In the paper we present the Impulse Response Function Thermal Analysis (IRFTA) model and its application to leakage detection by analysis of temperature measured in the body of earth dam or dike of the canals. This method bases on theory of Green's function that is applied to coupled heat and water transport description. Direct leakage flow or even only variation of humidity of the soil due to seepage presence, influence on heat transport in the soil. In consequence IRFTA model application for the parametrical description of heat transport, allows for analysis of water transport in dike or dam. In consequence we can identify leakages but also we can analyse even small seepage changes and estimate intensity of this process. It is possible due to fact that IRFTA model is not only statistical model but its parameters have physical definition. Application of IRFTA model is predicted for the distributed fibre optic temperature measurements, especially for a sensor installed in the downstream toe of the earth hydraulic structure, close to the upstream face. By this way a system of thermal monitoring continuing along the dam can be installed with small cost and with minimal earth works on already existing structure.