台灣受到降雨時空分布不均及全球氣候變遷的影響，使得枯水期發生乾旱情況變得更加頻繁。在面臨乾旱時，因地下水具有水質乾淨且不易受豐枯水期影響的特性，故可做為抗旱水資源以降低災害損失。為有效規劃乾旱時期地下水資源管理，擬利用氣候預報資訊以掌握未來地下水的變化狀況，藉此增加地下水資源調配措施效益以降低乾旱造成的衝擊。 本研究選定台灣北部鳳山溪流域作為研究區域，建立該流域耦合地表與地下水模型WASH123D，透過降雨事件的校準與驗證，顯示在本研究水文模式參數的建置下，模擬地下水季變化趨勢與觀測值相符，因此可用於後續季節性推估之研究。以近年2015年和2017年乾旱事件作為探討，採用中央氣象局發布之季長期天氣預報，並結合氣象合成模式(WGEN)進行季節性降雨預報，將之作為水文模式WASH123D氣象輸入，以模擬季節性地下水位之預測。研究結果顯示降雨預報準確與否，會直接影響未來季節性地下水位預估的準確度，但在季預報預測與實際區間相同的情況下，多可以掌握地下水位變化趨勢，故利用季長期天氣展望預估地下水位之方法可提供有效的訊息以供地下水資源管理應用。 ;The management of water resources in Taiwan are under considerable challenges due to severe climatic conditions and uneven spatio-temporal distribution of rainfall. As a result, the drought in the dry season likely to become more frequent over northern Taiwan. Here, the management of groundwater has a particular interest due to reliable and clean water source. In order to effectively manage groundwater resources during the drought, this study proposed a methodology to incorporate seasonal climate forecasting as input in hydrological models. The study area comprised of Fengshan Creek basin (250 km2) in northern Taiwan. A coupled surface water and groundwater model, WASH123D, was applied to simulate the seasonal groundwater levels. The simulation results reasonably approximate observed measurements for 2015 and 2017 historical rainfall event. The rainfall forecasting for drought events of selected years was generated from seasonal outlook issued by Central Weather Bureau of Taiwan (CWB) incorporated with weather generator (WGEN) and used as input for WASH123D. The seasonal outlook results showed that, the total amounts of rainfall were accurately modeled but unable to capture the occurrence of extreme events which directly lead to inaccuracy for the prediction of seasonal groundwater levels. This study indicated that, the proposed approach provided valuable information for groundwater resource management and the prediction of groundwater level are sensitive to the accuracy of seasonal outlook.
