This paper intends to formulate the base flow model due to the watershed morphometry factors. The methodology consists of to carry out the filtering of rainfall-single peak flood hydrograph pair data, then to separate the base flow and direct run-off from the observed hydrograph. However, the whole data that are used in this research are formerly evaluated regarding to the data validity condition. The next step is to find out the average of each base flow peak discharge. Finally, is to characterize the watershed physical parameter to formulate the base flow modeling. The result shows that the base flow formulation is QBF = 0.355 * P1,124 * Dd0,310 with the determination coefficient is 0.782