Journal of Hydroelectric Engineering

水力发电学报

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2023 Vol. 42, No. 6 Published: 2023-06-25

	1	Reservoir impounding strategies of cascade reservoirs under extreme low-flow conditions. Case study of lower Jinsha River and Three Gorges cascade reservoirs ^Hot!
		CAO Rui, LI Shuai, XING Long, ZHU Wenli, GONG Wenting, SHEN Zhaoyong
		DOI: 10.11660/slfdxb.20230601
		To maximize power generation benefit, this study explores reservoir impounding strategies adapted to extreme low-flow conditions in the case of the lower Jinsha River and the Three Gorges cascade reservoirs, and presents a new reservoir impounding scheme by combining the impounding rule of benefit maximization and the water supply requirement of the Three Gorges Reservoir. We also examine alternative reservoir impounding schemes aimed at different water allocation principles that meet the targets of reservoir stages or the control boundaries. Typical extreme low-flow scenarios are simulated numerically for operation and benefit analysis. From the results, we demonstrate a critical condition of natural inflow for full filling of the cascade reservoirs－the natural inflow is above the level at the frequency of 97% from August through early September, and above the level at the frequency of 90% from mid-September through November. Under extreme low-flow conditions, the cascade reservoirs will be able to perfectly fulfill the water supply requirement of the Three Gorges Reservoir if they adopt a certain joint water supply dispatching. In the case of a full filling impossible, their power generation benefit can be maximized by impounding preferentially those in the lower Jinsha River, such as the Baihetan Reservoir first and then the Xiluodu Reservoir as recommended by this study.
		2023 Vol. 42 (6): 1-12 [Abstract] ( 105 ) PDF (1961 KB) ( 521 )

	13	Urban flood risk assessment for Shenzhen River basin
		TANG Qingzhu, XU Zongxue, WANG Jingjing, CHEN Hao, YANG Fang
		DOI: 10.11660/slfdxb.20230602
		The increasing urban flooding threatens urban safety and sustainable development, and further improvement in the accuracy of urban flood risk simulation and assessment are essential to protect people's lives and properties. In this study, a flood simulation model is developed for the Shenzhen River basin based on a Cellular Automata flood simulation model, and inundation depths are simulated for the design rainfall conditions of this basin. Using the Hazard-Vulnerability risk assessment framework, we consider its different rainfall scenarios and assign weights to its different urban flood risks, through a game theory-based combination of weights determined by the analytic hierarchy process and the Criteria Importance Though Intercrieria Correlation methods. Then, its urban flood risks are evaluated and predicted. The results show typical temporal and spatial differences occur over the high-risk areas of urban flooding in the basin. With an increasing rainfall recurrence period, the ratio of the risky area increases, such as from 0.20% of a 2-year rainfall event to 0.82% of a 100-year event; the ratio of the medium-low risk area decreases, such as from 67.4% to 64.7% in terms of the two events. The results of this study can be visualized to show the distribution of flood risks over the basin, helping improve its flood control system and enhance the urban flood prevention capability and resilience of the city.
		2023 Vol. 42 (6): 13-22 [Abstract] ( 195 ) PDF (3739 KB) ( 578 )

	23	Impacts of extreme weather on Sichuan power in summer of 2022 and its enlightenment
		ZHOU Yerong, MAO Yuxin, HU Yang, TIAN Rui, HUANG Weibin, MA Guangwen
		DOI: 10.11660/slfdxb.20230603
		Climate change is closely related to energy-power supply and demand. In the summer of 2022, the upper reaches of the Yangtze River experienced three worst cases: the highest temperature, longest continuous hot days, and lowest rainfall in the same period in history. This resulted in a daily power shortage of 17 million kW and 370 million kW?h in Sichuan, a major hydropower province, and imposed a significant impact on its social and economic development and people’s livelihood. To guarantee energy and power safety, it is of great significance to establish power planning mechanism and some countermeasures for power supply guarantee in extreme weather. This paper presents an analysis on the impacts of extreme weather in the 2022 summer on the power supply guarantee in Sichuan, and examines the shortcomings of previous electric power development. We suggest certain countermeasures for the period of power transformation－such as water-wind-solar-thermal energy complementarity, and a coordinated development of power supply and power grid.
		2023 Vol. 42 (6): 23-29 [Abstract] ( 302 ) PDF (422 KB) ( 681 )

	30	Coupled uncertainty of flash flood forecasting method and its application
		WANG Zhengrong, HAN Juntai, YANG Yuting
		DOI: 10.11660/slfdxb.20230604
		Uncertainty in each forecasting component, such as driving data, hydrological simulation, and early warning method, imposes an impact on the uncertainty of flash flood risk early warning, but its mechanism is not well understood yet and the theory and method for a quantitative combination analysis are lacking. This study develops a coupled uncertainty analysis method for flash flood early warning based on hydrological model simulations, formulates a dynamic critical rainfall index, and applies both to an analysis of the lower reaches of the Min River in Fujian Province. The results show the uncertainties caused by precipitation input, runoff simulation, and critical rainfall quantification account for 36%, 24% and 40% of the total uncertainty, respectively. Under a coupled uncertainty analysis, the average probabilities of flash flood disasters at risk levels IV, III, II and I are 58%, 65%, 79% and 81%, respectively. This new analysis method is of great significance in practical flash flood warming and disaster prevention.
		2023 Vol. 42 (6): 30-39 [Abstract] ( 121 ) PDF (2488 KB) ( 452 )

	40	Effect of local pipeline reconstruction on waterlogging risk. A case study in Jincun, Jincheng City
		HUANG Yixuan, XU Zongxue, YE Chenlei, LIAO Ruting, SHU Xinyi, JIA Shuhui
		DOI: 10.11660/slfdxb.20230605
		Urban flood disasters are a significant restraint on the sustainable development of society and economy; and many built-up areas have an urgent demand for upgrading the rainwater pipeline network in a limited space. This paper demonstrates local pipeline reconstruction, which improves the drainage capability of the whole area. A coupled hydrological and hydrodynamic model is developed, and pipeline reconstruction schemes are designed through identification of the waterlogging areas. Based on the return period of local flood control and drainage design, key factors of flood-waterlogging are examined, and flood risks are assessed using multi-source data before and after pipeline reconstruction. The results show that for the rainstorms with return periods of 3a and 30a, the reconstruction reduces the length of severely ill pipelines by 1990 m and 921.6 m and the node overflows by 73.61% and 55.13%, respectively. It lowers the rate of sub-healthy pipelines and improves the drainage capability of the pipeline network in the waterlogging areas; it reduces the area at the extremely dangerous flood level by 72.9% and the area at the highest comprehensive risk level by 17%. This study provides an optimal scheme for urban stormwater process control and flood risk reduction of the city. The comprehensive risk assessment helps its disaster prevention and mitigation planning and its response to emergencies.
		2023 Vol. 42 (6): 40-52 [Abstract] ( 78 ) PDF (4594 KB) ( 252 )

	53	Study on hydrodynamic index threshold of early warning model for bank collapse in lower reaches of Yangtze River
		ZHANG Fanyi, WEN Yuncheng, WANG Xiaojun, XU Hua, JIA Menghao, XIA Mingyan
		DOI: 10.11660/slfdxb.20230606
		Previous multi-index bank-collapse prediction models are built on a river bank stability evaluation method that relies on the analytic hierarchy developed in recent years. As a key factor affecting the stability of river banks, determining the threshold values of hydrodynamic factors responding to different collapse risk levels is often empirical and lacks theoretical, systematic or practical research support. In this study, the thresholds of the key hydrodynamic factors－such as dominant discharge, flow velocity, water level variation, and channel diversion ratio change rate－are determined by integrating data statistics, theoretical derivation, numerical model calculation, and the previous results in literature. Determination of the dominant discharge threshold of a river and its water level variation threshold takes into account river-tide interactions in its tidal reach; a flow velocity factor is introduced in a formula for calculating riverbed stability. For a branched reach, the threshold of the diversion ratio change rate is calculated to distinguish its major branch channel from the minor ones, and we conclude the bank of the major branch is unstable at the diversion ratio change rate greater than 8%. The results support the development and application of an analytical bank-collapse-prediction hierarchy model for the lower Yangtze, and help prevent bank collapse disasters.
		2023 Vol. 42 (6): 53-64 [Abstract] ( 92 ) PDF (2252 KB) ( 308 )

	65	Theoretical analysis of tail vortices in radial-flow hydraulic turbine
		WANG Xiaohui, YANG Hao, MIAO Senchun, ZHANG Xingjie, JIANG Huzhong, ZHANG Kai
		DOI: 10.11660/slfdxb.20230607
		Large-scale spiral tail vortices at the outlet of a radial hydraulic turbine would affect the efficiency and stability of the machine. To reveal the flow mechanism, a Q criterion is used to identify and extract the structure of different tail vortices, focusing on analysis of velocity fields. The results show that the vortices rotate opposite to the impeller with their core radius about one third of the impeller outlet radius. We divide a tail vortex into a core zone and a decay zone by the radial profiles of its tangential velocity at the impeller outlet. Transversely, the tangential velocity increases sharply along the radius in the core zone, and peaks at the core radius; then it decreases gradually in the decay zone down to a level of roughly half the peak at the tube wall. Along the flow, its variation flattens out gradually and its peak moves gradually toward the channel wall. We find the vortex core is a zone of energy loss dominated by the kinetic energy loss of tangential velocity, which is one of the major causes of energy loss in a radial hydraulic turbine.
		2023 Vol. 42 (6): 65-72 [Abstract] ( 66 ) PDF (2904 KB) ( 181 )

	73	Experimental study on speed matching of first and secondary impellers of contra-rotating full tubular pump
		WANG Bangsheng, LIN Bin, ZHAO Guohui, ZHAO Fujian
		DOI: 10.11660/slfdxb.20230608
		This paper presents an experimental study of a dual-motor driven contra-rotating full tubular pump for tidal power generation. The first and secondary impellers of this pump adopt the same structural form, and the speed ratio of their rotators in pumping mode is examined. The results show that at the same rotational speed of the two-stage impellers, the overall head of the second stage is higher than that of the first stage, but the latter has lower shaft power and higher efficiency. At different rotational speeds of the two impellers, no hump occurs in the lift head curve of low flow conditions; the pump efficiency is improved significantly with its high hydraulic efficiency zone shifted towards the design flow point. The lift head and power of the pump are linearly related to the rotational speed of its secondary impeller; its shaft power is mainly related to the corresponding flow rate and rotational speed. A variable rotational speed can be applied to the secondary impeller to achieve an operating power equal to that of the first-stage so as to avoid the overload of its motor. The results are of great theoretical and practical significance to the hydraulic performance and the safe and stable operation of full tubular pumps.
		2023 Vol. 42 (6): 73-79 [Abstract] ( 72 ) PDF (631 KB) ( 267 )

	80	Evolution of top-level governance structure of major water conservancy projects
		DING Jiyong, WAN Xuechun, WANG Zhuofu, QIAN Fei
		DOI: 10.11660/slfdxb.20230609
		Major water conservancy projects have a high degree of complexity and great social influence, and their top-level governance structure design imposes a profound impact on project transaction governance and project management performance. Since the reform and opening-up in China, the structure has been evolving accordingly with the changes in the socioeconomic system. This paper conducts a long period, large span analysis of multiple cases on typical major water conservancy projects, and finds out that since the reform and opening-up, the top-level governance structure of the projects has evolved through three stages: the stage of the government’s role as the project owner, the stage of the project legal persons’ responsibility system led by the government, and the stage for promotion of a better combination of efficient markets and competent governments. We also find that the governance framework "government-led + market mechanism" is suitable for the situation of the socialist market economy with Chinese characteristics. Generally, project entity formation modes should be analyzed with consideration of the investment and financing mode; the optimal design of top-level governance structure should be formulated in combination with project characteristics. This study enriches the top-level theory in the theoretical governance framework of major engineering projects, useful for their top-level governance structure design.
		2023 Vol. 42 (6): 80-91 [Abstract] ( 81 ) PDF (1274 KB) ( 270 )

	92	Augmented reality feedback method for rolling quality and progress of RCC dam concrete placing area
		ZHANG Sherong, QIAN Junjie, ZHAO Dongliang, WANG Chao, WANG Xiaohua
		DOI: 10.11660/slfdxb.20230610
		Construction information such as the rolling quality and progress of roller compacted concrete (RCC) dam surface is transmitted in feedback mostly in traditional ways such as reports and pictures, which is not conducive to timely detection of construction quality defects and overall grasp of construction progress. This paper presents a solution method of fixed camera three-dimensional registration based on the Tsai two-step calibration method to realize the fixed augmented reality (AR) feedback of construction quality. And a mobile AR feedback expression method is developed for concrete placing progress information by using hybrid registration. We use the relational database and building information modeling (BIM) to interrelate construction quality information and construction progress information, so that a complementary added value of construction information is achieved. Through system development and engineering application, we show this coordinate mapping method has an error of no more than 0.5 m in the placing area and an average response time of 5.06 s, meeting the requirement of field construction. The construction progress feedback module based on mobile AR has an average frame rate of 29.55 for mobile phone use, and 96.17% of the time for the frame rate greater than 27, meeting the fluency requirement of field construction. Thus, our AR-based method provides on-site managers with multi-view construction information expression and feedback channels.
		2023 Vol. 42 (6): 92-103 [Abstract] ( 102 ) PDF (3261 KB) ( 247 )

	104	Rock mass integrity evaluation method in hydraulic engineering based on ensemble features of core images
		ZHANG Ye, CHEN Jinqiao, LI Yanlong, WEN Lifeng
		DOI: 10.11660/slfdxb.20230611
		Hydraulic engineering projects are mostly located in regions of high mountains and deep gorges with complicated geological conditions. Evaluation of the integrity of rock mass in the dam site and reservoir area is significant to the construction, but traditional evaluation, often completed manually, is laborious and of high cost. In this study, a knowledge transfer method is applied to achieve a deep feature ensemble of rock core images; then an intelligent evaluation model is developed for hydraulic rock mass integrity based on Weighted Support Vector Machine (WSVM). We compare the evaluation results obtained using a single deep model and a deep feature ensemble method, and find that the latter improves model performance better, raising the accuracy by more than 5%. We also compare WSVM with SVM and other machine learning methods. The results prove that WSVM is more effective in the intelligent evaluation of hydraulic rock mass integrity. It realizes automatic and intelligent analysis of the integrity evaluation to a certain extent, and provides a new method for geological survey and hydraulic construction.
		2023 Vol. 42 (6): 104-114 [Abstract] ( 76 ) PDF (3953 KB) ( 257 )

	115	Study on scenario earthquakes and site-related response spectra of Xiluodu arch dam
		WANG Xiangchao, SHI Hongtao, HUANG Hailong, WANG Jinting
		DOI: 10.11660/slfdxb.20230612
		Reasonable ground motion parameters are a prerequisite for seismic hazard analysis of high dams. This study investigates scenario earthquakes and the corresponding site-related response spectra for the Xiluodu dam, based on the Code for seismic design of hydraulic structures of hydropower project (NB 35047—2015) with category A of seismic protection. First, the Yongshan area with the largest contribution to the exceedance probability of this dam is selected as a potential seismic area for earthquakes; then, the magnitude and epicenter distance of the scenario earthquakes are determined by the principle of the maximum occurrence probability. Finally, the site-related response spectrum is generated using the ground-motion prediction equation AS08. This study gives a basis for seismic analysis of the Xiluodu dam based on real dynamic working state, and helps seismic analysis of similar projects.
		2023 Vol. 42 (6): 115-122 [Abstract] ( 81 ) PDF (1474 KB) ( 359 )