Abstract: As a non-point source pollution, initial rainwater has seriously affected the current situation of urban water environment. In this paper we analyzed different types of control measures for initial rainwater runoff pollution, and compared functions of pollutant accumulation, washout, and simulation software. Furthermore, we simulated rainfall in the study area by Digital Water with three scenarios: non-developed scenario, LID (Low Impact Development) scenario, and end storage tank scenario. We found that source control and end control in combination had satisfactory result and each played significant role in initial runoff reduction and pollutant concentration reduction in different time and space scales with different contribution rates. LID measures cut pollutant concentration and peak flow through interception in the early stage, and weakened later on; while storage tank reduced peak discharge and pollutant concentration in the later stage of rainfall. Nevertheless, the application and research on process control of initial rainwater, namely, the interception of initial rainwater, is inadequate, hence would be the direction of future research and practice.

Key words: initial rainwater, runoff, Digital Water, pollution control, LID, storage tank