Calculations of hydrodynamic time parameters in a semi-opened coastal zone using a 3D hydrodynamic model

Hydrodynamic time parameters (HTs) in a semi-opened aquatic ecosystem are synthetic indicators offering the opportunity to bring out the links between its physical functioning and its biology. The generic term “residence time” is frequently used through literature to mention HTs resulting in various calculation methods. This article presents different computing methods relying on the use of a 3D numerical hydrodynamic model and the HTs to which they give access. Several large-scale (water exchange time, average water export time, e-flushing time) and local time parameters (export time, flushing lag, local e-flushing time) are defined. The applications presented are carried out within the south-west lagoon of New Caledonia (SLNC), on three embedded control volumes. The definition of the control volume is more important for the values of local HTs than for their comparative distribution. The comparison of the global hydrodynamic time scales applied to a control volume provides information on the mixing processes inside the control volume.