The water volume-renewing period model: Leşu reservoir on the Iada river. The water volume-renewing period (turnover period) is in a strong relation with an other hydrological characteristic, the water volume variation. The volume variation expresses the annual renewing of the water volume and it can be computed by the help of the hydrologic balance. The intensity of this variation represents the volume-renewing period and we can define it as the time in which the whole volume of a basin is renewed. In case of natural or artificial lakes, the estimation of this intensity is very important considering the water quality and different chemical and biological water characteristics. The turnover period of water volume in lakes is mainly influenced by the volume magnitude and the input and output discharge, but there are some other elements, too.