Variations in glacier volume and snow cover and their impact on lake storage in the Paiku Co Basin,in the Central Himalayas     

Xingxing Zhang  Rui Wang  Zhijun Yao  Zhaofei Liu 《水文研究》2020,34(8):1920-1933

Glaciers and snow cover are important constituents of the surface of the Tibetan Plateau. The responses of these phenomena to global environmental changes are sensitive, rapid and intensive due to the high altitudes and arid cold climate of the Tibetan Plateau. Based on multisource remote sensing data, including Landsat images, MOD10A2 snow product, ICESat, Cryosat-2 altimetry data and long-term ground climate observations, we analysed the dynamic changes of glaciers, snow melting and lake in the Paiku Co basin using extraction methods for glaciers and lake, the degree-day model and the ice and lake volume method. The interaction among the climate, ice-snow and the hydrological elements in Paiku Co is revealed. From 2000 to 2018, the basin tended to be drier, and rainfall decreased at a rate of −3.07 mm/a. The seasonal temperature difference in the basin increased, the maximum temperature increased at a rate of 0.02°C/a and the minimum temperature decreased at a rate of −0.06°C/a, which accelerated the melting from glaciers and snow at rates of 0.55 × 10⁷ m³/a and 0.29 × 10⁷ m³/a, respectively. The rate of contribution to the lake from rainfall, snow and glacier melted water was 55.6, 27.7 and 16.7%, respectively. In the past 18 years, the warmer and drier climate has caused the lake to shrink. The water level of the lake continued to decline at a rate of −0.02 m/a, and the lake water volume decreased by 4.85 × 10⁸ m³ at a rate of −0.27 × 10⁸ m³/a from 2000 to 2018. This evaluation is important for understanding how the snow and ice melting in the central Himalayas affect the regional water cycle.  相似文献   

A novel coupled FDM-DEM modelling method for flexible membrane boundary in laboratory tests     

Hua-Xiang Zhu  Zhen-Yu Yin  Qiang Zhang 《国际地质力学数值与分析法杂志》2020,44(3):389-404

Difficulties are involved in discrete element method (DEM) modelling of the flexible boundary, that is, the membranes covering the soil sample, which can be commonly found in contemporary laboratory soil tests. In this paper, a novel method is proposed wherein the finite difference method (FDM) and DEM are coupled to simulate the rubber membrane and soil body, respectively. Numerical plane strain and triaxial tests, served by the flexible membrane, are implemented and analysed later. The effect of the membrane modulus on the measurement accuracy is considered, with analytical formulae derived to judge the significance of this effect. Based on an analysis of stress-strain responses and the grain rotation field, the mechanical performances produced by the flexible and rigid lateral boundaries are compared for the plane strain test. The results show that (1) the effect of the membrane on the test result becomes more significant at larger strain level because the membrane applies additional lateral confining pressure to the soil body; (2) the tested models reproduce typical stress and volumetric paths for specimens with shear bands; (3) for the plane strain test, the rigid lateral boundary derives a much higher peak strength and larger bulk dilatation, but a similar residual strength, compared with the flexible boundary. The latter produces a more uniform (or ‘diffuse') rotation field and more mobilised local kinematics than does the former. All simulations show that the proposed FDM-DEM coupling method is able to simulate laboratory tests with a flexible boundary membrane.  相似文献   

Hydrological management strategies for the control of algal blooms in regulated lowland rivers     

Jian Li  Wei Yin  Haiyan Jia  Xiaokang Xin 《水文研究》2021,35(6):e14171

Reservoirs of lowland floodplain rivers with eutrophic backgrounds cause variations in the hydrological and hydraulic conditions of estuaries and low-dam reservoir areas, which can promote planktonic algae to proliferate and algal bloom outbreaks. Understanding the ecological effects of variations in hydrological and hydraulic processes in lowland rivers is important for algal bloom control. In this study, the middle and lower reaches of the Han River, China, a typical regulated lowland river with a eutrophic background, are selected. Based on the effect of hydrological and hydraulic variability on algal blooms, a hydrological management strategy for river algal bloom control is proposed. The results showed that (a) differences in river morphology and background nutrient levels cause significant differences in the critical threshold flow velocities for algal bloom outbreaks between natural river and low-dam reservoir sections; there is no uniform threshold flow velocity for algal bloom control. (b) There are significant differences in the river hydrological/hydraulic conditions between years with and without algal blooms. The average river flow, water level and velocity in years with algal blooms are significantly lower than those in years without algal blooms. (c) For different river sections where algal blooms occur and to meet the threshold flow velocities, the joint operation of cascade reservoirs and diversion projects is an effective method to prevent and control algal blooms in regulated lowland rivers. This study is expected to deepen our understanding of the ecological significance of special hydrological processes and guide algal bloom management in regulated lowland rivers.  相似文献   

Implementation of a coupled plastic damage distinct lattice spring model for dynamic crack propagation in geomaterials          下载免费PDF全文

Chao Jiang  Gao‐Feng Zhao 《国际地质力学数值与分析法杂志》2018,42(4):674-693

This paper studies dynamic crack propagation by employing the distinct lattice spring model (DLSM) and 3‐dimensional (3D) printing technique. A damage‐plasticity model was developed and implemented in a 2D DLSM. Applicability of the damage‐plasticity DLSM was verified against analytical elastic solutions and experimental results for crack propagation. As a physical analogy, dynamic fracturing tests were conducted on 3D printed specimens using the split Hopkinson pressure bar. The dynamic stress intensity factors were recorded, and crack paths were captured by a high‐speed camera. A parametric study was conducted to find the influences of the parameters on cracking behaviors, including initial and peak fracture toughness, crack speed, and crack patterns. Finally, selection of parameters for the damage‐plasticity model was determined through the comparison of numerical predictions and the experimentally observed cracking features.  相似文献   

Assessment of alternative adsorption models and global sensitivity analysis to characterize hexavalent chromium loss from soil to surface runoff          下载免费PDF全文

Chuan‐An Xia  Juxiu Tong  Bill X. Hu  Xiujie Wu  Alberto Guadagnini 《水文研究》2018,32(20):3140-3157

We investigate our ability to assess transfer of hexavalent chromium, Cr(VI), from the soil to surface runoff by considering the effect of coupling diverse adsorption models with a two‐layer solute transfer model. Our analyses are grounded on a set of two experiments associated with soils characterized by diverse particle size distributions. Our study is motivated by the observation that Cr(VI) is receiving much attention for the assessment of environmental risks due to its high solubility, mobility, and toxicological significance. Adsorption of Cr(VI) is considered to be at equilibrium in the mixing layer under our experimental conditions. Four adsorption models, that is, the Langmuir, Freundlich, Temkin, and linear models, constitute our set of alternative (competing) mathematical formulations. Experimental results reveal that the soil samples characterized by the finest grain sizes are associated with the highest release of Cr(VI) to runoff. We compare the relative abilities of the four models to interpret experimental results through maximum likelihood model calibration and four model identification criteria (i.e., the Akaike information criteria [AIC and AIC_C] and the Bayesian and Kashyap information criteria). Our study results enable us to rank the tested models on the basis of a set of posterior weights assigned to each of them. A classical variance‐based global sensitivity analysis is then performed to assess the relative importance of the uncertain parameters associated with each of the models considered, within subregions of the parameter space. In this context, the modelling strategy resulting from coupling the Langmuir isotherm with a two‐layer solute transfer model is then evaluated as the most skilful for the overall interpretation of both sets of experiments. Our results document that (a) the depth of the mixing layer is the most influential factor for all models tested, with the exception of the Freundlich isotherm, and (b) the total sensitivity of the adsorption parameters varies in time, with a trend to increase as time progresses for all of the models. These results suggest that adsorption has a significant effect on the uncertainty associated with the release of Cr(VI) from the soil to the surface runoff component.  相似文献   

Study of the flood control scheduling scheme for the Three Gorges Reservoir in a catastrophic flood          下载免费PDF全文

Shanghong Zhang  Zhu Jing  Wenda Li  Yujun Yi  Yong Zhao 《水文研究》2018,32(11):1625-1634

The Three Gorges Project is the world's largest water conservancy project. According to the design standards for the 1,000‐year flood, flood diversion areas in the Jingjiang reach of the Yangtze River must be utilized to ensure the safety of the Jingjiang area and the city of Wuhan. However, once these areas are used, the economic and life loss in these areas may be very great. Therefore, it is vital to reduce this loss by developing a scheme that reduces the use of the flood diversion areas through flood regulation by the Three Gorges Reservoir (TGR), under the premise of ensuring the safety of the Three Gorges Dam. For a 1,000‐year flood on the basis of a highly destructive flood in 1954, this paper evaluates scheduling schemes in which flood diversion areas are or are not used. The schemes are simulated based on 2.5‐m resolution reservoir topography and an optimized model of dynamic capacity flood regulation. The simulation results show the following. (a) In accord with the normal flood‐control regulation discharge, the maximum water level above the dam should be not more than 175 m, which ensures the safety of the dam and reservoir area. However, it is necessary to utilize the flood diversion areas within the Jingjiang area, and flood discharge can reach 2.81 billion m³. (b) In the case of relying on the TGR to impound floodwaters independently rather than using the flood diversion areas, the maximum water level above the dam reaches 177.35 m, which is less than the flood check level of 180.4 m to ensure the safety of the Three Gorges Dam. The average increase of the TGR water level in the Chongqing area is not more than 0.11 m, which indicates no significant effect on the upstream reservoir area. Comparing the various scheduling schemes, when the flood diversion areas are not used, it is believed that the TGR can execute safe flood control for a 1,000‐year flood, thereby greatly reducing flood damage.  相似文献   

Dynamic modelling of retrogressive landslides with emphasis on the role of clay sensitivity          下载免费PDF全文

Xue Zhang  Scott W. Sloan  Eugenio Oñate 《国际地质力学数值与分析法杂志》2018,42(15):1806-1822

This paper presents a detailed numerical study of the retrogressive failure of landslides in sensitive clays. The dynamic modelling of the landslides is carried out using a novel continuum approach, the particle finite element method, complemented with an elastoviscoplastic constitutive model. The multiwedge failure mode in the collapse is captured successfully, and the multiple retrogressive failures that have been widely observed in landslides in sensitive clays are reproduced with the failure mechanism, the kinematics, and the deposition being discussed in detail. Special attention has been paid to the role of the clay sensitivity on each retrogressive failure as well as on the final retrogression distance and the final run‐out distance via parametric studies. Moreover, the effects of the viscosity of sensitive clays on the failure are also investigated for different clay sensitivities.  相似文献   

基于噪声谱比法的内蒙古西部地区台站场地响应研究     

张珂  王鑫  王树波  张红才  宋晓燕 《大地测量与地球动力学》2020,40(6):646-651

利用内蒙古西部12个台站的地脉动噪声数据，采用噪声谱比法研究台站的场地响应情况。分析表明，台站场地响应按曲线形态可分为3类，且可能受地形地貌、局部构造和台基状况等条件影响。对比分析噪声谱比法与Moya方法的场地响应结果发现，场地响应曲线形态基本一致，只有极少数台站存在明显差异。结果表明，内蒙古西部区域大部分台站的台基状况总体较好，场地响应曲线较为平坦，无明显频率放大点。  相似文献   

LHRH-A和hCG对南方鲶血清促性腺激素水平的影响     

邓思平  王德寿  张耀光  吴天利 《广东海洋大学学报》2003,23(1):13-16

运用放射免疫分析法测定了促黄体释放激素类似物 (LHRH A)和人绒毛膜促性腺激素(hCG)对南方鲶血清促性腺激素 (GTH)水平的影响 ,结果表明 :LHRH A和hCG都能提高南方鲶一龄幼鱼血清GTH水平 ,hCG与LHRH A结合注射后血清GTH水平显著高于单独注射hCG或LHRH A后的血清GTH水平。LHRH A和hCG结合注射可诱导性成熟南方鲶排卵 ,同时排卵过程中伴随着血清GTH水平的急剧上升 ,在排卵后迅速下降 ;注射同样剂量的药物而未排卵的血清GTH水平虽有升高 ,但升高的幅度不及排卵鱼。这种血清GTH水平的急剧增高对诱导南方鲶卵母细胞最后成熟和排卵具有重要作用。  相似文献   

PRELIMINARY STUDY ON THE FLOODING AND DROUGHT CLAMITY DURING PAST 1500 YEARS IN THE HAI′AN REGION，JIANGSU PROVINCE   总被引：1，自引：0，他引：1  

ZHANGQiang  CHENGJi 《中国地理科学(英文版)》2002,12(2):146-151

Collection and arrangement of the historical records of climatic changes and environment evolution,espectial-lyin the aspect of calamities,are made on the history documents of past 1500 years about Haiˊan region,Jiangsu Province.There existed two obvious flooding-drought frequently-occurring periods:one was from 1550 AD to 1850 AD and another was 100 AD to 1200AD.The period of 1550 AD to1850 AD is interrupted by two relatively arid and cold climatic periods:one was from 1630 AD to 1700 AD and another was 1750 AD to 1820 AD.The main characteristic of the calamity periods is that they occurred by turns,and sometimes,both drought and flooding occurred in the same year.The instability of the climatic changes in the Little Ice Age may be the main reason of the frequently-occurring flooding and drought in Haiˊan region.Research results also show that the frequently-occurring periods of flooding and drought is in close relationship with the solar activity,and therefore,occurrence of the flooding and drought may be in relation with the intensity of the solar activity.This hypothesis may need further study in the future.  相似文献