## 2 Study Area  
Chaohu Lake (31 deg42'\(\sim\)32 deg25' N, 116 deg23'\(\sim\)118 deg22' E) is one of the five major freshwater lakes in China in the middle and lower reaches of the Yangtze River. It is located in central Anhui Province, China, with a perimeter of 176 km, an average depth of 2.89 m, an area of 780 km\({}^{2}\), and a volume of 2.07 billion m\({}^{3}\)[15]. The lake is mainly recharged by surface runoff, with a watershed area of 13,486 km\({}^{2}\) and 35 rivers along the lake [16]. Chaohu Lake has a northern subtropical temperate monsoon climate with significant monsoons and four distinct seasons. The average annual temperature of the entire basin is between 15 and 16 \({}^{\circ}\)C, the active cumulative temperature is above 4500 \({}^{\circ}\)C, the frost-free period is above 200 days, the annual temperature difference is above 25 \({}^{\circ}\)C, and the annual precipitation contour of 1000 mm passes through the district boundary [17]. The main roles of the basin are shipping, water supply, irrigation, aquaculture, tourism, and many other functions. Figure 1 illustrates the land use pattern of the Chaohu Lake watershed, with urban land (red blocks) dominating the upstream, while the peripheral areas of the watershed are dominated by paddy fields for cultivation and aquaculture, while the downstream is dominated by scattered industrial and other special land uses [15; 18].  
In a study published by [PERSON] et al. [19] in 2022, it was noted that the annual average amounts of total nitrogen and total phosphorus in the basin were estimated to be 10,832 t/a and 781 t/a. This case study also shows that the load intensity within the watershed is unevenly distributed, and soil erosion, precipitation intensity, and population density, as the three key factors driving N and P losses, show a positive correlation with the intensity of N and P losses. In addition, the studies by [PERSON] et al. and [PERSON] et al. [20; 21] both showed that the water quality pollution of Chaohu Lake mainly originated from the rapid population growth and economic development, and the high-intensity human activities further deteriorated the water quality. Untreated domestic sewage, industrial wastewater, and massive application of pesticides in major tributaries, all of which have caused accumulation of nutrients in their water bodies, increased net primary productivity, increased eutrophication, shrinking of lakeshoe ecological zones, elevated lake bottoms and accelerated aging of the lakes. It is extremely important to establish a water quality prediction model that meets the long-term needs to cope with the changing trends in the future stages [22].  
The data for this study was selected from some monitoring sections in the Chaohu basin, which are located at the latitude and longitude as shown in Table 1. By analyzing the geographic environment of the monitoring points on the map, including relative location, topography, climate, vegetation, soil, and distribution in the upstream and downstream of the basin, three more representative monitoring sections in Figure 2: Lakeside, Chaohu Shipyard, and the Zhaojia River intake area were chosen as cases for this study to implement the proposed model.  
Figure 1: Distribution of utilization types in the Chaohu Lake watershed.