|A simple method was developed to estimate longitudinal profiles of ordinary waterlevel using existing gauging station data and its estimation accuracy was verified bycomparison with observed values for the Shonai River, Japan. First in this new method, alongitudinal profile of ＂reference riverbed elevation＂ is created using riverbed elevationdata, periodically measured by the river manager. Second, the longitudinal profile of ordinarywater level is estimated using the reference riverbed elevation and gauging stationwater levels. Overall, the estimation accuracy of our method was high. Our new estimationsshowed higher accuracy than the linear interpolations in the all river segment types（ M, 1,2-1, and 2-2）. Our new estimations showed higher accuracy than the uniform flow estimationswith simplified roughness coefficients and slopes in the 2-1 and 2-2 segments, andshowed similar accuracy to the uniform flow estimations in the M and 1 segments.