In Reply Refer To:

Mail Stop 412                                                                                           November 14, 2001




Subject:  National Water Quality System (NWIS) QWDATA Rounding Code—update to fix errors


A script has been written to update the NWIS QWDATA ‘user rounding code’ for several hundred parameter codes.  The ‘user rounding code’ (has been called the precision code) is the integer stored with each result in the database that defines the number of decimal places or significant figures when a user selects the 'user rounding' option for output.

The update will repair problems that were introduced into the ‘user rounding code’ from several sources, including:

   1.  A nationally distributed NWIS field form that inserted a user rounding code of '4' for many field parameters.

   2.  A bug in the code that inserted a ‘user rounding code’ of '3' instead of referencing the parameter code dictionary.

The repair is limited to 'field' data and does not address problems in rounding codes for analytical results.  The parameter code dictionary is the source for the modifications, so the approach to this repair assumes that one rounding array will work for each constituent.  Generally, the parameter codes addressed in the script are:

   1.  Fixed value parameter codes

   2.  Field parameters (typically have a reporting order number less than 60)

   3.  Bacteria parameters

   4.  Field alkalinity and ANC parameters

   5.  Sediment concentration parameters

Detailed instructions for applying this update are located at:

Questions can be emailed to



                          Stephen K. Sorenson

                          Acting Chief, Office of Water Quality

This memorandum does not supersede any other Office of Water Quality Technical Memorandum.

Distribution:  All WRD Employees


Stephen K. Sorenson

Acting Chief, Office of Water Quality

US Geological Survey

412 National Center

Reston, Virginia 20192