潮汐對近岸海水出滲量影響之模擬研究;Numerical Study of Tide Influences on Submarine Groundwater Discharge

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Title:	潮汐對近岸海水出滲量影響之模擬研究;Numerical Study of Tide Influences on Submarine Groundwater Discharge
Authors:	李唯祺;Li, Wei-Ci
Contributors:	應用地質研究所
Keywords:	近岸海水出滲;潮汐波;HYDROGEOCHEM;白努利定律;SGD;Tide wave;HYDROGEOCHEM;Bernoulli’s equation
Date:	2017-01-23
Issue Date:	2017-05-05 17:43:01 (UTC+8)
Publisher:	國立中央大學
Abstract:	為了探討海水與地下水在沿海含水層海灘坡面上之交互作用關係，本研究考慮海水水體移動時對於底下含水層之影響。本研究以漲退潮時的潮汐波作為研究對象，並探討潮汐波通過海灘坡面時造成之壓力差對於坡面下地下水滲出現象之影響。本研究選用 HYDROGEOCHEM (Hydrologic Transport and Geochemical Reactions Model) 數值模式，以探討潮汐波對於一理想斜坡非飽和二維海岸含水層之地下水出滲率影響。研究中假設海灘坡面為無摩擦力平面，基於白努利定律(Bernolli’s equation)，潮汐波通過時將會降低海灘坡面上的壓力，加上由於潮汐波傳遞速率較地下水流快上數倍，因此此效應便不可忽略。本研究考慮了數種情境以量化此效應對於海水出滲速率之影響，這些情境包括有海灘坡度、含水層水力傳導係數以及潮汐振幅等。研究結果顯示上部鹽水團的產生與消失和海灘坡面的出滲速度有關，而潮汐波的加入使潮間帶周圍的邊界出滲速度下降約50%，但低潮線以下區域的出滲速度則增加了約兩倍，出滲邊界往海移動的結果造成上部鹽水團體積增大並於使海水鹽楔移動至海洋邊界附近。;To investigate the interactions between seawater and groundwater in coastal aquifer, this study considered tide current may create pressure changes on interfaces of aquifer and seawater when tide falls and rises. A two-dimensional unsaturated aquifer was considered in this study, HYDROGEOCHEM (Hydrologic Transport and Geochemical Reactions Model) numerical model was employed to quantify the influences of ocean currents on output fluxes of Submarine Groundwater Discharge (SGD). Based on energy conservation equation (Bernolli’s equation), the pressure heads on beach surface will decreased by tidal currents. Due to the velocities of tidal currents are several orders of magnitudes greater than that of groundwater, this de are not negligible in this study. This study considered several scenarios to quantify the influences of tidal current on SGD, those scenarios including different beach slopes, hydraulic conductivity values and tide amplitudes. Simulation results show that the fate of Upper Saline Plume (USP) was relates to out flux rates on beach surface. Tide currents will decrease about 50% of out flux rates near intertidal zone and increase the out flux rates about 200% near seabed. This downstream movement of out flux point results in a larger volume of USP and retreat of SGD. Simulation results also show that relative to beach slope and hydraulic conductivity, tide amplitude is one of the factors to control the influences of tidal current on aquifer. The influences of tidal current will increases about 10% on out flux rate when the tide amplitude raising 0.5 meters.
Appears in Collections:	[Graduate Institute of Applied Geology] Electronic Thesis & Dissertation

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