=========================== FOLLOWING PSMSL DOCUMENTATION ADDED 07-Apr-1999
data for 1963-85 referred to Normal Null data for 1986- referred to TGZ
=========================== FOLLOWING PSMSL DOCUMENTATION ADDED 25-Jun-2001
Wittduen - data 1963-85 apparetnly corrected to NN (Normal Null).
=========================== FOLLOWING PSMSL DOCUMENTATION ADDED 09-Aug-2010
The data for Wittduen was measured to Normal Null which is a German datum related to levels at Potsdam near Berlin. It is similar to ODN in the UK and the NAP in Holland. It is unusual therefore that the station has been made RLR as it 'breaks the rules' of RLR. Data 2000 onwards refers to TGZ.
=========================== FOLLOWING PSMSL DOCUMENTATION ADDED 22-Jan-2016
Removed documentation dated 2001 Apr 11 stating "Data up to 1997 were high and low waters (mean tide level). MSL thereafter."  Review of the documentation indicates that data through 1998 is MTL, with MSL 1999 onwards.
=========================== FOLLOWING PSMSL DOCUMENTATION ADDED 26-Jan-2016
A value of MTL-MSL=-121 mm has been applied to the RLR data for the period 1963-1998.  This value was derived from the entire time series (through 2008) by Thomas Wahl, using the "k factor method" described in Wahl et al., 61, 701-715, 2011.
=========================== FOLLOWING PSMSL DOCUMENTATION ADDED 15-Nov-2017
Data for 2011 onwards has been supplied using RLR as the datum. Therefore no adjustment needs to be applied to the data.
=========================== FOLLOWING PSMSL DOCUMENTATION ADDED 11-Sep-2019
The complete dataset for this station has been supplied by the Federal Waterways and Shipping Administration, provided by the Federal Institute of Hydrology.