Case study on application of graphical method for baseflow separation

Baseflow constitutes most of the streamflow during the dry season and it is an important factor for stream management. In this study, four techniques for separating baseflow from the streamflow were applied to two target areas to examine the applicability. The baseflow separation techniques used in the analysis are all graphical methods, which are fixed interval method (FIM), sliding interval method (SIM), local minimum method (LMM), and PART programs based on the N-day method. The target areas are the Daeri and Cheongsong stage stations in the Nakdong River Basin where the streamflow was measured continuously for 5 years. We evaluated the appropriateness of the results for baseflow separation methods by examining the indexes for model assessment (NSE, PBIAS, RSR), baseflow index, and shape of baseflow separated from a flood hydrograph. It was analyzed that the FIM, SIM, and LMM methods included some errors in separating the baseflow from streamflow, whereas the PART program results were found to be the best.