Impact of consecutive rainfall on non-point source pollution in the Danshui River catchment
连续降雨对淡水河流域非点源污染的影响

The aim of this study was to investigate the impact of 4 consecutive rainfalls on non-point source pollution in the Danshui River catchment. Continuous measurements for water flows and water quality constituents were obtained at a pollutant flux station at the outlet of the Danshui River catchment. Results of regression analysis showed that there were no significant correlations between pollutant concentrations and water flows during consecutive rainfall, whereas significant correlations with water flows were found for pollutant fluxes. The sequence of correlations between pollutant fluxes and run off was listed as follows: TP>NH3-N>TN>SS>NO3-N. Statistic analysis was performed to compare pollutant output in storm events under similar rainfall condition. For long duration rainfall, fluxes of SS, TN and NH3-N of storm 3 decreased by 36%, 29% and 28% in comparison with storm 1. In the case of short duration rainfall, fluxes of SS, TN and NH3-N of storm 4 dropped by 8%, 32% and 26% when compared with storm 2. In contrast, NO3-N fluxes increased by 70% and 98% respectively (also storm 1 vs. storm 3, storm 2 vs. storm 4), while TP fluxes remained stable during consecutive rainfall.