東港溪流域位於屏東平原，流域內擁有豐富的地下水資源，該區習慣取用地下水做為用水的來源，因此，如何有效率的管理地下水資源為重要的課題。本研究欲藉由河床出入滲試驗與數值模擬來探討東港溪流域內河川與地下水之間的交互關係，以提供水資源永續經營之參考。 本研究進行河川出入滲試驗與蒐集流域內的水文觀測資料，以及彙整流域內的地質鑽井資料進行地質統計分析，建立異質性水文地質模型，並使用地下水模擬系統(GMS)整合相關資料，建立地下水流數值模式來進行地下水與河川交換的季節性特徵探討。現地試驗的結果顯示，東港溪沿岸主要為地下水出滲，河床傳導度介於2.34×10-8~1.37×10-3 m/s之間，數值分布呈現上游高而下游低的態勢。根據鑽井地質材料比例，流域的主要材料為礫石(佔比約為40%)，玫瑰圖分析顯示，地質材料主軸連續方向與河川主流方向相似，顯示該區域沉積環境與河川有相關性。地下水流數值模式結果顯示，乾季的地下水出滲變化與前一濕季的降雨總量有關。濕季的地下水出滲量變化除了與降雨總量有關外，亦與當季的降雨雨型有關。率定完成的數值模式結果顯示，研究區的東港溪段主要呈現地下水出滲，與現地試驗的結果相符合。 ;Donggang River Watershed is located in Pingtung Plain where the water resources are mainly from groundwater system. Land subsidence thus is a serious problem in the coastal area due to groundwater over-exploitation. Therefore, it is important to investigate the groundwater and river seasonal interaction in the study area for the management of groundwater resources. This study aims to investigate the interactions between river water and groundwater in the Donggang River Watershed by using river recharge and discharge experiments and numerical simulation. The study results can provide a reference for the sustainable management of water resources in the study area. To overcome the uncertainty from riverbed conductance and hydrogeological model, this study conducted riverbed infiltration experiments in different segments of Donggang River and collected geological drilling data in the study area to construct a heterogeneous hydrogeological model. The field experimental results show that groundwater mainly discharges to river in the study area. The riverbed conductivity ranges from 2.34×10-8 to 1.37×10-3 m/s, and the quantities decrease from upstream to downstream. A heterogeneous hydrogeological model has been established based on the collected geological boreholes. According to the proportion of materials from drilling data, gravel is the majority material in the watershed (approximately 40%). The rose diagram analysis for the continuity of geological materials illustrated that the principal direction is similar to that of the river flow. It shows that the continuity of geological materials matches the sedimentary environment of Donggang River. A numerical model integrates the relevant data by using Groundwater Modeling System (GMS) to discuss the seasonal pattern of interaction between groundwater and river. The results showed that the quantity of river discharge in the dry season is mainly affected by the total amount of rainfall in the previous wet season. The river discharge quantity during the wet season is influenced by not only the total amount of rainfall but also its seasonal pattern. The calibrated results of the numerical model show that Donggang River in the study area is mainly under a groundwater discharge situation, as the experimental results of riverbed infiltration.
