Erosion and seepage processes development is one of the principal menaces for the hydraulic structure safety. The analysis of the data from the monitoring systems is the principal tool for their identification and their evolution determination. The effective group of the monitoring methods is the thermal-monitoring methods of the seepage process. These methods, very well known in many countries, are almost unknown in Poland. Heat and water transports are the coupled processes. Transport of the heat from the reservoir inward the dams body linked to the water seepage and changes of the humidity in the soil around the seepage zone, both their influence on the heat distribution in the dam. We present IRFTA (impulse response function thermal analysis) model that allows for seepage processes identification and for their intensity determination by analysis of the temperature measurements. Application of IRFTA model for seepage processes determination at the earth dike of the Oraison's canal is described in the paper.