An interpretation of the relationship between dominant rainfall-runoff processes and the shape of flow duration curve by using data-based modeling approach

Abstract

Seeking a process-based understanding for the shape of the flow duration curve (FDC) uniqueness to a catchment, this study applied a data-based rainfall-runoff modeling approach in perennial, intermittent and ephemeral catchments which would have different dominant rainfall-runoff processes. Using this approach, we identified (1) the number of dominant runoff processes in a catchment, (2) rainwater storage in all processes, (3) infiltrations and return flows between the processes. We then identified reasons for different FDC shapes in the catchments in terms of identified dominant processes. Our results showed a humid climate with lower aridity index (AI) would cause perennial flow created by the combination of four dominant processes of fast flow, faster and slower interflows and base flow components. On the contrary, an arid climate with higher AI would cause ephemeral flow created by the combination of two dominant processes of fast and faster interflow components. These indicate a FDC in arid catchments would become ephemeral because of less dominant runoff processes occurring only near ground surface, whereas a humid catchment would become perennial because of more dominant runoff processes occurring from near ground surface to deep underground. These findings contribute in estimating FDCs in ungauged catchments from climatic conditions.