[S-GD01] Geodetic Advances in Crustal Dynamics and Environmental Change for Taiwan and Neighboring Regions

[SGD01-10] Analyzing Land Subsidence and Groundwater Depletion in Taiwan's Choushui River Alluvial Fan Using GNSS and Hydrogeological Techniques

*Wei-Chia Hung^1,2, Yi-An Chen¹, Shao-Hung Lin^1,3, Kuan-Chung Lin^1,2 (1.Green Environment Engineering Consultant Co. LTD, 2.National Yang Ming Chiao Tung University, 3.National Taiwan University)

Keywords:land subsidence, Global Navigation Satellite System (GNSS), groundwater, time series analysis

This study examines groundwater depletion and land subsidence in Taiwan’s Choushui River Alluvial Fan (CRAF) by integrating data from 233 groundwater monitoring stations and 50 GNSS stations. An automated GNSS processing system and time-series analysis were employed to monitor long-term trends and seasonal changes in groundwater levels and surface displacements. The analysis reveals significant hotspots of groundwater depletion and subsidence, particularly south of the old Huwei Creek, where the presence of highly compressible soils makes the region susceptible to subsidence from historical over-extraction of groundwater. There is a clear relationship between groundwater fluctuations and surface deformation, with both increasing from northeast to southwest. The area between the 78 Expressway and Puzi Creek is the most severely impacted, experiencing groundwater level declines of up to 0.54 meters per year and subsidence rates reaching 5.2 centimeters per year. These findings underscore the urgent need for targeted groundwater management strategies to mitigate subsidence in the CRAF region.