Introduction. Recently the issue of study in thermo-stressed state of rockfill dam concrete faces has become urgent. This is related to the fact that stresses from thermal effects may be one of the reasons that cause crack formation in a concrete face. This paper investigates the character of a thermal effect to which the face is subject during the reservoir impoundment. Materials and methods. There was studied nonstationary temperature regime of a fragment of a dam structure with a concrete face at the contact with cold water. Two cases were considered: rapid reservoir impoundment and impoundment with water rise rate 1 m a day. The study was conducted by numerical modeling method with the aid of the commercial software system ANSYS and the authorial computer program. It was shown that in order to obtain adequate results, the finite-element model should be in great detail. Results. Analysis showed that after the reservoir impoundment the face temperature regime is installed a durably, about one month. At a rate of 1m/day reservoir water level rise the face temperature regime is formed during a longer time than at rapid reservoir impoundment. The face temperature regime varies more intensively during the first three days. During this time interval, the face is subject to a high temperature gradient. Conclusion. The face temperature regime at the reservoir water level variation, characterized by a high temperature gradient during several days, evidences about unfavorable thermal effect, because it results in the face bending deformations. At stress-strain state analyses of a concrete face, it is reasonable to consider the thermal effect characterized by the temperature variation not throughout the whole thickness of the face but only in the part nearest to the upstream face.