As the part of the sustainable development of water balance and increased needs for water, hydro-engineering structures help to shape artificiall water accumulations as a need of modern-day lifestyle and human interaction with nature. The consequence of the increase in the living standard is the rise in water consumption; therefore each country, and region must determine which waters they have at their disposal and the means of the usage and the protection of the water in their system. According to the Plan of the Istrian county, the accumulation Grobnik plays a significant role. The construction of Grobnik dam is foreseen due to the mitigation of the consequences of extreme waters and due to flood protection that appear on the Posert stream (tributaries of the river Raša). The dam forms accumulation with the basic purpose to protect downstream areas from floods, but it`s waters, according to the irrigation plan of Istrian County , are used to irrigate agricultural crops during the dry season of the year. This work deals with the conceptual design of the Grobnik dam. It covers the elements and parameters, related to the dam itself, by which the choice of dam type, the location of the partition profile and the size of the accumulation is influenced. By the analysis of the geological and hydrological base, a heterogeneous embankment dam made of limestone and marl with clay core and filter layer has been chosen. For the evacuation of large waters, side overflow has been selected with a chute and waterfall, while of the range of the auxiliary facilities, in this work are covered: the basic discharge with the associated closure, control gallery, water intake building.