Groundwater-flow modeling in the Yucatan karstic aquifer, Mexico   总被引：1，自引：0，他引：1  

Roger González-Herrera  Ismael Sánchez-y-Pinto  José Gamboa-Vargas 《Hydrogeology Journal》2002,10(5):539-552

The current conceptual model of the unconfined karstic aquifer in the Yucatan Peninsula, Mexico, is that a fresh-water lens floats above denser saline water that penetrates more than 40 km inland. The transmissivity of the aquifer is very high so the hydraulic gradient is very low, ranging from 7–10 mm/km through most of the northern part of the peninsula. The computer modeling program AQUIFER was used to investigate the regional groundwater flow in the aquifer. The karstified zone was modeled using the assumption that it acts hydraulically similar to a granular, porous medium. As part of the calibration, the following hypotheses were tested: (1) karstic features play an important role in the groundwater-flow system; (2) a ring or belt of sinkholes in the area is a manifestation of a zone of high transmissivity that facilitates the channeling of groundwater toward the Gulf of Mexico; and (3) the geologic features in the southern part of Yucatan influence the groundwater-flow system. The model shows that the Sierrita de Ticul fault, in the southwestern part of the study area, acts as a flow barrier and head values decline toward the northeast. The modeling also shows that the regional flow-system dynamics have not been altered despite the large number of pumping wells because the volume of water pumped is small compared with the volume of recharge, and the well-developed karst system of the region has a very high hydraulic conductivity. Electronic Publication  相似文献   

The Mount Parnitha (Athens) Earthquake of September 7, 1999: A Disaster Management Perspective     

Pomonis  Antonios 《Natural Hazards》2002,27(1-2):171-199

Natural Hazards - Strong earthquakes in the proximity of densely inhabited urban areas pose one ofthe most complicated disaster management situations faced by societies today. Herethe experience...  相似文献   

Identifying and quantifying urban recharge: a review   总被引：12，自引：1，他引：12  

David N. Lerner 《Hydrogeology Journal》2002,10(1):143-152

The sources of and pathways for groundwater recharge in urban areas are more numerous and complex than in rural environments. Buildings, roads, and other surface infrastructure combine with man-made drainage networks to change the pathways for precipitation. Some direct recharge is lost, but additional recharge can occur from storm drainage systems. Large amounts of water are imported into most cities for supply, distributed through underground pipes, and collected again in sewers or septic tanks. The leaks from these pipe networks often provide substantial recharge. Sources of recharge in urban areas are identified through piezometry, chemical signatures, and water balances. All three approaches have problems. Recharge is quantified either by individual components (direct recharge, water-mains leakage, septic tanks, etc.) or holistically. Working with individual components requires large amounts of data, much of which is uncertain and is likely to lead to large uncertainties in the final result. Recommended holistic approaches include the use of groundwater modelling and solute balances, where various types of data are integrated. Urban recharge remains an under-researched topic, with few high-quality case studies reported in the literature. Electronic Publication  相似文献   

The gravity method in groundwater exploration in crystalline rocks: a study in the peninsular granitic region of Hyderabad, India     

B. Murty  V. Raghavan 《Hydrogeology Journal》2002,10(2):307-321

The application of variations in the earth's gravity in groundwater exploration on a regional scale, especially in sedimentary basins, metamorphic terrains, valley fills, and for buried alluvial channels, is well established. However, its use in hard crystalline rocks is little known. In granite, for example, the upper weathered layer is a potential primary aquifer, and the underlying fractured rock can form a secondary aquifer. Fracturing and weathering increases the porosity of a rock, thereby reducing the bulk density. Changes in gravity anomalies of 0.1–0.7 mGal for granites, due to weathering or variations in lithology, can be detected. To test the use of gravity as a groundwater exploration tool for crystalline rocks, a gravity survey of the peninsular shield granites underlying Osmania University Campus, Hyderabad, India, was undertaken. At the site, gravity anomalies reflect variations in the lithology and in the thickness of weathered zones. These anomalies also define the position of intrusives and lineaments. Areas of more deeply weathered granite that contain wells of higher groundwater yield are represented by negative gravity values. In the weathered zone, well yield has an inverse relation to the magnitudes of residual gravity. The study confirms the feasibility of gravity as a tool for groundwater exploration in crystalline rocks. Electronic Publication  相似文献   

A method to predict the group fissuring and faulting caused by regional groundwater decline     

E. Rojas  J. Arzate  M. Arroyo   《Engineering Geology》2002,65(4):20-260

Ground fissuring is a recurrent problem in many countries where water extraction surpasses the natural recharge of aquifers. Due to differential settlement, the soil layer undergoes deformation and cracks with serious consequences for civil infrastructure. Here, we propose an approximate analysis of the fissuring process that can be used to predict the location of cracks, which increasingly affect some middle- and large-sized cities in the world. For that purpose, the ground loss theory is applied to sediments overlying a sinusoidal-shaped graben. This analysis shows the existence of a tensile zone at the border of the graben with maximal values on its shoulder where tension cracks are more likely to appear. It also shows that soil deformation under differential settlement may evolve into ground faulting if water withdrawal continues. Finally, when a crack has completely developed, the tensile zone shifts towards the center of the graben, creating a new area for potential cracking and faulting.  相似文献   

山西水2井和岳42井水位记震能力分析   总被引：2，自引：1，他引：2       下载免费PDF全文

张子广  张素欣  郑云贞  王贺生 《地震工程学报》2002,24(3):262-266

对比分析了唐山地区同一地质单元内、同一观测含水层、水位动态相同的山西水2井和岳42井记录的水震波曲线，显示两井记震能力相差很大，从井孔结构、地震面波特性等方面分析了两井记震能力差异性的成因机理，结果表明，井孔的固有周期是影响水位记震能力大小的首要条件。  相似文献   

Processes in microbial transport in the natural subsurface     

Timothy R. Ginn  Brian D. Wood  Kirk E. Nelson  Timothy D. Scheibe  Ellyn M. Murphy  T.Prabhakar Clement   《Advances in water resources》2002,25(8-12)

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电阻率图像中的地下水和断层     

朱涛  冯锐  郝锦绮 《CT理论与应用研究》2002,11(4):43-49

目的：将电阻率层析成像应用于探测潜伏断层的研究中，本文发现了断层和地下水的一些基本电阻率分布特征，这对于工程物探意义重大，一般情况下，断层两侧具有不同的电阻率特征，但是，根据电阻率层析图像中的电阻率分布，通常难以区分断层和地下水层，这是因为两者不仅都具有低电阻率值，而且还具有非常相似的电阻率异常特征。资料和方法：运用电阻率层析图像的数据，电阻率层析图像中的断层会呈现如下特征：1）由于孔隙度的加大和地下水的存在，使得断层表现出高角度的低阻线性结构。它们既可以出现在浅部盖层中，也可以存在于深部基岩中，特别是在深部区域，它们尤为明显；2）它们还呈现出高角度的线性梯度带，在该梯度带两边的电阻率结构出现整体性的差异，通常情况下，正断层的上盘表现出低阻或／和班驳状的高阻和低阻扰动区，而下盘则为完整的高阻区，这与逆冲断层正好相反；3）与断层有关的电阻率异常区常常具有良好的大尺度水平连续性，并且可以追瞎异常区附近的精细电性结构。而地下水的电阻率特征为：1）如果没有裂隙，地表水所引起的低阻区非常浅，即使存在丰富的水源以及高孔隙度的砾岩和中粗砂。一般情况下，其底端深度不超过强风化区；2）地下水的电阻率值非常低，特别在高矿化度的地区。地下水，包括岩溶水和砂岩水，的电阻率总显示出局部水平延伸或／和面团状特征；3）地下水层的深度朝某个固定方向逐渐增加，并且其电阻率图像会随季节而变；4）一般情况下，在水下渗的地区，会出现降水漏斗，其上部为高阻，而下部为低阻，从而便形成了“Y”或“V”字型的典型结构。结果：利用上述的基本特征一般可以区分断层和地下水。结论：仅依靠电阻率层析图像，可能极难准确地区分断层和裂隙水，这是因为裂隙水不但可能具有高角度的低阻线性结构，而且在一定尺度上具有很好的水平连续性，还有，由于电阻率层析成像较差的垂直分辨率，难以精确确定断层的上端点位置，所以结合其它的物探手段如钻探和浅层地震勘探是非常必要的。  相似文献   

昆仑山口西8.1级地震的远程地下水动力学效应   总被引：3，自引：2，他引：3  

王道 《内陆地震》2002,16(3):213-223

对新疆北天山地区地下流体的动态观测资料进行分析 ,发现在 2 0 0 1年 11月 14日昆仑山口西 8.1级地震的震时和震后 ,多井水位、水温、流量出现大量异常变化 ,其特征主要表现为地震波的同震振动效应和震后阶跃变化。其中乌鲁木齐 10号井的地震波效应双振幅最大 ,为 185 mm,持续时间达 2个小时 ;0 4井水位阶跃上升幅度较大 ,为 0 .12 5 m,且具有不可逆特征。另外 ,对比了新疆及邻区 7级以上地震北天山地下水的震后效应 ,讨论了地下水远程效应与井震距离的关系以及阶跃异常的幅度等问题  相似文献   

干旱区地下水脆弱性特征及评价方法探讨   总被引：29，自引：18，他引：29  

马金珠  高前兆 《干旱区地理》2003,26(1):44-49

干旱区地下水脆弱性是地下水系统本身固有的不稳定属性，是系统结构、功能状态在人类活动干扰及气候变化等自然因素作用下具有的敏感性、易变性和弹性的综合反映。可以以河川径流中冰雪融水比重、地表径流入渗占地下水补给比例、地下水补给强度、地表水的引用率等十项指标（IRRUDQELTS）进行定量评价。通过对塔里木盆地南缘地下水脆弱性评价，表明该区属地下水严重脆弱区，其中又以民丰县、皮山县为极端脆弱，结果与实际情况相符合，说明该评价指标体系具有一定的科学性。  相似文献