台中盆地地下水流數值模式之建立

Establishment of Groundwater Conceptual and Simulation Model in Taichung Basin

陳希軍(Hsi-Chun Chen)

指導教授 ： 徐年盛

國立臺灣大學/工學院/土木工程學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.01326

摘要

本研究以台中盆地為研究對象，彙整歷年來台中盆地之地質鑽探、地下水觀測網量測、抽水量與補注量調查分析資料，針對台中盆地地下水系統提出水平衡概念模式及地層分層概念模式，用於水平衡分析與地下水流數值模擬模式建置，以合理評估台中盆地地下水系統蓄水量、抽補量之時間與空間分布情形。
台中盆地之邊界北側以大甲溪為界，此邊界除河水補注外另有河道北岸地下水補注、東側車籠埔斷層及西側大肚山、八卦山背斜為零流量邊界、南側以地下水分水嶺為界，但由於此邊界具變動性，故以新光井設定為已知水頭邊界；含水層特性以粗顆粒之砂石及卵礫石為主，地下水系統概念分層包括含水層一、阻水層一與含水層二，阻水層一僅於霧峰、烏日地區附近。地下水受大尺度降雨之影響，每年穩定呈現乾季時水位下降、雨季時水位上升之變化。盆地內各方向之地下水流均匯集於烏溪下游隘口流出。
本研究結合土地利用、土壤特性、雨量、人為灌溉等因子，合理評估補注量之空間分布，並將水平衡分析與數值模式結合，透過穩態模式掌控流場以及抽水量與補注量空間分布；再以暫態模式評估各水文量(河道出入滲補注、雨水灌溉補注、區外流入、隘口地下水流出)隨時間之變化情形，同時探討各水文量間之相互關係及時間稽延。
研究結果顯示，2008~2010年平均補注量約15.15億噸，其中雨水灌溉補注佔38%、河道入滲補注佔41%、南北兩側地下水入流佔21%。平均年流失量約11.33億噸，其中地下水出滲河道損失佔68%，隘口地下水流出佔32%；年抽水量約為3.90億噸，年蓄水變化量平均為-0.08億噸，年淨補注量平均為3.82億噸。補注量以烏溪沿岸最豐沛，台中市區最少，抽水量則以西屯區最大；由各水文量與時間稽延關係，發現暴雨過後地下水持續出滲至河川導致流失，未來若能妥善運用此特性，將可達劫豐濟枯之效用。

關鍵字

台中盆地 ； 地下水 ； 地下水歷線法 ； 模擬模式 ； 抽補量

並列摘要

In this research, we collected the data of Taichung Basin, including geological drilling, groundwater levels, pumping and recharge. Through water budget and conceptual model, we can develop the Taichung Basin groundwater numerical model and estimate the pumping and recharge of Taichung Basin.
Tachia stream is the north boundary of Taichung basin, In addition to stream leakage, this boundary has groundwater recharge of the north shore of the river. The east of the Chelungpu, the west side of the Tatu mountain, and the anticline of Bagua mountain are nonflow boundary . The groundwater drainage divide is used to be the south boundary. However, because the boundary is variability, we set the Xinguang well to be the transient head.
The aquifer is mainly formed with coarse-grained materials like gravel and sand. The hydrogeology of Taichung Basin is divided into two aquifers and one aquitard, for a total of three hydrogeological stratifications. The variation of groundwater level with a rise during wet period and a fall during dry period is influenced by the intensity of rainfall. All groundwater flows through the Wuxi downstream pass as the only exit of Taichung Basin.
This study combines the factors of land use, Land use, soil characteristics, rainfall, artificial irrigation. Assessment of the spatial distribution of the recharge reasonably, and combines water balance analysis and numerical model. Control field and the spatial distribution of the pumping and recharge through steady-state mode. Assess hydrology amount change situations as time goes by transient mode, and discuss the interrelation and lag time between hydrology amount.
The results show from 2008~2010 the averaged annual recharge is 1515 million tons, the annual pumping is 390 million tons, the storage change is -8 million tons, and the loss is 1133 million tons. The largest amount of recharge occurs along the banks of Wuxi River, while the least recharge takes place at Taichung urban area. As for the amount of pumping, Situn District is with the most serious pumpage. We found the groundwater run off because it was still seepage to the stream after the storm by the relationship between hydrology amount and lag time.If we can use this feature for doing recharge in the future, we can get the result of best.

並列關鍵字

Taichung Basin ； groundwater ； groundwater hydrograph analysis ； simulation model ； pumping and recharge

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