The paper assesses the hydro-morphological of the Misciwojow retention reservoir. The evaluation was carried out using the Ilnicki and Lewandowski’s method and the British River Habitat Survey (RHS), adapted to Polish conditions. The reservoir discussed in this paper is one of two small retention facilities in the Lower Silesian Voivodship with a preliminary reservoir. Apart from the function of water storage and flood protection, the main reservoir is also intended for recreational purpose. The biological barriers used separate the main reservoir from the initial reservoir, making it an island for waterfowl and other animals.