T he Institute of H ydrology Lum ped M odel \vhich is one of the sim uiation m odels used in estim ation of stream flow was described and m odel parameters \vere optim ised on the two years o f observed flows from the Ortadere catchm ents I and IV in Belgrad Forest, C alibration results show that the m odel could be applicable for catchm ents having broadleaved forests, relations betw een observed and predicted flows were signiHcant. In order to get better results, precipitation characteristics such as type, and intensity, and dates of snovvmelt slıould be taken into account.