International Commission on Irrigation & Drainage Commission Interationale des Irrigation et du Drainage



(2034) Tidal water level
Altitude reached by tidal surface, usually subdivided as follows : High water (HW) Highest level reached by a rising tide. Higher high water (HHW) : Higher of the two high waters of any lunar day; the high water, occurring daily during periods when the tide is diurnal, is considered a higher high water. Higher low water (HLW) : Higher of the two low waters of any lunar day. Low water (LW) : Lowest water reached by a falling tide.Lower high water (LHW) : Lower of the two high waters of any lunar day. Lower low water (LLW) : Lower of the two low waters of any lunar day; the single low water, occurring daily during periods when the tide is diurnal, is considered a lower low water. Mean high water (MHW) : Mean level of high waters over a long period. When tide is semi-diurnal or mixed, only higher values are included; in this case, mean high water is the same as mean higher high water. Mean higher high water (MHHW) : Mean level of higher high waters over a long period. Mean low water (MLW) : Mean level of low waters over a long period when tide is semi-diurnal or mixed, only lower low water values are included; in this case, mean low water is the same as mean lower low water. Mean lower low water (MLLW) : Mean level of lower low water over a long period (19 years). Mean high water spring (MHWS) : The average elevation of all high waters of spring tides. Mean low water spring (MLWS) The average elevation of all low waters of spring tides.

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