A technique for deriving an average event unit hydrograph from streamflow—only data for ephemeral quick-flow-dominant catchments

A technique is presented for empirical and parametric estimation of an average event unit hydrograph response curve solely from measured streamflow data for use in rainfall-runoff models with a focus on modelling flow for natural resource management. As the technique does not require rainfall data, the unit hydrograph can be derived solely from streamflow data at a temporal resolution appropriate for the response of the catchment. The response curves derived for a number of stations show a power law relationship of decay in flow after peak that can be described using a three-parameter function. The approach is best suited to ephemeral streamflow regimes dominated by surface and near-surface runoff (quick-flow component) where flow events are well-separated and largely independent of each other. Analysis of the derived unit hydrograph for 28 quick-flow-dominated catchments illustrates the range of parameter values obtained in fitting the power law.