The significance of morphometric analysis for obtaining groundwater potential zones in a structurally controlled terrain

Watershed development and management plans are more important for harnessing surface water and groundwater resources in arid and semi-arid regions. To prepare a comprehensive watershed development plan, it becomes necessary to understand the topography, erosion status and drainage patterns of the region. This study was undertaken to determine the drainage characteristics of Pageru River basin using topographical maps on a scale of 1:50,000. The total area of the Pageru River basin is 480 km². It was divided into X sub-basins for analysis. The drainage patterns of the basin are dendritic and include a sixth order stream. The quantitative analysis of various aspects of a river basin drainage network characteristics reveals complex morphometric attributes. The streams of lower orders mostly dominate the basin. The development of stream segments in the basin area is more or less affected by rainfall. The elongated shape of the basin is mainly due to the guiding effect of thrusting and faulting. The erosional processes of fluvial origin have been predominately influenced by the subsurface lithology of the basin.     

川中丘陵区紫色土表层土壤有机碳分布及影响因素

以2004～2006年间野外采样数据，采用土壤类型法对川中丘陵区（内江、资阳和遂宁三市）紫色土表层土壤有机碳密度及储量进行估算，分析了土壤有机碳密度的分布差异。据统计研究区紫色土面积为9070．19km^2，研究结果：表层土壤有机碳密度介于3．32kgC／m^2～1．71kgC／m^2间，具有高度的变异性，表层土壤有机碳储量为1．84Tg。并对影响紫色土有机碳分布的母质、地形和土地利用方式等因素进行了分析：不同成土母质上发育的表层土壤有机碳密度有差异，但均与母岩及其风化物有较强的相关性；主要土属从丘顶到丘脚土壤有机碳密度均逐渐增高；不同土地利用方式下土壤有机碳密度不同，但基本遵循疏林地〉荒草地〉坡耕地的规律。     

基于土壤水分动态随机模型的土壤湿度概率密度函数研究进展

简要回顾和评述了几个典型土壤水分动态随机模型和相应的土壤湿度概率密度函数,并基于这些模型的模拟结果就系统随机波动、气候因素、土壤特性、植被条件、地形特征对稳定状态土壤湿度概率密度函数的影响分别进行了分析和讨论,同时还引用相关的实验结果对这些影响进行佐证.结果表明,土壤湿度概率密度函数对以上因子的响应非常敏感,对揭示土壤水分动态和诠释生态水文现象有很好的指导意义.指出未来土壤湿度概率密度函数的研究方向:开发更加逼近真实情况的随机模型;用土壤湿度概率密度函数的思想量化植被水分胁迫、耦合土壤水分动态与养分动态;对某一地区建立其土壤湿度概率密度函数,并用该函数指导其他相关的生态建设和研究.     

A note on the lithosphere thickness and heat flow density of the Indian Craton from MAGSAT data

The Curie depth map of India compiled from MAGSAT data has been used for preparing the lithosphere thickness and the surface heat flow density maps of the Indian Craton, utilizing the concept of magnetothermometry. The lithosphere thicknesses of the major Indian geological units/provinces, as obtained from the prepared map, are found to be in reasonably good agreement with the previously published values for these regions. Also, the surface heat flow density values obtained from the prepared maps closely follow the previously published results. The maps are useful in providing first order estimates of lithosphere thickness and surface heat flow density of the important geological units/provinces of India.     

氟化物环境容量的研究

由高斯烟羽模式推导出的标准浓度分布推算源强分布的反演模式方法,计算了西宁市北郊地区环境空气中氟化物的环境容量。计算结果表明:拟建或已经在生产的各铝厂氟化物排放量均不超过按城市标准计算出的环境容量值,但均超过按农业区标准计算出的环境容量值。为了保护该地区农业生态环境,需要对现有的各铝厂氟化物排放量进行削减。     

Emplaced Geotechnical Characteristics of Hydraulic Fills in a Number of Australian Mines

Hydraulic fills used in Australian mines have similar grain size distributions whilst having quite different specific gravity values, typically in the range of 2.7–4.4. When produced and distributed in slurry at 65–75% by solid content, they settle to produce fills with similar geotechnical characteristics. The fills under investigation have been found to settle, in the laboratory, to a dry density of about 0.56 × specific gravity, a saturation water content of about 17–34%, and a porosity of 37–49%. A quick estimate of the optimum water content that gives the minimum porosity may be obtained by locating the intersection of the saturation curve and minimum porosity line, which may simply be done on a water content vs. porosity plot. However, transportability of the slurry requires it to be mixed at water content substantially greater than the optimum water content. As the tailings settle out of suspension, they settle to relative density of 50–80%. This paper shows that the current empirical relationships relating relative density and N-value to friction angle for sands will significantly underestimate the friction angle of the hydraulic fills. Based on limited experimental data, a unique relationship between relative density and friction angle is proposed for hydraulic fills placed in some Australian mines.     

Study of the Probability Density Functions From a Large-Eddy Simulation for a Stably Stratified Boundary Layer

Turbulence in a non-strongly stably stratified large-eddy simulation (LES) case is studied through probability density functions (PDFs) to obtain additional information than that provided by classical LES averages. The PDFs are computed for one hour within the steady-state regime at three different levels: near the surface, in the middle and at the top of the boundary layer, for the wind components and the temperature. The physical significance of these PDFs from LES is discussed and they are compared to those obtained from observations. The analysis of the eddy structures within the stably stratified boundary layer is made through the combined study of the fields, the spectra and the statistical moments obtained from the PDFs and joint PDFs. The homogeneity of the fields is inspected through a comparison of the ensemble to the temporal and the spatial PDFs, showing that the ergodic theorem is not fulfilled. To this end, the sensitivity of the PDF moments to the LES resolution is explored.     

Consequences of hyperconcentrated flow for process‐based soil erosion modelling on the Chinese Loess Plateau

High sediment concentrations in runoff are a characteristic feature of the Chinese Loess Plateau, and are probably caused by factors such as the occurrence of erodible materials on steep slopes, the characteristics of the loess and the harsh climate that results in low plant cover. When sediment concentration increases, fluid density increases, viscosity increases and settling velocity decreases. These effects become increasingly important with increasing concentration and can result in flow behaviour that is quite different from that of clear water flow. Although the net effect of these changes on the flow is not always apparent, erosion models that deal with high sediment concentrations should consider such effects and could include corrections for some of these effects. A case study in a small catchment on the Loess Plateau indicated that sediment concentrations were considerable, and literature data suggested that for such sediment concentrations, corrections for settling velocity, fluid density and viscosity are needed. Furthermore, a number of corrections are necessary to be able to compare field measurements with results of soil erosion models: sediment volume should be subtracted from runoff volume and a density correction is needed to use data from a pressure transducer. For flumes that were used to measure discharge from smaller areas inside the catchment, the measured water level should be corrected by subtracting the sediment level in the flume from the water level, while the sediment volume should also be subtracted from the discharge. Finally, measured concentration should be corrected to give concentration expressed as grams per litre of clear water, since soil erosion models express sediment concentration in this way. Copyright © 2006 John Wiley & Sons, Ltd.     

Fracture Toughness Measurements and Acoustic Emission Activity in Brittle Rocks

Fracture toughness measurements under static loading conditions have been carried out in Barre and Lac du Bonnet granites. An advanced AE technique has been adopted to monitor real-time crack initiation and propagation around the principal crack in these tests to understand the processes of brittle failure under tension and related characteristics of the resulting fracture process zone. The anisotropy of Mode I fracture toughness has been investigated along specific directions. Microcrack density and orientation analysis from thin section studies have shown these characteristics to be the primary cause of the observed variation in fracture toughness, which is seen to vary between 1.14 MPa.(m)^1/2 and 1.89 MPa.(m)^1/2 in Barre granite. The latter value represents the case in which the crack is propagated at right angles to the main set of microcracks. The creation of a significant fracture process zone surrounding the propagating main crack has been confirmed. Real-time imaging of the fracture process and formation of fracture process zone by AE techniques yielded results in very good agreement with those obtained by direct optical analysis.