WEKU – a GIS-Supported stochastic model of groundwater residence times in upper aquifers for the supraregional groundwater management

 The supraregional GIS-supported stochastical model, WEKU, for the determination of groundwater residence times in the upper aquifers of large groundwater provinces is presented. Using a two-dimensional analytical model of groundwater flow, groundwater residence times are determined within two extreme cases. In the first case, maximal groundwater residence times are calculated, representing the part of groundwater, that is drained by the main surface water of a groundwater catchment area. In the second case, minimal groundwater residence times for drainage into the nearest surface water are determined. Using explicit distribution functions of the input parameters, mean values as well as potential ranges of variations of the groundwater residence times are derived. The WEKU model has been used for the determination of groundwater residence times throughout Germany. The model results – mean values and deviations of the groundwater velocity and the maximal and minimal groundwater residence times in the upper aquifers – are presented by general maps and discussed in detail. It is shown that the groundwater residence times in the upper aquifer vary regionally, differentiated between less than 1 year and more than 2000 years. Using this information, the time scales can be specified, until measures to remediate polluted groundwater resources may lead to a substantial groundwater quality improvement in the different groundwater provinces of Germany. With respect to its supraregional scale of application, the WEKU model may serve as a useful tool for the supraregional groundwater management on a state, federal or international level. Received: 15 August 1995 · Accepted: 15 October 1995     

数字图像压缩方法在天文上的应用

概述了数字图像压缩技术在天文领域应用的必要性。针对天文观测的特点和研究的需要，经过研究、分析和比较，提出了天文图像压缩的可行方案。通过应用计算机编程及压缩实验并给出相应的结果。     

RELAXING ASSUMPTIONS OF PERFECT INFORMATION IN PARK VISITATION MODELS*

Variables related to urban park awareness are identified and methods for relaxing assumptions of perfect information in park use models are discussed. Park awareness is related to park characteristics (age and degree of development of the park), population characteristics (race, age, length of residence, recreation participation), and distance. Park attributes are stronger predictors of both park awareness and use than is distance. These findings parallel similar research on the cognitive aspects of shopping decisions.     

REVIEWS OF GEOGRAPHIC SOFTWARE

Reviews of geographic software in this article: DEMO-GRAPHICS: WORLD POPULATIONS AND PROJECTIONS. ESP GAUSS. CEMODEL S. Damus LIMDEP. William H. Greene MICROSTAT 4.1 OTIS PCIPS. (Personal Computer Image Processing System) . H.J. Meyers and R. Bernstein. REGRESSION ANALYSIS OF TIME SERIES (RATS) SPSS/PC+ URBAN DATA MANAGEMENT SOFTWARE (UDMS)     

The importance of oxygen isotope provenance in relation to solute content of bulk meltwaters at Imersuaq Glacier,West Greenland

Stable oxygen isotope analysis and measurement of several dissolved cations and anions of bulk meltwater samples have provided information about the hydrochemical environment of the glacial hydrological system at Imersuaq Glacier, an outlet tongue from the Greenland ice‐sheet, West Greenland. The samples were collected at frequent intervals during the period 20–28 July 2000 in a small (<20 L s^?1) englacial meltwater outlet at the glacier margin. The results document the following findings: (i) a marked diurnal variation of δ¹⁸O is related to the composition of oxygen isotope provenances, mainly near‐marginal local superimposed ice and basal up‐sheared ice further up‐glacier; (ii) a relationship is seen between all base cations (Na⁺, K⁺, Ca²⁺, Mg²⁺), SO₄^2? and δ¹⁸O, indicating that solute acquisition is provided by solid–solution contact with the up‐sheared ice—as the relationship with Cl^? is weak the influence of seasalt‐derived solutes is small in the area; (iii) when the melt rate is high, two diurnal maxima of δ¹⁸O values and solute concentrations are measured, and it is suggested that a snow meltwater component is responsible for the second maximum of δ¹⁸O—a short residence time leads to a delayed decrease in ion concentrations. Copyright © 2003 John Wiley & Sons, Ltd.     

Directions and possibilities of mathematical geology

This paper considers the present state of mathematical geology. Three directions are recognized: applied, theoretical, and mathematical. Applied mathematical geology includes formal use of mathematics to solve problems and computer processing of data. Success is achieved by a correspondence of mathematical methods used to the nature of geological data. This correspondence can be demonstrated by purely mathematical means. Theoretical mathematical geology uses mathematics as a language of geology; however, a number of methodological problems must be solved: formalization of initial geological concepts and creation of a strict conceptual basis, substantiation of initial principles of mathematical simulation, creation of theoretical geological models, problems of elementary and coincidence in geology, and methodological substantiations of possibilities of any mathematical model to approximate geological models. The essense and significance of these problems are considered. The main task of mathematical geology is to prove its correspondence to the nature of the geological objects studied, geological data obtained, and geological problems solvable. Finally, the main problems of mathematical geology are not so much mathematical as geological and methodological.     

岩体三维节点偶对分析及其应用

本文讨论了节点偶对分析的三维扩展。节点偶对分析是针对摩擦滑动节理单元的约束边界进行的序列矢量判定。在三维节理单元的分析中,几何约束和相应的力学判据极为复杂,采用节点偶对等效结合力方法才能迎刃而解。文中对三维转向节理模型的分析得到合理的结果,它表明本文所提出的方法可成功地应用于节理岩体的有限元分析。