Use of parameter-method code pairs in the National Water Information System (NWIS) and the process for requesting parameter codes and method codes
In Reply Refer To:
Mail Stop 412
March 27, 2003
Office of Water Quality Technical Memorandum 2003.01
Subject: Use of parameter-method code pairs in the National Water
Information System (NWIS) and the process for requesting
parameter codes and method codes
The purpose of this memo is to describe the way parameter code-method
code pairs are used for rounding purposes in National Water-Quality
Information System (NWIS), an enhancement that was added in NWIS version
4.2. The process for assigning new and/or updating existing parameter
and method codes is also described.
Use of parameter-method code pairs in NWIS water-quality software:
The NWIS water-quality software (QWDATA) uses a reference table of
parameter-method code pairs for most rounding scenarios and, during data
entry, performs a check against the reference table for valid
parameter-method code pairs. Batch entry of an invalid parameter-method
code pair causes the assignment of a 'blank' method code for that result
in the database. During the transfer to the NWIS 4.2 software, invalid
method codes were allowed to exist in historical records. Invalid
parameter?method code pairs are rounded using rounding specifications
associated with a 'blank' method code. The rounding specifications
associated with the 'blank' method are typically less precise than recent
methods and, consequently, the use of 'blank' method rounding may not be
appropriate for newer, more precise methods. Therefore, the reference
table maintained within NWIS and used for validation must contain all
legitimate parameter-method code combinations, and their associated
rounding arrays, in order for data to be properly rounded in tables and
Method code descriptions are currently not an integral part of the NWIS,
so this information will be maintained externally until it can be added
to the software. The external file can be obtained from:
Process for requesting new and updated parameter codes and method
The process for requesting new and updated parameter codes, as described
in Office of Water Quality (OWQ) Technical Memorandum 96.08, has become
obsolete. The current process for requesting new codes is outlined
1. Requests for new and/or updated parameter codes and method codes are
to be submitted to the Office of Water Quality by completing the
information listed in a spreadsheet named "pcode.request.xls." The
spreadsheet can be obtained via ftp as follows:
[login as] anonymous
These instructions can also be found on the internal Office of
Water Quality (OWQ) home page at:
Mandatory information for the assignment of new parameter codes
Mandatory information for the assignment of new method codes includes:
- Constituent name.
- Sample medium (e.g., water, biota, etc.), or matrix, or biological
tissue type or body part.
- Reporting units.
- Lowest reporting level at which at least one significant figure is
- Maximum number of significant digits to be shown in output.
Additional information can be entered if it is known. This same
spreadsheet is used to request updates to existing parameter and
2. The completed spreadsheet should be sent via electronic mail to Ken
Pearsall, New York District (email@example.com). Ken will assign new
parameter codes, update existing parameter codes, forward requests for
new and updated method codes to Pete Rogerson (senior chemist, OWQ), and
maintain the parameter-method code reference list for NWIS.
3. Pete Rogerson will assign new method codes and make any requested
updates to the method codes and will forward these codes to Ken for
inclusion in the parameter-method code pair reference table.
4. Ken will submit the revised Parameter Code Dictionary (PCD), method
code reference list, and parameter-method code pair reference table to
the NWIS team.
5. To keep data processing as up-to-date as possible, the NWIS team will
release the updated PCD, method code reference list, and parameter-method
code pair reference table at least quarterly for the Districts to install
on their NWIS systems.
Questions should be directed to Yvonne Stoker (firstname.lastname@example.org). Errors
and requests for changes to NWIS other than a parameter code-method code
request should be entered into the NWIS 'Gnats Problem Report Management
Chief, Office of
This memorandum supercedes OWQ Technical Memo 96.08.
Distribution: All WRD Employees
(See attached file: OWQ 03.01 pcode-method_management.doc)
Timothy L. Miller, Chief, Office of Water Quality
U.S. Geological Survey
412 National Center
Reston, VA 20192
- Parameter code(s) associated with the method.
- Method short name.
- Method citation.
- Identification as a field or a lab method.
- Lowest reporting level at which at least one significant figure is shown.
- Maximum number of significant digits to be shown.