The examination of the performances of methods used in separating the total stream flow in different rivers

Abstract

In this study, the performances of methods of flow separation into the surface flow and base flow of the total stream flow in rivers with different hydraulic features have been examined. For this purpose, daily mean stream flow data of Büyük Melen and Aksu Rivers which are in the same watershed but with different features (average flow value, catchment area, mean elevation) have been separated as surface flow and base flow with the use of Digital Filtering Method (DFM) and United Kingdom Institute of Hydrology Method (UKIH). The recession coefficient in DFM has been used as α = 0.830; and the number of elements for the groups formed to determine the turning points of flow data in UKIH has been used as N = 5. The study has revealed that the results of surface and base flows obtained by both flow separation methods show similarity in all rivers in an acceptable level; and the surface flow values agree better (R² > 0,76) compared to base flow values (R² > 0.63). However, it has been seen that as long as the total flow values decrease, the surface flow results for both methods come closer to each other; but the results of base flow get differentiated. This situation has been clearly seen in the results of surface (R² > 0.89) and base (R² > 0.63) flows belonging to Aksu River which has lower values of flow when compared to the ones of Büyük Melen River.