Basef low is the main source of stream flow in the dry season of a year. Due to the difficulty in measurement

it is important to select an adaptive basef low separat ion method for further baseflow research. In order to test the applicability of automated base flow separation methods on the Loess Plateau

six watersheds located in the hilly and gully region were chosen to estimate several widely used techniques

which are PART

digital filter technique

and smoothed minima method. Comparison shows that the results of all three type methods have little difference. The discharge hydrograph demonst rates that the result of digital filter method is more consistent with the actual discharge condition. Since the true values of the baseflow index are unknown

it is difficult to find which method may give the best estimation. However

the digital filter method appears to be more plausible than other methods for this region and the results from the method are objective and authentic. For the study area

result from digital filter method shows that the basef low index is 37%~ 64%

which means that basef low accounts for a larg e proportion of the total runo ff . However

the baseflow volume has been gradually reduced in the recent 48 years.