For Clarification:

If you look at the charts in the following link you will see that the river in the Mount Vernon area just above I-5 where the guage is located is almost exclusively influenced by the flow from the dams.

http://waterdata.usgs.gov/wa/nwis/uv/?station=12200500

The obvious fluction of about 3000 CFS reflects the 4000 CFS fluctuation in the flow from the Lower Baker Dam about 50 miles up river. A practiced eye can also see the flow variation resulting from lesser fluctuations in the dam at Newhalem.

The tidal influence at the Mount Vernon guage is minimal and measured in fractions of an inch in river level. It can rarely be seen on the charts and then only during extremely low river flows when the dams are running steady or closed for extended periods and we are experiencing peak tidal movement due to the lunar cycle.

Below the Memorial Hwy bridge the tidal influence becomes more obvious and increases as you travel towards and below the forks. By the Fir Island Bridges on either fork the tidal influence has become the predominant factor.


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