Oxygen Balance of an Estuary

The net seaward movement of organic impurities in estuaries is due to the displacement by the land runoff and to the longitudinal diffusion of the tidal action. The dissolved-oxygen profile depends on the concentration of the organic material, its rate of oxidation, and the resulting rate of reaeration. The interrelationship among these geophysical and biochemical factors is described by a differential equation under a steady-state condition. The assumption of constant coefficients in the equation is confirmed by the field data from estuarine surveys of the Delaware and the James Rivers. Dissolved-oxygen profiles are calculated from the integrated equation and compared to the measured dissolved-oxygen concentrations. The turbulent diffusion coefficient and the deoxygenation rate are determined from an analysis of survey data and are used in the calculation of the oxygen profiles. The agreement between the calculated profiles and the observed values is sufficiently close to justify the use of the equations for the conditions assumed in the development.