Towards reconstruction of the flow duration curve: development of a conceptual framework with a physical basis

摘要

In this paper we investigate the climatic and landscape controls on the flowduration curve (FDC) with the use of a physically-based rainfall-runoffmodel. The FDC is a stochastic representation of the variability of runoff,which arises from the transformation, by the catchment, of within-yearvariability of precipitation that can itself be characterized by acorresponding duration curve for precipitation (PDC). Numerical simulationsare carried out with the rainfall-runoff model under a variety ofcombinations of climatic inputs (i.e. precipitation, potential evaporation,including their within-year variability) and landscape properties(i.e. soil type and depth). The simulations indicated that the FDC can bedisaggregated into two components, with sharply differing characteristicsand origins: the FDC for surface (fast) runoff (SFDC) and the FDC forsubsurface (slow) runoff (SSFDC), which included base flow in our analysis.SFDC closely tracked PDC and can be approximated with the use of a simple,nonlinear (threshold) filter model. On the other hand, SSFDC tracked the FDCthat is constructed from the regime curve (i.e. mean monthly runoff), whichcan be closely approximated by a linear filter model. Sensitivity analyseswere carried out to understand the climate and landscape controls on eachcomponent, gaining useful physical insights into their respective shapes. Inparticular the results suggested that evaporation from dynamic saturatedareas, especially in the dry season, can contribute to a sharp dip at thelower tail of the FDCs. Based on these results, we develop a conceptualframework for the reconstruction of FDCs in ungauged basins. This frameworkpartitions the FDC into: (1) a fast flow component, governed by a filteredversion of PDC, (2) a slow flow component governed by the regime curve, and(3) a correction to SSFDC to capture the effects of high evapotranspiration(ET) at low flows.