發展複合型地下水數值模式評析地下水資源開發及海水入侵

A Study on the Integrated Numerical Model of Groundwater Resources and Seawater Intrusion

張祉凱(Chi-Kai Chang)

指導教授 ： 譚義績

國立臺灣大學/生物資源暨農學院/生物環境系統工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201702557

摘要

屏東平原為台灣重要地下水資源使用地區，原以灌溉及家庭用水為主，近年來因養殖漁業發展蓬勃，台灣沿海地區競相引用地下水資源，導致需水量大增，過度抽用地下水的結果，造成地層下陷、海水入侵與土壤鹽化等問題。
為了解屏東平原海水入侵情況，本研究使用SWAT垂直補注模式、MODFLOW地下水流模式與MT3D溶質傳輸模式建置屏東平原之複合型地下水、海水入侵與水資源開發之數值評估模式。
本研究根據水利署氣候變遷之海平面上升境況與未來經濟成長下，抽水量增加之情境，模擬屏東平原因應外在條件改變下，地下水之氯鹽濃度變化。研究分為兩種模擬條件：情境一、探討於2020~2039年間，海平面上升總量分別27公分、40公分與54公分三個案例模擬，結果顯示，在維持現有的安全抽水量下，海平面上升在三個案例均對內陸氯鹽濃度並無明顯影響，對沿海地區而言，高濃度氯鹽則向內陸推進。情境二以經濟發展為前提，預測未來地下水抽水量增加分別以增加現有抽水量10％、20％與30％三個案例模擬，結果顯示，在第一含水層氯鹽濃度隨抽水量增大而有顯著的上升，第二含水層、第三含水層沒有隨抽水量增大而有明顯變化。
本研究建立之屏東平原之複合型地下水、海水入侵與水資源開發之數值評估模式，探討氣候變遷與需水量增加下之氯鹽濃度之時空變化，可因應未來經濟發展用水量增加對於水資源品質影響之評估，並提供政府執行管理與決策之參考依據。

關鍵字

SWAT ； MODFLOW ； MT3D ； 地層下陷 ； 海水入侵 ； 氣候變遷 ； 屏東平原

並列摘要

Pingtung Plain is an important area for the usage of groundwater resources, with irrigation and household as the main usage in the past. In recent years, the development of fishing industry starts to flourish, which causes a competitive utilization of groundwater resources in Taiwan’s coastal areas, resulting in groundwater overdraft and an increase demand in the needs of water, which leads to various problems such as land subsidence, seawater intrusion and salinization.

In order to explore the situation of seawater intrusion in Pingtung Plain, this research applies Soil Water Assessment Tool (SWAT), MODFLOW groundwater model and MT3D to stimulate the numerical model of integrated groundwater, seawater intrusion and the development of water resources in Pingtung Plain.

This study applies the external factors of Pingtung Plain provided by Water Resources Agency, to stimulate the change of chloride concentration in groundwater due to the increasing pumpage phenomenon causes by future economic growth and rise in sea level as climate changes. The study is divided into two simulation conditions:
i.To stimulate in 2020 to 2039, the rise in sea level in 3 different cases: 27cm, 40cm and 54cm. The stimulated result has shown that, under the current pumping situation, the rise in sea level in the mentioned cases has no significant effect towards the inland chloride concentration. However, the high concentration of chloride in coastal area moves towards inland.
ii.Based on the future economic development, predict groundwater pumpage will respectively increase by 10%, 20% and 30% over the existing percentage. Result has shown that, the chloride concentration in the first aquifer has a significant growth as pumpage increases. However, the second and third aquifer has no significant changes as pumpage increases.

The numerical model of integrated groundwater, seawater intrusion and water resources development set up in this research investigates the spatiotemporal changes of chloride concentration as climate changes and water demand increases. This model can examine the affects towards the quality of water resources as the increase usage in water amount due to future economic development, and act as a reference for the government in decision making and implementation.

並列關鍵字

SWAT ； MODFLOW ； MT3D ； land subsidence ； seawater intrusion ； climate changes ； pingtung plain

參考文獻

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