Mean low waters refer to the average lowest levels of water reached during the ebb phase or the low tide in a particular area over an extended period. It is a term commonly used in coastal and marine navigation and is crucial for ship operators, marine surveyors, and cartographers.
Mean low waters are determined by measuring the water levels during multiple low tide cycles, typically over a 19-year period, known as a Metonic cycle. This extended time frame helps to account for natural variations like astronomical tides, currents, and weather conditions, which can influence the height of the water.
The measurements taken during these cycles are then averaged to calculate the mean low water. This data provides a reference point for determining the depth of water over shallow areas, such as channels, ports, or harbors. It is also essential for constructing accurate nautical charts, which are vital for safe navigation and preventing ship groundings.
Mean low waters help mariners determine clearance under bridges, ensure safe passage for vessels, and plan docking operations. They serve as a baseline for establishing water depths for various purposes, including dredging operations, calculating draft restrictions, and determining tidal windows for construction projects.
Overall, mean low waters provide valuable information about the lowest water levels in a specific area, aiding in safe and efficient marine operations.
