Abstract:The non-stationary characteristics of the average runoff in driest days are tested in this paper based on the measured runoff data of Tangnaihai Hydrological Station from 1957 to 2018 using the 5-year moving average and Mann-Kendall abrupt change test to analyze the effect of climate change on the non-stationary of hydrological extreme value. According to the Kendall rank correlation analysis method, the climate index was selected, and the non-stationary generalized extreme value distribution model (generalized extreme value, GEV) was constructed with time and climate index as covariates. Parameter estimation and model selection were carried out, and application effects of the stationary and non-stationary GEV models in the runoff simulation of dry season were compared. The results indicated that the dry season runoff shows obvious non-stationary characteristics. Meanwhile, the simulated value of the stationary GEV model is higher than the measured value, and the GEV model with the western Pacific index as covariate produces better fit for the extreme value, which better explained the volatility of extreme dry events.

Abstract:To evaluate the accuracy of extreme runoff simulation by combining the satellite remote sensing and the reanalysis data, the precipitation and temperature data of TRMM, PERSIANN-CDR, and CFSR, and measured data were selected to obtain eight combination schemes of precipitation and temperature. Hydrological models were utilized to evaluate the accuracy of different combinations in each extreme flow sequence. The results show that: among the combinations of remote sensing data without measured data, TRMM precipitation & CFSR air temperature and PERSIANN-CDR precipitation & CFSR air temperature are the best combinations for simulating the extreme high and low runoff, respectively; in addition to the reference combination (actually measured precipitation & measured temperature), measured precipitation & CFSR temperature and TRMM precipitation & measured temperature are the combinations with the highest simulation accuracy of the high and low runoff simulation, respectively; among the extreme flow series, CFSR precipitation & CFSR air temperature and CFSR precipitation & measured temperature seriously overestimate the extreme flow with the maximum overestimation reaching 651%, and the simulation error increases with the decrease of discharge. The other schemes underestimate the runoff with the maximum underestimation reaching 67.48%, and the error decreases with the decrease of runoff; The characteristics of extreme precipitation vary in different extreme value series. Compared with the other two precipitation products, TRMM can better reflect the frequency of extreme precipitation and the duration of no rain in the high flow series, while the precipitation of PERSIANN-CDR in the low flow series can best reflect the intensity, total amount, and characteristics of consecutive wet days.

Abstract:This study aims to construct the estimation method of river network regression coefficient C s that does not depend on the rainfall-runoff data. Four typical small and medium-sized river basins located in different hydrometeorological divisions are selected in this study. River networks are extracted from the DEM information, simplification schemes for the river network is constructed based on Strahler’s rule, the differential equation for the storage based on the self-similar river network method is improved, and the influence of different river length ratios on the C s calculation results is analyzed. The results show that: the improved method proposed in this paper can effectively reduce the difference of C s between the original river network and the simplified scheme to improve the stability; the increase of river network complexity in the basin usually leads to the increase of C s calculation results; the river length ratio affects the applicability of simplified scheme by influencing the information covered by the river network. For small and medium-sized basins with the 3-level structure, when the length ratio of the level 1 river network is less than 70%, the simplification solution of river network retained to level 2 can be used as an alternative input.

Abstract:In order to make the HEC-HMS model universally applied in different hydrometeorological regions, the SCS-CN method in the HEC-HMS’s director runoff module was improved according to the small and medium-sized watersheds of Xianbeigou, Chengcun and Pinghe. The improvement measures include replacing the previous 5 days’ rainfall with the antecedent impaction precipitation P a to evaluate the previous soil wetness, adopting the linear interpolation to increase the classification of CN( Cx ) and selecting the appropriate initial loss rate λ according to the different meteorological and hydrometeorological region. The limitation of the inverse algorithm in the calibration of SCS model parameters is discussed. By calibrating the optimal Cx under the pre-affected rainfall in different watersheds and regressing the Cx-P a relationship, we explored the law of the change of actual wetness with the pre-affected rainfall. The results show that when the optimal initial loss rate is 0.05 in the humid region and 0.20 in the sub-humid region, a better simulation accuracy can be achieved. The improved method can effectively improve the application effect of HEC-HMS, and provide a reference for the rainfall and runoff simulation in the region with insufficient data.

Abstract:Based on Zunyi City Statistical Yearbook and Zunyi City Water Resources Bulletin from 2011 to 2020, the multi-factor entropy weight method is used to determine the weight of each index system for the level of water resources carrying capacity and the level of urban economic and social development. The coupling coordination degree model of water resources carrying capacity and urban economic and social development level, which can reflect multiple factors such as society, economy, population, water quantity, water quality and so on, is established to analyze the spatial coupling and coordination relationship of water resources carrying capacity and urban economic and social development level between current urban area and planned urban area of Zunyi City. The results show that the current and planned urban areas of Zunyi City, the spatial-temporal coupling coordination degree between its water resources carrying capacity and the urban economic and social development level shows an overall upward trend from 2011 to 2020. The influence of the economic and social development level on the temporal coupling coordination degree is obvious in the current urban area, and the northward expansion of the planned urban area further strengthens the economic layout, which reduces the level of economic and social development. The coupling coordination degree with the level of urban economic and social development has obvious spatial differences in the development process and the difference is gradually narrowing with a pattern of “strong south and weak north”, indicating that the economic and social development has a high demand for water resources. In the south, the future economic layout can be gradually moved northward and eastward, and continue to implement a strict water resource management system, optimize the water resource allocation, alleviate water shortages and other problems, and ensure sustainable economic and social development.

Abstract:In order to understand the water quality variation of Hongze Lake during the transfer period of the South-to-North Water Diversion Project, the water quality monitoring data from 2013 to 2020 of Hongze Lake during the water transfer period was evaluated, and the evaluation results were analyzed by the Daniel trend test for the annual change trend of water quality. The spatial interpolation was done to obtain the distribution pattern of water quality in each lake area, and the main pollution types of water quality were further analyzed by the principal component analysis. The results showed that the water quality of Hongze Lake from 2013 to 2020 during the transfer period was mainly qualified and lightly polluted, with TP and TN as the main exceedance factors. The water quality tended to improve over time and spatially, the water quality in the overwater area was the worst, but there was a trend of turning better, while the Chengzihu area and the Lihewa area became deteriorated. The pollution type was mainly eutrophication pollution, and the nitrogen and phosphorus nutrients had a greater impact. The main sources affecting water quality were the discharge of pollutants from river inputs into the lake and the increase of construction land that is caused by human activities, but also accompanied by occasional pollution accidents. At the same time, in time Hongze Lake showed an improvement trend to the East Line water transmission of the comprehensive water quality, it is recommended to further strengthen the relevant pollution prevention work to protect the water environment of Hongze Lake and to protect the safety of the water quality of the east line of the South-to-North Water Diversion Project water transmission.

Abstract:To analyze the influence of the water temperature change in the lower reaches of Jinsha River on the spawning period of typical fishes before and after the completion of the Xiangjiaba Dam, the interannual water temperature trend and the variation range in recent years are analyzed and studied based on the measured data; and then the suitable water temperature range of 14 typical fish species in the historical spawning period is projected to the change curve of current water temperature, so as to obtain the variation of spawning period. The influence of water temperature change on the spawning activity is quantitatively evaluated by the proposed index of time overlap. The results show that the rise period of temperature in the lower reaches of Jinsha River before the dam construction is from February to June, and the annual variation range is 11.8 to 23.2℃. After the dam is built, it is postponed to April-July, with the variation range of 14.0 to 23.1℃, and the temperature fluctuations show a decreasing trend. Under the water temperature condition after the dam construction, the main spawning period of typical fishes in the lower reaches may move from early March-late July to late March-early August.

Abstract:In view of the defect that the traditional safety evaluation method of aqueduct ignores the dynamic change of index weight and cannot reflect the impact of danger factors on the actual operating state of aqueduct in real time, a comprehensive evaluation method of aqueduct safety based on the dynamic weight-cloud model is proposed, in which the dynamic weight model is introduced to dynamically weight the evaluation index, and the cloud model is used to obtain the membership degree of evaluation index. This method was applied to the safety evaluation of the M River aqueduct in the middle line of the South-to-North Water Diversion Project and compared with the research results of static weight model. The results showed that the dynamic weight model realized that the calculation result of the weight of evaluation index layer changed in real time with the project operation state, and at the same time had a higher sensitivity to the identification of risk factors, which improved the applicability and accuracy of the evaluation method for the comprehensive evaluation of aqueduct safety under complex operating environments.

Abstract:To reflect the dilatancy behavior of the coarse-grained materials, the dilatancy equation in the form of the fourth power function was introduced to modify the basic hhu-SH model that is an elastoplastic constitutive model of coarse grains based on the mesoscopic structure. In addition, the yield function, hardening parameter, derivation process of initial elastic modulus, and parameter determination method in the modified hhu-SH model were given. Relying on the concrete-faced rockfill dam (CRFD) in a pumped storage power station, the parameters of the modified hhu-SH model for different coarse-grained materials were determined by using the results of CD triaxial tests and isotropic compression tests. Then, the numerical simulation was conducted to study the stress and deformation of CRFD under the action of filling and impounding. Meanwhile, the calculated results were compared with those by using Duncan E-B model and Shen’s elastoplastic model. It shows that the results obtained from modified hhu-SH model are similar to those of Duncan’s E-B model and Shen’s elastoplastic model in the respect of the distribution of dam deformation, which validates the applicability of the modified hhu-SH model. However, from a quantitative perspective, the deformation of dam, deformation and stress of the concrete-slab, and displacement of the joints calculated by the modified hhu-SH model were smaller than that by Duncan’s E-B model generally, while closer to that of Shen’s elastoplastic model. Furthermore, the stress of the concrete-slab along the slope is the compression stress generally, which is consistent with the monitoring.

Abstract:In view of the complexity of deformation analysis and prediction for the concrete dam, a deformation analysis and prediction method of concrete dam based on SSA-LSTM-GF is proposed by using the idea of phase space reconstruction and fusion modeling. Firstly, the measured data sequence of deformation is decomposed into the trend component, the periodic component and the remaining component by singular spectrum analysis (SSA), and the remaining component is removed as noise; then, long short-term memory (LSTM) model and Gaussian fitting (GF) algorithm are used to analyze and predict the periodic component and the trend component respectively; finally, the two results are reconstructed to obtain the final prediction results. The example analysis shows that SSA can achieve good data decomposition and denoising effect; LSTM model has superior prediction performance for periodic components; GF algorithm can well realize the fitting and prediction of trend components and the mining and extraction of some information; the reconstruction effect of the results of LSTM model and GF algorithm is good. In conclusion, the deformation analysis and prediction method based on SSA-LSTM-GF has certain feasibility and research application value.

Abstract:Taking the YD002 borehole in Tongzhou Bay area of Jiangsu Province as the research object, this paper establishes a DFOS (distributed fiber optic sensing) system of land subsidence to monitor the deformation and subsidence of Quaternary sedimentary layer in this area for a long time. Based on the monitoring data, the current situation and trend of land subsidence in this area are studied and analyzed. The results show that the main deformation source in this area is the compression deformation of the soil layer caused by the vertical water release of the confined aquifer group in the upper part of the main pumping layer. The whole stratum shows a compression trend, and the deformation of each compression layer is closely related to the variation law of groundwater level. Compared with the traditional layer-wise mark, the DFOS technology can more finely measure the vertical compression and rebound deformation of soil layer.

Abstract:In order to study the effect of floodplain on the flow characteristics and pollutant transport of river confluence, a three-dimensional hydrodynamic and pollutant coupled numerical model is established to simulate and analyze the effects of floodplain with different heights and widths on the flow structure and transverse mixing characteristics of pollutants in the confluence in this study. The results show that the vertical momentum redistribution of the lateral inflow, which is caused by the floodplain, has a significant influence on the structure of the twin-helical flow, the transverse advection range of pollutants, and the position, morphological characteristics and width of the mixing layer. The intensity and range of the secondary flow increase with the increase of floodplain height. The widening of the floodplain makes the secondary flow deviate from the left bank and its intensity increases. In addition, the mixing degree of pollutant is closely related to the secondary flow, i.e., theintensity, location and range of secondary flow;the higher intensity, the largerrange and the closerpositionto the mixing layer can result in the faster the material mixing rate.

Abstract:A quasi-integrated numerical model for the vertical slot fishway was established to investigate the allowable maximum water depth difference between the fishway inlet and outlet, particularly when the fishway is subject to insufficient inlet water depth. The mathematical model was used to numerically simulate the flow velocity, flow pattern and water surface line along the fishway. The results suggest that when the water depth at the inlet is insufficient, the water depth in the upstream section is consistent with that of the outlet, and the flow velocity is stable. The water depth in the middle section begins to drop slowly, and the flow velocity gradually increases. The water depth in the downstream section decreases sharply, and the flow velocity increases rapidly. There is a drop at the inlet and the maximum flow velocity is observed. It indicates that the outlet depth has a linear relationship with the allowable maximum water depth difference between inlet and outlet, i.e., the greater the outlet depth, the greater the allowable maximum water depth difference between inlet and outlet. The results also demonstrate that there is a linear relationship between the fishway slope and the allowable maximum water depth difference between inlet and outlet, which is that a steeper slope corresponds with a smaller the allowable maximum water depth difference between inlet and outlet.

Abstract:To explore the phenomena of early peak arrival and trailing of non-Fickian migration, the solute migration experiment of a rough single fracture is carried out, the solute migration characteristics and migration mechanism in the rough single fracture are summarized, and the phenomena of early peak arrival and trailing are analyzed and explained in combination with the boundary layer theory. The results show that there is a good linear correlation between the peak arrival time, the trailing time and the thickness of the boundary layer; The boundary layer has a significant effect on the solute transport in fractured media, that is, the smaller the flow velocity is, the greater the thickness of the boundary layer is, the more solutes remain in the boundary layer, and the lower the solute acquisition rate is; the peak advance and trailing of solute penetration curve in the rough single fracture are caused by the joint action of the main flow area dominated by the inertial force in the fracture center and the boundary layer area dominated by the viscous force on the fracture wall. Among them, the peak arrival time is mainly controlled by the convection factor in the main flow area and the existence of the boundary layer area has a great influence on the trailing time.

Abstract:A particle image velocimetry (PIV) technique with the adaptation of multi time-interval was used to measure the flow field of vertical round jet in still water and cross-flow environments. The reliability of measurement results of the multi time-interval PIV technique was compared and analyzed, and the motion characteristics of the vertical round jet were studied. The results show that the measurement results obtained by the multi time-interval PIV technique can accurately reflect the time-averaged and turbulent characteristics of the jet in still water and cross-flow environments, and its accuracy is significantly better than that of the traditional PIV technique. This study found that the multi time-interval PIV technique can conveniently and accurately measure the flow field with large velocity variation in the viewing window.

Abstract:In order to investigate the effects of elasticity and plasticity on the stress-strain characteristics of cement sand and gravel (CSG) and to establish the dilatancy equation, a series of triaxial compression tests, isotropic loading and unloading tests, and triaxial loading and unloading tests of CSG materials with different cement contents under different confining pressures were carried out to systematically study the dilatancy characteristics, by means of the research method for the dilatancy characteristics of coarse-grained soil or rockfill. The results show that, both elastic and plastic strains cannot be ignored during the loading of CSG, and the CSG shows the dilatancy under the low confining pressure, while the dilatancy transits to the shrinkage with the increase of confining pressure. The elastomer strain and elastic shear strain of CSG were obtained by test data and dilatancy characteristic curves of CSG materials with and without considering elastic strain were also compared. The study reveals that the elastic strain of CSG has a greater influence on the dilatancy, and only with the high cement content and under the high confining pressure, the influence of elastic strain can be ignored. Finally, the quadratic function can well describe the dilatancy characteristics of CSG.

Abstract:Based on the construction advantages of dry connection mode of precast shear wall with high-strength bolts, steel plates and other components, a new type of prefabricated shear wall with the function of friction energy dissipation was proposed. Three shear wall specimens with the scale ratio of 1.54 were designed, and the control parameters were the axial compression ratio and the longitudinal reinforcement ratio of edge components. The quasi-static tests were carried out and the results show that the final failure mode of the three specimens are similar, which is the bending-shear failure that diagonal cracks in the wall develop to the concrete spalling in the compression area. The reduction of axial compression ratio or longitudinal reinforcement ratio of edge components have adverse effects on the seismic performance of the new prefabricated shear wall, which is manifested in the weakening of hysteretic performance and the reduction of ultimate bearing capacity. Combined with the finite element analysis results, the five-fold skeleton model and restoring force model of the new prefabricated shear wall were established. The proposed restoring force model is in good agreement with the test results, which can provide reference for the elasto-plastic seismic response analysis of the new prefabricated shear wall.

Abstract:According to the characteristics of long-period ground motions (GMs), 139 long-period GM records are selected to study the influence of structural dynamic parameters and long-period GM characteristics on the inelastic response spectra of long-period GMs. The following conclusions are obtained: compared with conventional GMs, the influence of the restoring force model and the post-yield stiffness ratio ( η ) on the spectral values of the medium- and long- periods of inelastic response spectra is larger, and the amplification effect of site soil on the inelastic response spectra is more significant; on the contrary, the effects of damping ratio ( ξ ) and displacement ductility ratio ( μ ) on the inelastic response spectra of conventional and long-period GMs are similar. Therefore, when establishing the design spectra of long-period GMs, it is necessary to select a reasonable restoring force model and η , while the existing influence law of ξ and μ on the conventional GM response spectra can be referred to, and the corresponding design spectra should be established according to different types of site soil; moreover, the design spectra of long-period GMs of a standard fortification intensity can be established first, and then the design spectra of other fortification intensities can be adjusted by the ratio of PGAfortification and PGAstandard.

Abstract:A method of standard syntaxis of the flood control and drainage based on the theory of water level safety margin is constructed, and the northern part of the Taihu Lake Basin is used as the study area to analyze the cohesion between the sub-basin flood and urban drainage standards. Through the trial calculation of different simulation schemes, the effect of changes of sub-basin flood and urban drainage standards on the inflow and outflow volume in key sections is analyzed, and the design combination of sub-basin flood and urban drainage standards is proposed based on the evaluation method of water level safety margin. The results indicate that the current sub-basin flood and urban drainage standards of the northern part of the Taihu Lake Basin basically can resist the flood with a return period of 50-year. However, the capacity and demand of flood control and drainage at the sub-basin and urban are incohesion, which shows that the water level in the urban is far lower than the flood control design water level, while the sub-basin water level is close to or even higher than the flood control design water level and even slightly higher than its flood control capacity. There are significant differences in the characteristics of changes in the flood discharge pattern caused by the improvement of flood control standards in different sub-basins. The flood control capacity of Wuchengxiyu District and Yangchengdianmao District is improved by expanding the flood discharge to the Yangtze River, while the Huxi District is profited by expanding flood discharge to the Taihu. Limiting the discharge volume of polder of urban has limited effect on alleviating the flood control pressure in the external area of urban. Finally, the sub-basin flood standard with a return period of 50-year and the urban drainage standard with a return period of 20-year in the north of Taihu Lake Basin are the design combination of standard syntaxis.

Abstract:Whether the assumption of the same frequency of storm and flood is true or not and the probability distribution of encountering the storm and flood are the basis for the design flood calculation of small and medium-sized basins. To validate the rationality, based on the hourly rainstorm and flood observation data from 1967 to 2013 in the typical heavy rainfall basin of Caojiang River in the upper reaches of Jianjiang River, this paper firstly analyzes the marginal distribution of the maximum surface rainfall and the maximum flood peak discharge, then analyzes the encounter probability of the joint distribution of rainstorm and flood peak, and calculates the design recurrence level. The main conclusions are as follows: the probability of the same frequency of rainstorm and flood is small in this basin; for a specific design frequency, the encounter probability of flood peak discharge and watershed surface rainfall increases with the increment of watershed surface rainfall; the encounter probabilities of rainfall and flood peak flow show that there are many management options for flood risk; compared with the ‘OR’ return period and the ‘AND’ return period, the secondary return period more accurately reflects the risk rate of R-Q combination.

Abstract:In order to dispatch the excessive extreme flood and ensure the flood control safety, the early warning model for water areas exceeding the alarming and guaranteed level based on the coupled hydrology and hydrodynamic models, and the rapid assessment model of flood risk based on the hydrological method. The models and the system were intelligently interacted in the forecasting and dispatching integration system of the Taihu Lake Basin, to realize the visualization of forecasting and scheduling results. Based on the National Water One Map System, the dynamic demonstration of water exceeding the alarming and guaranteed level, with the risk assessments of flood inundation, achieved the product breakthroughs from station forecasting to area prediction, from conventional forecasting to impacting prediction, as well as the flood risk from static evaluation to real time dynamic assessment. The system has been applied in resisting the 2020 major flood in the Taihu Lake Basin. The results showed that 39 risk reminders of water exceeding the alarming and guaranteed level, as well as 4 risk assessments of flood inundation, were released by the Bureau of Hydrology Information Center of Taihu Lake Basin Authority. The forecasting results were consistent with the observation, provided technical support for the dispatching, and avoided more than 30 thousand people evacuation in Suzhou city of Jiangsu Province, which guaranted the safety of flood control in the Taihu Lake Basin.