Wyoming Geohydrologic Setting Sensitivity Ratings at 1:500,000-Scale

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

Title:

Wyoming Geohydrologic Setting Sensitivity Ratings at 1:500,000-Scale

Abstract:

This dataset represents an aquifer sensitivity rating for the Geohydrologic Settings in the State of Wyoming. This dataset is specifically to be used within a DRASTIC-type aquifer sensitivity/vulnerability analysis.

1. How should this data set be cited?

   Wyoming Water Resources Center, 199702, Wyoming Geohydrologic Setting Sensitivity Ratings at 1:500,000-Scale: Wyoming Water Resources Center, Laramie, Wyoming.

   Online Links:

   • <URL:http://www.sdvc.uwyo.edu/clearinghouse/water.html>

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -111.04531329

   East_Bounding_Coordinate: -103.84002217

   North_Bounding_Coordinate: 44.99712629

   South_Bounding_Coordinate: 40.94825784

3. What does it look like?

   <URL:http://www.sdvc.uwyo.edu/images/dtw.gif>dtw.gif (gif)

   geohydrologic setting ratings in Wyoming

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: unknown

   Ending_Date: present

   Currentness_Reference: Publication date of sources

5. What is the general form of this data set?

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • GT-polygon composed of chains

   2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest .001. Longitudes are given to the nearest .001. Latitude and longitude values are specified in Decimal Degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is GRS1980.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.98.
      

7. How does the data set describe geographic features?

   Entity_and_Attribute_Overview:

   The lone attribute within this layer is called RATING containing an integer value between 1 and 10. This value is the sensitivity rating for the unit with 10 being the highest possible value.

   Entity_and_Attribute_Detail_Citation: n/a

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Wyoming Water Resources Center

2. Who also contributed to the data set?

3. To whom should users address questions about the data?

   SDVC Technical Coordinator
   Spatial Data and Visualization Center
   Box 4008 University Station
   Laramie, Wyoming 82071
   USA
   

   307-766-2532 (voice)
   itasca@uwyo.edu
   

   Hours_of_Service: 8 AM to 5 PM MST

This layer was developed specifically to serve as a parameter in a ground-water vulnerability to surface contamination study conducted at the Wyoming Water Resources Center. The DRASTIC-based model requires geohydrologic setting rating as one of its parameters. No other suitable uses for this data are known.

1. From what previous works were the data drawn?

   Digital Geologic Map of Wyoming in ARC/INFO Format (source 1 of 3)

   Green, G.N. and P.H. Drouillard, 1994, Digital Geologic Map of Wyoming in ARC/INFO Format.

   Type_of_Source_Media: digital map

   Source_Contribution: source of majority of boundaries used in attributes

   Surficial Geology map (source 2 of 3)

   Case, J.C., Arneson, C.S., and Hallberg, L., 1998, Preliminary 1:500,000-Scale Digital Surficial Geology Map of Wyoming.

   Type_of_Source_Media: digital map

   Source_Contribution: source of majority of boundaries used in attributes

   Geologic Map of Wyoming (source 3 of 3)

   Love, J.D. and A.C. Christiansen, 1985, Geologic Map of Wyoming.

   Type_of_Source_Media: paper map

   Source_Contribution: was source for Green and Drouillard (1994) map

2. How were the data generated, processed, and modified?

   (process 1 of 1)

   Geohydrologic Setting represents the aquifer characteristics of the uppermost aquifer. This comprehensive layer replaces both the Aquifer Media and the Saturated Hydraulic Conductivity layers that are used within the standard DRASTIC methodology. For purposes of the DRASTIC project, there was no single comprehensive analysis on the generalized hydrologic characteristics of the geological formations present in Wyoming. There were, however, a number of studies that addressed the hydrology of specific basins or regions within the state. The first step in analyzing the geohydrologic settings for all areas in Wyoming was to determine the generalized hydrologic characteristics for each geological formation present in the state by summarizing the formation-specific hydrologic characteristics published in the Water Resources Research Institute Basin Ground Water Report Series . The Water Resources Research Institute (which became the Wyoming Water Resources Center) reports provided overviews on the occurrence and characteristics of ground water in most basins in Wyoming. The project used the USGS Hydrologic Investigations Atlases to provide ground water reconnaissance for most of the state and selected USGS Water Supply Papers for information on ground water resources and geology for specific areas of the state. Using the above references for guidance, the Wyoming State Geological Survey developed a classification scheme to rank all geological formations in Wyoming by generalized hydrologic characteristics. In cases where the hydrologic characteristics were not described in the literature, the characteristics were estimated, based upon the dominant lithology of the formation. The classification scheme is as follows: 1. Aquiclude/aquitard - low to no yield 2. Aquitard with aquifer interbeds - low yield 3. Aquitard with aquifer interbeds, secondary permeability - low to moderate yield 4. Aquifer and aquitard mixed - moderate to low yield 5. Aquifer with aquitard interbeds - moderate yield 6. Aquifer with aquitard interbeds, secondary permeability - moderate to high yield 7. Aquifer - high to moderate yield 8. Aquifer - high yield The Stratigraphic Chart Showing Phanerozoic Nomenclature for the State of Wyoming (Love, Christiansen, and Ver Ploeg 1993) was used as the basis for the geological formations that were classified. Geological formations were classified within specific geographic regions of the state. Generalized hydrologic classifications assigned to the formations range from a high-yield aquifer to an aquiclude/aquitard with low to no yield. For the purposes of this study, the following definitions of yield were used: High Yield: May provide water supply for irrigation or water supplies for large communities in Wyoming. In general, such formations yield over 100 gallons per minute and may yield thousands of gallons per minute. Moderate Yield: May provide water supply for small communities or for light industrial needs. In general, such formations may yield approximately 30 gallons per minute. Low Yield: May provide a limited water supply for stock or domestic use. In general, such formations may yield up to 5 gallons per minute. The values for yield are approximate, and in localized areas any geological formation may produce significantly more or less water than indicated by the classification. The classification represents average characteristics for a formation over an entire basin. One of the key elements of the Ground Water Vulnerability Mapping Project is the final aquifer sensitivity analysis, which synthesizes data from multiple sources. The project used the 1:500,000-scale Geologic Map of Wyoming (Love and Christiansen 1985) as one of the base layers for the sensitivity assessment. The aerial extent of many geological formations are too small to be shown at a scale of 1:500,000, and some formations with similar ages but dissimilar hydrologic characteristics have been combined on the Geologic Map of Wyoming. As a result, in order to delineate geohydrologic settings many of the formations that were individually classified in regards to their hydrologic characteristics, have been combined with other formations with similar hydrogeologic characteristics, and the combination then reclassified using the scheme presented above. Individual formations may have different classifications based on what area of the state it occurs. DRASTIC (Aller et al 1987) defined a sensitivity rating for saturated aquifer media in large part based upon inferred hydrologic, geologic, and lithologic characteristics for various rock and material types. It ranged from 1 to 10, with 1 representing unfractured massive shale with a low pollution potential and 10 representing well-developed karst limestone with a high pollution potential. Because the Wyoming method uses a more comprehensive Geohydrologic Setting layer instead of individual Aquifer Media and Hydraulic Conductivity layers, the DRASTIC classification was modified to include hydraulic conductivity values from Freeze and Cherry (1979). Relative rankings from the Wyoming model were compared to the relative rankings from the eight-step aquifer characteristics model, presented above. One of the limitations of the DRASTIC model is that sensitivity rankings are largely based upon rock type, lithology, and inferred hydrologic characteristics. The comparison allowed the DRASTIC ranking to be adjusted to reflect the actual hydrologic characteristics of the geological formation or material. Process_Date 1996

3. What similar or related data should the user be aware of?

1. How well have the observations been checked?

   see Process Steps

2. How accurate are the geographic locations?

   see Process Steps

3. How accurate are the heights or depths?

4. Where are the gaps in the data? What is missing?

   All polygons are fully attributed.

5. How consistent are the relationships among the observations, including topology?

   All polygons are closed and each polygon has one unique label.

Are there legal restrictions on access or use of the data?

Access_Constraints: none

Use_Constraints:

This data should not be used for analysis at a scale larger than 1:100,000. Because updates to this dataset or the attached metadata will occur without notice, this dataset may not be redistributed or repackaged in any form without the express written consent of the University of Wyoming Spatial Data and Visualization Center. Instead it is recommended that additional users download the most current version of the data from <http://www.sdvc.uwyo.edu/clearinghouse>.

1. Who distributes the data set? (Distributor 1 of 1)

   SDVC Technical Coordinator
   Spatial Data and Visualization Center
   Box 4008 University Station
   Laramie, Wyoming 82071
   USA
   

   307-766-2532 (voice)
   n/a
   

2. What's the catalog number I need to order this data set?

3. What legal disclaimers am I supposed to read?

   The distributor shall not be held liable for improper or incorrect use of this data, based on the description of appropriate/inappropriate used described in this metadata document. It is strongly recommended that this data is directly acquired from the distributor described above and not indirectly through other sources which may have changed the data in some way. See the Use_Constraints section of this metadata for appropriate uses/limiations of the data. The distributor makes no claims for the data's suitability for other purposes.

4. How can I download or order the data?
   • Availability in digital form:

     Data format:	ARCE (Arc/Info export) (version 7.0.4) Size: 8.9
     Network links:	ftp.sdvc.uwyo.edu or <http://www.sdvc.uwyo.edu/clearinghouse>

   • Cost to order the data:

Dates:

Last modified: 16-Jun-1997

Metadata author:

Margo Berendsen
Box 3067 University Station
Laramie, Wyoming 82071
USA

307-766-2735 (voice)
meh@uwyo.edu

Metadata standard:

FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)