Measurements of velocity and temperature distributions were made in en
trances of tidal harbours at reduced scale. The influences of the geom
etry of the entrance and tidal water level changes on the flow in the
harbour entrance and the exchange of water between harbour and river w
ere studied. Density differences were absent. The formation and decay
of gyres in the harbour is shown to correspond with variations in adve
ctive and turbulent transports of heat through the harbour entrance.