ABSTRACT
ABSTRACT: Estimating the monthly and annual volume of groundwater contributions to runoff within a watershed is a critical aspect of many hydrogeologic investigations. In this study, groundwater contributions to total runoff asBaseflow Index (BFI)were estimated at fourteen streamgaging stations throughout the Basins in southwest of Iran. Two baseflow separation techniques, local minimum and recursive digital filter with range of 0.9-0.975 filter parameters, were used to separate daily runoff data into direct runoff and baseflow. The relative performances of the techniques were evaluated using the results obtained from recession analysis and visual inspection. Comparison of baseflow separation results indicated that recursive digital filter method with the parameter value of 0.925 has more accurate baseflow values. Temporal variability of BFI through the region was evaluated using the results of recursive digital filter method. Some possible applications of the results of this research in the study area were discussed.
