The temporal and spatial distributions of precipitation are extremely uneven, so making careful management of water resources in Taiwan is crucial. The long-term over-exploitation of groundwater resources poses a challenge to water resource management in Taiwan. However, assessing groundwater resources in mountainous basins is challenging due to limited information.The principal objectives of this book are to investigate the groundwater resources in mountainous basin through a set of detailed case studies. This book is mainly divided into three major parts including: (1) groundwater recharge estimation; (2) groundwater recharge potential zone mapping; and (3) groundwater recharge characteristics evaluation. Evaluating the hillslope hydrology can help determine the groundwater recharge characteristics in Taiwan’s mountain region for the goal of water resource protection.