Mean Low Water (MLW) is calculated by averaging low water heights observed over time. According to the provided reference, it's the arithmetic mean of the low water heights observed each tidal day.
Here's a breakdown:
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What is Mean Low Water (MLW)? It is a tidal datum, meaning it's a standard elevation used as a reference point for measuring water depths and heights.
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Calculation: The process involves recording the height of the low water mark each day and then calculating the average of those heights.
- Data Collection: You need a consistent record of low water heights.
- Averaging: Add up all the low water heights recorded during the observation period.
- Divide: Divide the sum by the total number of observations (days).
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Example: If you recorded the following low water heights over 5 days (in feet): 2.1, 1.8, 2.3, 2.0, 1.9.
- The sum is 2.1 + 1.8 + 2.3 + 2.0 + 1.9 = 10.1
- The mean low water is 10.1 / 5 = 2.02 feet.
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Relationship to Other Tidal Datums: MLW is also used in calculating other tidal datums such as Mean Tide Level (MTL). The provided reference states that MTL is the average of the Mean High Water (MHW) and MLW elevations.
