There are three first-level sub-directories on each of the CD- ROMs. Each directory contains a help file entitled "1st_read.me" that lists the sub-directories and their functions as well as the file contents of the current directory. The DOCFILES sub-directory contains ASCII files giving an overview of WQN, the authors, contacts, and references. The files DATA_ALL.TXT and DATA_DOS.TXT should be consulted by the user for a listing of the relevant ASCII and DOS data files on the CD-ROMs, respectively. The REPORT sub-directory contains the text, figures, and tables of this U.S Geological Survey Open-File Report (96-337). On the ASCII disc, the WQN sub- directory contains ASCII files of all the water-quality, streamflow, and quality-assurance data. These data are available for users unable to use the DOS-compatible search software. On the DOS disc, all data in this sub-directory, with the exception of daily streamflow values, are accessible with the supplied software, GSSEARCH and GSMENU.
On the DOS disc, an additional first-level sub-directory, DOSMENU, contains the files necessary to operate the GSMENU and GSSEARCH software, and includes the WQN data bases accessed by this software.
The following two sections describe the contents of the WQN and DOSMENU sub-directories.
The data in this directory are organized in three subdirectories on the ASCII disc. The sub-directory WQ contains stream monitoring data on water quality and streamflow and ancillary data on monitoring station and watershed attributes. The sub-directory BSP contains the Blind Sample Program data on laboratory measurement bias and variability. Finally, the sub-directory QASURE contains quality-assurance information on network operations and important method changes that may influence the use or interpretation of the WQN stream water-quality data. The contents of each sub-directory are described in the following sections.
WQ sub-directory
ASCII data files in this directory provide ancillary information
on station and watershed attributes as well as several files
describing the collection agencies, laboratories, and methods used to
analyzed the water-quality data. The file "1st_read.me" provides a
complete description of these data files. The format of each data file
is supplied in the sub-directory FORMATS in files with the suffix
"FMT." A few of the key files are highlighted here.
A listing of 121 water-quality constituents and information on the units of measure, chemical expressions, and identifying codes are described in the file WQ_PARM.DAT (instantaneous streamflow is not among the constituents listed, but the data are available in the water-quality files). Attributes of the 679 water-quality monitoring stations and the hydrologic units containing the stations are given in the file WQ_STAS.DAT. Forty-eight of these stations in the NASQAN network were relocated at some time from 1973-95. A listing of these stations, their replacement stations, and dates of station operation are given in the file WQ_RELOC.DAT. A listing of the daily streamflow station for each water-quality site is listed in WQ_FLOW.DAT. Daily streamflow records are collected at most national network sites. The file WQ_FLOW.DAT indicates a nearby alternate site for 79 of the NASQAN stations (19 sites are relocated NASQAN sites), and indicates 25 sites where no records of daily streamflow are available. The attributes of 61 alternate streamflow gaging sites (non-NASQAN) are given in the file FLOWSTAS.DAT (the streamflow record for one NASQAN site is composed of two upstream alternate streamflow sites).
The ASCII water-quality and streamflow data sets are located in 21 sub-directories corresponding to the major hydrologic regions defined by the Water Resources Council (Seaber and others, 1987). Each sub-directory has the name "REGrr" where rr is the first two digits of the hydrologic unit code (HUC) associated with the major regional watersheds (see the HUCS.TXT file for a complete explanation of hydrologic unit codes).
Within each regional sub-directory, the water-quality and streamflow data are organized in separate station and parameter files. The name of each file is "ssssssss.ttt" where "ssssssss" is the eight digit USGS station number and "ttt" refers to a three-character descriptor of the constituent group (see the WQ_PARM.DAT file for a listing of these descriptors). Each constituent has been assigned to a logical physical, chemical, or biological grouping as indicated in the WQ_PARM.DAT file. For example, station files with the suffix of "NUT" contain nutrient water-quality data and files with the suffix of "DMV" contain daily mean streamflow values. Each record in these files gives measurements for a unique date and time except the daily streamflow file where there is one record for each day of the month (31 records for each calendar year). The agency collection and agency laboratory analysis codes are also provided in the water- quality files to allow identification of the agency source of each sample (AGENCIES.DAT and LABS.DAT give explanations). These codes are available generally beginning in the early 1980s. A laboratory analytical method code and remark code is provided with each water-quality value in these files (METHODS.DAT and REMARKS.DAT give explanations of these codes). Method codes are available beginning in 1985.
BSP sub-directory
This directory provides Blind Sample Program (BSP) data for
34 dissolved chemical constituents for the water years 1985 to 1995.
These constituents are listed in the file BSP_PARM.DAT with their
units of measure, chemical expression, and unique identifying codes.
The laboratory analytical method codes corresponding to the BSP
data are listed in the file BSP_METH.DAT.
The estimates of laboratory measurement bias and variability are organized in separate files by constituent group. The name of each file is "BIAS.ttt" or "VAR.ttt" where "ttt" is a three-character descriptor of the constituent group (see the BSP_PARM.DAT file for a listing of this descriptor).
Within each measurement error file, the records are sorted by the laboratory login date, the BSP sample mixture number, and the sequential sample number designating samples of the same mixture analyzed on identical days. For each constituent, five values are recorded: the NWQL measurement of the BSP reference sample, the MPV of the reference sample, the NSD, the measurement error expressed as percent of the MPV, and a remark code to designate estimates of error that are less-than the analytical reporting limit.
Within each measurement variability file, the records are sorted by the beginning and ending dates of login of the samples to the laboratory, and the BSP sample mixture number. For each constituent, five values are recorded: the MPV of the reference sample, the mean, variance, and relative standard deviation (RSD) of NWQL measurements of the BSP reference sample, and the number of observations used to compute the mean and variance statistics for the indicate time interval.
QASURE sub-directory
This directory gives quality-assurance information on network
operation and important changes in field and laboratory methods.
Much of this information is documented by internal USGS
memoranda provided on the discs.
The file QA_MEMOS.DAT (Table 5) gives a brief summary of 60 selected USGS water-quality technical memoranda. Documents are presented for six topical categories: national network implementation memoranda, biological methods, nutrient methods, trace element methods, alkalinity methods, and miscellaneous processing, analytical, and reporting methods. The text for the memoranda are identified by the originating office and a unique number QWyy_nn.TXT (Office of Water Quality) and NLyy_nn (National Water Quality Laboratory), where yy gives the year of the document and nn is a sequential number or character identifying the year's memoranda.
The files QA_FLD.TXT (Table 4) and QA_LAB.TXT (Table 8) give a summary of the most important changes in field and laboratory methods and sample contamination that could affect the use and interpretation of WQN data. The contents of these files are organized alphabetically by constituent type and chronologically within each constituent. For each entry, we provide a date, a brief summary of the event, and a reference to key memoranda or publications.
The GSMENU software allows the user to search the WQN data base using the program GSSEARCH. A logical query of any of the items in up to 15 datafiles may be executed. All data are retrievable from GSSEARCH or browsable from GSMENU except for the streamflow data, which can only be accessed from the ASCII disc using user-provided software. Some of the items available for searching the water-quality data include, for example, station name and other station attributes (e.g., county/state, hydrologic unit code, drainage basin 1990 population and 1987 land cover, latitude, longitude), date, constituent name, and the remark code, method code, collection agency code, laboratory analysis code, or value of the water-quality constituent. The software allows the selected data that satisfies the query conditions to be output in a variety of formats including dBASE, flat ASCII, delimited ASCII, or fixed-field. Instructions for the use of GSSEARCH are provided as text in this directory and as on-line help.
The GSMENU system may be used to browse the contents of 69 data files containing national network and quality-assurance information. These files include the water-quality memoranda in the QASURE sub-directory, several text files in the WQ sub-directory (consisting of Tables 2, 3, 6, and 7), and the files QA_FLD.TXT (Table 4), QA_LAB.TXT (Table8), and QA_MEMOS.TXT (Table 5) in the QASURE sub-directory.