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Data Collected for the Source Water Assessment
One of the challenges facing the source water assessment
team was the determination and collection of the GIS data required for
the project. All of the GIS data collected for the project were converted
into seamless, statewide coverages for ease of map production and analysis
within the GIS software. The only exception to this method was the Digital
Elevation Model (DEM). The DEM coverage for the state was roughly divided
into quarters to allow for faster processing. The GIS data considered
pertinent to the source water susceptibility methodology include:
Land Use/Land Cover (LULC)
FGDC Metadata
Source: Arkansas GAP
Analysis Project
Data Format:
Raster (30m resolution)
Scale:
1:100,000
Source Agency:
Center for Advanced Spatial Technologies (CAST)
Description:
The Arkansas GAP Analysis project was completed in 1996 by the Center
for Advanced Spatial Technologies. The result of this project was a
Statewide, LANDSAT image classification of the land cover and vegetation
classes found within Arkansas. These data represent the most current
and complete land use characteristics for the study area. Therefore,
the resulting land cover classification was re-classed into the appropriate
land cover classes for the source water assessment.
Soils
FGDC
Metadata
Source:
STATSGO; modified by CAST
Data Format:
Raster (30m resolution)
Scale:
1:250,000
Source Agency:
NRCS (Fort Worth, TX); CAST
Description:
The Arkansas STATSGO General Soil map contains 71 soil map units. Each
of these general map units are comprised of approximately 21 categories
and 7 layers that further describe the soils that make up the entire
unit. Those categories and layers were averaged for each soil unit in
order to obtain a single value for the assessment of Soil Permeability
and Depth-to-Bedrock, which were required attributes for the Source
Water Assessment.
Elevation
FGDC Metadata
Source:
USGS Digital Elevation Model (DEM)
Data Format:
Raster (30m resolution)
Scale:
1:24,000
Source Agency:
United States Geological Survey (Little Rock, AR)
Description:
The United States Geological Survey in Little Rock were responsible
for obtaining all of the most current 7.5' minute Digital Elevation
Models (DEM) for the study area and patching them together with ArcInfo
(GRID). In those areas where a 7.5-minute DEM quadrangle had not been
completed for Arkansas, the 80m data from the NIMA organization were
used and then re-sampled to 30m resolution to match the rest of the
dataset. The project participants agreed that these were the best data
available at the time of the project.
Slope
FGDC
Metadata
Source: Calculated
from the DEM in percent slope
Data Format:
Raster (30m resolution)
Scale: 1:24,000
Source Agency:
United States Geological Survey (Little Rock, AR)
Description:
The slope map was derived from the DEM data generated for the study
area. The slope ranges are in percent slope and were determined by the
source water assessment team. The ranges of percent slope are: ( 0-5%,
6-10%, 11-15%, 15-20%, > 20%, and No Data).
Geology
FGDC
Metadata
Source:
USGS Geologic Map of Arkansas; digitized by CAST
Data Format:
Raster (30m resolution)
Scale:
1:100,000
Source Agency:
USGS; CAST
Description:
The General Geology map of Arkansas was originally compiled in 1977
by the USGS and was digitized into a GIS coverage in 1989. These data
remain the only digital version of Arkansas' general geology to date.
The geologic categories were reclassified into source water assessment
"weighting factors" for each rock type in Arkansas. Dr. Ralph Davis
of the Arkansas Water Resources Center determined these category reclassifications.
Landforms
FGDC Metadata
Source:
STATSGO; modified by Arkansas Department of Health
Data Format: Vector
Scale:
1:250,000
Source Agency:
NRCS (Fort Worth, TX); Arkansas Dept. of Health
Description:
The Arkansas Department of Health - Engineering Section, contributed
the Arkansas landform data. Lyle Godfrey and Ralph Davis were responsible
for edits made to this dataset to reflect their collective, professional
opinion of the general landform regions of Arkansas. The source of the
original data was the STATSGO general soil map of Arkansas that had
been manipulated by the Natural Resource Conservation Service in Little
Rock, Arkansas.
Roads
FGDC
Metadata
Source:
USGS 7.5minute quad maps; modified/updated by AHTD
Data Format:
Vector
Scale:
1:24,000
Source Agency:
USGS, Ark. Highway and Transportation Dept.
Description:
These data were obtained from the Arkansas Highway and Transportation
Department (AHTD) for use during the Arkansas source water assessment
project. These data were originally digitized from USGS quadrangle maps
and have since been updated and maintained by the AHTD cartographers
using current black and white photography. Although these data do not
contain address attribution or even street names, it was the most "spatially"
accurate, complete road coverage for the state of Arkansas at the beginning
of this study. The AHTD allowed the Arkansas Department of Health to
use these data, free of charge, via a memorandum of understanding.
Streams
FGDC Metadata
Source:
TIGER Line Files (1998)
Data Format:
Vector (lines)
Scale:
1:100,000
Source Agency: U.S.
Bureau of the Census
Description:
This data layer contains all of the 1998 TIGER/Line hydrographic lines
for the State of Arkansas. The file is an extract of the 1998 TIGER/Line
files. These data were originally collected from the USGS Digital Line
Graph data. After review by the source water team, it was determined
that these data better represented the nature of the hydrology within
Arkansas, than any other readily available data source; regardless of
the fact that the other reviewed data were collected at a more accurate
scale. The added bonus of the DLG data was the inclusion of segment
attribution. Although this attribution is not entirely accurate, a large
majority of the major streams and rivers are labeled correctly. Many
attribute errors exist in perennial streams and canal segments within
the Arkansas and Mississippi delta areas. (TIGER is a registered trademark
of the U.S. Census Bureau)
Lakes
FGDC Metadata
Source:
TIGER Line Files (1998)
Data Format:
Vector (polygons)
Scale:
1:100,000
Source Agency:
U.S. Bureau of the Census
Description:
This data layer contains all of the 1998 TIGER/Line hydrographic polygons
for the State of Arkansas. The file is an extract of the 1998 TIGER/Line
files. These data were originally collected from the USGS Digital Line
Graph (DLG) data. After review by the source water team, it was determined
that these data better represented the nature of the hydrology within
Arkansas, than any other readily available data source; regardless of
the fact that the other reviewed data were collected at a more accurate
scale. The DLG lake polygons contained the most accurate topological
structure and therefore made solid fills within the mapping process
much simpler.
Public Water System Intakes (PWS)
FGDC
Metadata
Source:
Determined in the field using GPS or USGS 7.5-minute quads
Data Format:
Vector (points)
Scale: 1:100,000
Source Agency:
Arkansas Department of Health
Description:
This data layer illustrates the locations of public water system (PWS)
intakes in the State of Arkansas. These locations have been mapped and/or
located by the Arkansas Department of Health-Engineering Section staff
under the guidance of Lyle Godfrey, using a variety of methods. The
PWS locations were mapped between the spring of 1995 until the summer
of 1999. The full metadata documentation contains a description of each
attribute that was collected for the PWS locations, but the most important
to note that these "systems" were classified by type by the Arkansas
Department of Health. These types consist of: Surface, Groundater, Spring,
and GroundWater Under the Direct Influence of surface water (GWUDI)
water source-type. The type of source used for each public water system
determined the method for assessment area delineation.
Assessment Areas for each Public Water
System Intake
FGDC
Metadata
Source: ADH
Wellhead Protection Program using various methods
Data Format:
Vector (polygons)
Scale: 1:100,000
Source Agency:
Arkansas Department of Health (ADH), United States Geological Survey
Description: Wells:
Well delineation methods are those approved for the Arkansas Well Head
Protection Program.
Springs and GWUDI wells: An assessment area was
delineated around each spring enclosure or wellhead using the arbitrary
fixed radius method of delineation to set the boundary at a radial distance
of 0.5 mile around each intake. If a surface water body intersected
the base 0.5-mile radius, conjunctive delineations were performed. In
such cases the delineation and assessment area was increased to include
all area within a radius of 3.0 miles of the intake.
Rivers, Streams and Impoundments: The entire
watershed of the drinking water source within the state boundary was
delineated. For Rivers / Streams, Assessment Areas included all lands
within 0.25 miles of either side of the centerline of the river / stream
and of all its tributaries within a 3 day time of travel limited by
a maximum distance upstream from the intake of 20 miles.
For Impoundments, Assessment Areas included all
lands within a 5-mile radius around the intake that are within 0.25
miles of the shoreline at the impoundment's high water level and within
0.25 miles of either side of the centerline of all tributaries. In addition,
all lands within a 0.5-mile radius of the intake, regardless of watershed
boundaries are included.
County/State boundaries
FGDC Metadata
Source: TIGER
Line Files (1998); modified by CAST
Data Format: Vector
(lines)
Scale: 1:100,000
Source Agency:
U.S. Bureau of the Census; CAST
Description:
The file contains the 1998 TIGER/Line county boundaries for the State
of Arkansas. The file is an extract of the 1998 TIGER/Line files. TIGER,
TIGER/Line, and Census TIGER are registered trademarks of the Bureau
of the Census. The geographic coverage for a single TIGER/Line file
is a county with the coverage area based on January 1, 1998 legal boundaries.
The subject file was created using the GIS Tools software product "tgr2shp"
to convert the individual county TIGER/Line files to the shapefile format.
Using the ESRI software product ArcView 3.2 the individual county files
were merged into one file covering the State of Arkansas for database
population and subsequent use by the general public.
Railroads
FGDC Metadata
Source:
TIGER/Line files (1998); modified by CAST
Data Format:
Vector
Scale:
1:100,000
Source Agency:
U.S. Bureau of the Census; CAST
Description:
The file contains all of the 1998 TIGER/Line railroad links for the
State of Arkansas. The file is an extract of the 1998 TIGER/Line files.
TIGER, TIGER/Line, and Census TIGER are registered trademarks of the
Bureau of the Census. The geographic coverage for a single TIGER/Line
file is a county with the coverage area based on January 1, 1998 legal
boundaries. The subject file was created using the GIS Tools software
product "tgr2shp" to convert the individual county TIGER/Line files
to "shp" format. Using the ESRI software product ArcView 3.2 the individual
county files were merged into one file covering the State of Arkansas
for database population and subsequent use for the source water assessment.
Precipitation
FGDC
Metadata
Source:
PRISM; modified by CAST
Data Format: Vector
Scale:
1:100,000
Source Agency:
Oregon State Univ., Oregon Climate Service and CAST
Description:
This data layer illustrates average annual precipitation in the State
of Arkansas for the climatological period 1961-1990. Parameter-elevation
Regressions on Independent Slopes Model (PRISM) derived raster data
is the underlying data set from which the polygons were created. PRISM
is an anlytical model that uses point data and a digital elevation model
(DEM) to generate grid estimates of annual, monthly and event-based
climatic parameters. Further information on PRISM can be found at: http://www.ocs.orst.edu/prism/prism_new.html
Potential Sources of Contamination (PSOC)
FGDC Metadata
Source:
Varies
(Click to see table), geocoded/compiled by CAST
Data Format: Vector
(points)
Scale:
1:100,000
Source Agency: Various
Agencies (Click to see table), CAST
Description:
The identification of potential sources of contamination (PSOC) and
the where or how to obtain these data was another challenge. A PSOC
was defined as; "a contaminant that has the potential to adversely affect
the quality of a drinking water supply". An initial list of contaminants
was obtained from the Environmental Protection Agency (EPA) web site:
· http://www.epa.gov/OGWDW/swp/vcontam3.html
· http://www.epa.gov/OGWDW/swp/sources1.html
The Source Water Assessment Team agreed to refine
the EPA lists of potential contaminants to fit the conditions found
within Arkansas. These PSOCs were assigned a "table
code" that indicated the source of the information so that
each point location could be merged into one seamless map layer of PSOCs
for assessment purposes. These "table codes" ensured that each point
would not only have a unique number, but that it could be traced back
to the data source. A complete list, including the contact information
for organizations that contributed data during the project, is contained
in the Appendix of this document.
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