The resistivity method can reflect the soil physical index and structural properties, and it has the characteristics of high efficiency, convenience and non-destructive. In this study, the resistivity characteristics and the resistivity model of laterite had been analyzed using the pore water, water content and porosity as the key factors. A correction formula of contact resistance was proposed considering the influence of electrode area, and the resistivity prediction model of laterite had been established by introducing the structural factors to reflect the influence of pore water on the resistivity of laterite. The results show that the proposed contact resistivity correction formula can effectively reduce the test error, the laterite resistivity and structure factors decrease with the increasing water content and porosity with a power function relationship. The correlation of influencing factors of laterite resistivity is sorted as: pore water>water content>porosity. The resistivity prediction model of laterite was constructed with the variables of contact resistance, pore water, water content and porosity, which has high fitting accuracy. Thus, it can provide a reference for evaluating the physical indicators and structural properties of laterite.

The premise of non-conformity traceability and correction of run-off is that there is an accurate and reliable long series measured flow sequence as the calibration reference. For watersheds without long series of measured flow data, the accuracy of calculated flow can be verified through short-term and typical test data to obtain a calibration benchmark. In this study, the accuracy of NHQ curves and discharge curves of Pubugou Reservoir was analyzed and verified based on the ultrasonic flow, combined with the analysis of the level-flow relationship under stable and sudden change working conditions. The research results have proven the accuracy of the outflow calculation of Pubugou reservoir, which provided basic support for tracing and correcting the non-uniformity of cascade runoff.

Factors such as climate change have increased the spatial-temporal distribution heterogeneity of rainfall, it is thus important to study the response of hydrograph to the influence of the spatial heterogeneity of rainfall, which is of great importance to provide guidance to the hydrologic simulation of the flooding under conditions that the rainfall of the mainstream and tributary streams have different occurrence frequencies. The watershed above Linyi station of the Yihe River in Shandong Province was selected as an example. The watershed hydrological model was established using the Xinanjiang model. Hourly rainfall data from June to September from 1980 to 2020 were used for frequency analysis to obtain the design storms with different return periods in the Yihe river basin with a duration of 72 h. The flood process at Linyi station was analyzed by considering combined design scenarios of design storms with different return periods. Simulations were run using the established hydrologic model to obtain the response of flood process to the spatial heterogeneity of rainfall. The results show that the spatial distribution of rainfall has a significant impact on peak flows, with rainfall in areas close to the basin outlet being the determining factor for peak flood flows, and that smaller amounts of rainfall can produce larger peak flows in scenarios with high spatial heterogeneity of rainfall. The results can provide reference for the flood forecasting of downstream cross-sections under conditions that the mainstream and tributary floods have different occurrence frequencies due to spatial heterogeneity of rainfall.

The water intake mode of pumping station under the condition of large variable water level of water source has great impact on the reliability of water intake, project cost and safety of water intake building, so the reasonable evaluation of different water intake mode is one of the key problems in engineering design. In this paper, a two-level evaluation index system consisting of 3 quantitative indicators and 14 qualitative indicators was constructed. The analytic hierarchy process (AHP), entropy weight method and least square method were used to assign the combination of subjective and objective weights. The method of membership degree and fuzzy comprehensive evaluation was used to evaluate and rank different water intake schemes, and an engineering example was analyzed. The results show that the proposed index system is comprehensive, the weighting method is reasonable, and the evaluation method can better reflect the uncertainty of the scheme selection. The practical engineering example verified the feasibility of the evaluation method.

For water supply systems with high-lift, the pump-stopping water hammer caused by the power failure is usually greater than the direct water hammer caused by the check valve closing. Based on the Joukovsky equation and the pressure drop law behind the pump, the influence of the check valve closing law on the pressure along the pipeline was studied, and the theoretical value of the optimal closing time (i.e., T_g=T_d) was obtained when a pump trip occurred. The theoretical value was verified by numerical simulation through a practical project. The results show that for high-lift water supply projects, the theoretical closing time of the check valve can minimize the pressure drop along the pipeline when the pump trip occurred.

Aiming at the falling into locally optimal solution shortcomings of optimization algorithm and probability density method for inversion of river cross-sections in ungauged regions, this paper proposed a combination of Ensemble Kalman Filter (EnKF) method and particle swarm optimization algorithm (PSO). The PSO was used to initialize the missing section to form a trapezoidal initial section. Then the EnKF was used to correct the initial section, and the proposed method was verified by the ideal case. The results show that the R² and N_NSE of the model are higher than 0.99, and the relative mean square error is less than 0.04. Considering the observation errors in the engineering practice, the observation errors of 0.1%, 1%, 5% and 10% were selected to evaluate the hydrodynamic simulation errors of the missing section, the PSO initial section and the corrected section by the EnKF method. It is found that the errors are normally distributed with the selected errors, but the overall distribution is normal with different errors. But the EnKF method can maintain a high simulation accuracy with different observation errors, the R² is higher than 0.98, the relative mean square deviation (RMSD) is less than 0.06 m, and the N_NSE is higher than 0.98. Thus, the proposed method has a high feasibility.

Under the condition of low flow ratio, the flow structure of the inlet area of tributaries is very complicated. Based on physical model test and PIV particle image velocimetry technology, the average velocity distribution and three-dimensional velocity spatial distribution of open channel tributaries under different intersection conditions were observed, and the variation law of the flow field of tributaries was analyzed. The results show that when the confluence is relatively small, the surface water of the tributaries will have reverse reflux phenomenon to varying degrees due to the top supporting effect of the main stream water, while the bottom water flows downstream to the main stream, and there is a relatively obvious oblique mixing interface. With the increase of the confluence ratio, the influence of the main stream on the flow structure of the left bank of the tributary decreases gradually. When the intersection angle is 30° and 90°, the water flow structure near the right bank section is most affected by the water top support of the main flow. When the intersection angle is 150°, the tributaries are basically in reverse reflux state, and the maximum reflux velocity area is formed at the intersection. The results can provide theoretical support for the study of frequent bloom caused by nutrient enrichment in tributaries of reservoir area.

For underflow energy dissipation, the arrangement of the grille shortens the length of the stilling pool and makes it easier to adapt to changes in terrain conditions. The two-phase flow of water and gas in the round-bore Γ-shaped grille type stilling pool was numerically simulated by the aeration model in FLOW-3D. The results show that the concentration of longitudinal bottoming gas decreased (31.3% →8.0%) along the way, and decreased significantly at the grid position, the minimum number of holes in front of the grid (^#6 section) was 5.6, the number of holes near the grid was about 9.0, and the number of holes behind the grid was much greater than 9.0. The bubble size near the bottom of the grid front axis increases along the course (0.9 mm→8.1 mm), and the bubble size of the near bottom plate after the grid decreases along the way (1.6 mm decreases to close to 0 mm). It can be considered that the bubbles with smaller diameters in large flow velocity areas play a major role in aeration corrosion reduction, which has obvious protective effect on the solid boundary of concrete, and the structure of the stilling pool including the grid is not easy to occur cavitation erosion damage.

Aiming at the shortcomings of hydropower unit vibration signal denoising using ensemble empirical mode decomposition (EEMD), a denoising algorithm based on an improved fruit fly optimization algorithm (RFOA) for optimizing the EEMD noise IMF component threshold was proposed. Firstly, the noise signal was decomposed using the EEMD algorithm to obtain the IMF components, and then the correlation coefficient method was used to determine the noise signal and the effective signal. Then, the RFOA was used to determine the noise signal IMF component threshold. Finally, the sample entropy of the obtained IMF components was used as a feature vector input of the GRNN algorithm for vibration mode recognition. Compared with the wavelet threshold method and the EEMD-GA method, the results show that the proposed algorithm has the highest signal-to-noise ratio and the best denoising effect.

Maintaining ecological flow in a river is an important initiative to coordinate water resources development and utilization with river ecological protection. Most of the existing ecological flow calculation methods are limited by insufficient ecological data, difficult ecological modeling. In this paper, a Bayesian hierarchical model based on phytoplankton biomass was established to investigate the hydrological-ecological response relationship. The relationship between phytoplankton biomass and flow and water temperature in pre-flood, flood and post-flood periods was analyzed by taking the Shaying River as a case study. The results show that the Bayesian hierarchical model can identify the complex hydrological-ecological response relationship, and the advantage of hierarchical analysis improves the availability of short series data; The probability of biomass-flow covariate parameter β greater than 0 in pre-flood is 0.683, and the probability of less than 0 in flood is 0.577, and the guarantee of flow in the river channel in pre-flood and the control of discharge in flood have positive effects on phytoplankton biomass; Under the ecological flow conditions that meet the design requirements, the predicted maximum and minimum biomass improvements occur in river section 7 (+32.05% before flood, + 871.80% during flood, and +81.79% after flood) and river section 3 (+3.91% before flood, +1.16% during flood, and +2.89% after flood), respectively.