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Chapter V
Geographic Information System Database

The final phase of this project was to create a Geographic Information System (GIS) database from USEPA's system and source tables. A GIS is a computerbased system that captures, stores, edits, manipulates, analyzes, synthesizes, and displays geographically referenced information (Burrough, 1985). This project's GIS database includes PWS source locations, roads, streams, cities, and counties as data layers. In producing the GIS, it was necessary for all layers to have a common datum, projection, and units. Since the GPS collected data were created in decimal degrees using a geographic projection with reference to the WGS84 datum, these parameters were applied to all data layers.

Due to compatibility with DEQ, the GIS software utilized in this project was ArcView by Environmental Systems Research Institute (ESRI), Inc. ArcView is a "point & click" GIS software that allows for ease and efficiency in querying, displaying, and updating GIS data. Both the system and source tables were placed within the GIS. Source locations provided the spatially referenced data with a link being established to the system attributes. This provided a methodology to quality check the data by comparing source locations with their corresponding system local descriptors (i.e. street, city, county, etc.).

In order to create the PWS sources data layer, the decimal degree latitude and longitude fields from the source table were used. By applying the add event theme action in ArcView, these fields were chosen to represent x, y for the layer and placed within the GIS along with the other associated attributes (fields). This direct link to the source and system database files allows for future updates to be made directly to the table using a database software or through ArcView. Either method provides for the new positions or attributes to be incorporated automatically within the GIS. All other data layers were pre-existing GIS layers developed by the WWRC GIS Lab.

With a majority of the sources located, additional future research can be focused on developing a customized graphical user interface (GUI) specific to PWS data. When notified by the USEPA Safe Drinking Water Program of PWS updates, changes, and/or additions, DEQ/WQD would have the ability to directly place these changes within the GIS and maintain a up-to-date, dynamic database. The USEPA could also benefit by utilizing this interface to aid in monitoring and regulating Wyoming PWSS. Finally, a GUI would allow for a quicker and easier methodology for querying the data.

Other future work could be concentrated on the use of GIS for delineating wellhead protection areas. This approach which has been utilized in various States (Rifai, et. al., 1993) allows for a systematic and efficient method to be developed in determining appropriate Wellhead Protection Areas (WHFAS) for PWSS. Lastly, as changes occur within WHPAS, GIS provides the capabilities necessary to make these updates and produce refined protection areas in the manner of minutes.

In summary, the GIS mapping of PWS systems has the potential to help facilitate the following:

For many PWSs it will be necessary to collect a variety of additional attribute data relating to each source in order to perform the activities described above. However with accurate locations present within the database, the ability to combine spatial data layers enhances and expedites this attributing process. Therefor it becomes vital for this database to have consistent accuracy standards throughout the records. It was noticeable when examining source locations within the GIS that accuracy fluctuated in respect to previously located sources. This discrepancy is directly related to the varying methods and techniques employed in collecting the locations. A need exists to standardize location accuracy for all sources found in the database in order to effectively and confidently utilize this database to its full potential. By maintaining this accuracy assurance and control, the role of GIS in monitoring, regulating, and protecting PWSs throughout Wyoming will continue to develop in the upcoming years.

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