Grey Box Modelling of Oxygen Levels in a Small Stream

Data from a stream is used to identify a dynamic model of the oxygen level as a function of solar radiation and precipitation. The time series of the oxygen level is occasionally corrupted by pumping of external water into the stream, which is of no interest to the biological processes in the stream. In this paper a grey box modelling approach, which is a statistical method taking the known physical relations into account, is used. Using this approach, an identification of a stochastic continuous time model for the oxygen level based on the discrete time data, where the corrupted data are considered as missing values, is outlined.