Riverbed roughness is an important aspect of river dynamics research， and its quantitative measurement has always been challenging. In this experiment， regardless of the macroscopic undulation of the riverbed， we laid the initial bed surface in a straight channel with non-uniform natural sand and thickened it by gradually increasing the flow rate of water. Laser scanning technology was used to obtain high-resolution bed elevation data after each bed roughening. Statistical theory and variogram function were used to investigate the surface roughness characteristics of riverbeds with varying degrees of coarseness， and to deepen the understanding of their statistical characteristics. The study's main finding is that artificially laid non-uniform sand presents an elevation frequency distribution that approximates a normal distribution. On the contrary， the frequency distribution of the stable rough bed surface formed by the continuous cumulative erosion of different flow intensities shows a slight positive deviation trend. The study found evidence that the increase of flow intensity leads strictly to an associated elevation standard deviation increase. This finding indicates that elevation standard deviation can be used as a reliable indicator to measure the characteristics of riverbed roughness in future studies. The study revealed that the kurtosis of the bed elevation data precisely decreased monotonically with the flow intensity， and that skewness and kurtosis showed a monotonic trend， indicating that they can be used to measure bed roughness. Additionally， the study found that the flow forming the bed surface is anisotropic， and as flow intensity increases， the rough layer breaks and becomes rougher again. This leads to an increase in the base value of the two-dimensional bed elevation variogram. Therefore， the study suggests that the base value of the two-dimensional variogram could serve as another reliable index for evaluating bed surface roughness. In addition， due to the influence of water flow， although the change trend of the characteristic parameters of the average variogram along the flow direction， vertical flow direction and radial profile elevation is consistent， the average variogram base value and golden point value of the transverse section are slightly larger than those of the transverse and longitudinal sections. Conversely， in the radial section， the abutment value and nugget value are considerably smaller than the values in transverse and longitudinal sections. In conclusion， this study enhances our understanding of the characteristics of bed roughness and provides crucial insights into statistical expressions for quantifying it.

Under the long-term effect of the flow load， the local scour around the bridge pier foundation is extremely prone to occur. Local scour of bridge pier foundation is one of the important factors of bridge failures， and seriously affects the safety and stability of bridges. Therefore， it is especially important to study the local scour reduction measures for bridge piers. As a classical scour reduction measure， the collar can effectively weaken the local scour around the bridge pier foundation. In order to study the local scour reduction around cylindrical bridge piers affected by the collar thickness， a three-dimensional numerical model of pier-flow-sediment is established based on the numerical simulation software Flow-3D. Then the reliability of the model is verified by the Melville classical experimental data， and the validated model is used to study the effect of the change of collar thickness on the local scour depth of bridge piers and the local scour pit morphology of bridge piers. The results show that the scour reduction effect of the collar on the front and rear of the bridge pier is better than that on both sides of the pier. The increase in collar thickness will aggravate the local scour around the bridge pier， especially on both sides of the pier. Under the selected test conditions， the local scour depth around the bridge pier is the smallest， and the scour reduction effect is the best when the collar thickness is 0.05D （D is the diameter of the bridge pier）. The scour reduction efficiency can reach 54.4% at this time. The research findings serve as a reference for the local scour protection of bridge piers.

With the development of industrialization and urbanization， untreated domestic sewage， industrial sewage and pollutants of surface runoff in the rainy season are discharged into the river system， leading to the serious urban water pollution. Due to the complexity and variability of the sources of urban polluted water bodies and environmental conditions， the current river restoration focuses on the rapid recovery of water quality， but does not fundamentally clarify the source of pollution， and does not consider the restoration of river water ecosystem damage. It leads to the fact that urban river is characterized with poor ability of self-purification and imperfect biodiversity， meanwhile， it is difficult to maintain and continuously improve water quality. This paper systematically illustrates the development process and inherent science of the concept of near naturalization restoration and urban sponge city. Both of them have separate characteristics， the concept and measures of which have commonality with the urban river restoration. The ecological restoration under the guidance of near-naturalization concept is beneficial to restore the hydrological continuity of river channels， to reshape the meandering and winding landscape of rivers， to increase the biodiversity index， making full use of their original ecological functions and values. Whereas， the concept of sponge city can effectively reduce surface runoff， purify， accumulate， utilize rainwater and alleviate the discharge of pollutants into river or water bodies. They also contribute to the mitigation of flooding risk and improvement of river dredging and drainage functions. In addition， this paper summarizes the near-naturalized and sponge city part from the project carried out in Fuyang City， Anhui Province. Through the combination technology of “source control， pollution interception， dredging， water diversion and management”， ecological restoration makes the near naturalization and sponge city integrated， which also emphasizes the construction of food chain system and greening management in the river channels. The two concepts focus on the restoration of self-purification capacity of the river and the reconstruction of ecosystem integrity， emphasize the treatment and reuse of rainwater resources， achieving the harmonious development of urban ecological restoration and landscape. Finally， to ensure the sound cycle and sustainable development of urban water ecosystem， the paper develops the direction of urban river restoration under the concept of near naturalization and sponge city intersection based on the current advanced environmental remediation and administration of domestic and foreign countries. It mainly includes two aspects： one is that the river restoration should be implemented in combination with the over-all planning of urban areas， making the river channel construction as an organic component of urban landscape； the other one is to gradually establish the evaluation indicators and standard for urban river restoration， including the traditional water quality indicators and those indicators related to the biological habitat and biodiversity.

Dams are important structures that provide various benefits， such as hydroelectric power generation， irrigation， and flood control. However， dam failures can lead to catastrophic consequences， causing significant economic and human losses. Therefore， predicting the potential impact of a dam break is crucial for ensuring the safety of people and property downstream. The width of the breach is a critical factor in estimating the flooded area downstream of an earth-rock dam during a dam break. Traditional empirical formulas developed by the Scientific Research Institute of the Ministry of Railways and the Yellow River Water Conservancy Commission are used to estimate the width of the breach， taking into account the storage capacity， length， and height of the dam. However， these formulas have been found to have significant errors when compared to actual breach widths observed in dam break cases at home and abroad. To improve the accuracy of these formulas， this paper uses an allometric model to fit the data from seven dam break cases， resulting in an optimization formula for calculating the width of the breach. The new formula takes into account the length， height， and storage capacity of the dam， as well as the degree of compaction of the soil in the dam body. The optimized formula has been found to have a maximum error of only 4.5% when compared to actual breach widths， indicating that it is more accurate than the traditional empirical formulas. The optimization formula proposed in this study provides a more accurate method for estimating the width of the breach in earth-rock dam breaks， and can be used to improve the accuracy of calculations for maximum flow rate. The results of this study can also have significant implications for dam safety engineering， as well as for the development of effective emergency response plans in the event of a dam break. In addition， the DBFL-IWHR model is used to simulate the downstream flood evolution and compared with the traditional empirical formula. The DBFL-IWHR model is a two-dimensional hydrodynamic model that takes into account the complex interactions between the water flow and the topography of the river channel. The results show that the maximum flow rate calculated by the traditional formula is lower than that of the DBFL-IWHR model， and that the arrival time of the maximum flow rate in the downstream section is delayed compared to that of the DBFL-IWHR model. This highlights the importance of using accurate models in predicting the potential impact of dam breaks on downstream areas. In conclusion， the optimization formula proposed in this study provides a more accurate method for estimating the width of the breach in earth-rock dam breaks， and can be used to improve the accuracy of calculations for maximum flow rate. Furthermore， the use of accurate hydrodynamic models， such as the DBFL-IWHR model， is recommended for simulating the downstream flood evolution and predicting the potential impact of dam breaks. These findings may have significant implications for dam safety engineering， emergency response planning， and the protection of people and property downstream of earth-rock dams.

Based on the flood disaster mechanism and flood characteristics of the Minjiang Basin， the hydrological， topographic， hourly precipitation data， statistical yearbook， flood control projects and other data of the Minjiang Basin are collected and sorted out. Starting with the danger of flood risk， this paper selects vulnerability and disaster-bearing and defense ability， 17 evaluation indexes. The AHP analytic hierarchy process and the entropy weight method are used to obtain flood factor weight indicators of the Minjiang Basin， and the spatial differentiation characteristics of flood risk are analyzed in combination with the spatial analysis function of GIS， so as to quickly evaluate the flood risk zoning of the Minjiang Basin. It is conducive to the formulation of macro-flood control and disaster reduction policies and refined flood control response measures. The results show that the results of flood risk zoning in the Minjiang Basin are basically consistent with the flood disasters in recent decades. The distribution of the flood risk in the Minjiang Basin is closely related to its climate， topography， social economy， flood control projects and other factors. The difference of flood risk in the basin is high， and the high risk is concentrated on several counties and cities in Nanping， the upstream region.

The opposite side vertical joint fishway has the characteristics of better adaptation to water level changes， obvious energy dissipation effect and better flow pattern of water. According to the design guidelines， the fish passage in the study area is designed in body shape. In this paper， the effect of different vertical slit positions on the flow structure of the chamber is investigated by numerical simulation， including the hydraulic characteristics of the main flow area， the hydraulic characteristics of the return flow area and the flow velocity distribution of the vertical slit position， and the vertical slit position of the fish passage suitable for the fish in the study area is analyzed. The simulation results show that： the vertical slit position has almost no effect on the maximum flow velocity in the pool chamber of the opposite side vertical slit， and has less effect on the change of the maximum flow velocity along the main flow area. As the center of the vertical slit gradually approaches the center of the pool chamber， the decay of the maximum flow velocity along the main flow area takes the lead in gradually becoming larger and then tends to saturate. Most of the flow velocity in the return area of the upper left part of the main flow area gradually decreases and then increases， and most of the flow velocity in the return area of the lower right part gradually increases. The area ratio of the two sides of the reflux zone gradually decreases. The vertical slit position on the pool room mainstream area flow pattern and the flow velocity distribution of the return area has a significant impact， when 0.23≤l/B≤0.40， the pool room flow pattern is the best； when l/B≥0.37， the mainstream area along the maximum flow decay rate tends to saturate， when 0.37≤l/B≤0.40， the maximum turbulent kinetic energy in the pool room at l/B=0.40 minimum， and the area of the return area on the left and right sides. Therefore， when l/B=0.40， the migratory effect of semi-migratory fish in the study area can be significantly improved. The maximum variation of turbulent energy in the pool is between 0.074 and 0.116 m²/s² when the vertical slit is located at 0.13~0.50 of the width of the pool chamber from the side wall， and the flow pattern in the pool is the best when the vertical slit is located at 0.23~0.40 of the width of the pool chamber， which can significantly improve the migratory effect of semi-migratory fish in the study area. The results of the study clarify the influence of the center position of the vertical joints on the water flow structure of the pool chamber and provide a reference for the subsequent design and research work of other related fish passage projects.

Wading projects are likely to bring about changes of the original hydrodynamic conditions of the river， and this may further affect the flood discharge capacity of the river course. Thus， it is of great significance to study the flood risk of the river course with or without the wading projects， so that we can well maintain the project， regulate river course and ensure regional flood control security. Based on the random simulation of four uncertain factors， namely peak flood discharge， initial water level， river course roughness and dike elevation， this paper analyzed the stress of aqueduct under flood action， and then calculated the water surface line of the river. Combined with theforce conditions and water surface line calculation results， the conventional Monte Carlo method and the Monte Carlo method based on Latin hypercube sampling were both used to calculate the flood risk of river course with or without an aqueduct. The results show that： ① When the water level in Gangqian Aqueduct is 0.5， 1.0， 1.5 and 2.0 m， the flood discharge capacity of Qingfeng Mountain stream， compared with its designed discharge of 1 200 m3/s， respectively decreases by 36.68%， 27.87%， 19.00% and 10.05%. ② In the case of having no aqueduct in its river course， the flood risk of Qingfeng Mountain stream course is 0.007. In the case of having Gangqian Aqueduct in its river course， when the water level in the aqueduct was 0.5， 1.0， 1.5 and 2.0 m respectively， the flood risk of Qingfeng Mountain stream course is 0.34， 0.045， 0.016， 0.012 in turn. ③ Keep the water level in Gangqian Aqueduct at the highest value within the safe range. When the discharge of Qingfeng Mountain stream exceeds 1 600 m3/s， the flood risk of its river course still rises significantly with the increase in the flood flow. Therefore， in this case， Gangqian Aqueduct would have to be scrapped to ensure the flood discharge capacity of Qingfeng Mountain stream. ④ Both the conventional Monte Carlo method and the Monte Carlo method based on Latin Hypercube Sampling are suitable for assessing the influence of aqueduct on flood risk of river course， and the latter has better convergence. In summary， building adueducts in river courses would have a negative impact on the river courses’ flood discharge capacity. It results in the flood discharge capacity of the river course being lower than the designed discharge， and further， led to the flood risk of river course increasing. To a certain extent， raising water level in the aqueduct can reduce the flood risk of river course.

The fairness of water use is one of the key factors to be considered in the balanced allocation of water resources. Aiming at the problem that the fairness of water use in the basin is not considered enough in the different industries， an evaluation method based on multi-factor Gini coefficient in different industries is proposed. The Gini coefficient between industry water consumption and industry scale is used to represent industry water fairness. The comprehensive Gini coefficient of water use in the basin is calculated based on the proportion of water consumption in each industry to represent the fairness of water use in the basin. Taking the Yellow River Basin as an example， this paper calculates the Gini coefficient and analyzes the variation of the fairness of water use of different industries in nine provinces of the Yellow River Basin from 1980 to 2020. Take 1995 and 2005 before and after the integrated water regulation of the Yellow River as examples， the impact of integrated water regulation on the fairness of water use in the basin was compared and analyzed. The results show that over the past 40 years， the fairness of water use in domestic， industry， urban public， and agriculture were “highly fair”， “relatively fair”， from “highly fair” to “relatively fair”， and from “relatively fair” to “highly fair”， respectively. The proportion of agricultural water use exceeds 70%， and the Gini coefficient of watershed water use is mainly affected by agricultural water use， the comprehensive Gini coefficient of economic and social water use in the basin is 0.16~0.25 from 1980 to 2020， which is in a downward trend， indicating that the fairness of economic and social water use in the basin has gradually improved， changing from “relatively fairness” to “highly fairness”. The fairness of water use for domestic and agriculture is gradually improved， and the fairness of public water use in industry， especially in urban areas， has decreased significantly. This is mainly because the differences in water use quotas for domestic and agriculture between 9 provinces in the basin have decreased， while the differences in water use quotas for the tertiary industry have increased. The integrated water regulation of the Yellow River has effectively controlled the total water use in the basin， promoted the improvement of agricultural water use efficiency and the reduction of water quota differences between provinces， and improved the fairness of agricultural water use and water use in the entire basin.

Due to climate change and human activities， the runoff characteristics of the upper Yangtze River have changed significantly in recent years， bringing many challenges to the development and utilization of water resources in the upper Yangtze River Basin and the functions of national strategic freshwater resource reservoirs such as the Three Gorges and the upstream reservoir group. Attribution analysis of runoff changes is of great importance to the development and utilization of water resources in the basin. Based on the observed runoff data from 1951 to 2013， statistical methods such as Mann-Kendall test， Spearman test and Pettitt test are used to diagnose the variation patterns of the Three Gorges inflow runoff. Based on the meteorological and land use data of the same period， the causes of the variation of the Three Gorges inflow runoff are further quantitatively analyzed by using the climate elasticity method， the water-energy balance equation and the SWAT. The results show that： ① the inflow runoff of the Three Gorges was significantly changed around 1993， before 1993 the runoff was relatively natural and less affected by climate change and human activities， and after 1993 the runoff changed and was more affected. ② During the study period， the inflow runoff from the Three Gorges decreased significantly， at a rate of 8.8 mm/10 a. Large-scale human activities in the upper Yangtze River were the main cause of the decrease in inflow runoff into the Three Gorges， while the decrease in precipitation and the increase in temperature were important causes. ③ The attribution results of the climate elasticity approach are consistent with the SWAT-based method， while the water-energy balance approach underestimates the impact of human activities on runoff. ④ SWAT takes into account the spatial and temporal changes in land use， can better describe the causes of runoff changes than the traditional “two-stage” method. These results are important to guiding the comprehensive utilization of water resources in the Three Gorges Reservoir and the rational development of water resources in the upper Yangtze River.

The Yangtze River to Huai River Diversion Project spans two major river basins， the Yangtze River and the Huai River. It is a major cross basin water transfer project that alleviates local water resource shortages， improves project benefits， and supplies water to the Henan section. In the case of unknown water supply and demand sides in the Yangtze River to Huaihe River Diversion Project， the water volume at the head of the channel is reversely optimized by using the regulation and storage capacity of Caizi Lake， Chaohu Lake， and Wabu Lake， and the water intake process at the diversion outlet is forward optimized. A simulation model and a bidirectional optimization model are layered and coupled， and a medium and long-term water volume scheduling model for the Yangtze River to Huaihe River Diversion Project is constructed based on the principle of water balance. A typical annual scheduling scenario set is constructed based on the water inflow situation and water demand. Based on the water inflow forecast results of various lakes in different level years， the water demand process at the entrance and engineering constraints， a differential evolution algorithm with adaptive parameter correction mechanism and a stepwise optimization algorithm are used to solve the problem， in order to formulate the annual water volume scheduling plan for the Yangtze River to Huaihe River Diversion Project. This paper takes the 2030 planning level year of abundant water as an example to compare and analyze the layered coupling water scheduling model and the conventional optimization scheduling model. Due to the layered coupling water scheduling model optimizing the lake regulation and storage process and constraining the lake water level， the model has better effects in terms of river diversion water volume， water shortage in water receiving areas， and lake utilization. The results show that on the basis of meeting the water use plan of the diversion gate， the model reduces the lake’s abandoned water volume， and the deviation value of the lake’s end water level is small. The daily water level variation is guaranteed to be within 0.1 m， and the lake is in a high water level operation state. The annual water volume scheduling plan obtained from this model can effectively utilize local water resources， improve water resource utilization efficiency， and provide technical support for the operation scheduling and scheduling plan preparation of the Yangtze River Diversion to Huaihe River Project.

Based on the precipitation， runoff and sediment data from the hydrological station， cluster analysis and sediment content-flow （SSC-Q） hysteresis curve are used to study the runoff and sand transport characteristics of different types of flood events in the Mihe River Basin of the northern earth and rock mountainous areas from the event scale， and reveal the relationship between various floods and sediments， the contribution of sand transport and the influence mechanism of soil and water conservation measures. The results show that ① The 261 flood events in the Mihe River Basin from 1951 to 2021 could be divided into four categories： small， medium， large and extra-large， and the flood hysteresis curve type was mainly figure-8. With the increase in flood magnitude， the flood duration and runoff sand transport of flood events showed an increasing trend， the runoff， and sediment variability increased， and the proportion of the composite hysteresis curve gradually increased. ② The frequency of large-scale and extra-large flood events was the lowest， but the contribution rate of sand transport was as high as 86.9%， which was the main type of flood in the northern earth-rock mountainous area， and dominated the soil erosion disaster in the Mihe River Basin， which needs to be paid attention to in the governance of the river basin. ③ Water and soil conservation measures and human activities have a greater impact on medium and small flood events， and the variability of the water-sediment relationship exceeds 10%. However， the impact on large-scale flood events is relatively small， and the variability of water-sediment relationship is only 1.2%. Through the rational allocation of water and soil conservation measures in the river basin， the relationship between water and sediment in local small and medium-sized flood events can be adjusted， so as to achieve the purpose of flood storage and sediment control. At the same time， it is urgent to continue to strengthen soil erosion and flood prevention and control measures for exceptionally heavy rainfall to avoid serious damage to the ecological environment of the northern earthy mountainous areas. The research findings serve as a theoretical and practical basis for the development of soil and water conservation in the region and the response to exceptionally heavy rainstorms and flood events.

Climate change and human activities are important causes of runoff changes in watersheds. The Budyko hydrothermal coupled equilibrium equation is a common tool for runoff change analysis， because it takes into account certain physical causes on the one hand， and the parameters of the equation are simple on the other hand， so it has been widely used in runoff change attribution for a long time. However， the current research and application of Budyko’s formula for time-varying forms still need to be strengthened. Therefore， this paper first analyzes the trend and abrupt change of annual runoff in the study area by Mann-Kendall test and abrupt change test， and then constructs the time-varying Budyko formula based on the principle of hydrothermal coupling equilibrium， including linear， quadratic polynomial and physical mechanism， and uses Nash efficiency coefficient as the evaluation index to verify the most suitable. Finally， the contribution of precipitation， potential evapotranspiration and human activities to the runoff change is calculated， and the attribution analysis of the runoff change in the Liudong River basin is carried out. The results of this study show that the runoff of the river basin has been decreasing in recent years with the impact of climate change， with a significant change in 1997. A comparison of the sensitivity of precipitation， potential evapotranspiration and human activities to runoff show that the decrease in precipitation is the dominant factor in the decrease in runoff， with a contribution of 49%. Meanwhile， with the development of human economy and society and the construction of large water conservancy facilities， the influence of human activities on runoff changes in the basin is gradually emerging， with a contribution rate of about 26%.

With the development of society and economy， urbanization level continues to increase， which has changed the characteristics of the underlying surface. The water cycle has been seriously affected， leading to a series of urban water problems such as waterlogging and water environment pollution. Low Impact Development （LID） can alleviate the amplification effect of rainfall and flood caused by urbanization， and a key issue in the design of LID measures is to explore the impact of underlying surface changes on flood processes. This paper compares urban rainwater flood models and selects the Win-TR55 model， which is a small watershed design flood model. The core of this model is the SCS-CN runoff curve model， which is characterized by simple calculation process， less required parameters， and comprehensive consideration of the relationship between changes in basin precipitation， underlying surface type， and runoff. Based on the above model， the underlying surface of the Jiulong Ecological Park in Wuhan is analyzed under current， traditional， and low impact development conditions. The design flood process is simulated under different return periods， and the hydrological effects of low impact development are evaluated based on changes in the flood volume， peak， and inundation range. The results show that ① under the three development modes， the CN value is the highest under traditional development and the CN value is the lowest under low impact development conditions. This indicates that in the low impact development mode， the type of underlying surface has been changed， the storage capacity has been increased， and the corresponding CN value has decreased， resulting in a decrease in flow rate. ② Under the low impact development conditions， the reduction rates of flood volume for once every year， once every five years， once every ten years， and once every fifty years can reach 96.74%， 81.58%， 73.46%， and 61.13%， and the reduction rates for flood peaks can reach 94.14%， 70.63%， 60.64%， and 45.42%. ③ The reduction rates for the design inundation range can reach 74.35%， 63.60%， 51.14%， and 6.83%. From the simulation results， it can be seen that as the rainfall intensity increases， the flood control effect of low impact development gradually weakens. The study also found that as the rainfall intensity increases， the control effect of low impact development on rainwater and flood gradually weakens. The research findings can provide a hydrological basis for the design of regional LID facilities.

In the process of applying the hydrological model to hydrological forecasting， there are many simplifications and assumptions in the structure of the basin hydrological model， which will bring errors to the hydrological forecasting results. Therefore， error correction technology is needed to improve the accuracy of the hydrological model in real-time forecasting. The system differential response method uses the system response function to modify the forecast results by modifying the inputs， state variables and parameters of the hydrological model. This method has a solid theoretical foundation， simple structure， and the advantages of not losing the forecast period. It has been widely used in multiple watershed hydrological model with good results. VIC model is a large-scale distributed hydrological model， which divides the watershed into multiple grids of the same size to simulate runoff generation and concentration results within the grid. This paper takes the Jianyang Basin of the Minjiang River as the research area， constructs a basin VIC model for runoff simulation， applies the system differential response error correction method to the VIC model， corrects the forecast results by modifying the rainfall in the model input， and compares and analyzes it with the traditional autoregressive model error correction method （AR model）. The results show that the system differential response method has a good correction effect in the VIC model， with the Nash efficiency coefficient increasing from 0.752 to 0.895 before correction， and the relative error of runoff decreasing from 7.89% to 5.71%. The Nash efficiency coefficient of the AR model correction result is 0.807， and the relative error of runoff is 6.77%. The results of these two correction methods indicate that the system differential response method is superior to the AR model error correction method. The system differential response correction method has good applicability in the VIC model， which can significantly improve the accuracy of daily runoff simulation in the basin and can be applied to future hydrological forecasting processes.

In order to analyze the impact of rainstorm design on mountain torrent disasters in small watersheds in mountainous areas， this paper uses a spatio-temporal variable source mixed runoff generation model， taking Guankou， and Hanwangchang in Sichuan Province as the research area， the response rules of descending water in high vegetation cover basins to different reproduction periods and rainstorm type conditions of different designs are analyzed， and the peak flow， peak present time and peak lag time of the river basin under different rain types and recurrence period conditions are compared and analyzed. The research findings show that the spatio-temporal variable source mixed runoff generation model is suitable for the simulation of hydrological processes with good simulation accuracy in mountainous areas with high vegetation coverage. The latter rain patterns in the Guankou and Hanwangchang basins have more flood peaks than those formed under the front and middle conditions under the same recurrent period， but the front rain patterns produce more floods than middle and rear rain patterns. Under the conditions of different rainfall patterns， with the increase in return period， the peak discharge of the Guankou and Hanwangchang drainage basins shows an increasing trend. The forest and grass vegetation coverage rate is Hangwangchang>Guankou watershed， and the peak emergence time of the Guankou is earlier than that of the Hangwangchang watershed under the design rainstorm conditions of different return periods， the vegetation coverage of forest and grass can regulate the runoff process of flood to a certain extent. The lag time between the occurrence time of the flood peak and the occurrence time of rainstorm peak in the Guankou watershed and the Hanwangchang watershed is forward type>middle type>rear type.Revealing the quantitative law of the high vegetation covered watershed in the southwest mountain area for the design of rainstorm patterns in different return periods has a guiding significance in analyzing the formation process of rainstorm and flood in the high vegetation coverage basin of the southwest mountain area， and improving the flood forecasting accuracy and flood control and disaster reduction capability of the basin.

The properties of expansive soil include water expansion， dehydration shrinkage， and cracking， with soil fissure having a significant impact on rainfall infiltration and runoff generation. This paper uses chestnut soil， which is frequently found in the Qinghai Lake Basin， as expansive soil， and performs an indoor rainfall infiltration runoff generation experiment with varying initial soil moisture contents for the soil shrinkage process. The goal of the experiment is to investigate the influence of the law of desiccation cracks of expansive soil on infiltration runoff generation， the effects of soil fissure and shrinkage on runoff intensity， cumulative infiltration rate， and moisture content under various initial moisture content conditions. The findings indicate that when the initial water content of the soil declined， soil shrinkage and fissure development increases， and all of the infiltration rates—initial infiltration amount， cumulative infiltration amount， initial infiltration rate， average infiltration rate， and stable infiltration rate—increase as well. The accumulated infiltration amount， fissure linear density， and soil surface fissure rate all exhibit strong correlations with correlation coefficients above 0.85. The more surface fissure area rate and linear density there are， the greater the impact of the fissure on infiltration. The longer the lag time between soil runoff generation and runoff generation from other sources， the smaller the runoff generation， and the longer it takes for the runoff intensity to stabilize， all are related to the degree of soil shrinkage and fissure development. Soil shrinkage and fissure are advantageous for the development of preferred flow. The capacity of the soil to supply water to deep soil increases with the degree of fissure formation. In order to complement the rainfall infiltration runoff generation law of expansive soil， the experiment investigates the influence of expansive soil shrinkage and fissure on infiltration runoff generation.

In order to explore the influence of jet pipe structure on the flow field of annular jet pump， three-dimensional numerical simulation of annular jet pump under right-angle turn and arc turn was carried out， and the straight section of annular nozzle outlet was calculated and analyzed. The results show that the flow field is unevenly distributed around the nozzle， throat and diffuser in the jet pipe with right-angle turn. The annular nozzle forms a uniform jet in the jet pipe with arc turn， which is conducive to the uniform and symmetrical mixing and energy transfer between the primary flow and the secondary flow， so that the pressure ratio and efficiency are improved under each flow ratio. The performance of the annular jet pump can be improved by setting （0.5~1） times the outlet width of the straight section at annular nozzle outlet， and the efficiency can increase by 1% at the middle and low flow ratio. At the same time， the straight section helps to stabilize the pressure at the nozzle outlet and to reduce the range of the recirculation area near the inlet of the throat and the extent of the pressure drop. The research findings serve as a support for the analysis of the overall flow field of annular jet pump and the design of jet pipe structure.

Mechanism of drought disaster in karst areas is complex， and the technical specification method of drought disaster risk census does not consider the drought disaster mechanism comprehensively， resulting in insufficient coordination between the drought disaster risk zoning results with the county-level administrative regions as the assessment unit and the historical drought disaster results， which has become a difficult problem in the drought disaster risk census in Guizhou Province. As the basic theory of drought disaster risk zoning， the natural disaster risk theory constructs a drought disaster risk zoning index system with karst characteristics based on the natural disaster risk theory to conduct drought disaster risk research， which can provide a basis for drought disaster risk zoning. Taking Zunyi City as an example and based on risk theory of natural disasters， the representative indicators of drought disaster risk in karst area are analyzed and selected， a drought risk zoning model is established， the weight of drought disaster index system is determined by coupled weighting method of expert scoring method and entropy weight， and quantile classification using ArcGIS， and drought disaster risk zoning research is carried out. ①The results show that surface water drought hazard index， terrain composite index， cultivated area and proportion of drylands， rural centralized water supply rate and effective farmland irrigation ratio are the main influencing factors of the drought hazard， environmental vulnerability， exposure of the values at risk， and capacity to prevent or mitigate drought disaster， respectively. ②The drought disaster risk level of all counties and districts in Zunyi City is mainly medium risk or below， accounting for 64.3%， and the cumulative proportion of medium-high risk areas and high-risk areas are 35.7%. ③The overall drought disaster risk shows a pattern of high distribution in the northeast and low in the southwest and regional distribution characteristics. High-risk areas are distributed in the northeast， medium-high risk areas are distributed in the north， medium-risk areas are distributed in the east， medium-low risk areas are distributed in the south， and low-risk areas are mainly distributed in the middle. Through a comparative analysis with the national drought relief program and other related data， the rationality of the zoning results is verified， which can provide a scientific basis for the local drought disaster prevention work.

As the lined channels in Northwest China are subject to frost heave soil extrusion damage in winter， coupled with the easy sinking of wet-submerged loess in water， the frost damage of lined channels with wet-submerged loess as foundation is complicated. To address this problem， this paper takes the East First Trunk Canal before and after the renovation of Ningxia Guhai Irrigation District as a prototype， and establishes a simplified three-phase coupled mathematical model of the channel by analyzing the deterioration law of the channel before and after the renovation by frost damage and the plastic damage structure of concrete material. Considering the mechanical properties of wet-submerged loess and the contact behavior between canal base soil and liner plate， the numerical model of thermal-force coupling of lined channels before and after renovation is constructed by ABAQUS software based on the measured data， and the specific situation and deformation law of frost swelling are simulated and analyzed in comparison. By comparing the three physical fields simulated by the two coupled models， the results show that the frost damage of the modified rigid-flexible lined channels has been substantially improved and the stress concentration has been avoided to a certain extent； comparing the field data before modification with the research results， the accuracy and feasibility of the numerical coupled model are verified， and the three physical fields of heat-force-displacement simulated can better reflect the frost swelling mechanism of the actual lined channels， which serves as a reference for the management and modification design of the frost damage of the irrigation channels.

Shimen Reservoir Irrigation Area is a large-sized irrigation area in Hanzhong Plains. It is of great significance to study the water use efficiency of typical irrigated areas through water balance test to realize the mode， experience and practice of the strictest water resource management system. By conducting water balance tests of point， line and plane in irrigated area， and the quantitative relationship between water distribution and water delivery， water facilities operation， total water consumption and water consumption in each region is obtained. Based on the test data， this paper calculates the utilization efficiency of irrigation water， analyzes the water use efficiency of the irrigated area by combining the geomorphology， crop distribution， channel lining and other factors， and studies its improvement measurement. The results indicate that in hilly areas， rice planting and water leakage from low level channels are the major factors of water loss in irrigated areas， which provide important basis for water use efficiency and water-saving scheme in irrigated areas.

Long-distance water transmission project lines， complex environment along the line， in the daily operation of water transmission projects， engineering safety inspection is an important way to maintain production safety. A large amount of inspection text data is generated in the engineering inspection. In the traditional production management process， inspection text relies on managers to manually classify according to the severity of the problem， which is inefficient and prone to subjective problem classification errors， and is not sufficient for good management of long lines and complex environment along the water transmission project. To address this problem， this paper proposes a hybrid deep learning model combining Bi-directional Long Short-Term Memory （BERT） and BERT neural network to classify inspection text intelligently by using BERT as the input layer to transform inspection text into feature vectors， and then inputting the results to BiLSTM.The model uses BERT as the input layer to transform inspection text into feature vectors， and then feeds the results into BiLSTM model to mine text features and realize intelligent classification of inspection text. Compared with the mainstream deep learning models TextCNN， BERT and BiLSTM， the accuracy， recall and F1 values of the model reach 92.30%， 92.32% and 92.30% respectively， and the model outperforms other deep learning models.

Based on the transport model of pore gas in unsaturated soil under the membrane， the solution of the transport model of pore gas under membrane is obtained by means of the solution method of heat conduction model. The rationality of the numerical simulation method is verified by using the theoretical formula method of pore pressure calculation under the membrane. The pore pressure in the unsaturated soil under the membrane is simulated and calculated when groundwater levels different rise of heights， and the pore pressure distribution law is analyzed. The influence of exhaust ditch spacing on pore pressure is discussed. The research findings show that in plain reservoirs with geomembrane reservoir basin seepage control， when the infiltrated water is in contact with groundwater， a space of closed gas will be formed， and the rise of groundwater level will cause geomembrane air expansion. The rising groundwater level’s magnitude affects the air pressure distribution in the soil under the geomembrane membrane， and the air pressure under the membrane grows non-linearly with the rising groundwater level. When the rise of the groundwater level causes the increase in the pressure under the membrane， eight kinds of exhaust ditches with different spacing of 30~175 m are set， and the pressure under the membrane is compared and analyzed. It is found that the exhaust ditches can effectively slow down the pressure increase during the groundwater rising process and accelerate the gas migration under the membrane. At the same time， the distance between exhaust ditches affects the exhaust effect. The greater the distance between exhaust ditches， the smaller the drop in air pressure and the more unfavorable the dissipation of air pressure. For typical examples， exhaust ditches with 75 m spacing are recommended.

By solving the problems such as the shortage of drainage power in inland rivers and the difficulty of construction land， the integrated gate pump with compact structure and small floor area has received much attention. Among them， the integrated gate pump with larger diameter has a short application time and few examples in China. This paper takes the Salt River Pump Gate Project as the background， uses the three-dimensional parametric calculation model， carries on the design optimization analysis of the door blade thickness， the plate thickness and other parameters， and the reinforcement analysis of the weak parts of the wall pipe and web. At the same time， the key problems such as vibration and anticorrosion of the gate pump are analyzed and demonstrated. The results show that the thickness of the door blade should not increase too much， and the panel and web structure with large separation should be properly strengthened at the same time to control the resonance frequency domain. When the ratio of gate width to height is less than 0.6 and the ratio of the pump outer diameter to gate width is close to 0.5， the plate thickness combination in the range of 12~16 mm should be used. Transverse， longitudinal and diagonal ribs should be considered at the same time for wall pipe reinforcement. Through a dynamic simulation analysis， the design of Salt River Pump Gate can avoid the resonance of the integrated pump gate， and has a certain safety margin.

In order to study the effect of different groundwater depth on soil water and salt transport and its changing characteristics in takyric solonetz soil， the salt content， water content and salinity of the soil under six groundwater depths of 0.8，1.0，1.2，1.5，1.8 and 2.0 m are monitored in takyric solonetz land at the farmland of Xidatan in Ningxia， China. The results show that there is an exponential relationship between soil total salt and groundwater depth， and there is a significant linear positive correlation between soil total salt and groundwater salinity. The change of total salinity and alkalinity is 0.8 m >1.0 m >1.5m >1.8m >2.0 m； 1.5 m ground water depth is the turning point of soil water and salt change. The total salt and water content of each soil layer are higher at 0.8~1.2 m ground water depth. The variation of soil water and salt is the most serious in the soil with the groundwater depth of 1.5~1.8 m. Oil sunflower grows in 1.5~2.0 m depth of ground water suitably. The emergence rate， survival rate， plant height， stem diameter， diameter and yield of oil sunflower in 0.8， 1.0 and 1.2 m of groundwater table are significantly lower than those in 1.5， 1.8 and 2.0 m of groundwater table. There are no significant differences in soil water content， total salinity and alkalinity， emergence rate， survival rate， plant height， stem diameter， disc diameter and yield of oil sunflower at depths of 1.5， 1.8 and 2.0 m. These results will provide a technical support for salt-water management of the takyric solonetz farmlands， and have an important scientific value for environmental protection and agricultural irrigation development in arid areas.

In order to solve the problem of large-scale backflow in side-inlet forebay of Shiqiao Pumping Station in Yangzhou City， Jiangsu Province， Shiqiao Pumping Station intake structure is taken as the research object based on Reynolds time-averaged equation and RNG k-ε model， CFD software is used for numerical calculation of side-inlet forebay and intake sump. The flow characteristics of forebay and intake sump are analyzed under different rectification measures. Several rectification measures are proposed and the effect of flow pattern control is quantitatively analyzed. The result shows that the flow pattern of 2# and 6# intake sump is comparatively disordered without rectification measures， as the streamline is distributed unevenly. Through an analysis of three rectification measures， the streamline distribution of the intake sump is uniform and the flow velocity distribution is reasonable when the bottom ridge is added to the forebay. Axial velocity distribution uniformity of inlet characteristic section in intake sump is increased by about 30% on average in each pump unit， indicating a significant rectification effect. The research findings serve as a reference for the flow pattern improvement of similar pumping station projects.

Through the complex function method， an analytical method for solving the circular hydraulic tunnel with double lining is proposed. The established model is based on the interaction between the surrounding rock and the primary lining， the primary lining and the secondary lining （full contact）， taking internal water pressure and the support delay into account. Based on the preset boundary conditions， the equations for solving the coefficients of the relevant analytic functions can be established， and then the obtained analytical function can be used， the stress components of any point in the surrounding rock， the primary lining and the secondary lining can be solved. By comparing the numerical solution， it is found that the analytical method proposed is correct and effective. At last， the parameters are analyzed from three aspects of controlling the water pressure in the hydraulic tunnel， exchanging the elastic modulus of linings and controlling the thickness of linings， and the factors and results affecting the stress distribution of lining are discussed. The load transfer mechanism and law of the double-lined hydraulic tunnel are revealed， which provides a theoretical basis for the preliminary design and construction of the lining protection project.

In the concrete pouring of the high arch dam， multiple cable cranes usually pour multiple pouring blocks based on strips. So the key to improving construction efficiency is to optimize cable cranes to the coordination of pouring blocks strips. The difference of transportation distance and strip area leads to different pouring efficiency of each cable crane， and simple equal surface of the pouring block hardly guarantees the strip collaborative pouring rise， then the pouring efficiency of the cable crane group is affected. In order to solve the above problems， this paper establishes an intelligent configuration model of cable crane group， which takes into account the pouring cycle time and load balance. Firstly， the pouring strip is divided for the area where the coverage of each cable crane overlaps with the pouring block and the configuration of cable crane group and pouring blocks is transformed into a combination optimization problem of the cable crane group and the strips. Subsequently， a “micro-matching” model which bridges the cable machine and multiple strips is proposed. The many-to-many relationship between cable cranes and pouring blocks is transformed into a one-to-one matching relationship between the cable crane and the micro strip， and the “micro-matching” integral expression of the pouring configuration optimization is established. Finally， the optimal configuration scheme of the cable crane group is obtained with the optimization objectives of cycle time and load balancing， and the coordinated rise of pouring strips is realized. The pouring configuration example of Baihetan arch dam shows that the pouring cycle time and lifting load of the cable crane is basically balanced. The average deviation of the upper cable crane pouring strength is -6.8%， and the average deviation of the lower cable crane pouring strength is 5.1%. This method has good adaptability to the change of the number of cable crane and pouring block， and has certain intelligent configuration ability.

In this paper， the influence on performance of radial straight blade hydraulic turbine is studied with radial meridional flow channel and mixed-flow meridional flow channel. Firstly， the theoretical models are suggested for radial straight blade hydraulic turbine. Secondly， runners are designed based on two different types of meridional flow channels. Finally， the numerical simulation is carried out for different schemes， while the performance and flow field are analyzed and compared. Results show that the two different schemes adapt to ultra-small discharge and head with large fluctuation. Moreover， the best numerical predicted efficiency is 81.4% for radial straight blade hydraulic turbine with the mixed-flow meridional flow channel， which is 1.8% more than the radial meridional flow channel. Meanwhile， with a larger conveyance capacity， the optimal efficiency is verified for the hydraulic turbine with mixed-flow meridional channel， and it can meet the needs of hydraulic energy recovery with ultra-small discharge. The conclusions serve as a reference in the design of hydraulic energy recovery turbine.

Aiming at the spillway tunnel radial gate structure of Baihetan Hydropower Station with large width and height ratio， this paper uses the first horizontal three-arm hidden radial gate type in China. The multi-factor analysis of key design parameters， such as the placement of the three arms， the unit stiffness ratio of the main beam to the arm， and the finite element numerical calculation verification under multiple load conditions are adopted. The optimal arm length and unit stiffness ratio of the radial gate of Baihetan spillway tunnel are determined. Furthermore， the force distribution of the horizontal three-arm radial gate is optimized， which effectively guarantees the bearing safety of the civil structure under the huge discharge. The results show that the optimal arm length and unit stiffness ratio in Baihetan are 2.5 m and 10.7 based on the criteria for determining the length and unit stiffness ratio of the three lateral arms on the basis of the sensitivity analysis of multi-factor parameters. The main calculated stress of the optimized radial gate structure is less than 145 MPa， and the maximum calculated combined displacement is less than 15 mm， both of which meet the requirements of strength and stiffness. The key technology of horizontal three-arm radial gate is researched and established， which can provide technical support for the safe operation of spillway tunnel with super width-to-height ratio orifice and super large discharge volume.

Intensive land use is one of the core issues of land science， while the research on intensive land use in the special area of reservoir resettlement town is relatively less. Through the construction of PSR model， the intensive use of land in the resettlement area of Z market town is evaluated. The results show that the land use in the resettlement area of Z Town is not intensive， which belongs to the extensive land use mode， and the phenomenon of inefficient land use is relatively serious. Further， by using the obstacle factor analysis method， four main obstacle factors affecting the land intensity in the resettlement area of Z Market Town are found： the turnover of shops per unit area， the carrying capacity of land population， the total investment in land construction and the per capita income of reservoir resettlement. For the resettlement area of reservoir resettlement market town， the following three suggestions are put forward to improve the intensive use of land： ① increasing investment attraction and the turnover per unit area of reservoir resettlement shops； ② improving the infrastructure construction in the resettlement area and enhance the land population bearing capacity； ③ The government should increase the support of post support funds to increase the average land investment.

Deep beam specimens are introduced into the tensile strength test of compacted clay， and the evolution of the cracking resistance characteristics under different water content and dry density conditions， including load-deflection curves， tensile strength and energy parameters， are analyzed. The results show that： the damage mode of compacted clay is closely related to water content and is not affected by dry density； water content and dry density have significant effects on the tensile strength of compacted clay specimens， and the tensile strength increases with increasing water content and then decreases， and increases linearly with increasing dry density； the fracture dissipation energy increases with increasing water content and then decreases， and the crack ductility dissipation energy is more at high water content. The elastic reserve energy and crack ductility energy increase gradually with the increase in dry density of the specimen， and the elastic reserve energy increases more.

In order to deeply explore the evolutionary process and characteristics of social stability risk of reservoir resettlement， and improve the scientific nature of government management decisions， Firstly， the risk transmission chain of reservoir resettlement social stability and the risk indicator system including 4 primary indicators and 15 secondary indicators of economy， government management， living environment and social interaction are established from the perspective of risk perception. Then， based on the established risk transmission chain， the causal relationship between risk factors is qualitatively analyzed. Finally， the system dynamics （SD） evolution model of reservoir resettlement social stability risk is constructed， and the ANP is used to determine the basic weight of each index， and the risk evolution simulation is carried out with an example. The results show that with the investment of funds and the implementation of the government’s pacification measures， the risk value of social stability shows a general trend of rapid increase first， then a rapid decrease， and finally tends to be flat. Its specific characteristics are as follows： the risk amount in the first to third years accumulates rapidly， and rises to the peak in a short time. The risk value in the third to sixth years decreases rapidly due to the intervention of various policies， and the risk value gradually tends to be flat in the sixth year， and keep it descending slowly.

With the construction and operation of cascade reservoirs in large basins， the research on short-term optimal operation of cascade reservoirs has received more and more attention. However， the optimization problem contains many variables and complex constraints， and its model modeling and solution are more and more difficult with the expansion of the reservoir group. Although traditional optimization methods or intelligent optimization methods can obtain optimal solutions that meet relevant objectives and constraints， the results under the optimization algorithm are often too biased towards the target value， resulting in large volatility and randomness， which is difficult to meet the actual scheduling needs. In view of this， this paper proposes the construction technology of power station output scenario based on the historical dispatching results， cluster analysis and other data mining methods， considering the scheduling period， business type， scheduling period length， scheduling objects and other scenario elements， and forms the output scenario set by mining typical output scenarios based on a long series of historical operation data. On this basis， a short-term optimal operation method of cascade reservoirs based on the output scenario set is proposed. Through the case study of Shaxi cascade reservoirs， it is found that compared with the traditional optimal operation method， the scenario method proposed in this paper can not only obtain the output process that meets the actual operation requirements， but also shorten the calculation time relatively， which verifies the feasibility and practicality of this method. The research results have a good reference significance for short-term optimization scheduling of cascade reservoirs in other basins.

The four hydropower stations of Wudongde， Baihetan， Xiluodu， and Xiangjiaba in the lower reaches of Jinsha River are important components of the Yangtze River flood control system. The operation of the hydropower stations in Wudongde and Baihetan not only greatly improves the flexibility of flood control scheduling， but also gives full play to the comprehensive benefits of the four reservoirs. In this study， the optimal dispatching model of cascade hydropower stations is applied to the Wudongde， Baihetan， Xiluodu and Xiangjiaba stations in the lower reaches of Jinsha River. A hybrid algorithm based on nonlinear programming and improved progressive optimality algorithm is used to solve this model. Based on long series historical inflow data， the optimal dispatching strategy of cascade hydropower stations during flood and impoundment periods is analyzed. The results show that the cascade hydropower stations have different strategies of reservoir capacity utilization under different inflow conditions. If the inflow is dry in the whole period， the flood control capacity of Wudongde， Xiluodu and Xiangjiaba will be used first before Baihetan. If the inflow is dry in the early period and rich in the later， the flood control capacity of Wudongde and Xiluodu will be used first before Baihetan and Xiangjiaba. If the inflow is rich in the early period and dry in the later， the flood control capacity of Wudongde， Baihetan， Xiluodu will be used first before Xiangjiaba. If the inflow is rich in the whole period， the flood control capacity of Wudongde and Baihetan will be used first before Xiluodu and Xiangjiaba. The utilization of flood control capacity of the four reservoirs presents different distribution proportions with inflow characteristics. There is a significant linear correlation between the proportion of water volume and that of cascade flood control capacity utilization， and the monthly release of cascade flood control capacity can be estimated by linear fitting function. The research findings serve as a reference for the dispatching of cascade hydropower stations in the lower reaches of Jinsha River.

Gently inclined weak interlayer is one of important factors affecting anti-sliding stability of dam foundation. The densely developed gently inclined weak interlayer makes the stability of dam foundation more complicated. It is of great significance to engineering safety and treatment of dam foundation under complex foundation conditions to study the instability mode of dam foundation under the influence of dense gently inclined weak interlayer. In this paper， two typical dam sections of Datengxia Sluice Dam are studied by using geomechanical model and numerical simulation method respectively. In this study， the adverse effects of dense gently inclined weak interlayer and faults are taken into full consideration， and the failure process and form of the dam foundation are obtained. The stability safety factor of the comprehensive method is determined to be K_SC =3.30~4.18. It is revealed that the failure mode of the dam foundation of Datengxia Sluice Gate is the compression yield failure of shallow bedrock， and the gently inclined weak interlayer does not form a slip channel. No deep sliding failure occurs in the dam foundation. The results show that the dam heel area and the dam toe area are the weak parts of the project， which needs to be strengthened by engineering measures. The research results provide an important basis for the design of engineering reinforcement scheme and a reference for similar engineering dam foundation stability researches.