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In order to solve the problem of lack of unified evaluation criteria for water quality evaluation in the Three Gorges Reservoir under different hydrologic condition, hydraulic retention time and flow rate were calculated wih the hydrological data of 6 intact hydrological years after the 175 m impoundment in the Three Gorges Reservoir using the concept of segment capacity. Results indicate that the hydrological conditions of the Three Gorges Reservoir have obvious spatial and temporal differences. The whole river should be evaluated according to the river standard during the wet season. In the dry season, the upstream of Wanxian should be evaluated according to the river standards and the downstream of Wanxian should be evaluated according to lake standard. The tributary bay should be evaluated according to the lake standard. The conclusion obtained by this evaluation method is consistent with actual situation of the reservoir, providing a theoretical basis and technical support for the targeted protection of water environment in river-type reservoirs.

Human activities are important factors that trigger frequent occurrences of landslides; thus, for landslide control, it is critical to determine the influence of human activity on landslide occurrence probability. The Three Gorges area is a region in the world that typically experiences serious landslide disasters and frequent human activities. The objective of this work is to employ the Three Gorges area as an example to reveal the impact of human activity on the dynamic development of landslide susceptibility from 2010 to 2019. Some new viewpoints are suggested for the five aspects: (1) High-precision landslide susceptibility maps are generated by a combination of multiresolution segmentation and convolutional neural network algorithms. Moreover, the dynamic development rules of landslide susceptibility from 2010 to 2019 are revealed. (2) The change in landslide susceptibility in the study area from 2010 to 2019 was mainly caused by the combined action of rainfall and human activity. The fluctuation of reservoir water level had a less influence on the development of landslide susceptibility. (3) Some human activities, especially road construction, farmland appropriation for building construction, agricultural reclamation, farmland cultivation and irrigation, initiation of commercial planting, urban expansion, and large-scale deforestation, may dramatically increase landslide occurrence probability. (4) Human activities, e.g., conversion of farmland to forestry, artificial recovery of natural vegetation, and later periods of artificial planting, may obviously reduce landslide susceptibility. (5) The human activity causes and mechanisms influencing landslide susceptibility in the study area are proposed, including transpiration and anchorage of plants, slope reinforcement by plant roots, destruction of slope stress equilibrium, and soil erosion.

Plant roots have great effect on the process of soil detachment, but the contribution of the physical and biochemical effects of root on soil detachment have not been sufficiently evaluated. For the purpose to distinguish the relative contribution of the root physical effect and biochemical effect to soil erosion resistance, three kinds of treatment, soil samples without roots, dead roots and live roots, were chosen to simulate the condition of no root effect, the root’s physical effect and the root’s whole effect on the soil detachment, respectively. The Cynodon dactylon and purple soil in Three Gorges Reservoir Area in China were selected to conduct the scouring experiment under condition of five slope gradients (17.63%, 26.79%, 36.40%, 46.63% and 57.73%) and three runoff rates (1, 2 and 3 L min-1). The soil detachment process under different treatment conditions was analyzed. The effects of slope gradient and the runoff rate on soil detachment rate were also estimated for different treatment conditions and the contributions of the physical and biochemical effects of root on soil detachment were also evaluated. The results indicated that detachment rate showed a dramatically decrease initially, followed by gradual decrease until to a stable stage for all treatments. The soil detachment rate can be effectively described with the slope gradient and the runoff rate by using the power function, which was more influenced by slope gradient than by runoff rate for all the treatment conditions in this study. Plant roots could effectively diminish the soil detachment rate, and the contributions of physical and biochemical effects of root on detachment were 59.64%–82.09% and 17.91%–40.36%, with mean values of 68.92% and 31.08%, respectively. The root’s physical effect is the main reason strengthens soil erosion resistance.

This study advances our understanding of the processes whereby actors select and play out particular tactics and framings from “repertories of contention” to fight against repressive states. Empirically, it focuses upon a unique dataset captured from a discussion group of 140 participants in an instant messenger app—WeChat. Related to a petition campaign in Beijing, the data reflect the claims of over 1,000 petitioners who had been forced to relocate to different parts of China by the building of the Three Gorges Dam (1994–2006). The real-time chronological exchanges online among petitioners and other displaced persons reveal the petitioners’ tactics against the state’s counterpetition strategies, and the motives behind the petitioners’ repertoire selection. Theoretically, this study seeks to understand this case of grassroots resistance in terms of Bourdieu’s concept of habitus. It shows that the actors pursued parochial and rent-seeking motives—as symbolized in the discursive usage of nao (or troublemaking)— more than their defense of legal and constitutional rights as citizens. Both the characteristics and outcomes of such repertoire selection, shaped by what I call the habitus of nao, are discussed.

Climate change has caused an increase in extreme rainfall and snowfall in many parts of the world. For example, in the Three Gorges Reservoir area, annual precipitation has gradually increased and the occurrence of heavy precipitation events has become more frequent. As the reservoir water level rises in October, the high water combined with heavy precipitation creates a “special hydrological environment,” which recently caused the Yanguan landslide. The Yanguan landslide is a large-scale soil landslide that has undergone two slides, pushed the Yanguan Road Bridge into the reservoir, and caused serious damage to roads and buildings. In the present study, the combined effects of high water and heavy precipitation on landslide deformation characteristics (movement patterns and evolution processes) have been analyzed and a stability evaluation was conducted through a field investigation and numerical simulation. To comparatively analyze these combined effects of high water and heavy precipitation, a two-dimensional finite element model was created, and four cases of the hydrological environment were calculated with the model. Results show that the factor of safety was maintained in the range of 1.013 to 1.059 before the precipitation conditions changed. However, as heavy precipitation increased in October 2017 (reaching 356.4 mm in 1 month), this “special hydrological environment” potentially decreased the FoS to 0.948, which is 9.6% lower than that observed under normal conditions, and helped drive the Yanguan landslide activity. The analysis of these various combined effects can also indicate the impacts of climate change on landslides in other areas of the Three Gorges Reservoir.

Monitoring data show that many landslides in the Three Gorges region, China, undergo step-like displacements in response to the managed, quasi-sinusoidal annual variations in reservoir level. This behavior is consistent with motion initiating when the reservoir water level falls below a critical level that is intrinsic to each landslide, with the subsequent displacement rate of the landslide being proportional to the water depth below that critical level. Most motion terminates when the water level rises back above the critical level, so the annual step size is the time integral of the instantaneous displacement rate. These responses are incorporated into a differential equation that is easily calibrated with monitoring data, allowing prediction of landslide movement from actual or anticipated reservoir level changes. Model successes include (1) initiation and termination of the annual sliding steps at the critical reservoir level, producing a series of steps; (2) prediction of variable step size, year to year; and (3) approximate prediction of the shape and size of each annual step. Annual rainfall correlates poorly with step size, probably because its effect on groundwater levels is dwarfed by the 30 m annual variations in the level of the Three Gorges Reservoir. Viscous landslide behavior is suggested.

Rain classroom is a big data tool that effectively connects the teacher with students throughout the teaching process. This paper mainly applies rain classroom in blended teaching of college students, and evaluates the application effect. Firstly, the authors set up a model of rain classroom, covering all three phases of the teaching process: before-class (B), in-class (I) and after-class (A). Next, the BIA model was applied to the course Film and Television Appreciation, and the key issues in each phase were explained. To evaluate the effect of the BIA model, two questionnaire surveys were carried out among engineering students in Chongqing Three Gorges University. The results show that rain classroom can greatly improve the learning effect of the target course in various aspects: the teacher could arouse the students’ learning interest by sending red packets, make students more attentive through limited-time quiz, and reduce the absence through random roll call; the students were actively involved in group activities and confident in presenting their findings; however, many students most students switched to other apps in the class. The research results provide new insights to the application of big data technology in college education.

Landslides represent major threats to life and property in many areas of the world, such as the landslides in the Three Gorges Dam area in mainland China. To better prepare for landslides in this area, we explored how several machine learning algorithms (long short term memory (LSTM), random forest (RF), and gated recurrent unit (GRU)) might predict ground displacements under three types of landslides, each with distinct step-wise displacement characteristics. Landslide displacements are described with trend and periodic analyses and the predictions with each algorithm, validated with observations from the Three Gorges Dam reservoir over a one-year period. Results demonstrated that deep machine learning algorithms can be valuable tools for predicting landslide displacements, with the LSTM and GRU algorithms providing the most encouraging results. We recommend using these algorithms to predict landslide displacement of step-wise type landslides in the Three Gorges Dam area. Predictive models with similar reliability should gradually become a component when implementing early warning systems to reduce landslide risk.

This paper presents an in-depth analysis of the deformation characteristics and reactivation mechanisms of a giant ancient translational landslide in the Three Gorges Reservoir (TGR) based on more than 6 years of monitoring data with the assistance of in situ surveys. The Outang landslide, divided into three active parts, has a total volume of approximately 90 million m3 and slides along weak interlayers (WIs). Since the impoundment, the landslide has been experiencing persistent deformations with some distinct movement signs. The temporal displacements are marked by seasonal cycles of fast displacements in the summer followed by almost imperceptible movements for the remainder of each hydrologic year. The spatial displacement rates gradually increased with the increase in altitude. The primary triggering factors for slope movement could transition from the drawdown of the reservoir water to the periodic rainfall. The affected areas by the former and latter are mainly concentrated in the front part and the upper part of the slope, respectively. The landslide exhibited a composite push-retrogression-type failure evolution with the fluctuating reservoir levels destabilizing rock masses at the front part of the landslide and the precipitation mainly mobilizing materials in the upper part of the slope. Currently, the landslide is in a state of continuous movement. The toe area and upper part of the landslide should receive high priority for the development of preventative measures.

Large-scale water conservancy projects bear much economic and social significance. However, there is a lack of systematic research on how such projects affect radioactivity levels in regional water bodies. For the first time, the present paper uses data for nearly 10 y at different impoundment levels during construction of the dam to analyze changes in water radioactivity concentration levels in China’s Three Gorges region, in order to provide a valuable reference for evaluating the impact of large-scale water conservancy projects on radioactivity concentration levels. Results show that gross α, gross β, U, Th, 226Ra, 40K, 90Sr and 137Cs levels in the water bodies of the Three Gorges region fall within normal limits and annual effective dose for the adults, children and infants are below the WHO recommended reference level of 0.1 mSv per y. The period where the sample was collected and spatial distribution are the main reasons why some radionuclides are not normally distributed. Different water levels during different periods result in large variations in the levels of certain radionuclides, indicating that water levels can have a strong influence on radionuclide levels in reservoir regions. Hence, when evaluating the impact of large-scale water conservancy projects on radioactivity levels, analysis should be carried out on samples collected during different periods in order to make accurate assessments.

Recently, scholarship on migration has shifted to address people’s agency and reflexivity, particularly those of marginal groups such as refugees, older migrants and rural-urban migrants. These ind...

Exopalaemon modestus (Heller, 1862) and Macrobrachium nipponensis (De Haan, 1840) (Palaemonidae) are ecologically and commercially important fishery resources in the Three Gorges Reservoir (TGR), China, and co-occur in demersal habitats. Little information is available on their biology. We compared the reproductive traits of both species on the upper, middle, and lower sections of the TGR. Both species differed in mean size at maturity, which increased from upper to middle and lower sections. Sex ratios were significantly biased toward females, but no significant differences were observed among the three sites for either species. Both species displayed an obvious trade-off between embryo size and fecundity, with the size of embryos being the smallest but with the highest fecundity at the upper section, followed by the middle and lower sections. Exopalaemon modestus spawned from early April to late September, with a peak in May and June, whereas M. nipponensis spawned from late April to early October with a peak in June and July. The spatially distinct reproductive traits, which were concordant across species, are likely related to differences in habitat characteristics such as water flow. We suggest that management strategies should account for the reproductive biology of the two species in order to maintain a sustainable fishery in the reservoir.

This paper examines the social integration of individuals in the Fuling District, Chongqing Municipality, China, following the construction of the Three Gorges Project. The experience of these indi...

On 4 April 2013, a 1.5 million cubic meter landslide occurred in Sunjia Town, Wanzhou County, Three Gorges Reservoir, China. After initiation, the Sunjia landslide traveled about 30 m toward the northeast and destroyed most of the infrastructure in its path. The landslide was triggered by heavy rainfall and previous slope excavations, but this slope also displayed a complicated failure process: the overlying earth slope first deformed and then induced sliding along underlying rock surfaces. Surface displacements that resulted from continuous creeping of the post-event slope were observed by an emergency monitoring system that revealed the disequilibrium state of the slope. To discuss the stability and future movements of the remaining unstable debris deposits, we developed a geotechnical model of the post-slide slope, calculated how it can slide again in an extreme rainfall scenario, and estimated the potential runout distance using the Tsunami Squares method. We then estimated the number of people and the value of the infrastructure threatened by this potential landslide. Lastly, we analyzed the vulnerability of elements at risk and quantitatively evaluated the hazard risk associated with the most dangerous scenario. This quantitative risk analysis provides a better understanding of, and technical routes for, hazard mitigation of rainfall-induced complex landslides.

The Three Gorges Reservoir region suffers from severe soil erosion that leads to serious soil degradation and eutrophication. Interrill erosion models are commonly used in developing soil erosion control measures. Laboratory simulation experiments were conducted to investigate the relationship between interrill erosion rate and three commonly hydraulic parameters (flow velocity V, shear stress τ and stream power W). The slope gradients ranged from 17.6% to 36.4%, and the rainfall intensities varied from 0.6 to 2.54 mm·min−1. The results showed that surface runoff volume and soil loss rates varied greatly with the change of slope and rainfall intensity. Surface runoff accounted for 67.2–85.4% of the precipitation on average. Soil loss rates increased with increases of rainfall intensity and slope gradient, Regression analysis showed that interrill erosion rate could be calculated by a linear function of V and W. Predictions based on V (R 2 = 0.843, ME = 0.843) and W (R 2 = 0.862, ME = 0.862) were powerful. τ (R 2 = 0.721, ME = 0.721) did not seem to be a good predictor for interrill erosion rates. Five ordinarily interrill erosion models were analyzed, the accuracy of the models in predicting soil loss rate was: Model 3 (ME = 0.977) > Model 4 (ME = 0.966) > Model 5 (ME = 0.963) > Model 2 (ME = 0.923) > Model 1 (ME = 0.852). The interrill erodibility used in the model 3 (WEPP) was calculated as 0.332×106 kg·s·m−4. The results can improve the precision of interrill erosion estimation on purple soil slopes in the Three Gorges Reservoir area.

Background: Modernization of Chinese adults is associated with increased atherosclerotic diseases. Over 1 million farmers have been resettled upland since 1996 in the Three Gorges dam project of th...

Curtain Weirs (CWs) are hydraulic structures that act as a barrier to the flow and diffusion of heat across the width of a water body. Algal blooms occur frequently in Xiangxi Bay (XXB), which is one of the largest tributaries of the Three Gorges Reservoir (TGR). Numerical modeling has become a widely accepted tool for predicting and diagnosing hydrodynamic problems. A laterally averaged two-dimensional hydrodynamic and water quality model (CE-QUAL-W2) was used to simulate the CWs and the hydrodynamics, temperature and chlorophyll-a concentrations for XXB. The developed model was calibrated using data collected in XXB from January to December in 2010. The results indicated that the maximum chlorophyll-a concentrations was observed 154 mg/m3 at sampling sites XX09, XX06 and XX01. The CWs led to a marked reduction of the overall chlorophyll-a concentrations 30–85% because of the CWs height and locations. Therefore, the proposed CWs represent a potential method of reducing algal blooms and improving water quality in XXB of the TGR. Keywords: Curtain weirs (CW), Xiangxi Bay (XXB), CE-QUAL-W2, Algal blooms, Three Gorges Reservoir (TGR)

Rainfall erosivity is a key factor to predict soil erosion rate in universal soil loss equation (USLE) and revised USLE (RUSLE). Understanding rainfall erosivity characteristics, especially its spatial distribution and temporal trends, is essential for soil erosion risk assessment and soil conservation planning. In this study, the spatial-temporal variation of rainfall erosivity in the Three Gorges Reservoir Area (TGRA) of China during 1960–2010, at annual and seasonal scales, was explored based on daily rainfall data from 40 stations (26 meteorological stations and 14 hydrologic stations). The Mann–Kendall test and Co–kriging interpolation method were applied to detect the temporal trends and spatial patterns. The results showed that TGRA’s annual rainfall erosivity increased from west, south, and east to the north-central, ranging from 3647.0 to 10884.8 MJ·mm·ha−1·h−1 with an average value of 6108.1 MJ·mm·ha−1·h−1. The spatial distribution of summer and autumn rainfall erosivity was similar to the pattern of annual rainfall erosivity. Summer is the most erosive season among four seasons, accounting for 53% of the total annual rainfall erosivity, and winter is the least erosive season. July is the most erosive month with an average of 1327.3 MJ·mm·ha−1·h−1, and January is the least erosive month. Mean rainfall erosivity was 5969.2 MJ·mm·ha−1·h−1 during 1960–2010, with the lowest value of 3361.0 MJ·mm·ha−1·h−1 in 1966 and highest value of 8896.0 MJ·mm·ha−1·h−1 in 1982. Mann–Kendall test showed that the annual rainfall erosivity did not change significantly across TGRA. Seasonal rainfall erosivity showed a significant decrease in autumn and insignificant decrease in summer and winter. Monthly rainfall erosivity in TGRA showed insignificant increases from Jun to Jul and then underwent decreases from Aug to Nov. and from Dec to Feb and it rose again in Feb reaching a 0.01 level significance. The daily rainfall data of supplemental stations is very useful to interpolate rainfall erosivity map, which could help to find the credible maximum and minimum value of TGRA. In total, the findings could provide useful information both for soil erosion prediction, land management practices, and sediment control project of TGRA.

SUMMARYSlippage on a deep fault, which cannot be directly measured, can be inferred from repeating earthquakes. Here, we use a matched filter technique (MFT) to detect missing earthquakes near the Xiannvshan fault in the Three Gorges Reservoir region of Central China. We detected 13 repeating aftershock sequences (RASs) containing 107 events after a Ms 4.4 local earthquake that occurred on 26 March 2014. The RASs occurred in the vicinity of the Ms 4.4 main shock hypocentre and were concentrated within a depth range of 4–7 km. The short-term slip rates estimated from these RASs varied from ∼0.001 to 0.31 mm d–1. The slip rates of the RASs followed an approximately logarithmic decay with RAS duration, suggesting that the deep Xiannvshan fault behaviour tended to follow the logarithmic velocity-strengthening friction law. Relatively high-stress RAS events seemed to influence the occurrence of other RAS events whereas we found no evidence that high-stress nearby events, including a Ms 4.6 local earthquake that occurred on 29 March 2014, triggered the RAS events. We suggest that the fault stress change caused by the Ms 4.4 main shock played a role in triggering the RAS events. Our results demonstrate that the MFT can effectively help identify repeating aftershocks, which could help decipher fault zone rheology.

The long-term stability of rock slopes is greatly affected by the creep behavior of rock mass. This study presents the creep behavior of a saturated silty mudstone that is from the Three Gorges Reservoir in China. Triaxial compression tests and triaxial creep tests were performed on the silty mudstone under different confining pressures. The test results show that the creep behaviors have three stages, namely, the primary creep stage, steady-state stage, and accelerated creep stage when the deviatoric stress is higher than the yield stress of the silty mudstone. The steady-state creep strain rate of the silty mudstone increases with the increment of the axial deviatoric stress. Partial reversals of the axial creep strain curve are found under the confining pressure of 1 MPa and 5 MPa, which may be caused by the expansion of illite minerals after being infiltrated by water in the rock voids. Based on the experimental data of the silty mudstone and the fractional calculus theory, a nonlinear creep model that describes the creep behaviors of the silty mudstone is proposed. The theoretical creep curves obtained from the creep model are in good agreement with the experimental data.

In order to study the treatment of a dangerous thick submerged rock mass, the Jianchuandong dangerous rock mass (JDRM) in the Three Gorges reservoir area is analyzed in this paper. Field investigation, on-site monitoring, and laboratory testing were used to analyze the deformation and failure mode of the dangerous rock mass. The analysis shows that the uneven pressure caused by the weight and deterioration of the base of the rock mass during the dry-wet cycles will eventually lead to slump failure of the JDRM. Preventative methods, including anchoring the upper part of the dangerous rock mass and reinforcement of the base of the rock mass, are proposed to improve the stability of the dangerous rock mass. Based on a numerical simulation, we conclude that anchoring the upper dangerous rock mass can effectively control the deformation of the dangerous rock mass and reinforcement of the base of the rock mass can block the slip zone of the dangerous rock mass. The combination of these two preventative methods significantly improves the stability of the dangerous rock mass. By comparing the stability of the dangerous rock mass before and after the implementation of these preventative methods during the dry-wet cycles, it can be seen that the preventative methods can satisfactorily ensure the long-term stability of the dangerous rock mass.

The Three Gorges Project has benefited shipping development in the upper Yangtze River by improving the waterway channel and thus increasing ship load and port handling capacity. However, the Three...

Due to severe congestion before the Three Gorges Dam, roll-on/roll-off and container carriers are encouraged to adopt water-land transshipment mode. Owing to high transit and road costs, however, carriers are reluctant to adopt this mode. In this paper, we study the spatial-temporal relationship between the transshipment mode and the transshipment cost. Furthermore, we analyze the feasibility of subsidy strategies with regards to water-land transshipment from the standpoint of the government. An evolutionary game theory model is used to identify the equilibrium points of transshipment and non-transshipment, as well as subsidy and non-subsidy strategies available to carriers and the government, respectively, under different scenarios. With a transshipment job for a major carrier as an example, freight prices offered by carriers and subsidies provided by the government under water-road and water-road-water modes are analyzed, with the aim of providing strategic input for both the government and the carriers.

The purpose of this paper is to study the sliding failure of the jointed rock slope caused by the degradation of rock mass mechanics under dry-wet cycles. Based on the mechanical parameters of reservoir limestone obtained under different numbers of dry-wet cycles, a discrete element approach was adopted to analyze the slippage failure mode of HuangNanBei slope in the Three Gorges Reservoir Region. The Barton-Bandis nonlinear strength criterion for discontinuities was used to improve the Mohr-Coulomb (M-C) sliding model, and the modified M-C sliding model could make the shear strength parameters of the discontinuities change with the stress state. Under the modified model, there was a tendency for disintegration between blocks in the process of slippage, which was more in line with the actual working conditions and proved the validity and necessity of this model. Furthermore, the slip rate increased with the increase of dry-wet cycles, and the increase trend had not slowed down after 30 dry-wet cycles. The cumulative displacement from 0 to 30 dry-wet cycles was obtained by changing the mechanical parameters of the discontinuities every 10 steps to simulate each dry-wet cycle. The pattern of the cumulative displacement curve was consistent with the slip curve of the 30th dry-wet cycle, which indicated that the degradation of the rock mass mechanics is irreversible. Consequently, strengthening the hydro-fluctuation belt is of great significance for disaster prevention and control in the reservoir region.

Due to the unprecedentedly increasing demands of waterway transportation on the Yangtze River during the latest years, traffic congestion at the Three Gorges Dam (TGD) has becoming a serious problem. In busiest seasons, a vessel may need to wait up to 3 days for passing the TGD via the ship lift or the five-stage ship lock. In order to improve the navigation efficiency and the utilization of passing facilities, a co-scheduling problem of ship lift and ship lock at the TGD is modeled in this paper. Besides, the improvement on effectiveness, safety and fairness of the navigation scheduling by introducing the ship lift is taken into account. The mathematical model proposed is, by nature, a two-stage problem, where the first-stage variables determine the assignments of passing facilities and the second-stage variables schedule the vessels. In order to solve the proposed mathematical model, a hybrid metaheuristic algorithm is used at the first stage to determine the allocation of vessels to different passing facilities and to different lockage through the maximization of facility utilization rate. The second-stage problem is then solved by CPLEX. The proposed mathematical model and algorithm are validated through a set of numerical experiments and a case study. The results show both the navigation efficiency and the utilization of passing facilities can be improved by using the proposed methods.

Ensemble learning methods can be used to evaluate landslide susceptibility when combined with remote sensing (RS) and geographic information systems (GIS). In this study, the rotation forest (ROF) and random forest (RF) ensemble learning models were applied to evaluate landslide susceptibility. The experiments selected the factors by analysing the linear relationship between the factors, explored the optimal proportions of non-landslide samples and landslide samples based on an unbalanced sample dataset, and used the factors before and after the selection to generate landslide susceptibility maps (LSMs) in the Zigui-Badong area. The results show that a suitable ratio between the sample types in the training set can achieve good results for both sensitivity and specificity. The RF models of the study area with 21 factors and 16 factors had sensitivities of 94.22% and 93.59%, respectively. The ROF models with 21 factors and 16 factors had sensitivities of 90.63% and 88.84%, respectively. Although both the RF and ROF models exhibited high accuracy, the RF model achieved a more reasonable and accurate LSM.

Construction of the Three Gorges Reservoir converted areas of the original terrestrial ecosystem along the shores into a draw-down zone with a fluctuating water-level at an elevation ranging between 145 and 175 m. The water-level fluctuation is regulated against the normal seasonal flooding with summer emergence and winter submergence. We investigated the seed rain and soil seed banks along elevational gradients of the Xiangxi zone in the reservoir to explore the characteristics of species composition and spatial distribution of seed rain and soil seed bank, and their similarities with standing vegetation under the regulated water-level fluctuation. The results showed that the seed rain and soil seed bank comprised 36 and 50 species of plants, respectively. These were predominantly annual herbaceous plants, which accounted for 54.02 and 66.0% of the seed rain and soil seed bank, respectively, with an average density of 445.16 ± 49.97 and 7322.18 ± 678.44 seeds/m2, respectively. The regulated water-level fluctuation resulted in greater species diversity and seed density of seed rain and soil seed bank in the middle and upper elevations of the zone than that of the lower elevations. The similarity coefficient between seed rain and seed bank, seed bank and extant vegetation, seed rain and extant vegetation was 0.488, 0.373 and 0.466, respectively. Effects of the regulated water-level fluctuation on the species compositions and spatial distribution of the seed rain and seed bank, and their similarities with existing vegetation were further discussed by contrast with the current research in the same field.

Bacterioplankton communities are closely related to river alterations and biogeochemical processes in freshwater reservoirs. Affected by reservoir regulation and hydrological variation, regulated rivers can create distinctive patterns in bacterioplankton communities. In this study, we conducted 16S rRNA V4 amplicon high-throughput sequencing to investigate compositional changes in the bacterioplankton community and its environmental responses to damming effects in the Pengxi River, the largest tributary on the northern bank of the Three Gorges Reservoir (TGR). The bacterial community was dominated by the phyla Proteobacteria and Actinobacteria, accounting for 51.0% and 13.1% of all sequences, respectively. Distinct differences in the bacterioplankton community composition were observed between the backwater and riverine areas, and the dominant taxa showed clear shifts at the class level between the upper stream and backwater area sites along the Pengxi River. Conductivity, transparency and temperature were considered the major environmental factors driving the bacterioplankton composition variation. Additionally, the functional profiles of the bacterioplankton community corresponded with compositional changes in reservoir regulation by TGR. Therefore, these results provide insights into dam effects on the bacterioplankton community in the Pengxi River, and further research should focus on the potential ecological processes of river regulation by dams or reservoirs.

Interval estimation of landslide displacement prediction is significant for landslide early warning. The goal of this paper is to improve the accuracy of landslide displacement point prediction and quantify the uncertainties associated with the predicted values. To do so, a coupling prediction model based on double moving average (DMA) method and long short-term memory (LSTM) network is investigated. The DMA method is employed to decompose cumulative displacement of landslide into trend and periodic displacements, while the LSTM network is adopted to model and predict these two sub dis-placements. The sum of predicted sub displacements is considered as predicted cumulative displacement. Further, the probability estimation theory is utilized to derive confidence intervals that quantify the uncertainties of the point prediction. The proposed approach was validated on Baishuihe landslide in Three Gorges Reservoir area of China. Results show that the LSTM network performs better than support vector machine and Elman network, while the DMA decomposition method outperforms single moving average method. As a consequence, the coupling prediction model of DMA and LSTM network is a better solution for the point prediction of landslide displacement. Furthermore, the proposed probability estimation method can construct high-quality confidence intervals.

Body size is sensitive to environmental changes and one of the fundamental traits linking ecological functions. Size structure has been suggested as a useful indicator for environmental monitoring and assessment in aquatic ecosystems. However, the organisms’ size structure and the relationship with environmental factors remain seldom addressed in reservoir ecosystems. In this study, we investigated the size spectrum, size diversity of the zooplankton and their relationships with environmental conditions across nitrogen and phosphorus gradients in the Xiangxi Bay of Three Gorges Reservoir, China. We further tested the hypotheses that how nutrient and water temperature affect zooplankton size structure: nutrients indirectly affect zooplankton size spectrum and size diversity via phytoplankton (H1); increasing water temperature will reduce size diversity and result in a steeper size spectrum (H2); size diversity is a more robust metric indicating environment changes than the size spectrum in high dynamic ecosystems (H3). We found that both the size spectrum and size diversity showed high spatiotemporal dynamics. The size spectrum ranged from −3.373 to −0.984. The size diversity ranged from 0.631 to 3.291. Spatially, the lowest values of the size spectrum and size diversity were observed in the upstream areas of Xiangxi Bay, where nitrogen and phosphorus concentrations are high and low, respectively. And in temporal dynamics, lower values of the size spectrum and size diversity were generally observed in March and April. Further analyses based on the structural equation model (SEM) found a clear pathway revealing that nutrient variables affect the zooplankton abundance and size structure, supporting hypothesis H1. That is, dissolved inorganic nitrogen had an indirect effect on the zooplankton abundance, size spectrum, and size diversity by influencing the concentration of phytoplankton chlorophyll a. In addition, results of SEM suggested that increased water temperature had a significant negative effect on the size diversity but had non-significant effects on zooplankton abundance and size spectrum. This finding suggests that size diversity is a reliable and useful index in measuring the zooplankton size structure in reservoir ecosystems with high dynamics, which may have a wide application in environmental monitoring and assessment, especially for complex and dynamic aquatic ecosystems.

The non-point source (NPS) pollution has become an important limitation to the sustainable development of the Three Gorges Reservoir Area (TGRA) water resources. NPS load estimation research has theoretical and realistic significance for water environment security and water pollution control. Therefore, the TGRA was chosen to be the study area, and the export coefficients of different land-use type were calculated through literature consultation method combined with improved observation experiment. The load of total nitrogen (TN) and total phosphorus (TP) of NPS from different pollution sources including farmland, decentralized livestock and poultry breeding and domestic pollution sources were estimated. The results are shown as follows: the order of TN load of different sources in the TGRA from high to low was land use, livestock and poultry breeding, rural life; the TN from land use was 372% higher than that of rural; the order of TP load of different sources in the TGRA from high to low was livestock and poultry breeding, rural life, land use; the TP from livestock and poultry breeding was 114.5% higher than that of land use. Therefore, control of livestock and poultry sewage discharges was the key practice to limit the TP loss, while the optimization of agricultural management was the key practice to control the loss of TN. HIGHLIGHTS In this study, the TN and TP loads of NPS pollution of TGRA based on ECM in 2010 were estimated.; The export coefficients of different sources were determined by field observation and literature consultation.

Since the impoundment of the Three Gorges Reservoir area in 2003, the potential risks of geological disasters in the reservoir area have increased significantly, among which the hidden dangers of landslides are particularly prominent. To reduce casualties and damage, efficient and precise landslide susceptibility evaluation methods are important. Multiple ensemble models have been used to evaluate the susceptibility of the upper part of Badong County to landslides. In this study, EasyEnsemble technology was used to solve the imbalance between landslide and nonlandslide sample data. The extracted evaluation factors were input into three bagging, boosting, and stacking ensemble models for training, and landslide susceptibility mapping (LSM) was drawn. According to the importance analysis, the important factors affecting the occurrence of landslides are altitude, terrain surface texture (TST), distance to residences, distance to rivers and land use. The influences of different grid sizes on the susceptibility results were compared, and a larger grid was found to lead to the overfitting of the prediction results. Therefore, a 30 m grid was selected as the evaluation unit. The accuracy, area under the curve (AUC), recall rate, test set precision, and kappa coefficient of a multi-grained cascade forest (gcForest) model with the stacking method were 0.958, 0.991, 0.965, 0.946, and 0.91, respectively, which a significantly better than the values produced by the other models.

The Zigui Basin in the Three Gorges area is a syncline running in the north-south axial direction; the sediments in the basin are mainly late Triassic-late Jurassic sandy and argillaceous rocks. Since the Three Gorges Project began undergoing impoundment in May 2003, nearly 20,000 mini-earthquakes have occurred in the Zigui–Badong region, including five earthquakes with magnitudes greater than Ms 5.0. Herein, a 3D gravity inversion method was introduced to investigate the density structure of the Zigui Basin and its adjacent areas. A comprehensive analysis of the geological structure of the area was carried out, based on focal mechanism solutions of six moderate–strong earthquakes in the area. The Zigui Basin is a low–density area from the periphery, and the sediment in the east is thicker but less dense than in the west. The shallow part of the Zigui Basin is a weak bottom layer prone to slippage, and the deep part (5–10 km) could comprise lithological strata such as limestone, sandstone, and shale, which easily undergo dissolution by leaking reservoir water. Under the action of external forces such as long-term infiltration and unloading of reservoir water, fissures will expand and squeeze then earthquakes are likely induced in the deep strata. Furthermore, new buried faults in the western and southeastern edges of the core area of the Zigui Basin could also trigger an earthquake under long–term pressurization and reservoir water penetration.

Water temperature, as one of the important water environment impact factors, has a significant impact on the survival and development of aquatic organisms. We selected water temperature data (1959–2017) from four key hydrological stations in the Yangtze River: Cuntan, Yichang, Hankou, and Datong. We analyzed the characteristics and variability of the Yangtze River hydrothermal regime by the Mann-Kendall method, wavelet analysis, and by the IHA-RVA method to analyze hydrothermal regime variations of the Yangtze River, and the response mechanisms of fish to variations in hydrothermal regimes were explored. The results show that (1) The annual average water temperature of the Yangtze River is warming, and Cuntan Station, Yichang Station, Hankou Station, and Datong Station have a sudden increase in temperature in 2002, 1995, 2003, and 2004, and the periodicity analysis demonstrates that Cuntan, Yichang, and Datong stations all have main periods of 24~32 years, (2) The overall variations of 32 hydrothermal indicators at Cuntan Station and Yichang Station reached 65% and 61%, which are close to the height variation, (3) With the construction of the Three Gorges Dam, the stagnant cooling effect caused the arrival date of the upper reproduction water temperature of “The four major fish species” to be delayed by about 23 days, and the stagnant heat effect caused the arrival date of the Chinese sturgeon reproduction upper limit water temperature to be delayed by about 30 days.

Excessive reclamation and improper use of agrochemicals in karst areas leads to serious non-point source pollution, which is of great concern and needs to be controlled, since contaminants can easily pollute groundwater due to the thin patchy soil and developed karst structures. The occurrences of organochlorine pesticides (OCPs) in karst soil were investigated by analyzing 25 OCPs in the karst soils near the Three Gorges Dam, China. The total concentrations of OCPs ranged 161–43,100 (6410 ± 9620) pg/g, with the most abundant compounds being p,p’-DDT and mirex. The concentration differences between the orchard and vegetable field and between upstream and downstream presented the influences of land-use type and water transport on the OCP spatial distributions. Composition analysis indicated the possible fresh inputs of lindane, technical DDT, aldrin, endrin, mirex, and methoxychlor. Their illegal uses implied an insufficient agrochemical management system in undeveloped karst areas. Principal component analysis with multiple linear regression analysis characterized the dominant sources from current agricultural use and current veterinary use in the study area. OCPs in the soils might not pose significant cancer risk for the residents, but they need to be controlled due to their illegal uses and bioaccumulation effect via the food chain.

Faults or joints widely exist in rock masses, which deeply affect the mechanical properties of rock. The seismic frequency of the Gaoqiao fault and its surrounding areas in the Three Gorges Reservoir area before and after water storage is significantly higher than that in other areas. In this study, a curved joint is used to simulate the occurrence characteristics of the Gaoqiao fault, and the influence of reservoir water is simulated by adjusting the fracture water pressure. Compared with the changes of joint surface morphology parameters before and after the test, it is found that the macro failure characteristics of rock samples are in good agreement with the micromorphology changes of the joint surface. Among them, the parameters such as root-mean-square height (Sq), arithmetic mean height (Sa), reverse load area ratio (Smc), and minimum autocorrelation length (Sal) can better characterize the joint surface deterioration of rock samples under the action of fracture water pressure. The test results have a certain reference value for studying the fault response under the action of reservoir water.

China is one of the countries with the most serious geological disasters in the world (Wang et al.,.Landslides 1:157–162, 2004; Keqiang et al.,.Environ Geol 55:55–63, 2008; Li et al., Environ Earth Sci 60:677–687, 2010; Du et al.,.Landslides 10:203–218, 2013). In some cases, landslides can cause huge losses in human lives and properties as well as impose significant impacts on the environment (Yin et al.,.Landslides 7:339–349, 2010; Zhang et al., Front Struct Civ Eng 14:1247–1261, 2020a). Specially, due to the complex geological conditions associated with high mountain areas and intensive human engineering activities, landslides occur frequently in the Three Gorges Reservoir (TGR) region, where steep slopes exist and flooding often occurs (Xu and Niu,.Comput Geosci 111:87–96, 2018; Xie et al.,.IEEE Access 7:54,305–54,311, 2019).

Extreme hourly precipitation is amongst the most prominent driving factors of flash floods and geological disasters. Based on the hourly precipitation data of 35 stations in the Three Gorges Reservoir Region (TGRR) from 1998 to 2020, we analyzed the spatiotemporal variation characteristics of hourly extreme precipitation indexes. The selected indicators included the frequency, intensity, period, annual maximum, trend of hourly heavy precipitation (20–50 mm/h) and hourly extreme heavy precipitation (≥50 mm/h) in the TGRR. Closely related climatic factors such as the Western Pacific Subtropical High Intensity (WPSHI) were also discussed. The results showed that in 2010–2020, the cumulative frequency of heavy precipitation magnitude between 25 and 40 mm/h slightly increased, while the corresponding frequency for magnitudes ≥50 mm/h decreased. In summer, the frequency of both heavy and extreme heavy precipitation increased in June and decreased in August, indicating a shift of extreme events to an earlier time in the flood season. The cumulative frequency of heavy precipitation in July had a period of about 7a, and that of extreme heavy precipitation had a period of 3a. The annual average intensity of heavy precipitation and extreme heavy precipitation in the TGRR was 28.9 mm/h and 61.4 mm/h per station, respectively, and both fluctuated and insignificantly decreased from 1998 to 2020. The annual maximum hourly precipitation center in the TGRR moved downstream from west to northeast. The frequency of heavy precipitation was relatively small along the main stream of the river valley. Both the frequency and total amount of heavy precipitation in southeast of the TGRR were significantly higher than those in other regions. Heavy precipitation in the majority of stations with high elevation (higher than 500 m) showed a decreasing trend. The cumulative frequency of precipitation with an intensity of 20–50 mm/h was closely correlated with the Western Hemisphere Warm Pool (WHWP) Index in February and the WPSHI Index in January, and especially, the abnormal large annual frequency (top 20%) showed strong correlation with the two indexes, implying highly predictable factors for extreme events. The frequency of precipitation intensity above 50 mm/h was correlated with the Western Pacific Warm Pool (WPWP) Area Index in January and the WPWP Intensity Index in November of last year. The research results provide a strong and refined factual basis for the assessment and prediction of extreme precipitation, and for disaster prevention and mitigation, in the TGRR.