Long-term evaluation of pollutiondynamicsin West Lake Taihu, China: Enhanced WQI and TLI models for improved accuracy and management relevance

Accurately assessing water quality and eutrophication remains a critical challenge in global lake pollution management. Traditional models, such as the Water Quality Index (WQI) and Trophic Level Index (TLI), often rely on expert judgment and outdated guidelines, limiting their adaptability to evolving pollution conditions. This study improves overall model performance by integrating Principal Component Analysis (PCA) and Factor Analysis (FA) for parameter weighting, and using Random Forest (RF) to validate weight rankings. West Lake Taihu (WTH), the largest natural pretreatment reservoir of Lake Taihu, was selected as the case study for assessing long-term (2008–2023) pollution dynamics. Results showed that total phosphorus (TP) and total nitrogen (TN) were the dominant factors influencing both water quality and eutrophication, replacing traditional dissolved oxygen (DO) and chlorophyll-a (Chl-a). RF and exceedance rate analyses confirmed TP (24.79%) and TN (19.51%) as the primary contributors to WQI, with exceedance rates > 80%, while DO showed little influence (