Notice: CO-OPS recently determined that water level data from St Helens (9439201) 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 9439201, St Helens OR

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: 9439201, St Helens, OR
Status: Accepted (Apr 2 2024)
Units: Feet
Control Station: 9439040 Astoria, OR
T.M.: 0
Epoch: 1983-2001
Datum: MLLW
MHHW3.21Mean Higher-High Water
MHW2.73Mean High Water
MTL1.48Mean Tide Level
MSL1.47Mean Sea Level
DTL1.60Mean Diurnal Tide Level
MLW0.23Mean Low Water
MLLW0.00Mean Lower-Low Water
NAVD88-6.06North American Vertical Datum of 1988
CRD_OFFSET-1.78Columbia River Datum Offset
STND-1.80Station Datum
GT3.21Great Diurnal Range
MN2.50Mean Range of Tide
DHQ0.48Mean Diurnal High Water Inequality
DLQ0.23Mean Diurnal Low Water Inequality
HWI0.07Greenwich High Water Interval (in hours)
LWI7.88Greenwich Low Water Interval (in hours)
Max Tide13.54Highest Observed Tide
Max Tide Date & Time03/30/2017 18:48Highest Observed Tide Date & Time
Min Tide-2.10Lowest Observed Tide
Min Tide Date & Time09/21/2003 20:48Lowest Observed Tide Date & Time
HAT4.09Highest Astronomical Tide
HAT Date & Time12/22/2003 23:24HAT Date and Time
LAT-0.72Lowest Astronomical Tide
LAT Date & Time08/21/2009 20:36LAT Date and Time
Tidal Datum Analysis Periods
08/01/2002 - 11/30/2002
07/01/2003 - 11/30/2003
07/01/2004 - 11/30/2004
08/01/2005 - 10/31/2005
08/01/2006 - 10/31/2006
08/01/2007 - 11/30/2007
08/01/2008 - 10/31/2008
08/01/2009 - 10/31/2009
08/01/2010 - 10/31/2010
09/01/2011 - 12/31/2011

Products available at 9439201 St Helens, OR