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, and impacted data products from March 27, 2002 to August 4, 2021. Water level products from August 4, 2021 to present, including real-time data, are correct. We are currently working on correcting the historical water level data and downstream products and aim to have them updated by 2024. We will provide a notification once the historical data products have been updated. Any data products downloaded from this time will need to be re-downloaded. 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 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 (Jun 16 2017)
Units: Feet
Control Station: 9439040 Astoria, OR
T.M.: 0
Epoch: 1983-2001
Datum: MLLW
DatumValueDescription
MHHW3.23Mean Higher-High Water
MHW2.75Mean High Water
MTL1.49Mean Tide Level
MSL1.49Mean Sea Level
DTL1.62Mean Diurnal Tide Level
MLW0.23Mean Low Water
MLLW0.00Mean Lower-Low Water
NAVD88
CRD_OFFSET-2.03Columbia River Datum Offset
STND-2.05Station Datum
GT3.23Great Diurnal Range
MN2.52Mean Range of Tide
DHQ0.49Mean Diurnal High Water Inequality
DLQ0.22Mean Diurnal Low Water Inequality
HWI0.04Greenwich High Water Interval (in hours)
LWI7.86Greenwich Low Water Interval (in hours)
Max Tide13.29Highest Observed Tide
Max Tide Date & Time03/30/2017 18:48Highest Observed Tide Date & Time
Min Tide-2.35Lowest Observed Tide
Min Tide Date & Time09/21/2003 20:48Lowest Observed Tide Date & Time
HAT4.11Highest Astronomical Tide
HAT Date & Time12/22/2003 23:24HAT Date and Time
LAT-0.71Lowest 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