Evaluating the Response of the Residence Time to Flow in the Lower Peace River Estuary in Florida, USA

The paper presents the use of a sophisticated hydrodynamic model to evaluate the response of the estuarine residence time (ERT) to flow in the Lower Peace River (LPR) estuary located on the southwest coast of Florida, USA. Here, the ERT is defined, following Miller and McPherson (1991, Limnol. Oceanogr., 36: 602–612), as the time required to flush out a certain percentage of conservative particles that were evenly distributed at time = 0. With the use of a multi-block hydrodynamic model that dynamically couples a 3D model with a laterally averaged 2D model, ERT values for a total of 16 freshwater flow scenarios were calculated. Unlike most previous tracer simulations which did not allow tracers that left the domain during the ebb tides to return back to the estuary, this study allows some of them to return during the flood tides, resulting in a more realistic estimation of the ERT in the LPR. Based on a careful analysis of calculated ERTs, it was found that the ERT in the LPR is a power function of the gauged in-stream flow (Q) from the Peace River watershed and the ERT in the LPR can be expressed as ERT = [240.83−51.76ln(L)]Q^-0.556, where L represents the percentage of remaining conservative mass within the estuarine system after ERT days.