Malfunctions resulting from rub-impact between moving and stationary parts of bulb tubular unit will jeopardize the safety and stability of hydropower units. Aiming at the bulb tubular unit shaft rubbing system, a coupled bending-torsional rotor-runner system with faulty oil receiver under multi-vibration source and corresponding differential equation were established. The Floquet theory was applied to investigate the stability of periodic solution. The results reveal that when faulty oil receiver is taken into account, the system dynamic feature alters dramatically, which aggravates the possibility of system instability and alternates frequency transition between steady and non-steady state. This fault aggravates the unsteady vibration characteristics of different rotating parts, especially for the runner structure response trend, which needs to be paid enough attention. The results can provide useful references for safe operation and stability analysis of bulb tubular units.

In the hydraulic transition calculation of long-distance water transmission pipeline, the intake and exhaust coefficient of air valve is mostly constant. In order to explore the influence of the intake and exhaust coefficient of water hammer air valve on the change of pipeline pressure, the DN100 water hammer air valve was simulated by FLUENT software to obtain the mass flow at -9 kPa -11 kPa, and the dynamic intake and exhaust coefficient curves with different pressure differences were established. Taking Xishan primary water lift pump station as an example, dynamic value and fixed value were adopted for air valve inlet and exhaust coefficient respectively (mean value 0.55) to calculate and compare the transition process. The numerical simulation results show that the improved dynamic inlet and exhaust coefficient of the air valve has little impact on the negative pressure of the pipeline and great impact on the positive pressure. The improved dynamic inlet and exhaust coefficient effectively reduces the pressure fluctuation in the pipeline. In the actual operation of the pump station, it is necessary to pay attention to the positive pressure change of the pipeline, and strengthen protection. The calculation of water hammer prevention should be based on the measured data of air valve inlet and exhaust. The research results can provide some references for the hydraulic transition calculation of air valve in the operation of pump station.

In order to explore the spatiotemporal characteristics of water quality and its correlation with land use type in the middle and lower reaches of the Chanba River, sampling and monitoring were conducted in April (wet period), August (flow period) and December (dry period) of 2019 based on seventeen sampling sites. The spatial-temporal characteristics of water quality and the identification of main pollution factors were analyzed by employing multivariate statistical, and the relationship between the land use type and water quality indexes was studied by the method of Spearman analysis. The results show that water quality had spatial and temporal characteristics in the middle and lower reaches of Chanba River in 2019. In terms of time, the concentration values of NH₃-N, TP and COD_Mn were maximum in flow period; The order of TP and COD_Mn was sorted as flow period > wet period > dry period. Spatially, the concentrations of NH3-N, TP and COD_Mn basically increased from the middle reaches to the lower reaches. Influenced by human activities along the river, the water quality was mainly polluted by nutrient and organic matter in the middle and lower reaches of Chanba river. Construction land had a positive correlation with pollutants and played a "source" role, while forest had a negative correlation with pollutants and played a "sink" role. The results can provide reference for water environmental management in Chanba River Basin.

Analyzing the hydrological response of mining activities in the Loess Plateau will help to promote ecological protection and high-quality development in mining areas. This paper selected four typical small watersheds of Baima River, Songta River, Xinshui River and Zhouchuan River on the Loess Plateau, and conducted a study on the applicability of 8 base flow segmentation methods in the Loess Plateau. The difference of anomaly cumulative percentages (DACP) based on paired watersheds was employed to analyze the impact of mining disturbances on the base flow process in the basin. The results show that the Chapman-Maxwell filtering method and the Eckhardt filtering method have the best applicability in the typical small watersheds of the Loess Plateau, the segmented base flow is relatively stable, and the base flow hydrograph conforms to the precipitation and runoff mechanism and the water regression process of the watershed; The base flow of the four small watersheds showed significant downward trends from 1956 to 2012 as a whole; With the increase of mining disturbance intensity, the DACP index of base flow increased, and mining disturbance increased the base flow of the basin.

In order to study the adjustment characteristics and response of the important shoals in the bar area of the Yangtze River estuary under the influence of sediment discharge decreasing and human activities, this article took the Hengsha shoal, the Jiuduansha shoal and the eastern Nanhui beach as examples. The measured hydrological and topographic data were used to investigate the morphological adjustment of the shoals and the response to changed environment. The results show that in recent years, the two-dimensional geomorphology of the shoals were shrank in the bar area of the Yangtze River estuary, and the tail of the shoals stop progradation in general. The Hengsha shoal and Jiuduansha shoal had different degrees of tidal creeks development; Empirical relationships were developed between the areas of the Hengsha shoal and the previous seven-year average fluvial erosion intensity during flood seasons. This relationship can be used to reflect the change tendency of shoal’s area with the altered flow and sediment regime; The estuarine regulation project can restrain some part of the shoal’s erosion, which was caused by the variation of the flow and sediment conditions. However, the estuarine regulation project may have a slow and long-term cumulative impact on the surrounding regions.

In order to optimize the dispatching mode of Luntan hydropower plant, the process of socio-economic and ecological water demand in the downstream were analyzed. Considering the downstream water demand, the monthly generation dispatching function were extracted from the results of optimal generation dispatching by use of stepwise regression method. The results show that the dispatching of Luntan reservoir plays a great role in the downstream water demand process. The main period of water replenishment is from July to the following February, which directly changes the process of power generation diversion flow of Luntan hydropower plant. The NSE coefficients of the generation dispatching function of Luntan hydropower plant based on multiple linear regression model and BP neural network are greater than 0.90 in most months. Considering the advantages of simple structure and convenient implementation, the generation dispatching function based on multiple linear regression model is selected for Luntan hydropower plant. Compared with the results of actual dispatching and dispatching diagram of Luntan hydropower plant, the generation capacity of the dispatching function is increased by 338.4×10⁴ kW·h/month and 183.8×10⁴ kW·h/month from March 2017 to February 2019, respectively. As a result, the water level of Luntan Reservoir can be significantly increased by use of the dispatching function. The research can provide a support for the generation optimal dispatching process of Luntan hydropower plant, and provide a useful reference for many other hydropower plants to improve the practical way of the generation dispatching.

In order to evaluate the quality of "stepped" concrete cut-off wall of Hejiagou reservoir dam, the ground penetrating radar was used to detect the whole cut-off wall, and the cross-hole ultrasonic method was used to detect the " steps" of the concrete cut-off wall. The detection shows that the overall quality of the cut-off wall is good. Core drilling and water pressure test were carried out in the areas where there may be abnormalities, and the quality of the cut-off wall was comprehensively evaluated in combination with the monitoring data of the osmometer in front of and behind the cutoff wall. The results show that no major quality defects are found on the cutoff wall, local abnormalities exist, and the overall working performance is normal. This comprehensive geophysical detection method can effectively reflect the actual quality of the "stepped" cutoff wall, and the comprehensive utilization of relevant technologies can provide reference for similar projects.

To study the evolution law of member properties of hydraulic concrete materials under the coupling effect of freeze thaw cycles and salt erosion, early frozen specimens with different air-entraining agent admixtures (0, 0.005%, 0.01%) were selected and placed in a composite solution with a mass fraction of 3.5% sodium chloride +5% sodium sulfate for freeze-thaw cycle tests. Based on nuclear magnetic resonance (NMR)-fractal theory, the coupling relationship between the fractal dimension of the concrete pore volume and the damage degree of the specimens was constructed. The results show that the addition of air-entraining agents in concrete materials in appropriate amounts can effectively improve the mechanical properties such as elastic modulus and compressive strength of the members under the effect of salt freezing, and can improve the pore structure and frost resistance. The fractal dimension of concrete pore volume tested by nuclear magnetic resonance gradually decreases with the increase of freeze-thaw cycles, which indicates that the addition of air-entraining agent can change the internal pore structure of concrete in the initial state, and the effect is more obvious with the increase of air-entraining agent mixture. The correlation model between fractal dimension of pore volume and compressive strength was established by combining fractal theory, and the best functional relationship between fractal dimension D_MAX and compressive strength was found to be approximately exponential function. The regression coefficients R² is greater than 0.85, and the fitting effect is ideal, which provides a reference for durability assessment of concrete structures.

As a key point in early-warning of river system health, alert source verification is an important basis for eliminating hidden trouble and maintaining the river system health. Based on the analysis of the alarm source factors affecting the health status of Dongjiang river system, the alarm source index system was constructed, and the alert sources verification model of Dongjiang river system health was established by the partial least squares regression (PLSR) method. This model was used to verify main alarm source factors for affecting the health status of the Dongjiang river system (2015-2019), and the influence trend and degree of different alarm source factor on the health status of Dongjiang river system were analyzed. The results show that annual rainfall is the most direct and significant positive effect factor on the health status of Dongjiang River system. In addition, factors such as ecological water use, social development and river management level in this basin also play a promoting role. However, the flood disaster, sewage discharge, water for production and living, non-eco-friendly water conservancy facilities in this basin, and inter-basin water transfer have obvious negative effects on the health of Dongjiang river system.

The safe and economic support of pressure tunnel under the condition of high head and low crustal stress has always been a difficult design problem in water conservancy and hydropower projects. Based on the diversion and power generation pressure tunnel of Coca Codo Sinclair hydropower station in Ecuador, the combined support type of steel lining and reinforced concrete permeable lining was adopted within the framework of the Norwegian guidelines. The coupling theoretical model of steel lining and reinforced concrete permeable lining considering the influence of crustal stress was constructed to determine the starting point of steel lining. Based on the three-dimensional seepage field analysis, the optimal grouting depth and pressure of reinforced concrete permeable lining of high-pressure tunnel were determined. The analysis of monitoring data during operation shows that the selection of various indexes of the combined support of the pressure tunnel is appropriate. This study effectively solves the problem of safe and economic support of high head and low crustal stress tunnel, and ensures the safety and stability of pressure tunnel structure.