Water resource management absolutely depends on water resource data like rainfall and streamrnflow. Better quality of such data are obtained by direct measurement via interconnectedrngauging instruments. Due to limited resource, gauging instrumentsâ€™ distribution are not densernenough, in turn causes water resource data scarcity. Currently, Satellite rainfall estimates arernavailable with good spatial and temporal resolutions. However, they are estimates rather thanrndirect measurements. Thus, as the study was begun to evaluate the performance of satelliternbased rainfall product, TRMM_3B42; it was validated in Jemma sub-basin, and its raw andrncombined version was evaluated as input of distributed type of HEC-HMS model in Gumerrowrncatchment. For the achievement of the objectives, collected hydro-meteorological, satelliternremote sensing and Arc-Info data were processed with appropriate tools like R-programingrnlanguage, Arc-GIS model builder, HEC-HMS and others. Results also were presented usingrngraphical techniques, categorical and continuous statistics, and model evaluation statistics.rnThe Satellite based rainfall product and Ground rain-gage data were comparable except somernimportant variations. In categorical rainfall values, the overall accuracy of Satellite rainfallrnestimate was greater than 78.7%, which was observed in Light rain type of daily timescale.rnHowever, the stated algorism has faced special difficulty in daily timescale with more falsernalarms. In continuous rainfall values, Positive linear association was detected in daily, monthlyrnand seasonal timescales with correlation coefficient values of 0.52, 0.915 and 0.926 respectively.rnAnd an average underestimation of Satellite rainfall estimate was discovered in all timescales.rnAmong seven HEC-HMS model parameters, Potential max retention factor (S) was obtainedrnas the most sensitive parameter in Gumerrow catchment. Raw Satellite rainfall estimaternshowed poor performance in calibration period of (2003-2006) with NSE, PBIAS, RSR andrnR2 values of 0.406, 24.26%, 0.771 and 0.417 respectively. However, the performance hadrnimproved significantly to good enough with NSE, PBIAS, RSR and R2 values of 0.532, 14.83%,rn0.684 and 0.554 respectively when combined version was used as input of HEC-HMS model.rnRelative to calibration period, improved performance was discovered in validation periodrnof (2007-2008) with NSE, RSR and R2 values of 0.452, 0.74 and 0.477 respectively for rawrnSatellite rainfall estimate, and 0.56, 0.663 and 0.618 respectively for combined version.