DIAGNOSTIC MODELING OF RESIDENCE TIMES IN ESTUARIES

The variability of estuarine residence times is elucidated through acc urate, diagnostic numerical tracking of a large number of particles, c omplemented with statistical analysis. Residence times are shown to ha ve strong spatial and temporal variability, which is accentuated by ex changes between the estuary and the coastal ocean due to chaotic stirr ing at the mouth. The concept of a single residence time per estuary, while convenient from both ecological and engineering viewpoints, is t herefore shown to be an oversimplification. Maps of residence times an d cumulative histograms are examined as alternatives. The former are a ttractive only for once-through tracers, while the latter appear usefu l over a broader range of tracer characteristics.