Analysis of Trophic State Uncertainty and its Variation: Miyun Reservoir, Beijing, China

Frequently used biomass-related Trophic State Index (TSI) shows the total weight of living biological material in a waterbody at a specific location and time. TSI isdetermined from water chemistry samples and the Secchi depth measurement. Applying this, one can get a quick idea about how productive a lake is, by its assignedTSI number. In this paper, an attempt has been made to identify the basic factors influencing the TSI number in a reservoir. Then, by using Delta method, regarding toeffective factors uncertainties, a case study on the base of Miyun Reservoir data has been done to determine the TSI number in this reservoir and the coefficient ofvariation to ponder the optimal water resource management in the Reservoir. The results of this investigation have been indicated that the average TSI number and its variation in Miyun reservoir during the October were 43.83 ± 10.68 (mean ± SD).These values indicate that the Miyun reservoir is oscillating between Mesotrophic to Eutrophic category. It means that the lake is considered to be waterbodies with midrangeto sufficient nutrients and has fairly high productivity

Keywords:

TSI , Miyun Reservoir , Uncertainty , Delta Method