A radon monitoring system capable of continuous real-time monitoring of well gas radon was devised and tested in a climate change observation network. It comprised a radon detector and could help observe the groundwater in a well, blocking the inflow of outside air. The water temperature, electrical conductivity, and water level were also monitored in the groundwater well. The temperature and electrical conductivity were almost constant within a 1% error range in both the 5-day preliminary and the 7-month long-term tests. The groundwater level appeared to be related to radon concentration, and tidal forces may have influenced both radon concentration and groundwater levels. [ABSTRACT FROM AUTHOR]