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Water: Georeferencing

Water Quality Standards GIS Review Implementation: Moving from a Static Website to a Web-based GIS

Anne Marie Miller and Peter I. Ilieve, Research Triangle Institute

The U.S. EPA has committed to developing a national Water Quality Standards (WQS) data system that will locate and describe the official designated uses for the Nation's waters. Research Triangle Institute (RTI) under contract with EPA is developing states' WQS coverages and assisting the states in their review using a web-based approach. Initial implementation was a static website that included Avenue-generated jpegs. One of the lessons learned was that a dynamic mapping site was required to meet the states' review needs. RTI developed a web-based GIS site using MapObjects that will be widely used in this major EPA project.


The U.S. Environmental Protection Agency (EPA) Office of Water is developing a database that will enable EPA, states, tribes, and the public to view water quality standards for U.S. surface waters on the Internet. Previously, water quality standards have been available as parts of detailed state regulations in text form (U.S. EPA, 1999). Since May 1998, the Water Quality Standards Branch of EPA's Office of Science and Technology (OST), in coordination with other EPA offices, has been developing detailed Geographic Information System (GIS) coverages of waters and their water quality standards as well as a national Water Quality Standards Database (WQSDB). These products will allow for the display and spatial analysis of water quality standards information. A complete picture of the locations of waters and their standards will help EPA and state and local governments target their management resources more effectively and provide the public increased and enhanced access to good environmental data.

State water quality standards comprise three parts: (1) designated uses (e.g., protection of aquatic life); (2) chemical, biological, and physical criteria that support the designated uses; and (3) applicable antidegradation provisions (e.g., no new or expanded discharges to outstanding natural resource waters). Displaying water quality standards information involves a two-step process: (1) locating the waters with water quality standards in each state and defining their locations in a GIS; and (2) converting the information in state WQS documents to a database format. Once these two components are in place, they can be linked for presentation via a web interface.

The database behind the website must be developed so the water quality standards information can be linked to a GIS via a unique identifier and displayed in a meaningful way. The GIS component involves locating water quality standards waterbodies in a national surface water coverage such as EPA's Reach File Version 3.0 (RF3) or the National Hydrography Dataset (NHD) Exit EPA Disclaimer , the next generation of reach files. Both RF3 and NHD provide unique identifiers for stream segments that comprise the nation's surface water drainage network (Dewald et al., 1996). The GIS component was developed using dynamic segmentation and the creation of event tables that contain the unique identifiers from the surface water coverage and the unique identifiers from the database (Figure 1). This linkage allows for the display of the designated use and criteria attributes. The process of assigning unique identifiers from the database to unique identifiers in the surface water coverage is known as reach indexing, or georeferencing. For more information on reach indexing refer to https://www.epa.gov/owow/monitoring/georef.

Figure 1. The relationship between the indexing, WQSDB, and surface water coverage (NHD).

Once the database and GIS components are developed, they must be reviewed and quality assured (QA'd) by the states to ensure accuracy in both interpretation of the document and waterbody locations. In the past, CD-ROM data packages were prepared and distributed to the states for review. However, providing the data on the web would allow states to download and view their data in a more timely manner. The website would need to provide states easy access to the water quality standards coverages so that they could provide corrections and feedback. Using a web-based approach, the data can be easily maintained and kept current without having to repeatedly send out CD-ROM data packages. The website also needs to be password protected since draft data are displayed and require state review and approval before becoming public. This paper presents two approaches investigated to deliver the data via the web for review: a static website approach using Avenue-generated jpeg images and a dynamic, web-based GIS approach using a MapObjects application.

Static Website Approach

The WQS Review Site was initially implemented as a static website. A series of Avenue-generated jpeg images were created for each state. A separate jpeg image was created for each designated use. Roads, cities, and streams coverages were also displayed in the image for reference. However, due to the size of the jpeg images and screen resolution restrictions, roads and streams are difficult to see and are not labeled. The cities are labeled for reference. The website allowed state reviewers to navigate to their state and choose an 8-digit U.S. Geological Survey (USGS) Cataloging Unit (CU) watershed to review. The reviewer would then click on a designated use to review using a button menu. The designated uses listed for the state to choose were specific to the particular state. A jpeg image would then highlight the selected designated use within the specified CU (Figure 2).

Figure 2. Example of an Avenue-generated jpeg image showing all the waters with a Drinking Water Supply designated use in the Lower Missouri-Moreau CU.

The HTML files for these web pages were created through Avenue scripts. A table is also displayed below the designated use map that shows which Water Quality Standards waterbodies are highlighted (Figure 3). The unique identifier from the WQSDB and the waterbody name are displayed in the table. This table was also created using an Avenue script that joined the indexing to the WQSDB and queried for the particular CU and designated use of interest.

Figure 3. Table showing the selected waterbodies with a Drinking Water Supply designated use.

The website also contains data for state reviewers to download for further review: CU- and state-level shapefiles of the indexing, a designated use file, and a file containing the water quality standards that were not located and require state advice.

Maintenance quickly became a problem with the static website. As updates were made to the indexing and WQSDB, all of the web pages, tables, and jpeg images had to be re-created. Also, the jpeg images were so small it was difficult to see the designated uses waterbodies for review. States and EPA realized the need for a website where they could zoom in and perform a more detailed online review of the data. A static website was no longer meeting review site requirements.

Web-based GIS Approach

The WQS Review Site was finally implemented using a web-based GIS approach. An internet application was created using MapObjects 1.2, MapObjects Internet Map Server (IMS) 2.0, and Visual Basic 5.0. A SQL Server 7.0 database was created to store the designated uses information. The MapObjects application consists of eight shapefile data layers. Two of the shapefiles contain the water quality standards indexing. The unique database identifier in the shapefiles allows for simple queries to be performed on the database and linked back to the indexing. The following four major areas are included in the main website menu:

First-time Users: Provides a slide show that can be viewed online or downloaded. Terms such as such as waterbody, georeferencing, and spatial indeterminacy are fully discussed. These materials show the benefits of georeferencing waterbodies to a nationally consistent hydrography coverage.

Reach Indexing: Leads to a related educational reach indexing website (https://www.epa.gov/owow/monitoring/georef) where the fundamental concepts of georeferencing and dynamic segmentation are presented in greater detail with demonstrations and examples.

Begin Review: Provides a link to the MapObjects application where states can review and perform QA of their designated uses indexing (Figure 4). A link from the mapping application is also available that allows states to download their data for further review: CU- and state-level shapefiles of the indexing, a designated use file, and a file containing the water quality standards that were not located and require state advice.

EPA: Provides a link to the Agency's website (https://www.epa.gov/).

Figure 4. Dynamic Water Quality Standards Review Website.

The newly added functionality possible with a web-based GIS enables states to perform a more detailed review of their WQS indexing and database. State reviewers have the ability to zoom in, zoom out, and pan to the location of interest. An identify function also allows state reviewers to view the database information (database identifier, waterbody name, and designated use) associated with a selected waterbody. Reviewers can also identify all other available layers: roads, CUs, cities, capitals, counties, and states.

A function is also available to map a user-specified designated use. The "map selected designated use" function allows the reviewer to display all the waterbodies with a specified designated use within a specified CU (Figure 5), presenting a map with the waterbodies highlighted in red that meet the user selection. A table containing the database information appears below the map (Figure 6). The designated use and CU choices are limited to the specified state that the user is reviewing.

Figure 5. All the waters with a designated use of Irrigation in the Lower Missouri-Moreau CU (10300102).

Figure 6. Table showing database information returned from the "map selected designated use" query.

A reviewer can also locate waterbodies by name, choosing from a list of waterbody names in the database for their state. A map (Figure 7) and table containing database information (Figure 8) display all the indexed waterbodies that contain the specified name.

Figure 7. Waterbody name query for the Osage River.

Figure 8. Table showing database information returned from the "map waterbody name" query.

One benefit of this online review is that it allows state staff without GIS capability to assure that the mapping is done accurately. States with GIS capability can download shapefiles of the water quality standards work, either for a more thorough review or for use with other state initiatives. Using a web-based GIS approach, provides states with a more robust way of reviewing their data. Another benefit of this approach is minimal site maintenance. As the database and indexing are updated, the site can easily remain current since the web pages are dynamic.

The next phase of the WQS Review Site will incorporate the chemical, biological, and physical criteria that support the designated uses. Currently these water quality criteria are being populated into the WQSDB. In the future, users will be able to view the linkage between the designated uses and the associated criteria.


Although the web-based implementation was initially much more time consuming, maintenance became much simpler. The benefits from the MapObjects approach far outweigh the additional time spent during the initial implementation. The web-based GIS approach has many advantages:

  1. States without GIS capability can easily review their designated uses indexing in detail.
  2. States with GIS capability can download shapefiles of the designated uses indexing work for more thorough review or use with other state initiatives.
  3. Users can view and identify more layers for a more accurate review.
  4. Users can zoom in, zoom out, and pan to more accurately review the data. The static approach allowed only one CU to be viewed at a time. The dynamic approach allows a user to pan through as many CUs as desired.
  5. The ability to query the database and display the selected designated uses allows for a thorough review.
  6. EPA no longer has to send out CD-ROM data packages every time the data are updated; the review site remains current.
  7. The site can now be easily adapted for reviewing other types of water quality indexing.
  8. One easily accessible location for reach indexing support is now available, with NHD reach indexing updates, National WQS reach indexing status, training and education, etc.
  9. The state/agency review and approval process is streamlined, pointing all interested parties from the respective state agencies to evaluate and provide feedback at the same time on the same coverage.
  10. The opportunity for state cooperation and regional analysis (i.e. between neighboring states, shared watershed, hydro region, or EPA region) is available.
  11. More states are encouraged to be involved and contribute to this national effort (i.e. serves as incentive).

The WQS Review Site implementation has been widely accepted by the states, and EPA will use the same approach for other water quality indexing initiatives in the near future. The review site approach is limited to state review and correction of draft reach indexing work. EPA will provide public access to several types of waterbody-specific spatial information including water quality standards via a new Enviromapper application later in 2000. See also Spoerri et al. in this proceedings for a description of the Reach Indexing Tool developed for georeferencing these various waterbody features.


The work described in this paper was funded by the U.S. Environmental Protection Agency under Contract 68-C7-0056 with Research Triangle Institute (RTI). RTI gratefully acknowledges this support.

Disclaimer: Although the research described has been funded wholly or in part by the U.S. Environmental Protection Agency Contract No. 68-C7-0056 to Research Triangle Institute, it has not been subject to the Agency’s review and therefore does not necessarily reflect the views of the Agency, and no official endorsement should be inferred. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.


Dewald, T.G., C. McKay, S. Hansen, and W. Wheaton. 1996. Managing Watershed Data with the USEPA Reach File. In: Watershed ’96: Proceedings of the National Conference on Watershed Management, Baltimore, MD, June 8-12, 1996. Water Environment Federation, Alexandria, VA.

Spoerri, C., A.M. Miller, and T. Dabolt. 2000 (in press). The Reach Indexing Tool for the National Hydrography Dataset: Functionality and Impacts on State Water Programs. In: ESRI User Conference 2000, San Diego, CA, June 26 -30, 2000.

U.S. EPA (Environmental Protection Agency). 1999. National Water Quality Standards Database. Water Quality Criteria and Standards Newsletter. EPA-823-N-00-001. Spring/Summer 1999. Office of Science and Technology, Office of Water.

Anne Marie Miller
GIS Specialist, Water Quality Program
Research Triangle Institute
3040 Cornwallis Road
RTP, NC 27709
ammiller@rti.org Exit EPA Disclaimer

Peter I. Ilieve
Research Environmental Engineer, Water Quality Program
Research Triangle Institute
3040 Cornwallis Road
RTP, NC 27709
pii@rti.org Exit EPA Disclaimer

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