Terms & Glossaries of Shipping and Trading

MLLW (Mean lower low water)

Mean lower low water (MLLW) is the average height of the lowest tide recorded at a tide station each day during a 19-year recording period, known as the National Tidal Datum Epoch as used by the United States' National Oceanic and Atmospheric Administration.

What is MLLW (Mean lower low water)?

The average of the lower low water height of each tidal day observed over the National Tidal Datum Epoch. For stations with shorter series, comparison of simultaneous observations with a control tide station is made in order to derive the equivalent datum of the National Tidal Datum Epoch.