地層導熱係數是地下傳熱的基本重要控制因素，溫泉觀測井常有自湧現象，因而產生溫度的變化，利用此溫度差，可推求地層導熱係數。本計畫擬先在礁溪溫泉進行現地地層導熱係數研究，此方法確立後也可應用於其他溫泉區，各溫泉區或地熱區之開發，其溫度變化乃受到地層導熱係數之控制，了解地層導熱係數之空間分布，為溫泉地熱開發管理的基礎。 The determination of thermal diffusivity is a pre-requisite for geothermal site characterization and utilization. The temperature recovery (TR) method is a popular method for determining in-situ thermal conductivity together with the thermal response test and thermal conductivity probe methods. To determine in-situ thermal properties of the subsurface following a thermal disturbance produced by drilling processes or a heating cable within a borehole, the TR method is used to record decaying temperatures during the recovery period. However, to date, no studies exist to determine thermal diffusivity using up-welling water within a well. In this study, we introduce a 1D numerical method for estimating in-situ thermal diffusivity of the subsurface using up-welling thermal water as a heat source within an artesian well. Our numerical model includes parameters for the position of a sensor within a borehole, as well as for the thermal properties of a well casing and an annulus.