This study takes the Shenzhen Bay Basin as the research object, based on the combined model of rainfall runoff pollution, overflow from sewer interception system and hydrodynamic water quality in the bay, the temporal and spatial variation of overflow pollution and its effect on water quality in the bay were analyzed. The results show that in the whole year, the main pollution sources of the basin are the pollution of the wastewater treatment plant and the overflow pollution. The overflow pollution accounts for about 30% of the total pollution load, rises to about 50% in the rainy season, and becames the main pollution source in the rainy season in Shenzhen Bay Basin. The overflow pollution load in rainy season accounts for more than 85% of the total overflow pollution load in the whole year. The pollution load of overflow increases with the rainfall. When the rainfall intensity is similar, the longer the dry time before rain, the greater the overflow pollution load. In terms of water quality in the bay, the water quality in the Inner Bay is worse than that in the Outer Bay and the fluctuation is more obvious, In rainy season, the water quality in Inner Bay and Middle Bay is worse and fluctuates more than that in dry season. In the event of rain, the water quality fluctuation in the inner bay was most seriously affected by the impact of overflow pollution, while the middle and outer bays was mainly affected by the tidal action. When the return period of rainfall is 0.25 to 0.5 years, the water quality in Shenzhen Bay exceeds the standard most obviously, and the duration of water quality affected by overflow pollution is 12 to 20 days.

overflow pollution, water source apportionment of pollution, bay water quality, temporal and spatial variation, storm water management modol (SWMM), the environmental fluid dynamics code (EFDC)