Macrophytes play a crucial role in maintaining the health of lake ecosystems. A thorough understanding of their long-term evolutionary processes and patterns is of great theoretical and practical significance for ecosystem restoration and mitigation of lake eutrophication. The succession process and driving factors of macrophytes in the Lake Erhai aquatic ecosystem were systematically analyzed using the investigation of macrophytes, literature research, and classification. A survey conducted in July 2022 showed that the macrophyte community in Lake Erhai is seriously degraded, with species numbers notably lower than historical levels from a decade ago (2011). The distribution area declined by over 70% compared to its peak in the 1980s. Over the past 60 years, the macrophyte community of Lake Erhai has undergone successive processes, including expansion, peak, decline, and stabilization. The dominant populations gradually transitioned from being indicative of clean water to pollution-tolerant species. The driving factors of the macrophytes succession of Lake Erhai were the development of cascade hydropower projects on the Xi’er River and the increased outflow capacity of Lake Erhai; these have resulted in substantial fluctuations in water levels, the eutrophication of the lake, pollutant discharge exceeding Lake Erhai’s environmental capacity, and substantial climate change in the Lake Erhai basin. Our research provides important theoretical references for ecological restoration and management of early eutrophic lakes in China.

Nutrient-loading patterns remain poorly characterized in plateau lake watersheds with complex terrain and sparse monitoring. We applied the Loading Simulation Program in C++ (LSPC) to the Yangzonghai Lake watershed to estimate runoff, total nitrogen (TN), and total phosphorus (TP) loads during 2017–2024. Across three monitoring stations, validation Nash–Sutcliffe efficiency values ranged from 0.54 to 0.75 for streamflow, 0.51 to 0.66 for TN, and 0.50 to 0.60 for TP. Approximately 86% of annual inflow occurred during the wet season, whereas the wet-season proportions of nutrient loads were lower, indicating higher nutrient export per unit water volume during the dry season. Total loads and area-specific loading intensities showed contrasting spatial patterns. Southern sub-basins contributed more than 48% of total nutrient loads, while the highest loading intensities occurred in the middle and lower Baiyi River in the north, where domestic sewage was estimated to contribute more than 50%. These findings support differentiated management: agricultural nutrient management and erosion control in the south, and sewage interception and sewer-network improvements in the north. The framework provides spatial information for targeted nutrient management and offers a methodological reference for similar data-limited basins worldwide.