Vulnerability assessment of twelve major aquifers in Oklahoma

              LL
Funding for this investigation was partially provided by the U.S. Environmental Protection
Agency under the FY95 104(b) (3) program. Any use of trade names in this publication is for
descriptive purposes and does not imply endorsement by the State of Oklahoma or U.S.
Government.
This publication is prepared, issued and printed by the Oklahoma Water Resources Board. Five
hundred copies were prepared at a cost of $3,825. Copies have been deposited with the
Publications Clearinghouse at the Oklahoma Department of Libraries.
LLL
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Selected Aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Aquifer Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Vulnerability Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Vulnerability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
DRASTIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Hydrogeologic Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Map Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Appendix A: Drastic Ranges and Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1
Appendix B: Vulnerability Maps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1
1
Introduction
PURPOSE
The purpose of this investigation was to provide information on 12 major aquifers in Oklahoma
that will enable the state to incorporate groundwater protection for whole-basin planning.
The DRASTIC model was used to compute the relative vulnerability of groundwater to
contamination from surface sources of pollution. A series of easy-to-understand color maps was
produced, which can be used to provide assistance in resource allocation and prioritization of
groundwater-related activities.
PARTICIPANTS
This study was prepared under a cooperative agreement with the Oklahoma Office of the
Secretary of Environment (OSE) and funded by the U.S. Environmental Protection Agency
(EPA). The U.S. Geological Survey (USGS) created, documented, and published digital
geospatial data sets that describe the aquifer characteristics and created the grid layers used to
calculate the DRASTIC index. The Oklahoma Water Resources Board (OWRB) computed the
final DRASTIC indices and produced the aquifer vulnerability maps.
Aquifers
BACKGROUND
Groundwater is water that has percolated downward from the surface, filling voids or open
spaces in the rock formations. More than 60 percent of the total water use in Oklahoma,
including almost 90 percent of the state’s irrigation needs, is from groundwater. Groundwater
provides municipal water for more than 300 Oklahoma cities and towns.
An aquifer is a subsurface unit that can yield useful quantities of water. Oklahoma’s aquifers
may be divided into two general groups: bedrock and alluvium and terrace aquifers. The
bedrock aquifers include sandstone aquifers, soluble carbonate and evaporite (limestone,
dolomite, and gypsum) aquifers, and the semi-consolidated sand and gravel underlying the High
Plains. The alluvium and terrace aquifers consist of unconsolidated deposits of sand and gravel
along rivers and streams.
The OWRB considers major aquifers, or groundwater basins, to be those bedrock aquifers that
can yield on average at least 50 gallons per minute (gpm), and those alluvium and terrace
aquifers that can yield at least 100 gpm. Minor aquifers yield less water. Oklahoma is underlain
by 23 major aquifers containing an estimated 320 million acre-feet of water in storage. Many
minor aquifers also yield significant amounts of fresh water.
SELECTED AQUIFERS
Twelve major aquifers, for which adequate data were available from previous studies, were
selected for the study.
2
The twelve aquifers included in this study are listed below and are displayed in Figure 1:
Bedrock Aquifers:
Central Oklahoma
Vamoosa-Ada
Rush Springs
Antlers
Elk City
High Plains
Alluvium and Terrace Aquifers:
Enid Isolated Terrace
Tillman Terrace
Cimarron River
North Canadian River:
------ western reach from the Panhandle to Canton Lake
------ central reach from Canton Lake to Lake Overholser
------ eastern reach from Oklahoma City to Eufaula Lake
The vulnerability was calculated on the surficial, or outcrop, portion of the aquifers. Portions of
some bedrock aquifers (Central Oklahoma, Rush Springs, and Antlers) are overlain by less
permeable rock and were not included in the final vulnerability determination.
AQUIFER DESCRIPTIONS
The Central Oklahoma aquifer consists of the Permian-age Garber Sandstone, Wellington
Formation, and the Chase, Council Grove, and Admire Groups. The Pennsylvanian-age
Vamoosa Formation and Ada Group comprise the Vamoosa-Ada aquifer. Both aquifers are in
central Oklahoma and consist of fine-grained sandstone interbedded with shale and siltstone.
The Rush Springs aquifer, in western Oklahoma, consists of the Permian-age Rush Springs
Sandstone, parts of the Permian-age Marlow Formation, and alluvial and terrace deposits. The
Rush Springs Sandstone consists of fine-grained sandstone with some interbedded gypsum and
dolomite. Wells from these aquifers commonly yield 25 to 400 gpm.
The Cretaceous-age Antlers aquifer, in southeastern Oklahoma, consists of poorly- cemented,
fine-grained sand and sandstone with some layers of shale, limestone, conglomerate, and clay.
Wells commonly yield 10 to 50 gpm, but can yield as much as 400 gpm. The Elk City aquifer, in
southwestern Oklahoma, consists of the Elk City Sandstone and overlying terrace deposits, dune
sands, and gravel of the Ogallala Formation. The Permian-age Elk City Sandstone is composed
of friable sandstone with minor amounts of silt and clay. Wells in the Elk City aquifer yield 25-
300 gpm.
The High Plains aquifer, in western Oklahoma and the Panhandle, consists of the Tertiary-age
Ogallala Formation, overlying Quaternary-age alluvial and terrace deposits, and some Triassic,
Vamoosa-Ada
Tillman
High Plains
Rush Springs
Central Oklahoma
North Canadian (Central)
North Canadian (East)
North Canadian (West)
Enid
Elk City
Cimarron
Antlers
County
N
30 0 30 60 90 120 150 180 Miles
Figure 1. Map showing the twelve major aquifers in Oklahoma that are included in the vulnerability assessment
4
Jurassic, and Cretaceous-age rocks that are exposed at the surface. The Ogallala Formation is
composed of semi-consolidated layers of sand, silt, clay, and gravel. Wells commonly yield 25
to 1,500 gpm. The depth to water in the High Plains is much deeper than in the other aquifers in
this study, with depths generally greater than 100 feet.
The alluvium and terrace aquifers are Quaternary in age, and occur along modern and ancient
streams throughout the state. They consist of unconsolidated deposits of sand, silt, clay, and
gravel. The alluvium and terrace aquifers typically have shallow water depths and are very
permeable. Yields of wells in these aquifers range from 10 to 1,200 gpm.
Vulnerability Assessment
VULNERABILITY
As used in this report, vulnerability refers to the sensitivity of groundwater to contamination, and
is determined by intrinsic characteristics of the aquifer. It is distinct from pollution risk, which
depends not only on vulnerability but also on the existence of significant pollutant loading. The
seriousness of the impact on water use will depend on the magnitude of the pollution episode and
the value of the groundwater resource.
DRASTIC
DRASTIC was developed by the EPA to be a standardized system for evaluating groundwater
vulnerability to pollution. The primary purpose of DRASTIC is to provide assistance in resource
allocation and prioritization of many types of groundwater-related activities and to provide a
practical educational tool. DRASTIC can be used to set priorities for areas to conduct
groundwater monitoring. For example, a denser monitoring system might be installed in areas
where aquifer vulnerability is higher and land use suggests a potential source of pollution.
DRASTIC can also be used with other information (such as land use, potential sources of
contamination, and beneficial uses of the aquifer) to identify areas where special attention or
protection efforts are warranted.
The model has four assumptions:
1. the contaminant is introduced at the ground surface;
2. the contaminant is flushed into the groundwater by precipitation;
3. the contaminant has the mobility of water;
4. the area being evaluated by DRASTIC is 100 acres or larger.
DRASTIC was not designed to deal with pollutants introduced in the shallow or deep subsurface,
by methods such as leaking underground storage tanks, animal waste lagoons, or injection wells.
The methodology is not designed to replace on-site investigations or to site any type of facility or
practice. For example, DRASTIC does not reflect the suitability of a site for waste disposal.
Although DRASTIC may be one of many criteria used in siting decisions, it should not be the
sole criterion.
5
DRASTIC considers seven hydrogeologic factors:
1. Depth to water
2. net Recharge
3. Aquifer media
4. Soil media
5. Topography (slope)
6. Impact of the vadose zone media
7. hydraulic Conductivity of the aquifer
Each of the hydrogeologic factors is assigned a rating from one to 10 based on a range of values.
The ratings are then multiplied by a relative weight ranging from one to five (Table 1). The most
significant factors have a weight of five; the least significant have a weight of one. The ranges
and ratings for each hydrogeologic factor are listed in Appendix A.
Table 1. Assigned weights for DRASTIC hydrogeologic factors
Hydrogeologic Factor Weight
D- Depth to Water 5
R - Net Recharge 4
A - Aquifer Media 3
S - Soil Media 2
T - Topography 1
I - Impact of the Vadose Zone Media 5
C - Aquifer Hydraulic Conductivity 3
The equation for determining the DRASTIC index is:
D D + R R + A A + S S + T T + I I + C C = DRASTIC Index r w r w r w r w r w r w r w
where D, R, A, S, T, I, C represent the seven hydrogeologic factors, r designates the rating, and w
the weight. An example DRASTIC calculation is shown in Table 2. The smallest possible
DRASTIC index rating is 23 and the largest is 226.
The resulting DRASTIC index represents a relative measure of groundwater vulnerability. The
higher the DRASTIC index, the greater the vulnerability of the aquifer to contamination. A site
with a low DRASTIC index is not free from groundwater contamination, but it is less susceptible
to contamination compared with the sites with high DRASTIC indices.
The method used in this study is called DRASTIC. Another DRASTIC method, called Pesticide
DRASTIC, is designed to be used in areas where the activity of concern is the application of
pesticides. Pesticide DRASTIC differs from DRASTIC in the assignment of relative weights for
6
Table 2. Example of a DRASTIC index calculation
Factor 5DWLQJ  Weight Number
D 7 * 5 = 35
R 1 * 4 = 4
A 8 * 3 = 24
S 5 * 2 = 10
T 9 * 1 = 9
I 8 * 5 = 40
C 2 * 3 = 6
DRASTIC Index 128
the seven hydrogeologic factors. If the user is concerned with groundwater vulnerability to
pesticides, then Pesticide DRASTIC should be used.
For a complete discussion of the DRASTIC method, refer to the EPA publication DRASTIC: A
Standardized System for Evaluating Ground Water Pollution Potential Using Hydrogeologic
Settings by Aller and others, 1987.
METHODOLOGY
The ARC/INFO Geographic Information System (GIS) was used to compile the geospatial data,
to compute the DRASTIC indices, and to generate the final vulnerability maps (ESRI, 1997).
The USGS created digital geospatial data sets that describe aquifer characteristics of the 12
aquifers (Abbott and others, 1997a,b; Adams and others, 1997; Becker and others, 1997a,b,c,d;
Runkle and Rea, 1997a,b). Included in the data sets are the aquifer boundaries, hydraulic
conductivity, recharge, and water-level elevations. The data sets are available in nonproprietary
and ARC/INFO formats on the Internet at: http://wwwok.cr.usgs.gov/gis/aquifers/index.html.
The USGS also created digital surficial geology sets from the hydrologic atlases of Oklahoma
(Cederstrand, 1996a,b,c,d,e,f,g,h,i,j,k,l). The surficial geology data sets are available on the
Internet at http://wwwok.cr.usgs.gov/gis/geology/index.html.
The USGS then overlaid a model grid over the aquifers, and assigned DRASTIC ratings to the
grid cells for each of the seven hydrogeologic factors. The cell size is 960 x 960 meters, which is
about 228 acres.
The OWRB used the grid layers created by the USGS to compute the final DRASTIC indices and
to produce the aquifer vulnerability maps. The OWRB created an aquifer zone grid to group grid
cells by aquifer for the statistical analysis.
7
HYDROGEOLOGIC FACTORS
The hydrogeologic factors are described below:
Depth to Water (D): The depth to water is the distance, in feet, from the ground surface to the
water table. It determines the depth of material through which a contaminant must travel before
reaching the aquifer. Thus, the shallower the water depth, the more vulnerable the aquifer is to
pollution.
The grid layers for depth to water were generated by computer subtraction of water-level
elevation data sets from land surface elevation. Land surface elevations were derived from a
digital elevation model (DEM) for Oklahoma from 1:100,000-scale maps (Cederstrand and Rea,
1996). The water-level elevation data sets were developed from maps published in aquifer
reports. Depth to water ranged from less than 5 feet in some alluvium and terrace aquifers to
greater than 100 feet in the High Plains aquifer.
Net Recharge (R): The primary source of recharge is precipitation, which infiltrates through the
ground surface and percolates to the water table. Net recharge is the total quantity of water per
unit area, in inches per year, which reaches the water table. Recharge is the principal vehicle for
leaching and transporting contaminants to the water table. The more the recharge, the greater the
chance for contaminants to reach the water table.
The grid layers for net recharge were developed from the recharge data sets. Recharge rates for
the aquifers were usually derived from groundwater flow models and represent averages over
large areas. All of the values in this study were in the ranges of 0-2 or 2-4 inches per year.
Aquifer Media (A): Aquifer media refers to the consolidated or unconsolidated rock that serves
as an aquifer. The larger the grain size and the more fractures or openings within the aquifer, the
higher the permeability, and thus vulnerability, of the aquifer. In unconsolidated aquifers, the
rating is based on the sorting and amount of fine material within the aquifer. In consolidated
aquifers, the rating is based on the amount of primary porosity and secondary porosity along
fractures and bedding planes.
Information on aquifer media was obtained from the aquifer studies and the hydrologic atlases of
Oklahoma. The grid layers for aquifer media consist of one number for each aquifer. Ratings for
the aquifers in this study range from six for the Vamoosa-Ada and Central Oklahoma aquifers, to
eight for the High Plains and the alluvium and terrace aquifers.
Soil Media (S): Soil media is the upper weathered zone of the earth, which averages a depth of
six feet or less from the ground surface. Soil has a significant impact on the amount of recharge
that can infiltrate into the ground. In general, the less the clay shrinks and swells and the smaller
the grain size of the soil, the less likely contaminants will reach the water table.
The general soil associations for an area were determined from soil survey maps. The soil
horizons were then evaluated to determine which will most significantly affect groundwater
vulnerability, based on texture and thickness of each layer. The USGS used the U.S. Department
8
of Agriculture’s State Soil geographic Database (STATSGO) to develop the grid layers for soil.
Soils in this study varied greatly from clay to sand.
Topography (T): Topography refers to the slope of the land surface. Topography helps control
the likelihood that a pollutant will run off or remain long enough to infiltrate through the ground
surface. Where slopes are low, there is little runoff, and the potential for pollution is greater.
Conversely, where slopes are steep, runoff capacity is high and the potential for pollution to
groundwater is lower. The USGS used a digital elevation model (DEM) to calculate percent
slopes. Most of the slopes in this study were in the ranges of 0-2 and 2-6 percent.
Impact of the Vadose Zone Media (I): The vadose zone is the unsaturated zone above the water
table. The texture of the vadose zone determines the time of travel of the contaminant through it.
In surficial aquifers, the ratings for the vadose zone are generally the same as the aquifer media.
Sometimes a lower rating is assigned if the aquifer media is overlain by a less permeable layer
such as clay.
As in the aquifer media (A) factor, this information was obtained from the aquifer studies and the
hydrologic atlases of Oklahoma. The grid layers for vadose zone media consist of one number
for each aquifer.
Hydraulic Conductivity of the Aquifer (C): Hydraulic conductivity refers to the rate at which
water flows horizontally through an aquifer. The higher the conductivity, the more vulnerable
the aquifer.
Conductivity values for the aquifers were usually derived from groundwater flow models and
represent averages over large areas. Most of the bedrock aquifers in this study have hydraulic
conductivity values in the range of 10-100 gpd/ft2. The alluvium and terrace aquifers have higher
hydraulic conductivity values, ranging from 100 to greater than 2,000 gpd/ft2.
Results and Discussion
RESULTS
The vulnerability maps are displayed in Appendix B. Standard DRASTIC colors were used for
the maps. These standard colors range from purple for the least vulnerable to yellow for the most
vulnerable. The large state-wide map is useful for comparing the relative vulnerability of the 12
aquifers. Ten smaller maps display the DRASTIC results by aquifer. These are useful in
viewing smaller areas within an aquifer.
A statistical summary of the DRASTIC indices, by aquifer, is listed is Table 3. The mean
DRASTIC indices range from 96 (least vulnerable) for the Central Oklahoma aquifer to 156
(most vulnerable) for the eastern reach of the North Canadian Alluvium and Terrace aquifer.
Table 4 lists the mean DRASTIC numbers, by aquifer, for each of the hydrogeologic factors.
9
Aquifer DRASTIC Index D R A S T I C
Central Oklahoma 95.8 25.6 4.0 18.0 6.1 9.1 30.0 3.0
Vamoosa-Ada 95.9 26.1 4.0 18.0 6.1 8.6 30.0 3.0
Rush Springs 98.5 23.8 4.2 21.0 7.4 9.1 30.0 3.0
High Plains 104.0 11.6 4.0 24.0 9.0 9.6 40.0 5.7
Antlers 110.9 35.8 4.0 21.0 7.7 9.4 30.0 3.0
Elk City 129.1 36.8 12.0 21.0 9.7 9.7 35.0 4.8
N. Canadian River (West) 133.5 29.3 4.0 24.0 16.1 9.9 40.0 10.3
N. Canadian River (Central) 134.2 37.6 4.1 24.0 12.4 9.9 40.0 6.2
Tillman Isolated Terrace 142.2 34.6 12.0 24.0 9.6 10.0 40.0 12.0
Cimarron River 150.9 37.3 11.9 23.9 15.1 9.9 39.9 12.8
Enid Isolated Terrace 152.0 41.0 12.0 24.0 7.0 10.0 40.0 18.0
N. Canadian River (East) 155.5 30.2 12.0 24.0 9.6 9.5 40.0 30.0
Table 3. Summary statistics of the DRASTIC indices by aquifer
Aquifer Aquifer Minimum Maximum Mean Median Standard
Type Deviation
Bedrock
Central Oklahoma 75 133 96 95 13.31
Vamoosa-Ada 71 132 96 95 15.47
Rush Springs 74 136 98 98 13.53
High Plains 91 152 104 98 13.41
Antlers 70 136 111 114 15.03
Elk City 95 151 129 126 10.41
Alluvium
and
Terrace
N. Canadian River (west) 95 164 134 133 14.19
N. Canadian River (central) 107 177 134 137 10.93
Tillman Terrace 110 166 142 141 11.80
Cimarron River 81 172 151 151 13.07
Enid Isolated Terrace 131 166 152 151 7.65
N. Canadian River (east) 122 178 156 156 15.64
Table 4. Mean values for DRASTIC indices and hydrogeologic factors by aquifer
10
There is a correlation between the mean DRASTIC indices and the type of aquifer material. The
three bedrock aquifers that consist of sandstones with interbedded shales (Central Oklahoma,
Vamoosa-Ada, and Rush Springs) have low mean DRASTIC indices of less than 100. The
Antlers and Elk City aquifers, composed of loosely-cemented sandstones, have mean DRASTIC
indices of 111 and 129. All of the alluvium and terrace aquifers, composed of unconsolidated
sands and gravels, have mean indices above 130.
Because DRASTIC indices were calculated only for the areas where the aquifers outcrop, the
ratings for aquifer media (A) and the impact of the vadose zone media (I) factors are usually the
same. These factors have weights of five and three respectively, and together they have a strong
influence on the final DRASTIC index.
Depth to water (D) is also heavily weighted, with a weighting factor of five, and therefore has a
significant influence on the index. The Central Oklahoma, Vamoosa-Ada, and Rush Springs
Sandstone aquifers have the lowest ratings for depth to water, and the alluvium and terrace
aquifers have the highest ratings. The impact of water depth is most apparent in the High Plains
aquifer. Although the High Plains aquifer has a high DRASTIC rating for aquifer media (A) and
impact of the vadose zone media (I), similar to the alluvium and terrace deposits, its great depth
to water lowers its mean DRASTIC index.
MAP LIMITATIONS
The twelve aquifers included in this study represent only a portion of the groundwater in the
state. Several major and all of the minor aquifers were excluded. None of the carbonate or
evaporite aquifers, which are typically very vulnerable, were included in this investigation.
Therefore, caution should be used in making conclusions about which aquifers in the state are the
most or least vulnerable. Additional work is needed to produce hydrologic studies and
vulnerability maps of the other major and minor aquifers in Oklahoma.
The aquifer data used in these analyses were taken from various studies, which were conducted
by different authors. Values for some factors, such as recharge (R), were determined by different
methodologies. Thus, apparent differences in vulnerability may be due to differences in
methodology or interpretation.
Another limitation is the accuracy of the depth to water. The accuracy of depth to water is a
function of the contour interval of the water-level elevations. The larger the contour interval, the
less accurate were the depths to water.
These maps describe the relative vulnerability of the aquifers based on available data of different
levels of precision and resolution. Resolution depends on the number and proximity of data
points. For example, the grid layer for topography (T) was derived from a high resolution, 60-
meter DEM grid, while other layers, such as net recharge (R) and hydraulic conductivity (C),
were derived from groundwater flow models and represent averages over large areas. The mixed
resolution is acceptable for evaluating relative vulnerability of aquifers, but is not adequate to
determine site-specific vulnerability. No attempt has been made to calibrate the DRASTIC
results to field data.
11
Conclusions
The relative vulnerability of 12 major Oklahoma aquifers was determined using the EPA’s
DRASTIC method. Of the aquifers included in this investigation, the bedrock aquifers have the
lowest DRASTIC indices and are the least vulnerable to contamination from pollutants
introduced at the ground surface. The alluvium and terrace aquifers have the highest DRASTIC
indices and are the most vulnerable. The High Plains aquifer has a moderate DRASTIC index,
largely due to its great depth to water.
The vulnerability maps can assist in the implementation of groundwater management strategies
to prevent degradation of groundwater quality. The DRASTIC vulnerability maps are useful in
identifying areas where certain activities may pose a higher risk, but they do not replace the need
for site-specific investigations.
12
References
Abbott, M.M., Runkle, Donna, and Rea, Alan, 1997a, Digital Data Sets That Describe Aquifer
Characteristics of the Antlers Aquifer in Southeastern Oklahoma: U.S. Geological Survey
Open-File Report 96-443, based on a scale of 1:250,000, 1 diskette.
------1997b, Digital Data Sets That Describe Aquifer Characteristics of the Vamoosa-Ada
Aquifer in East-central Oklahoma: U.S. Geological Survey Open-File Report 96-444,
based on a scale of 1:250,000, 2 diskettes.
Adams, G.P., Runkle, Donna, and Rea, Alan, 1997a, Digital Data Sets That Describe Aquifer
Characteristics of the Alluvium and Terrace Deposits along the Beaver-North Canadian
River from the Panhandle to Canton Lake in Northwestern Oklahoma: U.S. Geological
Survey Open-File Report 96-446, based on a scale of 1:250,000, 1 diskette.
------1997b, Digital Data Sets That Describe Aquifer Characteristics of the Alluvial and Terrace
Deposits along the North Canadian River from Canton Lake to Lake Overholser in
Central Oklahoma: U.S. Geological Survey Open-File Report 96-447, based on a scale of
1:250,000, 1 diskette.
Adams, G.P., Runkle, Donna, Rea, Alan, and Becker, C.J., 1997, Digital Data Sets That Describe
Aquifer Characteristics of the Alluvial and Terrace Deposits along the North Canadian
River from Oklahoma City to Eufaula Lake in East-central Oklahoma: U.S. Geological
Survey Open-File Report 96-448, based on a scale of 1:250,000, 1 diskette.
Adams, G.P., Runkle, Donna, Rea, Alan, and Cederstrand, J.R., 1997, Digital Data Sets That
Describe Aquifer Characteristics of the Alluvium and Terrace Deposits along the
Cimarron River from Freedom to Guthrie in Northwestern Oklahoma: U.S. Geological
Survey Open-File Report 96-445, based on a scale of 1:250,000, 1 diskette.
Aller, L., Bennett, T., Lehr, J.H., Petty, R.J. and Hackett, G., 1987, DRASTIC: A Standardized
System for Evaluating Groundwater Pollution Potential Using Hydrogeologic Settings:
U.S. Environmental Protection Agency Report 600/2-87/035, 622 p.
Becker, C.J., Runkle, Donna, and Rea, Alan, 1997a, Digital Data Sets That Describe Aquifer
Characteristics of the Elk City Aquifer in Western Oklahoma: U.S. Geological Survey
Open-File Report 96-449, based on a scale of 1:63,360, 1 diskette.
------1997b, Digital Data Sets That Describe Aquifer Characteristics of the Enid Isolated Terrace
Aquifer in Northwestern Oklahoma: U.S. Geological Survey Open-File Report 96-450,
based on a scale of 1:62,500, 1 diskette.
13
------1997c, Digital Data Sets That Describe Aquifer Characteristics of the High Plains Aquifer
in Western Oklahoma: U.S. Geological Survey Open-File Report 96-451, based on scales
of 1:125,000 and 1:250,000, 2 diskettes.
------1997d, Digital Data Sets That Describe Aquifer Characteristics of the Tillman Terrace
Aquifer in Southwestern Oklahoma: U.S. Geological Survey Open-File Report 96-452,
based on a scale of 1:250,000, 1 diskette.
Cederstrand, J.R., 1996a, Digital Geologic Map of Ardmore-Sherman Quadrangles, South-
Central Oklahoma: U.S. Geological Survey Open-File Report 96-370, based on a scale of
1:250,000, 3 diskettes.
------1996b, Digital Geologic Map of Beaver County, Oklahoma: U.S. Geological Survey Open-
File Report 96-371, based on a scale of 1:250,000, 1 diskette.
----- 1996c, Digital Geologic Map of Cimarron County, Oklahoma: U.S. Geological Survey
Open-File Report 96-372, based on a scale of 1:250,000, 1 diskette.
----- 1996d, Digital Geologic Map of Clinton Quadrangle, West-Central Oklahoma: U.S.
Geological Survey Open-File Report 96-373, based on a scale of 1:250,000, 2 diskettes.
----- 1996e, Digital Geologic Map of Enid Quadrangle, North-Central Oklahoma: U.S.
Geological Survey Open-File Report 96-374, based on a scale of 1:250,000, 4 diskettes.
----- 1996f, Digital Geologic Map of Fort Smith Quadrangle, East-Central Oklahoma: U.S.
Geological Survey Open-File Report 96-375, based on a scale of 1:250,000, 2 diskettes.
----- 1996g, Digital Geologic Map of Lawton Quadrangle, Southwestern Oklahoma: U.S.
Geological Survey Open-File Report 96-376, based on a scale of 1:250,000, 3 diskettes.
----- 1996h, Digital Geologic Map of McAlester-Texarkana Quadrangles, Southeastern
Oklahoma: U.S. Geological Survey Open-File Report 96-377, based on a scale of
1:250,000, 3 diskettes.
----- 1996i, Digital Geologic Map of Oklahoma City Quadrangle, Central Oklahoma: U.S.
Geological Survey Open-File Report 96-378, based on a scale of 1:250,000, 2 diskettes.
----- 1996j, Digital Geologic Map of Texas County, Oklahoma: U.S. Geological Survey Open-
File Report 96-379, based on a scale of 1:250,000, 1 diskette.
----- 1996k, Digital Geologic Map of Tulsa Quadrangle, Northeastern Oklahoma: U.S.
Geological Survey Open-File Report 96-380, based on a scale of 1:250,000, 2 diskettes.
----- 1996l, Digital Geologic Map of Woodward Quadrangle, Northwestern Oklahoma: U.S.
Geological Survey Open-File Report 96-381, based on a scale of 1:250,000, 2 diskettes.
14
Cederstrand, Joel.R., and Rea, Alan, 1996, Watershed Boundaries and Digital Elevation Model
of Oklahoma Derived from 1:100,000-scale digital topographic maps: U.S. Geological
Survey Open-File Report 95-727, 1 CD-ROM. (URL address is:
http://wwok.cr.usgs.gov/public/gis.html).
ESRI (Environmental Systems Research Institute, Inc.), 1997, ARC/INFO Version 7.1.1:
Redlands, CA.
Runkle, Donna, and Rea, Alan, 1997a, with source data sets and supplemental information
provided by Mark F. Becker, Digital Data Sets That Describe Aquifer Characteristics of
the Rush Springs Aquifer in Western Oklahoma: U.S. Geological Survey Open-File
Report 96-453, based on a scale of 1:250,000, 1 diskette.
------1997b, with source data sets and supplemental information provided by Scott Christenson,
Digital Data Sets That Describe Aquifer Characteristics of the Central Oklahoma Aquifer
in Central Oklahoma: U.S. Geological Survey Open-File Report 96-454, based on a scale
of 1:250,000, 2 diskettes.
A-1
'   'HSWK WR :DWHU  )HHW 
5DQJH  5DWLQJ
      
      
       
       
       
        
      
:HLJKW   
Table A-1. Ranges and ratings for
depth to water
5   1HW 5HFKDUJH   ,QFKHV 
5DQJH  5DWLQJ
     
     
     
      
     
:HLJKW   
Table A-2. Ranges and ratings for
net recharge
A-2
6   6RLO 0HGLD
5DQJH  5DWLQJ
7KLQ RU $EVHQW   
*UDYHO   
6DQG  
3HDW  
6KULQNLQJ DQG RU $JJUHJDWHG &OD\  
6DQG\ /RDP  
/RDP  
6LOW\ /RDP  
&OD\ /RDP  
0XFN  
1RQVKULQNLQJ DQG 1RQDJJUHJDWHG &OD\  
:HLJKW   
Table A-4. Ranges and ratings for soil media
$   $TXLIHU 0HGLD
5DQJH  5DWLQJ 7\SLFDO 5DWLQJ
0DVVLYH 6KDOH      
0HWDPRUSKLF ,JQHRXV      
:HDWKHUHG 0HWDPRUSKLF ,JQHRXV      
*ODFLDO 7LOO      
%HGGHG 6DQGVWRQH  /LPHVWRQH DQG 6KDOH
6HTXHQFH
     
0DVVLYH 6DQGVWRQH      
0DVVLYH /LPHVWRQH      
6DQG DQG *UDYHO      
%DVDOW       
.DUVW /LPHVWRQH        
:HLJKW   
Table A-3. Ranges and ratings for aquifer media
A-3
7  7RSRJUDSK\  3HUFHQW 6ORSH 
5DQJH  5DWLQJ
      
     
      
       
     
:HLJKW   
Table A-5. Ranges and ratings for topography
,   ,PSDFW RI 7KH 9DGRVH =RQH 0HGLD
5DQJH                                        
5DWLQJ
&RQILQLQJ /D\HU    
6LOW FOD\      
6KDOH      
/LPHVWRQH      
6DQGVWRQH      
%HGGHG /LPHVWRQH  6DQGVWRQH  6KDOH      
6DQG DQG *UDYHO ZLWK VLJQLILFDQW 6LOW DQG &OD\      
0HWDPRUSKLF ,JQHRXV       
6DQG DQG *UDYHO      
%DVDOW       
.DUVW /LPHVWRQH        
:HLJKW   
Table A-6. Ranges and ratings for impact of the vadose zone media
A-4
&  +\GUDXOLF &RQGXFWLYLW\
 *3' )W  
5DQJH  5DWLQJ
       
         
         
          
           
        
:HLJKW   
Table A-7. Ranges and ratings for aquifer
hydraulic conductivity
60 0 60 120 Miles
Vulnerability Map of 12 Major Aquifers in Oklahoma
N
W E
S
Less Vulnerable
More Vulnerable
DRASTIC
70 - 79
80 - 99
100 - 119
120 - 139
140 - 159
160 - 178
No Data
Rivers
Lakes
PAYNE
LOGAN
KINGFISHER
OKLAHOMA
LINCOLN
POTTAWATOMIE
CLEVELAND
30 0 30 Miles
N
W E
S
Less Vulnerable
More Vulnerable
DRASTIC
70 - 79
80 - 99
100 - 119
120 - 139
140 - 159
160 - 178
No Data
Rivers
Lakes
Vulnerability Map of the Central Oklahoma Aquifer
DEWEY
CUSTER
WASHITA
KIOWA
COMANCHE
STEPHENS
GRADY
CADDO
CANADIAN
BLAINE
50 0 50 Miles
N
W E
S
Vulnerability Map of the Rush Springs Aquifer
Less Vulnerable
More Vulnerable
DRASTIC
70 - 79
80 - 99
100 - 119
120 - 139
140 - 159
160 - 178
No Data
Rivers
Lakes
CARTER
JOHNSTON
LOVE
MARSHALL
BRYAN CHOCTAW
ATOKA PUSHMATAHA
MCCURTAIN
30 0 30 60 Miles
N
W E
S
Vulnerability Map of the Antlers Aquifer
Less Vulnerable
More Vulnerable
DRASTIC
70 - 79
80 - 99
100 - 119
120 - 139
140 - 159
160 - 178
No Data
Rivers
Lakes
ROGER MILLS
CUSTER
BECKHAM WASHITA
30 0 30 Miles
Vulnerability Map of the Elk City Aquifer
N
W E
S
Less Vulnerable
More Vulnerable
DRASTIC
70 - 79
80 - 99
100 - 119
120 - 139
140 - 159
160 - 178
No Data
Rivers
Lakes
CIMARRON
TEXAS
BEAVER
HARPER
WOODWARD
ELLIS
ROGER MILLS
DEWEY
50 0 50 Miles
Vulnerability Map of the High Plains Aquifer
N
W E
S
Less Vulnerable
More Vulnerable
DRASTIC
70 - 79
80 - 99
100 - 119
120 - 139
140 - 159
160 - 178
No Data
Rivers
Lakes
KIOWA
JACKSON
TILLMAN
30 0 30 Miles
N
W E
S
Vulnerability Map of the Tillman Terrace Aquifer
Less Vulnerable
More Vulnerable
DRASTIC
70 - 79
80 - 99
100 - 119
120 - 139
140 - 159
160 - 178
No Data
Rivers
Lakes
WOODS
ALFALFA
MAJOR
GARFIELD
KINGFISHER LOGAN
BLAINE
Enid
Cimmarron
30 0 30 Miles
Vulnerability Map of the Cimarron River Alluvium and Terrace Aquifer
 and the Enid Isolated Terrace Aquifer
N
W E
S
Less Vulnerable
More Vulnerable
DRASTIC
70 - 79
80 - 99
100 - 119
120 - 139
140 - 159
160 - 178
No Data
Rivers
Lakes
HARPER
WOODWARD
DEWEY
MAJOR
BLAINE
CANADIAN
30 0 30 60 Miles
Vulnerability Map of the North Canadian River Alluvium
 and Terrace Aquifers (West) & (Central) 
N
W E
S
Less Vulnerable
More Vulnerable
DRASTIC
70 - 79
80 - 99
100 - 119
120 - 139
140 - 159
160 - 178
No Data
Rivers
Lakes
OKLAHOMA
LINCOLN
OKFUSKEE
POTTAWATOMIE
SEMINOLE
HUGHES
MCINTOSH
30 0 30 60 Miles
Vulnerability Map of the North Canadian River 
Alluvium and Terrace Aquifer (East)
N
W E
S
Less Vulnerable
More Vulnerable
DRASTIC
70 - 79
80 - 99
100 - 119
120 - 139
140 - 159
160 - 178
No Data
Rivers
Lakes