关键词: SCS, USLE, 总磷, 总氮, 参照状态, 程海

Abstract:

The loadings of total phosphorus and total nitrogen entering a lake were divided into two categories: point source and non-point source. The SCS (Soil Conservation Service) and the USLE (Universal Soil Loss Equation) models were used to calculate dissolved and particulate non-point source loadings, while the point source loading was estimated from the discharge of industrial, domestic and livestock wastewater. The mass conservation model of total phosphorus and total nitrogen in a lake was established, which was built upon the estimated input loadings of total phosphorus and total nitrogen entering a lake as well as the current concentration of total phosphorus and total nitrogen in the lake. Based on the calculated loadings entering a lake from the watershed and atmospheric deposition, along with the mass conservation model established, the previous annual average concentration of total phosphorus and total nitrogen in a lake was obtained by backward inference. Then, the reference condition of total phosphorus and total nitrogen, which was minimally impacted by human activities, could be established. The reference conditions of total phosphorus and total nitrogen in Chenghai Lake are 0.014 mg/L and 0.247 mg/L with the application of the proposed model. The reference conditions inference model is of clear physical concept, and less data required. Thus, the proposed methodology is applicable to other lakes under similar situations.

Key words: soil conservation service, universal soil loss equation, total phosphorus, total nitrogen, reference conditions, Chenghai Lake