Minimum water discharge and seasonal flow calculations of Veliki Rzav at Arilje have been conducted for the purposes of regional water supply system "Rzav". For the first time for this hydrological station minimum water discharges have been calculated by frequency curves, parameters of which have been determined by method of moments. Also for the first time in Serbia seasonal flow was calculated using "composing method". Analysis presented in this paper can be used for exploitation and planning of upcoming water management activities in the regional water supply system "Rzav.