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How do strong tidal currents create a vertically homogeneous estuary?

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Diagram showing four main types of estuaries: salt wedge, partially mixed, vertically homogeneous, and fjord. Each panel illustrates river and seawater mixing patterns, with arrows indicating the direction of saltwater and freshwater flow. — estuary Four main types of estuaries: (A) salt wedge estuary, (B) partially mixed estuary, (C) vertically homogeneous estuary, and (D) fjord (black arrows indicate salt water and white arrows fresh).

In a vertically homogeneous estuary, the river flow is relatively weak, while the tidal flow is strong. These powerful tidal currents generate sufficient turbulence to produce total mixing of the water column, which effectively eliminates the boundary between fresh water and seawater.12

Because of this intense mixing, salinity levels remain nearly uniform from the surface to the bottom at any given location within the estuary. While the water is vertically homogeneous, a horizontal salinity gradient still exists, with salinity levels being lowest where the river enters the estuary and highest near the sea.12