Integrated water resources management: Concepts and issues   总被引：1，自引：0，他引：1  

H.H.G. Savenije  P. Van der Zaag 《Physics and Chemistry of the Earth》2008,33(5):290-297

After the describing the historical developments that led the development of Integrated Water Resources Management (IWRM), the paper defines this important concept. It subsequently deals with the thorny issue of water security as well as water conflict, after which the major issues over which thus far no consensus has been achieved are briefly reviewed. The paper concludes with an analysis of the role of the IAHS International Commission on Water Resources Systems (ICWRS) in promoting IWRM.  相似文献   

Global ellipsoid-referenced topographic,bathymetric and stripping corrections to gravity disturbance     

P.?VajdaEmail author  A.?Ellmann  B.?Meurers  P.?Vaní?ek  P.?Novák  R.?Tenzer 《Studia Geophysica et Geodaetica》2008,52(1):19-34

This paper revisits several aspects of defining and computing the anomalous gravity data for purposes of gravimetric inversion/interpretation. Attention is paid to evaluation of a refined global topographic correction to the gravity disturbance based on the reference ellipsoid (RE) and constant reference density for solid topography onshore and sea water density for liquid topography offshore. The global bathymetric correction is discussed. Two issues associated with compilation and inversion of bathymetrically and topographically corrected gravity disturbances in regions of negative ellipsoidal (geodetic) heights are pointed out: the evaluation of normal gravity and the harmonic continuation of the gravity data. Stripping, the removal of an effect of a known density contrast, is considered also for additional geological elements such as lakes, glaciers, sedimentary basins, isostatic mountain roots, etc. The stripping corrections are discussed in the context of the gravimetric inverse problem.  相似文献   

Modelling the impact of afforestation on average annual streamflow in the Loess Plateau,China   总被引：1，自引：0，他引：1  

Xiao Ping Zhang  Lu Zhang  Tim R. McVicar  Tom G. Van Niel  Ling Tao Li  Rui Li  QinKe Yang  Liang Wei 《水文研究》2008,22(12):1996-2004

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Velocity analysis based on data correlation   总被引：1，自引：0，他引：1  

T. Van Leeuwen  W.A. Mulder 《Geophysical Prospecting》2008,56(6):791-803

Several methods exist to automatically obtain a velocity model from seismic data via optimization. Migration velocity analysis relies on an imaging condition and seeks the velocity model that optimally focuses the migrated image. This approach has been proven to be very successful. However, most migration methods use simplified physics to make them computationally feasible and herein lies the restriction of migration velocity analysis. Waveform inversion methods use the full wave equation to model the observed data and more complicated physics can be incorporated. Unfortunately, due to the band‐limited nature of the data, the resulting inverse problem is highly nonlinear. Simply fitting the data in a least‐squares sense by using a gradient‐based optimization method is sometimes problematic. In this paper, we propose a novel method that measures the amount of focusing in the data domain rather than the image domain. As a first test of the method, we include some examples for 1D velocity models and the convolutional model.  相似文献   

Slug test analysis to evaluate permeability of compressible materials     

Choi H  Nguyen TB  Lee C 《Ground water》2008,46(4):647-652

The line-fitting methods such as the Hvorslev method and the Bouwer and Rice method provide a rapid and simple means to analyze slug test data for estimating in situ hydraulic conductivity ( k ) of geologic materials. However, when analyzing a slug test in a relatively compressible geologic formation, these conventional methods may have difficulties fitting a straight line to the semilogarithmic plot of the test data. Data from relatively compressible geologic formations frequently show a concave-upward curvature because of the effect of the compressibility or specific storage ( S _s). To take into account the compressibility of geologic formations, a modified line-fitting method is introduced, which expands on Chirlin's (1989) approach to the case of a partially penetrating well with the basic-time-lag fitting method. A case study for a compressible till is made to verify the proposed method by comparing the results from the proposed methods with those obtained using a type-curve method (Kansas Geological Survey method [ Hyder et al. 1994 ]).  相似文献   

The compatibility of erosion data at different temporal scales     

Iris Peeters  Kristof Van Oost  Gerard Govers  Gert Verstraeten  Tom Rommens  Jean Poesen 《Earth and Planetary Science Letters》2008,265(1-2):138-152

Soil erosion processes have been studied intensively throughout the last decades and rates have been measured at the plot scale as well as at larger scales. However, the relevance of this knowledge for the modelling of long-term landscape evolution remains a topic of considerable debate. Some authors state that measurements of current rates are irrelevant to landscape evolution over a longer time span, as they are inconsistent with some fundamental characteristics of landscapes, such as the fact that the long-term sediment delivery ratio needs to be equal to 1 and that extrapolation of current rates would imply that all soils in Europe should have disappeared by now (e.g. Parsons, A.J., Wainwright, J., Brazier, R.E., Powell, D.M., 2006. Is sediment delivery a fallacy? Earth Surface Processes and Landforms 31, 1325–1328). In this study, we investigate if and to what extent estimates of long-term erosion rates are consistent with information obtained over much shorter time spans for the Loam Belt of Belgium.In a first step, observed short-term and long-term patterns in the Belgian loess area are compared statistically by classifying the study area into landscape element classes and comparing average erosion values per class. This analysis shows that the erosion intensities on the two temporal scales are of the same order of magnitude for each landscape element class. Next, the spatially distributed model WaTEM LT (Water and Tillage Erosion Model Long Term) is calibrated based on the available short-term data by optimising average erosion values for the same landscape element classes. Finally, the calibrated model is used to simulate long-term landform evolution, and is validated using long-term data based on soil profile truncation. We found that the model allows simulating landscape evolution on a millennial time scale using information derived from short-term erosion and deposition data. However, it is important that land use is taken into account for the calibration in order to obtain realistic patterns on a longer time scale. Our analysis shows that, at least for the study area considered, data obtained on erosion and deposition rates over various temporal scales have the same orders of magnitude, thereby demonstrating that measurements of current rates of processes can be highly relevant for interpreting long-term landscape evolution.  相似文献   

Seismic site effects by an optimized 2D BE/FE method I. Theory, numerical optimization and application to topographical irregularities     

B. Gatmiri  C. Arson  K.V. Nguyen 《Soil Dynamics and Earthquake Engineering》2008,28(8):632-645

This paper deals with the evaluation of seismic site effects due to the local topographical and geotechnical characteristics. The amplification of surface motions is calculated by a numerical method combining finite elements in the near field and boundary elements in the far field (FEM/BEM). The numerical technique is improved by time truncation. In the first part of this article, the accuracy and the relevance of this optimized method are presented. Moreover, parametric studies are done on slopes, ridges and canyons to characterize topographical site effects. The second part deals with sedimentary valleys. The complexity of the combination of geometrical and sedimentary effects is underlined. Extensive parametrical studies are done to discriminate the topographical and geotechnical effects on seismic ground movement amplifications in two-dimensional irregular configurations. Characteristic coefficients are defined to predict the amplifications of horizontal displacements. The accuracy of this quantitative evaluation technique is tested and discussed.  相似文献   

Approaches to modelling coupled flow and reaction in a 2D cementation experiment     

B. Cochepin  L. Trotignon  O. Bildstein  C.I. Steefel  V. Lagneau  J. Van der lee 《Advances in water resources》2008,31(12):1540-1551

Porosity evolution at reactive interfaces is a key process that governs the evolution and performances of many engineered systems that have important applications in earth and environmental sciences. This is the case, for example, at the interface between cement structures and clays in deep geological nuclear waste disposals. Although in a different transport regime, similar questions arise for permeable reactive barriers used for biogeochemical remediation in surface environments.The COMEDIE project aims at investigating the coupling between transport, hydrodynamics and chemistry when significant variations of porosity occur. The present work focuses on a numerical benchmark used as a design exercise for the future COMEDIE-2D experiment. The use of reactive transport simulation tools like Hytec and Crunch provides predictions of the physico-chemical evolutions that are expected during the future experiments in laboratory. Focus is given in this paper on the evolution during the simulated experiment of precipitate, permeability and porosity fields.A first case is considered in which the porosity is constant. Results obtained with Crunch and Hytec are in relatively good agreement. Differences are attributable to the models of reactive surface area taken into account for dissolution/precipitation processes. Crunch and Hytec simulations taking into account porosity variations are then presented and compared. Results given by the two codes are in qualitative agreement, with differences attributable in part to the models of reactive surface area for dissolution/precipitation processes. As a consequence, the localization of secondary precipitates predicted by Crunch leads to lower local porosities than for predictions obtained by Hytec and thus to a stronger coupling between flow and chemistry. This benchmark highlights the importance of the surface area model employed to describe systems in which strong porosity variations occur as a result of dissolution/precipitation. The simulation of highly non-linear reactive transport systems is also shown to be partly dependent on specific numerical approaches.  相似文献   

Polycyclic aromatic hydrocarbons from rural household biomass burning in a typical Chinese village     

HaiLin Wang  YaHui Zhuang  ZhengPing Hao  MeiQiu Cao  JinXian Zhong  XiaoKe Wang  Thi Kim Oanh Nguyen 《中国科学D辑(英文版)》2008,51(7):1013-1020

Biomass energy sources are still popular in the rural areas of developing countries for cooking and space heating. Since the incomplete combustion of agricultural residues in home-made ranges might lead to both outdoor and indoor air pollution and cause potential health threat to the rural population, we monitored the ambient levels of 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) at a typical rural site. Ambient particulate PAH samples (PM2.5 and PM10) were taken during both cooking and non-cooking periods. Source emission monitoring was also conducted for both improved and tra- ditional cooking stoves used in the area. Ambient PAHs had a significant increase during the cooking periods and varied from 72.1 to 554.4 ng/m3. The highest total PAH levels were found during the supper cooking time, in which five- and six-ring species accounted for a large proportion. The observed PAH levels during cooking periods at this rural site were even higher than those in urban areas. A good correlation was found between the benzo[a]pyrene level and the total PAH concentration (r=0.98), making benzo[a]pyrene a potential molecular marker for PAH pollution in the rural areas, where bio- mass burning is typical. The profiles of the particulate PAHs in both ambient air and source emissions showed a high proportion of high molecular-mass PAHs. In addition, emission factors of 16 PAHs from an improved household stove were found to be significantly lower than those from traditional stoves used in China and in other Asian countries.  相似文献   

On the design and selection of polychlorinated biphenyls for use in biological test systems     

M. Tysklind  P. L. Andersson  B. Van Bavel 《Marine environmental research》1998,46(1-5)

The polychlorinated biphenyls (PCBs) consist of a large number of individual congeners with varying degree of chlorination and possible substitution patterns. No single congener can be used as a representative congener for the whole class of compounds. Multivariate chemical characterisation (principal component analysis) in combination with factorial design provide tools by which small sets of structurally representative congeners can be determined. These tools are suggested to be used in the design of biological experiments in order to introduce systematic structural variation in the congeners to be tested and to make it possible to construct quantitative structure-activity relationships (QSARs). A QSAR based on bioaccumulation factors (BAFs) in fish for 20 systematically selected PCBs made it possible to predict BAFs for all 134 non-tested tetra-through hepta-chlorinated congeners. The use of these systematic and balanced sets of congeners in the experimental protocol will provide increased knowledge of the environmental behaviour of the PCBs.  相似文献