This electronic report contains current (water year 2004) and historical hydrologic, biologic, and meteorologic data for Illinois. Data include records of discharge, stage, water quality and biology of streams; stage of lakes and reservoirs; levels and quality of ground water; and records of precipitation, air temperature, dew point, solar radiation, and wind speed. Data were collected and compiled as a part of the National Water Information System (NWIS) maintained by the U.S. Geological Survey, in cooperation with Federal, State, and local agencies.

All data published in previous years' CDs are copied into the current year's CD.  Therefore, the most recent CD supersedes previous CDs.

The electronic report offers more information and features than traditional printed Water-Data Reports. The following is a list of the general features available on the electronic report:

1. data provided as traditional annual data tables,
2. data provided as text files,
3. data grouped by data type,
4. annual data tables for water years 1998 to current,
5. daily values for the period of record,
6. gage values for water years 1994 to current,
7. station descriptions that contain a list of all data available for a station,
8. station descriptions provided separately from data tables,
9. ability to sort station lists by station number or name,
10. a dynamic map with zooming capabilities,
11. peak flows,
12. access to real-time data, and
13. ability to generate a printed Water-Data Report

Data are arranged on the electronic report by data type, station number or name, and year. When the electronic report is accessed, the general data types listed in the first selection window (Brief Table of Contents) include "Surface Water", "Ground Water", "Meteorological", and "Biological".  If interested in surface-water data, for example, "Surface-Water Data" would be selected. The two data types in "Surface-Water Data" include "Water Discharge and Stage" or "Water Quality". "Water Discharge and Stage" provides the additional data types "Water Discharge", "Water Stage", "Partial Record", and "Peak Flow". Below "Water Discharge", for example, are the following choices: "Annual Tables", "Daily Values", "Gage Values", and "Real-Time".

Data contained in "Annual Tables" include the traditional annual-data tables for water years 1998 to current.

"Daily Values" of discharge contain the period of record of mean-daily discharges for each site that has approved data available from the USGS Illinois Water Science Center's computer system. These daily values are provided as text files.

"Gage Values" include those recorded, transmitted, and/or computed from a gaging station and typically are 5-, 15-, or 30-minute data.  These data are provided as compressed files by an Internet connection, and generally available for water years 1994 to current.  To view a gage-value file, save the compressed file to your computer then uncompress it with extraction software such as WinZip or Gzip.

"Real-time" is a link that has been provided on the "Surface-Water Data", "Ground-Water Data", "Meteorological Data", and "Available Data" pages that accesses the National Water Information System (NWIS) real-time data Web site, if an Internet connection is available from your computer. Accessing the NWIS real-time Web site from the "Surface-Water Data", "Ground-Water Data", and "Meteorological Data" pages will display a summary page of the current gage values at the applicable telemetered sites. Accessing the NWIS real-time Web site from an "Available Data" page displays hydrographs of current gage values for all the data types collected at the particular site. Many other forms of data retrievals and options for displaying the data also may be available on this page.

"Peak flow" contains text files of annual maximum peak discharge and their associated stage values for the period of record. Also, secondary instantaneous peak discharges and their associated stage values above a selected base discharge are available if the flow above the gage is not appreciably regulated. The base discharge generally is selected such that, on average, three secondary peak-flow discharges, including the annual maximum peak discharge, will exceed the base discharge each water year. Also, if the maximum peak stage occurred at a different time than the annual maximum peak discharge, it also is listed. The specific criteria for (1) deciding which gaging stations should have secondary peaks (2) selecting the base discharge,  and (3) selecting secondary peaks greater than the base discharge are given in Novak (1985).

The section "Station Descriptions" in the first selection window (Brief Table of Contents) provides information about each station, such as station location, period of record, extremes for period of record, and other remarks pertinent to the station. This section provides station descriptions separate from annual data tables.

Selecting "Annual Tables," "Daily Values," or "Gage Values" under a general data type will provide a list of stations with available data. The list of stations includes the period of record in years. Stations can be sorted by station number or name. Below the title of the station list, the sort order can be changed by selecting "(Station list by name)" or "(Station list by number)." Select a station name or number to obtain a list of the available data for that station. On the "Available-Data" page are two groups of data choices for the selected station. The first group (top of page) contains a list of the data choices for the currently selected data type. The second group (below the first group) lists the additional data that are available for the station.

A map is available that shows stations that have data. There are two areas where map links can be found. There is a link in the upper right corner of the first selection window (Brief Table of Contents). If a general data type such as "Surface-Water Data" is selected, map links, where applicable, also can be found beside each data type (for example, "Water Discharge"). When a map link is selected, the initial stations shown on the map are those with available data for the data type selected and the current year. The map offers seven main options as follows:

1. display stations by data type,
2. display features such as streams,
3. find stations by station number or map feature,
4. display stations by year(s) of available data,
5. increase or decrease text or symbol sizes,
6. zooming and panning capabilities, and
7. link to the "Available Data" page.

Stations can be found on the map by using the "Find" function. To use the "Find" function, enter numbers (for example, the station number or part of the number) and/or text (for example, the station name or part of the name) into the "Find" box and select the "Go" box. The "Find" function will locate any stations and any loaded features that contain the exact numbers and/or text entered into the "Find" box. Features are loaded once they are selected with the small check box. The red bullseye will show the location of the first station or feature found. If more than one station and/or feature is found, stations are located first followed by map features. In addition, the "next" or "prev" boxes can be used to locate the next site (station or feature) or previous site, respectively. The "clear" box is used to reset the "Find" function so different sites can be located.

If you are interested in stations with data for a certain year or period of time, you can use the "Show Stations by Year(s)" function. Enter a year or years in the box provided to locate stations with data for the desired year(s). The current year (default) in the box can be changed by (1) selecting the box, (2) using the "Backspace" key to erase the year, (3) typing the new year or period desired, and (4) pressing the "Enter" key. This function will not limit stations located by the "Find" function discussed in the previous paragraph. The "Find" function will locate any stations published in the report whether or not it is being shown on the map. All stations (current and discontinued) for the data type(s) selected can be shown on the map by selecting the "All years" button.

Text and symbols on the map can be increased or decreased in size. The "+" and "-" symbols in the "Size" function are used to increase or decrease the size of the text or symbols, respectively. The "Size" function can change the size of text on the map whether or not it is visible. Text of station numbers and map features will appear on the map after zooming for more detail.

The map offers zoom and pan capabilities. By using the "Zoom" bar, you can increase or decrease the detail of the map. The "Fit to Window" button located under the "Zoom" bar is used to set the map to the original size. The map can be repositioned by panning. Panning is done by holding down any mouse button and moving the mouse in the direction you want the map to move. When panning, a black bullseye will appear on the map designating the center of the map window. The bullseye is the location on the map that will appear in more detail when pulling down the zoom bar. Therefore, the black bullseye is useful for positioning a desired site within the bullseye prior to zooming.

When a station or feature is pointed to by the cursor, the name of the station or feature appears below the map. Selecting a station on the map will display the "Available Data" page for that station.

At the bottom of most selection windows is a navigation bar that includes  "Table of Contents," "Introduction," "Station Descriptions," "Surface-Water  Data," "Ground-Water Data," "Meteorological Data," and "Biological Data."  This navigation bar allows quick transfer to other sections and data types.

A print-on-demand feature prints a paper copy very similar to the traditional printed Water-Data Report for the current water year.  This printable format of the report contains the same introductory sections as the electronic report and presents traditional annual tables of surface-water, ground-water, meteorological, and biological data collected during the current water year. To print this document, the user will find the link to the "Printable Water-Data Report" page under the title of the first selection window ("Brief Table of Contents" page).

The traditional printable version of the Water-Data Report is stored in the electronic report as an Adobe® PDF® document.  This PDF® document contains the introductory sections of the report, all data tables, and maps showing the data-collection sites for the current water year.  The user must have Adobe® Acrobat® Reader® installed on the computer. This software may be freely obtained from the following Internet URL (http://www.adobe.com/products/acrobat/readstep2.html).  Once Adobe® Acrobat® Reader® is available on the computer, select the link called "Printable Report" found on the "Printable Water-Data Report" page that will open the PDF® document.  Allow time for the document to open and  select Print from the File menu.   NOTE: The complete printed document may exceed 1,000 one-sided pages.