Water Level Methodology

Water levels at locations remote from operating water level gauges are estimated using the discrete 
tidal zoning methodology implemented by the NOAA Center for Operational Oceanographic Products 
and Services (CO-OPS). Tidal zoning methodology extrapolates observed water levels to a location 
of interest using correctors for estimated time differences in the time of high and low tides 
and correctors for estimated difference in the range of tide. Time and range correctors are 
based on a geospatial mapping analysis of the co-tidal lines depicting how the tide progresses 
through an estuary or embayment. Discrete tidal zones are typically established to resolve 0.3 ft. 
differences in range of tide and 0.2 hours change in the time of tide. For planning purposes, these 
correctors can be applied to the predicted tide at a tide station. For final correctors, the tide 
is extrapolated to the area of interest using the correctors applied to the verified observations 
at the tide station. Success in the tidal zoning methodology depends upon similar tidal 
characteristics and similarity in the response of the water levels to weather.