NOTICE: CO-OPS recently determined that water level data from Longview (9440422) 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 October 21, 2015 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 October 21, 2015 to present, including real-time data, were not impacted. If you have any questions, please send an email to Tide.Predictions@noaa.gov and we will get back to you as soon as possible.

Datums for 9440422, Longview 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: 9440422, Longview, WA
Status: Accepted (Sep 20 2023)
Units: Feet
Control Station: 9439040 Astoria, OR
T.M.: 0
Epoch: 1983-2001
Datum: MLLW
DatumValueDescription
MHHW4.47Mean Higher-High Water
MHW4.01Mean High Water
MTL2.17Mean Tide Level
MSL2.02Mean Sea Level
DTL2.24Mean Diurnal Tide Level
MLW0.33Mean Low Water
MLLW0.00Mean Lower-Low Water
NAVD88
CRD_OFFSET-2.06Columbia River Datum Offset
STND-2.33Station Datum
GT4.47Great Diurnal Range
MN3.67Mean Range of Tide
DHQ0.47Mean Diurnal High Water Inequality
DLQ0.33Mean Diurnal Low Water Inequality
HWI11.21Greenwich High Water Interval (in hours)
LWI6.55Greenwich 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
HAT5.25Highest Astronomical Tide
HAT Date & Time11/24/2003 23:06HAT Date and Time
LAT-0.83Lowest Astronomical Tide
LAT Date & Time01/12/2009 07:42LAT Date and Time
Tidal Datum Analysis Periods
08/01/2002 - 10/31/2002
08/01/2003 - 10/31/2003
07/01/2004 - 11/30/2004
08/01/2005 - 10/31/2005
08/01/2006 - 10/31/2006
08/01/2007 - 11/30/2007
09/01/2008 - 10/31/2008
08/01/2009 - 10/31/2009
08/01/2010 - 10/31/2010
09/01/2011 - 10/31/2011


Products available at 9440422 Longview, WA