The flow field characteristics of vortex setting chamber (VSC) play a decisive role in its water and sediment separation performance. In order to clarify the influence of the inclination angle of the curved deflector on the flow field characteristics of VSC, the large eddy simulation and VOF method are used to study the three-dimensional flow field characteristics of the VSC when the inclination angles of the curved deflector are 5°, 10° and 15° respectively, and the flow field characteristics of the VSC with the plane deflector under the same inlet flow rate are compared. The results show that the use of curved cantilever deflector will increase the eddy current intensity in the VSC chamber and reduce the range of low velocity zone. The increase of the inclination angle can improve the stability of the air vortex, increase the strength and size of the air vortex, which is beneficial to the separation of water and sediment. The radial velocity in the cone area increases with the increase of the inclination angle, and basically points to the center of the VSC, which is conducive to the rapid transport of sediment to the bottom hole of the sediment discharge. The velocity of the overflow flow on the surface of the curved deflector is greater than that on the surface of the plane deflector, and the flow velocity on the deflector is the largest when the inclination angle is 15°.

In order to solve the problem that the current existing precipitation trend analysis methods cannot simultaneously detect precipitation trends in low and high value areas, this article introduces innovative trend analysis (ITA) and combines it with traditional trend analysis methods for analysis. Taking the station data of Yili River basin from 1961 to 2020 as an example, the ITA and Mann-Kendall (MK) series, Theil Sen and other seven methods are compared and analyzed. The results show that the annual precipitation of stations in Yili River basin, except Huocheng Station, Yining County Station and Zhaosu Station, increases significantly in other stations in high value areas, which is the same as the trend of annual extreme precipitation; The extreme precipitation intensity in the low and median areas of other stations shows an increasing trend, while the high value areas show a decreasing trend, and the overall trend is increasing; The ITA can reflect the range of rainfall changes and detect the trend changes of rainfall in low, medium, and high value areas. Therefore, the combination of ITA and traditional trend method to conduct trend analysis on the overall rainfall and rainfall in high and low regions simultaneously will help to more comprehensively analyze the precipitation change law of Yili River basin.

In view of the relatively serious drought in the Feiyun River basin in recent years, the inability to effectively utilize the regulating capacity of the counter-regulating reservoir, and the inability to effectively guarantee the timeliness and scientificity of the operation, which affect the water supply safety of nearly 6 million people in Wenzhou, the anti-drought operation model and data center of the Feiyun River basin are established. The real-time data of rainfall, water level, water supply flow and ecological flow of multiple reservoirs in the basin are quoted. The meteorological data including 1 h, 3 h, 6 h short-term and imminent grid forecast data, and 1 d, 3 d, 7 d, 15 d, 30 d, 90 d and other long-term rainfall forecast data are introduced. Combined with water and soil moisture in the basin, reservoir and basin evaporation, support vector regression (SVR) calculation method is used to develop a distributed digital twinning business system based on SPARK components, which realizes early warning of available water supply, drought-resistant water level early warning, drought-resistant days early warning and ecological flow early warning, increases the use of the anti-regulation storage capacity of 2.8 million cubic meters and the reserve storage capacity of 2.93 million cubic meters. Thus, it provides data basis and technical support for the drought-resistant decision-making, scientific scheduling and "four pre-" realization in the Feiyun River basin.

Dry-wet cycle effect is an important factor affecting slope stability in red mudstone reservoir area. Triaxial consolidation undrained shear experiments, CT scans and high precision scanning electron microscopy experiments were carried out to investigate the mechanical and fracture evolution characteristics of in situ weathered mudstones during dry and wet cycles. The results show that the stress-strain relationship of red-bed mudstone presents strain softening characteristics at low confining pressures and strain hardening characteristics at high confining pressures. The shear strength parameters of red-bed mudstone decrease gradually during the dry-wet cycle. The volume content of cracks decreases exponentially with the increase of the time of dry-wet cycles, and has a negative linear correlation with cohesion function. The microstructure of mudstone gradually breaks down in the process of dry-wet cycles, leading to the connectivity of cracks and the attenuation of mechanical properties.

In view of the lack of research on the creep characteristics of hydraulic concrete in water from mesoscale scale, a meso-finite element model of concrete specimen of "aggregate-mortar-transition layer" was established. Based on the test data of tensile and compressive creep in water, the method of "orthogonal design-neural network-meso-finite element calculation" was adopted to implement the inversion analysis of the tensile and compressive specific creep of hydraulic concrete specimens at mesoscale. Finally, the relationship between tensile and compressive specific creep of hydraulic concrete and mortar was compared. The results show that the variation law of tension creep degree of hydraulic concrete in water is similar to that in sealed. The creep degree of mortar water is 2.4 times of hydraulic concrete water under conditions of tensile and compressive creep.

Rainfall will affect the characteristics of slope flow field. Due to the continuous flow of fluid, the surface runoff and slope seepage usually exist a coupling linkage phenomenon. The surface runoff is described by the N-S equation, while the Darcy’s law is used to describe the seepage in the slope. The analytical solutions of velocity distribution, pressure and discharge as well as the semi-analytical solution of runoff surface line are derived by the separation of variables method under the velocity slipping boundary condition at the interface between runoff and soil. In addition, the explicit Runge-Kutta method is adopted to solve the water depth, velocity and discharge values at different locations. The results show that the steeper the slope is, the faster the fluid movement and the shallower the water depth is. The greater the rainfall intensity is, the deeper the overall water depth is. The flow velocity at the slope surface is not equal to 0. The closer to the downstream, the larger the proportion of runoff flow discharge is. The study can provide reference for the research of the slope flow field characteristics.

River bank collapse is very common in natural rivers and plays an important role in the evolution of river channels. In order to quantitatively study the influence of river bank soil properties and bank slope inclination on river bank stability, the BSTEM model for calculating river bank stability and bank toe erosion was adopted, and six typical river bank materials were selected to study the stability of homogeneous river banks under six bank slope inclination angles. Under the condition of ignoring the water table, the collapse modes of non-cohesive bank slope and cohesive bank slope are different. For non-cohesive bank, the dominant factor affecting bank stability is the effective internal friction angle. The larger the effective internal friction angle is, the more stable the bank is. For cohesive bank, the dominant factor affecting the stability of the cohesive bank is effective cohesion. The greater the effective cohesion is, the more stable the bank is. When the effective cohesion difference is the same, the smaller the absolute value of the effective internal friction angle difference is, the more the safety factor increases. The increase of bank slope inclination reduces river bank stability and the safety factor. The larger the effective internal friction angle of the non-cohesive bank is, the more sensitive the safety factor to the change of bank slope inclination is. For cohesive banks, the greater the effective cohesion is, the more sensitive the safety factor to the change of bank slope inclination is.

In order to address the limitations of the existing vibration trend prediction model for hydroelectric units, a vibration trend prediction method for hydroelectric units based on optimal variational mode decomposition (OVMD), time-varying filter empirical mode decomposition (TVFEMD), hunter-prey optimization algorithm (HPO), and extreme learning machine (ELM) is proposed. This method first applies OVMD to adaptively decompose the original vibration signal of the hydroelectric unit, and then further employs TVFEMD to perform a secondary decomposition of the residuals obtained from the first decomposition. Subsequently, vibration trend prediction models HPO-ELM are established for each subsequence. The final predicted vibration signal is obtained by aggregating and reconstructing the prediction results of all the sub-sequences. The research results demonstrate that this method outperforms traditional methods in terms of prediction accuracy for the vibration trend of hydroelectric units, and it has good engineering application value.

The study of classified water price can provide scientific basis for the rational formulation of agricultural water price, which is of great significance for guaranteeing the benign operation of irrigated areas and promoting the high quality development of regional agriculture. Taking grain and oil crops as the research object, two evaluation indexes of irrigation benefit apportionment coefficient and irrigation water output were selected to define the irrigation benefit apportionment coefficient by emergy theory. The agricultural water price share evaluation system of different crops was constructed based on entropy weight method, and the irrigation classified water price evaluation model was established and applied in Baojixia irrigation district of Xianyang City. The results show that the share coefficient of irrigation benefit was 0.42, the share of agricultural water price of grain and oil crops was 0.37, and that of cash crops was 0.63. For agricultural water supply at full cost, the agricultural water price of grain and oil crops was 0.485 yuan/m³, and that of cash crops was 0.827 yuan/m³. As for the water price of agricultural water supply operation cost, the agricultural water price of grain and oil crops was 0.377 yuan/m³, and that of cash crops was 0.641 yuan/m³.

After the Deneng Xiangjiang Hydropower Station replaced the 4-blade runner with a 5-blade runner, the unit started experiencing severe vibrations, which eventually led to coupling vibrations in the powerhouse structure and posed significant safety hazards. This paper explores the vibration source and employs Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) methods for analysis. Finally, modal verification through actual measurements validates the relevant conclusions. The study reveals that the resonance is caused by the multiple frequency relationship between the runner blade rotational frequency and the natural frequencies of the powerhouse structure. The research on the vibration issue at this power station hold great practical value.