Mean High Water Springs (MHWS) (MHWS)

The average height of the two successive high waters during spring-tide periods at a stated location and over a defined observation period.

MHWS is a tidal datum associated with the larger astronomical ranges near new and full moon, derived according to the responsible hydrographic authority’s method. It is an average and is neither the highest astronomical tide nor a prediction of every spring high water. It is used as a height reference in some charts, clearance information and coastal boundaries, but the actual datum must be read from the relevant source. Meteorological effects can raise or lower observed water relative to MHWS.