Une dépression piézométrique naturelle en hausse au Sahel (Sud-Ouest du Niger)A rising piezometric depression in the Sahel (southwestern Niger)     

Guillaume Favreau  Christian Leduc  Christelle Marlin  Abdou Guéro 《Comptes Rendus Geoscience》2002,334(6):395-401

In southwest Niger, the Continental Terminal water table displays a natural hollow shape about 10 m in depth over an area of 4000 km². A 10-year survey of this hollow aquifer has shown that current recharge is above $\text{20 }\text{mm}\text{yr}{}^{\mathrm{?1}}$. The water table has risen continuously since the 1950–1960s as a result of land clearance. This shows a disequilibrium in the aquifer balance. The long-term recharge rate is estimated by radioisotopes to be around $\text{1 }\text{mm}\text{yr}{}^{\mathrm{?1}}$. This figure fits with the only possible origin of the piezometric depression, i.e. evapotranspiration losses in its centre. To cite this article: G. Favreau et al., C. R. Geoscience 334 (2002) 395–401.  相似文献   

Natural Geological Weighing Lysimeters: Calibration Tools for Satellite and Ground Surface Gravity Monitoring of Subsurface Water-Mass Change     

Bardsley  W. E.  Campbell  D. I. 《Natural Resources Research》2000,9(2):147-156

Increased accuracy in measuring temporal variations in the Earth's gravity field allow inprinciple the use of gravity observations to deduce subsurface water-mass changes. This canbe with respect to a small area, or as a larger spatial average of water mass change usinggravity observations from low-altitude satellites, such as the forthcoming GRACE mission.At both scales, there is a need to validate gravity-based estimates against field recordings ofactual subsurface water-mass variations. In practice, this could prove difficult because thespatial integral of all water-storage change components can be subject to considerable fieldmeasurement error. An alternative approach to the validation process is proposed by whichsuitable geological formations are utilized as giant weighing devices to directly measure area-integratedwater-mass changes. The existence of such natural geological weighing lysimetersis demonstrated using observations from a replicated experimental site in New Zealand. Sitesof this type could be used to verify water-storage change estimates derived from sensitiveground surface gravity instrumentation. In addition, geological lysimeters could be used tomake local checks on the accuracy of any estimated regional water-mass time series, whichis proposed for satellite calibration. The land area weighed by a geological lysimeter increaseswith formation depth and it is speculated that recordings made at oil well depth may allowdirect monitoring of subsurface water mass changes at the regional scale.  相似文献   

Geostatistical mapping of geomorphic variables in the presence of trend     

R. M. Lark  R. Webster 《地球表面变化过程与地形》2006,31(7):862-874

Mapping geomorphic variables geostatistically, specifically by kriging, runs into difficulties when there is trend. The reason is that the variogram required for the kriging must be of residuals from any trend, which in turn cannot be estimated optimally by the usual method of trend surface analysis because the residuals are correlated. The difficulties can be overcome by the use of residual maximum likelihood (REML) to estimate both the trend and the variogram of the residuals simultaneously. We summarize the theory of REML as it applies to kriging in the presence of trend. We present the equations to show how estimates of the trend are combined with kriging of residuals to give empirical best linear unbiased predictions (E‐BLUPs). We then apply the method to estimate the height of the sub‐Upper‐Chalk surface beneath the Chiltern Hills of southeast England from 238 borehole data. The variogram of the REML residuals is substantially different from that computed by ordinary least squares (OLS) analysis. The map of the predicted surface is similar to that made from kriging with the OLS variogram. The variances, however, are substantially larger because (a) they derive from a variogram with a much larger sill and (b) they include the uncertainty of the estimate of the trend. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

辐射井在强透水弱调节含水层地下水开采中的应用     

赵宝峰  王润兰  李文智  康卫东  宋寿鹏 《地下水》2006,28(4):49-51

本文通过在强透水弱调节含水层研究区建立了地下水流数模型、并在研究区域进行数值模拟计算的基础上,分析了不同取水构筑物的取水效果.得出了强透水弱调节含水层地下水采用辐射井开采的优越性和辐射井的设计参数,总结出辐射井是开采强透水弱调节含水层较为合理的取水构筑物.  相似文献   

大南湖煤田一井田水文地质条件分析     

王宝成  邵洪文  韦波 《新疆地质》2006,24(3):267-269

通过对大南湖煤田一井田含水层特征、水力联系、地下水补给、径流与排泄及地下水化学特征等因素的分析,确定该井田水文地质条件类型,为矿床开采提供依据.  相似文献   

淮河流域(河南段)第四纪地层沉积规律     

左正金  王献坤  程生平  罗文金  王伟峰 《地下水》2006,28(4):34-36

本文详细介绍了第四纪地层划分原则,确定了第四纪下限与各世内分的时间,对河南段各个时期地势、各统的沉积规律进行了阐述,确定了含水层主流相与边缘相.  相似文献   

灰色聚类法在常州市第Ⅱ承压地下水水质评价中的应用     

刘洪  孙国夕 《地下水》2007,29(6):29-32

在灰色聚类方法原理的基础上，探讨了如何通过白化函数生成灰色聚类矩阵，并以常州市第Ⅱ承压地下水为例进行了水质评价，评价结果表明，常州市大部分第Ⅱ承压地下水水质优良，达到了Ⅰ类水，未遭受外来物质的污染，评价结果符合实际情况。  相似文献   

北京市朝阳区沙子营垃圾污染物在潜水含水层中迁移规律的现场模拟实验     

刘长礼詹黔花  张凤娥张云 张胜叶浩  侯宏冰张明裴丽欣  姜建梅 《地质通报》2007,26(3):305-311

选择北京平原区水文地质、环境地质等方面都比较典型的沙子营垃圾堆放场,建立了其水文地质模型。在充分收集资料、分析得出部分计算所需参数后,采用现场弥散实验、勘查取样测试等方法,求得了该含水层的弥散系数等参数;用二维非稳定流溶质运移方程对污染物在此含水层中的迁移扩散规律、速度和污染范围等进行了模拟计算;采用现场钻探、取样测试分析等方法,评价了该含水层的实际污染状况。实验模拟计算和现场调查结果表明:污染物在潜水含水层中的运移规律遵循二维非稳定流场中的溶质运移方程,污染物在潜水含水层中的运移速度约为86.25m/a,迁移扩散主要发生在地下水流向上,侧向扩散宽度极小,是地下水流向上的1/17。  相似文献   

基于尺度因素的地下水随机分析          下载免费PDF全文

史良胜  杨金忠  林琳  李少龙 《水科学进展》2007,18(1):39-43

针对小尺度的各态历经假设的失效,研究了小尺度上多孔介质特性参数统计特征。利用基于K-L(Karhunen-Loeve)展开和混沌展开的谱模型,分析了尺度大小对地下水流动的影响。结果表明,尺度大小导致了特征值系列和特征函数系列的变化,尺度的变化对水头、含水量、流速影响程度不同;水头和流速方差与尺度相关,尺度越大,水头和流速方差越大;研究尺度的变化对水头、含水量、流速均值产生的影响较小。  相似文献   

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

Xiaolong Hu  Xiaoming Wang  Max Gunzburger  Fei Hua  Yanzhao Cao 《水文研究》2012,26(13):2031-2040

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.  相似文献