Modeling the observed hydrograph recession of a small semiarid watershed

the recession curve of observed hydrographs was modeled based on the concept of linear reservoirs. each of the recession limbs was fitted using a non-linear curve fitting procedure based on levenberg-marquardt algorithm. the results showed that in general the response of this watershed is primarily non-linear. besides, the recession of the observed hydrographs showed a good fit by means of a two linear reservoirs model with parallel discharge. the mean residence time for this watershed varied between 0.1 and 6 h for direct runoff, while it ranged between 0.7 and 18.5 h for subsurface flow. finally, it was founded that subsurface flow is an important component of the hydrographs. from these results it can be concluded that hydrograph recession analysis technique could be useful in order to obtain a better insight about the runoff components as well as the recession process in watersheds of semiarid zones.