Hydrogeological Investigations and Numerical Simulation of Groundwater Flow in the Karstic Aquifer of Northwestern Yucatan, Mexico
Hydrogeological Investigations and Numerical Simulation of Groundwater Flow in the Karstic Aquifer of Northwestern Yucatan, Mexico
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墨西哥尤卡坦半岛西北部岩溶含水层地下水流水文地质调查与数值模拟
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发表时间：
2003
期刊：
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通讯作者：
H. Essaid
中科院分区：
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作者：
B. Steinich;E. Perry;L. Marín;H. Essaid
在墨西哥尤卡坦半岛北方喀斯特平原的整个地下存在着一个淡水透镜，下面是咸水。水位记录在这个平原，在1987年6月至1989年4月期间，被用来绘制地下水位，确定内陆水文地质边界，并估计厚度的淡水透镜使用的Ghyben-Herzberg关系。尤卡坦半岛西北部大部分地区的地下水位比平均海平面高出不到两米。在研究期间，正常的干/湿季节变化约为0.5 m。Ghyben-Herzberg对淡水透镜厚度的估计范围从靠近海岸的18米到研究区域东南部的80米以上。采用一个将咸淡水流分隔为锐界面的准三维有限差分模型，对研究区地下水流进行了数值模拟。最能再现实测水位的概念模型是一个两层系统，一个深层的高水力传导率（1米/秒）覆盖着一层较低的水力传导率（0.1米/秒）。高导水率层对应于3.5万年至12万年前可能发生化学侵蚀的区域，当时海平面在低于目前水平约50米的水平上振荡。在一个浅的沿海弱透水层破裂的模拟表明，拟议的建设，这将导致这样一个突破，可能会导致尤卡坦平原的水资源大幅减少。引言尤卡坦半岛西北部的含水层包含一个淡水透镜，它漂浮在一个密度更大的盐水楔上方，渗透到内陆40多公里处（Back和Hanshaw，1970年; Durazo等人，1980; Back和Lesser，1981; Gaona等人，1985;佩里等人，1989年）。最近，它被证明可以穿透超过90公里（佩里等人，1995年; Steinich和Marín，1996年）。含水层，除了沿海岸沿着的狭窄地带外，是无压的（佩里等人，1989年），是唯一的淡水。
A freshwater lens underlain by saltwater exists beneath the entire northern Yucatan karst plain, Mexico. Water levels recorded in this plain, during the period June 1987 April, 1989, were used to map the water table, identify inland hydrogeologic boundaries, and estimate the thickness of the freshwater lens using the Ghyben-Herzberg relation. The water table under most of northwestern Yucatan is less than two meters above mean sea level. Normal dry/wet seasonal variations during the period of study were about 0.5 m. The Ghyben-Herzberg estimated thickness of the freshwater lens ranges from a low of 18 m near the coast to more than 80 m in the southeastern section of the study area. A quasi-three dimensional finite-difference model, in which freshwater and saltwater flow are separated by a sharp interface, was used to simulate groundwater flow in the study area. The conceptual model that best reproduces measured water levels is a two-layer system with a deep layer of high hydraulic conductivity (1 m/s) overlain by a layer of lower hydraulic conductivity (0.1 m/s). The layer of high hydraulic conductivity corresponds to a zone where chemical erosion probably occurred between 35 and 120 thousand years ago, when sea level oscillated around a level about 50 m below the present level. Simulation of a breach in a shallow coastal aquitard showed that proposed construction, which would cause such a breach, could result in a substantial reduction of the water resources of the Yucatan plain. INTRODUCTION The aquifer in northwestern Yucatan contains a freshwater lens that floats above a denser saline water wedge that penetrates more than 40 km inland (Back and Hanshaw, 1970; Durazo et al., 1980; Back and Lesser, 1981; Gaona et al., 1985; Perry et al., 1989). Recently, it’s been shown to penetrate more than 90 km (Perry et al., 1995; Steinich and Marín, 1996). The aquifer, which is unconfined except for a narrow band along the coast (Perry et al., 1989), is the sole freshwater