On the predictability of the 137Cs distribution in the Severn Estuary

The observed distribution of ¹³⁷Cs resulting from known sources in the Severn Estuary permits the testing of simple predictive models for the one-dimensional distribution of non-conservative substances in an estuary. These models either use a known distribution of salinity to infer corresponding ones for other substances, or else directly solve mass balance equations utilizing previously determined dispersion coefficients. Both methods are shown to previously determined dispersion coefficients. Both methods are shown to provide results comparing favorably with observations.Stokes drift plays an important role in the circulation of the Severn. A modified densimetric Froude number, including this drift, is therefore used to estimate the circulation and stratification of the estuary.A new equation is used for calculating the ¹³⁷Cs distribution from the observed salinity distribution. It generalizes previous formulations to permit variation of the net runoff with position along the estuary.