Reservoir Water Level Research Articles

Influences of Sediment Particles on Air Vessel Water Hammer Protection Effect in the Long-Distance Water Supply Systems

Abstract Long-distance water supply systems are important measures to improve the water resources distribution, and the water hammer protection devices such as air vessels are usually added in the project to ensure the safety and stable operation. However, the sediment particles are always ignored in the design. Hence, a numerical model and program were established for sediment laden water hammer based on the method of characteristics (MOC). Using the proposed model, the water hammer protection influences of sediment particles parameters are simulated for the same pipeline system of a water supply project. The result shows that the resistance loss of sediment-laden water in pipelines is larger than that of water, and the initial head of pump needed to be increased to ensure the water levels of downstream reservoirs are consistent. After power failure and pump stopping, the negative pressure wave of sediment-laden water is 2.97 m higher than that of water, and the theoretical minimum internal pressure along pipelines is 7.8 m lower. With the same air vessel protection, the lowest minimum internal pressure heads along pipelines decrease with the increase of quantities of sediment, while the results show no obvious influence by changes of median particle diameters. The lowest absolute pressure of pipeline could reach −0.69 m under the condition of 50 kg/m3 quantity of sediment and 0.05 mm median particle diameter. The relevant research results are of great significance sediment-laden water hammer numerical simulation and water hammer protection design.

Reactivation of an old landslide in north–central Iran following reservoir impoundment: Results from multisensor satellite time-series analysis

Water impoundment combined with more frequent precipitation extremes due to climate change increases landslide hazards on the slopes surrounding dam reservoirs. In situ monitoring systems in these potential landslide-prone areas are often unavailable, making landslide failures challenging to forecast. This paper describes a multisensor and multivariate remote sensing approach using data from Envisat, Sentinel-1, Landsat and PlanetScope satellites to reconstruct the spatiotemporal evolution of the mechanism and causes of the March 2019 landslide failure backside of the dam reservoir in Hoseynabad-e Kalpush village, north–central Iran. Statistical analysis and time series clustering are performed to derive the main landslide kinematic features from multitemporal interferometric synthetic aperture radar (MT-InSAR) analysis. We also exploit GIS and wavelet analysis to correlate potential external driving factors with landslide kinematics. Envisat and Sentinel-1 MT-InSAR analyses revealed that a previously stable old landslide was reactivated following reservoir impoundment in early 2013. As the reservoir water level rose during the following years up to 34 m in 2019, the landslide displacement rate gradually increased from 3.5 cm/yr to 8.4 cm/yr, and the destabilization gradually propagated upslope. At this stage, seasonal precipitation effects were detected only in the vertical component, indicating swelling and shrinkage movements of the shallower soil layer. The reactivated landslide accelerated and catastrophically failed following the exceptional precipitation in early 2019, producing a horizontal shift of >40 m, detected with optical image digital correlation. In the aftermath, the landslide continued to move with a decreasing trend until final stabilization in October 2021. Our study demonstrates how combined observations derived from multisensor satellite remote sensing data can be used to assess landslide precursors and kinematics, as well as the influence of climatic and anthropogenic factors on the instability of slopes surrounding water reservoirs. This is especially relevant in data-scarce areas.

Climate Change Impact On Upper Layang Reservoir Operation

The goal of reservoir operation policies is to get the most out of the water that can be stored and delivered as a water supply. Water shortages and floods may become more common in Malaysia because of climate change and global warming. The biggest impediment to developing reliable water storage and supplies in Sg Layang Reservoir, Johor, Malaysia, is a lack of water. Forecasting reservoir water levels is critical for storage management, particularly in water supply systems. As a result, the objective of this research is to create a reservoir simulation model using the Hydrologic Modeling System (HEC-HMS) to generate water levels to compare with observed water levels and to predict water levels using input variables such as future daily rainfall to examine the reservoir’s performance under changing conditions. Rainfall data from 2011 is utilized to calibrate the system, while data from 2012 to 2013 is used to validate it. The observed rainfall data was applied to the Sungai Layang watershed region. The correlation coefficient, R2, was employed to show the watershed’s best value. The calibration procedure has an R2 of 0.91, whereas the validation procedure has an R2 of 0.88. The accuracy of the model is satisfactory, as the R2 is near to 1.0, and calibration parameters can be employed in the following design processes, according to the analysis completed by HEC-HMS applications. The simulation was carried out using the same parameters in 2017, 2030, and 2050 with four distinct scenarios to evaluate water level behavior using future rainfall data. According to the simulation, most of the water level in the future will be below the crucial threshold of 23.5m. The findings reveal that climate change has an impact on reservoir functioning in terms of rainfall intensity.

Design for construction and assessment the accuracy of the automatic monitoring system for the horizontal displacement of the dam of Hoa Binh hydropower plant

The article presents solutions for designing, building and evaluating the accuracy of automatic monitoring system by robotic total station when continuously monitoring horizontal displacement of Hoa Binh Hydropower Plant . The system is designed and built put into operation and used for horizontal displacement monitoring results with high reliability and stability with accuracy of horizontal displacement less than 2.5 mm, for continuous and instantaneous data collection frequency, data can be extracted at any time according the erratic changes of weather, natural disasters or the change of reservoir water level and automatically send an alarm when the horizontal displacement value at the monitoring points reaches the alarm threshold. Continuous horizontal displacement monitoring is the basis to add settlement measurement cycle to check the settlement of the dam when there are abnormal signs of horizontal displacement.

Will extreme drought impact the reservoir water quality? A 30-year observational study

Climate change affects the security of the global water supply. However, only a few studies on the effects of drought on water quality in Asia have been published. In 2021, Taiwan faced its most severe water crisis in the past 56 years. The Te-Chi reservoir, situated at an elevation exceeding 1420 m, stands out as significantly affected by hydrologic variability. Overcoming geographical challenges, we captured an exceptional climatic period to sample and analyze water quality. Subsequently, we investigated multivariate long-term water quality data incorporating climate and hydrological information to evaluate the effect of climate change on the reservoir. The results showed the annual average temperature had risen by about 1.4 °C while total annual rainfall declined over the past 18 years. 30-year water quality data from 1993 to 2022 was analyzed to examined the long-term water quality change. There was an observed upward trend in the electrical conductivity of the reservoir water. The concentration of dissolved oxygen showed a decreasing trend, which may be attributed to the increase of temperature due to climate change. Besides, as the water level dropped during the drought, we found that the concentration of total phosphorus, total nitrogen and electrical conductivity in Te-Chi reservoir tended to increase, while the transparency of the water decreased. Consequently, we further explored the potential pollution sources during extreme drought by multivariate statistical methods, such as Pearson’s correlations, principal component analysis, and factor analysis. We found that four varimax rotated principal components collectively explain 82% of the variation in water quality data of the Te-Chi reservoir with the reservoir water level, signifying their representativeness in interpreting the monitoring data. We also assessed the contribution of each factor to specific water parameters, which can aid in better management of water resources during such challenging conditions. In conclusion, this study provides evidence and raises awareness on the effect of climate change by long-term water quality data with multiple parameters. The water quality components in the reservoir are affected by extreme weather, which is predicted to occur more frequently in the future and thus could affect energy scarcity, public health and food safety for sustainable reservoir operation. The study underscores adaptive management, mitigation strategies and the future research direction.

Correlation Analysis of Various Water Quality Parameters of the Tiru Reservoir, Maharashtra, India

The present study was conducted in the department of Aquatic Environment Management, College of Fishery Science, Udgir, District Latur, Maharashtra, India during August, 2017 to January, 2019 to investigate trophic status of the Tiru reservoir. Twenty (20) water quality parameters had been collected monthly from five sampling sites of Tiru reservoir, Udgir, Latur district, Maharashtra, India. Seasonal trends were analysed and discussed in this chapter. Pearson’s correlation coefficient (r) of eighteen physico-chemical parameters from five study locations were analyzed to know the pollution causing parameters. Water quality analysis showed that Total Phosphorus concentrations was highest in the summer, when reservoir water levels were lowest. Correlation between Total phosphorus and Chl-a was highest at 0.926. Eutrophication was mainly generated by phosphorus available in the water, which increases chlorophyll-a concentration (algal blooms). A positive correlation between temperature and DO might be possible because higher summertime water temperatures boost photosynthetic activity. SDD has shown a substantial negative connection with Chl-a throughout all seasons, since an increase in phytoplankton abundance yields a decrease in water transparency. The negative correlation between SDD and turbidity is primarily caused by the high levels of productivity in the summer, and high levels of suspended organic load due to surface runoff in the monsoon season. The majority of the time throughout the research period, Tiru reservoir was found in the eutrophic state, and in some cases even hyper-eutrophic.

Climate Change Scenarios Reduce Water Resources in the Schuylkill River Watershed during the Next Two Decades Based on Hydrologic Modeling in STELLA

The Schuylkill River Watershed in southeastern PA provides essential ecosystem services, including drinking water, power generation, recreation, transportation, irrigation, and habitats for aquatic life. The impact of changing climate and land use on these resources could negatively affect the ability of the watershed to continually provide these services. This study applies a hydrologic model to assess the impact of climate and land use change on water resources in the Schuylkill River Basin. A hydrologic model was created within the Structural Thinking Experiential Learning Laboratory with Animation (STELLA) modeling environment. Downscaled future climate change scenarios were generated using Localized Constructed Analogs (LOCA) from 2020 to 2040 for Representative Concentration Pathways (RCP) 4.5 and RCP 8.5 emission scenarios. Three regional land use change scenarios were developed based on historical land use and land cover change trends. The calibrated model was then run under projected climate and land use scenarios to simulate daily streamflow, reservoir water levels, and investigate the availability of water resources in the basin. Historically, the streamflow objective for the Schuylkill was met 89.8% of the time. However, the model forecasts that this will drop to 67.2–76.9% of the time, depending on the climate models used. Streamflow forecasts varied little with changes in land use. The two greenhouse gas emission scenarios considered (high and medium emissions) also produced similar predictions for the frequency with which the streamflow target is met. Barring substantial changes in global greenhouse gas emissions, the region should prepare for substantially greater frequency of low flow conditions in the Schuylkill River.

Using Remote Sensing to Study Impact El Niño Southern Oscillation on Reservoir Level at Murum and Bakun Dam Hydropower, Sarawak

In the years 2015 and 2016 has happened El Niño phenomenon was one of the three worst in history that has been happened since 1908. The El Niño phenomenon is usually related to the drought in Southeast Asia, Asia Pacific, and the Caribbean. This study analyses the impact of El Niño in the year 2015/2016 on rainfall at Bakun and Murum Hydropower using the technique of remote sensing. Global Precipitation Measurement (GPM) satellite was applied to understanding, the impact of 2015/2016 El Niño on rainfall at Bakun and Murum Hydropower. The results of this study show that drought conditions are widespread have reduced the total amount of rainfall and reservoir level and led to unusually low lake levels in Bakun and Murum reservoirs. Better understand the hydrological response and the complexity of different methods. The study found the rainfall decrease 20 until 30 % from normal during neutral and reduced 25 until 30 meters above sea level the reservoir water level at Murum and Bakun dam during the El Niño 2015/2016. The impact approach can support the design of more adaptive management strategies for specific areas.

Optimizing the Flood Limit Water Level of Reservoirs in Sediment-Laden Rivers under Changing Water and Sediment Conditions: A Case Study of the Xiaolangdi Reservoir

Optimizing the flood limit water level (FLWL) of reservoirs in sediment-laden rivers under changing water and sediment conditions is an important research topic that could improve comprehensive utilization benefits. Because reservoir operation has multiple objectives in sediment-laden rivers, this study established a water–sediment mathematical model, a comprehensive benefit evaluation model, and an evaluation index system. Taking the Xiaolangdi Reservoir of the Yellow River as an example, the operation mode of the FLWL under changing water and sediment conditions was studied. Under the scenarios of incoming sediment amounts of 300–800 million tons, when using the operation mode of gradually raising the FLWL, the sediment retention period was 4–13 years longer; the lower average annual siltation of the downstream channel and minimum bank-full discharge of the downstream channel after 50 years was larger by 150–260 m3/s than the operation mode of raising the FLWL at one time. However, with enhanced benefits of sediment blocking and siltation reduction, other benefits such as water resources supply, hydropower generation, and ecological improvement are reduced. The average annual number of days that do not meet the downstream water resources supply requirements, irrigation, and ecological improvement was increased by 0.64–2.16 days, and 91–197 million kW·h reduced average annual hydropower generation. The critical amount of incoming sediment was 350 million for conversion between the two FLWL operation modes, and it will increase to 450 million tons if the incoming runoff of the Yellow River increases by 20%. After constructing the Guxian Reservoir in the middle of the Yellow River, the critical amount of incoming sediment will increase to 600 million tons. This study is of great significance for improving the utilization efficiency of water resources and promoting the socio-economic development of river basins.

Numerical Simulation and Sensitivity Analysis of Sediment Issues in Pumped Storage Power Stations: Sediment Conveyance of Turbine and Sedimentation of Reservoirs

In this paper, a 1D process-based numerical model is established to study the sediment concentration via the turbine (TSC) and sedimentation of the lower reservoir and the upper reservoir of a certain pumped storage power station (PSPS), which is intended to be built on a sandy river. In addition, the sensitivity of TSC to some factors, such as suspended sediment gradation, the water level of the lower reservoir, and the coefficients of the sediment-carrying capacity formula, are analyzed in this paper. It is revealed that (1) the TSC will decrease by 30.8~34.5% when the incoming sediments of particle sizes less than 0.002 mm (which accounts for 3.95% of the totality) are replaced with incoming sediments of particle sizes between 0.002 mm and 0.004 mm. At the same time, the sedimentation thickness of the upper reservoir will decrease by 20.9%, and the siltation rate of the lower reservoir will increase by 2.4%. (2) The TSC will decrease by 12.6~13.1% as the water level of the lower reservoir rises by 17.55 m. This represents an increase of 8.4% in the average water depth and 26.4% in the storage capacity of the lower reservoir. At the same time, the sedimentation thickness of the upper reservoir will decrease by 32.2%, and the siltation rate of the lower reservoir will increase by 2.5%. (3) The TSC will decrease by 1.2~1.4% as the index of the sediment-carrying capacity formula m changes from 1.12 to 0.666, and the coefficient of the sediment-carrying capacity formula K changes from 0.2 to 0.6. At the same time, the sedimentation thickness of the upper reservoir will decrease by 7.2%, and the siltation rate of the lower reservoir will increase by 1.7%. Through the research on the sensitivity of the TSC, the direction and amplitude of the TSC changes with the boundary conditions are found, which provides a basis for the scheme comparison of specific projects and further supplements the prediction method system of the TSC. Meanwhile, the results remind researchers to pay more attention to the determination of boundary conditions and also provide the basis for the error analysis of the TSC. In summary, the results have certain guiding significance for the related research, and the sensitivity analysis results of the case could provide a reference for other specific projects.

Modelling reservoir sediment flushing through a bottom tunnel with an initially covered intake

Sediment flushing through a bottom tunnel is one of the most effective methods to alleviate reservoir sedimentation. However, the multi-physical hydro-sediment-morphological processes of reservoir sediment flushing through an initially covered bottom tunnel intake have remained poorly understood, and a physically enhanced and practically viable mathematical model is required. The present study uses an integrated model to resolve sediment flushing through an initially covered bottom tunnel intake. The proposed model couples a two-dimensional double layer-averaged model for the reservoir with a one-dimensional model for the bottom tunnel by means of numerical fluxes calculations at the inner boundary. The governing equations are solved synchronously using a well-balanced finite volume method. Several parameters related to boundary resistances and sediment exchange flux need to be determined for model closure. The model is tested against data from a series of physical experiments on reservoir sediment flushing, with sound agreement achieved between computed and measured scour hole geometries. Moreover, the present model successfully predicts the occurrence of tunnel blockage. The results prove that reservoir sediment flushing is best accomplished for high reservoir water level, small cover layer thickness, short tunnel length and steep tunnel slope. The present model facilitates reservoir design and operation to help preserve reservoir capacity.

Determination of Replacement Material Thickness in the Case of Expansive Soil in Dams

One simple solution to reduce the impact of damage caused by swelling on expansive soil is to replace it with soil that has better properties. Unlike replacing expansive soil material in the subgrade or foundation layer, replacing expansive material in a constructed dam requires special consideration, as fluctuating reservoir water levels and rainfall cycles affect the active zone of expansive soil, which will affect the stability of the dam. Therefore, this study was conducted to determine the thickness of the replacement layer, which is also the active zone of expansive soil in the dam, by modeling the stability of the dam against changes in reservoir water levels and rainfall cycles with parent analysis using finite element and limit equilibrium method programs. One example of dam damage caused by expansive soil was used as a case study. The study results show that changes in the wet-dry active zone can be used as a basis for determining the thickness of the replacement material in cases of expansive soil in dams.

Smart Home Remote Control System Prototype Using Internet of Things (IoT) Based ESP8266 Microcontroller

Technology is developing very rapidly in the current era, there will be several impacts that will result from the development of technology. Electronic equipment control can be done remotely in real time using the IoT system. The problem faced is the concern when leaving home. Because when leaving the house, homeowners sometimes often forget about electronic devices whether they are turned off or still on. IoT can be utilized at home as a smart home system by connecting an electronic device to an android application. This IoT-based smart home system uses an ESP8266 microcontroller which is used to connect between hardware and software that is controlled through the Blynk application. Blynk application is used as an interface that functions to provide input and produce output. This system consists of four sensors, namely the MQ2 sensor to detect gas leaks in the kitchen, the DHT11 sensor to determine the level of humidity and temperature in the bedroom, the PIR sensor to detect human movement at the front entrance, the ULTRASONIC sensor as a detector of the water level in the water reservoir and using three relays as a connector for lights and other electronic components. And using the Blynk application as a control system on the ESP8266 microcontroller.

Permeability Tests and Numerical Simulation of Argillaceous Dolomite in the Jurong Pumped-Storage Power Station, China

Due to its poor hydro-physical properties and other characteristics, argillaceous dolomite is susceptible to seepage failure under high water pressure, affecting the seepage stability of a rock mass. To ensure the safety of the project, when the argillaceous dolomite is present, it is necessary to study the conditions pertaining to its seepage failure. Taking the argillaceous dolomite of Jurong Pumped Storage Power Station as the research object, the spatial distribution, occurrence, scale, degree of weathering, and mechanical and hydrogeological characteristics of the argillaceous dolomite were studied. Through on-site water pressure tests and laboratory variable head tests, the permeability characteristics of argillaceous dolomite were analyzed, and the hydraulic conductivity of the argillaceous dolomite in the upper reservoir and underground powerhouse areas was quantified. The argillaceous dolomite specimens were collected, and seepage failure tests were conducted to determine the critical water pressure for its seepage failure. Based on the results of the laboratory tests, a numerical model of groundwater flow was established. By changing the water level of the upper reservoir and the measures of the anti-seepage and drainage, the seepage stability of the argillaceous dolomite was discussed. The actual water pressure of argillaceous dolomite in the underground powerhouse area was identified during the operation of the Jurong pumped-storage power station. The calculations show that when fully enclosed anti-seepage and drainage measures are taken for the underground powerhouse, the maximum head of water is 98 m, which is lower than the critical water pressure of seepage failure for the argillaceous dolomite. Therefore, no seepage failure will occur. The results provide a scientific basis for the anti-seepage and drainage design of the underground powerhouse area.

Deciphering the black box of deep learning for multi-purpose dam operation modeling via explainable scenarios

Operational rules of a multi-purpose dam are hidden due to missing of the records for decision-making processes. This study aims to assess the explainability of a deep learning model for the multi-purpose dam operation of Seomjin River, Juam, and Juam Control dams in the Seomjin River basin, South Korea. In this study, the Gated Recurrent Unit (GRU) algorithm is employed to predict the hourly water level of the dam reservoirs over 2002–2021. First, the GRU models are trained and validated using the local dam input (precipitation, inflow, and outflow) and output (water level) data to examine similarity/singularity in the operational patterns of these three dams. The hyper-parameters are optimized by the Bayesian algorithm. Secondly, the sensitivity test of the trained GRU model to altered input data (−40%, −20%, +20%, and +40%) is conducted to understand how the GRU models facilitate the input data to simulate the target output data (herein, hourly water level), which is known as explainability scenarios. Results show that the trained GRU models predict the hourly water level well across the three dams (above 0.9 of the Kling-Gupta Efficiency). Results from the explainability scenarios show a linear response to the altered inflow rates, but no response to altered precipitation. Furthermore, the GRU models show a site-specific response to altered outflow rates, depending on whether the observed outflow rate-water level relationship is linear or not. This study hints how to decipher the black box of deep learning in multi-purpose dam operation modeling via explainable scenarios.

Dam Surface Deformation Monitoring and Analysis Based on PS-InSAR Technology: A Case Study of Xiaolangdi Reservoir Dam in China

The Xiaolangdi Dam is a key project for the control and development of the Yellow River. It bears the functions of flood control, controlling water and sediment in the lower reaches, ice prevention, industrial and agricultural water supply, power generation, and so on. Its safety is related to people’s life and property safety and local economic and social development. It is of great significance to carry out comprehensive and regular deformation monitoring for dams since the deformation is an important evaluation index for dam safety. Interferometric Synthetic Aperture Radar (InSAR) technology has been a rapidly evolving technology in the field of space geodesy in recent years. It offers advantages such as high monitoring precision, extensive coverage, and high monitoring point density, making it a powerful tool for monitoring deformations in hydraulic engineering projects. Based on Sentinel-1 data covering the Xiaolangdi Dam from September 2020 to November 2022, the PS-InSAR technique was used to obtain the surface deformation of the Xiaolangdi Dam, and reservoir water level data on image acquisition dates were obtained for joint analysis. The results show that there is a large deformation in the center of the dam crest of the Xiaolangdi Dam, while both sides of the slope and downstream dam foot are relatively stable. The time series deformation of the dam body is closely related to the reservoir water level change. When the water level increases, the dam body tends to deform downstream; when the water level decreases, the dam body tends to deform upstream. The deformation and water level of the Xiaolangdi Dam exhibit a clear negative correlation. There is no significant cumulative deformation on the dam slopes or at the base of the dam. However, cumulative deformation occurs over time in the central area of the dam’s crest. The deformation process at the central area of the dam’s crest follows a continuous and non-disruptive pattern, which is consistent with the typical deformation behavior of the Xiaolangdi earth–rock dam structure. Therefore, it is judged that the current deformation of the Xiaolangdi Dam does not impact the safe operation of the dam. InSAR technology enables the rapid acquisition of high-precision, high-density deformation information on the surfaces of reservoir dams. With an increasing number of radar satellites in various frequency bands, such as Sentinel-1 and TerraSAR-X, there is now an ample supply of available data sources for InSAR applications. Consequently, InSAR technology can be extended to routine monitoring applications for reservoir dam deformations, especially for small and medium-sized reservoirs that may not be equipped with ground measurement tools like GNSS. This holds significant importance and potential for enhancing the safety monitoring of such reservoirs.

Inversion analysis of rock mass permeability coefficient of dam engineering based on particle swarm optimization and support vector machine: A case study

In order to efficiently and reasonably determine the permeability coefficient of engineering rock mass, the two key problems of complex seepage field simulation and objective function solution in permeability coefficient inversion are studied and improved. Firstly, a 3D refined seepage numerical model is established considering the main fault fracture zones and dam seepage control system. Secondly, combined with the support vector machine (SVM) algorithm, the complex mapping relationship between permeability coefficient of each rock layer and impervious structure and piezometer head is constructed. Finally, the particle swarm optimization (PSO) algorithm is introduced, and then the efficient optimization of permeability coefficient inversion of engineering rock mass and impervious structure is realized based on PSO-SVM. The case study of LJH arch dam shows that the inversion calculation framework based on PSO-SVM not only completes the rapid proxy calculation of the numerical model of complex seepage field, but also realizes the accurate optimization of the inversion objective function. The simulation results under the final inversion parameters reproduce the variation characteristics of the piezometric tube water level of each typical measuring point under the change of reservoir water level. In addition, with the correlation analysis between the permeability coefficient and the measured value of the corresponding piezometer, the parameter inversion method is endowed with new application value. This study is of great significance for clarifying the seepage characteristics of complex rock mass and improving the inversion efficiency of dam seepage monitoring data.

Deformation warning index for reinforced concrete dam based on structural health monitoring data and numerical simulation

The material mechanical parameters of the dam body and foundation will change when a dam is reinforced during the aging process. This causes significant changes in the structural state of the project and makes it difficult to ensure its structural safety. In this study, a new deformation warning index for reinforced concrete dams was developed according to the prototype monitoring data, statistical models, three-dimensional finite element model (FEM) numerical simulation, and the critical conditions of the dam structure. A statistical model was established to separate the water pressure component. Then, a three-dimensional FEM of the reinforced concrete dam was constructed to simulate the water pressure component. Furthermore, the deformation components that affected the mechanical parameters of the dam under the same amount of reservoir water level change were separated and quantified accurately. In addition, the method for inversion of comprehensive mechanical parameters after dam reinforcement was used. The influence mechanisms of the deformation behavior of concrete dams under the reservoir water level and temperature changes were investigated. A new deformation warning index was developed by combining the forward-simulated critical water pressure component and temperature component in the period of extreme temperature decrease with the aging component separated by the statistical model. The new deformation warning index considers the structural state of the dam before and after reinforcement and links the structural strength criterion and the deformation evolution mechanisms. It provides a theoretical foundation and decision support for long-term service and operation management of reinforced dams.

Exploring a Novel Reservoir Impoundment Operation Framework for Facilitating Hydropower Sustainability

Reservoir impoundment operation has far-reaching effects on the synergies of hydropower output, floodwater utilization, and carbon fluxes, but flood risk is significantly increasing, which is especially true when shifting to earlier impoundment timings and lifting reservoir water levels. This study proposed a novel reservoir impoundment operation framework driven by flood prevention, hydropower production, floodwater utilization, and carbon emission management. The Three Gorges Reservoir in the Yangtze River was selected as a case study. The results demonstrated that flood prevention safety could be guaranteed with the initial impoundment timings on and after the first of September. The best scheme of reservoir impoundment operation could efficiently boost synergistic benefits by enhancing 2.98 billion kW·h (8.8%) hydropower output and 6.4% water impoundment rate and decreasing greenhouse gas (GHG) fluxes and carbon budget by 28.15 GgCO2e/yr (4.6%) and 0.44 (23.1%), respectively, compared with the standard operation policy. This study can not only provide scientific and technical support for reservoir impoundment operations, benefiting water–carbon synergies, but can also suggest policymakers with various favorable advancing impoundment timing and lifting reservoir water level schemes to experience related risks and benefits in the interest of hydropower sustainability.

Creep behavior and permeability evolution of red sandstone in three Gorges Reservoir area subjected to cyclic seepage pressure

The creep behavior of the rock mass in an anchoring section affects the control effect of the stabilizing piles and the long-term stability of the landslide-stabilizing pile system. Additionally, periodic reservoir water level fluctuations cause cyclic water-seepage pressure changes in the rock mass of bank slopes, which may promote rock creep deformation, further compromising the stability of the slope and increasing the risk of landslides. In this experimental study, the creep properties and permeability of red sandstone from the bedrock of the Majiagou landslide in the Three Gorges Reservoir area were investigated under cyclic seepage pressure conditions. Four seepage pressures (0, 1, 2, and 1-2 MPa) were selected for comparison. The results demonstrated that creep strain curves, especially volumetric strain, exhibited fluctuations under cyclic seepage pressure conditions. The creep deformation of red sandstone was enhanced by cyclic seepage pressure. Creep strain increased with increasing deviatoric stress, except at 60 MPa deviatoric stress. Furthermore, the creep time to failure at 108 MPa deviatoric stress was inversely proportional to the seepage pressure. The steady-state creep rate exponentially increased with deviatoric stress, and the steady-state creep rate under cyclic seepage pressure was higher than that under constant seepage pressures of 1 and 2 MPa. Finally, the permeability of the red sandstone fluctuated in accordance with the fluctuating seepage pressure. The permeability evolution of the red sandstone samples under different deviatoric stresses was attributed to the competing processes of preexisting microcrack closure and the propagation of new microcracks. Accurate evaluation of the long-term performance of stabilizing piles and the stability of stabilized landslides necessitates consideration of the influence of cyclic seepage pressure on rock mass creep behavior.