Mechanism of water level rising during pumping from a deep geothermal well in a coastal aquifer

Groundwater levels rarely rise during pumping and the mechanism is not yet fully understood.This rare phenomenon has been observed during pumping at a deep geothermal well located approximately 1 km from the western coastline of Seokmo-do Island, Korea.To elucidate the mechanism behind the water level rising, we considered the effects of water density and static water pressure.We also analyzed the relationships between water level and tidal efficiency, as well as those between flowing water temperature and the volume of naturally flowing water at the surface.During pumping from the geothermal well, the temperature at the depth of 9 m increases, leading to a continuous decrease in water density and a corresponding rise in water level.Once the natural flow begins, the water temperature within the well consistently rises with the increasing rate of the natural flow.When the temperature of the natural flow water reaches approximately 65.5C, the natural flow rate increases to around 1,441 m 3 /d.Using a simplified formula for transmissivity and maximum drawdown during steadystate, long-term pumping in the confined aquifer, we calculated that the water level would be 12.373 m above the land surface at a natural flow rate of 1,441 m 3 /day.