The chemical composition of Tattapani thermal springs, together with the experimental results on host rock-meteoric water interaction at 100 degrees C, indicate dissolution of K-feldspars and albite during the initial stages of reaction. These phases control the chemical composition of the thermal springs. The estimated reservoir temperatures range from 205 to 217 degrees C. Assuming an average thermal gradient of 80 degrees C/km, the minimum depth of the reservoir is estimated to be around 3 km.