Management of High Groundwater Level Aquifer in the Taipei Basin

Groundwater pumpings have been prohibited by the government since 1970 due to the overexploitation and severe land subsidence in the Taipei Basin. Declining water levels were gradually recovered back. Nowadays, high groundwater levels are developed in the Taipei Basin. This may cause safety problems such as seepage of underground facility, and liquefaction by the strong earthquake jeopardizing millions of people's lives and properties in the metropolitan area of Taipei. To reduce the associated risks, the study aims to formulate a management strategy to rationally reduce the groundwater level declining trend and sustainable utilization of groundwater resources in the Taipei Basin. A hydrogeologic model of Taipei Basin using MODFLOW-96 was setup to evaluate water budget and safe yield of the aquifer. The simulated water budget indicates that the groundwater annual storage increases about 17 million cubic meters in the main (Jingmei) aquifer. The average groundwater safe yield of the Taipei Basin estimated by the Hill method is about 54 million cubic meters per year. Moreover, with consideration of the reduction of liquefaction risks the revised average safe yield is about 126 million cubic meters per year. To effectively use and manage groundwater resources, restriction order on the use of groundwater resources in the Taipei Basin need to be revised. The implementation of groundwater management index coupled with an upper limit of the average groundwater level set as -7.5 m below the surface for avoiding earthquake caused liquefaction is suggested to manage the groundwater level for safe-use of groundwater resources in the Taipei Basin.