## 1 Introduction  
With the development of the social economy, people pay more attention to water environment problems. At the same time, the problem of point source pollution is gradually being solved and effectively controlled [1]. However, non-point source pollution with urban rainwater runoff pollution as the main pollution source threatens the health of the urban water environment [2]. Research on the urban water environment shows that even if the problem of urban sewage pollution is solved, urban rainwater runoff pollution will still hinder the improvement of receiving water quality [3]. Even with diverted drainage systems, stormwater runoff pollution can degrade water quality and accelerate biodiversity loss in rivers [4]. Rainwater runoff that is dumped directly into an urban water body without taking necessary precautions will harm the urban water ecosystem. As a result, adopting steps to reduce stormwater runoff pollution is critical to improving the urban water environment. Traditional stormwater management methods are not enough to solve the problem of stormwater runoff pollution, such as drainage system renovation or traditional grey infrastructure construction [5]. In recent years, the construction of sponge cities in China, the Sustainable Urban Drainage System (SUDS) in the UK, Water Sensitive Urban Design (WSUD) in Australia, and LID in North America have all brought new ideas to widely used urban stormwater management and demonstrated that Effective in stormwater management [6]. China is carrying out extensive sponge city construction, and one of the purposes of sponge city construction is to reduce pollution from stormwater runoff [7]. Enhancing sponge cities with recommended strategies can increase the economic, environmental, and architectural sustainability of metropolitan regions [8]. Since 2015, China has carried out sponge city construction pilot projects in 30 cities in two batches, accumulating a lot of practical experience and theoretical research, especially in the control of runoff pollution based on initial runoff volume capture [9]. From 2021 to the next five years, China will systematically carry out the construction of sponge cities in the whole region, which will bring new opportunities for research related to the reduction of runoff pollution. When dealing with high-frequency rainfall, LID facilities primarily focus on rainwater source control, which has a good runoff control impact and may effectively minimize total runoff, peak volume, and the peak present time [10]. Different LID facility combination schemes can be quantitatively analyzed using model simulation, taking into account various factors such as total runoff control, pollutant control, and cost to conduct a structured evaluation of facility combination schemes and select the optimal scheme for current conditions [11]. The stormwater management model (SWMM), MIKE Urban, Info Works ICM, and other drainage models have been widely used in stormwater management and achieved satisfactory results [12]. The SWMM model is often used to simulate the rainwater runoff control effect of LID facilities, and the potential factors affecting the LID runoff control effect can be analyzed through multiple rainfall simulations [13]. Over the years, the code integrity of the SWMM model has continued to increase, and it is widely used in China. At present, the research on the rainwater runoff and pollutant control effects of actual projects in the acceptance of sponge cities mainly relies on SWMM [14]. Some research has concentrated on the scouring effect during the early stages of rainfall, demonstrating that sponge city source facilities have a positive impact on runoff pollution management [15]. In the related research on the reduction of rainwater runoff pollution, some studies directly use the control volume of rainwater runoff to represent the amount of runoff pollution reduction [16; 17]. However, the relationship between volume control rate and pollutant control rate is not clear.