Dianchi Shallow Lake Management

Lake Dianchi in the Chinese province Yunnan is a shallow lake suffering from algae blooms for years due to high pollution. We conducted a thorough survey of the water quality of the northern part of the lake called Caohai. This study was intended as the basis for the system understanding of the shallow lake of Caohai. The study consisted of two steps. First we collected available environmental, hydrological and pollution data from Kunming authorities and other sources. It was possible to parameterise a lake model model based on the preliminary data set. It supported first estimations of management scenarios. But the first and quick answers came with a relevant vagueness. Relevant monitoring data was still missing like P release from lake-internal sediment.Because data uncertainty causes model uncertainty and model uncertainty causes planning and management uncertainties, we recommended and conducted a thorough sediment and river pollution monitoring campaign in 2017. Examination of the sediment phosphorus release and additional measurements of N and P was crucial for the improvement of the shallow lake model of Caohai. In May 2018 we presented and discussed the results of StoLaM shallow lake model of Caohai and the outcomes of a set of management scenarios.The StoLaM shallow lake model for Caohai used in SINOWATER indicates that sediment dredging could contribute to the control of algae by limitation of phosphorus, but sediment management can only produce sustainable effects when the overall nutrient input and especially the phosphorus input from the inflows will be reduced significantly.