Abstract: Ulza Lake catchment is part of the Mat River basin and has a hilly and partially mountainous watershed. From the hydrographic point of view, it is distinguished for a dense network of watercourses, especially in the middle and lower part where ultrabasic formations are dominant. In order to analyze seasonal and annual water balance for Ulza Lake watershed, the HEC HMS hydrological rainfall-runoff model has been implemented in the Mat river. The hydrological model used as input daily hydrometeorological observed data for precipitation, discharge, and temperature in the period 2002-2011. The method used for transform was SCS Unit hydrograph and for the routing was used Muskingum Kinge. The observed meteorological data was validated through a basic integrity test for the identification of anomalous values. Ulza Lake catchment has been divided into 13 subbasins in order to better calculate the inflow. The hydrological historical data in the period 2002-2011 was used for calibrating the model. HEC HMS result data series for Ulza Lake were processed and plotted using different methods.