Assessment of artificial riverbed recharge based on gravity investigation

Taiwan is grappling with a severe water scarcity issue, making the development and utilization of groundwater resources a critical national concern. In recent years, Taiwan's Water Resources Agency has been actively promoting the artificial recharge of groundwater resources in the Pingtung Plain to meet the increasing demands for domestic and industrial water use. This study focuses on five riverbed recharge facilities in the Pingtung AiLiao and Laonong River basins. A novel technique utilizing gravity methods to evaluate groundwater recharge volumes. This study utilizes gravity observations to directly monitor changes in groundwater storage, overcoming previous limitations associated with relying solely on monitoring wells to estimate groundwater recharge volumes. The study established two absolute and twelve relative gravity stations to collect data on variations in gravity over time and under different rainfall conditions. Preliminary results indicate that the average gravity value decreased by approximately 21 μgal over a 1.6 km2 area in December 2023, within a period of 3 weeks. The equivalent change in water volume will be verified with additional in-situ data. This research aims to compare the efficiency of recharge among different riverbeds in order to assess the applicability and limitations of this technique. Furthermore, we anticipate that this study will contribute to the dissemination of geodetic surveying techniques and their potential application in various hydrogeological and water resource fields.