河西内陆河春季流量变化特征的分析和预测

利用昌马、莺落峡、九条岭３个水文站四十余年的月平均流量资料,分析河西地区３条主要内陆河春季流量的长期变化特征,并用均生函数模型对流量进行了预报,为河西地区水资源的研究和利用提供参考依据     

全球大地热流-岩石生热率关系综合分析

大地热流分析是研究大地构造地球动力学和地壳化学组成的一个重要手段通过对全球范围大陆地区大地热流和岩石放射性生热率数据的综合统计分析探讨地壳一地慢热流配分统计结果揭示,全球尺度显生亩地质构造区热流与岩石生热率之间不存在简单的线性关系,但两者在隐生宙地盾区却具有明显正相关关系从大地热流-岩石生热率关系在显生亩地区和在隐生宙地区的差异可以大致确定壳-幔热流成分的变化范围取地壳厚度为30－50km,根据前寒武地盾区热流与生热率之间的统计关系可以进一步推测地壳岩石中放射性生热元素的平均丰度范围分别为铀（0．5-1．6）×10－6,钍（1．8－6．1）×10－6,氧化钾0．6％-1．9％．     

Velocity profiles and bed shear stress over various bed configurations in a river bend

Vertical velocity profiles measured over various bed configurations (plane beds, ripples, and dunes) in. the meandering River South Esk, Glen Clova, Scotland are presented on semilogarithmic paper. Local bed shear stress and roughness height are calculated from the lowermost parts of the profiles using the Karman-Prandtl law of the wall; these parameters, and the geometrical properties of the profiles, are related to the various bed configurations. A graphical model is used to identify profiles developed on specific regions of dune geometry, in order to discriminate those profiles that define bed shear effective in transporting sediment over dunes. An assessment is made of the errors involved in estimating local mean velocity from extrapolating the law of the wall to the water surface. A Darcy-Weisbach friction coefficient is related to bed configuration and local stream power.     

Efficiency verification of a horizontal flow barrier via flowmeter tests and multilevel sampling

The remediation strategy for an industrial site located in a coastal area involves a pump and treat system and a horizontal flow barrier (HFB) penetrating the main aquifer. To validate the groundwater flow conceptual model and to verify the efficiency of the remediation systems, we carried out piezometric measurements, slug tests, pumping tests, flowmeter tests and multilevel sampling. Flowmeter tests are used to infer vertical groundwater flow directions, and base exchange index is used to infer horizontal flow directions at a metric scale. The selected wells are located both upstream and downstream of the HFB. The installation of the HFB produced constraints to the groundwater flow. A stagnant zone of contaminated freshwater floating over the salt wedge in the upper portion of the aquifer is detected downstream of the HFB. This study confirms that the adopted remediation system is efficiently working in the area upstream of the HFB and even downstream in the bottom part of the aquifer. At the same time, it has also confirmed that hot spots are still present in stagnant zones located downstream of the HFB in the upper part of the aquifer, requiring a different approach to accomplish remediation targets. The integrated approach for flow quantification used in this study allows to discriminate the direction and the magnitude of groundwater fluxes near an HFB in a coastal aquifer. Copyright © 2012 John Wiley & Sons, Ltd.     

Understanding of hydraulic properties from configurations of stochastically distributed fracture networks

A systematic investigation of the effect of configurations of stochastically distributed fracture networks on hydraulic behaviour for fractured rock masses could provide either quantitative or qualitative correlation between the structural configuration of the fracture network and its corresponding hydraulic behaviour, and enhance our understanding of appropriate application of groundwater flow and contaminant transport modelling in fractured rock masses. In this study, the effect of block sizes, intersection angles of fracture sets, standard deviations of fracture orientation, and fracture densities on directional block hydraulic conductivity and representative elementary volume is systematically investigated in two dimensions by implementing a numerical discrete fracture fluid flow model and incorporating stochastically distributed fracture configurations. It is shown from this investigation that the configuration of a stochastically distributed fracture network has a significant quantitative or qualitative effect on the hydraulic behaviour of fractured rock masses. Compared with the deterministic fracture configurations that have been extensively dealt with in a previous study, this investigation is expected to be more practical and adequate, since fracture geometry parameters are inherently stochastically distributed in the field. Moreover, the methodology and approach presented in this study may be generally applied to any fracture system in investigating the hydraulic behaviours from configurations of the fracture system while establishing a ‘bridge’ from the discrete fracture network flow modelling to equivalent continuum modelling in fractured rock masses. Copyright © 2007 John Wiley & Sons, Ltd.     

A coupled model for prediction of settlement and gas flow in MSW landfills

Prediction of long‐term settlement and control of gas pollution to the environment are two principle concerns during the management of municipal solid waste (MSW) landfills. The behavior of settlement and gas flow in MSW landfills is complicated due to the combined effect of mechanical deformation of the solid skeleton and continuous biodegradation of the waste. A one‐dimensional settlement and gas flow model is presented in this paper, which is capable of predicting time evolution of settlement as well as temporal and spatial distribution of gas pressure within multi‐layered landfills under a variety of operating scenarios. The analytical solution to the novel model is evaluated with numerical simulation and field measurements. The resulting efficiency and accuracy highlight the capability of the proposed model to reproduce the settlement behavior and gas flow in MSW landfills. The influences of operating conditions and waste properties on settlement and gas pressure are examined for typical MSW landfills. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental and computational validation and verification of the Stokes–Darcy and continuum pipe flow models for karst aquifers with dual porosity structure

In our previous study, we developed the Stokes–Darcy (SD) model was developed for flow in a karst aquifer with a conduit bedded in matrix, and the Beavers–Joseph (BJ) condition was used to describe the matrix–conduit interface. We also studied the mathematical well‐posedness of a coupled continuum pipe flow (CCPF) model as well as convergence rates of its finite element approximation. In this study, to compare the SD model with the CCPF model, we used numerical analyses to validate finite element discretisation methods for the two models. Using computational experiments, simulation codes implementing the finite element discretisations are then verified. Further model validation studies are based on the results of laboratory experiments. Comparing the results of computer simulations and experiments, we concluded that the SD model with the Beavers–Joseph interface condition is a valid model for conduit–matrix systems. On the other hand, the CCPF model with the value of the exchange parameter chosen within the range suggested in the literature perhaps does not result in good agreement with experimental observations. We then examined the sensitivity of the CCPF model with respect to the exchange parameter, concluding that, as has previously been noted, the model is highly sensitive for small values of the exchange parameter. However, for larger values, the model becomes less sensitive and, more important, also produces results that are in better agreement with experimental observations. This suggests that the CCPF model may also produce accurate simulation results, if one chooses larger values of the exchange parameter than those suggested in the literature. Copyright © 2011 John Wiley & Sons, Ltd.     

Importance of no‐rain measurements on the comparison of radar and rain gauge rain rate

This study evaluated four possible cases of comparing radar and rain gauge rain rate for the detection of mean‐field bias. These four cases, or detection designs, consider in this study are: (1) design 1‐uses all the data sets available, including zero radar rain rate and zero rain gauge rain rate, (2) design 2—uses the data sets of positive radar rain rate and zero or positive rain gauge rain rate, (3) design 3—uses the data sets of zero or positive radar rain rate and positive rain gauge rain rate and (4) design 4—uses the data sets of positive radar rain rate and positive rain gauge rain rate. A theoretical review of these four detection designs showed that only the design 1 causes no design bias, but designs 2, 3 and 4 can cause positive, negative and negative design biases, respectively. This theoretical result was also verified by applying these four designs to the rain rate field generated by a multi‐dimensional rain rate model, as well as to that of the Mt Gwanak radar in Korea. The results from both applications showed that especially the design 4, which is generally used for the detection of mean‐field bias of radar rain rate, causes a serious design bias; therefore, is inappropriate as a design for detecting the mean‐field bias of radar rain rate. Copyright © 2009 John Wiley & Sons, Ltd.     

Land cover change detection in West Jilin using ETM ＋ images

In order to assess the information content and accuracy of Landsat ETM digital images in land cover change detection,change-detection techniques of image differencing, normalized difference vegetation index,principal components analysis and tasseled-cap transformation were applied to yield 13 images. These images were thresholded into change and no change areas. The thresholded images were then checked in terms of various accuracies. The experiment results show that kappa coefficients of the 13 images range from 48.05-78.09. Different images do detect different types of changes. Images associated with changes in the near-inflared-reflectance or greenness detects crop-type changes and changes between vegetative and non-vegetative features. A unique means of using only Landsat imagery without reference data for the assessment of change in arid land are presented. Images of 12t June, 2000 and 2‘d June, 2002 are used to validate the means. Analyses of standard accuracy and spatial agreement are performed to compare the new images (hereafter called “change images” ) representing the change between the two dates. Spatial agreement evaluates the conformity in the classified “change pixels” and “no-change pixels” at the same location on different change images and comprehensively examines the different techniques. This method would enable authorities to monitor land degradation efficiently and aeculately.