Analysis of an Unconfined Aquifer Subject to Asynchronous Dual‐Tide Propagation
Analysis of an Unconfined Aquifer Subject to Asynchronous Dual‐Tide Propagation
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DOI：
10.1111/j.1745-6584.2007.00412.x
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发表时间：
2008-03
期刊：
影响因子：
2.6
通讯作者：
K. Rotzoll;A. El-Kadi;S. Gingerich
中科院分区：
文献类型：
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作者：
K. Rotzoll;A. El-Kadi;S. Gingerich
大多数已发表的含水层对海潮响应的解决方案都集中在信号在内陆传播时的单侧衰减上。然而，岛屿含水层经历来自整个海岸的周期性强迫，这可能导致不同潮汐信号的综合效应，特别是在狭窄的高渗透岛屿上。一般来说，研究忽略了海啸席卷岛屿时潜在的时间滞后。我们提出了在相对边界上受异步和非对称振荡水头条件影响的地下水流动方程的一维解析解，并在毛伊岛一个无约束火山含水层的数据上进行了测试。该方案考虑了海岸线上的泥沙阻尼效应。毛伊岛含水层的响应表明，含水层中心附近的地下水位高度受到来自对面海岸的潮汐组合的影响。与单面解相比，双面解能使观测到的地下水头与理论响应更吻合。水力扩散系数估计为2.3 × 107 m2/d。假设比产率为0.04，含水层厚度为1.8 km，这意味着水导率为500 m/d。数值实验证实了水力扩散系数值，并表明回归估计的模态衰减和相位差的y截距可以近似于边界处低渗透率单元引起的阻尼因子。
Most published solutions for aquifer responses to ocean tides focus on the one‐sided attenuation of the signal as it propagates inland. However, island aquifers experience periodic forcing from the entire coast, which can lead to integrated effects of different tidal signals, especially on narrow high‐permeability islands. In general, studies disregard a potential time lag as the tidal wave sweeps around the island. We present a one‐dimensional analytical solution to the ground water flow equation subject to asynchronous and asymmetric oscillating head conditions on opposite boundaries and test it on data from an unconfined volcanic aquifer in Maui. The solution considers sediment‐damping effects at the coastline. The response of Maui Aquifers indicate that water table elevations near the center of the aquifer are influenced by a combination of tides from opposite coasts. A better match between the observed ground water head and the theoretical response can be obtained with the proposed dual‐tide solution than with single‐sided solutions. Hydraulic diffusivity was estimated to be 2.3 × 107 m2/d. This translates into a hydraulic conductivity of 500 m/d, assuming a specific yield of 0.04 and an aquifer thickness of 1.8 km. A numerical experiment confirmed the hydraulic diffusivity value and showed that the y‐intercepts of the modal attenuation and phase differences estimated by regression can approximate damping factors caused by low‐permeability units at the boundary.