Large-scale hydraulic conductivity distribution in an unconfined carbonate aquifer using the ocean tidal propagation
Large-scale hydraulic conductivity distribution in an unconfined carbonate aquifer using the ocean tidal propagation
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DOI：
10.1007/s10040-021-02366-4
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发表时间：
2021-06
影响因子：
2.8
通讯作者：
Heejun Yang;Y. Tawara;J. Shimada;M. Kagabu;A. Okumura
中科院分区：
文献类型：
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作者：
Heejun Yang;Y. Tawara;J. Shimada;M. Kagabu;A. Okumura
基于15口威尔斯井和海平面地下水位观测资料，采用互谱分析、解析解和密度相关地下水模型相结合的方法，对日本南大东隆起环礁的碳酸盐含水层的导水率进行了评价。根据岛屿形态和海潮向内陆传播的情况，将岛屿地区划分为10个分区。通过假设两个含水层厚度（300和1，800 m）和两个有效孔隙度（0.1和0.3），使用基于各井海潮M2分量相位滞后的分析解，获得了每个分区的水力传导率。依赖密度的地下水模型通过再现观测到的地下水位来评估分区的水力传导性。在含水层厚度为300米、有效孔隙度为0.1的情况下，各分区的导水率估计为3.46 × 10− 3至6.35 × 10− 2米/秒，在含水层厚度为1 800米、有效孔隙度为0.3的情况下，导水率估计为1.73 × 10− 3至3.17 × 10− 2米/秒。南部和北方地区土壤水分含量较高，内陆低地高于西部和东部地区。岛屿上裂隙和白云岩的分布控制了全方位海洋潮汐传播的差异，并导致导水率的差异。这项研究所用的方法也可适用于其他小岛屿，很少或没有数据的水力传导率。
The hydraulic conductivity of an unconfined carbonate aquifer at the uplifted atoll of Minami-Daito, Japan, was evaluated by a combination of cross-spectral analysis, analytical solution, and density-dependent groundwater modeling based on observed groundwater levels in 15 wells and at sea level. The island area was divided into 10 subregions based on island morphology and on inland propagation of ocean tides. The hydraulic conductivity was obtained for each subregion using analytical solutions based on phase lags of M2constituents of ocean tides at each well by assuming two aquifer thicknesses (300 and 1,800 m) and two effective porosities (0.1 and 0.3). The density-dependent groundwater model evaluated the hydraulic conductivity of the subregions by reproducing observed groundwater levels. The hydraulic conductivity in the subregions was estimated as 3.46 × 10−3to 6.35 × 10−2m/s for aquifer thickness of 300 m and effective porosity of 0.1, and as 1.73 × 10−3to 3.17 × 10−2m/s for aquifer thickness of 1,800 m and the effective porosity of 0.3. It was higher in southern and northern areas, and higher in interior lowland than in the western and eastern areas. Fissures and dolomite distributions on the island control differences of the omnidirectional ocean tidal propagation and cause these differences in hydraulic conductivity. The method used for this study may also be applicable to other small islands that have few or no data for hydraulic conductivity.