Small retention basins are water managing objects for acumulation of water for the purpose of cultivating land, cattle feeding and other. They are mostly used by individual rural economies for their own local needs for irrigation of smaller agricultural areas (orchards, smaller plantations etc.) or source of water for their livestock. At the beginning of this work all types of small retention basins are presented, regarding the available water sources, restrictions and requirements in accordance with Slovenian legislation. This is followed by some basic instructions for building small detention basins on different composition of geological characteristics found in Slovenia. Designation of a good catchment area can be a challenging task because of the very high inequality of precipitation distribution in Slovenia. Therefore this thesis includes a good orientational help in form of maps of potential annual and winter water storage in Slovenia that have been made on demand of Ministry of agriculture. In continuation there is a more thorough description of the realization of all four basic components of retention basin: reservoir, dam, outlet structure and emergency spillway. In the main, practical part of this work, I have designed a small retention basin for the catchment of surface runoff in Hrusevo.