Author(s): Qian Xu; Ji Chen; Liqun Sun; Mervyn Peart
Linked Author(s): Ji Chen
Keywords: Baseflow; Direct runoff; Total discharge; Runoff coefficient
Abstract: This study aims to improve our understanding of the relationship between rainfall and runoff over small headwater catchments. In the summer of 2007, several rain gauges and one automatic water lever data-logger were installed in a headwater catchment located in the New Territories of Hong Kong, and since then, the rainfall data and the water level have been recorded at the one minute time step. Analysis of the recorded data revealed that intense and short rainfall events frequently occur at the catchment. Using three classical baseflow separation methods (namely, the straight line method, inflection point method and one parameter filter method), this study computes direct runoff volumes for 24 storms. Their runoff coefficients (which are the ratios of direct runoff volumes to the total rainfall volumes) are obtained; the analysis shows that direct runoffs can contribute about 82% of flood peak discharges, but the average runoff coefficients (which are the ratios of direct runoff volumes to the total rainfall volumes) are less than 4% . Then, a linear regression model was to construct to prediction runoff coefficients, P (total precipitation in mm) and Db (antecedent baseflow in m3/min) as independent variables.