Preliminary Study on Baseflow Separation at Watersheds in East Java Regions

This research aims to determine the range of parameter value, baseflow index and the appropriate method for base flow separation. Seven (7) recursive-digital-filters (RDF) and two (2) graphical methods are used for this study. Discharge data from 8 watersheds in the administrative area of UPT PSDA Bondowoso in East Java were used to test the methods. Firstly, each method was calibrated using daily discharge data for each year (annually) to separate baseflow. Then, optimal parameter values are obtained by averaging the annual values. Calibration process produced optimal parameters value for each watershed. Furthermore, validation was performed using optimal parameter values from watershed having complete discharge data to other watersheds. The results show that optimal parameter values from calibrated watershed can be used to separate base flow in other watersheds. Principally, all methods can be used to separate base flow on this region, however three methods (EWMA, Line-Hollick and Local Minimum) perform better than others 6 methods.