Sustainable innovation for the clear waters of Hangzhou West Lake, China: Achievements and insights.

Despite many efforts and financial support, globally successful eutrophication restoration cases are rare, particularly in subtropical shallow lakes. Proposal and implementation of restoration strategy is hindered by lack of evidence in the long-term. Based on 2,000 years of management history and the recently successful recovery achievement in West Lake, a typical subtropical shallow urban lake in Hangzhou, China's first lake-related world cultural heritage site listing, we highlight the origin, eutrophication, restoration, and management processes. Its management and restoration was undertaken using five crucial procedures that included paludification prevention, external nutrient loading reduction, internal nutrient control, recovery of submerged macrophytes, and stable system regulation. We found a vital factor and successfully reestablished a stable aquatic system dominated by submerged macrophytes for more than 15 years based on a long-term synergistic technique, which not only inhibits phytoplankton propagation but also improves the self-purification capacity of the water body and landscape function. Our study highlights challenges and objectives of management and protection in West Lake at the next stage, and the strategy and methods regarding ecological restoration for similar subtropical shallow urban lakes on account of cross-century scale evidence.