Abstract
Analyses on the stochastic characteristics of inflow and transformation of water quality in a eutrophic reservoir are carried out based on water quality measurements in the reservoir. The reservoir under study has an anaerobic and eutrophic water near the bottom layer throughout a year. Water body of the bottom layer shows high electric conductivity and has never been exchanged in the last few years. The measurements of water quality have been carried out every month. The structures of the obtained time series are analyzed, regarding them as stochastic process. It is found that the time series of COD and T-N are considered to be the AR(1) process. We also attempt to apply the linear time invariant system to the transformation of water quality in the reservoir.