| 摘要: | 本研究以臺灣南部之美濃與旗山地區為對象，探討其地下水資源之分布與變化，並評估農業用水與天然補注對地下水系統之影響。由於臺灣南部為典型農業聚落，且因臺灣降雨時空分布不均，長期抽取地下水用於灌溉，導致地下水資源面臨日益嚴峻的挑戰。為量化區域地下水之實際影響，本研究應用MODFLOW數值模式進行地下水流動模擬，並結合實際水位資料進行模式檢定及驗證，藉以建立具代表性與穩定性之地下水分析模式。
利用土地利用、河川、降雨、抽水和地層鑽探等資料，建立MODFLOW地下水數值模式用以分析農業用水對美濃、旗山地區地下水資源之影響。並不同情境模擬分析，包括現況條件、無農業回滲水條件、農業抽水減少25%及無農業區條件，評估各項情境對地下水位之變化趨勢與空間分布之影響。模擬結果顯示，相較於現況(含農業和農業抽水)條件，農業用水減少25%情境下之地下水位已有回升情形，但相較現況較不顯著，而在無農業之情境下，地下水位面約會相較於有農業(現況)之情境回升約0.5m至1m。顯示農業用水確實導致地下水位下降，惟農業回滲水對地下水位具有明顯之補注效果，能部分緩解抽水造成之壓力。此外，雨量入滲也同為地下水位波動之重要因素，顯示未來極端氣候條件下，地下水補注能力可能面臨挑戰。
;This study focuses on the Mino and Qishan areas in southern Taiwan to investigate the distribution and variation of groundwater resources and to evaluate the impacts of agricultural water use and natural recharge on the groundwater system. Southern Taiwan is a typical agricultural region where uneven temporal and spatial rainfall distribution has led to long-term groundwater extraction for irrigation, posing increasing challenges to groundwater sustainability. To quantify the actual impacts on regional groundwater, the MODFLOW numerical model was applied to simulate groundwater flow, and the model was calibrated and validated using observed groundwater level data to establish a representative and stable groundwater analysis model.
Using data on land use, rivers, rainfall, pumping, and geological drilling, a MODFLOW model was constructed to assess the effects of agricultural water use on groundwater resources in the Mino and Qishan areas. Several scenarios were simulated, including the current condition, a condition without agricultural return flow, a 25% reduction in agricultural pumping, and a condition without agricultural areas. The simulation results indicate that, compared to the current condition (with agriculture and agricultural pumping), groundwater levels rise slightly under the 25% pumping reduction scenario, though the increase is not significant. In the no-agriculture scenario, groundwater levels rise by approximately 0.5 to 1 meter compared to the current condition. These results suggest that agricultural water use contributes to groundwater level decline, while return flow from agriculture provides a significant recharge effect that partially offsets the pressure caused by pumping. In addition, rainfall infiltration is also an important factor influencing groundwater fluctuations, implying that groundwater recharge capacity may face challenges under future extreme climate conditions. |
