Journal of Hydroelectric Engineering

水力发电学报

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2024 Vol. 43, No. 11 Published: 2024-11-25

	1	Cumulative influences and ecological effects of cascade hydropower development on water temperature in upper Yangtze River ^Hot!
		ZHOU Yang, WANG Ning, WEN Xiaoxiong, YAN Long, TANG Caihong, ZHU Yulong, ZHANG Shanghong, YI Yujun
		DOI: 10.11660/slfdxb.20241101
		Cascade hydropower development disrupts the continuity of natural river water temperature, leading to a significant cumulative effect on the temperature and a series of ecological effects. This study examines the water temperature along the lower Jinsha River and in the Three Gorges reservoir area , and reveals its spatial and temporal variations on different scales before and after dam construction and the cumulative effects. The impact of water temperature changes on fish spawning is also discussed. The results show that after the Xiluodu and Xiangjiaba dams were constructed, the annual mean water temperature difference along the lower Jinsha becomes smaller; along the river, the annual highest temperature at the hydrological stations shows a decreasing trend, while the annual lowest is significantly elevated, especially in January and December. After the construction, the annual temperature variation is reduced, and the time period featuring water temperature distribution has a trend of ‘convergence’－the days of water temperature distribution changed from M-type to V-type. An examination on the cumulative effect indicator finds that after dam construction, a significant time crowding effect occurs－a lag time in the extreme water temperature, water temperature delayed up to 1 - 2 months, the fish of 48% and 44% affected to a high degree at the Panzhihua section and the section downstream of Xiangjiaba dam respectively－thereby affecting severely the fish spawning and reproduction in the downstream and the fish protection sections. The study demonstrates the cumulative effects of water temperature impacted by cascade dam construction and its impact on fish spawning, laying a basis to enhance the role of temperature changes caused by large-scale cascade dams and the downstream ecological restoration.
		2024 Vol. 43 (11): 1-16 [Abstract] ( 68 ) PDF (6798 KB) ( 206 )

	17	Temporal and spatial characteristics of water quality and environmental discharges in middle and lower Hanjiang River
		HE Shufeng, SHE Xingyuan, LIN Yuqing, YANG Zaoli, MO Kangle, CHEN Qiuwen
		DOI: 10.11660/slfdxb.20241102
		In recent years, water quality problems have occurred frequently in the middle and lower Hanjiang River and its environmental discharge is yet unclear, which threatens the safety of water use in the regions along it. To assess its water quality and environmental flows, this paper describes a single-factor method to evaluate their spatial and temporal distribution characteristics based on data observation. First, we collect field data for five water quality indicators－pH, dissolved oxygen, permanganate index, ammonia nitrogen, and total phosphorus－which were observed in 2015-2019 at seven control sections in the middle and lower reaches: Huangjiagang, Xiangyang, Huangzhuang, Shayang, Qianjiang, Xiantao, and Hanchuan. Then, we develop a one-dimensional hydrodynamic and water quality model and a corresponding method for calculating the environmental discharge that meets the requirement of water quality at each control section, and calculate the environmental discharges of the river using different water sources inputs. The results show two failure cases－ρ (NH3-N) in the high flow period, and ρ (TP) in the low flow period, which are unable to meet the class Ⅱ standard at the section downstream of Huangzhuang. To guarantee the environmental discharge, the operation of Water Transfer Project from Yangtze River to Hanjiang River should be combined with the discharge from the Danjiangkou reservior. In the high and low flow periods, when a flow of 500 m3/s or 350 m3/s is diverted from Yangtze, the Danjiangkou reservoir should discharge at 214 m3/s or 315 m3/s respectively to meet the demand by the river environmental discharge. This study has explored the schemes and verified their improvement on water quality security and rational allocation of the reservoir water resources.
		2024 Vol. 43 (11): 17-26 [Abstract] ( 32 ) PDF (768 KB) ( 93 )

	27	Effect of rainfall time resolutions and interpolation methods on urban waterlogging simulations
		ZHANG Yu, HOU Jingming, WANG Zhengfa, GUAN Baojun, CHEN Jie
		DOI: 10.11660/slfdxb.20241103
		This study examines the influence of rainfall data with different time resolutions on urban waterlogging simulations using a 1D-2D coupling model, namely GAST-SWMM (GPU Accelerated Surface Water Flow coupled with Transport Model-Storm Water Management Model). Different interpolation methods are used to improve time resolution, and the best one is determined. Nash coefficients and peak errors are compared to evaluate the simulated flow hydrographs against the measurements for Tianfu Heyuan District, Xi'an City. We examine three methods－fractal interpolation, Lagrange interpolation and linear interpolation－using a time interval range of 5 min to 60 min. The results show the Nash coefficient of the model is 0.85 and 0.81 for two rainfall events, indicating its high accuracy. Of the five sets of different rainfall time resolutions studied, the one of 5min gives the highest simulation accuracy. A lower resolution results in a greater deviation of the simulation from measurements, and the worst case occurs when the interval is 60 min. We find that fractal interpolation has the best agreement with measurements, followed by Lagrange interpolation, and linear interpolation is the poorest. This study can provide a basis for the selection and processing of rainfall data for urban waterlogging simulation.
		2024 Vol. 43 (11): 27-38 [Abstract] ( 19 ) PDF (3710 KB) ( 99 )

	39	Comparative study of joint and optimal operation schemes for lower Jinsha-Three Gorges-Gezhouba cascade reservoirs
		XIE Yuzuo, GUO Shenglian, ZHONG Sirui, WANG Yun, XIANG Xin
		DOI: 10.11660/slfdxb.20241104
		The design rule curves are used to simulate reservoir operation to verify the design values and obtain a benchmark for comparative study. Joint and multi-objective optimal operation models are developed for the lower Jinsha-Three Gorges-Gezhouba cascade reservoirs. We solve the optimal model and its Pareto frontier using a parameterization-simulation-optimization framework based on the Gaussian radial basis functions and a Borg many-objective evolutionary algorithm. Comparative study reveals that the design values of annual hydropower generation are reasonable and reliable, and the joint operation of cascade reservoirs must consider the backwater effect of downstream reservoirs. Compared to the rule curve scheme, the joint (optimal) operation scheme reduces water spillage by 20.38% (30.44%) and increases annual hydropower generation by 4.01% (5.45%), with significant increases in the generation by the reservoirs of Xiluodu, Xiangjiaba, and Gezhouba. Generally, a conflict between hydropower generation and impoundment efficiency occurs, and the Three Gorges Reservoir will be faced with a challenge in dry years if it starts impoundment on the tenth of September. We suggest that the Three Gorges Reservoir should optimize further its flood-limited water level and consider an earlier start of impoundment.
		2024 Vol. 43 (11): 39-48 [Abstract] ( 26 ) PDF (970 KB) ( 90 )

	49	Identifying drought events in Beijing-Tianjin region using three-dimensional approach
		Lina Tuoku, MEN Baohui, LIU Nan, LYU Xing
		DOI: 10.11660/slfdxb.20241105
		The Beijing-Tianjin region, economically developed and densely populated, is highly vulnerable to drought events, which poses a challenge to its socio-economic development and water security. This paper presents a method for identifying droughts using a three-dimensional approach that considers longitude, latitude, and time, and an application of the Standardized Vegetation Index (SVCI) to detection of the drought events in this region. We quantify the events based on duration, area share, and intensity, and examine their frequencies and return periods using the Copula function. The results show the drought events identified using SVCI align with those recorded in literature, indicating the results of this study are reliable. In the study region, totally 48 drought events occurred from 1982 to 2020, with 34 lasting three months or longer. Compared to its two-dimensional version, the three-dimensional Copula function is more effective in fitting the joint distributions of drought variables in the region, considering more factors for better fitting.
		2024 Vol. 43 (11): 49-58 [Abstract] ( 23 ) PDF (1885 KB) ( 61 )

	59	Study on calculation methods of medium- and long-term multi-scale peaking shaving capacity of hydropower stations
		AI Xueshan, HUANG Kui, SHI Xuanyu, ZHAO Longqing, LIU Fengshuo, YU Yangxin
		DOI: 10.11660/slfdxb.20241106
		Peak load balancing ability is a key characteristic index to measure the performance of a hydropower station. To operate a regional power grid with new energy sources such as wind and solar power, a task of great significance is to conduct studies on the medium- and long-term peak load shaving capacity of the hydropower stations, so as to improve its new energy absorption and long-term stable operation. This paper presents a calculation method of daily peak load－a basis for determining the peak load shaving capacity on each scale－that is based on the historical typical daily load process corresponding to multiple time scales, and extracts the typical daily load proportion on each scale using the clustering by fast search and find of density peak (CFSFDP) algorithm. We develop a scheduling model of the corresponding calculation periods and time scales with the target of maximized peak power load, and examine the optimization scheduling on different scales－annual monthly scale, monthly ten-day scale, and intra-ten day scale. Application in a case study of the Longtan hydropower station with an annual regulation capacity shows that this method helps the decision-making for regional power grids to carry out medium- and long-term power balance, and it is an effective tool to schedule the peak power load of cascade hydropower stations on various time scales.
		2024 Vol. 43 (11): 59-70 [Abstract] ( 27 ) PDF (1679 KB) ( 72 )

	71	Experimental study on rainfall-runoff process and sediment erosion on steep slopes in mountain regions
		TONG Xiaoxia, CUI Yuanlai, SHAO Dongguo, LI Jianming, DING Wenfeng, ZHANG Guanhua, CHEN Jinyang
		DOI: 10.11660/slfdxb.20241107
		In this work, we conduct a laboratory experiment to simulate continuous rainfall based on four designed soil tanks to clarify the interaction effects of different rainfall intensities, soil layer thickness distribution, and soil base permeability on runoff generation and sediment erosion on hillslopes. The results show that the surface runoff rate takes an increasing trend with significant fluctuations during continuous rainfall, and the average erosion rate shows a trend of increasing first and then decreasing. The surface runoff rate is influenced mainly by rainfall intensity, with a variance contribution rate of 88.85%; the erosion rate is affected primarily by rainfall intensity and its interaction with soil layer thickness distribution, with variance contribution rates of 46.13% and 20.64%, respectively. And the interaction between soil layer thickness distribution and soil base permeability also has a certain impact on the erosion rate, with a variance contribution rate of 9.21%. Therefore, besides rainfall intensity, we should consider the factors of soil layer thickness, soil base permeability, and their interactive effects on the runoff and sediment yield process. This study would lay a basis for understanding the mechanisms of runoff generation and sediment erosion on hillslopes under complex underlying conditions.
		2024 Vol. 43 (11): 71-80 [Abstract] ( 31 ) PDF (2253 KB) ( 68 )

	81	Cavity evolution in flows around active rotating hydrofoil
		LI Yanhao, WANG Yifu, YU An
		DOI: 10.11660/slfdxb.20241108
		In the construction of a new power system with a high proportion of new energy, the cavitation characteristics of guide vanes and blades in hydropower units, especially pumped storage units under switch condition are quite different from stable condition, and the cavitation development mechanism is worthy of further study. This study examines the flows around a hydrofoil that oscillates in two different modes based on filter correction (FBM) and a Zwart-Gerber-Belamri cavitation model, focusing on the characteristics of flow cavitating evolution and the influences of different modes on the dynamic characteristics of cavitation. The numerical results of the cavitation shapes and velocity vectors around a NACA0015 foil are analyzed, the influencing mechanism of cavity evolution and the hydrodynamic parameters of its oscillating motions are explored. The results show that in the head fixed mode, foil oscillation induces larger cavities and a higher time-average volume fraction of vapor phase than the tail fixed oscillation, and the volume is larger. Under sheet cavitation in the two modes, the overall volume curves of vapor phase are very similar, while they are significantly different under cloud cavitation that differs in form.
		2024 Vol. 43 (11): 81-91 [Abstract] ( 32 ) PDF (2897 KB) ( 80 )

	92	Dynamic stress prediction and fatigue analysis of centrifugal pump impeller based on long short-term memory network
		QIAO Fengquan, SUN Yi, WU Songquan, ZHANG Pengchang, FANG Mingkun, ZHANG Fangfang, TAO Ran
		DOI: 10.11660/slfdxb.20241109
		Low-speed centrifugal pumps are prone to stress concentration issues during operation, which, along with dynamic stress variations, may lead to fatigue damage. Traditional finite element methods are limited in predicting fatigue life accurately. This paper describes a new fatigue life prediction method based on Long Short-Term Memory (LSTM) networks. It predicts the pump's operational life under different conditions, using LSTM networks to train and predict dynamic stress time series signals under rated and low-flow conditions, and integrating fatigue life models. Results show that this LSTM model captures stress variations accurately and can achieve fitting performance under rated conditions superior to that under low-flow conditions. The prediction set under rated conditions has a Mean Absolute Percentage Error (MAPE) of 21.3% lower than that under low-flow conditions. The operational life achieves 3×108 cycles under predicted stress of 2.28×107 Pa, meeting the life requirements of high-intensity operation. As a reliable, useful tool for pump management and maintenance, our method improves significantly the accuracy of centrifugal pump operational life prediction.
		2024 Vol. 43 (11): 92-102 [Abstract] ( 32 ) PDF (4368 KB) ( 66 )

	103	Influence of erosion models on calculations of sediment erosion in solid-liquid two-phase flows
		ZHANG Zichao, CHANG Fengxiang, LI Jiaxing, ZHAO Sanya, LI Yanpin
		DOI: 10.11660/slfdxb.20241110
		The Yellow River carries huge amount of suspended particles, which would cause sediment erosion on flowing components of hydraulic turbines. The selection of a proper erosion model is crucial for the accurate numerical prediction of the erosion depth. In this study, four erosion models are applied respectively to numerically simulate the solid-liquid two-phase flow in a right-angle bend under the conditions of two particle diameters and two flow velocities. By comparing the predicted erosion depth with previous experimental data in literature, we screen out suitable erosion models for the numerical simulation of erosion caused by suspended sediments from the Yellow River. The results show the erosion zones are concentrated on the connecting sections of the upstream and downstream turbine pipelines and the downstream circumferential locations of 90°and 270°, and erosion caused by large particles can also be observed in the range of 90° - 270°. In general, both the Tusla model and Oka model could perform better accuracy. The Oka model is recommend for simulations with larger sediment particles, which is equipped with the factor of sediment particle diameter and is superior in accuracy. The Tusla model, yielding the highest accuracy, has better performance in small sediment particle conditions. Oriented to the hydropower stations in the Yellow River basin, this study suggests the selection of proper numerical model for sediment erosion simulation.
		2024 Vol. 43 (11): 103-113 [Abstract] ( 20 ) PDF (7496 KB) ( 41 )

	114	Multi-label text intelligent classification method for construction safety hazards of hydropower projects
		ZHOU Jiayi, ZHENG Xiazhong, TIAN Dan, CHEN Yun
		DOI: 10.11660/slfdxb.20241111
		In water conservancy and hydropower projects, construction safety hazards come large in volume and are usually diversified in forms and types. The same hidden danger may involve multiple types, but the definition of its types is ambiguous; previous classification of hazard types is mostly dominated by manual experience, easily leading to confusion and difficulty in hazard management. To address such issues, this paper presents a multi-label intelligent identification method for construction safety hazards in hydropower projects. First, the ALBERT model is used to encode text information to achieve a high-precision quantification of the unstructured risk texts. Then, we construct a multi-label intelligent classification model of safety hazards text to improve identification efficiency, considering the content weight of the Chinese text for safety hazards and using the Bidirectional Gated Recurrent Unit (Bi-GRU) improved by the Attention mechanism. Finally, the performance of this method is tested using the texts of hydropower engineering construction safety hazards, verifying its F1 value reaches 92.11% compared with previous text classification methods. It is proved applicable, as a useful support to safety management of hydropower construction and analysis of its safety hazards.
		2024 Vol. 43 (11): 114-124 [Abstract] ( 27 ) PDF (627 KB) ( 86 )