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This paper analyzes agricultural pathways and the impacts of land requisition from dam construction in a Catholic community in Tibetan Southwest China. Cizhong Village is unique for its Catholic religion and unique agroecology of growing paddy rice and grapes for household winemaking, one of the very few ethnic Tibetan communities to do so. This unique agriculture is due to the community being located at the boundary between two larger culinary/agricultural spheres, rice boiling, and wheat grinding peoples. The situation has changed with a construction of a large dam, which caused another community to be moved on top of the village's paddy fields. In the context of this issue on food politics, the paper also highlights the ways in which new global forces related to infrastructure (dam building), are disabling unique interfacing forms of self-sufficient food production, leading to emotional responses among rural farming communities. [ABSTRACT FROM AUTHOR]

In high dam construction projects in China, stilling basin design with an abrupt bottom drop is sometimes introduced to reduce the bottom velocity and pressure loads by generating A-type hydraulic jumps. Although the stilling basin design is not new, A-type hydraulic jumps have not been studied taking into account the air entrainment and evolution of internal air–water flow structures. This paper presents an experimental study of self-aerated A-type jumps in terms of bubble transport and free-surface fluctuations over the bottom drop. Four Froude numbers from 4.1 to 10.3 are tested for three drop heights, in addition to the flat-bottom case. Compared to the classic hydraulic jumps, A-jumps are observed with longer jump lengths and weaker free-surface fluctuations. The downward deflection of the jet-shear flow and formation of a bottom roller in the step cavity require a modification to the analytical expression of velocity and void fraction distributions. The relationship between the bubble diffusivity and jump spreading rate differs from that in classic hydraulic jumps, suggesting a faster expansion of the bubble diffusion layer than the turbulent shear flow downstream of the drop, especially for large drop heights. At large approach velocities, the reattachment of the deflected jet-shear flow to the lowered bed may cause a local rise in bubble counts downstream the bottom roller. Further increase in drop height results in a W-jump with overwhelming bottom roller over the surface roller and an arced surface jet, which is beyond the scope of this study. [ABSTRACT FROM AUTHOR]

The instability of dams will bring immeasurable personal and property losses to the downstream, so it has always been a trendy topic worthy of investigation. Currently, the rigid body limit equilibrium method is the most commonly used method for the dynamic stability analysis of dams. However, under the action of earthquakes, the instability of the integral dam-foundation system threatens the safety of the dams and is of great concern. In this paper, a stability analysis method that can reflect the complex geological structural forms of dam foundations is proposed in this paper. The advantages are that this method deals with the difficulty in assuming sliding surfaces and the lack of quantitative criteria for the dynamic instability analysis of dams with complex geological structural forms of dam foundations. In addition, through the method, the sliding channels that may appear in the dam foundations can be automatically searched under random earthquake action, and the safety factors of the dynamic instability of dams be quantitatively obtained. Taking a high RCC gravity dam under construction in China as an example, the proposed method is applied to the three-dimensional finite element model of the dam-foundation system of this dam, and then the dynamic stability calculation is carried out. Through this method, the formation process of the dam foundation's plastic zone and the failure of sliding channels with different strength reduction coefficients are studied on and analyzed detailedly, and the quantitative acquisition of the safety factors is realized. The results show that the method is reasonable and feasible, and helps provide a new idea and method for the dynamic stability analysis of dams. [ABSTRACT FROM AUTHOR]

The issue of dam type selection is a prevalent challenge in water resource allocation engineering. The site of the Y2 dam in China is suitable for building concrete arch dams and roller-compacted concrete (RCC) gravity dams. To determine which dam type is better in terms of construction progress, this paper proposes a multiattribute decision-making method based on construction simulation. First, the construction characteristics of concrete dams are analyzed, and the construction simulation systems for arch dams and gravity dams are developed based on construction simulation theory. Then, for each dam type, the initial construction schemes are used as the input of the simulation systems, and attribute values of construction progress are output. Secondly, a multiattribute decision-making method is used to select the typical scheme of each dam type from these initial schemes. Finally, the simulation results of the typical schemes for the arch dam and the RCC gravity dam are compared, to determine the optimal dam type for the Y2 dam. The results show that for the Y2 dam, the construction period of the arch dam is 34 months, and that of the RCC gravity dam is 28 months. From the perspective of construction progress, the Y2 dam type should select the RCC gravity dam. Compared with similar dams that have been built, it is concluded that the simulated progress result conforms to the current actual construction level, which also verifies the correctness of the calculation results and the reliability of the construction simulation. [ABSTRACT FROM AUTHOR]

In China, there are more than 12,000 tailings ponds, and the number is still growing. With the rapidly increasing number of tailings ponds, the safety issue has drawn more and more attention by governments and local communities. The design and construction of each tailings pond must meet the specific requirements of a particular mining project and the changing conditions with time. This paper presents a case study of the Dahongshan Longdu tailings pond which combined upstream and centerline methods for dam construction. The Dahongshan Copper Mine and Iron Mine were facing a challenge of the disposal of increased production of tailings. The current upstream method of dam construction could no longer guarantee its safety. Therefore, the original design of tailings pond should be revised for the safety of the tailings pond. This tailings dam used centerline method for subsequent construction after total height of this dam was constructed up to 100 m by upstream method. This tailings pond initially used upstream method for the dam construction. To pile up the increased production of tailings, the dam construction method was switched to centerline method after dam height of 100 m. Numerical simulation was performed to analyze the seepage and displacement fields, stability and storage capability of the tailings dams constructed by upstream and mixed methods, respectively. Through the simulated results, the mixed method was demonstrated to be more beneficial to the practical safety management of this tailings pond than the upstream method. [ABSTRACT FROM AUTHOR]

The risk management of cascade reservoir systems (CRSs) is a major public challenge, and the establishment of risk criteria is critical to solving this issue. In this paper, an approach is presented to establish risk criteria of for CRSs in China based on statistical data (reservoir dam break accidents; fatalities due to reservoir dam breaks; the construction date of defective reservoirs; and the current situation of CRSs), F–N curves, F–E curves, F–I curves, and the as low as reasonably practicable (ALARP) principle. This paper has some innovations in the following aspects. First, the characteristics of CRSs are revealed for the first time. Second, risk criteria for CRSs are suggested. Third, the engineering safety level, risk exposure level, and risk level of CRSs in China are determined. The research results of this paper provide abundant information for the operation management, maintenance and reinforcement of CRSs in China. [ABSTRACT FROM AUTHOR]

Dams have proliferated along the Mekong, spurred by energy demands from economic development and capital from private companies. Swift dam evolution has rendered many databases outdated, in which mismatches arise from differing compilation methods. Without a comprehensive database, up-to-date spatial assessment of dam growth is unavailable. Looking at future development, hydropower potential specifically within the Mekong remains to be systematically evaluated. In this paper, we offer (1) an open-access and unified database of 1,055 dams, (2) a spatiotemporal analysis of dams on a sub-basin and country level from the 1980s to the post-2020s, and (3) a grid-based assessment of the theoretical basin-wide hydropower potential, using present-day discharge from the CaMa-Flood model (2011-2015, 0.05 degree), and future discharge from the WaterGAP2 model used for ISIMIP2b (2021-2030, 0.5 degree). The dam count of 1,055 is more than twice the largest existing database, with 608 hydropower dams generating a boom in hydropower capacity from 1,242 MW in the 1980s to 69,199 MW post-2020s. While China had the largest capacity increase from the 2000s to the 2010s (+16,854 MW), Laos has the most planned dams and the highest projected growth post-2020s (+18,223 MW). Based on present-day discharge, we estimate a basin-wide hydropower potential of 1,334,683 MW, where Laos is the highest at 514,887 MW. Based on future discharge modeled with climate change, hydropower potential could grow to over 2,000,000 MW. Laos and China are the highest at around 900,000 MW each, together forming over 80% of the total potential. Our database facilitates research on dam-induced hydrological and ecological alterations, while spatiotemporal analysis of hydropower capacity could illuminate the complex transboundary electricity trade. Through both spatiotemporal and hydropower potential evaluation, we address the current and future vulnerability of countries to dam construction, highlighting the need for better planning and management in the future hydropower hotspot Laos. The Mekong dam database is publicly available at https://doi.org/10.21979/N9/ACZIJN (Ang et al., 2023). [ABSTRACT FROM AUTHOR]

This paper uses a political ecology approach to unpack the experience of local governments and displaced communities in Sarawak, Malaysia, with Chinese dam construction at the Bakun Hydroelectric Dam. Data for the study was collected over 32 months from 2014 to 2016. The field site offered a unique insight into how recipient countries of aid are also often at the receiving end of domestic politics of donor countries. The paper finds that Chinese and Australian enterprises involved in the dam construction and resettlement of indigenous communities displayed different understandings with regards to social and environmental safeguards, resulting in a dysfunctional handover of the project from Australian to Chinese leadership. Consequently, indigenous communities were dispossessed from their land, affecting their ability to successfully reconstruct their livelihoods, with their attempts to do so causing further damage to the environment around the reservoir of the dam. [ABSTRACT FROM AUTHOR]

Despite the rapid development of risk analysis, there is a relative absence of risk criteria for dams in developing countries recently, which restrained the practical application of the research results. This paper proposes guidelines for establishing risk criteria of dams in developing countries in considering the coordination of social, economic and engineering factors, then establishes a method of targeted analysis and demonstrates relevant parameters selected according to the ALARP principle and F-N curves, using China as an example. Different individual life risk criteria are established based on different safety levels for existing dams and newly built dams. Social life risk criteria and economic risk criteria are established on the basis of the different safety levels of all size reservoirs, the seriousness of the consequences of accidents, and the acceptability of social risks. The process of establishing risk criteria of dams and the analysis of the parameters demonstrated in this paper are meaningful to provide a reference and promote the required level of management for developing countries. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Three Gorges Dam on the Yangtze River is currently the largest construction project in the world. Because of its complexity, integration of social, environmental and technological systems, and tight coupling required by the schedule, the project should be managed using a systems approach. To find out if this was the case, the authors formed a research team, sponsored by the International Society of Systems Sciences, to tour the dam sight, interview managers and engineers, travel up the Yangtze to Chongqing, analyze problems posed by the critics of the dam and, finally, report back to the ISSS annual meeting in Shanghai following the trip. This paper reports on the team's observations, the results of the interviews and a systems model that analyzes the problems facing the dam builders. Finally, the paper concludes that the engineers and managers are aware of the interrelated problems and have planned for their solution. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

On the basis of research and analysis of the landslide system of the Three Gorges Reservoir area, this paper systematically analyzes and studies the temporal–spatial distribution law of landslides of this reservoir area and their impacts on environment of this area. The paper puts forward that the temporal–spatial distribution of this area's landslides is mainly controlled by lithologic characters of strata, geological structure, valley landscape, and types of bank slope structure; landslide deformation and failure have such characteristics as simultaneity, laggardness, cyclical instability, and stage. Besides, the paper systematically analyzes and studies the main impacts of landslide on environment and points out that landslides and collapses will bring about relatively serious impacts on relocation and layout of cities and towns along the banks. These impacts mainly include the increase of relocation investment, number of migrants, and compensation for losses. Much attention and evaluation should be paid to the impacts of Xintan Landslide and Lianziya Landslide—large landslides near the Dam—on the construction and safety of the Three Gorges Project. However, landslides have relatively small impacts on shipping and reservoir capacity. The above-mentioned research is of great guiding significance for the construction of the Three Georges Project, planning and construction of cities and towns along the banks, and protection of geological environment. [ABSTRACT FROM AUTHOR]

The Three Gorges Project (TGP) is a transcentury project that has aroused world attention. It is expected that the flow velocity and runoff of the Yangtze River will be changed after the project has been accomplished. Consequently, however, the ecological environment in the Yangtze River Basin, particularly in the estuary region, will be affected. Salinity intrusion into the Yangtze River estuary, in general, is mostly affected by the Yangtze River discharge and its external tidal level. This paper focuses on examining the influence of changes in runoff on salinity value. The question, to which should be paid attention is: how is the interaction between changes in runoff of the Yangtze River and salinity distribution in the Yangtze River estuary, China? In this research, a three-dimensional model has been used to identify the effects of runoff change on salinity distribution. The drawn conclusion is that the change of salinity is influenced by discharge variation. Positive and negative impacts of TGP would both turn up but in different period. In sum, TGP is in favor of restraining saltwater intrusion. Nevertheless a suitable method should be found to resolve its negative influences. [ABSTRACT FROM AUTHOR]

System simulation has proved to be an effective tool for planning and improving the performance of a construction process in many successful case studies. However, with the aid of a three dimensional (3D) visualization system, simulation technology will be engaged to its farthest-reaching potential. This paper presents a geographic information system (GIS)-based visual simulation method, in which system simulation techniques are integrated with visualization techniques. The GIS-based visual simulation system (GVSS) was developed by the authors. The GVSS is a simulation tool offering powerful planning, visualizing, and querying capabilities that facilitate the detection of logic errors in simulation models. The software also helps to understand the comprehensively complex modeled construction process, and is capable of organizing vast amounts of spatial and nonspatial data involved in simulation. A hydroelectric project, which will take place on the Yellow River in the northwest of China, is used as an example. An optimum equipment set scheme is determined by simulating a variety of scenarios taking place under different construction conditions. Likewise, other parameters, such as the construction sequence of dam blocks, the monthly intensity of the concrete process, and the construction appearance at the middle and end of each year, are obtained. Meanwhile, the complex processes of dam construction are demonstrated dynamically using 3D animation, which provides a powerful tool for quickly and comprehensively understanding the whole construction process. The GVSS has proven to be a helpful and useful tool for the design and management of concrete dams. [ABSTRACT FROM AUTHOR]

A rock-filled concrete (RFC) dam is an original dam construction technology invented in China nearly 20 years ago. The technology has been continuously improved and innovated upon, and the accumulated rich practical experience gradually formed a complete dam design and construction technology. Seismic design is a key design area for RFC dams that still requires more investigation; therefore, this article attempts to address some questions in this area. In the article, the seismic design for a curved gravity dam, currently under construction, is compared for RFC and conventional vibrating concrete (CVC) dam alternatives based on American design documents. The conclusions drawn from investigations include the following: The displacement and stress distributions in both the CVC and RFC alternatives are similar, but the maximum computed values for the RFC dam model are slightly smaller than those for the CVC one, while the sliding resistance of both dam alternatives can meet the requirements of the specifications. Regarding the nonlinear seismic analysis results, the extent of damage in the RFC dam model is significantly reduced when compared with the CVC model, which can be explained by the higher cracking resistance of RFC. In general, the seismic performance of the investigated dam made of RFC appears to be better than that of CVC. [ABSTRACT FROM AUTHOR]

Water temperature is an important habitat factor in river ecosystems that exhibits the characteristics of continuous change. Dam construction disrupts the continuity of river water temperature and reset it, thus exerting sharp rise/decrease on the characteristics of water temperature change. The effect of a dam on river continuity is directly related to the dam size. To explain this relationship, two rivers in China were selected: one river without reservoirs and one river with cascade reservoirs. Through the analysis of the longitudinal change of water temperature in free‐flowing rivers, we found that water temperature changes continuously and steadily in the longitudinal direction. Based on this, a temperature trend hypothesis in river was proposed, and the discontinuity of the water temperature in the reservoir section was evaluated. The results are as follows: (1) In mixed reservoirs, river water temperature remained as continuous as free‐flowing rivers. However, the river water temperature had a large discontinuity in the stratified reservoir. (2) Water residence time was used as an indicator of the continuity of reservoir water temperature. (3) Selective withdrawal of stratified reservoirs in January could not remove the discontinuity caused by itself, but it worked in June. [ABSTRACT FROM AUTHOR]

Dongping Lake is an important regulator for the Eastern Route of South-to-North Water Diversion Project in China, and the water quality assurance of it is of great importance. To investigate the distribution characteristics and burial process of phosphorus (P) in Dongping Lake as well as their relationship with regional economic development and human activities, 33 spatially distributed surface sediment samples and one lake sediment core were extracted from Dongping Lake. A harmonized procedure for the P forms in freshwater sediments developed by the European Programme, Standards, Measurements, and Testing was used in this paper. The results show that NaOH-P (P bound to Al, Fe, Mn oxides or hydroxides), HCl-P (Ca-bound P), inorganic phosphorus (IP), organic phosphorus (OP), and total phosphorus (TP) in the surface sediments show a strong spatial variability. The highest NaOH-P and OP concentrations were observed in the eastern and south-eastern region of the lake and decreased gradually away from the mouth area of Dawen River. We deduced that anthropogenic input via the Dawen River is the main contributor. The higher concentration of HCl-P occurred in the north-west region of the lake and increased in a gradient away from the mouth area of Dawen River, and this pattern of distribution could be related to grain-size effects and higher transport energies close to riverine inlets. Pollution reflected by phosphorus in the core sediments of Dongping Lake is well consistent with the economic development history of Dongping County. From the beginning of the 20th century to the middle 1970s, the concentrations of each P speciation did not vary largely and runoff of the Yellow River mainly contributed to the P accumulation in the sediment, which might reflect the background values of them in the lake in pre-industrial period. The stable Mz (mean grain size), low loss-on-ignition (LOI), and high sedimentary flux also support this. The rapid increase of NaOH-P and OP at 10-0 cm (especially 5-0 cm) indicates the enhancing anthropogenic eutrophication since the middle 1970s. The LOI peak period and a coarsening of particle size also support this interpretation. However, the decreasing of TP and HCl-P was attributed to the change in sediment supply. As due to construction of dams around the lake, runoff of the Dawen River mainly contributed to the P accumulation in the sediment during this period. [ABSTRACT FROM AUTHOR]

[Display omitted] • We quantified the impacts of land use changes and dam construction on flood regulation service (FRS). • A transfer matrix of ecosystem FRS was developed associating with land use changes. • Both the amount and direction of land use changes play key roles in influencing the ecosystem FRS. • Land use outweighted dams in forming the annual FRS supplies. • Increases in FRS supply came more from dam construction (84.65%) than land use changes (15.35%). Flood regulation service (FRS) is essential for a sustainable landscape and human society. It is not only subject to land use changes, but also affected by engineered measures (e.g., dam construction). However, the comprehensive impacts of the two major driving factors are still to be elucidated. To fill the research gap, this paper aims to evaluate the response of basin-scale FRS supply and demand to land use changes and dam construction. A case study in the Yangtze River Basin, China, shows that the 2020 FRS supply is mainly from land uses (84.85%) rather than dams (15.15%), with the biggest contributions from water bodies (rivers and lakes, 30.00%) and forests (29.35%). Between 1980 and 2020, the total FRS supply has increased by 10.50%, from 1.48 × 1010 m3 to 1.64 × 1010 m3. The net increase mainly comes from dam construction (84.65%) rather than land use changes (15.35%). Regarding the land use changes, the developed transfer matrix shows the ecosystem FRS flows and indicates that both the land use change amount and direction play a key role, e.g., the declines in farmlands have increased ecosystem FRS supplies when transiting into forest lands (by 3.68 × 108 m3) and water bodies (by 1.37 × 109 m3), while have decreased the ecosystem FRS supplies by −1.96 × 107 m3 with the transition into construction lands. These findings could shed light on the divergent roles between land-based measures and engineered measures in managing flood risk. [ABSTRACT FROM AUTHOR]

The western region of China is rich in hydropower resources and characterized by unique geological conditions. For the construction or planned construction of high dams in this region, different types of cover layers are formed due to special geological structures, most of which are located in high seismic intensity zones. This study focuses on four different site conditions: hard ground, medium–hard ground, medium–soft ground, and weak ground. By simulating the dynamic response of concrete-face rockfill dams under near-fault earthquake excitation, the vertical settlement of the dam and the attenuation of seismic motion under different site conditions are analyzed. The research findings reveal a consistent trend where the vertical settlement of the dams progressively escalates with increasing dam height across all four site conditions. This settlement phenomenon is especially pronounced in weak ground conditions, posing a potential risk of failure. Furthermore, when subjected to near-fault pulse-type earthquake motions, the existence of weak soil layers significantly dampens the seismic forces experienced by the dam. This finding suggests that the weaker the geological conditions of the site, the more pronounced the attenuation effect of the seismic motion. Additionally, the overburden layers have a noticeable amplification effect on near-fault pulse-type earthquake motion. However, this amplification effect is not significant in weak ground, possibly due to the presence of weak soil layers restricting the propagation and amplification of seismic motion. In conclusion, these research findings have practical significance for the dynamic response of high dam construction in different site conditions in the western region of China. They provide a scientific basis for the design and construction of high dams and serve as a reference for the implementation of seismic mitigation measures and earthquake disaster prevention in engineering projects. [ABSTRACT FROM AUTHOR]

The flow regime of the Yangtze River (Changjiang) has been altered to some extent by intensified human activities over the past decades, particularly dam construction. To assess the impacts of dam building on the flow regime in the Yangtze River, two of the largest reservoirs on the upper reach, i.e., the Gezhouba and Three Gorges reservoirs, have been selected as case study sites. To analyze the changes in flow regime between predam and postdam periods, the whole study period was divided into three subperiods according to the years when these two reservoirs started to store water. On the basis of the time series of daily flow discharge from four key hydrological stations, i.e., Cuntan, Yichang, Hankou, and Datong, the alterations in annual, seasonal, monthly, and daily flow regimes and water rising or falling regime in different subperiods were investigated and the driving forces were explored. The results revealed the impacts of the two reservoirs on their downstream flow regime varied with reservoir storage capacity and the distance between the target reservoir and the case study site, the Gezhouba and Three Gorges reservoirs imposed various impacts on different time scales of downstream runoff regime, and the operation of these two reservoirs altered the water rising and falling regime to some degree, which is particularly critical for the spawning of Chinese sturgeon and the four major domestic carp. The output of the paper could provide references for the assessment of impacts of dam construction on the health and stability of the Yangtze River ecosystem. [ABSTRACT FROM AUTHOR]

Big cities are often said to have big water problems, and Shanghai is no exception. In this paper, we examine and compare the influence of the major factors that give rise to the risk of water insecurity in Shanghai. There is an extensive and diverse literature on these issues, dealt with in isolation, and here, we provide a synthesis of the literature, together with our own assessments and calculations, to assess what are the risks to Shanghai's water supply and what is our degree of confidence in this assessment. We describe the systems that supply water to the city, and past and future changes in the systems, including changes in the glaciers that supply some water to the river, changes in climate, changes in land use, the construction of dams, and water diversions. We show how, at the same time as Shanghai is increasing its dependence on the Yangtze river, water diversions and sea level rise are increasing the risk that this water will be too saline to consume at certain times of the year. This analysis suggests that most of the major drivers of the risk to water security in Shanghai are within the power of environmental managers to control. [ABSTRACT FROM AUTHOR]

This paper presents an evaluation of the spatio-temporal patterns of hydrologic alteration induced by dam construction and precipitation variability in the Lancang River Basin of southwest China from 1957 to 2000. Analyses were conducted using the linear regression method, the Mann-Kendall test, and the Range of Variability Approach. The results indicate that there was considerable variation in the average monthly precipitation between the pre- and post-dam periods in the Lancang River Basin. Second, the magnitude of monthly runoff was strongly related to precipitation, which showed an up-down annual variation, and was significantly altered by dam construction and precipitation variability. In the modified series (hydrologic series with the precipitation impacts removed), runoff deviations between the pre- and post-dam periods became larger. Third, the extreme runoff cycles were influenced by dam construction and precipitation variability downstream from the dam, and the monthly maximum runoff increased from the pre-dam to post-dam period at all hydrologic stations. Fourth, the degree of hydrologic alteration (DHA) indicates that the precipitation variability not only affected the hydrologic regime of unregulated river reach but also modified the negative impacts of dam construction, which could provide a modest mitigation of the hydrologic alterations induced by dam construction, possibly decreasing the level of DHA. Last, the overall degree of hydrologic alteration in the observed series reached 25.2, 25.3, and 29.1 % for the upstream, midstream, and downstream areas, respectively. These results show that the hydrologic regimes of the Lancang River during the 1957-2000 period were affected by damming and precipitation variability, but the hydrologic alteration was relatively low in the upstream areas of the river without a dam. [ABSTRACT FROM AUTHOR]

The impoundment of the Three Gorges Dam (TGD) has disturbed the hydrological regime downstream and has directly affected the relationship between the Yangtze River and Dongting Lake. To trace the realistic and potential impacts, this paper examined the changes of the channel morphology and sedimentology caused by the TGD through a field survey on the channel cross-sections and then analyzed the impact on lake water level through BP neural networks. The possible impacts on inundation patterns in lake wetlands were studied based on the lake basin DEM. The results indicate that drastic sediment decline and severe channel erosion are putting considerable pressure on the river and lake. Changing river channels are evident in some monitoring cross-sections. Dongting Lake, for the first time, changed from trapping to supplying net sediment to the Yangtze River. During the water storage periods of the TGD, the water level decreased 2.03 m in 2006 and 2.11 m in 2009 at the outlet of the lake, with extreme decreases up to 3.30 m and 3.02 m, respectively. These changes have inevitably induced alterations in the inundation patterns of the lake wetlands, which in turn have disturbed the ecological function of lake wetlands as habitats for both migratory birds and aquatic fish. The serious droughts in Dongting Lake recent years were largely connected with the above changes. Therefore, proper attention should be paid to this occurrence. [ABSTRACT FROM AUTHOR]

On 19 May 2011, the State Council released a statement vowing to overcome ‘issues’ created by the now completed Three Gorges Dam. Among these was the well-being of those displaced to make way for its construction. In the same statement, the Central Government promised that the displaced would catch up with provincial living standards by 2020. This paper examines some of the residual issues facing the Project region and presents the key components of the new Working Plan. [ABSTRACT FROM AUTHOR]

This paper examines the debates over the decision to build the Three Gorges Dam, the subsequent flows of income to the firms involved in its construction, and the continuing implications of the dam for the Chinese space economy. The paper makes and justifies three claims. First, the construction project has been responsible for both dispossession and the formation of capital (primitive accumulation). But it is too simple to interpret the project as merely the face of modernity or development: proponents were reflecting traditional attitudes to bureaucracy and environmental management, whereas opponents sought liberalisation, marketisation, and opening up. It turns out that the concept of modernity, as a western programme introduced into China after the formation of the People's Republic, is of remarkably little value in understanding the construction of this dam. Secondly, the decision to build the dam reflects both structure and happenstance - particular political events and individuals were critical. Notably, the project shows few signs of having come into being to absorb over-accumulated capital: mega-projects like this do not have to satisfy any capitalist logic. Finally, I emphasise that such huge projects have long run effects on the structure of power in China - indeed, events at Three Gorges underpinned much of the later debate and struggle over dams on the Mekong, Salween, and Changjiang above Three Gorges. [ABSTRACT FROM AUTHOR]

The flood peak and flood volume are generally considered to be independent random variables in early-term dam construction diversion risk simulation, while the cofferdam elevation is a definite value. Due to the continual construction of high dams at the 200 m-level in southwest China, the effect of flooding on dams lasts longer than before due to greater filling volumes and longer construction periods. The correlation between the flood peak and the volume has been shown to affect the accuracy of mid-term diversion risk analysis. Aiming at determining the mid-term diversion risk of high rockfill dams, this paper presents a joint distribution for the construction flood peak and volume using the copula function. Then, a simulation model for the monthly filling height during the flood season is given considering the filling intensity and effective construction days, in which the daily rainfall and the stoppage standards for rain, which affect the effective construction days, were analysed. Additionally, stochastic factors such as the hydrology, hydraulics, stop days, and filling intensity were considered to resolve the diversion risk rate by using the Monte Carlo method. Finally, an example of a high rockfill dam in southwest China was provided to verify the correlation between the flood peaks and volumes and to calculate the mid-term diversion risk during its construction by incorporating historical flood data, rainfall days, and diversion standards. The results reflect the probability distribution of a construction flood more accurately, avoiding the overestimation of a low-probability flood event, with a high peak but a small volume, that leads to a lower risk rate and lower designed reliability for diversion structures. In addition, the monthly diversion risk and its corresponding maximum water level in the equivalent reappearance period can provide design references for coordination between flood prevention measures and construction schedules. [ABSTRACT FROM AUTHOR]

Highlights • Parametric analysis of semi-unbounded foundation models is performed comprehensively. • Nonlinear seismic response of arch dams is affected by the material damping and the simulation size of foundation. • We propose to neglect the material damping of foundation when the wave incident mechanism is used. • The realistic non-uniformity of foundation should be considered in the earthquake response analysis of arch dams. Abstract Simulation of the infinite foundation is a key issue in the seismic response analysis of high dams. This paper studies how the major characteristics of foundation models influence the nonlinear dynamic response of arch dams when the radiation damping effect is taken into account. The nonlinear dynamic responses of the 217 m high Yebatan arch dam under construction in China is performed as a numerical example. Several key factors, including truncated size, material damping and non-uniformity of the foundation, are analyzed comprehensively. The results show that the material damping and the size of the foundation affect the dynamic response of the dam when the incident wave method is used. Neglect of the material damping of the foundation is proposed to solve this problem, and its rationality is verified. In addition, the results show that the realistic non-uniformity of the foundation should be considered in the earthquake response of arch dams. [ABSTRACT FROM AUTHOR]

This paper describes some special features of the Wenchuan earthquake that affected dam safety. Damage and performance of dams, primarily for four dams over 100 m high located in the affected earthquake area, are briefly described. Lessons learned related to dam safety from this devastating earthquake are preliminarily drawn. As the seismic safety of high dams during strong earthquakes has gained more attention around the world, some critical issues related to dam construction in China are considered and extensively discussed. Questions such as "Why is dam construction necessary in earthquake prone countries such as China?", "Can we accurately evaluate the seismic safety of high dams in China?", "Did reservoir impounding of the Zipingpu and Three Gorges Projects trigger the Wenchuan Earthquake in some way?" and "What is the strategic priority of dam safety for large dams in China?" are discussed. Finally, the corresponding tactics with response to the challenge are suggested and recent preliminary progress mainly achieved in IWHR is briefly introduced. [ABSTRACT FROM AUTHOR]

In the Langcang (Upper-Mekong) watershed, degraded watershed ecosystems in upland areas threaten cultivation practices, water resources, and dam development downstream. Assessment of ecosystem services and the factors that threaten them is an important first step to support watershed management. This, however, requires detailed information that is often missing in mountainous regions. To overcome this, in this paper, we adopt a decision tree approach to assess protection, biodiversity, and production services in two mountainous watersheds (Fengqing and Xiaojie) of the Lancang River Basin. Decision tree rules were built on the basis of field surveys, available references, ecosystem maps derived from remote sensing, expert knowledge, basic topographic information, and community interviews. Decision tree results showed that forest cover and agro-forestry practices contribute greatly to improved ecosystem functioning in the Fengqing Catchment compared to the Xiaojie Catchment. The results were consistent with field observations. The decision tree method proved to be a suitable and flexible tool for the rapid assessment of watershed ecosystem services, for highlighting those areas that need more in-depth research, and for guiding watershed and ecosystem management. [ABSTRACT FROM AUTHOR]

Ecological effects of the cascade hydropower dam construction on ecosystems have acquired much concern from scientists with the expanding of dam development scales in the Longitudinal Range-Gorge Region. In the Lancang River region and Yuanjiang River-Red River region of the Longitudinal Range-Gorge Region (LRGR), an index system has been therefore established to assess the current ecological vulnerability and to predict the likely future ecological vulnerability of these two river regions after the dam constructions. Eight cascade hydropower dam construction scenarios have been established in this paper for forecast. Abrupt change characteristics of the ecosystem have been considered in the calculation. Economic benefits like current supply, navigation and tourisms of the dam construction have not been considered in the calculation. The results show that (1) the current ecological vulnerability values of Lancang River region and Yuanjiang River-Red River region are 0.34 and 0.43 respectively, which would rise to 0.90?0.91 and 0.86?0.89 respectively after the joint work of all the planned dams; (2) abrupt change would happen to both the Lancang River region and Yuanjiang River-Red River region in future; (3) interval construction with high human response is recommended for both the Lancang River region and Yuanjiang River-Red River region, after which their likely ecological vulnerability would rise to 0.56?0.62 and 0.42?0.43 respectively. These results provide a reasonable method and theoretical references to assess the ecological effects of dam construction, and also give prewarnings to other mainstreams of the Longitudinal Range-Gorge Region which are being planned to construct cascade hydropower dams. [ABSTRACT FROM AUTHOR]

This paper provides an evaluation of current arrangements made for compensation and resettlement to farmers who will be displaced by the construction of the Three Gorges Project (TGP) on the Yangtze River. Kaixian County is used as a case study. Under present regulations the specific value of peri–urban land is underestimated, neither cash–in–hand arrangements nor land–for–land swaps are adequate. There are other problems. The availability of suitable land for resettlement is scarce and rarely of equivalent quality. The inflexibility of the ‘household responsibility system’ contributes to the problem. It is suggested that some of those facing displacement should be encouraged to accept resettlement in places at considerable distance from their current homes and that a more creative approach should be taken to the issue of compensation to enable people to develop their trade and business skills. [ABSTRACT FROM AUTHOR]

• The ecohydraulic modeling framework is a valuable tool for assessing fish ecology in dammed rivers. • Cascade dam construction could fragment spawning site habitats and reduce fish population abundance in the tailwater zone of the main stream. • Spawning site habitats would improve, leading to an increase in fish population abundance in the backwater zone of tributaries. • The effects of cascade dam construction on endemic fish habitat and population status depend on spawning site location, fish species, and life stages. Cascade dam constructions will alter the habitat of spawning sites and affect fish population in the Lancang River basin. This paper examines the impacts of cascade dam construction on four spawning sites, focusing on two co-distributed and endemic fish species: Schizothorax prenanti and Schizothorax davidi. An ecohydraulic modeling framework that combined hydro-morphodynamic, habitat, and population models was used to investigate changes in habitat quality and fish population under two scenarios: no-dam and with-dam. Fish habitat quality was evaluated using the habitat suitability index, and population fluctuations were assessed by the abundance and density of fish populations at all life stages. The simulation results indicated that cascade dam construction would fragment the spawning site habitat in the tailwater zone of the main stream and result in a decrease in fish population abundance and density. Conversely, spawning site habitats in backwater zone of tributaries would improve, and fish population abundance and density would increase. Additionally, the simulation results showed that the magnitude of fish population variations varied by species and life stages. These results highlight the different responses of spawning site location, fish species, and life stages to dam construction, which can help identify areas of the habitat with higher potential for finer-scale endemic fish conservation and recovery efforts. This study provides a comprehensive framework tool for fish ecological evaluation in dammed rivers, which has the potential to assist decision-makers involved in river ecosystem ecological conservation. [Display omitted] [ABSTRACT FROM AUTHOR]

A number of previous studies have contributed to a better understanding of the thermal impacts of dam-related reservoirs on stream temperature, but very few studies have focused on air temperature, especially at the catchment scale. In addition, due to the lack of quantitative analysis, the identification of the effects of water impoundment on regional air temperature is still lacking. We investigated the impacts of reservoirs on the regional air temperature changes before and after two large dam constructions in the lower Jinsha River located in southwest China, by using a 40 year record of reanalysis data at 90 m resolutions. Furthermore, the long short-term memory (LSTM) model was also employed to construct an impoundment effect on the temperature (IET) index. Research results indicate that compared to the pre-impoundment period (1980–2012), the variations in the air temperature at the catchment scale were reduced during the post-impoundment period (2013–2019). The annual maximum air temperature decreased by 0.4 °C relative to the natural regimes. In contrast, the cumulative effects of dam-related reservoirs increased the annual mean and minimum air temperature by 0.1 °C and 1.0 °C, respectively. Warming effects prevailed during the dry season and in the regions with high elevations, while cooling effects dominated within a 4 km buffer of the reservoirs. Therefore, this study offers important insights about the impacts of anthropogenic impoundments on air temperature changes, which could be useful for policymakers to have a more informed and profound understanding of local climate changes in dammed areas. [ABSTRACT FROM AUTHOR]

The Yangtze River is one of the largest and most important rivers in the world. Over the past several decades, the natural sediment regime of the Yangtze River has been altered by the construction of dams. This paper uses multi-scale entropy analysis to ascertain the impacts of large dams on the complexity of high-frequency suspended sediment dynamics in the Yangtze River system, especially after impoundment of the Three Gorges Dam (TGD). In this study, the complexity of sediment dynamics is quantified by framing it within the context of entropy analysis of time series. Data on daily sediment loads for four stations located in the mainstem are analyzed for the past 60 years. The results indicate that dam construction has reduced the complexity of short-term (1–30 days) variation in sediment dynamics near the structures, but that complexity has actually increased farther downstream. This spatial pattern seems to reflect a filtering effect of the dams on the on the temporal pattern of sediment loads as well as decreased longitudinal connectivity of sediment transfer through the river system, resulting in downstream enhancement of the influence of local sediment inputs by tributaries on sediment dynamics. The TGD has had a substantial impact on the complexity of sediment series in the mainstem of the Yangtze River, especially after it became fully operational. This enhanced impact is attributed to the high trapping efficiency of this dam and its associated large reservoir. The sediment dynamics “signal” becomes more spatially variable after dam construction. This study demonstrates the spatial influence of dams on the high-frequency temporal complexity of sediment regimes and provides valuable information that can be used to guide environmental conservation of the Yangtze River. [ABSTRACT FROM AUTHOR]

The check dam is the most important engineering measure in place for controlling water and preventing soil loss in the gully on the Loess Plateau. This study assesses Jiuyuangou, a typical governance watershed of the Loess Plateau, and studies the influence that the check dam system has on the dynamics of sub-storm floods over different return periods by coupling the one-dimensional hydrodynamic MIKE 11 model with the distributed hydrological MIKE SHE model. This research demonstrates the following: The check dam system significantly reduces a flood's peak flow and total volume in the basin and also increases the flood duration. The former effects are greater than the latter effect. The flood peak's rate of reduction, the flood volume's rate of reduction and the flood duration's rate of increase all increase linearly as the number of check dams increase. Of all dam systems, the check dam has the best linear response to a flood peak's rate of reduction. The check dam system reduces the flow rate of flood runoff in the basin. After the dam is built, the average flow rate in the basin decreases by 54%. The runoff velocity of the flood is reduced by different degrees over different return periods and the average peak value decreases compared with a scenario lacking any kind of dam. The check dams have a greater impact on the runoff velocity over a shorter return period, with the velocity being 58.56% slower. Finally, the check dam system significantly reduces the intensity of erosion in the middle and lower reaches of the watershed, and it changes the distribution of the intensity compared to the original channel runoff. These findings are expected to provide a scientific basis for guiding the construction and high-quality development of check dams on the Loess Plateau. In addition, check dam construction in basins can trap water, sediment and nutrients, and it can also contribute to ecosystem diversity and maintaining ecosystem imbalances around the world. [ABSTRACT FROM AUTHOR]

In order to safely and efficiently use soft rock aggregate cemented dams in red bed regions and promote the development of widely sourced cemented sand and gravel dam materials, the Jinjigou project in China applied soft rock for the first time in the construction of cemented material dams. This article further explores the concept of cemented material dams from conducting on-site direct shear tests and research on soft rock material ratios and explores and invents a new structure and construction method by combining soft rock cemented sand and gravel with cemented rockfill. This article also proposes a digital mixing and intelligent dynamic control method for cemented material dams with soft rock. The research results show that soft rock aggregate content not exceeding 60% can produce soft rock cemented gravel with a compressive strength of no less than 6 MPa. The stress on the dam body is small and does not produce tensile stress. The dam body with added soft rock has certain shear-bearing capacity, with a shear friction coefficient of 0.99~1.10 MPa, cohesion of 0.26~0.53 MPa, and high residual strength, accounting for 60~80% of the peak strength. At the same time, the problems of large fluctuations in moisture content and the uneven grading of the soft rock and riverbed gravel mix during the mixing and production process, and the significant influence on safety caused by the large strength dispersion of the cemented sand and gravel, are resolved, ensuring the quality of soft rock cemented sand and gravel preparation. The successful application of soft rock cemented material dams in Jinjigou has achieved a breakthrough in key technologies for soft rock cemented dam construction in red bed regions, proving the feasibility of soft rock cemented material dam construction and having broad prospects for application and promotion. [ABSTRACT FROM AUTHOR]

How to accurately determine the mechanical parameters of rockfill is one of the key issues of concrete-face rockfill dams. Parameter back-analysis using internal or external monitoring data has been proven to be an efficient way to solve this problem. However, traditional internal or external monitoring methods have limitations in efficiency and long-term monitoring. In this paper, the displacement of the Shuibuya concrete-face rockfill dam is monitored by the space-borne Interferometric Synthetic Aperture Radar (InSAR) time series method. Using the InSAR results and the finite element method, the back-analysis of the mechanical parameters of the rockfill dam is investigated, and the back-analysis results of InSAR and levelling are compared. A high correlation of 0.99 for the displacement results generated from InSAR and the levelling offers good agreement between the two methods. The agreement provides confidence that the external InSAR monitoring measurement allows producing a reliable back-analysis and captures the displacement properties of the dam. Based on the identified parameters from the InSAR results, the dam displacement is predicted. The prediction of the maximum settlement of the dam is 2.332 m by the end of 2020, according to the dam displacement characteristics, which agrees well with the results derived from the recorded internal monitoring data. Therefore, the external monitoring results from the InSAR observation can be used as a supplement for traditional monitoring methods to analyse the parameters of the dam. [ABSTRACT FROM AUTHOR]

Due to the excessive exploitation of traditional energy sources, the attention paid to water energy has increased in recent years. As an important means to effectively utilize water energy, reservoirs play an important role in drinking water, irrigation, flood control, and drought resistance. However, utilizing reservoirs often led to water quality issues resulting from the interaction of nutrients and hydrological conditions, especially due to the special structure of karst areas. Because of the change of hydrological conditions by the effect of dam construction, the dynamic of water quality will be more obvious in karst areas with a fast exchange of water and contaminants between underground and surface streams. In the present study, the change in water quality of a karst reservoir, the Muzhu Reservoir in the Houzhai Catchment, was studied. Long-term monitored datasets (1981–2002) and water quality datasets of more recent years were used to assess the effect on the water quality of reservoir expansion from the underground reservoir to the surface reservoir in a karst area. Long-term series datasets had shown that the hydro-chemistry type had been changed from HCO3−·SO42−-Ca2+·Mg2+ type to HCO3−-Ca2+ type in the short term after the reservoir's expansion. The chemical components of water originating from a rock background reduced markedly after the reservoir's expansion, whereas the content of the anthropogenic contribution in the water decreased after the expansion, except in April and May. Isotopic characteristics showed that δ15N-NO3− and δ18O-NO3− values were positively correlated before and after the reservoir expansion, but the slope of the linear regression before the expansion was 0.34, while the slope of the linear regression before the expansion was close to 0.7. This indicated that although denitrification and assimilation may occur simultaneously after the reservoir's expansion, the role of denitrification on nitrate removal decreased, which resulted in nitrate accumulation in the karst reservoir. The results highlighted that nitrate accumulation in karst reservoirs should be monitored to decrease nitrate concentration in the future. [ABSTRACT FROM AUTHOR]

In 2011, Burma/Myanmar one-sidedly halted the billions-worth construction of Myitsone Dam, derailing China's then-largest-ever hydroelectric project abroad and creating a lasting controversy in China–Burma relations. This decision followed an unprecedented public outcry in Burma and a decade of inter-ethnic resistance against this mega-project. This article explores how, throughout the Myitsone Dam controversy, actors at different scales and in three national societies speculated about hidden hostile inter-national plots behind the project or the resistance. Drawing on more than two years of ethnographic fieldwork in 2010–2019, interviews, and media analysis, this article takes seriously many Chinese, Burmese, and Kachin voices – from ambassadors and journalists, to activists and village elders – who claim or dispute various hidden hostile inter-national strategies. The Myitsone case shows how deeply inter-national speculating shapes Burma, often in ways that erase ethnic-minority actors, popular movements, or dispossession. More broadly, it shows how nationalist thinking and competing nationalisms can shape ideas about a frontier of resource extraction. Finally, ethnographic research has often revealed how marginalised people's conspiratorial narratives can reflect realities, but this study suggests using ethnography to let people challenge dominant conspiracy theories about themselves. Researchers across ethnographic disciplines, International Relations, and critical geopolitics face the analytical and ethical challenge of both contextualising and evaluating any people's claim that someone plots against them. [ABSTRACT FROM AUTHOR]

The paper offers a geographical interpretation of the evolving technical, political, and economic intricacy of large dams. It incorporates existing hydropolitical scholarship and the notion of the Chinese Water Machine to reframe dams as assemblages built by specific political, financial and technical processes in particular socioenvironmental regions. The paper examines the continuity of hydropolitical relationships through a genealogical inquiry into the formulation and materialisation of Ghana's three dams: the Akosombo and Kpong dams built during the Cold War, backed by Western lenders and engineering companies; and the Bui dam commissioned in the 2010s, with support from China. Based on fieldwork in Ghana and China, as well as documentary evidence, the paper argues that the thinking, planning and building of dams interconnect the host regime and external techno-financial actors with their floating political-economic interests, but in a durable way. Sometimes, even if little concrete is actually poured, the symbolic power of dams endures, transforms, and at certain times and places expands, through events and discourses of national and international interest groups pursuing their own purposes, albeit with the replacement of influential individuals and powerful institutions, and regardless of the involvement of Western, Chinese and/or other actors. Ruptures exist but do not necessarily break the continuity of dam assemblages. The emergence of an opposition assemblage that battles against dams is a more recent complexity. [ABSTRACT FROM AUTHOR]

The distribution of sediment grain size can record past environmental conditions and human activity. In this study, radioisotope of 210Pb and 137Cs and a grain size of a 41 cm core in Hulun Lake were applied to reconstruct the high-resolution sedimentation history. The profiles of the grain size of the lake sediments show that silt (4–63 µm) was the largest contribution with an average content of 84.05%, and the second largest contribution was sand (>63 µm) with an average content of 15.68%. The median grain size and the mean grain size in the whole sediment core was 22.39 μm and 36.85 μm, respectively. Correlations of the sedimentological variables with instrumental measurements were also analyzed. The peak–trough value of the mean grain size of the sediments in Hulun Lake can reflect the magnitude of rainfall intensity and river discharge. The clay and silt contents at a depth of approximately 32–38 cm was different from other depths throughout the core, which showed continuous maxima with an average content of 0.35% and 94.08%. These changes in grain size correspond to the period of dam construction in 1963–1970. Therefore, the sediment grain size of Hulun Lake effectively recorded the dam-building activity. [ABSTRACT FROM AUTHOR]

• A field survey based on structure from motion (SfM) technique is presented. • Improper grade control may cause massive erosion in large-scale compound channels. • Floodplain stability is critical to grade control in large-scale compound channels. • Design suggestions are proposed for grade control in large-scale compound channels. Sediment flux in rivers has dropped globally in the past decades due to the increasing anthropogenic stressors, leading to significant riverbed degradation that may endanger the instream structures, collapse the banks and affect the riverine environment. To stabilise riverbeds, grade control structures (GCSs) have been widely applied in degrading channels. However, further understanding of the impacts of GCS on large-scale compound channels (with a main channel and floodplains) is needed. This paper reports a failure case of grade control in a large-scale compound channel (Shi-ting River, China), including a comparison of the bed profile measured using the structure from motion (SfM) technique before and after the flood season. The impacts of two improperly designed GCS on the bed morphology of the studied river reach are analysed and the reasons for failure of the present case are discussed based on numerical flow modelling. The results of numerical flow modelling and the measured bed profile indicate that the skewed mainstream flow direction in a curved main channel and the local scour downstream of a high drop GCS (3 ∼ 8 m) led to massive erosion on the floodplain near the GCS, significantly increasing the width and cross-sectional area of the main channel near the GCS. Consequently, the flow bypassed the GCS through the eroded area of the floodplain, leading to the dysfunction of the GCS. Due to the GCS dysfunction, a 5-year return period flood caused over 1.3 million m3 of erosion in the studied river reach (length ≈ 3.1 km), inducing severe bed degradation (up to 10 m) and reducing the width/depth ratio of the main channel upstream of the GCS. Through comparing the present study with the documented cases from literature, it is found that the bed degradation induced by GCS failure in compound channels develops much faster than those induced by sediment mining, weir or dam construction and reafforestation. Based on the analysed failure reasons, recommendations are provided for GCS design in large-scale compound channels. [ABSTRACT FROM AUTHOR]

The global diversity of freshwater fish has been greatly reduced as a result of human alteration. In the Yangtze River, China, the species composition has changed hugely owing to dam construction and overfishing. However, insufficient data have prevented the status of several fish species being evaluated, including that of largemouth bronze gudgeon (Coreius guichenoti), which is a commercially important endemic species.This study describes the effects of the Xiangjia Dam on populations of C. guichenoti. A multivariate autoregressive state‐space model was applied to catch per unit effort data derived from drifting gill nets deployed in the mid‐channel before (2005–2012) and after (2013–2018) the construction of the dam.The analysis indicated that the mean instantaneous population growth rate of the population was −0.252 over the entire period and that the growth rates of both total and local populations have declined. Before the impoundment, the probability of population extinction was close to 1, which was the result of overfishing. After impoundment, the probability of extinction became 1 at all sites, and the time until quasi‐extinction has decreased. Based on the Euler–Lotka equation, the reproductive parameter (á) has declined by more than 95%.The results show that the population of C. guichenoti in the upper Yangtze is almost certain to become extinct under the current conditions because of the Xiangjiaba Dam blocking migration routes. To protect this population, conservation measures, such as hatchery supplementation, the removal of small hydropower stations in the tributaries and the relocation of fish, are required. [ABSTRACT FROM AUTHOR]

Policies for promoting sustainable development of dam projects in the world have always been an argument due to the negative impacts on ecosystems. How to improve the efficiency of identifying the impacts and main indicators in the environmental impact assessment (EIA) process and post environmental impact assessment (PEIA) process is a common topic. Since the rapid dam construction in the past decades, most dam projects in China have turned to operation period. In order to identify the main impacts and provide scientific bases for the decision-making process, we optimized and applied the decision-support prototype (DSP) toolkit on the cascade dam projects on the Yangtze River. Through the optimization of the module and tools, the modified DSP was more applicable for China's dams. Though the modified DSP cannot replace large-scale assessments for dam projects, it would assist the EIA and PEIA process by identifying the most relevant environmental concerns and knowledge gaps at early stages of negotiation, so that more attention can be focused on subsequent studies and evaluative processes. On the other hand, some new limitations were found in our practice. In response to the limitations, we propose several suggestions: (1) SBQ: to introduce a factor to balance the proportion evaluation result of new developed dams and existing dams in the study; (2) SBQ: to consider more about interactions between cascade dam projects and their impacts on different spatial scales; (3) EEM, extend the parameters for generating EEM from dams in areas outside of the U.S. [ABSTRACT FROM AUTHOR]

Erosion and sediment delivery have been undergoing considerable variations in many catchments worldwide owing to climate change and human interference. Monitoring on-site erosion and sediment deposition is crucial for understanding the processes and mechanisms of changes in sediment yield from the catchments. The Ten Kongduis (kongdui is the transliteration of ephemeral creeks in Mongolian) are 10 tributaries of the upper Yellow River. Severe erosion in the upstream hills and gullies and huge aeolian sand input in the middle reaches had made the 10 tributaries one of the main sediment sources of the Yellow River, but the gauged sediment discharge of the tributaries has decreased obviously in recent years. In order to find out the mechanisms of changes in the sediment load of the tributaries, topographic surveys of four typical gullies in 3 of the 10 tributaries were made repeatedly in the field with the terrestrial laser scanning (TLS) technique. The results show that all the monitored gullies were silted with a mean net rate of 587–800 g/m2 from November 2014 to June 2015 and eroded by a mean net rate of 185–24,800 g/m2 from June to November 2015. The monitoring data suggest that the mechanism of interseasonal and interannual sediment storage and release existed in the processes of sediment delivery in the kongduis. The contrast of the low gauged sediment load of the kongduis in recent years against the high surveyed gully erosion indicates the reduction in their sediment delivery efficiency, which can be attributed to the diminution in hyperconcentrated flows caused mainly by the increase in vegetation coverage on slopes and partly by construction of sediment-trapping dams in gullies. [ABSTRACT FROM AUTHOR]

Fish passage facilities are an effective means for mitigating the effect of barriers (e.g., dams, weirs, and road crossings) on migrating fishes. Fishways in China were first recorded in 1958. The efficiency of fishways is one of the evaluation indicators of a river ecosystem's health. This paper summarises and analyses China's construction of fishways since 2000. Three typical cases (Changzhou water control project, Laolongkou water control project and Cao'e river gate project) are presented to illustrate the current situation of fishways in China. A discussion is also provided regarding ideological guidance, theoretical systems, technical means (monitoring), research content, legal systems and other aspects to elaborate the deficiencies and challenges of China's fishways. Thus, a number of prospects, such as proposing the design criterion of fish passages, performing basin ecological protection planning, and implementing adaptive management are urgent and necessary for further development of fishways in China. [ABSTRACT FROM AUTHOR]

This article investigates contestation over China-funded hydropower projects in Cambodia by examining the case of Chhay Areng. By analysing different social forces mobilising in pursuit of their own interests, particularly an anti-dam campaign group and the ruling party, this article emphasises the changing political dynamics that shaped both the strategies and outcomes of the contestation. Based on interviews with civil society representatives and a review of newspaper articles and published works, the article provides insights into the role of civil society and social media in the mobilisation and in shaping the outcome of this case. It also casts light on the nature of Chinese international development and the impact of the resultant contestation on China's influence and role as a regional and global power. [ABSTRACT FROM AUTHOR]

Dams are built on rivers for power generation, flood prevention and control, and water resources utilization. However, dams also reduce the connectivity of rivers, which hinders the exchange of material and organisms within rivers. The Yangtze River Basin and the Yellow River Basin are the two largest river basins in China. In this study, the connectivity of these two huge and highly impacted systems was investigated. The Dendritic Connectivity Index (DCI) was applied to evaluate the impact on river connectivity of dams with a reservoir capacity of larger than 0.1 km3. The results show that river connectivity decreased following an increase in dam construction. The connectivity of the Yangtze River Basin was close to 80 (0 is completely disconnected and 100 is connectivity under natural condition) in the 1980s, but declined significantly after the Gezhouba Dam was constructed on the mainstream of the Yangtze River. From 1980 to 2010, the connectivity of the Yellow River Basin was always lower than that of the Yangtze River Basin. The changes in the connectivity indices of potamodromous fish (DCIp) and diadromous fish (DCId) were determined for the period of 1980–2010. In the Yangtze River Basin, the DCIp decreased by 67.28% and the DCId decreased by 65.72%. In the Yellow River Basin, the DCIp decreased by 43.8% and the DCId decreased by 100%. In conclusion, the construction of dams, especially those on the main stream, has reduced the connectivity of the basin. The connectivity of the Yangtze River Basin and the Yellow River Basin has been severely affected. [ABSTRACT FROM AUTHOR]

Abstract: Characterizing the landscape changes and hydrologic alterations associated with dam construction is very important for watershed management. This paper presents a case study of the Lancang River in Yunnan Province following dam construction. The landscape patterns and dynamics indicate the fragmentation, shape, and diversity of the river in 1980, 1990, and 2000. The Range of Variability Approach (RVA) is used to evaluate the degree of hydrologic alteration (DHA) using 44 years (1957–2000) of hydrologic data. The results indicate that the midstream and downstream landscapes were affected by dam construction, becoming more complex and fragmented during the 1980–2000 period; the upstream area was not influenced by dam construction and the reservoir impoundment exhibited less change. The variability in maximum runoff occurrence in the post-dam period was less than that in the pre-dam period. The integrated DHAs of the Jiuzhou (upstream), Gajiu (midstream), and Yunjinghong (downstream) stations were relatively low, reaching 26.28%, 33.40%, and 37.14%, respectively. However, the alteration became obvious in the midstream area, and the situation worsened when the river was simultaneously influenced by dam construction and other human activities (downstream). The results of the regression analysis show strong relationships of landscape metric changes with DHA, and the forestland and water areas with DHA. The DHA increased along with the aggravation of landscape fragmentation, the complexity of the landscape shape, and the diversification of the landscape. [Copyright &y& Elsevier]