Analysis of rock fracture seepage plays an important role in evaluation of rock engineering safety. The three-dimensional coordinate points of the rock fracture surface were scanned by a three-dimensional structure optical scanner and visually reconstructed. Parameters such as joint roughness coefficient JRC and topography statistics were used to quantitatively describe the roughness and undulation characteristics of rock fractures. Through experimental research, it is found that when the seepage pressure gradient increases, the seepage in rock fractures will change from linear seepage to non-linear seepage, and the Forchheimer formula can better fit this process. The threshold and Reynolds number of the critical Darcy flow were obtained by introducing he nonlinear factor E. The relative loss of momentum-Euler number was introduced to study the law of fluid energy evolution in the process of fracture seepage. It is found that the Euler number shows a trend that first drops rapidly and then gradually stabilizes. The result has certain guiding significance for actual engineering.

As the most basic precipitation collection equipment in the field of hydrometeorology, the tipping bucket rain gauge has the characteristics of practicality and good stability, but there are some deficiencies in the research on the tipping characteristics and mechanism of the tipping bucket rain gauge and the causes of the mechanical error of the tipping bucket rain gauge. In this study, the mechanism of the tipping process of tipping bucket rain gauge was explored by means of combination of numerical simulation and indoor experiment with high-speed camera. The results show that during the turnover process, the time from start to stop is about 0.35-0.40 s, the time t₁ from start to level is relatively high, about 80%-85%, and the time t₂ from level to stop is only about 0.05 s, and there is a slight rebound after the turnover touches the adjusting nut. During t₁ period, water will be continuously injected into the tipping bucket, which is the fundamental reason for the change of additional water volume and mechanical error of rain gauge with rain intensity. The tipping bucket will pour out the water in a very short time (about 0.4 s), and because the tipping bucket will cause slight rebound when touching the stop bolt, it will cause the "double peak" phenomenon of the tipping flow of the rain gauge tipping bucket when pouring out the water, and it will increase with the small installation inclination of the tipping bucket on the left and right. The research results can provide basic theoretical support for the improvement of tipping bucket rain gauge in the future.

Aiming at the inability to accurately locate the fault of the transmission line in hydropower station, an improved double-end location algorithm independent of wave velocity was derived from the actual propagation theory of traveling waves. Using the unique advantages of variational mode decomposition (VMD) which can adaptively decompose fault current traveling wave signals, and the Teager energy operator (TEO) which can quickly track the energy change of signals and has less computation, a traveling wave positioning model for 220 kV transmission lines based on VMD-TEO was established. The model does not need to consider wave velocity correction and double terminal time synchronization. The simulation results of PSCAD show that the maximum error percentage of the improved double-end fault location model is 0.239%, which is superior to other location algorithms. The reliability and superiority of the proposed method were verified.

Aiming at the topology optimization of large-scale offshore wind power collection system, an improved partheno genetic algorithm was proposed. The calculation model of the present value of the life cycle cost of the power collection system was established. Taking the minimum of the sum of present value as the goal, the population generation mode meeting the current carrying capacity constraints of the submarine cable and the elimination coefficient related to the number of crossing points were designed to avoid the submarine cable crossing. The topology of the power collection system with 35 kV and 66 kV voltage levels was optimized and compared. The example results show that the total cost of the improved partheno genetic algorithm can be reduced by 14.2% compared with the traditional algorithm; Compared with 35 kV, 66 kV voltage level has better comprehensive benefits, which can provide reference for the planning and design of large-scale offshore wind farm power collection system.

The ecological security of rivers is not only closely related to the physical, chemical and biological integrity of the river itself, but also affected by the natural, economic and social conditions of the regions through which it flows. Based on the "driving force-pressur-state-function-response" (DPSFR) framework and matter-element extension model, a river ecological security evaluation system was constructed. Taking Hongru River as an example, it was divided into 10 evaluation units according to the spatial differences such as physical geography and water conservancy projects, and the river ecological security evaluation and spatial differentiation characteristics research were carried out. The results show that the ecological safety level of the Hongru River in 2017 was in a critical safety state, and there was a tendency to develop to an unsafe level. Its spatial differentiation characteristics were that the upstream was better than the downstream, and the tributaries were better than the mainstream, especially in the functional and response layers. Among the indicators, total phosphorus, per capita comprehensive water consumption, river longitudinal connectivity, and water quality assessment cross-section compliance rate are the main factors affecting the spatial distribution of ecological security differences in Hongru River. The response is a criterion layer that is significantly related to the spatial differentiation of the ecological security of the Hongru River.

To analyze the applicability of CMORPH merged hourly gridded precipitation product in Northern China, the statistical indicators between the observed grid precipitation and CMORPH merged gridded precipitation in temporal and spatial distribution of flood season from 2008 to 2012 were evaluated in the Yihe River Basin. Using the two precipitations as the input of HEC-HMS model, the feasibility of floods forecast of the CMORPH merged precipitation was evaluated. The results show that the CMORPH merged precipitation has a high correlation with the observed grid precipitation, and the flood simulation accuracy is comparable to the result of observed grid precipitation, and performing better in the simulations both runoff volume and flood peak. The satellite merged precipitation has good applicability in flood forecasting in the study area.

Rainfall observations derived from 76 ground rainfall gauges from January 1, 2018 to December 31, 2020 were used to evaluate the accuracy of IMERG Final Run (IMERG_FR) and IMERG Early Run (IMERG_ER) in IMERG (Integrated Multi-satellitE Retrievals for GPM) products over the small Sancha River basin in Guizhou Province. This study aimed to explore the precipitation detection capacity of IMERG_FR and IMERG_ER on different time scales. Metrics for assessment include correlation coefficient (C_CC), relative bias (R_RB), root-mean-squared error (R_RMSE), probability of detection (P_POD), false alarm ratio (F_FAR), critical success index (C_CSI). The performance of IMERG was assessed at different time scale with different precipitation thresholds. The results show that the IMERG_FR and IMERG_ER have a certain precipitation detection ability in the small basin on the whole, and it still needs to improve the accuracy of IMERG products in estimating precipitation intensity.

In order to study the hydraulic characteristics of staggered stepped energy dissipaters with different slopes, the flow pattern, flow field, pressure field and energy dissipation characteristics of staggered stepped and rectangular stepped energy dissipaters with slope of 1:2.0 and 1:2.5 under different flow rates were compared and studied by using the method of numerical simulation and model test. The results show that with the increase of the slope of the staggered step dissipator, the three-dimensional vortex scale formed at the step groove increases, the water flow is violent and the water depth is large. The absolute value of the vertical pressure of the step is larger, and the range of negative pressure zone increases. The horizontal pressure distribution of the step under the two slopes is similar, and the closer the step is, the smaller the pressure is. The energy dissipation rate of stepped energy dissipaters with a slope of 1:2.0 is larger. The energy dissipation rate of energy dissipaters with the same slope has a nonlinear relationship with the flow rate. The larger the flow rate is, the slower the energy dissipation rate changes. The staggered stepped energy dissipater is more fully aerated and has higher energy dissipation rate than the rectangular stepped spillway. The conclusions can provide a theoretical basis for the structural optimization of staggered stepped energy dissipater.

Naolihe National Nature Reserve is located in the hinterland of Heilongjiang Sanjiang Plain and is an important ecological function area in China. Based on remote sensing image data and hydrological data of the protected area, this paper inversed the vegetation coverage by pixel dichotomy, analyzed the spatial and temporal distribution characteristics of vegetation coverage in Naolihe Nature Reserve from 1984 to 2021, and studied the influence of precipitation and flooding frequency on vegetation coverage. Studies have shown that from 1984 to 2021, the low and middle vegetation coverage areas of Naolihe wetland first increased and then decreased, while the middle and high vegetation coverage areas showed the opposite trend. From the correlation coefficient between annual monthly precipitation and monthly vegetation coverage, the vegetation growth in Naolihe Nature Reserve is greatly affected by precipitation, which is positively correlated, and the response of vegetation coverage to precipitation is about one month behind. When the frequency of wetland flooding is between 0.45 and 0.50, the wetland vegetation grows well. The research can provide reference for Nalihe wetland ecological protection.

To analyze the impact of unsteady state friction and tube wall viscoelastic on leakage, based on the energy conservation theory of the transient flow in a closed pipeline, the leakage numerical model for the hydraulic transient pipeline was constructed considering the dynamic term in the unstable friction and the elastic viscosity effect of the pipe wall. The transient flow reverse analysis method (ITA) was improved. As a case study, Xujiaya Reservoir Irrigation District in Shandong Province was selected to carry out field experiments. The leakage process was assumed to be quasi-normal distribution. Based on the field water flow transient test data, pipeline leakage location and leakage amount were simulated. The simulated error was calculated by the ITA method. When a single point leakage occurs in the experimental pipeline, the average location error of the simulated leakage is 1.44%, and the maximum error is 6.89%, the average area error of the simulated leakage hole is 3.85%, and the maximum error is 14.77%. When multipoint leakage occurs in the experimental pipeline, the average error of the simulated leakage location is 1.31% and the maximum error is 3.91%; the average area error of the simulated leakage hole is 1.74% and the maximum error is 4.35%. The study results could provide theoretical and technical support for the leakage detection of water pipelines.