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.

To study on water replenishment effect of ecological gate in the Tarim River Basin, the MODFLOW was used to establish the numerical simulation of the two-dimensional flow movement of the groundwater profile in the Wusiman section, and to analyze the evolution process of the groundwater flow field in 4 years. On this basis, the two schemes with or without ecological sluice were predicted and compared. The results show that in the fifth year under the two prediction schemes, compared with the single main river channel, the buried depth area less than 8 m in the study area increased by 6.62% by using the ecological sluice water conveyance scheme. The ecological gates restored the groundwater level far away from the ecological area of the main river channel, and the groundwater level on the north side of the section increased by 2-3 m on average. Compared with the single main channel water conveyance, the phreatic evaporation consumed by the increment of groundwater storage per cubic meter was reduced by 24.6%. The ecological sluice solves the problem that the groundwater level is difficult to recover in the ecological area far away from the main river channel under the traditional water conveyance mode, and creates conditions for the restoration of the river network ecosystem formed by multiple branches in the middle reaches and the safety belt of biodiversity along the main stream.

The unsteady inflow process changes the hydrodynamic characteristics of the compound open channel and then determines the processes of material transfer and energy transfer in the floodplain and main channel. In order to study the influence of different unsteady inflow processes on the hydrodynamic characteristics of the compound open channel, indoor flume experiments were carried out to analyze the influence of different unsteady inflow processes on the water level, flow instability, and discharge per unit width process of the compound open channel, taking into account three factors: discharge amplitude, unsteady period, and rising duration. The results show that with the increase of discharge amplitude, the slope of wave peak growth of water level is greater than that of wave valley, and the wave height increases linearly. The discharge process of the unit width of the channel is deformed over time, and there is an obvious slow change process in the descending process of the main channel and the rising process of the floodplain. With the increase of the unsteady period, the wave peak of the water level increases, the wave valley decreases, and the wave height also increases linearly. The phenomenon of deformation of the unit width discharge of the channel over time disappears. The water level peaks and valleys change synchronously with the hydrologic skewness. When the hydrologic skewness (ratio of fluctuation water duration) is greater than 1, the rising process of the unit width discharge of the floodplain and main channel will also have an obvious slow change stage.

The Guangxi coastal of Beibu Gulf has abundant water resources, but the inter-annual distribution is uneven under the influence of El Niño/La Niña events. The Nanliu River is the largest river located in the costal of Beibu Gulf, Guangxi. Based on SWAT model, the characteristics of blue water, green water flow, and green water storage in typical El Niño/La Niña years in the river basin were quantitatively analyzed. The results show that from 1971 to 2015, the annual average blue water, green water flow, and green water storage in the river basin was 835.0 mm/year, 929.0 mm/year, and 114.0 mm/year, respectively. In the typical El Niño years (1997)/La Niña years (2007), the blue water, green water flow and green water storage in the river basin are 145.7%/51.6%, 92.4%/96.9% and 115.5%/78.3% of the multi-year average, respectively. The El Niño/La Niña event caused a significant increase/decrease in precipitation in the river basin, which mainly affected the amount of blue water. Due to humid climate in the basin, the amount of green water flow was mainly affected by solar radiation and wind speed. The research can provide an important reference for the rational and efficient utilization of water resources and the high-quality development of the region.

Conductivity is an important parameter to measure water quality. High-frequency monitoring of water conductivity plays an important role in water quality management. Due to the complexity of field conditions, equipment failure often leads to data loss. In order to improve the high-frequency monitoring data, machine learning model was used to predict the conductivity content in water body based on the meteorological and physical indexes obtained from high-frequency monitoring. The results show that the random forest regression model has the best prediction effect, with its determination coefficient R² reaching 0.996, root mean square error (R_RMSE) 1.31 μS/cm, and mean relative error (M MRE) 0.38%. The pH value contributed the most and was the dominant factor affecting the conductivity. The results are conducive to optimizing the field high-frequency monitoring system platform, improving the high-frequency monitoring data, which provides scientific basis for water quality management.

In order to analyze the influence of Poyang Lake Water Control Project on wetland vegetation habitat, MIKE21 was used to establish two-dimensional hydrodynamic model of Poyang Lake. Through the scenario of the typical years, the changes of water level and wetland vegetation growth habitat area in the main lake area and wetland nature reserve after the operation of the water conservancy project were simulated. The simulation results show that the operation of the Hydraulic Project has a great influence on the water level in the north of Songmen Mountain, and the influence degree gradually decreases from north to south. The operation of the hub has a great influence on the most suitable area and suitable habitat area of wetland vegetation in different hydrological years. The vegetation habitat surface varies greatly. After the operation of the hub, the dry year increases by 43.8 %, the normal year increases by 24.6 %, and the wet year is only 16.4 %. In October and November, the suitable habitat area can reach more than 2,000 km², accounting for about 2/3 of the total lake area, indicating that wetland vegetation will provide Siberian cranes with rich food sources and make them better survive and reproduce in wetlands. The simulation results reveal the influence of the Hydraulic Project on the change law of lake water level and wetland vegetation habitat interval under the current scheduling scheme, which can provide a theoretical reference for engineering construction and dispatching operation and maintenance.

Danjiangkou Dam is a control project for the development and protection of the Hanjiang River basin, and is also a water source project for the Middle Route Project of the South-to-North Water Transfer Project. The dam operation safety is the support and guarantee of the national strategy. After the dam heightening, the operating water head will increase, and there may be cavitation, and the downstream scour pit will move upward during the flood discharge process. In order to master the mechanical characteristics of flood discharge after heightening the dam and evaluate the safety of flood discharge structures, the parameters such as bottom flow velocity, dynamic water pressure, flow cavitation noise, and scouring under the dam are mainly observed by means of field hydraulic prototype observation, and the results of previous studies are analyzed. The observation parameters under the design water level are within the safe range. Aiming at the problem that the water tongue of the surface hole impacts the middle wall, the opening order of the flood discharge orifice is optimized. The causes of the scour holes in the flow channel and side wall after the flood season are analyzed and the treatment suggestions are put forward. The problems found and treatment measures can provide reference for similar projects.

To explore the temporal and spatial distribution and attribution of mountain torrent disaster risk in Sichuan Province, the spatial distribution difference and high-risk areas of mountain torrent risk during 1990-2020 were studied by AHP and cluster analysis methods, and the changing characteristic and driving reason were investigated. The results show that the risk of mountain torrent disasters increased from the west to the east in Sichuan Province. High-risk areas mostly existed in areas with dense river networks and high exposure and vulnerability, such as Meishan, Zigong, Neijiang, Ziyang, Suining, Guangan and Nanchong. From 1990 to 2020, the risk of mountain torrents showed an increasing trend in Sichuan Province. The proportion of areas with high and above risk increased from 17% to 34%. Increased risk levels were concentrated in central Sichuan, and most of them were from moderately high and relatively high risk transformed into high risk. In the past 30 years, the risk of mountain torrents has shown a downward trend in Sichuan Province, while the greater GDP and population density had changed vulnerability and disaster prevention capacity, leading to increasing risk level of mountain torrents in local areas. The results can provide theoretical guidance and practical support for forecast and early warn in flood disaster and disaster prevention and mitigation in Sichuan Province.

With the increase of economic development and the frequency and intensity of flood disasters, post-disaster emergency management requires rapid understanding of disaster losses. This paper firstly constructed an index system from five aspects including disaster-causing factors, disaster-bearing bodies, disaster-pregnant environment, emergency response capacity and disaster situation, and verified its rationality based on generalized gray correlation analysis. Secondly, Gaussian process regression model was introduced to pre-evaluate and simulate the economic losses of flood disasters. Finally, the method was applied to evaluate the direct economic losses of flood disasters in Beijing-Tianjin-Hebei urban agglomeration from 2010 to 2020. The results show that the generalized gray correlation analysis-Gaussian process regression model has the best fitting accuracy when comparing the simple Gaussian process regression with the neural network assessment model.

The risk of water flow compensation caused by the additional discharge of leading hydropower station has increased the difficulty of multi entity cascade hydropower optimal operation, and the backwater jacking effect of downstream hydropower stations has further increased the complexity of the model. Therefore, non-linear modeling is carried out for the flow compensation process of leading hydropower station, and the risk of flow compensation in the compensation period and the recharge period is quantified. At the same time, the impact of backwater jacking effect of downstream hydropower stations on the tail water level of leading hydropower station is considered, and then a scheduling model with the goal of maximizing the joint operation revenue of cascade hydropower stations is constructed. The analysis of the example shows that the method can more reasonably distribute the benefits between the upstream and downstream hydropower stations in the cascade basin, coordinate the conflicts of interests among the multi entity cascade hydropower stations, and improve the activity of the hydropower stations at all levels in participating in the market scheduling.