An improved and consistent approach to estimate catchment response time parameters: case study in the C5 drainage region, South Africa

Abstract

Large errors in estimates of peak discharge in medium to large catchments in South Africa can be largely ascribed to significant errors in the estimation of the catchment response time, mainly as a consequence of the use of inappropriate time variables, the inadequate use of a simplified convolution process between rainfall–run-off time variables, and the lack of locally developed empirical methods to estimate catchment response time parameters. Furthermore, the use of a typical convolution process between a single hyetograph and hydrograph to estimate observed time parameters at large catchment scales is regarded as not practical, as such simplification is not applicable in real, large heterogeneous catchments where antecedent moisture from previous rainfall events and spatially non-uniform rainfall hyetographs can result in multipeaked hydrographs. This paper presents the development and evaluation of an alternative, improved and consistent approach to estimate catchment response time expressed as the time to peak (TP) in the C5 secondary drainage region in South Africa, while the interrelationship, similarity and proportionality ratios between TP and the conceptual time of concentration (TC) and lag time (TL) are also investigated.