Comparison of Base Flow Estimation Methods Based on Hydrograph Separation (Case study: Karun Basin)

Estimating the volume of groundwater contribution to runoff within a watershed is one of the most important subjects in water resources management and hydrology. In this paper, groundwater contribution to total runoff as a base flow index was estimated using hydrograph separation in six stream gauging stations in southwest of Iran. The major objective of this research is to distinguish the most suitable automated hydrograph separation and base flow estimation method. Conventional automated hydrograph separation methods including local minimum and recursive digital filter with the parameter of 0.9 to 0.975 were compared with recession analysis numerically and graphically. The results showed that recursive digital filter with the parameter of 0.925 is the most accurate method to estimate base flow in the studied watersheds. This research also indicated that the base flow index estimated through the selected method varies from 0.79 to 0.88 in the study area.