NOTICE: CO-OPS recently determined that water level data from Skamokawa (9440569) contained an error due to the conversion of pressure to water level in our database. This error resulted in water level measurements several centimeters higher than actual. Impacted water level products from March 27, 2002 to August 4, 2021 have now been corrected, including 6-minute water level data, hourly heights, highs/lows, monthly means, and tidal datums. Any data products downloaded from this time will need to be re-downloaded. Water level products from August 4, 2021 to present, including real-time data, were not impacted. If you have any questions, please send an email to and we will get back to you as soon as possible.

Datums for 9440569, Skamokawa WA

Columbia River Datum Columbia River Datum (CRD) is the adopted fixed low water reference plane for this area. CRD is a U.S. Army Corps of Engineers non-tidal datum defined at distinct river miles relative to NAVD88, and is used as chart datum above river mile 23 on the Columbia River. Datums are computed using observations from the low river stages of the year, generally August through October due to the masking of the tidal signal from strong seasonal river runoff during other portions of the year. Depending on river flow, water levels can be significantly higher than Columbia River Datum. As of 2014, the U.S. Army Corps of Engineers provided updated offsets for CRD that have been applied to this station. Station Datum (STND) is no longer set equal to CRD.
NOTICE: All data values are relative to the MLLW.

Elevations on Mean Lower Low Water

Station: 9440569, Skamokawa, WA
Status: Accepted (May 3 2023)
Units: Feet
Control Station: 9439040 Astoria, OR
T.M.: 0
Epoch: 1983-2001
Datum: MLLW
MHHW7.35Mean Higher-High Water
MHW6.73Mean High Water
MTL3.74Mean Tide Level
MSL3.66Mean Sea Level
DTL3.67Mean Diurnal Tide Level
MLW0.76Mean Low Water
MLLW0.00Mean Lower-Low Water
NAVD88-1.74North American Vertical Datum of 1988
CRD_OFFSET-0.49Columbia River Datum Offset
STND-0.43Station Datum
GT7.35Great Diurnal Range
MN5.96Mean Range of Tide
DHQ0.62Mean Diurnal High Water Inequality
DLQ0.76Mean Diurnal Low Water Inequality
HWI9.94Greenwich High Water Interval (in hours)
LWI4.38Greenwich Low Water Interval (in hours)
Max TideHighest Observed Tide
Max Tide Date & Time Highest Observed Tide Date & Time
Min TideLowest Observed Tide
Min Tide Date & Time Lowest Observed Tide Date & Time
HAT9.29Highest Astronomical Tide
HAT Date & Time12/15/2039 21:00HAT Date and Time
LAT-1.78Lowest Astronomical Tide
LAT Date & Time07/31/2000 17:06LAT Date and Time
Tidal Datum Analysis Periods
08/01/2002 - 10/31/2002
07/01/2004 - 09/30/2004
08/01/2005 - 10/31/2005
07/01/2006 - 10/31/2006
08/01/2007 - 11/30/2007
09/01/2008 - 10/31/2008
07/01/2009 - 10/31/2009
07/01/2010 - 10/31/2010
08/01/2011 - 09/30/2011
08/01/2012 - 10/31/2012

Products available at 9440569 Skamokawa, WA