Driving factors and management strategies for water quality improvement in Fuxian Lake, China: A case study on ecological restoration and sustainable management of plateau lakes

• 3-decade TN/TP decline in Fuxian Lake via strict runoff controls and wetlands. • Policy-ecology integration boosts lake resilience, surpassing climate impacts. • Multivariate model shows human actions drive >70% water quality improvement. • Tailored strategies for plateau lakes balance tourism with watershed control. • First proof: multi-sector collaboration maintains China’s Class I freshwater reserves. Fuxian Lake, a vital plateau freshwater ecosystem in China, has undergone significant water quality transformation over the past three decades. This study systematically investigates the primary drivers of this improvement and proposes actionable strategies for sustainable management. By using a mixed-methods approach that integrates 34-year monitoring data (1990–2024) with principal component analysis (PCA), Statistical trend analyses (Mann-Kendall test with Sen’s slope), combined with geospatial visualization (GIS, kriging interpolation), Correlation networks (Pearson) and constrained ordination (Redundancy Analysis, RDA), we quantified the temporal-spatial dynamics of water quality parameters (TN, TP, COD), pinpointed dominant pollution pathways, and evaluated the cumulative efficacy of policy interventions versus climatic drivers. Our analysis demonstrates that stringent pollution source control, particularly in agricultural and urban runoff management, coupled with large-scale wetland restoration projects, has been instrumental in reducing nutrient inputs. Reveals that centralized pollution mitigation eliminated 78 % of agricultural nitrogen loads and 64 % of urban COD inputs, while large-scale wetland restoration reduced sedimentation rates by 41 % ± 8 % (p < 0.01). Additionally, the implementation of robust environmental policies and adaptive governance frameworks has significantly enhanced the lake’s resilience to external pressures. Climatic factors, such as precipitation patterns and temperature fluctuations, also influenced nutrient cycling and sedimentation processes, albeit to a lesser extent compared to anthropogenic interventions. This study not only highlights the success of integrated watershed management in Fuxian Lake but also provides a comprehensive analytical framework for the sustainable restoration and preservation of freshwater ecosystems worldwide. These findings underscore the importance of multi-sectoral collaboration, evidence-based policymaking, and long-term ecological monitoring in achieving environmental sustainability goals. This study also provides sustainably governance solutions for plateau lake ecosystems under Yunnan’s “Nine Lake Protection Initiative” and offers critical insights for provincial-level environmental protection policy formulation.