Under the background of global climate change and the increasing impact of human activities， drought has become a key factor restricting the sustainable development of China’s social economy， seriously threatening the national food security， water security and ecological security. This paper is based on the global land reanalysis product of China Meteorological Administration. It extracts the monthly soil moisture data of Guizhou province and calculates the standardized soil moisture index. The applicability of the index to agricultural drought identification and the accuracy of historical typical drought process simulation are evaluated. The long-term evolution trend of dry and wet is analyzed， and the most likely time of drought is calculated. The results show that the monthly standardized soil moisture index is consistent with the record of China Flood and drought Disaster bulletin， and the drought duration is accurately described and the drought intensity is reasonable. The monthly standardized soil moisture index can not only accurately simulate the whole process of drought occurrence， development and elimination， but also reflect the temporal and spatial characteristics of drought in real time， especially for the monitoring of drought processes above severe drought. The dry and wet evolution characteristics of Guizhou Province are obvious， that is， there is a general pattern from wet to dry from west to east. The wet areas are mainly concentrated in the northwest of the study area， while the drying trend is significant in the southeast and other areas. Drought occurs mainly in spring and winter in Guizhou Province， among which， drought occurs in the northwest in January， in the east and southeast in February， in central region in March and April， and in southwest in April. The results of this study can provide a reference for agricultural drought evaluation and drought prevention and mitigation work in Guizhou Province.

Long-term runoff forecast is of great significance for mastering future runoff information and realizing efficient utilization of water resources. At present， there are many models for long-term runoff forecasting， and each model has its own advantages and disadvantages under different forecasting conditions. In order to achieve mutual coordination and performance complementarity among multiple models， this paper selects the key predictors affecting the runoff in Huanren River Basin from the hydrological and meteorological factors by coupling the correlation analysis and forward-searching parcel method. Six runoff forecasting methods， including the statistical analysis and machine learning method are applied to forecast the annual and monthly runoff. And the applicability of the multi-model in the long-term runoff forecast of the basin is compared and analyzed. The results show that the correlations between the atmospheric circulation factors and the forecasted runoff are higher. The annual runoff forecast accuracy of the machine learning models， such as the artificial neural network model based on principal component analysis （PCA-BP-ANN） and the support vector machine （SVM） is higher than that of traditional statistical models. For the monthly runoff forecast in the flood season， the forecast accuracy of each model varies from month to month. The artificial neural network model based on principal component analysis （PCA-BP-ANN） has the highest forecast qualified rate in May and August and is about 10% higher than the artificial neural network model （BP-ANN）， but the forecast effect is not as good as other models in June and July. While the threshold regression model （TR） performs best in July， with a qualified rate of 94%. The mode is selected with the best performance in each month of the flood season to give a comprehensive multi-model forecast scheme. Under the optimal forecast scheme， the qualified rate of annual runoff forecast and the monthly runoff in July and August in the flood season are both higher than 90%.

With the development of urban economy and the acceleration of urbanization， the surface hardening area and the density of urban buildings increased， which changes the characteristics of regional hydrologic cycle and energy cycle. In order to further understand the evolution characteristics of regional hydrological factors under the influence of urbanization， Beijing is selected as the research object. On the basis of measured data， mathematical statistics method combined with ArcGIS software is used， the characteristics of land using change from 1980 to 2018 is analyzed. The variation and correlation of regional precipitation and temperature under the influence of urbanization is explored. The main conclusions are as follows. In terms of land use， from 1980 to 1990， the land use types in Beijing urban area did not change much， indicating that the land use development was relatively stable during that period. After 1990， it was the rapid period of urbanization， and the land development activities were relatively active， and the land use types changed dramatically， the cultivated land area and construction land area changed significantly. The area of cultivated land decreased significantly， the area of building increased significantly， and the area of green land and water surface increased slightly. Among them， the area of cultivated land decreased from 635 km² to 137 km²， the area decreased by 498 km²， and the proportion of the total area decreased from 46.1% to 9.9%， with a total variation of 78.4%. The area of construction land increased from 563 km² to 1 049 km²， the area increased by 486 km²， and the proportion of construction land in the total area increased from 40.9% to 76.1%， with a total variation of 86.3%. In terms of influencing hydrological factors， the rainfall and the maximum 5-day rainfall in urban and suburban areas showed a decreasing trend. With the development of urbanization， the rainfall amount and occurrence frequency in urban areas are higher than those in suburban areas. The number of days with rainfall of more than heavy rain increased， and the temperature from June to September increased， with the monthly average temperature rising in 1.81~2.72 ℃.The monthly average temperature rises the most in August. There is a positive correlation between the number of rainfall days above heavy rain and the temperature series in June， July and August. The results provide a basis for understanding the changes of hydrological factors under the current conditions and provided technical support for the flood control work in Beijing.

The contrast between water resource supply and demand is very prominent in the arid and semiarid inland basins of Northwest China. The plain area of those basins is arid， the groundwater is mainly formed in the mountains and their piedmont areas， and originate from the atmospheric precipitation and ice/snow melt water. Groundwater undergoes multiple hydro-chemical processes during the long-distance runoff before discharging from the aquifer， which determines the complexity of the formation and evolution of groundwater hydrochemistry in arid and semiarid basins. The hydro-chemical evolution of groundwater is the main factor affecting its chemical composition and content， and is also the internal mechanism controlling its quality. Therefore， the understanding of the evolution mechanism of hydro-geochemistry is of importance for the scientific management of regional groundwater resources， and is beneficial to coordinated development of the ecological environment and the economy in arid areas. In this study， the groundwater flow system of the northern Tacheng Basin is taken as the research area. The water–rock interactions that occur through groundwater flow are analyzed quantitatively by using inverse modeling based on selecting typical groundwater flow paths， identifying the potential mineral phases and reaction directions involved in hydro-geochemical processes， and calculating the evaporation degree of groundwater. Results reveal that water–rock interactions play a dominant role in the hydro-chemical evolution of unconfined groundwater， while evaporation has little impact on its hydro-chemical composition. Dissolution of gypsum， halite， and dolomite， positive cation exchange between Na⁺-Ca²⁺， minor plagioclase dissolution， and calcite precipitation occur in the groundwater system flowing from the recharge area to the discharge area. The runoff condition of the groundwater subsystem in the western region is better than that in the eastern region， and the groundwater circulation speed is faster. Thus， the contribution of water–rock reaction to the chemical components of unconfined groundwater is much lower than that in the eastern region and little dissolution of halite occurs. Consequently， the water quality of the groundwater subsystem in the western region is better than that in the eastern region. The results of this study provide a scientific basis for the optimal allocation and sustainable development of the groundwater resources in arid and semiarid basins of Northwest China.

The water supply mode of “ multi-source-multi-user” is a common mode in water resources supply and demand tension areas. How to use this mode to construct a reasonable water resources allocation scheme and alleviate or solve the contradiction between supply and demand of regional water resources is a topic worthy of study.In this paper， a water resource allocation model based on the priority scheduling of water source-user topological relationship is proposed. The water demand of different regions and industries is embodied to the water users. By constructing the multi-level topological relationship between the water supply order of the interaction between the water source and the water users， the water receiving priority of the water users， the spatial distribution relationship between the water sources in series or parallel， and so on， the priority scheduling is given priority to， and the order of all water supply behaviors of the “water source-user” in the region is obtained by unified coding. The goal is to meet the requirements of regional irrigation and water supply design guarantee rate， and take into account the fairness between water users. To achieve optimal allocation of water resources. In this paper， Qishui Irrigation area is taken as the research object. Based on five types of water supply sources such as reservoirs， rivers， lakes， groundwater， and reclaimed water reuse， five calculation slices such as Xieya， Huayuan， Feiyue， Yaoyingyan， and Huanghechang， and water use types such as agricultural irrigation and domestic industry， considering water saving and returning the basic ecological water quantity of rivers， a simulation model of water resource allocation based on the topological relationship between water source and water user is constructed to conduct a long series of adjustment from 1956 to 2018.In the planning level year 2035， the average annual total water demand is 2.49×10⁸ m³， the total water supply is 2.38×10⁸ m³， the water shortage is 0.11×10⁸ m³， the assurance rate of domestic and irrigation water supply is 95% and 80%， which meets the requirements， so as to meet the water demand of the irrigation area. The results show that the model can well simulate the allocation of “multi-source-multi-user” complex water supply and demand system.

The work of mountain flood disaster is defined as the focus of flood control and disaster reduction in China， and the success of mountain flood disaster warning is determined by critical rainfall， which is an important indicator. The Copula function is established based on the nonlinear relationship between variables. The functions of joint distribution and its marginal distribution function respectively can be linked. So that nonlinear， asymmetric and symmetric correlations among variables are described. In this paper， the Copula functions are used to describe the correlation between rainfall and peak rainfall intensity variables， and Gumbel， Clayton，Frank and mixed Copula（M-Copula） functions are used to construct the joint probability distribution model of 12 h site rainfall and peak rainfall intensity， respectively. Several Copula functions are analyzed in this paper. Finally， the M-Copula function is introduced， the multi-dimensional joint distribution of critical rainfall is constructed， and the joint distribution of rainfall and peak rainfall intensity is analyzed. The Huilongwan Formation of Baiguo Village， Junmahe Township， Xixia County is taken as an example. The critical rainfall of combined probability is calculated， the water level of mountain flood disaster， the critical rainfall of ready shift warning and immediate shift warning are warned and analyzed. The results show that the flood peak modulus of the river in hilly area has a certain law， the larger the basin area is， the smaller the flood peak modulus is， and the smaller the area is， the larger the flood peak modulus is. The calculation result of the design flow of 639 m3/s is reasonable. Based on the risk combination of mixed Copula function， the early warning results of mountain flood disaster in Xixia County are reasonable and reliable， and the mountain flood disaster warning in other areas is provided with theoretical support.

Constructing a complete index system and adopting effective methods are the core issues of water resources spatial equilibrium evaluation. In order to further improve the existing evaluation index system of water resources spatial equilibrium and optimize the evaluation methods， the basic characteristics of water resources spatial equilibrium reflecting three aspects of water demand， water development， and water supply-demand are taken as the evaluation sub-systems to establish an evaluation index system. A set pair analysis-variable fuzzy set coupling model is constructed to quantitatively reflect the fuzzy uncertainty characteristics of the water resource-socioeconomic-ecological environment composite system. By taking Jiangsu Province as the research object， a case study is carried out to evaluate the spatial equilibrium of water resources in 13 prefecture-level cities in Jiangsu Province from 2010 to 2019. The results show that from the perspective of spatial distribution， the spatial equilibrium degree of cities along the Yangtze River is relatively high， while that of Lianyungang and Yancheng along the coastal area is relatively poor. From the perspective of dynamic changes， from 2010 to 2019， the spatial equilibrium degree of five cities along the Yangtze River， such as Nanjing and Wuxi， has increased from critical equilibrium to relative equilibrium， Taizhou has increased from less equilibrium to critical equilibrium. Yangzhou has increased from critical equilibrium to relative equilibrium in 2016， and then decreased to critical equilibrium in 2019. Huai’an and Suqian along the Jianghuai region have maintained at critical equilibrium， while the equilibrium degree of Xuzhou has upgraded formless equilibrium to critical equilibrium， which is the same as Lianyungang and Yancheng along the coastal area. The reasons for the relative lag of the water resources spatial equilibrium degree of Lianyungang and Yancheng are the water use amount per ten thousand Yuan GDP， the reclaimed water utilization rate， the average water resource amount per capita， the water quality compliance rate of water function zones and the water resources development and utilization rate. The results of coupling model are objective and reasonable when applied to quantitative evaluation of water resources spatial equilibrium.

The downstream area of Youluokou in Dayu County is the key flood control one， which is densely populated and economic core. However， the topography of the region is characterized by a high periphery and a low middle， which makes it highly susceptible to flooding and causes large losses and disasters， which is not conducive to the sustainable economic development of the region. Therefore， it is of great practical significance to carrying out flood risk zoning to guide the construction of non-engineering measures for flood prevention and mitigation in the area. In this paper， the key flood control area in Dayu County and downstream is taken as the research object， and the river floods from the underflow of Youluokou Reservoir and small tributaries on both sides of the Floating River and Zhangjiang River are taken as the main flood sources， and a two-dimensional hydrodynamic model of the river and the study area as a whole is constructed based on the self-developed flood risk analysis software. The model is also rate validated by using historical empirical data from 2002 and 2009， respectively. On this basis， the flood risk of diffuse embankment under different design flood frequencies of 20， 50 and 100 years is analyzed， and factors such as maximum inundation depth， maximum inundation flow rate and maximum inundation duration are extracted， and the flood risk zoning of the area is analyzed by the integrated risk degree method. The results show that Fujiang， Huanglong， Qinglong， Chijiang， Xincheng and other key flood control areas are seriously affected by floods. The main impact area is distributed in the right bank of the Zhangjiang River， and a small part of the impact area is distributed in the left bank of the Zhangjiang River， and the total inundated area amounts to 68.91 km². The overall risk zoning is divided into four grades： low， medium， high and extremely high， accounting for 17%， 12%， 18% and 53%， respectively. So the results are helpful to providing decision-making basis for the construction of non-engineering measures for disaster prevention and mitigation and territorial space planning in Dayu County.

Ecological base flow is responsible for maintaining the stability of river form and ensuring the basic health of ecological environment in river. It is very important to determine the ecological base flow of rivers to protect the ecological environment of river basin and promote regional economic and social development. Based on the monthly runoff data of Langan Hydrological Station， the ecological base discharge of Keriya River in arid area is calculated by using the Texas method， the guarantee rate method （Q_P method），the typical hydrological frequency year method， the northern great plains resource program method （NGPRP method）， the driest monthly average flow in the past 10 years， the frequency curve method and the annual distribution method respectively. And starting from the basic functions of the ecological base flow， from the stable channel of basic form， basic survival safeguard river aquatic organisms， reflect the characteristics of the runoff during the year and change in three aspects， such as drawing water standards， and evaluation of different methods from the aspects of water ecological base flow calculation results of standard situation， comprehensive analysis and evaluation of the applicability of different calculation method. At the same time， combined with the runoff characteristics of Keriya River， the traditional ecological base flow calculation method， Texas Method is improved. The annual corresponding water amount of ecological base flow calculated by the improved Texas method is 189 million m³， accounting for 24.83% of the total annual runoff of Keriya River， and the corresponding water amount of ecological base flow in the flood season is 102 millionm³， accounting for 20.1% of the runoff of the same section. The corresponding amount of ecological base flow in non-flood season was 87 millionm³， accounting for about 34.4% of the runoff in the same period. Studies suggest that the ecological base flow calculated by the improved Texas method can not only meet the demand of different standard water quantity in different periods of the year， but also give more reasonable consideration to the runoff characteristics of rivers with great difference in annual distribution and the actual situation of total water resource scarcity in the basin. In the protection of river play its basic functions， maintain stable form， under the premise of avoiding serious damage to the ecological environment， water is used as much as possible for the local people’s production and living water， growing a better balance in the region ecological environment water use and the contradiction between production and living water， has a certain practical significance.

This paper aims at improving the problem of gradient forecast of traditional Recurrent Neural Networks （RNN） and exploring the use of combination model in rainfall water level forecast. A combination forecast model on account of Gated Recurrent Unit （GRU） and BP neural network is proposed so as to forecast the West Lake rainfall water level at the source of the Headwaters of the Liede Chung Valley in Guangzhou. The study uses the hydrological time series of West Lake from March to July as the training set， and August as the test set. The optimal parameters of the GRU-BP model are determined by the control variable method. The model uses the historical rainfall and water level of the West Lake monitoring points as input conditions to predict the water level process in the next 1 hour， model corrects the forecast error by non-linearly assigning the output vector weights to the individual model framework through the GRU fusion layer.The feedback weight of water level increment by information of water replenishment， drainage time series change and rainfall is allocated accurately by parallel ensemble method. The results show that compared with the combined model based on convolutional neural network （CNN） and GRU， GRU， Long Short-Term Memory network（LSTM）， and BP， the overall prediction accuracy of the GRU-BP model increased by 10.6%， 17.2%， 32.5%， and 51.2%， respectively. short time series （March-April） and typical rainy season hydrological time series （May-July） are further selected to train the model， and the influence of different prediction step sizes on the model accuracy is discussed under the condition of constant parameters. The results show that when data-driven models are used， typical and representative hydrological data should be selected for training as much as possible. When the model predicts the water level in the rainstorm period and heavy rain period， when the prediction step is set to 30 min， a certain advance time can be obtained， and a better prediction accuracy can also be obtained. The accuracy and stability of the GRU-BP ensemble are improved， providing a new method for lake water level prediction.

Reservoir （Group） flood control operation is a hot topic in the research on non-engineering flood control measures at present. With the development of hydrological prediction technology， real-time flood control operation of reservoir combined with prediction information is widely used. How to further carry out the real-time flood control forecasting-optimization operation of reservoir combined with prediction information is the focus of relevant research on improving reservoir flood control benefits. Therefore， by taking the real-time flood control operation of the reservoir for the downstream control points as an example， this paper puts forward a real-time forecasting-optimization operation strategy. The strategy establishes the optimal operation model of reservoir flood control operation considering the maximum peak clipping criterion in the forecast period， makes full use of the flood forecast information in the forecast period to carry out the optimal operation calculation， guides the real-time flood control operation of the reservoir according to the decision-making of the period faced in the optimal operation results， and rolls out the above “forecast optimization operation” process to assist the flood control operation of the reservoir， so as to effectively retain and store the flood. Taking the flood control operation of Wan’an Reservoir in the middle reaches of Ganjiang River as an example， the relevant experimental results show that： ① the proposed real-time forecasting-optimization operation strategy improves the flood-peak rate by about 10% compared with the current flood control operation rules under the condition of 48 h forecast period. ② To carry out the real-time flood control forecasting-optimization operation， the flood prediction period shall be at least 2 more periods than the flood propagation delay. The flood control forecasting-optimization operation of Wan’an Reservoir for Ji’an Station at the downstream needs at least 30 h effective flood forecasting information （when the operation time step is 6 h）； ③ Considering the prediction error， the flood-peak rate of the optimal operation strategy of real-time flood control prediction is reduced， but it is still significantly better than the current operation rules.

Leaching soil salt with flood irrigation in winter and spring is a widely used water and salt management method in arid saline-alkali areas such as Xinjiang and Hetao in Inner Mongolia. It is of great theoretical and practical significance to clarify the influence mechanism of different winter and spring irrigation strategies on soil salt migration and quantify the process of soil water and salt migration in the fallow period， so as to formulate a scientific and reasonable winter and spring irrigation scheduling and reduce the quota of winter and spring irrigation. The predecessors have carried out a lot of research on the salt leaching effect of different winter-spring irrigation strategies， which has provided strong support for the formulation of winter-spring irrigation regimes and the prevention and control of soil salinization in Xinjiang and the Hetao District in Inner Mongolia. In this paper， the influence of irrigation quota， irrigation technology， freeze-thaw effect， straw mulching and deep burial， subsurface pipe salt drainage technology on the salt leaching effect of winter and spring irrigation， and the application of model simulation in the study of salt leaching in winter and spring irrigation in saline alkali areas of North China are summarized. And it is proposed that in the future research， the innovation of salt leaching technology mode of winter and spring irrigation， quantification of soil water and salt migration process during freezing and thawing periods， optimization of straw mulching and deep burial， subsurface pipe salt layout mode， simulation of regional scale salt leaching and selection of new models of farmland water and salt management to replace conventional winter and spring irrigation should be strengthened.

Mountain rivers are usually narrow. During the flood season， flood discharge period， or in the circumstance of the dam break in the upstream reservoir， water level in the river channel increases significantly in a short period with great energy， flood wave can penetrate into the drainage pipe networks through the outfalls， and further become inundation after overflowing from manholes in inland areas. If the overflow flood inundates the street before the river flood or urban flood really happens， it may cause great inconvenience to people and vehicles， and even have negative influence on the available evacuation time and routes. Based on the above， a coupled flood model integrating a 1D drainage pipe model and 2D overland flooding model is proposed， which is validated by using an idealized case and small-scale physical model experiment. Results show that the proposed modeling method can reproduce the overflow inundation depth and area satisfactorily， and the model can be applied to predict the pipe overflow flood effectively and provide technical support for emergency management and disaster mitigation. Through the numerical and experimental study， it is confirmed that the manholes in the main pipe and the pipe near river channels have great risks of suffering overflow inundation due to a serious river flood. The highest water level of the river flood， its initial increasing speed and the duration all have effects on the overflow. The river flood with sharp increasing waves may induce the water spurt from manholes. For the areas that is vulnerable to this type of overflow inundation， proper installation of floodgates in the outfalls is recommended. Since the surface tension in the inwall of manholes is not taken into account in the present model， the simulated inundation area is not in good agreement with the measured， especially during the flood receding period. The model overestimates the water volume flowing back to the pipe system through manholes compared to that in real situations， in which the surface tension in the inwall of manholes stops the water flowing into the manhole. Besides， there may be additional sediments accumulation in the pipe after a long-term service without appropriate maintenance， which could reduce the pipe drainage capability. In the future study， these factors would be incorporated as well as the discussion on the effect of floodgates.

Rural water conservancy is one of the important tasks in the rural revitalization strategy. Due to the improvement of rural water conservancy in the new era， the Hubei Provincial Water Resources Department organizes an investigation team to conduct investigation in Jiangsu Province and Shaanxi Province， and the investigation focus is the experience and practices of the two provinces in standardized management of irrigation areas， comprehensive reform of agricultural water prices， and management and supervision of farmland water conservancy projects. According to the investigation， the development of rural water conservancy work needs to implement government responsibilities， highlight planning and guidance， pay attention to project management and protection， adhere to ecological priority， and improve the grassroots system. Further， based on the investigation and summary， suggestions are made for the development of rural water conservancy work in Hubei Province， and these suggestions have important reference values for the other regions.

Based on principal component analysis method， 11 indicators were selected to study the agricultural water use trend and structure in Anhui Province. Moreover， main driving factors affecting the water use structure were determined； and their effects on the structure of agricultural water use were discussed. The results showed that the total water resources and per capita water resources in Anhui Province fluctuated greatly from 2010 to 2019. Agricultural water consumption and its proportion in total water consumption showed an overall downward trend year by year； The proportion of farmland irrigation water in agricultural water consumption gradually decreases； The proportion of water for forestry， animal husbandry and fishery in agricultural water consumption gradually increased. The structure of agricultural water consumption tended to be rationalized. Rural per capita disposable income， total output value of agriculture， forestry， animal husbandry and fishery， total population， water-saving irrigation area， effective irrigation area， average temperature and precipitation were the main driving factors affecting the change of agricultural water use structure in Anhui Province. The relevant measures of agricultural water saving in Anhui Province were proposed. The research results can provide reference for rational utilization and scientific distribution of water resources and agricultural sustainable development in Anhui Province.

In order to analyze the motion state and hydraulic characteristics of the upturning flap valve during the start-up process， taking the upturning flap valve of the axial-flow pump unit as the research object， the Realizable k-ε turbulence model is applied， and the unit is designed by the user-defined function （UDF） by using the smoothing method and reconstruction method in the moving grid， combined with the 6DOF algorithm， to simulate the opening process of the upturning flap valve. The research results show that during the startup of the unit， the upturning flap valve will be closed for a short time due to the combined force， and then it will be flushed open by the water flow. The opening speed of the flap valve is fast at first and then slow and tends to be stable. The rapid opening process of the flap valve in this study is 0.021~0.654 s， the maximum flap valve opening is 23.76°， and the flap valve opening degree after the unit stabilizes is maintained at 20.36°.At the moment when the flap valve is opened， the moment and the hydraulic loss before and after the flap valve are relatively large， and then decrease with the increase in the opening degree and tend to be stable. The average flapping moment in the research process is 11 746.17 N·m. The average hydraulic loss before and after the flap valve is 0.20 m， and the average hydraulic loss coefficient before and after the valve is 1.43.

Water quota management is the means and guarantee for the effective implementation of water-saving work， and an effective water quota evaluation system is the basic work to standardize the formulation of water quota and strengthen the water quota management. In order to overcome the shortcomings of the current water quota evaluation is mainly qualitative evaluation， and some quantitative evaluation have not yet formed a unified evaluation index system， a quantitative assignment method is proposed and applied to the agricultural water quota evaluation in Guangxi. According to the evaluation content proposed in the “Technical Requirements for Water Quota Evaluation”， this method establishes an evaluation index system including the agriculture water quota evaluation contents of “four properties”， and quantitatively evaluates agricultural water quota. The evaluation results show that the coverage of agricultural water quota in Guangxi is “strict”， the rationality is “reasonable”， the practicality is “strict” and the progressiveness is “reasonable”. The quantitative evaluation method is a full quantitative evaluation method， and it is closely integrated with the “Technical Requirements for Water Quota Evaluation”. It overcomes the shortcomings of the current evaluation methods such as subjectivity and inconsistent indicators， and it can provide a reference basis for water quota evaluation in various provinces and regions in China.

Crop water use efficiency is an important indicator to measure the scientific and rational nature of agricultural water use， and the study of sugarcane water use efficiency is a key scientific issue to achieve its efficient irrigation management and improve the development of China’s sugarcane industry. In this paper， based on the SPEI index， a typical drought year is selected， and the DSSAT-Canegro model is used to simulate the response mechanism of sugarcane yield to irrigation system scenarios in different typical drought years， Crop water productivity （WP）， irrigation water productivity （WUE_ti ）， generalized water use efficiency （WUE_g ） and irrigation water use efficiency （WUE_i ） are evaluated and analyzed based on the simulation results. The study clarifies that the maximum， minimum and mean values of simulated yields in different typical drought years show a significant increasing trend with increasing irrigation quotas； WUE_g， WUE_ti， and WP indicators can better reflect the relationship between sugarcane yield and water consumption， and the correlation between the three is significant， but WP is not easily available due to the data of field evapotranspiration， which limits its application in the large-scale and long period. WUE_i reflects only the relationship between sugarcane yield and irrigation and is not applicable to areas with abundant precipitation. After the analysis， WUE_g and WUE_ti are recommended as sugarcane irrigation water use efficiency indicators in Laibin， Guangxi. The study serves as a reference for irrigation water use efficiency evaluation and irrigation decisionmaking.

To study the improvement effect of biochar in brown soil area of eastern Loess Plateau， and to investigate the effect of biochar application rate on the water infiltration pattern. In an indoor one-dimensional soil column vertical infiltration test， six application rates （0， 1%， 3%， 5%， 7%， 9%） were set to monitor the transport of wetting fronts and the changes of cumulative infiltration volume and infiltration rate within 3 h. The water content of the soil column at 3 h was measured at 2.5， 5， 7.5， 10， 12.5， 15， 17.5 and 22.5 cm. of soil water contents. The infiltration rate is simulated by Kostiakov， Philip model and Horton model， and the better fitting was Kostiakov model， which was suitable for simulation and analysis of different biochar application rates. The power function can be used to well analyze the law of biochar on the transport of wetting fronts. The application of biochar has a reduction of infiltration effect on the soil in brown soil area， and the higher the amount of biochar application， the smaller the infiltration rate， cumulative infiltration volume and wetting front transport distance， and the higher the soil water contents.

Taking a water supply project in Northwest China as an example， the energy dissipation scheme of setting a diversion outlet at the bottom of the inverted siphon with large drop are designed and studied. By comparing the characteristics of the piston-type regulating valve and the sleeve-type regulating valve， the piston-type regulating valve is selected as the energy dissipation valve type of the diversion outlet； On this basis，the design scheme of two-stage energy dissipation is determined， and the reasonable outlet type of the energy dissipation valve and the operation and control mode of the piston valve when piston valve is running in series are selected by analyzing the cavitation of equipment and piston valve. The energy dissipation scheme has been successfully applied in engineering practice and can provide reference for similar projects.

The sponge city construction has been comprehensively promoted in China since its implementation in 30 pilot cities. However， as a direct beneficiary of sponge city program， the public awareness of sponge cities is poor. The low degree of public participation will affect the sustainable construction and development of sponge cities. By taking the sponge city pilot area in Qingshan District of Wuhan as an example， this paper conducts a questionnaire on the public perception of the concept， effect and fund-raising mode of the sponge city. The results of 775 valid questionnaires show that， in terms of the concept and effect of the sponge city， 82% of the respondents are aware of the sponge city construction （SCC） in the city. Respondents， not aware of the SCC are younger， less educated， have shorter residence periods in Wuhan， or lower incomes. Senior citizens know about SCC mainly through TV and newspapers， while the young and middle-aged people know about SCC mainly through mobile apps. More than 80% of the respondents agree that the SCC is efficient in mitigating urban waterlogging， increasing green space， improving life quality， and raising real-estate values in surrounding areas. In terms of fund-raising modes， more than 70% of the respondents think that public private partnerships are more conducive to sustaining the financial support to SCC than sole funding by the government， but still nearly half of the respondents would rather the governments funded SCC. The proportion of such preference increases among the age of the respondents. Elderly respondents are more likely to choose government funding for the SCP than the younger ones. Interestingly， respondents， who believe that waterlogging is caused by multiple factors， or that SCC is efficient in mitigating urban waterlogging and improving life quality. This study may provide a reference for enhancing public participation and public investment for the future SCC.

To study the ecological quality and its change characteristics under land use change in Yigeziya River Basin from 1990 to 2019， this paper provides a scientific basis for the utilization of land resources and the sustainable development of regional economy in arid areas. Based on the Landsat TM remote sensing image data of four periods in 1990， 2000， 2010 and 2019， the land use change process is analyzed， the temporal and spatial evolution characteristics of land use and vegetation coverage in Yigeziya River Basin are studied， and the environmental quality of the basin is evaluated. The results show that： ① From 1990 to 2019， the cultivated land area in Yigeziya River Basin increased by 225.02%， and the construction land area increased by 56.36%. ② The total forest land area of Yigeziya River Basin in 2019 increased by 31.00%， 216.40% and 325.06% respectively compared with that in 1990， 2000 and 2010. Among them， the area of natural forest land changed little on the whole， only decreased by 9.80%. The area of artificial forests continued to increase by 594.00%， and the areas of forested land， sparse forest land， and shrub forest land decreased slightly during the entire period， indicating that the natural forests in the Yigeziya River Basin had suffered the least damage in the past 29 years. ③ From 1990 to 2019， the total area of grassland in Yigeziya River Basin increased slightly at first and then decreased， but the general change trend is to decrease. In the past 29 years， the grassland area with high-coverage and low-coverage showed a decreasing trend， and the area in 2019 decreased by 33.61% and 36.59% respectively compared with 1990. The area of medium-coverage grassland shows an increasing trend， with an increase of 31.06% in 2019 compared with 1990. The expansion is partly due to the degradation and transformation of high-coverage grassland into medium-coverage grassland. ④ In 1990， 2000， 2010 and 2019， the EI index range of Yigeziya River Basin was 20≤EI<35， belonging to the poor range. Among the four results， the EI index in 2000 was the lowest and the EI index in 2010 was the highest. Therefore， the overall ecological environment of the basin can be expressed as follows： the vegetation density in the region is small， the biological richness in it is low， the precipitation in it is small， and it is not suitable for human survival and residence.

Groynes are common river regulation structures， and water is stagnated in a groyne field formed between two adjacent groynes when flowing through groynes. The flow characteristics of the groyne fields in the river play an important role in local ecological environment. To explore the influence of submergence on the flow characteristics and mass exchange in the groyne field， this paper establishes a single groyne field model by using the RNG k-ε model in Fluent and the VOF method is used to capture the free surface. The effects of submergence on circulation system， velocity distribution， mixing layer thickness， and exchange coefficient are studied. The results show that there are lateral circulation and vertical circulation in the submerged groyne field. With the increase in submergence， the thickness of lateral mixing layer decreases， while the thickness of vertical mixing layer increases； the groyne field mainly exchanges with the main channel through lateral mixing layer and vertical mixing layer when it is under low submergence and high submergence respectively. There are two exchange processes between the groyne field and the main channel. With the increase in submergence， the exchange coefficient in the rapid exchange stage decreases and the exchange coefficient in the slow exchange stage increases first and then decreases.

In order to explore the pollutant consumption law of farmland under different drainage modes， taking Yunnan ecological irrigation area in Sucheng District of Suqian City as the research object， the site selection， sampling and determination of pollutant contents are carried out， and the pollutant removal effects of different channel systems （System 1， Ditch gate regulation and storage system； System 2， farmland ditch direct drainage system； System 3， with gate and without agricultural ditch system） are studied. The results show that compared with the three channel systems， the effect of system 1 is the best. In the irrigation season， the pollutant removal effect of farmland drainage ditch system is the best in July and August. In the non-irrigation season， due to the long-term closure of the sluice gate of the bucket ditch in system 3， the ponding in the ditch is turbid， and a large number of algae and duckweed cover the water surface， resulting in the highest COD concentration in the bucket ditch in May and November. Although the ditch system of system 2 is relatively perfect， there is no control gate， the height difference ranging from the main ditch to the branch ditch is large， the flow velocity is fast， and the residence time of farmland drainage in the ditch is short， which is not conducive to giving full play to the sewage interception function of the ditch system. Therefore， as far as the farmland drainage system plays the function of absorbing pollutants， the sluice or overflow dam should be arranged at the end of the branch ditch， main ditch and agricultural ditch， or the slope of the ditch should be reduced to slow down the water velocity， so as to prolong the time of absorbing pollutants in the ditch.

There are a large number of unpaved earth roads in farmland and orchards in Loess Plateau of China. These roads are not only a seasonal channel for local people to carry out agricultural production activities， but also an important source of soil erosion and a channel for runoff and sediment transportation， which has a serious impact on the production and life of locals and the natural ecological environment. In order to solve this problem， indoor simulated artificial rainfall and flow scouring tests are conducted to identify the variation characteristics of runoff， sediment yield and hydraulic parameters on unpaved and grass-covered earth road surface in Loess Plateau， and to analyze relationships of soil detachment rate and runoff hydraulic parameters. The results are as follows： ①soil detachment rates decrease 18.25%~63.28% after planting grass on unpaved earth road surface. ② runoff coefficients increase obviously on grass-covered earth road surface within a short period of time after grass is planted； ③ soil detachment rates have extremely significant correlation with runoff velocity， shear stress and significant correlation with stream power， unit energy of water-carrying section on unpaved earth road surface. The best simulation effect is stream power following shear stress； ④ soil detachment rates have extremely significant correlation with all hydraulic parameters on grass-covered earth road surface. The best simulation effect is runoff velocity following shear stress. The research results can provide a scientific reference for the prevention and control of soil erosion on earth road surface in this area.

Non-point source pollution carried by rainfall runoff is the main natural element driving the variation of river water pollution， where the mechanism of non-linear influence of rainfall on river water pollution has been a difficult research focus at the intersection of hydrology and environmental disciplines， and there are significant differences in the effect of the magnitude of rainfall intensity on pollutant discharge. Xinfeng River is one of the important ecological corridors in Beijing， the capital city of China， and the water quality of the river is strongly influenced by rainfall. To explore the influence of rainfall on the pollution change characteristics of urban river water bodies， this paper analyzes the water quality change and its response relationship to rainfall and the pollution output characteristics under different rainfall intensities based on the long series of water quality and rainfall data from 2015 to 2019 at the exit section of Xinfeng River， a typical black smelly water body in Beijing， and scientifically elucidates the non-linear response law of river pollution under different rainfall intensities. The results show that： ① the outlet water quality of the basin improved from inferior V class to III~IV class， turning point appeared between 2017 and 2018， and its correlation with rainfall directly reflected the change of watershed pollution from point source control to non-point source control； ② the average concentrations of COD， ammonia nitrogen and TP were higher in moderate and heavy rain， but lower in torrential rain and extraordinary rainstorm， with an increase in rainfall intensity， the component concentrations increased first and then decreased； ③ there is a significant quadratic function between rainfall and water quality concentration under different rainfall intensity， and the change of water quality depends on the diluting or scour effect of rainfall. This paper aims to reveal the response relationship between pollutants in urban rivers and meteorological elements in the watershed from an academic point of view， and to propose scientific references for the prevention and control of nonpoint source pollution in other urban rivers.

The impact on human and natural ecological systems caused by extreme weather events under climate change conditions has received widespread attention. A continuous water quality monitoring is taken in the mainstream of Yellow River after July 20’s rainstorm in Henan Province to reveal the contaminant transportation rule during this flood event and study the influence on water quality in mainstream of Yellow River. The results show that the variation trend of sediment concentration keeps consistent with that of discharge， it has significant positive correlation with discharge， the concentration increases first and then decreases， and it is affected by rainfall confluence， peak value appears differently. The peak value of flow emerges one day behind that of rainfall. As for the water quality， the rainstorm brings a bad influence on water quality in mainstream of Yellow River， Henan Province， and the major excessive pollutants are total phosphorus and total nitrogen. The concentration of total phosphorus exceeds the standard in July 21th， and then turns normal in a short-term， while the concentration of total nitrogen increases firstly， and then decreases after the peak value. The concentration of other water quality indices fluctuate at first during rainfall period and the concentration can turn normal in a few days after the rain. Overall， this rainstorm causes a serious excess of total nitrogen， and its duration of pollution is longer than TP and other indicators. The source of nitrogen and phosphorus are different. What is more， the water pollution caused by rainstorm is dynamic and retrieval， the total pollution load has not exceeded the environmental capacity of Yellow River mainstream for a long time. To protect the healthy life of Yellow River， the measures of LID measures， tillage mode adjustment， storage pool， ponds， riparian buffers and other measures should be taken to reduce the risk of pollution during rainstorm period.

Tidal energy is a renewable and pollution-free energy with huge reserves. The research on the distribution characteristics of tidal energy resources is of great practical significance for the development and utilization of the tidal energy in China. At present， the investigation of tidal energy resources is mostly the analysis and statistics of discrete point resources， and there is a lack of continuous calculation of and research on the tidal energy resources in the whole sea area. In order to understand the distribution of resources in the whole sea area， a numerical model of the tidal wave motion in the East China Sea is established. The numerical simulation results are in good agreement with the coastal stations and the co tidal map given by predecessors based on measured data. On this basis， combined with the numerical simulation results and the national standards issued in recent years， the spatial distribution laws of the technical exploitable level， theoretical average power and annual reserves of tidal energy resources in the East China Sea are evaluated. The results show that due to the change of lunar orbit， the annual average tidal range variation period （about 19 years） and phases are equal， but amplitude is different. Most sea areas in the East China Sea have a small average tidal range and are poor in tidal energy resources， but a small number of sea areas such as the West Bank of the Korean Peninsula， Hangzhou Bay and Taiwan Strait have an average tidal range of more than 4.5 m. They are rich or relatively rich in tidal energy resources， and their theoretical average power and annual potential tidal power reserves can above 2×10³ kW/km² and 2×10⁸ kWh/（a·km²）. The average tidal range in most coastal areas of Zhejiang， Fujian and Northern Jiangsu is around 3.0~4.0 m， which is mainly the available area of tidal energy resources. The theoretical average power and annual potential tidal power reserves are about 1.3×10³ kW/km² and 1.3×10⁸ kWh/（a·km²）. Compared with the average tidal range， the spatial distribution of annual potential tidal power reserves and theoretical average power in different sea areas is more uneven.

Hydropower has such characteristics as renewable energy， large-scale storage， cross space-time regulation and comprehensive utilization， low operation costs and low environmental pollution. However， at present， a lack of price adjustment mechanisms for old hydropower， the weak linkage between price and capacity cost， and the inadequate embodiment of environmental benefits have led to the inability of hydropower feed-in tariffs to reflect the true value of hydropower. In this context， taking Sichuan province as an example， this paper firstly analyzes the hydropower development and points out a series of problems such as low backward pricing in hydropower outward transmission， and proposes corresponding solutions. Then， the benchmark price of coal-power in the landed province is backwardly deducted from the transmission and distribution price. A competitive analysis method for outward hydropower is proposed， which is compared with hydropower feed-in tariffs. And based on the capacity compensation and green value， a feed-in tariff measurement model is proposed to truly reflect the capacity cost and environmental value of hydropower. Finally， on the premise of measuring the competitiveness of outward hydropower in Sichuan Province， a hydropower plant is selected to measure two tariff mechanisms， which provides a basis for the adjustment of hydropower feed-in tariff.

As a new type of dam， the performance of the cemented sand and gravel dam has attracted widespread attention. In order to explore the working characteristics of the cemented sand and gravel dam， based on a 40.6 m high dam， a centrifuge modeling test with a similarity ratio of 65 is designed and carried out. The results show that under self-weight settlement condition， the displacement of the dam is symmetric about the dam axis， and the displacement value increases gradually from the bottom to the top of the dam. With the increase in the headwater level， the displacement of the dam body gradually deflects to the downstream. Then， the lattice discrete particle model （LDPM） is briefly introduced. Combined with triaxial compression test， model parameters are calibrated. By comparing the results of centrifuge modeling test， the applicability of numerical model is verified. Furthermore， according to the water density overload method， the overload coefficient K is introduced to explore the overload capacity and failure mode of the cemented sand and gravel dam. The simulation results show that when K<2， no cracks appear. As the K value increases， cracks first appear at the dam heel， and then gradually extend upward and toward the toe of the dam. It proves that cemented sand and gravel dam has strong overloading capacity.

With the continuous in-depth development of hydropower industry， the development of new hydropower station is becoming more and more difficult. In addition， the high-quality development of energy and the continuous promotion of electric power system reform have higher requirements for the management level of existing hydropower stations. The existing operation evaluation system of hydropower station is unable to make a horizontal comparison among different types of hydropower stations， so this paper takes 65 hydropower stations in a province as the research object， focuses on the quantitative expression of operation differences of hydropower stations， and innovatively proposes the concept of operation difficulty coefficient of hydropower station to effectively quantify the operation difficulty of hydropower stations and reflect the operation and management of hydropower stations in operation in a more comprehensive and objective way. It centers on the core thought of benchmarking management to conduct a benchmarking evaluation research based on the operation difficulty coefficient of hydropower stations by extracting the characteristic attributes of hydropower stations with different importance degrees and using theories and methods such as random forest regression and extenics. Moreover， the paper quantifies the model based on the operation difficulty coefficient， inputs the data of power stations for index calculation， and combines information entropy weight and improves extenics method to get the evaluation results， which are consistent with the self-evaluation results of the enterprise. The results show that the proposed benchmarking evaluation method based on operation difficulty coefficient is reasonable and adaptable， and can provide a reference for the development of optimization and compensation of hydropower enterprises.

In order to study the applicability of free-surface-pressurized flow in the tailrace tunnel of the hydropower station with circular sections， this paper uses one-dimensional calculation based on the improved virtual slit method and three-dimensional calculation method based on CFD and VOF models to numerically simulate the hydraulic characteristics of the large fluctuation transition process. The results show that the fluctuation of the free-surface-pressurized flow interface of the tailrace tunnel includes three processes： recession， slot filling， backwater， and there is no obvious difference in hydraulic characteristics between the two cross-sections. The free-surface-pressurized flow interface of the tailrace system shows obvious three-dimensional fluctuations， and the three-dimensional calculation has obvious wavefront phenomena. The movement of the free surface-pressurized flow interface is accompanied by the generation， development， broke and collapse of trapped air. However， the impact pressure of the collapse of trapped air at the top of the tailrace tunnel in this paper is relatively small， which will have no obvious impact on the structure. Therefore， the tailrace system with circular sections has no adverse flow pattern under the free-surface-pressurized flow conditions， and can be applied to engineering projects.

As the core component of the power system， the overheating fault of switchgear is the main fault mode. How to make full use of the multi-source information of switchgears， conduct switchgear temperature rise mechanism and data analysis and evaluate the temperature rise risk has become an urgent problem in the power system. Considering the influence factors of temperature rise such as account data， operation data， monitoring data and environmental data of switchgear， this paper puts forward a risk assessment method of switchgear temperature rise based on adaptive BP neural network. Through a mechanism analysis of the switchgear temperature rise， the main factors of temperature rise are determined as the input of the model， and the temperature rise risk level is taken as the output. The adaptive genetic algorithm is used to adjust the network parameters in real time to improve the training efficiency and accuracy of the network， and a temperature rise risk assessment method named ABPNN is established. The experimental results show that compared with the traditional BP neural network and GA-BP neural network， ABPNN can predict the risk level of switchgear temperature rise more quickly and accurately and support the construction of the switchgear operation， maintenance and repair system.

The problem of oil leakage and oil rejection of hydro-generator unit bearing pedestal has become one of the bottlenecks that need to be broken through in unit operation and maintenance. In order to ensure the economy and security of generator unit operation in hydropower stations and the personal security of operation and maintenance personnel， the oil leakage of bearing pedestal of two 3.2 MW horizontal three fulcrum hydro- generator units in a hydropower station in Hubei Province is studied as an example. Firstly， the causes of oil leakage are analyzed. Secondly， aiming at the dilemma of the existing sealing oil leakage prevention methods， this paper proposes a bearing pedestal oil leakage prevention method based on negative pressure. Then， the intelligent control device of negative pressure vacuum pumping combined with the software and hardware corresponding to proposed method is developed. Finally， the developed device is applied to the hydropower station， and it succeeds in solving the oil leakage problem.

The frequently changing of working conditions of hydraulic turbine generator units during operation will lead to the intense vibration of runner blades. In order to explore the influence of working condition parameters on the vibration characteristics of runner blades， an analysis of the sensitivity of the runner blade dynamic response is carried out based on Sobol’ method. Firstly， according to the dynamic model of runner blade， the expression of dynamic response of runner blade is deduced. Then， based on Sobol’ method， the sensitivity of runner blade dynamic response to working condition parameters is deduced， and the internal relationship between the runner blade dynamic response and working condition parameters is revealed. Finally， the sensitivity of runner blade dynamic response to speed is calculated through an example， and the influence of speed on the runner blade dynamic response is analyzed. The results show that when the speed / rated speed is 0.6 and 1.2， the dynamic response of the blade is the most sensitive to speed， which provides a theoretical basis for a further research on the vibration control of the runner blade and the safe operation of the units.

An intelligent mobile inspection system for dam safety is developed based on image recognition technology and orbital robot. The system is based on the orbital robot and its carrying equipment to realize the information collection of the inspection objects. On this basis， the image data analysis and fusion analysis are carried out based on the image recognition technology. The system has been applied in a project. Results show that it can solve the problems of limited scope of traditional manual inspection and difficulty for hydraulic workers to carry out on-site inspection under extreme natural conditions. Besides， it can effectively realize the functions of remote control mobile inspection for dam operation safety， automatic identification of defect characteristics， and automatic reading of manual reading devices for important monitoring facilities.