three-Gorges Reservoir migration through the analytical hierarchy process. Totally 43 indicators were selected to assess the impact of migration on the economic, social and ecological environmental aspects of the migration communities, with the data of the indicators of the years 1992, 1998, 2002 which represented the period of premigration, the end of the first phase migration and the end of the second phase migration, respectively. The evaluation matrix is sufficiently consistent, with a consistency ratio CR equal to 0.086 3. The assessment turned out a benefit value for the economic subsystem in the year 2004 larger than triple the value in the year 1992, indicating a remarkable economic growth in the Reservoir area. The constantly increasing value for the social subsystem reflects the stable social situations. There is a slight decline in the assessment outcome of the ecological subsystem for the year 1998, which implies enviromental conservation was given insufficient importance during that period. On the whole, the implementation of the migration project is favorable to the Reservoir region, as confirmed by the stably increasing overall evaluation value from 42.22% in 1992 to 68.81% in 2002. However, there is still much room to improve from the status quo to the target criteria.

Three-Gorges Reservoir Area on the Yangtze River Faced with Risk of Induced Destructive Earthquakes

The Three-Gorge Water Conservancy Project on the Yangtze River started to impound water by locking gates on June 1, 2003. A swarm of more than 2000 small earthquakes suddenly occurred densely along the river section in Xinling Town north of Badong, Hubei Province, on June 7. This caused grave concern in the following years, but, with the completion of the second- and third-phase engineering construction, the water level in the reservoir will rise up to 156 m and 175 m respectively, no matter whether it can induce larger and stronger earthquakes. After an analysis of the distribution of active faults in the eastern part of the reservoir area, their intersections and capability to generate earthquakes from a seismo-tectonic viewpoint, we consider that after the reservoir impounding, two potential focal zones existing in Badong and Zigui counties may generate M 5.5 earthquake, the seismic intensity of which may reach Ⅷ. It will induce landslide bodies in the reservoir area to be reactivated and slide. The evidence is the large-scale landslide occurring on the Shazhenxi Creek river in Zigui County on June 12, 2003.

Water Environment Pollution in Three-Gorge Reservoir Area and Treatment Technology

After the erection of Three-Gorge Reservoir, the water environment in the reservoir area will be turned into water bodies like lakes, and the self-clarification ability of water will also be much slower than ever. Now, the quality of water in most segments in upper reaches of Yangtze River cannot meet the requirements of l-ll class Environment Quality Standard (GHZB1-1999). In Yangtze River, dialing River and Wujiang River, the main indexes such as colon bacillus, nonionic ammonia, chemical oxygen demand (COD), petroleum, phenol, total phosphorus (TP), heavy metal, etc., have exceeded the standard limits. The water bodies of the reservoir area are facing serious risk of eutrophicationm. To solve that problem, a countermea-sure of multi-spot diverted treatment and separate discharge is recommended. For doing this, lots of small-scale wastewater treatment facilities employing updated activated sludge treatment technologies are to be set up. Up to now, a number of sewage treatment technologies to control eutrophication of water have been developed, which include processes of sequencing batch activated sludge (SBR), absorbing bio-degradation (AB), oxidation channel, package intermittent aeration system (PIAS), intermittent cycle extended aeration system (ICEAS), UNITANK and so on. The Effective one to be applied in the reservoir area should convey the requirements of ecological agriculture, forestry and urban planning, and be accompanied by legal support for appropriate exploitation of natural resources.

Land Use Zoning in Three-Gorge Reservoir Region:A Case Study of Fengdu County in Chongqing Municipality

Taking Fengdu County in Three-Gorge Reservoir region as an example,this paper applies the dynamic clustering analysis model, and divides land resource utilization of Fengdu County into three zones: Yangtze River valley economic zone,low mountains and hills agricultural zone,and low and middle agricultural,forestry and animal husbandry zone. It also analyzes current situation and existing problems in the land utilization of every zone,and finally puts forward corresponding recommendations.

Data-augmented landslide displacement prediction using generative adversarial network

Landslides are destructive natural disasters that cause catastrophic damage and loss of life worldwide.Accurately predicting landslide displacement enables effective early warning and risk management.However,the limited availability of on-site measurement data has been a substantial obstacle in developing data-driven models,such as state-of-the-art machine learning(ML)models.To address these challenges,this study proposes a data augmentation framework that uses generative adversarial networks(GANs),a recent advance in generative artificial intelligence(AI),to improve the accuracy of landslide displacement prediction.The framework provides effective data augmentation to enhance limited datasets.A recurrent GAN model,RGAN-LS,is proposed,specifically designed to generate realistic synthetic multivariate time series that mimics the characteristics of real landslide on-site measurement data.A customized moment-matching loss is incorporated in addition to the adversarial loss in GAN during the training of RGAN-LS to capture the temporal dynamics and correlations in real time series data.Then,the synthetic data generated by RGAN-LS is used to enhance the training of long short-term memory(LSTM)networks and particle swarm optimization-support vector machine(PSO-SVM)models for landslide displacement prediction tasks.Results on two landslides in the Three Gorges Reservoir(TGR)region show a significant improvement in LSTM model prediction performance when trained on augmented data.For instance,in the case of the Baishuihe landslide,the average root mean square error(RMSE)increases by 16.11%,and the mean absolute error(MAE)by 17.59%.More importantly,the model’s responsiveness during mutational stages is enhanced for early warning purposes.However,the results have shown that the static PSO-SVM model only sees marginal gains compared to recurrent models such as LSTM.Further analysis indicates that an optimal synthetic-to-real data ratio(50%on the illustration cases)maximizes the improvements.This also demonstrates the robustness and effectiveness of supplementing training data for dynamic models to obtain better results.By using the powerful generative AI approach,RGAN-LS can generate high-fidelity synthetic landslide data.This is critical for improving the performance of advanced ML models in predicting landslide displacement,particularly when there are limited training data.Additionally,this approach has the potential to expand the use of generative AI in geohazard risk management and other research areas.

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。

Seasonal succession of phytoplankton in response to the variation of environmental factors in the Gaolan River, Three Gorges Reservoir, China

To understand the responses of a freshwater ecosystem to the impoundment of the Three Gorges Reservoir （TGR）, phytoplankton was monitored in the tributaries of the TGR area. From August 2010 to July 2011, algal species composition, abundance, chlorophyll a and other environmental parameters were investigated in the Gaolan River, which is a tributary of Xiangxi River. Thirty-one algal genera from seven phyla were identified. Results show that the lowest concentrations of total phosphorus （TP） and total nitrogen （TN） were 0.06 mg/L and 1.08 rag/L, respectively. The values of TP and TN exceeded the threshold concentration of the eutrophic state suggested for freshwater bodies. In the Gaolan River, the succession of phytoplankton showed clear seasonal characteristics. Different dominant species were observed among seasons under the control of environment factors. In spring and summer, the dominant species were Nitzschia sp. and Aphanizomenon flos-aquae （L.） Ralfs, the limiting nutrient was NO3^--N, and the key environmental factor for phytoplankton population succession was water temperature （WT）. In autumn and winter, the dominant species were A.flos-aquae and Chlorella sp., the limiting nutrient was pO3--P, and the key environmental factors were transparency and WT. This study illustrates the influence of physical and chemical factors on phytoplankton seasonal succession in a tributary of TGR since the downstream regions of Xiangxi River and Gaolan River became reservoirs after impoundment of the Three Gorges Dam. We suggest that this activity has significantly affected water quality in the dam area.

Reservoir-induced landslides and risk control in Three Gorges Project on Yangtze River,China

The Three Gorges region in China was basically a geohazard-prone area prior to construction of the Three Gorges Reservoir （TGR）. After construction of the TGR, the water level was raised from 70 m to 175 m above sea level （ASL）, and annual reservoir regulation has caused a 30-m water level difference after impoundment of the TGR since September 2008. This paper first presents the spatiotemporal distribution of landslides in six periods of 175 m ASL trial impoundments from 2008 to 2014. The results show that the number of landslides sharply decreased from 273 at the initial stage to less than ten at the second stage of impoundment. Based on this, the reservoir-induced landslides in the TGR region can be roughly classified into five failure patterns, i.e. accumulation landslide, dip-slope landslide, reversed bedding landslide, rockfall, and karst breccia landslide. The accumulation landslides and dip-slope landslides account for more than 90%. Taking the Shuping accumulation landslide （a sliding mass volume of 20.7 × 106 m^3） in Zigui County and the Outang dip-slope landslide （a sliding mass volume of about 90 × 106 m^3） in Fengjie County as two typical cases, the mechanisms of reactivation of the two landslides are analyzed. The monitoring data and factor of safety （FOS） calculation show that the accumulation landslide is dominated by water level variation in the reservoir as most part of the mass body is under 175 m ASL, and the dip-slope landslide is controlled by the coupling effect of reservoir water level variation and precipitation as an extensive recharge area of rainfall from the rear and the front mass is below 175 m ASL. The characteristics of landslide-induced impulsive wave hazards after and before reservoir impoundment are studied, and the probability of occurrence of a landslide-induced impulsive wave hazard has increased in the reservoir region. Simulation results of the Ganjingzi landslide in Wushan County indicate the strong relationship between landslide-induced surge and water variation with high potential risk to shipping and residential areas. Regarding reservoir regulation in TGR when using a single index, i.e. 1-d water level variation, water resources are not well utilized, and there is also potential risk of disasters since 2008. In addition, various indices such as 1-d, 5-d, and 10-d water level variations are proposed for reservoir regulation. Finally, taking reservoir-induced landslides in June 2015 for example, the feasibility of the optimizing indices of water level variations is verified.

Filling of the Three Gorges Reservoir to the 135-m Level: Instant Effects on the Yangtze Discharge and Suspended Sediment Concentration Entering the Estuary

Via the valuable opportunity of the Three Gorges Reservoir (TGR) 135-m filling in June 2003, the Yangtze discharge and suspended sediment concentration (SSC) entering the estuary during the period from 15 May to 15 July 2003 were analyzed to examine the instant effects of the filling on them. The Yangtze discharge and SSC entering the estuary in the periods before, during and after the filling clearly indicated three phases: 1) the pre-storage phase characterized by natural conditions, in which the SSC increased with increasing water discharge; 2) the storage phase, during which the SSC decreased dramatically with decreasing water discharge; and 3) the post-storage phase, during which both the SSC and water discharge remained at relatively low levels first until the end of June, then the SSC increased gradually with increasing water discharge. It seems that the times for the instant effects of the decreasing discharge downstream from the upper Yangtze on the Yangtze discharge and SSC entering the estuary due to the TGR 135-m filling to take place were about 5 d and 1 d respectively, while both were about 18 d for those of the increasing discharge. This probably reflects the buffering and resultantly hysteresis of the 1800-km stretch from the upper Yangtze to the estuary. The results are helpful for scientific and hydrological investigation of the Yangtze mainstream downstream from the TGR Dam and of the estuarine and adjacent coastal waters.

Flocculation properties of cohesive fine-grained sediment in the Three Gorges Reservoir under variable turbulent shear

Sediment flocculation is a key process for the deposition of fine-grained sediments in the Three Gorges Reservoir(TGR)of China.Sediment flocculation influences the evolution of the river regime,but also hampers the smooth navigation in the long term.However,the flocculation process and its controlling factors are poorly understood.We experimentally determined the flocculation properties of cohesive sediment of samples from the TGR(predominantly a mixture of clay and silt)over a range of turbulent shear rates and sediment concentrations.The experiments were conducted in an almost isotropic turbulence field,which was simulated by an array of horizontal oscillating grids in a water tank.Sediment flocculation was recorded by a camera and investigated by image analysis.Our new data indicate that flocculation is generally a response in equilibrium median floc size(d_(f,50))to the increase of the shear rate G.The peak value is attained at G=16.5 s^(-1),where d_(f,50) is 81.3μm(for the suspended sediment concentration(ssc)=0.4 g/L)and 107μm(for ssc=0.7 g/L),respectively.At low shear rates(G<16.5 s^(-1)),the equilibrium floc sizes d_(f,50) increase with rising shear rate G and isinversely related to the Kolmogorov micro length scale η.We attribute this variability to an insufficient deposition time of the sediment flocs in the water tank.Settling velocities,calculated from our experimental data of the floc sizes,are almost consistent with in-situ measured settling velocities,and are ten times larger than the terminal settling velocity of primary particles as calculated from Stokes'law.

三峡水库补水调度对东洞庭湖典型沉水植物生境适宜性的影响

沉水植物是东洞庭湖水生态修复的重要物种,水深是影响沉水植物生长的关键因子之一。为定量描述三峡水库不同补水调度方式对东洞庭湖典型沉水植物生长生境的影响,以刺苦草(Vallisneria spinulosa)为目标物种,利用物理栖息地模型建立三峡水库补水调度期间不同出库流量与东洞庭湖刺苦草生长生境加权可利用面积(WUA)的关系。结果表明:刺苦草生长生境的适宜水深为0.2~1.8 m,最适宜水深为0.5~1.0 m;三峡水库实施补水调度后,东洞庭湖刺苦草生长生境的WUA整体呈现均匀上升趋势;三峡水库补水调度期间,出库流量为5 500~10 500 m^(3)/s时,刺苦草生长生境最适宜水深范围对应的WUA呈现先增后减趋势,在出库流量为9 500 m^(3)/s时WUA最大(74.46 km^(2)),可认为刺苦草生长最适宜出库流量为8 500~10 500 m^(3)/s。研究成果可为通过三峡水库生态调度进行东洞庭湖水生态环境恢复及保护提供参考。

Diversity and ecological assembly process of aerobic anoxygenic phototrophic bacteria in a low irradiation area,Three Gorges Reservoir

Aerobic anoxygenic phototrophic bacteria(AAPB)are significant bacterial groups in aquatic ecosystems,known for their rapid growth and photoheterotrophic characteristics.However,the distribution and ecological assembly process of AAPB in low irradiation freshwater basins remain unclear,warranting further investigation.In this study,we present the diversity,abundance,spatial variations,ecological process,and community interaction of AAPB in sediment of Three Gorges Reservoir(TGR)under low irradiation.Our findings demonstrate the dominant genera of AAPB community that exist in the TGR area also are appeared in different waters,with some regional preference.Moreover,the concentration of pufM gene,an indicator for AAPB,maintains a consistently high numerical level ranging from(2.21±0.44)×10^(4)to(9.98±0.30)×10^(7)gene copies/g.Although solar irradiation is suggested as the major factor affecting AAPB,it remains unclear whether and how AAPB differ between regions due to varying solar irradiation levels.Our results show spatial differences between total bacteria and AAPB communities,with significant differences observed only in AAPB.Geographical and environmental factor contributed less than 10%to the spatial difference of community,with sediment type and environmental factors being the key factors influencing microbial community structure.The stochastic process plays a dominant role in the aggregation and replacement of AAPB communities,among which the most contribution is dispersal limitation.For AAPB network,Yoonia and Gemmobacter are the hubs for modules.Those results valuable insights into the AAPB communities in TGR with low irradiation.

三峡水库蓄水初期水生态环境特征分析

以2003年10月和2004年4月的两次现场调查数据为基础,分析三峡水库蓄水初期的水生态环境特征。结果表明,蓄水初期水库水体交换能力减弱,水库有机污染甚微,但水体TN、TP浓度偏高,水库整体处于中营养状态;根据水生态环境特征的差异性,水库水域可划分为3种类型区,即坝前水域、库区干流水域以及库区支流洄水河段。对主要影响因素进行分析,发现流速、营养盐含量及水温是影响水生态环境特征的主要因素,而由于各类型区的TP、TN等营养盐含量均较高,水温及流速已成为三峡水库水生态环境特征的控制性因子。探讨3类不同水域的富营养化敏感性,表明坝前水域及库区支流洄水河段是库区未来富营养化的敏感水域。

三峡水库支流回水河段氮磷负荷与干流的逆向影响

通过分析三峡库区大宁河回水河段氮磷的来源、数量及时空特征,研究三峡水库成库初期和稳定运行期,次级支流回水段受干流的逆向影响.结果表明,成库初期,支流回水段的氮磷分配特征初步呈现干流逆向影响效应,分别有19.05%TN、28.93%TP源于干流倒灌输入;由于干流顶托作用,氮磷呈现具峰值的空间分布特征.在稳定运行期,支流回水段的氮磷来源及数量将明显受干流逆向影响,在其中的藻类适宜生长期,大宁河回水段干流倒灌输入的TN、TP分别高出上游径流输入近3倍、10倍,明显高于成库初期.当运行水位从145m升至175m时,支流回水段纳受干流倒灌输入的TN、TP可分别达15484.99、1185.75t.研究表明,干流逆向影响可能加剧三峡水库水体的富营养化.

三峡库区支流富营养化模型开发研究

为保护三峡库区水环境,应对库区支流富营养化演变态势进行模拟预测。以受三峡水库蓄水影响显著的代表性支流大宁河为例,在考虑营养盐、气候条件(包括水温和光照)对藻类生长速率影响的基础上,针对三峡库区特点,着重研究水动力条件对藻类生长速率的影响规律,进行富营养化模型综合开发研究,并利用三峡水库蓄水后大宁河回水影响区河段实测资料进行模型验证计算。结果表明,该模型能较好地反映三峡水库蓄水后,库区支流水环境条件发生显著变化状态下藻类生长繁衍特点,能够用来进行三峡库区富营养化预测,也可为其他类似水域研究富营养化问题提供参考。

三峡库区生态环境变化后钉螺孳生可能性的研究

目的研究三峡库区生态环境变化钉螺孳生的可能性,探讨钉螺在库区可能孳生的危险环境,并提出库区防止钉螺孳生的对策。方法湖北省宜昌市、重庆市万州区、江津市各选取一个生态观测点。模拟生态环境变化后库区淤积洲滩、移民点灌溉沟渠环境,开展钉螺生态学实验,并设立对照区。在实验室开展钉螺生存和繁殖实验,并收集库区气候、土壤等自然资料。结果生态环境变化后,库区适宜钉螺孳生。万州、江津观测点比宜昌观测点更适宜钉螺生存(P均<0.05)。江津、万州观测点各实验区钉螺存活率仅少数月份在50%以下,多数月份在80%以上,宜昌观测点钉螺存活率相对较低,且随时间呈下降趋势。土壤湿度与钉螺存活率存在相关性(r=0.3712,P=0.002),土壤pH值、有机质等指标都影响钉螺孳生。实验室结果表明库区土壤适宜钉螺生存,但比现场存活率低,且有幼螺孵出。结论模拟生态环境变化后库区条件,在灌溉沟渠、淤积洲滩环境下,钉螺可以生存繁殖,特别是万州、江津地区更适宜钉螺孳生。

基于SWAT模型的三峡库区大流域不同土地利用情景对非点源污染的影响研究

非点源污染对三峡库区流域的水环境污染起到主导作用。本文将SWAT(Soil and Water Assessment Tool)模型应用于库区大尺度流域的污染模拟研究中,以2005年土地利用现状为基准设定了6种土地利用情景,定量分析了不同土地利用措施对非点源污染的控制效果。首先采用三峡库区流域2002—2008年的水文、水质实测数据对建立的SWAT模型进行率定与验证,径流、泥沙、营养盐的评价指标ENS均达到令人满意的效果,表明SWAT模型应用于三峡库区流域是可行的。不同土地利用情景的非点源影响模拟结果表明,通过退耕还林措施将25°、15°、6°以上的耕地转化为林地可达到较好的非点源污染消减效果,考虑库区地处贫困山区,25°以上耕地退耕还林更为经济、可行;相同区域的草地转化为林地所产生的非点源污染要远远小于转化为耕地而产生的污染物,因此应严格控制自然植被退化为耕地的现象发生,否则会严重加剧库区污染状况;库区扩大林地范围的方案要有计划性、针对性,可在减少坡耕地的基础上进行,该措施能最大限度地减少库区非点源污染。本研究所得结论为政府科学合理的制定三峡库区流域非点源污染控制方案提供了重要科技支撑。

三峡库区农业土壤重金属含量特征及污染评价--以Cu Pb和Zn为例

通过田间采样和室内分析,对重庆市三峡库区6个区(县)(丰都、奉节、江津、万州、武隆和忠县)农业土壤中Cu、Pb和Zn的含量特征进行了调查研究,并同时对其污染状况进行了评价。结果表明,重庆市三峡库区农业土壤Cu、Pb和Zn全量的平均值分别为(29.96±12.80)mg·kg-1、(25.45±8.80)mg·kg-1和(64.79±18.79)mg·kg-1;其有效态含量的平均值分别为(1.66±1.36)mg·kg-1、(1.67±1.24)mg·kg-1和(2.95±3.02)mg·kg-1;3种重金属有效态含量变异均明显大于全量的变异;Cu、Pb和Zn有效性系数分别为(5.53±3.77)%、(7.52±7.18)%和(4.36±4.14)%。各区(县)农业土壤Cu、Pb和Zn的有效态与其全量间均呈显著或极显著正相关;Cu、Pb和Zn全量两两间也呈现显著或极显著正相关。各区(县)农业土壤重金属单因子污染状况均表现为Cu>Zn>Pb;各区(县)农业土壤重金属综合污染指数平均值为0.38±0.20,属安全等级,表明调查区域土壤清洁。

三峡水库2003年蓄水对长江悬沙中值粒径的影响

长江三峡水库分别在2003—06-01～06-10和10-25～11-052次蓄水，坝前水位分别达到135m和139m（吴淞高程）。通过三峡大坝上下游长江干流主要水文控制站（寸滩、宜昌、沙市、汉口和大通）蓄水后（2003～2005）的年均悬沙中值粒径分别与多年平均值以及蓄水前一年（2002）实测值相比较，分析了三峡水库2003年蓄水对长江悬沙中值粒径的影像。结果显示，与2002年和多年平均值相比，寸滩、宜昌、汉口和大通站蓄水后（2003～2005）年均悬沙中值粒径偏小，而沙市站明显偏大。这很可能说明，三峡水库蓄水引起大量泥沙特别是粗颗粒泥沙在库区落淤，从三峡大坝下泻的非正常清水，导致宜昌站至沙市站之间的长江河道遭受到严重冲刷，从该段河道冲刷起来的粗颗粒泥沙随着变小的河道坡降和河水流速，又逐渐沉降在沙市和汉口之间的河道。这些结果有助于决策者更好地管理三峡水库以及各行业学者更好地了解三峡水库蓄水带来的影响。

基于SRTM-DEM数据的三峡库区蓄水负荷模型及其地表重力与形变响应模拟

以三峡库区蓄水负荷变化为切入点,研究了库区因蓄水导致的地表重力与形变响应。通过高分辨率SRTM-DEM数据与三峡库区主干道及各支流边界的地形对应关系,构建得到不同蓄水水位下的蓄水负荷模型,并且给出了不同水位与库区整体库容量体积及受淹面积之间的数学拟合关系。在此基础上,结合弹性负荷响应理论及macson拟合方法,计算得到整个库区在蓄水第2阶段与第3阶段地表重力场及形变场的空间分布,以及库区蓄水库容量变化的60阶次球谐系数结果,并与GRACE监测结果进行了对比分析。GRACE去除CLM4.5模型后的陆地水储量可认为与三峡库区蓄水变化直接相关,两者之间的差异可能包含了在巨大水体负荷压力下出现的地下水渗透效应。本文理论模拟结果以期为实际观测资料的对比分析和相关校正提供支撑。有助于挖掘库区滑坡活动及水库地震等与库水负荷变化之间的关系。