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Wyoming Ground Water Vulnerability Mapping Project |
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Aquifer Sensitivity refers to the ease with which a contaminant placed on or near the soil
surface can reach the shallowest water-bearing layer. Potential contaminants include non-point
sources such as agricultural pesticides, fertilizers, and feedlot runoff as well as point sources such as
automotive service garage floor drains and shallow septic systems. Assessing ground water
vulnerability involves taking the sensitivity modeling process one step further by adding
potential contaminant sources. The project was initiated in 1992 by the Wyoming Department
of Environmental Quality's Water Quality Division, in cooperation with the University of
Wyoming's Water Resources Center, the Wyoming State Geological Survey, and the US Environmental Protection Agency. The final report was completed in 1998 and
CD-ROM products, maps,
and digital data are available as of Sept. 1999. The ultimate goal of this project was to
develop a dynamic, GIS-based tool to aid in planning, decision-making, and public education
relative to the management of ground water resources and maintenance of ground water
quality in Wyoming.
In addition to the required layers many "intermediate" and cartographic base
layers were required which have potential applications outside of
ground-water vulnerability mapping. These include the Public Land Survey
System (PLSS) digitized from BLM maps, Surficial Geology interpreted from
aerial photos, Bedrock Geology scanned from a previously published map,
Underground Injection Control (UIC) wells based on state permits, and
Permitted Ground Water Wells based on State Engineer's Office (SEO) well
permit database. All of these layers are available to download through
WyGISC's
data clearinghouse.
In an effort to disseminate the information produced through this project,
WYGISC is planning a
series of Ground Water Vulnerability Workshops to be conducted throughout the winter at
Wyoming's regional community colleges. For further information about the project or the upcoming
workshops contact Chris Arneson, WYGISC at (307) 766-2735 or Kevin Frederick, DEQ/WQD at
(307) 777-5985. Email questions can be sent to Chris Arneson or Jeff Hamerlinck.
CDs products by county Handbook and Maps Digital Data Procedure
Wyoming's sensitivity model requires six direct data layers which are then independently
rated and overlaid. These layers and their sources were Depth to Initial Ground Water based on
well permits, Net Aquifer Recharge estimated from soils and precipitation, Geohydrologic Settings
determined from geology, Soils, Land Surface Slope based on USGS DEMs, and Vadose Zone
Characteristics interpreted from geology and water levels. This overlay process created a relative
cumulative relative sensitivity map with ratings ranging from 6 (blue) to 60 (red). To create the vulnerability to
agricultural chemicals product, a seventh layer of Agricultural Land Use, interpreted from infrared
aerial photos, is added to create a Vulnerability rating range of 7 to 70.
Products
Currently these maps are being used in numerous planning and management projects. Some
examples include creating the Wyoming Statewide Pesticide Management Plan, Wellhead Protection
efforts in Goshen County, Quaternary Geology mapping for Wyoming, the Intermountain
Conservation District's Land Use Plan, the Wyoming/Nebraska North Platte Litigation, a BLM
pipeline EIS, a Cumulative Hydrologic Impact Assessment (CHIA) to mining activities in the Powder
River Basin, and USGS ground water monitoring efforts. USGS has used the maps directly to identify potential wells for pesticide sampling
within several counties of the state. For more information on this
program visit their web site, at http://wy.water.usgs.gov/projects/pests/pesticides.html.
