以數值模擬評估濁水溪沖積扇北彰化地區之地下水水文細節及人爲抽水分佈

Estimating Groundwater Details and Pumping Distribution in North Cho-Shui Alluvial Fan by Numerical Modeling

林時猷(Shih-Yu Lin) ； 許少華(Marko Shao-Hua Hsu)

《農業工程學報》 50卷3期 (2004/09) Pp. 48-58

https://doi.org/10.29974/JTAE.200409.0004

摘要

濁水溪沖積扇之降雨時空分佈不均，瞭解當地抽水及補注之時空分佈情形，是地下水資源管理上必要的資訊。本研究利用PMWIN來評估其地下水文收支狀況，將濁水溪沖積扇彰化北區分成七層扇狀的剖面，並參考現地觀測井間之空間相關性與水文地質屏狀圖，相關性高且地質岩性相近之區域劃爲同一水文地質參數區，4層含水層共35個分區。文中使用PEST模組先進行水文地質參數K值之推估，再以暫態模擬進行S值之微調，使民國84年模擬與濁水溪沖積扇含水層各分層之觀測井記錄實際資料吻合。模式所得之水平衡，民國84年之年總抽水量爲155.4百萬立方公尺，降雨入滲補注量爲81.3百萬立方公尺，上游之側流補注量18百萬立方公尺，可知該年抽水量明顯超出地下水補注量之1.5倍。文中除將各鄉鎮的分層相對抽水量以圖示表現以外，並將扇頂、扇央與扇尾之地下水流相互補注情形圖示出來。其中僅扇尾之含水層三有淨向上層之補注量，其餘含水層皆是補注向下層的多。敏感度分析顯示本系統因屬超抽狀況，抽水量及最敏感之變量，上下調整20%則會影響地下水位20%的振幅。包括垂向滲漏的水文地質參數若上下調整20%，則使地下水位變動5~10%。氣象水文量的降雨入滲與蒸發則對模式影響較不敏感。

關鍵字

地下水 ； 模擬 ； 抽水 ； MODFLOW

並列摘要

Assessing pumping amounts and all fluxes in groundwater flow is an essential support toward good management of regional water resources, especially in the Cho-Shui alluvial fan area, where rainfall is extremely seasonally uneven. In this study, PMWIN (a 3D groundwater model) was employed to simulate groundwater flow and estimate water budgets of the north part of Cho-Shui alluvial fan. Correlation analysis features of water-table records from multi-layers were utilized to divide suitable sub-regions. An inverse model, PEST, was used to estimate hydraulic conductivity of each layer. Calibration and verification were performed according to multi-layer records of groundwater table of 1995 to 1996. Results indicate that in year 1995, the cumulative pumping volume is 155.4 million cubic meter, the rainfall recharge is 81.3 million cubic meter, and the constant head inflow is 18 million cubic meter. Sensitivity analyses indicate that pumping rate is the most sensitive variable.

並列關鍵字

Groundwater ； Modeling ； Pumping ； MODFLOW