In order to provide references for landslide hazard prevention and research on the sensitivity of landslide-causing factors, the Longyangxia-Jishixia section of the upper Yellow River basin was selected as the study area, and 16 factors such as elevation, slope, terrain roughness and lithology were taken as typical landslide hazard factors. The collinearity test was carried out by Spearman correlation coefficient method to select landslide hazard factors with strong correlation. GIS was used to reclassify landslide disaster-causing factors and analyze their weights with geographic detectors. The geographic detection model results were coupled with random forest model to obtain landslide prediction probabilities under different causative factors. ROC curve was used to verify the accuracy of prediction results. The results indicate that a）the explanatory power of the interaction between causative factors is greater than that of individual factors, with the synergistic effect of elevation and other topographic parameters being particularly significant. b）The importance of drainage density, topographic roughness, and profile curvature is nearly zero, suggesting that these features may not have a direct or significant correlation with landslide occurrence. c）There are notable differences in the contribution of causative factors to the prediction results, with the elevation-slope combination being the core driving unit for landslide development in the study area. d）The AUC value ofrandom forest model has achieved 0.93, indicating strong classification performance.

Ecological protection and highquality development of the Yellow River basin has become a major national strategy. From the perspective of ecosystem protection and river health maintenance, this paper analyzed and evaluated the effect of ecological management in the lower Yellow River. The results show that the ecological base flow, the ecological flow in the sensitive period, the functional maintenance of the ecological corridor and the wetland ecological flow in the important sections of the lower reaches are fully satisfied. Compared with the period of 2009-2010, the number of fish species detected in Henan section and Shandong section has been increased by 16 and 12 respectively. The wetland area of the downstream river has been increased by 7.2% compared with that of 2019. The representative wetland area of reed marsh in estuarine area reaches to 17,300 hectares, exceeding the level of 14,000 hectares when the nature reserve was established in the early 1990s, playing an important role in the protection and restoration of the ecosystem of the lower reaches and the Yellow River delta. At the same time, it also points out that ecological protection and restoration are a longterm process and puts forward some suggestions on deepening ecological regulation in the lower reaches of the Yellow River and strengthening effect evaluation.

针对我国黄河三角洲和长江三角洲海岸线的侵蚀现状,分析了我国海岸线侵蚀主要因素:河流泥沙的减少;海平面的上升或海洋动力因素的增强以及人为因素的影响.对目前我国所采用的海岸防护措施进行了分析,指出应根据海岸侵蚀的具体特点采用不同的措施或多种形式组合,因势利导,使工程达到最好的防护效果.

The Shandong reach of the Yellow River was measured as the research area in this study. Based on the results of analyzing the temporal and spatial differences of monthly surveillance data of five monitoring sites from 2015 to 2017 according to the analysis of variance (ANOVA), 180 samples were divided into 12 groups by hierarchical cluster analysis. Using the sample mean of each group as the input, the comprehensive water quality identification index of each group was calculated. The results show that the comprehensive water quality of the Shandong reach of the Yellow River is in good condition and the comprehensive water quality of the sampling sections is at class I to class Ⅱ levels. The comprehensive water quality condition has an upwarding trend from 2015 to 2017. The comprehensive water quality of Lijin section is the worst among five monitoring sites and from upstream to downstream, the comprehensive water quality has an upwarding trend except Lijin section.

Concrete face rockfill dams (CFRDs) are widely utilized in water conservancy and hydropower engineering due to their excellent durability, strong impermeability, and cost-effectiveness. However, their seismic safety during service has raised significant concerns. In this study, a concrete face rockfill dam located on the upper reaches of the Yellow River was selected as the research object. Based on the structural characteristics of the dam and geological conditions, a three-dimensional numerical model was established to simulate the dam’s dynamic response under seismic action by integrating the Duncan-Chang model and the concrete damage plasticity constitutive model. Through this model, the dynamic responses of the dam under varying seismic intensities were analyzed, revealing the evolution of stress distribution and structural deformation characteristics. The results indicate that the critical zones prone to transverse damage under seismic action are located at two-fifths of the total height of the concrete face and the toe slab. Furthermore, based on the computational results, the correlation between failure variables and structural damage patterns under seismic action was investigated, and vulnerability curves under different seismic intensity levels were plotted. The findings demonstrate that with the increase of  seismic intensity, the vulnerability curves shows a rightward shift trend, and the failure probability of the dam body rises significantly.

对于荷载引起的混凝土裂缝,世界各国规范计算公式和方法各不相同,计算公式中荷载取值也各不相同.在参考国外裂缝宽度控制措施的基础上,探讨了我国混凝土结构设计规范中钢筋混凝土构件裂缝宽度计算中荷载取值问题,指出:长期作用在结构上并对裂缝有长期影响的是考虑可变荷载准永久值组合的荷载长期效应组合;对HRB500级钢筋混凝土构件裂缝宽度进行计算时,建议采用可变荷载准永久值组合的荷载长期效应组合进行计算.

根据水泥土搅拌桩的现场静载试验,测量了桩的轴向应变,计算了桩身轴力、桩侧摩阻力,分析了桩的荷载传递特性.结果表明:水泥土搅拌桩表现出摩擦桩的特性;荷载主要在一定的范围内传递,桩的轴力和侧摩阻力在桩体上部的衰减较快;主要在桩顶处发生横向拉裂破坏;桩体破坏前后荷载的传递机理是不同的.

The evaluation of management level and trend of irrigation area are of important for improving the management of irrigation area and for enhancing the use efficiency of water saving transformation project fund. This paper had established a system dynamics model on management of irri-gation area. This model could dynamically simulate the financial and engineering situation of irrigation area and their impacts on the area,grain yield and planting income of famers. The model was used to simulate the management situation of Yongsuyu irrigation area in Jilin Province. It was proved that this model could dynamically simulate the management situation of irrigation area and its impact well. The result shows that Yongsuyu irrigation area is managed well at present. It is estimated that the irrigation area,grain yield and planting income of famers of this irrigation area will be greatly increased during the period of 2010-2020.

Parameter calibration is the essential step for successful application of hydrologic models. The PEST,based on Levenberg-Marquardt,a nonlinear and automatic method to calibrate hydrologic models,has been widely used in many basins successfully. Guishui River,located at north-west of Beijing and faced with scarce water resources,is selected as the study area. The years of 2005-2006 and 2007-2008 were selected as cal-ibration year and validation year respectively. Manual calibration and automatic calibration were used simultaneously in the paper. First,the suit-able initial values of parameter were selected as the order of yearly runoff,monthly runoff and flow hydrographs by manual calibration. Then param-eter sensitivity and 95% confidence limits were analyzed with PEST and all the estimated values of parameters were within the limits indicated the result was reliable. Goodness-of-fit of the PEST calibration model uses the Nash-Sutcliffe coefficient (E)and coefficient of determination (R2 ). Statistical comparisons between simulated data and observed date for the calibration year give a reasonable agreement with E equal to 0. 640 and R2 equal to 0. 787 though the data of 0. 338 and 0. 612 by manual calibration. These values are respectively 0. 737 and 0. 859 for validation year. O-verall,PEST is a reasonable method and HSPF model has the good applicability on the Guishui River basin.

CCPM在单个项目管理中的应用主要包括关键链识别、缓冲区管理和缓冲时间设置等.关键链在工程项目群管理中应用时,包括设定各项目的优先权、对单个项目进行计划、避免交错项目资源冲突、对缓冲区进行有效地管理等步骤.应用CCPM方法和大型计划软件P3对某大型供水工程项目群管理表明:CCPM方法减少了学生综合征和帕金森定律的产生,提高了管理效率;把P3软件和CCPM计划方法结合在一起,减少了利用P3软件计划时的不确定性,也克服了CCPM方法在多项目管理应用中的局限性.

According to the analysis of the water resources development and protection, water pollution control, water ecological restoration, water landscape construction and water management of Nansi Lake area, a water ecological civilization evaluation index system and a comprehensive evaluation method were established on the basis of SWOT analysis of internal environment factors and external conditions. The evaluation index system and comprehensive evaluation method were applied to evaluate the water ecological civilization level of Zhuzhaoxin River basin. The evaluation result coincides with the basin’s present circumstances, which indicates that the evaluation index system and comprehensive evaluation method can correctly identify the main problem in the construction of water ecological civilization of Nansi Lake basin.

Based on the construction practice of TBM which is used in the Qinling tunnel of Water Diversion Project from Hanjiang to Weihe River, we compared the tunneling efficiency of the two TBMs in Lingnan and Lingbei under completely different geological conditions. It was considered that the tunneling efficiency of TBM was not rigorously judged by the types of surrounding rock. Actual research shows that the lithology of surrounding rock especially the geological factors of compressive strength, the integrity and groundwater of the surrounding rock are the main geological factors that affect the efficiency of excavation. Based on this, we explored the progress indicators of TBM in complex geological environment and the geological adaptability of TBM.

Higher requirements for the protection and management of the Yellow River were put forward, and also new opportunities for the development were provided in the Yellow River Basin following the established strategy of the ecological protection and high-quality development of Yellow River Basin. In this paper, the present situation of water security was analyzed, the connotation of high-quality development was discussed and the main problems existing in water security and high-quality development was summarized in the Yellow River Basin; then, the ideas for the water security and high-quality development of the Yellow River were discussed and the corresponding suggestions were proposed. The main problems of water security and high-quality development in the Yellow River are shortage of water resources, frequent floods and uncoordinated relationship between water and sediment, serious soil erosion and fragile water ecological environment, deficient water resources operation and regional water supply project and weak cooperative management ability of the river basin. Focusing on the issues discussed above, the ideas were put forward from six aspects including disaster prevention and mitigation, water network optimization, ecological protection and restoration, efficient use of water resources, basin management capacity and scientific support. Meanwhile, suggestions were proposed based on strategic planning promotion, development plans formulation, technological innovation and support enhance, institutional innovation exploration, ecological conservation and restoration plan boost and the rule of law promotion, which provided references for water security and high-quality development of the Yellow River.

Taking Ejina Oasis in the lower reaches of Heihe River as the research area, based on the groundwater depth observation data of different regions in the east branch and west branch of the Oasis from 1992 to 2015, the groundwater depth variation characteristics of Heihe Oasis after the Ecological Dispatching Water were analyzed. The results indicated that the groundwater level of east branch and west branch in March and April is the smallest, and that of August and September is the largest. From 1992 to 2003, the groundwater level decreases mainly. From 1999 to 2015, the groundwater level in most regions shows a rising trend, while the groundwater level in some regions does not change much or slightly decline. With the deepening of the Ecological Dispatching Water, the groundwater depth in the research area gradually tends to be stable, and after 15 years of the Ecological Dispatching Water, the downward trend of groundwater level in Ejina Oasis has been greatly curbed.

In order to investigate the influence of double polyethylene and double crosslinker material to the compressive strength characteristics of loess and analyze reinforcement mechanism, the unconfined compressive strength test was conducted to study the relations between compressive strength and admixture content, dry density, curing condition, failure strain and deformation modulus, it gave a fitting relationship of stressstrain, and analyzed the failure mode of solidified loess. The results show that when the dry density is relatively small, the strength of solidified loess increases with the increase of the admixture content and the compressive strength changes obviously. When the dry density is large, the strength of the solidified loess increases first and then decreases with the increase of the admixture content, and the compressive strength changes little. The compressive strength of solidified loess cured by drying is slightly higher than that cured by natural air drying. The failure strain of solidified loess decreases with the increase of compressive strength. It is a power relationship and gradually changes to brittleness. The deformation modulus is basically proportional to the compressive strength. The uniaxial stressstrain curve can be fitted well by the parabola. Destruction of solidified loess is closely related to the reticular membrane structure formed by the material. The reticular membrane structure makes the loess particles more closely arranged, the pore area is reduced, and the void ratio is lowered. External forces make it more difficult to destroy, which can effectively improve the strength of loess.

Modernization of water conservancy is the key to realize socialist modernization in an allround way. How to clarify the construction system and implementation route of water conservancy modernization in which man and nature coexist harmoniously is an urgent issue to be solved at present. Based on the indepth analysis of the concept of the harmonious coexistence between human and nature, this paper analyzed the need to adhere to the concept of the harmonious coexistence between human and nature in the building of water conservancy modernization, put forward the system framework of the harmonious coexistence between human and nature in the construction of water conservancy modernization and introduced its main building contents from eight aspects, such as theory, technology, engineering and service. The modernization of water conservancy was divided into three stages, namely preparation stage, rapid development stage and continuous improvement stage, and the road map of the modernization of water conservancy was drawn. It provides reference for realizing the modernization goal of harmonious coexistence between human and nature and constructing the modernization of water conservancy.

The application of resistivity tomography to detection for hidden dangers of embankment can grasp the safety status of embankment and ensure their safe operation. Electrical detection is usually based on the theory of semiinfinite space, but the section of embankment does not satisfy the condition of semiinfinite space. In order to reduce the impact of embankment terrain to the electrical method and improve the detecting precision of resistivity tomography, the paper established a trapezoidal embankment. Through changing the arrays and the distance of electrodes, the paper established a numerical simulation and model test. It is better to choose Schlumberger array in the detection of the hidden dangers. Electrode distance should not be more than 1.0 m to ensure the the detection resolution.

Aiming at the issue that it was difficult to accurately determine the index weight in the risk assessment of mountain torrent disasters in regions with small spatial scale, this paper selected Linzhou City as the research object, adopted the consequence reverse diffusion method, and selected 9 indicators from 2 aspects of natural disaster system and social disaster system to build a mountain torrent disaster risk index system. The random forest algorithm was introduced to establish the random forest risk assessment model of Linzhou City, according to different mountain torrent disaster risk levels, the mountain torrent disaster risk areas in Linzhou City were divided, and the comparison and analysis were made with the actual situation of historical mountain torrent disaster occurrence points. The results show that the classification accuracy of risk areas of the random forest risk assessment model reaches to 81.34%, which proves that the random forest algorithm has high accuracy when is applied to the risk assessment of mountain torrent disasters in areas with small spatial scales.

对2009年黄河桃汛期调水试验的基本情况进行了介绍,分析了三门峡库区相关各站洪水、库区冲淤、水库运用和试验对潼关高程及渭河口的影响.结果表明:①潼关站桃汛洪水对渭河尾闾段顶托作用明显,但未造成明显不利影响,桃汛洪水顶托引起的吊桥站水位壅高值最大为1.4 m,壅水影响最远点在渭淤2+1-3河段;②2009年桃汛期潼关高程降低约0.13 m;③增加桃汛期潼关河段流量大于1 000 m3/s的持续时间对冲刷降低潼关高程的作用较为明显.

The gullied rolling loess area is the most serious area of soil and water loss in the Loess Plateau. In order to provide basis and reference for the rational allocation of soil and water conservation forest in the gullied rolling loess area, by taking the Pinus tabulaeformis, Larix principisrupprechtii and Platycladus orientalis in Xiguoyuan watershed of Lanzhou as the research object, a systematic analysis of the relationship between soil aggregates and soil organic matter was made and the soil aggregates stability was evaluated. The results indicate that the >0.25 mm soil aggregates is the main aggregate size of Pinus tabulaeformis, Larix principisrupprechtii and Platycladus orientalis. The stability of soil aggregates is the best in Larix principisrupprechtii, then followed by Pinus tabulaeformis and Platycladus orientalis. The SOM of all stands is decreased with the increase of soil depth and which of the order is Larix principisrupprechtii >Pinus tabulaeformis >Platycladus orientalis. There is a positive correlation between Ww0.25, MWDw, GMDw and SOM, and there is a negative correlation between Wd0.25, PAD, Dw and SOM. SOM has a significant effect on the soil macroaggregate content, PAD and Dw. The stability of soil aggregate in Larix principisrupprechtii is higher than that in Pinus tabulaeformis and Platycladus orientalis and Larix principisrupprechtii can be given priority in the allocation of soil and water conservation forest in gullied rolling loess area.

This paper tried to use the vibration of a rotating equipment measurement evaluation method to accurately grasp the allowable operating boundary conditions of Xiaolangdi turbine. A low frequency displacement sensor was installed in the horizontal direction of the inlet door of the draft tube of the turbine. By measuring the horizontal vibration of draft tube, the vibration of head cover and the pressure pulsation at the lower chamber of turbine head cover, the inlet of spiral, the inlet of draft tube and the diffuse section of draft tube under different load conditions, it concluded that the variation trend of pressure pulsation and horizontal vibration of draft tube was consistent. Combining the measured data, the noise at the inlet of draft tube and the comprehensive characteristic curve of the model turbine, the running stability of the turbine was analyzed and evaluated. The consistency between the real turbine running characteristic and the comprehensive characteristic curve of the model turbine was verified accurately. It was proved that using the draft tube horizontal vibration to measure the hydraulic factors of the draft tube was the effective means for the evaluation of hydraulic vibration.

Aiming at the poor frost resistance of the sand stabilization materials, which is difficult to meet the demand of engineering construction in alpine regions, the preparation of polyurethane sand fixation material and its physical and mechanical properties under the freezethaw cycle conditions were carried out by combining the experimental study method with the theoretical analysis. In this study, samples with sandfixing agent content of 4%, 6%, 8%, 10%, 12% and 14% were prepared, and then subjected to 5, 10, 15, 20 and 25 freezethaw cycles at freezing temperature of -20 ℃ and thaw temperature of 20 ℃. Subsequently, the strength loss and mass loss of the consolidation body with different contents of sandfixing agent were measured after the freezethaw cycles. On the basis of that, the microstructure of the consolidation body was analyzed from the micro point of view by SEM, and the damage degradation mechanism of the polyurethane sand stabilization material under the freezethaw cycles was discussed. The results show that under the condition of freezethaw cycle, the compressive strength and solid mass of polyurethane sand fixation are mainly related to the concentration of sandfixing agent. Microscopic test shows that the loose grains of sand are connected by the "bridging", thus it becomes a whole of strength and toughness which can resists the damaging effects of freezethaw cycles.

Based on the precipitation data from 27 meteorological stations in Shanxi Plateau and its surrounding areas, the paper used some spatial interpolation methods to interpolate the annual average precipitation of Shanxi Plateau from 1981 to 2005. These methods included Inverse Distance Weight, Global Polynomial Interpolation, Local Polynomial Interpolation, Radial Basis Function, Spline, Trend, OrdinaryKriging and Empirical Bayesian Kriging. The precision of these methods was evaluated by using leaveoneout cross validation. Finally, it analyzed the precipitation spatial distribution of Shanxi Plateau which was obtained by the optimal method. The results show that a) among these methods, Radial Basis Function yields the best performance, whose mean absolute error is 25.1 mm, mean relative error is 5.7% and root mean squared error is 31.4 mm; b) according to the accuracy, the interpolation methods is ranked as: Radial Basis Function, Spline, Trend, Ordinary Kriging, Local Polynomial Interpolation, Global Polynomial Interpolation, Empirical Bayesian Kriging and Inverse Distance Weight and; c) the precipitation spatial distribution in Shanxi Plateau presents the regional characters, on the one hand, which shows a decreased trend from southeast to northwest, on the other hand, the precipitation of Mount Lyuliang and Mount Taihang is much more than that of the Fenhe River.

The Yellow River basin is short of water resources. In dry years, there is a sharp contradiction between water supply and demand, and a serious shortage of irrigation water. Scientific cascade reservoirs operation in the main stream of the Yellow River plays an important role in coping with drought of the Yellow River in an orderly way and improving the effect of drought resistance and disaster reduction. According to the agricultural drought situation and drought distribution in the Yellow River basin, the response relationship between incoming water of the Yellow River and agricultural drought demand in dry years was analyzed and the joint operation model of the key reservoirs in the Yellow River main stream with the minimum comprehensive water shortage as the objective was constructed. Selecting 1994 the severe drought occurred in the Yellow River basin as the typical year for operation analysis, and the schemes of water storage and replenishment for the key reservoirs in the Yellow River main stream during the flood season (July to October), the ice flood season (December to March the next year) and the peak water consumption (March to June) were put forward, the replenishment amount of key reservoirs in the main stream of the Yellow River was 3.78 billion m3 in the whole year, by identifying the importance of water supply, in key periods of crop irrigation the water supply for agricultural users was guaranteed, the degree of agricultural water shortage was reduced, the water shortage rate in the upper, middle and lower reaches of the Yellow River was basically controlled by about 25% and the drought situation in the Yellow River basin had been effectively alleviated. The results show that the water shortage in the upper, middle and lower reaches of the Yellow River can be alleviated by the joint operation of key reservoirs, the water shortage in the upper, middle and lower reaches of the Yellow River can be balanced and the drought resistance ability of the river basin can be improved.

The Lower Yellow River floodplain has an area of 3 154 km2, with 0.227 milllion hm2 of cultivated land and 1.895 2 million populations living in. Constrained by the special physiographic condition and the progress of safety construction, the economy development in the floodplain area is slow and people are still living in poor conditions. With the guidance of the national development strategy and water management policy in the new era, a reconstruction and ecological management plan of "Flood Control with Graded Standard, Sediment Depostition in Partitioned Zone, Regionalized Reconstruction and Development of Floodplain" was proposed, by summarizing the achievements in treatment of the floodplain and the characteristics and laws of flow and sediment transport in the Lower Yellow River. The reconstruction and management of the Lower Yellow River floodplain is an effective combiniation of river management and economy development, which is in accordance with the national requirement for national ecological civilization construction, and plays an important role in taking targeted measures to help people lift themselves out of poverty and promoting the development of the Central Plains Economic Zone. This paper advised to conduct studies instantly on the schemes for reconstruction and ecological management of the Lower Yellow River floodplain. Pilot projects should be launched in selected reaches firstly to conduct reconstruction experiments, and then the experience can be popularized along the entire Lower Yellow River.

The slope protection structure of stone cage net cushion is widely used in the engineering of river bank slope protection. The technical parameters of the net cushion structure have significant effects on bank slope protection, and different net cushion thicknesses, baffle spacing and gravel filling conditions will have a certain impact on its antierosion performance. Through indoor largescale sink flush test, the critical velocity was studied for stone cage mat structure with different thicknesses, different baffle distance and different contents of inferior diameter particles. The deformation process and failure rule of mat structure were revealed under different flow scouring. The antiscour performance was defined by the critical flow rate, so as to determine the optimal parameters. The results show that the inferior diameter ratio has a significant effect on the antiscour performance and it is recommended that it should not exceed 15%; when the spacing of the barriers is small, the rockfill is easy to form an overall stable structure and the movable gap between the rockfills is small. In the condition of feasible construction technology, it can improve the stability of filling stone and the antierosion performance of stone cage net cushion by reducing the partition spacing. In order to ensure the relative stability of stone filling, two layers of stone should be filled in stone cage net cushion at least. Considering the filling rate, the optimal thickness should be two times of the median particle size of filled stone.

In order to explore the win-win governance idea of the coordination and promotion of ecological protection and high-quality development of the Yellow River Basin, starting from theoretical research, issue research, empirical research and path research, this paper analyzed the problems existing in the research on ecological protection and high-quality development in the Yellow River Basin and summarized the measurement methods and implementation paths of ecological protection and high-quality development in the Yellow River Basin. It is pointed out that there are few studies on the coordinated development of the Yellow River Basin and most of them focus on the systematic study of the whole basin; There are few studies on the coordinated promotion of sustainable utilization of water resources and high-quality development; There are few innovative studies from the perspective of high-quality development in the Yellow River Basin. The research on ecological protection and high-quality development of the Yellow River Basin involves economic, cultural and ecological aspects. In the new period of economic development, promoting the coordinated development of high-quality development and ecological protection of the Yellow River Basin is an important direction of future research.

为了研究香溪河库湾水体富营养化的问题,采用数值模拟的方法分析了香溪河库湾春季水动力场的特点,并按照持续抬高和降低三峡水库水位两种工况研究了香溪河水动力场的变化.结果表明:①春季香溪河库湾水体存在着明显的分层异向流动,主要表现为表层水体由长江干流流向库湾,长江干流与库湾支流水体的交换作用明显；②水位持续下降或者持续上升的调度方式会对香溪河水动力场产生一定的影响,不仅使水体流向发生改变的位置有所变化,而且明显改变了库湾中上游水体流速,主要是表层水体流速；③水位持续下降会对水体分层流动产生抑制作用,而水位持续上升会促进水体的分层流动.

On the basis of robustness, this study had optimized closing law by automatic detailed search, and drew extreme nephograms of multivariable about break point. Favorable laws were separated from adverse closing laws significantly from nephograms, which included better robustness and adaptability of uncertain factor. Although closure law region was largely adjusted to optimize security parameters, a complex closed rule should be set to achieve better robustness when numerical method was employed to simulate the insitu case, and this situation would become worse in the pumped power station, whose flow characteristics had the Sfeature. Therefore, an optimization method based on the closure law region would reduce the errors between the numerical method result and the actual case.

The Sanmenxia area widely distributes Quaternary loess and loess soil. Through the analysis of the region of the loess particle composition, mineral composition, chemical composition and microstructure characteristics, the engineering properties of loess were analyzed. The results show that the region of composition and updated in the loess Q3 loess is basically similar, grain composition is given priority to silt, Sanmenxia area collapsible loess clay content is greater than that of the northwest region, silt content is less than that of the northwest region; Holocene loess and loess collapsibility belongs to late Pleistocene series for moderate collapsibility, strong coefficient of collapsibility of loess is from 0.020 to 0.098, the Pleistocene series loess collapsibility generally do not have.

In order to explore the inherent law of overland flow under vegetation, this paper studied on the differences of hydraulic characteristics of the overland flow between the rigid and flexible vegetation coverage. The results show that velocity increases as the increase of flow under rigid and flexible vegetation coverage; the effect of slowing flow under rigid coverage is better than that of the flexible vegetation coverage; under the coverage of rigid vegetation, the Froude number is less than 1 and it is in the slow flow state; the resistance coefficient changes with the Reynolds number and the flow rate; under the coverage of flexible vegetation, Froude number gradually increases with the increase of flow and the flow regime transforms from the slow flow to the rapids; the resistance coefficient decreases with the increasing of Reynolds number and the flow rate.

在开封惠北试验站进行清水灌溉、污水灌溉田间试验,探讨了污水灌溉对冬小麦和土壤系统的影响.结果表明:污水灌溉在冬小麦关键用水期更有利于对土壤水分的吸收;污水灌溉后对土壤有一定的重金属污染;污水灌溉对冬小麦的茎叶及子粒生长有一定的促进作用,并能提高产量.

The control of seepage stability of covering layer is one of the key technologies of building high cofferdam on deep overburden. The paper analyzed the reasons for the change of covering layer from the perspective of seepage pressure, used the method of numerical analysis of finite element, calculated and analyzed the influence of filling of underwater part of cofferdam and changes of covering layer made by channel scour to the seepage characteristics by using ABAQUS software. Project analysis shows that for a deep overburden watercourse on a complex condition, during the cofferdam construction organization, the coating thickness of cofferdam's base and its material properties parameters will be changed, the cover layer's seepage characteristics vary with its thickness and material properties. Seepage pressure characteristic values show an increasing trend, which matches the actual situation.

Based on monthly monitoring data of cross-sectional sampling points laid on watershed scale and taking Xiaohe River basin as an exam-ple,this paper studied on the basin scale inland spatial variation characteristics of water and river basin water self-purification ability. The results show that the water quality of the main flow Songta River is good,belonging to gradeⅢ;the water quality of tributary Baima River is poor,belong-ing to the worse gradeⅤ,which is the main factor of influencing the Xiaohe River basin water quality. Local sewage and industrial waste water of untreated water pollution discharging are the main reasons of causing water pollution of Xiaohe River basin. Judging from the spatial scale,the con-tents of CODCr ,NH3 -N and TP generally show a gradual decreasing trend from upstream to downstream along the river,which indicates that the Xiaohe River water has certain self-purification ability,but very poor. Exponential relationship exists between the slope of the water purification ca-pacity and hydraulic slope.

In order to understand the distribution of heavy metal pollution in bottom mud and reveal the pollution sources in the middle reaches of the Fenhe River, the section of the river from the inlet of Ciyao River to the 2 km below the inlet of Wenyu River was selected as the research object, a total of 35 sediment samples (sediment depth 0-70 cm) were collected from 5 sections. It analyzed its vertical distribution characteristics along the river channel and revealed the source of pollution by using principal component analysis (PCA) and positive definite matrix factor analysis (PMF). The results show that the heavy metals (Hg, Cu, Pb, Cr and Ni) in the sediment of the middle reaches of the Fenhe River are generally enriched at a depth of 40-70 cm, the content at 40-70 cm depth is 1.02-2.82 times that at 0-40 cm depth and its vertical distribution may be related to the history of local industrial pollution. By analyzing the distribution characteristics and sources of sediment from 0 to 40 cm deep along the river course, it is found that the distribution trend of the five heavy metals is similar along the river course, and the content of the five heavy metals appears large values at the inlet of Ciyao River into Fenhe and the inlet of Wenyu River into Fenhe. The content of Pb and Hg exceeds the standard seriously, which are 1.94 and 3.91 times of the local soil background value respectively, and the maximum value appears at the inlet of Wenyu River into Fenhe River. Heavy metals Pb, Cr and Ni are mainly from industrial production, Cu is mainly from industrial production and partly from algae accumulation and Hg is mainly from algae accumulation and partly from industrial production.

The paper studied the characteristics of break-up date in the Toudaoguai Hydrological Station of the Yellow River by the K-Means cluster algorithm and the Mann-Kendall examination methods according to the measured ice data since 1950. The results show that: a)the break-up date in the station has the trend in advance, which is more prominent after 2000; b)the break-up dates since 1950 can be sorted 3 classes by March 16th and March 24th, which are earlier break-up, common break-up, and later break-up, and the earlier break-up years increased rapidly; c)from 1988 to 1995 can be used as the transitional period of the break-up date changed from later to earlier, and the year of 1992 is the mutational point; d)the temperature is the main influencing factor of the break-up date, the trend in advance of the break-up date keep consistent pace with the temperature warming in the area after 1988.

The traditional slope stability analysis method cannot consider the effect of precipitation. Based on the basic theory of Sweden slice method, using the alternative methods of gravity, the equation which could consider the precipitation effect had been induced. Based on this, taken an earth embankment in Chenggu Country of Hanzhong City as an example, the effect of precipitation intensity and slope ratio on the safety factor had been analyzed. In addition, the fitting relation of precipitation intensity and slope ratio vs safety factor had been induced. Finally, the effect of slope ratio on safety factor under different precipitation had been analyzed and also the suggestion that considering the rainfall intensity effect during the earthwork construction had been recommended.