Abstract:Through studying the mechanism and characteristics of water resources carrying capacity under urbanization, the leading factors of water resources carrying capacity under urbanization was analyzed. The evaluation index system and evaluation model of regional water resources carrying capacity based on the four dimensions of quantity-quality-space-stream were constructed. The proposed evaluation model was solved by chaotic particle swarm genetic algorithm (CPSGA). Taking Nanjing city of Jiangsu Province as the research object, the water resources carrying capacity of Nanjing from 2015 to 2018 was evaluated. The results show that the comprehensive evaluation model is more reasonable to be applied to the evaluation of regional water resources carrying capacity under urbanization, and the CPSGA algorithm can effectively optimize the weight of indexes, which reduces the subjectivity of the traditional evaluation method in index weighting, making the evaluation results more scientific and reasonable.

Abstract:Taking the acrossocheilus labiatus in the Sheyang River of Longyou County, Zhejiang Province as the representative fish, a habitat suitability model was established by using GAM and HSI models through the investigation of fish communities and possible habitat impact factors in the field from 2017 to 2020. The habitat suitability zoning and threshold range were analyzed. The results show that the arithmetic mean algorithm (AMM) for weighting GAM models has the best model fitness. Flow rate, chlorophyll a and water depth are the key explanatory variables of the habitat suitability index model, and their deviation contribution rates are 61.5%, 21.0% and 12.5%, respectively. The optimum flow rate is from 37 to 58 cm/ s, the optimum water depth is from 40 to 63 cm, and the optimum chlorophyll a is from 0. 10 to 0. 35 mg/ m3. The habitat zoning of the acrossocheilus labiatus has strong spatial-temporal differences. The optimum habitat is mainly distributed in the upper and middle reaches of the river while the habitat suitability significantly deteriorated in 2019 and 2020.

Abstract:The water quality data were collected at 11 typical sections in the middle and lower reaches of the Hanjiang River from 2013 to 2020. The single-factor index method, comprehensive pollution index method, and the water pollution index method were used to analyze the variation characteristics and causes of water quality indices at the 11 sections before and after water diversion. The results show that after water diversion, the monthly pollution indices of the 11 typical sections in the middle and lower reaches of the Hanjiang River increased in variant degrees, and the Luohanzha and Xingouzha sections were in the most severe water pollution. The frequency of water quality exceeding standards increased at all sections, with a deteriorated water pollution situation. TN was the dominant pollutant at each monitoring section in the middle and lower reaches of the Hanjiang River. Water pollution related to TP,CODMn and NH3 -N tended to deteriorate from the middle to the lower reaches. Water pollution at the Xinggouzha section was the most severe. In addition to the influence of water diversion, water quality variation was also affected by other factors such as the operation of water conservancy projects, point and non-point source pollution.

Abstract:Based on the theory of flow diversion ratio in bifurcated rivers, integrating the classical slice velocity analysis methods such as the inclined slice method and the influence of water resistance, a calculation method for the far-field surge propagation in a bifurcated river was proposed. Taking the Mogu toppling landslide of the Lianghekou hydropower station in the Yalong River as an example, considering the working condition of the Mogu toppling landslide to the bifurcated river in front of the dam of the Lianghekou hydropower station, the generation and propagation characteristics of the toppling landslide surge were analyzed by the proposed method. The initial surge height, dam front surge height and dam climbing height of two typical landslide sliding modes were obtained under the condition of the second phase storage water level of 2785 m. The results show that the surge height of landslide surge is 9. 32 m in front of the dam when the landslide slips along the fracture zone. When sliding along the strong and weak toppling interface, the surge height of the landslide surge is 14.73 m in front of the dam.

Abstract:In order to investigate the improvement effect of the arrangement parameters of oblique sillsat the bend flow in the spillway, indoor hydraulic model experiments were carried out. Improvement effect of water flow in the bend of each scheme were analyzed and compared. The results show that the arrangement of oblique sills can improve the bend flow condition, and improve the evenness of water surface meanwhile reduce the water surface difference in cross-sections. Furthermore, in the condition that the number of permeable oblique sills is higher withlarger sillheight and lower discharge, the water level at the convex bank is higher than that at the concave bank where maximum water surface difference appear. The regression analysis method was used to establish the prediction model of the improvement effect of the water surface in the bend considering the parameters of the permeable oblique sill, including the sill height, sill number and permeability rate, which can be used as a reference for engineering design.

Abstract:In order to analyze the inflow process of large reservoirs in the upper reaches of the Yellow River and the time history variation law of cascade power generation under the influence of climate change, the Longyangxia and Liujiaxia cascade reservoirs in the upper reaches of the Yellow River were taken as examples, and Mann-Kendall method was used to identify the abrupt change of the Tangnaihai and Xiaochuan hydrological series. On this basis, the HBV model considering the snow melting process was constructed, and the statistical downscaling method ( SDSM) was used to analyze the CanESM2 and GFDL _ ESM2G climate models. The rainfall and temperature data of three climate change scenarios (RCP2.6, RCP4. 5 and RCP8. 5) was downscaled in space and was used to drive hydrological model to predict future runoff. Finally, a cascade joint generation scheduling model in the upper Yellow River was constructed to reveal the impact of climate change on future generation scheduling process. The results show that the mutation years of runoff series in the upper Yellow River are concentrated in the 1980s, and the runoff decreases significantly after 2000. From 2021 to 2050, climate change will increase the runoff from June to September, and decrease the runoff in non-flood period. With the passage of time, the change law of cascade power generation of the Longyangxia and Liujiaxia Reservoirs is different. Under RCP8. 5, the uncertainty of climate model has the greatest impact on the difference.

Abstract:In order to comprehensively understand the current situation of global hydropower development, and to analyze the development potential of global hydropower and the international hydropower market,the current situation of global hydropower development in recent years was analyzed based on the hydropower annual reports released by the International Hydropower Association. It is found that the total installed capacity of global hydropower continues to increase, and affected by the continuous COVID-19 and the 2050 carbon neutrality target,the increaserate was still rebounded although it did not reach the estimated 2%. Combined with the development of global hydropower resources, the potential of global hydropower development was analyzed. The results show that Asia, South America, Africa, and North America have great development potential. China, Brazil, Russia, Canada, and the United States are among the best in overall hydropower potential. Bhutan, Iceland, Papua New Zealand Guinea, Guyana, and Gabon have relatively large hydropower potential per capita.

Abstract:To solve the problem of pipeline leakage location determination, the leak situation of a trans-oceanic pipeline was modeled by EPANET software, and the BP neural network model and K-CV improved SVR model were used to predict the leak location. Firstly, the number of hidden layers and learning function of BP neural network were optimized and selected, and K-CV method was used to search for the optimal combination of the penalty coefficient c and the kernel function parameter g of SVR. The EPANET software modeling data was used to form a training set, and the test set was randomly selected from original data for prediction. Meanwhile, the relative mean square error and correlation coefficient were used to evaluate the prediction results. The experimental results show that K-CV method can effectively improve the accuracy of SVR model. Compared with the traditional steady-state hydraulic equation, the neural network model has a wider range of applications and higher accuracy in the prediction of leak location of trans-oceanic pipelines.

Abstract:From the two aspects of river health and livability, 11 indicators were selected to construct the membership degree weighted evaluation model based on subjective and objective weighting method, and the coordinated development degree model was constructed. The above models were used to evaluate the construction status of Happy River in the main stream of the Feiyun River from 2016 to 2019. Improvement suggestions were proposed, including reducing human interference in river regulation, restoring ecological water demand, rational planning of water resources and deepening rive social service functions. The results show that the overall Happy Rive construction is inclined to the second level of happiness, and the coordinated development status is in the medium coordinated development stage, indicating the development tendency to well-coordinated development stage. Indexes such as water resources development and utilization efficiency, economic level of urban and rural residents, ecological water satisfaction degree, discharge process variation degree and river connectivity restrict the happiness level promotion for the Feiyun River.

Abstract:In order to effectively predict the continuous water level in a certain period in advance, a short-term water level prediction model based on sequence to sequence (Seq2Seq) was proposed. The model used a long short-term memory (LSTM)network to encoder the historical water level sequence into a context vector, and another LSTM network was used to decode the context vector to predict the target water level sequence. Taking the Liuxi River as the research object, the water level prediction model was established for different prediction lengths, and compared with LSTM model and artificial neural network (ANN) model. The results show that the highest Nash-Sutcliffe efficiency coefficient predicted by the Seq2Seq model for continuous 6 h, 12 h and 24 h is 0. 93, 0. 90 and 0. 85, respectively. When the prediction length is 6h, the performance of the LSTM and Seq2Seq model are similar, and the ANN model has lowest precision. When the prediction length is 12h and 24h, the Seq2Seq model has better performance and faster convergence speed compared with the LSTM model and ANN model.

Abstract:In order to study the mixing rule of pollutant at a flow confluence of open channel, a 90° open-channel confluence of equal width was chosen as the study area. A three-dimensional hydrodynamic-pollutant coupling transport mathematical model was established and validated. The simulation was performed for six cases of different flux ratios. The results indicate that, the distribution of pollutant at the flow confluence shows obvious three-dimensional characteristics, which is closely related to the secondary flow. The relation between the maximum width of the polluted zone and the flux ratio on the surface of water is different from that in the interior of water body. The maximum width of the polluted zone of the water surface is equal to the width of main channel under low flux ratio cases and does not change with the flux ratios. However,it presents a good linear function relation with the flux ratio under high flux ratio cases. The relation between the maximum width of the polluted zone and flux ratio is quadratic in the middle and bottom water. The mixing of pollutant is less uniform if the flux ratio is closer to 0. 5. The mixing rate of pollutant is faster if the flux ratio is higher.

Abstract:Taking the Zhaojiagou East Sluice-Pump Project proposed to be built in the Pudong New District of Shanghai in a typical plain river network area as the research object, a quasi-3D numerical simulation software, MIKE3 and a real 3D software, FLOW-3D, were used to simulate the flow patterns of the discharge flow. The rationality of the simulation results of the two models were analyzed and compared based on the existing results of the horizontal 2D model MIKE21 and physical model test. The results show that, the quasi-3D MIKE3 cannot meet the requirements of the refined simulation of the flow pattern of the sluice-pimp project, and its simulation results are different from those of the physical model test, but still similar to those of the horizontal 2D model MIKE21. The results of the FLOW-3D are close to the results of the physical model test, which are more refined and reasonable, and can be applied to the refined numerical simulation of flow patterns in the design and research of similar water conservancy projects.

Abstract:In order to improve the energy dissipation rate and increase the aeration, a new type of reverse arc-stepped spillway was proposed, in which the horizontal plane of the traditional right-angle step was changed into a reverse arc surface. The flow pattern, aeration location and energy dissipation rate of the reverse arc step were studied by physical model tests. The results show that in the range of test conditions, the flow patterns of the reverse arc step can be divided into four kinds, which are nappe flow, ejection flow, transition flow and skimming flow. When the length and height of a single step are the same, the aeration position of the reverse arc step is 0. 5 to 0. 8 times of that for a right-angle step, and the energy dissipation rate of reverse arc step is about 9% higher than that of a right-angle step.

Abstract:To reduce the data-hidden issue for multi-beam data of underwater scour region, a new model-dimension adjustment algorithm was introduced, in which the regional isolation and data chromatography threshold adjustment was combined, and the postprocessing method was also provided. Casestudy indicates that this new approach can improve the imaging performance for multi-beam bathymetry surveying data 3 to 5 times. Therefore, the hidden phenomenon of underwater scour datafor hydraulic structures is solved.

Abstract:Aiming at the problem that the vibration signal of pump unit is susceptible to random error and noise interference caused by various factors, which affects the evaluation result of the health status of pump unit, the filtering methods of vibration signal of pump unit were analyzed and studied. Taking the vibration signal at the pump coupling of a pumping station from the East Route of the South-to-North Water Transfer Project as an example, filtering methods based on Batworth, Hanning window, and harmonic wavelet were used to filter the vibration signal of the pump unit. The comparative analysis results show that there are time delay and line of axis trajectory in the FIR results of filtering methods based on Batworth and Hanning window, indicating incomplete filtering, while the harmonic wavelet filtering can almost completely filter out the interference. The advantages of harmonic wavelet filtering are more obvious when the frequency range is smaller for a certain frequency band.

Abstract:A check gate was taken as an example to study the dynamic characteristics of a large width-height ratio steel radial gate under the action of water pulsation, by means of establishing the finite element model to analyze the effects of fluid-solid coupling and arm thickness on the gate vibration characteristics. Based on the random vibration method, the fluid-induced vibration displacement and stress response of the gate under the action of pulsating flow were obtained. The dynamic response of the gate was evaluated by the dynamic coefficient method. The results show that the basic order vibration of the gate is less affected by water, and the lower order vibration is more affected by the arm. The maximum displacement response of the flow-induced vibration under typical working conditions of the gate is 4. 029 mm, and the maximum dynamic stress is 61. 247 MPa. The dynamic coefficients are all lower than 1. 20. The overall dynamic stress level is low, and the gate can operate safely under the action of dynamic water.

Abstract:In order to meet the requirements of complex index system and multiple evaluation subjects for reservoir safety evaluation, and to reduce the influence of the subjectivity and blindness of traditional variable weight AHP equilibrium coefficient on the objectivity and authenticity of the evaluation results, a variable weight AHP with improved equilibrium coefficient was proposed. Through the application to the Mamiao Reservoir project, the variable weight of secondary indicators and the fuzzy comprehensive score of primary indicators and overall objectives calculated by traditional variable weight AHP and improved variable weight AHP were compared and analyzed. The results show that the improved variable weight AHP can avoid the problem of state imbalance caused by the independent assignment of the equilibrium coefficient of each secondary index by the traditional variable weight AHP, and the blindness caused by giving the same equilibrium coefficient to each secondary index is appropriately weakened. The fit between the evaluation result and the current situation of reservoir safety is improved. The evaluation results are consistent with the conclusions of the expert group, which shows the reliability of the method in this paper.

Abstract:Based on the research status, the dynamic processes of drift wood recruitment, transport-accumulation, accumulation-blockage and breakage were reviewed in detail, and the disaster effects of drift wood in flash flood and debris flow were summarized from four aspects of direct impact damage, clogging-submergence, clogging-scouring, and breakage-scouring. In order to deal with the disaster effect of drift wood, the disaster prevention and mitigation measures combined with engineering measures and management measures were put forward. On this basis, it is pointed out that the future research topics on drift wood disaster include quantitative evaluation of drift wood recruitment, dynamic process of drift wood transport-accumulation-clogging-breakage, disaster-causing effect and risk assessment of drift wood, disaster control and mitigation measures of drift wood.

Abstract:Based on systematic literature reviewing,the formation mechanism of bifurcating channels was introduced, such as central bar deposition, transverse bar conversion, chute cutoff, dissection of multiple bars and avulsion. Factors influencing water and sediment distribution include geometrical form, riverbed topography and hydraulic characteristics of bifurcating channels. The research progress of water and sediment distribution calculation method was also introduced. Taking the middle and lower Yangtze River as an example, the hydraulic characteristics and evolution characteristics of bifurcating channels were summarized. Finally, the problems that still need to be solved in the study of bifurcating channels were discussed, especially the application status and prospect of numerical simulation in the study of bifurcations formation and evolution.