## 1 Introduction  
The Yangtze River Delta area is a densely urbanized area and one of the most developed and fastest-developing areas in China [1; 2; 3]. With the rapid economic development, the demand for energy resources has risen sharply, especially for oil products. The shipping of oil, which is relatively low-cost due to the great volumes transported, has increased with demand, resulting in frequent sudden oil spills in recent years. This has become a major safety hazard for water environmental security in the Yangtze River Delta region [4; 5].  
The Taipu River is an important cross-border river in the Yangtze River Delta region, spanning the Jiangsu, Zhejiang, and Shanghai provinces and cities [6; 7]. There are many water sources along the main stream of the Taipu River, so once an oil spill occurs it will inevitably lead to transboundary pollution and threaten the drinking water safety of people across a wide region [8; 9]. In view of this, it is of great significance to scientifically predict the spread of pollution after sudden oil spills in the transboundary region of the Yangtze River Delta. Furthermore, it is important to clarify the main factors controlling different types of events and assess the degrees of pollution, scope of impact, and risk levels associated with various incidents. These efforts will facilitate the establishment of effective and sensitive early warning systems and the formulation of response plans for sudden pollution incidents.  
A lot of work has been conducted internationally on the numerical simulation of oil spills, including the OILMAP system in the United States [10] and the OSCAR system in Norway [11]. Domestic scholars have also conducted a lot of work on oil spill numerical simulation. [PERSON] et al. have incorporated the HSY algorithm into the traditional Lagrangian oil spill model and established an oil spill prediction model based on uncertainty analysis [12]; [PERSON] et al. successively established oil spill prediction models in Zhoushan waters [13]; and [PERSON] et al. used hydrodynamic current field data and wind field data to simulate the influence range of oil using a multi-module coupling oil spill model [14]. The above work is basically focused on the numerical simulation of oil spills in the ocean or estuaries, and there is little research on the numerical simulation of river oil spills at home and abroad. Therefore, this paper aims to make up for the shortage of domestic oil spill simulations by the numerical simulation of the Taipu River oil spill accident. It also provides emergency plans for oil spill accidents.  
The objective of this paper is to establish the ability to quickly predict the extent and degree of oil pollution and the impact on water source inlet after an oil spill accident. At the same time, it has the function of water quality forecasting and risk warning. Thus, a scientific and efficient early warning and emergency system for sudden oil spill accidents can be built. It provides a decision-making basis for handling the sudden oil spill accident of the Taipu River and technical support for the safety of water supply quality of water sources.  
Taking the typical transboundary Taipu River in the Yangtze River Delta region as the research object, this paper established a two-dimensional oil spill model in the MIKE21 software environment created by the Danish Institute of Water Conservancy [15; 16]. This model can facilitate risk assessment research for emergency management and provide a theoretical basis and technical support for the prevention, monitoring, early warning, emergency response, and follow-up management of oil spill events. Therefore, this research has high theoretical research value as a unique example of a river oil spill simulation and high practical application value as a tool to be used during Taipu River oil spill events.