Table 4-3. Tidal Terms and Definitions 



Term 



Definition 



1) Mean high water 



2) Mean low water 



3) Mean sea level 



4) Mean tide range 



5) Mean tide level 

 Mean water level 



6) Neap tide 



7) Spring tide 



(MHW) the average height of all the high 

 waters recorded over a 19-year period, 

 or a computed equivalent period. 



(MLW) the average height of all the low 

 waters recorded over a 19-year period 

 or a computed equivalent period. 



(MSL) the average height of the surface 

 of the sea for all stages of the tide 

 over a 19-year period, usually deter- 

 mined from hourly readings of tidal 

 height . 



(Mn) the difference in height between 

 mean high water and mean low water. 



(MTL) the mean surface level determined 

 by averaging the height of the water at 

 equal intervals of time, usually at 

 hourly intervals, over a considerable 

 period of time. 



tide of decreased range which occurs 

 about every two weeks when the moon 

 is in quadrature. 



tide of increased range which occurs 

 about every two weeks when the moon 

 is new or full (syzygy) . 



4-19 



10-80 



