Construction of lake reference conditions for nutrient criteria based on system dynamics modelling

Assessment of ecological status is crucial for establishing well-defined reference conditions for a lake. In this study, a model based on System Dynamics was developed to simulate the production, transport and distribution of the nutrients in Lake Chenghai, Yunnan Province, China. Application of the proposed model with a system retrieval technique yielded the variations in nutrient concentrations and eutrophication levels under different hydraulic conditions during the past several decades. Results showed that the proposed model is capable of describing the historical process of the lake's eutrophication after calibrating with the experimental data. The reference conditions for Lake Chenghai were proposed as follows: 0.0074-0.0091 mg/L for the total phosphorus concentration, 0.112-0.128 mg/L for the total nitrogen concentration, 0.859-1.081 ug/L for the chlorophyll a concentration, and 6.327-5.557 m for the Secci depth transparency. It provided an effective way to establish the nutrient reference conditions for the foundation of a lake's nutrient criteria, as well as the eutrophication control standards in China.