The accurate determination of the flow rate of the low flow season is a very important factor in setting and running a water resources development plan. Because South Korea undergoes a lot of flood damage due to localized heavy rain during the summer season, flow rates are measured mostly according to flood management, and this allows for a lack in research in understanding low flow season flow rates. In order to estimate the accurate flow rate of a low flow season, the present study has used the Parshall flume that has been used widely in flow measurements, and has reviewed the applicability. A Parshall flume was installed in an actual river and the measured flow rate that was obtained from the flow rate formula and velocity measurements, that were suggested by the ISO and the USBR, were found to be very accurate when compared to the flow rate computation results by the Parshall flume. By using the state-discharge rating curve equation that is most commonly used at the level gauging station, the flow rate was estimated and compared with the flow rate by the Parshall flume. The results showed an approximate 14% error with the estimation from the state-discharge rating curve equation. Therefore, using the Parshall flume to estimate the flow rate of low flow season is more effective than the state-discharge rating curve equation.