The travel time of groundwater plays a major role in the understanding of hydrogeological systems; however, large data sets necessary for regional studies of groundwater age are rare. In this study, a unique large data set of groundwater samples analysed for tritium and helium isotopes collected over the last 20 years from Cenozoic aquifers of the North German Plain is explored. Hereby, the variety of natural and technical influences on the tritium-helium age, including screen depth and length, groundwater recharge rate and climatic effects, are investigated. To a sampling depth of ~40 m below ground level, the median tritium-helium age increases almost linearly with depth, reaching a maximum of 40 years. Below, the portion of older, tritium-free water rises. The tritium-helium ages of the tritium-bearing portion increase only slightly to a maximum of about 46 years. The depth distribution of the tritium-helium age shows a dependency on groundwater recharge rates. Considering the same depth level, younger ages are related to higher groundwater recharge rates as compared to groundwater that infiltrated in areas with lower recharge rates. This is especially observed for shallow depths. Tritium-helium ages younger than 40 years are reflected well in the atmospheric tritium input curves, while deviations from it can be related to anthropogenic influences such as input from nuclear power plants and irrigation with deep, tritium-poor groundwater. The regional distribution for shallow wells indicates increasing tritium-helium ages from west to east, corresponding to decreasing groundwater recharge rates due to the more continental climate in the east.
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The Thiem equation of radial groundwater flow to a well is more than 100 years old and is still commonly used. Here, deviations caused by some of its simplifications are quantified by comparing the analytical to a numerical model that allows the implementation of more complex geometries. The assumption of horizontal flow in the Thiem equation, which necessitates uniform inflow over the entire screen length of the fully penetrating well, was found to cause deviations from actual pumping wells where the pump is placed above the screen, resulting in non-uniform inflow and additional drawdown. The same applies to partially penetrating wells, where inflow peaks and additional drawdown occur, especially when the well is screened in the lower part of the aquifer. The use of the Thiem equation in the near-field of a well should thus be restricted to situations where the screen inflow is relatively uniformly distributed, e.g. when it covers large portions of the aquifer thickness. The presence of a gravel pack and a background gradient, on the other hand, are of limited importance. 相似文献
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γ射线康普顿背散射扫描仪测量的信噪比研究 总被引：1，自引：0，他引：1
本文详细给出了ＣＢＳ测量中噪声的物理来源和降低噪声的有效措施,还对信噪比进行了定量的分析和讨论。 相似文献
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Georg Houben 《Hydrogeology Journal》2018,26(6):1789-1799
The publication “The water supply of some North Sea spas” by Alexander Herzberg in 1901 is a cornerstone of coastal groundwater research. It was fundamental to the development of the Ghijben-Herzberg principle, which describes the hydrostatic equilibrium between fresh and saline groundwater. Due to its age and the language barrier, the paper is often cited but probably rarely read. Therefore, the original paper has been translated from German into English, accompanied by an introduction and notes explaining the historical context. 相似文献
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Vincent E. A. Post Gualbert Oude Essink Adam Szymkiewicz Mark Bakker Georg Houben Emilio Custodio Clifford Voss 《Hydrogeology Journal》2018,26(6):1767-1770
The Salt Water Intrusion Meetings, or SWIMs, are a series of meetings that focus on seawater intrusion in coastal aquifers and other salinisation processes. 2018 marks the 50th year of the SWIM and the 25th biennial meeting. The SWIM proceedings record half a century of research progress on site characterisation, geophysical and geochemical techniques, variable-density flow, modelling, and water management. The SWIM is positioning itself to remain a viable platform for discussing the coastal aquifer management challenges of the next 50 years. 相似文献
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Houben GJ 《Ground water》2004,42(1):78-82
Ferric iron encrustations are a common problem that seriously affects the performance of wells and drains. Their formation is induced by the mixing of reduced ground water containing ferrous iron with oxic shallow ground water and exposure to air. The process of ferrous iron oxidation is a kinetically controlled reaction. The reaction rate has a quadratic dependency on pH. The precipitating oxides have an autocatalytic effect that further enhances reaction progress. This paper describes the application of kinetic models to the problem of encrustation formation. Influences of pH, residence time, and autocatalysis were modeled. The overall influence of the autocatalytic reaction path is particularly strong when initial amounts of iron oxides are present. Autocatalysis provides a good explanation on the development of well yield commonly measured in the field. Encrustation precipitation is slow at first, but speeds up after a sufficient amount of iron oxide has built up. An incomplete removal of iron oxide encrustations during rehabilitation leads to a renewed increase in catalytic efficiency and encrustation precipitation. 相似文献
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兰博集团开发生产的ＬＢＤ１０１型康普顿背散射扫描仪（ＣＢＳ），可以由被测物的单侧进行检查，广泛用于工业领域的无损检测（ＮＤＴ）和无损评价（ＮＤＥ）。这种新仪器采用非常简单而紧凑的单源和单探测器系统。其扫描范围为２００ｍｍ（Ｘ向）×２００ｍｍ（Ｙ向）×１００ｍｍ（Ｚ向或深度），用自动升降装置可调节检测高度为２００ｍｍ～２０００ｍｍ。ＬＢＤ１０１优越的技术指标包括：最高的空间分辨率优于０．８ｍｍ，最好的密度分辨率约为１％，最小可探测的缺陷体积小于０．６ｍｍ３，最小可探测的缺陷大小为０．８，最小可探测裂纹宽度为０．１５ｍｍ。辐射防护安全性能好，辐射剂量率非常低。本文摘要并详细比较了ＣＯＭＳＣＡＮ１６０和ＬＢＤ１０１型ＣＢＳ扫描仪的性能和主要技术指标。本文列出了设计便携式高分辨率ＣＢＳ扫描仪的主要技术问题，还给出了实际检测结果 相似文献
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Hyperfiltration (reverse osmosis) and subsequent precipitation of minerals from the hyperfiltrated solution are processes that potentially decrease the hydraulic conductivity of porous media. These processes were demonstrated by hyperfiltrating NiSO4 solutions through fine-grained sandstone. The mineral precipitates occur in very small (mm sized) layers at the high-pressure side of the samples where they create zones of lowered hydraulic conductivity (2–3 orders of magnitude lower than initial). The total amount of precipitates is very small compared to the dissolved mass which was passed through the membrane. Hyperfiltration-induced precipitates and the resulting lowering of hydraulic conductivities were observed at solute saturations as low as 10%. Nevertheless, at saturations higher than 50% the conductivity reduction strongly increased. Full reversibility of the hydraulic conductivity reduction by extensive re-flushing with water was only obtained at low initial solute saturations (10%). This indicates that precipitated minerals in many pores are susceptible only to very slow, diffusion-controlled re-dissolution. 相似文献
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Desens Annika Houben Georg Sültenfuß Jürgen Post Vincent Massmann Gudrun 《Hydrogeology Journal》2023,31(3):621-640
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