Discrete Water-Quality Data in NWISWeb

In Reply Refer To:
Mail Stop 412                                      September 15, 2000

Office of Water Quality Technical Memorandum 2000.10

Subject:  Discrete Water-Quality Data in NWISWeb

The NWISWeb software has been tested internally by the Water Resources
Division (WRD) over the last few months and will be made available to the
public on September 18, 2000.  All discrete water-quality data through
September 30, 1999 will be available, with some limitations.  These
limitations and a few points on future plans for water-quality data in
NWISWeb are described below, particularly to help those who may have to
answer questions from the public about the data.  Listed at the end of this
memorandum are two specific steps (and one optional step) Districts should
perform to improve the data available on NWISWeb.

The water-quality data were retrieved by each District in May 2000 and
provided to NWIS.  Some data were excluded from the Web-accessible data set
for a variety of reasons.

1.   District Processing Status:  All data with a code of 'R' (ready to
transmit) or 'T' (transmitted) were initially retrieved.  Samples coded as
'Z' (local only) were excluded from the retrieval.

2.   Analysis Status:  All samples with a code of '9' (proprietary) for the
Analysis Status were removed from the NWISWeb database.  Although it is
suspected that these samples were coded erroneously as proprietary data,
all such sample data were excluded (to err on the side of caution).  Refer
to John Brigg's July 6, 2000 email for information regarding the number of
samples in your District coded "proprietary," and steps to take review
these samples.

3.   Unapproved method data:  Data analyzed by unapproved methods at the
National Water Quality Laboratory (NWQL), and other U.S. Geological Survey
labs were screened from the NWISWeb database.  The specific parameter code
and method code combinations that were screened are listed at the following
web location:


4.   Water Year (WY) 2000 data:  These data are not included in this
release for several reasons. First, much of these data are preliminary.
WRD policy (WRD 95.19) for release of preliminary water-quality data on the
web that may exceed regulatory standards and for required quality control
are not in place. Also, the capability to update discrete water-quality
data is not included in this release of NWISWeb. Current plans are to
retrieve and reload the water-quality data in the spring of 2001. Plans are
being made to develop appropriate policies and to put a timely data reload
process in place for water-quality data, so that our current water-year
data can be included in the future.

5.   Site Flag:  Districts have the capability to set a flag in the
sitefile to prevent the display of all data from that site on the Web. The
sitefile in NWISWeb is reloaded frequently, and changes to this site flag
will determine whether or not any data, including water-quality data, can
be viewed.

The water-quality data provided to NWISWeb were retrieved without rounding.
NWQL data stored in NWIS since April 1997 have been stored as 'raw' or
unrounded values, and the exact nature of those raw values has varied with
analytical method.  NWISWeb currently displays the unrounded data. During
the last three years, the data may indicate much more precision than is
'real.'  The spring 2001 retrieval and reload using NWIS 4_1 will provide
rounded values to NWISWeb.

Most of the selection options in this first release of NWISWeb are
site-based criteria. The only chemistry-based data selection option is a
parameter group.  There are suggestions for retrieving the data in the help
sections of NWISWeb.  Additional selection criteria more tailored to
discrete water-quality data will be included in the next release.

A data refresh is planned for October 2000. The refresh is required for two
reasons.  First, if the site flag was turned off at the time of the
original load of water-quality data, no data will be loaded for that site.
The refresh provides an opportunity to add that data.  Second, some
Districts would like to provide a fresh retrieval of their data. Districts
will need to decide whether to make a new retrieval or stay with the data
already retrieved in May. Those sites that have cleaned up their data since
May 2000 should do a new retrieval.  All sites will be asked to retrieve
their data again in the Spring of 2001.  At that time, WY 2000 data will be
added to NWISWeb.

This implementation of the discrete water-quality system of NWISWeb is a
first step.  There are many improvements to be made and new capabilities to
be added to this system.  An NWISWeb User Group will work with the NWISWeb
development team, the Water Quality User Group (a.k.a. the Phoenix Group),
and representatives from the water quality user community to define the
requirements and prioritize their implementation.  Mark Brigham (Minnesota
District, Phoenix member), and Mark Nilles (Office of Water Quality,
Atmospheric Deposition Program Coordinator) are the specific water-quality
representatives on the NWISWeb User Group.

District ACTIONS for NWISWeb water-quality data:

1.   Check site flag status before the NWISWeb refresh in October 2000.
2.   Check the validity of any samples with an analysis status code of "9"
(proprietary) and make corrections so these samples will be included in the
data retrieved this fall (optional) or next spring.
3.   Optional: Make a new retrieval of your District water-quality data for
   October 2000 refresh.

                              Janice R. Ward /s/
                              Acting Chief, Office of Water Quality

This memorandum does not supercede any other OWQ Technical Memorandum.

Distribution:  All WRD Employees

(See attached file: techmemo0010.doc)
Janice Ward
Acting Chief, Office of Water Quality
US Geological Survey
Reston, VA