What should mariners consider when interpreting mean low water levels?

Mean low water levels are determined by taking the average of the lowest tide levels recorded over a significant period, typically 19 years. This methodology creates a reliable standard for measuring water levels and is crucial for navigational and operational planning. By using this long-term average, mariners can better understand the typical conditions they will encounter and make informed decisions regarding navigation, anchoring, and other maritime activities.

While seasonal variances in tides, weather impacts on tides, and coastal erosion are important factors that can influence water levels, they do not directly dictate the value of mean low water. Seasonal changes can affect tides temporarily but do not provide a consistent average over time. Similarly, weather conditions can lead to immediate fluctuations in tide levels, but they are not part of the long-term averaging process. Coastal erosion can change the topography of the shoreline, potentially affecting future tidal measurements, but does not alter the historical data used to calculate mean low water levels. Thus, the most accurate and useful consideration for mariners regarding mean low water levels is the established average of all low waters over a 19-year cycle.