Abstract:The existing flood regulation calculation methods for pumped storage power stations mostly neglect the hydraulic linkage between upper and lower reservoirs and tend to oversimplify scenarios involving the superposition of full-generation flow and natural floods. To address these issues, a flood regulation calculation method for the joint operation of upper and lower reservoirs in pumped storage power stations based on a segmented iterative method was proposed. This model established a mathematical framework that captured the complete water exchange and hydraulic coupling relationship between the upper and lower reservoirs and applied a segmented iterative algorithm to finely resolve the dynamic variations in water level and flow of the upper and lower reservoirs. On this basis, the model integrated a sliding combination approach to construct a flood encounter scenario matrix, simulating the impacts of various operating conditions and flood encounter scenarios on reservoir operations. A dynamic reserved reservoir capacity control strategy was proposed to ensure the safe operation of the power station and meet subsequent power generation needs. Case study results indicate that the proposed model can accurately and reliably simulate the dynamic response of upper and lower reservoirs under complex flood scenarios and effectively reveal the critical influences of flood encounter timing, operational status of the power station, and reserved reservoir capacity control strategies on hydrological conditions of the reservoirs. The most unfavorable flood encounter scenario identified by the model aligns with the operational characteristics of pumped storage power stations, offering a scientific reference for their engineering design and safe operation.

Abstract:In order to scientifically identify and evaluate the impact of the Western Route of the South-to-North Water Diversion Project (Phase Ⅰ) on the hydrology and water resources, ecological environment, and social economy of water source areas, the comprehensive situation of the project-affected water source areas was considered. In addition, based on literature and normative standards, a comprehensive impact assessment system for the Western Route of the South-to-North Water Diversion Project (Phase Ⅰ) was established, covering multiple criterion levels including hydrology and water resources, ecological environment, water energy utilization, and social economy. Moreover, the weights of the evaluation indicators were determined by the subjective and objective comprehensive weight method based on the fuzzy analytic hierarchy process and the improved entropy weight method. Combined with the TOPSIS method, the comprehensive situation of the water source areas along the Western Route of the South-to-North Water Diversion Project (Phase Ⅰ) from 2012 to 2021 was objectively evaluated. The results indicate that the comprehensive situation of the water source areas along the Western Route of the South-to-North Water Diversion Project (Phase Ⅰ) has improved, transitioning from a poor state prior to 2017 to a healthier one by 2021.

Abstract:Based on the multi-regional input and output table, the water, energy, and food (WEF) resource flow between Guangdong Province and other provinces/autonomous regions/cities in China was calculated, and the amount of risk transferred through WEF resource flow between these provinces/autonomous regions/cities was innovatively quantified. Moreover, the value of risk transfer was explored.The results show that:in the inter-provincial WEF resource trade, the net inflow of embodied water to Guangdong Province is 11.706 billion cubic meters; the net inflow of embodied energy is 2.80×109GJ, and the net inflow of embodied food is 16.229 3 million tons. Most regions have a net inflow of WEF resources to Guangdong Province, with Guangxi Zhuang Autonomous Region, Henan, Anhui, and Hunan provinces exhibiting the highest inflow values.The influence coefficient and induction coefficient of WEF resources in Guangdong Province are low, and the driving and influence effect on other provinces/autonomous regions/cities in the national WEF resource trade is not strong. In addition, the induction ability of resource consumption changes in other provinces/autonomous regions/cities is weak. The risk transfer value of WEF resource flows exhibits an asymmetrical pattern between input and output regions. For most regions,the risk transfer value of WEF resource flow into Guangdong Province is high. On the basis of alleviating the risk of WEF resources in Guangdong Province, the risk in these regions has not significantly improved, especially in Hainan Province, Tianjin City, Shanghai City, Henan Province, and Gansu Province.The risk transfer value of Yunnan Province, Beijing City, Shanxi Province, and Zhejiang Province is relatively low,and the WEF resource risk caused by the resource input of Guangdong Province is relatively large.

Abstract:Based on the water cycle model of distributed architecture, the Chuhe River Basin was divided into hydrological characteristic units such as the slope of the hilly area, the slope of the plain area, the river channel of the hilly area, the river channel of the plain area, the polder area, and the sluice dam project. The Xin’anjiang hydrological model was constructed in the hilly area; the hydrological model and the one-dimensional hydrodynamic model were constructed in the plain area; the flood drainage model was built in the polder area, and the project dispatching model was constructed for the sluice dam project. All models were coupled into an integrated flood control and drainage model that could fully generalize each natural entity element in the Chuhe River Basin. The accuracy and reliability of the model were verified through the flood processes of typical stations in the hilly and plain areas during the flood years (2016 and 2020). The results show that the integrated model can reproduce the flood processes in the basin in 2016 and 2020 quite well, and both the calibration and verification results reach Grade A accuracy.

Abstract:The super-efficiency slack-based measure (SBM) model considering unexpected output was used to measure the water resources utilization efficiency of 20 counties and districts in the water receiving area of the Bailong River Diversion Project in Gansu Province from 2011 to 2020. The Tobit model was used to analyze the main influencing factors of water resources utilization efficiency. The results show that the economic efficiency of water resources in the receiving area shows a downward trend, while the utilization environment and green efficiency of water resources exhibit a steady upward trend. Water use factors, economic level, industrial structure, and water resources endowment promote the economic efficiency of water resources utilization, while urbanization level inhibits the economic efficiency of water resources utilization. Urbanization level has a positive effect on the environmental efficiency of water resources utilization, while industrial structure and water resources endowment have negative effects on the environmental efficiency of water resources utilization. Industrial structure and water resources endowment inhibit the green efficiency of water resources utilization. On the whole, the green efficiency of water resources utilization is greater than the environmental efficiency, and the economic efficiency ranks last; the level of water resources utilization efficiency in the water receiving area is not high from 2011 to 2020. Therefore, the water receiving area needs to optimize the industrial structure, and neighboring counties and districts can strengthen regional cooperation to narrow the differences.

Abstract:To identify the sources of nitrate in irrigation canal water bodies of the Ganfu Plain, pH, electrical conductivity, concentrations of dissolved oxygen and NO-3, and nitrate isotope compositions ( δ 15N-NO^-3 and δ 18O-NO^-3) in the West Main Canal of the Ganfu Plain during spring and autumn were analyzed. The contributions of the main pollution sources were quantitatively analyzed using the stable isotope analysis in R model based on Bayesian mixing (MixSIAR model). The results show that the nitrification in water bodies of the West Main Canal is slightly stronger in autumn than in spring but is overall weak in the two seasons, and denitrification is almost not observed. The sources of NO^-3 in water bodies of the West Main Canal mainly include the upstream water, ammonium-nitrogen fertilizer, soil nitrogen, domestic sewage and manure, as well as precipitation. The upstream water (with a contribution rate of greater than 50%) and human activities (including the ammonium-nitrogen fertilizer, domestic sewage, and manure, with a contribution rate of greater than 37%) play a dominant role in the NO^-3 concentration in the entire irrigation canal water body. The contribution rates of pollution sources to NO-3 in the irrigation canal water body in descending order are as follows: upstream water, ammonium-nitrogen fertilizer, domestic sewage and manure, soil nitrogen, precipitation in autumn, and ammonium-nitrogen fertilizer, upstream water, domestic sewage and manure, soil nitrogen, precipitation in spring. In addition, the contribution of NO^-3 sources is associated with land use patterns. The contribution rates of upstream water and domestic sewage and manure show upward trends from rural to urban areas, while the contribution rate of ammonium-nitrogen fertilizer shows an opposite change.

Abstract:In view of the limited comparative research of pyrite-based iron autotrophic denitrification and sulfur autotrophic denitrification and low efficiency in nitrogen removal, pyrite was utilized as an electron donor for both sulfur autotrophic denitrification and iron autotrophic denitrification. Moreover, their performance in removing nitrogen from wastewater with a low carbon/nitrogen ratio (C/N) and the enhancement mechanisms involving heterotrophic bacteria were compared and investigated. The results show that the pyrite-based iron autotrophic denitrification system achieves higher nitrogen removal efficiency than the sulfur autotrophic denitrification system, and adding an appropriate amount of heterotrophic bacteria can enhance the nitrogen removal effect. At a heterotrophic-to-autotrophic sludge volume ratio of 1∶1, the pyrite-based iron autotrophic denitrification system yields effluent TN and NO^-3-N concentrations of 0.26 and 0 mg/L after 48 h, which were significantly lower than those of the sulfur autotrophic denitrification system (3.94 and 2.61 mg/L) under identical influent conditions. Thermomonas, Geothrix, Ferritrophicum, Acidovorax, Pseudomonas, Brachymonas, and other denitrifying bacteria can use reduced iron as an electron donor to participate in denitrification, and their relative abundance in the pyrite-based iron autotrophic denitrification system is all higher than that in the sulfur autotrophic denitrification system. Furthermore, the addition of heterotrophic sludge into the system can introduce Thauera . Compared with sulfur autotrophic bacteria, iron autotrophic bacteria and heterotrophic bacteria can exert a better synergistic denitrification and nitrogen removal effect.

Abstract:In order to improve the accuracy of weights in the evaluation index system for the ecological revetment’s impact on river ecosystems, a combinatorial weighting method based on game theory was proposed. This method optimally combined the weights calculated by the analytic hierarchy process (AHP) and entropy weight method to obtain comprehensive weights, taking into account both the subjective judgments of experts and the objectivity of data. The case study of the Jiepai Water Conservancy Project of Xinmeng River in Jiangsu Province shows that the combinatorial weighting method based on game theory can reflect the characteristics of different weighting methods and obtain more reasonable evaluation results.

Abstract:In order to study the evolution law of the safety factor of gravity dams on soft rock foundations, a shear strength parameter inversion method of structural plane based on monitoring data was proposed. By establishing a time-varying model of shear strength parameters and applying a partitioned finite element-interface element hybrid algorithm, the dynamic evaluation of the long-term anti-slidingstability of gravity dams was achieved. The verification results of engineering examples show that the proposed method effectively reflects the true variation of engineering parameters, significantly improves the accuracy of analysis results, and ensures dynamic evaluation of the engineering safety factor.

Abstract:To more accurately simulate the inundation process of inundation areas downstream of small-sized reservoirs after dam breaches and reveal the coupling mechanisms of dam breaches and levee overtopping, the DaYJ Reservoir in Guizhou Province was studied. Digital elevation measurements and orthophoto imaging were conducted in the reservoir area and downstream flood-prone areas. A coupled model of dam breaches and levee overtopping was developed based on a high-precision DEM, and sensitivity analyses were performed within the study area regarding flood depth, flow velocity, and flood severity relative to levee height. The results indicate that compared with the single dam breach model, the coupled model of dam breach and levee overtopping can more realistically simulate the changes in the inundation range downstream over time. When the levee height is no more than 1 m, overtopping is highly probable. A transitional state between levee overtopping and non-overtopping occurs at a levee height of approximately 1.5 m. When the levee height exceeds 1.7 m, overtopping is entirely prevented, and the flood primarily bypasses the levee from its end, inundating residential areas. As levee height increases, the arrival time of the flood, the emergence time of a 0.3 m water depth, and the occurrence time of the peak flow velocity are all delayed. Furthermore, both the maximum flow velocity and the peak flood severity within the study area of levee overtopping generally decrease and become more uniformly distributed.

Abstract:To alleviate sediment deposition in urban drainage pipelines, a hydraulic self-cleaning structure for pipelines was designed, incorporating a gate and flume.Numerical simulation methods were conducted to analyze the hydraulic characteristics of the dredging process under different slopes and initial inflow levels. The results show that at the initial stage of dredging, the flume shear stress and vertical mean velocity at the inlet of the pipeline can reach 16 and 1.55 times those at the end of the process, respectively. As the flushing wave moves to the end of the pipeline, the maximum flume shear stress and the maximum vertical mean velocity at the inlet of the pipeline can reach 5 and 2 times those at the end of the pipeline, indicating a stronger dredging effect in the upstream section. During dredging, the maximum shear stress of the flow in the flume and the maximum vertical mean velocity can reach 104 and 1.45 times those on the platform, respectively, indicating that the dredging efficiency in the flume is significantly superior to that on the platform.Specifically, the increased slope of the pipeline and higher initial inflow levels result in greater flushing wave shear stress and vertical mean velocity, with maximum recorded values of 156 Pa and 3.6 m/s, respectively, reflecting a better pipeline cleaning effect. During dredging, the flushing wave velocity and shear stress generated are significantly higher than the theoretical uplift flow velocity and critical shear stress of the sediment, which proves that the dredging effect of the hydraulic self-cleaning structure is good.

Abstract:To accurately assess the sensitivity of the parallelcomplex disaster in the Guangdong-Hong Kong-Macao Greater Bay Area, a sensitivity assessment index system for the parallel complex disaster of landslide and avalanche was constructed. Additionally, a sensitivity assessment model considering the spatial dimension superposition effect of the parallelcomplex disaster was established and derived. The results show that the parallel complex disaster of landslide and avalanche in the Guangdong-Hong Kong-Macao Greater Bay Area has high sensitivity areas concentrated in the northwestern part of the Bay Area such as Huaiji County and Fengkai County and the northeastern part of the Bay Area such as Longgang District and Huicheng District; low sensitivity areas are concentrated in the central part of the Bay Area such as Sanshui District and Nanhai District and the southwestern part of the Bay Area such as Taishan City and Enping City. Moreover, the higher sensitivity, middle sensitivity, and lower sensitivity areas are scattered sporadically between high and low sensitivity areas as transition areas.

Abstract:To better evaluate the internal friction angle of shallow cushion layers in pile-soil composite subgrades, the relationship between the internal friction angle of sand cushion layers and the specific penetration resistance was analyzed based on cavity expansion theory and static cone penetration tests. Laboratory calibration tests were conducted using a probe with an optimized diameter, incorporating Bolton’s stress-dilatancy theory, so as to establish a calibration relationship between the internal friction angle and relative deformation in gravel cushion layers. Field tests were carried out to determine the variation ranges of internal friction angles of shallow cushion layers in different types of composite subgrades. The results show that the specific penetration resistance increases with the increase in the internal friction angle of the sand cushion layer. In the laboratory calibration test, the internal friction angle ranges from 28.3° to 35.1° for sand cushion layers and from 33.1° to 42.6° for gravel cushion layers. Moreover, the average value of the internal friction angle of sand cushion layers in flexible pile composite subgrades generally ranges from 33.5° to 36.0°, while for gravel cushion layers in semi-rigid and rigid pile composite subgrades, the internal friction angle is between 37.0°-39.0° and 38.5°-40.5°, respectively.

Abstract:Based on physical model tests of the flume, the local scour characteristics of the tripod pile foundation for a tidal current energy turbine were investigated, and the effects of the installation angle of the foundation and flow intensity on the evolution of local scour depth of the tripod pile foundation under full machine operating conditions were explored. The experimental results indicate that as the flow intensity increases, both the scour rate around three piles of the tripod pile foundation and the maximum scour depth increase, with the maximum scour depth occurring at the upstream face of the piles. The scour development around the tripod pile foundation varies with changes in the installation angle, showing the most severe scour when the installation angle is 30°. At a 0° installation angle, the upstream piles experience relatively weak scour. When the installation angle reaches 30°, the pile located alone on one side exhibits the fastest scour rate. At a 60° installation angle, the upstream piles demonstrate greater scour depth.

Abstract:Based on the flow, sand, and topographic data during the flood seasons of 2005 and 2014, the three-dimensional (3D) numerical model of flow and sediment and the mechanism decomposition of suspended sediment flux were utilized to analyze the changing rules of the hydrodynamics and sediment dynamics in the Jiaojiang River Estuary under the influence of human activities. In addition, the process of sediment transport in the estuary was discussed, as well as the change in the mechanism and its influencing factors. The results show that dominated by the overall topographic change of the river, the tidal dynamics and sediment dynamics in the estuary change significantly; by taking Shixianfu as the demarcation, the upstream flood tide advantage is enhanced, and the downstream flood tide advantage is weakened, but the current velocity of the flood tide and the ebb tide along the river is increased. The distribution of the estuarine turbidity maximum moves upstream for more than 36 km, and the average sediment concentration in the section between Miaolonggang and Shixianfu increases by about 5 kg/m³, while that in the section between Shixianfu and Haimen increases by about 3 kg/m³. The increase in the sediment concentration and tidal asymmetry in the upper reaches of the river leads to a stronger tidal pumping effect on sediment transport in the estuary and varying total amounts and directions of sediment transport during the spring and neap tides. This in turn causes a mechanism shift from the “estuarine sediment transport to the sea at the upstream and to the land at the downstream” in terms of spatial characteristic difference to the “sediment transport to the land during spring tide and to the sea during neap tide” in terms of the tidal type distribution difference, which thus affects the characteristics of riverbed erosion and deposition.

Abstract:To analyze the nearshore motion characteristics of weakly inertial plastic particles, physical wave flume experiments were conducted to observe and compare the motion characteristics of medium-sized spherical plastic particles in a floating state and bottom-lying state under the action of regular waves with limited water depth. In addition, the dynamic responses of these plastic particles under different wave conditions and boundary conditions were investigated. Based on the motion quantity spectrum, the maximum possible horizontal displacement of the plastic particles in the bottom-lying state during random motion was estimated. The experimental results show that the motion law of plastic particles in the floating state basically conforms to the second-order Lagrangian drift theory; the motion trajectories of plastic particles in the bottom-lying state are mostly irregular, and random high-frequency disturbances account for 20% of their motion amplitudes; the maximum possible horizontal displacement increases first and then converges with the increase in the incident wave period.