[A-HW21] Surface and subsurface hydrologic models: Technical advances and applications for water management

[AHW21-P08] Heat tracer and numerical approaches to quantify submarine groundwater discharge in the coastal aquifer in Taoyuan, Taiwan

*Chia-Yu Hsu¹, Chuen-Fa Ni¹, Yu-Huan Chang¹, Chi-Ping Lin², YI-JING CHEN¹, Hsin-Po Wang¹, AN-YI HSU¹ (1.Graduate Institute of Applied Geology, National Central University, 2.Center for Environmental Studies, National Central University)

Keywords:Heat tracer method, Groundwater flux, Pumping strategies management

The increase in global water consumption is mainly owing to urbanization, growing agricultural activities, population growth, economic development, and improving living standards. Forcing the water resource authority concerned to seek new water resources to catch up with the gap of growing demand. Groundwater recharged from coastal aquifers to the ocean is a potential alternative water resource have drawn more attention in recent years. To use this resource more efficiently, a systematically assess of the groundwater system is necessary to prevent further influence on the groundwater system and proposed groundwater resources management strategy for this region to achieve sustainable development of groundwater management. In this study, we aim to quantify the groundwater flux in coastal areas and response to the groundwater extraction operation. The heat tracer method was applied to estimate groundwater flux by using the DTS system to acquire high-resolution temperature variation of the aquifer system. The parameters such as hydraulic conductivity and thermal conductivity are obtained through laboratory test. The FEFLOW model was selected to conduct the simulation, and the model is calibrated and validated based on the long-term observation of water level, hydrogeological parameters, temperature field, thermal conductivity, and tidal cycle. The groundwater flux results from the heat plus test match with the core samples, the groundwater flux of 0 m to 40 m and 40 m to 100 m are 3.61 m/min and 1.41 m/min respectively. The estimated unit-width groundwater discharge within 100 m depth is 223 m²/min. The model was calibrated and validated by the results from field tests to analyze the groundwater flow conditions of the aquifer under different pumping strategies and the relationship between seawater and freshwater in the coastal aquifer.