Reaeration Rate Estimation Using the Lag in Dissolved Oxygen Concentration

Michael G. Waldon

Abstract: Estimation of the reaeration coefficient in a stream may be classified as a dynamic system parameter estimation problem. One classical method of parameter estimation widely used in other fields involves observation of the output of a system being ' forced ' by a sinusoidal input signal. In some cases the system parameters may be estimated by simply observing the lag of the output to the input signal at one or more input frequencies. This classical method is here applied to the estimation of the reaeration coefficient. In this case, the forcing function or input is the diel production and consumptive of oxygen through photosynthesis and respiration. This function is assumed to be symmetrical and to peak at local true solar noon. A proposed relationship provides an estimate of the reaeration coefficient based on the timing of the afternoon maximum of dissolved oxygen and the day length. This method, termed the ' Peak Lag Method ', is derived and tested, and an extension is proposed which allows analysis of data from multiple stations along a stream. It is concluded that under some conditions the peak lag method provides an acceptable alternative to other estimation techniques.

Technical completion report, Water Resources Research Institute, OWRT Project Number A-54-LA, NTIS #PB83-202341, 1983.