This study involved the examination of the water balance of the groundwater basin functioning as the source for municipal water supply and the feasible groundwater intake volume, and also the preparation of the revised Third Groundwater Utilization Basic Plan.
On Miyakojima Island, the supply of drinking water almost relies exclusively on groundwater and a stable supply of drinking water is a great challenge for the island. In this work, boring and electric prospecting were conducted to clarify the aquifer structure and state of salt water incursion. A field survey was also conducted at sugar cane fields, etc. to observe the level of evapotranspiration. Based on the results of this field survey, a numerical analysis model was developed to calculate the feasible volume of groundwater intake. Moreover, the work examined whether groundwater could be used in a sustainable manner under changing climate conditions due to global warming. Based on the results of the study, the Third Groundwater Utilization Basic Plan was revised.