應用地面地下水耦合數值模式推估地面地下交互作用量-以台中盆地為例

地下水流動為整個水文循環之一部分，其與地面水文密切相關，因此若欲較完整模擬地下水系統之變化，尤其是降雨補注及河川與地下水互動的問題，一個可完整考量降雨所產生之地面與河川逕流，以及降雨入滲機制的地面地下水耦合數值模式乃是必需。其中SWAT-MODFLOW模式整合了兩種在地面水及地下水皆各自為最被廣泛應用的模式，惟由於涵蓋範圍廣，因此實際應用時，資料準備不易，尤其是SWAT模組所需之地面相關資料，常需大量前置分析與處理，始能滿足模式需求。因此本研究乃以SWAT-MODFLOW模式為基礎，建立SWAT-MODFLOW模式之整體應用流程，其中包括建立SWAT模式之資料前置處理流程，以及整體SWAT-MODFLOW模式之參數檢定步驟，並應用於台中盆地。其中SWAT模式所需之土地利用及土壤相關參數資料種類繁多，於應用時資料常不易收集齊全，本研究乃發展資料補遺之方法與流程。另外，SWAT與MODFLOW模式各自有參數檢定模組支援，惟並無整體SWAT-MODFLOW模式之參數檢定模式，因本研究乃整合兩模式各自之參數檢定模組發展SWAT-MODFLOW模式之整體參數檢定流程。分析結果顯示，台中盆地SWAT模式推估之年平均補注量約為1.36億立方公尺，為此區域年平均降雨量之0.21倍。河川與含水層交換率部分，在進入台中盆地上游區段以河川入滲至含水層為主，靠近下游及至隘口區段則以含水層出滲至河川為主。綜合以上，本研究解決SWAT-MODFLOW模式於實際應用時常遇之困難，使其更易於實際問題之應用，有助於提升地下水模擬分析之完整性，尤其是地面與地下交互作用量及降雨入滲之之分析推估。

關鍵字

台中盆地； SWAT ； MODFLOW ；耦合數值模式；地面地下交互作用量

並列摘要

Groundwater flow is a part of the hydrologic cycle and is closely related to the surface hydrology. Rainfall recharge and rivers interaction with groundwater are important factors. Establishing a coupled surface and subsurface Model can consider physical mechanisms of rainfall infiltration and runoff. The soil water assessment tool (SWAT) and the groundwater flow model (MODFLOW) are integrated into the coupled SWAT-MODFLOW model. This study is based on the coupled SWAT-MODFLOW model and develops a process of building the model. Data pre-processing of the SWAT model and parameters identification steps are included. Then we apply the coupled SWAT-MODFLOW model in the Taichung basin, Taiwan. Land surface and soil hydrological processes can be simulated by the SWAT model. However, it needs many parameters, and parameters of primary data are not adequate in Taiwan. Therefore, we develop a process of data supplement and data analysis methods. It can improve the applicability of the SWAT model in Taiwan. The SWAT model and the MODFLOW model have already had parameters identification module separately. On the other hand, the coupled SWAT-MODFLOW model doesn’t have parameters identification module. Accordingly, we develop a process of overall parameters identification for the coupled SWAT-MODFLOW model. Results show the average annual groundwater recharge is 136 million m3/s and is 21% of the average annual precipitation. River and groundwater exchange rates reveal high spatial variability. In the upstream segment of rivers entering the Taichung basin, rivers recharge to aquifers. On the contrary, in the downstream segment of Wu River locates nearby the outlet of the Taichung Basin, groundwater discharges to rivers. In conclusion, if the SWAT-MODFLOW model can be applied to the watersheds of Taiwan, the proposed method can provide crucial information for further groundwater study.