Tidal Characteristics And Datums In The Sacramento River

A tidal datum is a plane of reference for elevations and water depths determined from measurements of the rise and fall of the tides. Determination of precise tidal datums in tidal rivers, such as the Sacramento River of California, is important for; navigation and hydrographic surveying of the navigable waterways, property boundary determination, and the design of levies and piers. A method is presented to determine statistical tidal datums where water level fluctuations are both tidal and non-tidal. Tidal datums for the 19- year (1960-1978) tidal epoch are computed throughout the ocean/river transition zone of the Sacramento River. This is done through comparison of water level measurements collected over an 18 month period at seven tide stations along the river system to water levels at the long term reference stations at San Francisco and Sacramento. The standard procedure of the National Ocean Survey for comparison of simultaneous observations was used to determine 19-year tidal characteristics as a function of river level. The resulting regression equations and records of long term river levels determine 19-year datums. The accuracy of these tidal datums, indicated by the standard deviation, is within 0.1 foot in the lower bay system and within 0.2 foot upriver.