Mean High Water Springs (MHWS)

Mean High Water Springs (MHWS) is the average height of the high waters at spring tides over a tidal epoch, the highs that occur near new and full moon when lunar and solar tides reinforce. It sits above Mean High Water and below the Highest Astronomical Tide, and on Admiralty charts it is the datum to which drying heights and many coastal features are referenced. MHWS marks roughly the upper limit reached by ordinary spring high water, so it sets the practical inland edge of regular tidal inundation used in survey and charting.