The experimental field is located on the coast of the Japan Sea and in the north of Fukui prefecture. Some experiments with regard to the aquifer thermal-energy strage (ATES) have been carried out in the field for several years and the characteristics of these experiments were as follows;
(1) It was not the recharge through well, but the water spreading with some ditches that was adopted for the artificial recharge.
(2) Reservoir for heat and water was an unconfined aquifer and was located shallow depth below the surface.
(3) Recharge water used for these experiments was river water and it was naturally heated to an average temperature of 25t in summer.
The following are mainly identified by examining the heat balance of aquifer and by trying to compare the observed heat data with the approximate values that were lead from the simplified analytical models.
(1) The principal factor concerning the loss of heat in reservoir was the heat dispersion in aquifer caused by natural groundwater streams at this field.
(2) The heat conduction models are efficient for estimationg the change of heat capacity in the. aquifer after recharge.