Effects of rainfall on microbial water quality on Qingdao No. 1 Bathing Beach, China

Limited by sampling frequency and detection methods, current recreational water monitoring programs often fail to protect public health, especially after heavy rain or flooding, when microbial water quality can change rapidly. In order to assess the variations in the microbial indicators and to develop a scientific warning system, we conducted an intensive sampling project at the No. 1 Bathing Beach. The results show that, during dry weather, the detection rate of Enterococcus was significantly lower than that of Faecal coliform bacteria. On these days, water quality was mainly impacted by pollutants brought in by swimmers than by stormwater outfall. During wet weather, rainfall and microbial bacterial concentrations showed a positive correlation. Trends in the two microbial bacteria were approximately the same. With increasing distance from the shore, the detection rate of microbial bacteria gradually decreased. Microbial bacteria concentrations increased markedly during high tide and under a south wind.