U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2013–5219

Prepared in cooperation with the Oklahoma Water Resources Board

Hydrogeology and Simulation of Groundwater Flow 

in the Central Oklahoma (Garber-Wellington) Aquifer, 

Oklahoma, 1987 to 2009, and Simulation of Available 

Water in Storage, 2010–2059
Cover. Lake Arcadia, Oklahoma, autumn 2010.

Back cover. Left: Waterfall near Guthrie, Oklahoma, autumn 2009. 

Upper right: Jessica Magers, Oklahoma Water Resources Board, autumn 2010. 

Lower right: Edmond Water Treatment Facility 2 in Arcadia, Oklahoma, autumn 2010. 

All photographs by Christopher R. Neel, Oklahoma Water Resources Board.
Hydrogeology and Simulation of 

Groundwater Flow in the Central Oklahoma 

(Garber-Wellington) Aquifer, Oklahoma, 

1987 to 2009, and Simulation of Available 

Water in Storage, 2010–2059

By Shana L. Mashburn, Derek W. Ryter, Christopher R. Neel, S. Jerrod Smith, and 

Jessica S. Magers

Prepared in cooperation with the Oklahoma Water Resources Board

Scientific Investigations Report 2013–5219

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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Suggested citation:

Mashburn, S.L., Ryter, D.W., Neel, C.R., Smith, S.J., and Magers, J.S., 2013, Hydrogeology and simulation of groundwater flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma, 1987 to 2009, and simulation of available 

water in storage, 2010–2059, U.S. Geological Survey Scientific Investigations Report 2013–5219, 92 p., 

http://dx.doi.org/10.3133/sir20135219.

ISSN 2328-031X (print) 

ISSN 2328-0328 (online) 

ISBN 978-1-4113-3761-9
iii

Acknowledgments

The authors wish to thank the Garber-Wellington Study Team, which included the authors of this 

report and John Harrington (Association of Central Oklahoma Governments), Scott Bowen (Tinker 

Air Force Base), Neil Suneson (Oklahoma Geological Survey), Scott Christenson [U.S. Geological Survey (USGS) Emeritus], Stanley Paxton (USGS), and Noel Osborn [National Park Service, 

formerly USGS and formerly Oklahoma Water Resources Board (OWRB)]. This Garber-Wellington 

Study Team met several times per year during the initial planning and implementation phase to 

discuss study progress and plans, and took several field trips to outcrops of the aquifer geologic 

units in the study area. The authors thank the City of Norman for providing access to production 

wells; Brian Hapke, Chris Mattingly, and Scott Aynes were gracious in assisting the field team 

for the study. Fred Rice and Sam Drain with the City of Edmond provided water-use data and 

access to production wells. The authors wish to thank additional OWRB scientists who helped 

collect data for the investigation described in this report: Theda Adkisson, Gene Dousset, Chris 

Maggard, Maria Moreno, Jason Shievers, and Rick Wicker. The authors extend their thanks to 

the many landowners who provided access to their property for hydrologic data collection. 

The authors wish to thank several USGS scientists involved in the data collection for the investigation described in this report and the authors wish to acknowledge them individually: Jason 

Lewis, Kevin Smith, Rachel Esralew (currently U.S. Fish and Wildlife Service, formerly USGS), 

and former USGS students Greg Helling and Rika Burr.
iv

Contents

Acknowledgments........................................................................................................................................iii

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................3

Purpose and Scope ..............................................................................................................................5

Physiography.........................................................................................................................................5

Climate....................................................................................................................................................5

Geology of the Central Oklahoma Aquifer.................................................................................................7

Geologic History and Depositional Environments...........................................................................7

Quaternary-Age Alluvium and Terrace Deposits...........................................................................10

Permian-Age Geologic Units ............................................................................................................10

Hennessey Group.......................................................................................................................10

Garber Sandstone and Wellington Formation.......................................................................10

Chase, Council Grove, and Admire Groups ...........................................................................13

Pennsylvanian-Age Geologic Units .................................................................................................13

Vanoss Formation ......................................................................................................................13

Characteristics of the Central Oklahoma Aquifer ..................................................................................13

Regional Groundwater Flow .............................................................................................................15

1986–87 Potentiometric Surface .............................................................................................15

2009 Potentiometric Surface....................................................................................................15

Comparison of Water Levels from 1986–87 to 2009..............................................................18

Aquifer Saturated Thickness ...................................................................................................18

Water-Level Fluctuations...................................................................................................................21

Withdrawals for Groundwater Use..................................................................................................27

Historical Groundwater Use ....................................................................................................28

Reported Groundwater Use .....................................................................................................28

Domestic Groundwater Use.....................................................................................................32

Streamflow and Base Flow ...............................................................................................................41

Recharge..............................................................................................................................................41

Recharge from Base-Flow Discharge....................................................................................45

Recharge from Rorabaugh Method........................................................................................46

Recharge Calculated Using the Soil-Water Balance Code................................................48

Aquifer Hydraulic Properties ............................................................................................................48

Norman Aquifer Test .................................................................................................................50

Hydrogeologic Framework.........................................................................................................................50

Percent Sand Data Sources and Standardization Methods .......................................................50

Lithologic Logs............................................................................................................................51

Gamma-Ray Logs.......................................................................................................................51

Spatial Distribution of Percent Sand ...............................................................................................55

Hydrogeologic Framework Results..................................................................................................55

Groundwater-Flow Model ..........................................................................................................................56

Conceptual Flow Model.....................................................................................................................56

Numerical Groundwater-Flow Model Construction......................................................................57
v

Assumptions ...............................................................................................................................61

Simulation Periods.....................................................................................................................61

Boundaries..................................................................................................................................61

Streams...............................................................................................................................61

Lakes ................................................................................................................................63

Recharge............................................................................................................................63

Withdrawals ......................................................................................................................63

Hydraulic Properties .................................................................................................................65

Quasi-Steady-State Simulation ........................................................................................................65

Simulation Inputs .......................................................................................................................67

Calibration Targets.....................................................................................................................67

Calibration Process ...................................................................................................................67

Simulation Results .....................................................................................................................70

Transient Simulation 1987–2009........................................................................................................70

Simulation Inputs .......................................................................................................................71

Calibration Targets.....................................................................................................................71

Calibration Process ...................................................................................................................71

Simulation Results .....................................................................................................................71

50-Year Predictive Simulation...........................................................................................................71

Simulation Inputs .......................................................................................................................73

Simulation Results .....................................................................................................................73

Simulation of Available Water in Storage.......................................................................................74

Methods.......................................................................................................................................74

Simulation Inputs .......................................................................................................................75

Simulation Results .....................................................................................................................76

Sensitivity Analysis.............................................................................................................................77

Methods.......................................................................................................................................77

Sensitivity Analysis Results .....................................................................................................77

Model Simplifications, Assumptions, and Limitations...........................................................................79

Summary........................................................................................................................................................80

Selected References...................................................................................................................................83

Appendix 1. Aquifer Test.............................................................................................................................90

Figures

1. Map showing Central Oklahoma aquifer location, counties, cities, continuousrecorder wells, periodic water-level wells, cooperative observer stations, and 

Mesonet weather stations ..........................................................................................................4

2. Graph showing annual precipitation 1893–2009, 5-year moving average, and the

number of cooperative observer stations recording during each year in the 

Central Oklahoma aquifer study area........................................................................................6

3. Graph showing the average monthly precipitation during the time periods

1950–1979 and 1980–2009 for cooperative observer stations in the Central

Oklahoma aquifer study area......................................................................................................7

4. Map showing surficial geologic units in the extent of the Central 

Oklahoma aquifer..........................................................................................................................8

...
vi

5. Cross-section A–Aʹ diagram showing bedrock geologic units of the 

Central Oklahoma aquifer............................................................................................................9

6. Map showing the altitude of the base of the Hennessey Group (Hennessey

confining unit)..............................................................................................................................11

7. Map showing the altitude of the base of the Wellington Formation..................................12

8. Map showing the altitude of the base of the combined Chase, Council Grove, 

and Admire Groups.....................................................................................................................14

9. Map showing potentiometric-surface contours (1986–87) and direction of

groundwater flow in the Central Oklahoma aquifer..............................................................16

10. Map showing potentiometric-surface contours (2009) and direction of 

groundwater flow in the Central Oklahoma aquifer..............................................................17

11. Map showing altitude of the base of fresh groundwater....................................................19

12. Map showing saturated thickness (2009) in the Central Oklahʹoma aquifer....................20

13. Graphs showing water levels from Oklahoma Water Resources Board Mass

Measurement Program wells showing possible long-term (greater than 10 years)

precipitation response in the Central Oklahoma aquifer area............................................22

14. Graphs showing water levels from Oklahoma Water Resources Board Mass

Measurement Program wells showing possible response from localized

groundwater pumping in the Central Oklahoma aquifer area.............................................23

15. Graph showing water levels from USGS wells showing possible pumping and

precipitation responses in the Central Oklahoma aquifer area..........................................24

16. Graphs showing water levels from Oklahoma Water Resources Board continuous

recorder wells showing possible long-term precipitation response in the Central

Oklahoma aquifer area ..............................................................................................................25

17. Graphs showing water levels from Oklahoma Water Resources Board continuous

recorder wells showing possible response from localized groundwater pumping in

the Central Oklahoma aquifer area..........................................................................................26

18. Graph showing water levels collected with a vented pressure transducer at

Oklahoma Water Resources Board well site 94941 and atmospheric pressure

measured at the Norman Mesonet Station in the Central Oklahoma aquifer..................27

19. Graph showing groundwater use from alluvium and bedrock sources in the 

Central Oklahoma aquifer, 1967–2008......................................................................................29

20. Graph showing groundwater use and estimated unreported use by type from 

the Central Oklahoma aquifer, 1967–2008...............................................................................30

21. Pie diagram showing average groundwater use by type from the Central 

Oklahoma aquifer, 1995–2008....................................................................................................31

22. Map showing average annual reported groundwater use by permitted user 

greater than 100 acre-feet/year from the Central Oklahoma aquifer, 1995–2008 ............33

23. Graph showing groundwater use by the City of Edmond from 1967–2008........................34

24. Map showing population served by domestic wells during the year 1990.......................35

25. Map showing percent change in population from 1980 to 1990 .........................................36

26. Map showing percent change in population from 1990 to 2000 .........................................37

27. Map showing estimated population served by domestic wells during the 

year 2000 ......................................................................................................................................38

28. Map showing estimated population served by domestic wells during the 

year 2010 ......................................................................................................................................39

29. Graph showing estimated domestic use derived for the Central Oklahoma 

aquifer from the 1980, 1990, 2000, and 2010 U.S. Census Bureau data..............................40
vii

30. Map showing U.S. Geological Survey streamflow-gaging stations and selected

surface-water basins and groundwater basins in the Central Oklahoma aquifer ..........43

31. Graph showing estimated quarterly recharge rates and average annual recharge

rate using the Rorabaugh method for the Deep Fork River near Arcadia, Oklahoma

basin for the period 1969 to 1983..............................................................................................47

32. Graph showing estimated quarterly recharge rates and average annual recharge

rate using the Rorabaugh method for the Little River near Tecumseh, Oklahoma

basin for the period 1943 to 1961..............................................................................................47

33. Map showing average annual recharge calculated using the Soil-Water-Balance

code for the Central Oklahoma aquifer for the period 1987–2009 in 3,280-ft by

3,280-ft grid cells.........................................................................................................................49

34. Diagram showing lithologic category bins for converting lithologic logs into

percent sand................................................................................................................................51

35. Map showing locations of lithologic logs and gamma-ray logs used for

hydrogeologic framework percent-sand analysis of the Central 

Oklahoma aquifer........................................................................................................................52

36. Bar charts showing distribution of depths of lithologic logs and gamma-ray logs

used for hydrogeologic framework percent-sand analysis in the Central 

Oklahoma aquifer........................................................................................................................53

37. Graph showing scaling technique used to convert a gamma-ray log into percent

sand for hydrogeologic framework percent-sand analysis in the Central 

Oklahoma aquifer........................................................................................................................54

38. Cross-section A–Aʹ diagram showing layers for which percent sand was

interpolated in the hydrogeologic framework of the Central Oklahoma aquifer .............56

39. Map showing interpolated percent sand and log locations for layers 1 through 

5 for the hydrogeologic framework and for layers 6 through 11 for the 

hydrogeologic

framework....................................................................................................................................58

40. Bar charts showing derived percent sand distributions from lithologic logs and

gamma-ray logs ..........................................................................................................................60

41. Map showing numerical groundwater-flow model grid and boundary conditions 

for the Central Oklahoma aquifer study ..................................................................................62

42. Map showing stream channel widths and wells from which reported use 

was simulated in the transient groundwater-flow model for the Central 

Oklahoma aquifer........................................................................................................................64

43. Map showing depths from land surface that estimated domestic use was

withdrawn for the transient groundwater-flow model for the Central Oklahoma

aquifer...........................................................................................................................................66

44. Block diagram of horizontal hydraulic conductivity per model cell viewed from 

the southwest and truncated at model row 70, showing higher conductivity in 

the center of the aquifer and the low conductivity of the Hennessey Group on 

the west........................................................................................................................................67

45. Histogram of the distribution of head targets by model layer.............................................68

46. Map showing targets and residuals for the quasi-steady-state model for 1986–87

measurements.............................................................................................................................69

47. Graph showing simulated as compared to observed heads in the

quasi-steady-state model for 1986–87 measurements.........................................................70

48. Histogram of residuals from the head targets in the quasi-steady-state model for

1986–87 measurements .............................................................................................................70
viii

49. Map showing head residuals and error for the last stress period of the transient

model, 1987–2009 ........................................................................................................................72

50. Graph showing simulated as compared to observed heads in the transient model,

1987–2009 .....................................................................................................................................73

51. Histogram of residuals from the head targets in the transient model, 1987–2009 ..........73

52. Bar charts showing water budget for the transient model showing total flux for 

the period 1987–2009, by boundary condition........................................................................75

53. Map showing drawdown in the Central Oklahoma aquifer numerical model after 

50 years with 2009 pumping rates compared to the aquifer with no pumping.................75

54. Graph showing 50-year predictive model budget showing recharge, water 

removed from storage, groundwater pumpage, and base flow to streams 

assuming constant recharge and pumping at estimated 2009 rates .................................76

55. Graph showing percent of aquifer that had less than or equal to 15 feet of

saturated thickness at various pumping rates at the end of a 50-year period

(scenario 1)..................................................................................................................................77

56. Maps showing Central Oklahoma aquifer altitude of the water table (head) 

after 1, 25, and 50 years of pumping for the 2009–58 depletion-scenario 

simulation.....................................................................................................................................78

57. Graph showing percent of aquifer that had less than or equal to 15 feet of

saturated thickness at a pumping rate of 2 (acre-feet per acre) per year 

(scenario 2)..................................................................................................................................78

58. Graph showing changes in simulated heads at head targets in the transient 

model with percent changes in selected model parameters..............................................79

1–1. Schematic diagram showing layout of the aquifer test in the Central 

Oklahoma aquifer........................................................................................................................90

1–2. Graph showing the deep observation well water-level during the pumping 

(March 1–8) and recovery periods (March 8–16) of the Norman aquifer test 

in the Central Oklahoma aquifer, 2011.....................................................................................91

1–3. Graphs showing pumping drawdown data curves and derivatives with 

best-fit Hantush method with aquitard storage solution for leaky confined 

aquifer analysis...........................................................................................................................91

1–4. Graph showing water-level recovery data in Agarwal equivalent time with 

best-fit curve for the recovery analysis..................................................................................92
ix

Tables

1. Data collection time periods of precipitation at the cooperative observer stations

used in the Central Oklahoma aquifer study area...................................................................6

2. Stratigraphic column of geologic and hydrogeologic units in the Central Oklahoma

aquifer.............................................................................................................................................9

3. Reported and estimated groundwater-use statistics for the Central Oklahoma

aquifer, 1967–2008.......................................................................................................................30

4. Average annual reported and estimated groundwater use by type for the Central

Oklahoma aquifer, 1967–2008....................................................................................................31

5. Largest users of groundwater from the Central Oklahoma aquifer from 1995 to 2008 ...32

6. Cumulative population data and estimated domestic water use derived from the

1980, 1990, 2000, and 2010 census for the Central Oklahoma aquifer................................40

7. Streamflows at USGS streamflow-gaging stations in the vicinity of the Central

Oklahoma aquifer summarized through 2009.........................................................................42

8. Streamflow measurements (at base flow) and calculated recharge rates from small

selected streams located near the Central Oklahoma aquifer...........................................44

9. Water budget and inflow-outflow discrepancy for the transient model...........................74

10. Sensitivity of simulated heads to changes in parameters in the transient model...........79
x

Conversion Factors

This report contains a mixture of inch/pound and System International (SI) units. The water 

management in Oklahoma traditionally works in acre-feet units, whereas the numerical 

groundwater-flow model was built in SI units. Measurements and calculations are reported in 

units appropriate to the subject under discussion and not converted to one system of units.

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.004047 square kilometer (km2)

square foot (ft2) 929.0 square centimeter (cm2)

square foot (ft2) 0.09290 square meter (m2)

square inch (in2) 6.452 square centimeter (cm2)

section (640 acres or 1 square mile) 259.0 square hectometer (hm2) 

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 0.003785 cubic meter (m3) 

million gallons (Mgal) 3,785 cubic meter (m3)

cubic foot (ft3) 28.32 cubic decimeter (dm3) 

cubic foot (ft3) 0.02832 cubic meter (m3) 

acre-foot (acre-ft) 1,233 cubic meter (m3)

Flow rate

acre-foot per day (acre-ft/d) 0.01427 cubic meter per second (m3/s)

acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m3/yr)

acre-foot per year (acre-ft/yr) 0.001233 cubic hectometer per year (hm3/yr)

foot per second (ft/s) 0.3048 meter per second (m/s)

foot per day (ft/d) 0.3048 meter per day (m/d)

foot per year (ft/yr) 0.3048 meter per year (m/yr)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic foot per day (ft3/d) 0.02832 cubic meter per day (m3/d)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Specific capacity

gallon per minute per foot [(gal/min)/ft)] 0.2070 liter per second per meter [(L/s)/m]

Hydraulic conductivity

feet per day (ft/d) 0.3048 meter per day (m/d)

Transmissivity*

foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d) 
xi

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square meter (m2

) 0.0002471 acre 

square hectometer (hm2

) 2.471 acre

square kilometer (km2

) 247.1 acre

square centimeter (cm2

) 0.001076 square foot (ft2)

square meter (m2

) 10.76 square foot (ft2) 

square centimeter (cm2

) 0.1550 square inch (ft2) 

square hectometer (hm2

) 0.003861 section (640 acres or 1 square mile)

square kilometer (km2

) 0.3861 square mile (mi2)

Volume

liter (L) 0.2642 gallon (gal)

cubic meter (m3

) 264.2 gallon (gal) 

cubic meter (m3

) 0.0002642 million gallons (Mgal) 

cubic meter (m3

) 35.31 cubic foot (ft3)

cubic meter (m3

) 0.0008107 acre-foot (acre-ft) 

Flow rate

cubic meter per second (m3

/s) 70.07 acre-foot per day (acre-ft/d) 

cubic meter per year (m3

/yr) 0.000811 acre-foot per year (acre-ft/yr) 

meter per second (m/s) 3.281 foot per second (ft/s) 

meter per day (m/d) 3.281 foot per day (ft/d)

meter per year (m/yr) 3.281 foot per year ft/yr) 

cubic meter per second (m3

/s) 35.31 cubic foot per second (ft3/s)

cubic meter per day (m3

/d) 35.31 cubic foot per day (ft3/d) 

liter per second (L/s) 15.85 gallon per minute (gal/min) 

cubic meter per day (m3

/d) 264.2 gallon per day (gal/d) 

cubic meter per second (m3/s) 22.83 million gallons per day (Mgal/d) 

millimeter per year (mm/yr) 0.03937 inch per year (in/yr) 

kilometer per hour (km/h) 0.6214 mile per hour (mi/h)

Specific capacity

liter per second per meter [(L/s)/m] 4.831 gallon per minute per foot 

[(gal/min)/ft]

Hydraulic conductivity

meter per day (m/d) 3.281 foot per day (ft/d) 

Transmissivity*

meter squared per day (m2

/d) 10.76 foot squared per day (ft2/d) 
xii

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88). The NAVD 88 replaced the National Geodetic Vertical Datum of 1929 (NGVD 29), 

previously known as the Sea Level Datum of 1929.

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Water year is the 12-month period October 1 through September 30, designated by the calendar 

year in which the water year ends.

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

*Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times 

foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot 

squared per day (ft2/d), is used for convenience.
Hydrogeology and Simulation of Groundwater Flow in the 

Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma, 

1987 to 2009, and Simulation of Available Water in 

Storage, 2010–2059

By Shana L. Mashburn, Derek W. Ryter, Christopher R. Neel, S. Jerrod Smith , and Jessica S. Magers

Abstract

The Central Oklahoma (Garber-Wellington) aquifer 

underlies about 3,000 square miles of central Oklahoma. The 

study area for this investigation was the extent of the Central 

Oklahoma aquifer. Water from the Central Oklahoma aquifer 

is used for public, industrial, commercial, agricultural, and 

domestic supply. With the exception of Oklahoma City, all 

of the major communities in central Oklahoma rely either 

solely or partly on groundwater from this aquifer. The Oklahoma City metropolitan area, incorporating parts of Canadian, 

Cleveland, Grady, Lincoln, Logan, McClain, and Oklahoma 

Counties, has a population of approximately 1.2 million people. As areas are developed for groundwater supply, increased 

groundwater withdrawals may result in decreases in long-term 

aquifer storage. The U.S. Geological Survey, in cooperation 

with the Oklahoma Water Resources Board, investigated the 

hydrogeology and simulated groundwater flow in the aquifer 

using a numerical groundwater-flow model. 

The purpose of this report is to describe an investigation 

of the Central Oklahoma aquifer that included analyses of the 

hydrogeology, hydrogeologic framework of the aquifer, and 

construction of a numerical groundwater-flow model. The 

groundwater-flow model was used to simulate groundwater 

levels and for water-budget analysis. A calibrated transient 

model was used to evaluate changes in groundwater storage 

associated with increased future water demands.

The Central Oklahoma aquifer consists of Quaternaryage alluvium and terrace deposits and the Permian-age Garber 

Sandstone, Wellington Formation, and Chase, Council Grove, 

and Admire Groups. Groundwater flows between these geologic units and many wells are completed in the Quaternaryage and Permian-age units in the study area. The investigation 

described in this report focused more on the Permian-age 

units because water in the Quaternary-age alluvium and 

terrace was volumetrically a small fraction compared to the 

Permian-age units.

Analysis of regional groundwater flows indicate that 

groundwater in the shallow, local flow systems discharge to 

nearby streams and the rate of flow and flux of water are greatest in these local flow systems. Flow in the deeper part of the 

aquifer is slower and flowlines are longer than in the shallow, 

local flow systems. In the deeper flow system, groundwater 

flows under small streams to discharge primarily to the Deep 

Fork River and Little River. Flow in the Central Oklahoma 

aquifer is slowest in the confined part of the Garber Sandstone 

and Wellington Formation and in the less transmissive parts of 

the unconfined flow system, which includes part of the Chase, 

Council Grove, and Admire Groups. Groundwater in the 

confined part of aquifer comes from recharge primarily from 

a small area of the unconfined part of the aquifer near 35°23ʹ 

latitude and 97°23ʹ longitude as shown by the mound of water 

on the potentiometric-surface maps.

Groundwater levels measured in this aquifer in 2009 

were compared to water levels measured in 1986–87. Groundwater levels measured in wells in both the 1986–87 and 2009 

time periods were compared (169 wells). The difference in the 

median depth-to-water measurements for the two time periods 

was a decline of 3.75 feet. A water-level decline of 3.75 feet 

multiplied by the area of the aquifer (3,000 square miles), 

multiplied by the minimum and maximum porosity expected 

for this aquifer (14 to 30 percent) indicated change of water 

in storage from 1986–87 to 2009 ranging from 1,008,000 

to 2,160,000 acre-feet, assuming that all water from aquifer 

storage came from unconfined conditions. This loss in storage 

from 1986–2009 period, averaged per year, was about 44,000 

to 94,000 acre-ft/yr.

Water levels from wells measured by the Oklahoma 

Water Resources Board Mass Measurement Program and 

in the U.S. Geological Survey National Water Information 

System database indicate that shallow wells are affected 

by barometric-pressure changes, precipitation, and pumping from nearby shallow wells. Water levels in deeper wells 

in the aquifer had minimal response to precipitation and 
2 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

barometric-pressure changes, but responded to pumping from 

nearby deep wells.

Groundwater-use data were compiled from annual 

water-use reports submitted by permit holders to the Oklahoma Water Resources Board. Including estimated unreported 

groundwater use, average groundwater use from 1967 to 2008 

was about 37,367 acre-feet/year with public-water supply 

consuming 23,367 acre-feet/year, or about 63 percent of the 

average annual reported and estimated unreported groundwater use. Domestic groundwater use was estimated by using 

the 1990 census long-form data and population change compared to 1980, 2000, and 2010 census data. Average estimated 

domestic groundwater use from the aquifer from 1980 to 2010 

was about 13,752 acre-feet/year.

Recharge rates to the Central Oklahoma aquifer were 

estimated or calculated using three methods that varied in 

spatial and temporal scales. Recharge rates were estimated 

by using a basin-scale base-flow-discharge method, a basinscale recession-curve displacement (Rorabaugh) method, and 

a regional-scale method using the Soil-Water Balance code. 

The Soil-Water Balance method was used to estimate initial 

recharge for the groundwater-flow model because this method 

estimates spatial distribution of recharge for the aquifer area. 

Average annual recharge from the Soil-Water Balance code 

for the gridded aquifer area for the 1987–2009 period was 

4.6 inches. However, during model calibration, a scaling factor of 0.4 was applied to Soil-Water Balance recharge, which 

resulted in 1.84 inches per year of average annual recharge 

values for the gridded aquifer area for the 1987–2009 period.

Aquifer hydraulic properties were estimated from lithologic and geophysical well logs and a multiple-well aquifer 

test was analyzed to determine transmissivity and a storage 

coefficient. Transmissivity determined from the aquifer test 

at a production well near Norman, Oklahoma was 220 square 

feet per day. The geohydrologic-unit hydraulic conductivity 

was 2.4 feet per day. The storage coefficient from the analytical solution was 0.0013. This storage coefficient indicates that, 

even though the Central Oklahoma aquifer extends to land surface with a potentiometric surface below the top of the Central 

Oklahoma aquifer, the groundwater system acts as a confined 

system due to laterally extensive interbedded mudstone and 

large contrasts in vertical hydraulic conductivity.

The objective of developing the hydrogeologic framework of the Central Oklahoma aquifer system was to provide 

a three-dimensional representation of the lithologic variability 

of aquifer materials at a scale that captured the regional controls on groundwater flow for input to the groundwater-flow 

model. Lithologic logs and gamma-ray logs were converted 

to percent sand, which was used as a proxy in the estimation of initial hydraulic conductivity of the aquifer for the 

groundwater-flow model. 

A MODFLOW groundwater-flow model was developed 

to simulate groundwater flow and build water budgets in the 

Central Oklahoma aquifer. The Central Oklahoma aquifer was 

simulated using a grid comprised of 3,280-feet by 3,280-feet 

(1-kilometer by 1-kilometer) cells and 11 horizontal layers, 

each 100-feet thick (30.48 meters). The quasi-steady-state 

model was run to simulate the 1987 calendar year with 

equilibrium in flow and minimal changes in storage. Initial 

hydraulic conductivity used for the groundwater-flow model 

ranged from 0.33 to 3.3 feet per day and was estimated for 

each model cell using the percent sand from the hydrogeologic 

framework. The quasi-steady-state model was calibrated to 

a subset of the 1986–87 water levels. Parameters that were 

adjusted to affect quasi-steady-state model calibration included 

hydraulic conductivity, vertical anisotropy, and recharge. 

Recharge for the groundwater-flow model was set to 0.4 

multiplied by the Soil-Water Balance recharge estimate. There 

was no apparent horizontal or vertical spatial bias to model 

error and the residuals indicated that the simulated hydraulic 

heads are slightly lower than the observed hydraulic heads, but 

most residuals were near zero. These results indicate that there 

is random error in the model, a large component of which is 

related to the discretization that could not accommodate local 

variation. Hydraulic heads in the aquifer have been well simulated using the spatial distribution of percent sand. 

The transient groundwater-flow model was constructed 

to cover the period from 1987 through 2009. Because pumping rates for public water-supply wells were only available 

on annual intervals, each year was chosen as a stress period. 

The transient model was calibrated to all available water-level 

measurements for the aquifer during the period of the simulation (1987–2009). Parameters adjusted during the transient 

calibration process included the specific yield and specific 

storage of the aquifer, and the average annual recharge rate. 

The largest flux to the model is recharge, with water removed 

from storage, seepage from reservoirs, and water lost from the 

aquifer to streams being lesser amounts. Outflow is dominated by base flow to streams and pumping from wells. Water 

was removed from storage to meet the total outflow which 

indicates the aquifer was in a deficit (losing water) during 

this period.

The purpose of the 50-year predictive simulation was 

to estimate the change in groundwater in storage if water 

use continues for 50 years at 2009 rates. The period of the 

predictive model was 2010 through 2059. The 50-year predictive simulation used the same model inputs as the calibrated 

transient model except for recharge and pumping. Because 

this study did not attempt to simulate effects from a predictive 

climate model, recharge was held constant at the average flux 

for each cell that was specified for the 1987–2009 time period. 

Pumping was held constant at the 2009 average daily discharge for each well. Estimation of the effect to water levels in 

the aquifer by continuously pumping at the 2009 pumping rate 

for 50 years was achieved by running the model without any 

pumping, and then running the model with pumping. The difference in hydraulic heads and water in storage between those 

model runs was used to estimate the effect of pumping to storage in the aquifer. Pumping at the 2009 rate for 50 years with 

constant recharge resulted in drawdown in upland areas and 

reduction of water in storage. The recharge rate was substantially higher than the total pumping rate, but water discharge 
Introduction 3

to streams combined with pumping created a deficit that was 

met by releasing water from aquifer storage and decreasing 

base flow to streams. 

The calibrated transient model also was run to determine 

how much water could hypothetically be extracted from the 

Central Oklahoma aquifer in a 50-year period (scenario 1), 

and the effect of pumping the temporary state-apportioned 

rate of 2 (acre-feet/acre)/year (scenario 2). The purpose of 

this analysis was to provide estimates of the amount of water 

in storage in the Central Oklahoma aquifer. These scenarios 

were used to simulate the equal proportionate share by placing 

a well in every model cell and pumping at a constant rate. 

The first scenario determined the discharge rate at which 

wells placed in every model cell would have to be pumped so 

that just 15 feet (4.57 meters) or less of saturated thickness 

remained in 50 percent of the aquifer area (50 percent of the 

model cells) after 50 years. The second scenario was to pump 

2 (acre-feet/acre)/year from every model cell, and to determine 

the time at which one-half of the aquifer area was reduced 

to 15 feet or less of saturated thickness. For scenario 1, the 

pumping rate at all cells that reduced the saturated thickness 

in one-half of the cells to or below 15 feet (4.57 meters) after 

50 years was between 1.1 and 1.5 (acre-feet/acre)/year. The 

results of scenario 2 indicate the aquifer would be 50 percent depleted after between 35 and 41 years of pumping 

2 (acre-feet/acre)/year using 10 percent increase and decrease 

in specific yield. This analysis indicates that this pumping 

rate of 2 (acre-feet/acre)/year is not sustainable for more than 

41 years if every landowner with a potential well in each acre 

in the Central Oklahoma aquifer exercised their temporary 

right to pump at that rate. 

Introduction

The Central Oklahoma aquifer underlies about 

3,000 square miles of central Oklahoma (fig. 1). Water from 

the Central Oklahoma aquifer is used for public, industrial, 

commercial, agricultural, and domestic supply (Parkhurst and 

others, 1996). With the exception of Oklahoma City (fig. 1), 

all of the major communities in central Oklahoma rely either 

solely or partly on groundwater from this aquifer (Oklahoma 

Water Resources Board, 2011). The Oklahoma City metropolitan area, incorporating parts of Canadian, Cleveland, Grady, 

Lincoln, Logan, McClain, and Oklahoma Counties (fig. 1), has 

a population of approximately 1.2 million people, estimated 

from the 2010 census (U.S. Census Bureau, 2010) and is 

expected to increase by 20 percent from 2000 to 2030 (Oklahoma Department of Commerce, 2012). Residential development also is moving into rural areas, resulting in increased 

groundwater withdrawals from areas with previous minimal 

development. As areas are developed for groundwater supply, 

increased groundwater withdrawals may result in decreases in 

long-term aquifer water storage.

As of 2013, the Oklahoma Water Resources Board 

(OWRB) had not determined the maximum annual yield of 

groundwater from the Central Oklahoma aquifer. The maximum annual yield of a groundwater basin is defined by the 

OWRB to be the total amount of fresh groundwater that can 

be withdrawn while allowing a minimum 20-year life of a 

(groundwater) basin subsequent to that withdrawal (Oklahoma 

Water Resources Board, 2010). A groundwater basin is defined 

by the OWRB as “a distinct underground body of water by 

contiguous land having substantially the same geological and 

hydrological characteristics and yield capabilities.” “Life of 

a groundwater basin or subbasin” is defined by the OWRB 

as “....that period of time during which at least fifty percent 

of the total overlying land of the basin or subbasin will retain 

a saturated thickness allowing pumping of the maximum 

annual yield for a minimum twenty-year life of such basin 

or subbasin, provided that after July 1, 1994, the average 

saturated thickness will be calculated to be maintained at 

five feet for alluvium and terrace aquifers and fifteen feet for 

bedrock aquifers unless otherwise determined by the Board 

[OWRB];....” (Oklahoma Water Resources Board, 2010). 

The average saturated thickness of an aquifer is determined 

through hydrologic investigations. After the maximum annual 

yield has been established, the amount of water allocated to 

each permit applicant will be proportionate to the amount 

of land owned or leased by that applicant. This amount of 

water is referred to as the landowner’s equal proportionate 

share. For example, if a permit applicant owns 100 acres, 

and the equal proportionate share has been determined to be 

1.5 (acre-feet/acre)/year, which is abbreviated in the remainder 

of this report as (acre-ft/acre)/yr, then that permit applicant is 

allocated 150 acre-feet per year. Oklahoma water law (Oklahoma Statutes Title 82 Section 1020.5, 2011) states that certain 

factors be considered in the determination of the maximum 

annual yield of a major groundwater basin: total land area 

overlying the basin, the amount of water in storage in the 

basin, the rate of recharge, and total discharge from the basin, 

transmissivity of the basin, and the possibility of pollution 

from natural sources. 

To determine the maximum annual yield of a major 

groundwater basin, a hydrologic investigation is completed 

to obtain data and information related to the hydrology and 

hydrogeologic framework of the aquifer. Hydrologic data 

collected includes precipitation, water-level measurements, 

potentiometric-surface maps, measurements of transmissivity 

and storage coefficients, streamflow data, and geochemical 

data. Hydrogeologic framework data for this study consisted 

of lithologic properties extrapolated from gamma-ray logs and 

drillers’ lithologic logs, base-of-formation maps, and baseof-freshwater maps. A numerical groundwater-flow model 

can be developed using these data and information from the 

hydrologic investigation to conceptualize the flow system and, 

in turn, to evaluate effects of water withdrawals on the aquifer. 

Until the hydrology has been investigated and a maximum 

annual yield determined for a groundwater basin, the OWRB 

grants temporary permits to users allocating 2 acre-feet of 
4 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Map area

Study area

OKLAHOMA

Central Oklahoma aquifer from Runkle, Christenson, and Rea, 1997

9639

350816097233101

GUTHRIE 5S

PERKINS

KONAWA

CHANDLER

NORMAN 3SSE

OKLAHOMA CITY

WILL ROGERS

AIRPORT

SHAWNEE

122382

127446

122506

109355

129814

127559

127104

120577 122378

122695

118584

94941

101448

101467

101450

127759 128507

352646097231601

352956097290001

9624

9619

28776

9623

9622

352449097293201

Base from Horizon Systems Corporation, 2010, University of Oklahoma 

Center for Spatial Analysis, 2013, and U.S. Census Bureau, 2001

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

0 5 10 20 KILOMETERS

0 5 10 20 MILES

97°30’ 97°00’

36°00’

35°30’

35°00’

EXPLANATION

Cities and incorporated places

Extent of Central Oklahoma aquifer (study area)

Cooperative observer station (precipitation, 

snowfall, and temperature) and identifier

Continuous recorder well with Oklahoma 

Water Resources Board (OWRB) identifier

Mesonet weather station and continuous 

recorder well with OWRB identifier

Periodic water-level well with OWRB 

identifier

Periodic water-level well with U.S. Geological Survey identifier

City and name

127559

94941

350816097233101

9639

Bethany

Del

City

Edmond

Guthrie

Midwest

City

Midwest

City

Moore

Mustang

Norman

Oklahoma City

Shawnee

The Village

Yukon

Cimarron Riv er

Little River

Canadian Riv er

NorthCana dian River

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

44

35

240 40

40

35

44

NORMAN

Luther

Wildhorse Cr

Tecumseh

Purcell

Arcadia Deep Fork River

Tinker Air Force Base

Jones

Spencer

Harrah

Choctaw

Nicoma Park

Eason

Pond Creek

Eason

Figure 1. Central Oklahoma aquifer location, counties, cities, continuous-recorder wells, periodic water-level wells, cooperative 

observer stations, and Mesonet weather stations.
Introduction 5

water per acre of land per year (Oklahoma Water Resource 

Board, 2010). The U.S. Geological Survey, in cooperation 

with the Oklahoma Water Resources Board, investigated the 

hydrogeology and simulated groundwater flow in the aquifer 

using a numerical groundwater-flow model. The U.S. Geological Survey provides unbiased, timely, and relevant information, studies, and data about groundwater resources of 

the Nation.

Purpose and Scope

The purpose of this report is to describe an investigation 

of the Central Oklahoma aquifer that included analyses of the 

hydrogeology, hydrogeologic framework of the aquifer, and 

construction of a numerical groundwater-flow model. The 

groundwater-flow model was used to simulate groundwater 

levels and to analyze water-budget for 1987 to 2009 and for 

various pumping scenarios during a 50-year predictive simulation (2010–2059). This report provides information to the 

OWRB that can be used to determine the maximum annual 

yield of groundwater from the Central Oklahoma aquifer 

based on proposed management plans. The scope of the hydrologic investigation is the Central Oklahoma aquifer, which 

encompasses the freshwater zone in the Garber Sandstone and 

Wellington Formation, including the underlying Chase, Council Grove, and Admire Groups, and the overlying alluvium and 

terrace deposits. The study area for this investigation was the 

extent of the Central Oklahoma aquifer (fig. 1).

Physiography

The Central Oklahoma aquifer underlies all or parts 

of Cleveland, Logan, Lincoln, Oklahoma, Payne, and Pottawatomie Counties (fig. 1). The eastern part of the study area 

is characterized by low hills, with topographic relief ranging 

from 30 to 200 feet. The western part of the study area consists 

of gently rolling grass-covered plains, with topographic relief 

of less than 100 feet. The highest altitude of the Central Oklahoma aquifer area is approximately 1,300 feet above the North 

American Vertical Datum of 1988 (NAVD 88) in the western 

part of the study area and the lowest altitude is approximately 

800 feet above NAVD 88 in the northeastern part of the 

study area along the Cimarron and Deep Fork Rivers (fig. 1) 

(Parkhurst and others, 1996). 

Climate

The Central Oklahoma aquifer is in an area having a continental subhumid climate. The average monthly temperature 

in Oklahoma County, which includes much of the study area, 

is approximately 60 degrees Fahrenheit, with a slight increase 

from the northern part of the county towards the south. The 

average maximum temperature typically is recorded in July 

at 93 degrees Fahrenheit and the average minimum temperature typically is recorded in January at 26 degrees Fahrenheit 

(Oklahoma Climatological Survey, 2011a). 

Precipitation data were obtained from the Oklahoma Climatological Survey’s Web site for seven cooperative observer 

(COOP) stations distributed across the extent of the Central 

Oklahoma aquifer (fig. 1); (Oklahoma Climatological Survey, 

2011b). Cooperative observer stations compose a climateobservation network for the National Weather Service at which 

volunteers record observations in a variety of land-use settings 

(National Weather Service, 2011). Daily maximum and minimum temperatures, snowfall, and 24-hour precipitation data 

are collected at these stations. The seven stations used for the 

investigation described in this report were Chandler, Guthrie 

5S, Konawa, Norman 3SSE, Oklahoma City Will Rogers 

Airport, Perkins, and Shawnee (fig. 1). Precipitation data were 

downloaded for the entire period of record, which varied for 

each station. Years with less than 10 months of data in the 

period of record for a station were omitted from the analysis 

and trace amounts of precipitation were not included. Climate 

data from the seven COOP stations spanned from 1893 at the 

Guthrie 5S station to 2009 at 7 stations. Precipitation data 

were not collected at some stations throughout the entire 

period of record (table 1).

Average annual precipitation in the study area from 

1893 to 2009 was 34.27 inches (fig. 2). The 30-year average annual precipitation from 1980 to 2009 in the study area 

was 37.95 inches. Rainfall trends for the period of record 

indicate (1) below-average precipitation from approximately 

1900 to 1940, (2) variable precipitation from 1950 to the mid 

1980s, and (3) an above-average precipitation from the 1980s 

until 2009.

Maximum monthly precipitation from 1980 to 2009 

was 5.18 inches in May, minimum monthly precipitation was 

1.33 inches in January, and the monthly average precipitation 

was 3.18 inches (fig. 3). The period from 1950 to 1979 had 

below-average precipitation spanning two substantial drought 

periods, with the average monthly precipitation of 2.78 inches, 

maximum average precipitation in May of 5.60 inches, and 

a minimum average precipitation in January of 1.08 inches 

(fig. 3). The difference in precipitation between the 1980–2009 

period and the previous 30-year period (1950–1979) is primarily related to increased precipitation during the months of 

March, June, October, November, and December during the 

1980–2009 period. Precipitation data (fig. 2) indicate that the 

1980 to 2009 period was markedly wetter compared to the 

previous period (1893–1979), and the investigation described 

in this report was based on hydrologic data collected during 

this wetter period.
6 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Table 1. Data collection time periods of precipitation at the cooperative observer (COOP) stations used in the Central Oklahoma 

aquifer study area.

Station 

number Station name (fig. 1) Period of record1 Number of years 1950–1979 average 1980–2009 average

1684 Chandler 1902–2009 99 32.60 35.82

3821 Guthrie 5S 1893–2009 110 31.09 37.70

4915 Konawa 1943–2009 67 36.27 40.20

6386 Norman 3SSE 1895–2009 101 33.27 38.13

6661 Oklahoma City Will Rogers Airport 1898–2009 106 31.05 36.10

7003 Perkins 1928–2009 78 33.19 36.82

8110 Shawnee 1902–2009 102 35.45 40.89

Average 33.28 37.95

1

Not continuous.

Above historic average (5-year moving average)

Below historic average (5-year moving average)

Annual precipitation

EXPLANATION

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Year

0

20

40

60

Precipitation, in inches

0

2

4

6

8

10

Number of stations

117-year average

 34.27 in.

Figure 2. Annual precipitation 1893–2009, 5-year moving average, and the number of cooperative observer stations recording during 

each year in the Central Oklahoma aquifer study area.
Geology of the Central Oklahoma Aquifer 7

Geology of the Central Oklahoma 

Aquifer

The Central Oklahoma aquifer consists of Quaternary-age 

alluvium and terrace deposits and Permian-age geologic units 

(figs. 4 and 5 and table 2) (Christenson and others, 1990). 

Groundwater flows between these geologic units and both the 

Quaternary-age and Permian-age units are used as a source of 

groundwater. The investigation described in this report focuses 

primarily on the Permian-age units because water stored in the 

Quaternary-age alluvium and terrace is a small fraction of the 

water stored in the Permian-age units. The Central Oklahoma aquifer is referred to locally as the Garber-Wellington 

aquifer because the Central Oklahoma aquifer is dominantly 

composed of the Permian-age Garber Sandstone and Wellington Formation. However, this report does not use the name 

Garber-Wellington aquifer because the flow system includes 

Quaternary-age alluvium and terrace deposits and parts of 

the underlying Chase, Council Grove, and Admire Groups 

(table 2).

Geologic History and Depositional Environments

Understanding the geologic history is useful for determining the best approach for characterizing the hydrogeologic 

framework and hydraulic conductivity of the Central Oklahoma aquifer. Central Oklahoma was located near the equator 

during the early Permian age and shifted between wet and dry 

climates (Ziegler, 1990). The Permian-age geologic units that 

make up the Central Oklahoma aquifer were deposited on a 

shallow depositional slope by a system of fluvial, deltaic and 

marginal marine environments (Breit, 1998). However, Kenney (2005) states that the directional variability in paleocurrent 

indicators provide evidence that the Garber Sandstone was 

dominantly a fluvial system. Sea levels of the inland sea that 

covered much of the midcontinent were fluctuating during the 

Permian time (Siemers and others, 2000), which resulted in 

a range of depositional environments that are indicated in the 

various rock types of the area. The rock types and textures of 

the Chase, Council Grove, and Admire Groups, for example, 

indicate frequent fluctuations between shallow marine and 

fluvial systems and transition to a carbonate shelf to the north 

January

February

March

April

May

June

July

August

September

October

November

December

0

2

4

6

Precipitation, in inches

1950–1979

1980–2009

EXPLANATION

Month

Figure 3. Average monthly 

precipitation during the time 

periods 1950–1979 and 1980–2009 

for cooperative observer stations 

in the Central Oklahoma aquifer 

study area.
8 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

A

A A′

׳A

0 105 20 KILOMETERS

0 5 10 20 MILES

97°30’ 97°00’

36°00’

35°30’

35°00’

Bethany

Del

City

Edmond

Guthrie

Midwest

City

Moore

Mustang

Norman

Oklahoma City

Shawnee

The Village

Yukon

Deep Fork River

Cimarron Riv er

Little River

Canadian Riv er

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

35

240 40

40

35

44

44

Stanley

Draper

Lake

Lake

Thunderbird

Lake

Hefner

Lake

Overholser

EXPLANATION

Quaternary-age alluvium

Quaternary-age terrace deposits

Permian-age Hennessey Group

Permian-age Garber Sandstone and Wellington

Formation (undifferentiated)

Permian-age Chase, Council Grove, and 

Admire Groups

Pennsylvanian Vanoss Formation

Extent of Central Oklahoma aquifer

Line of section—Section shown 

on figure 5

Lake

Arcadia

Central Oklahoma aquifer from Runkle, Christenson, and Rea, 1997

Geology from Heran, Green, and Stoeser, 2003

North Canadian RiverNorth Canadian River

Base from Horizon Systems Corporation, 2010, University of 

Oklahoma Center for Spatial Analysis, 2013, and U.S. Census 

Bureau, 2001

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 4. Surficial geologic units in the extent of the Central Oklahoma aquifer.
Geology of the Central Oklahoma Aquifer 9

Table 2. Stratigraphic column of geologic and hydrogeologic units in the Central Oklahoma aquifer.

a

[Shaded grey hydrogeologic units and thickness are considered part of the Central Oklahoma aquifer]

Erathem System Geologic unit Aquifer unit type Thickness, in feet

Cenozoic Quaternary

Alluvium

Aquifer

b

0–100

Terrace Deposits b

0–100

Paleozoic

Permian

Hennessey Group Confining c

0–600

Garber Sandstone

Aquifer b

1,165–1,600

Wellington Formation

Chase Group

Aquifer b Council Grove Group 570–940

Admire Group

Pennsylvanian Vanoss Formation Confining d

250–490

a

Modified from Parkhurst and others, 1989.

b

Christenson and others, 1992.

c

Wood and Burton, 1968.

d

Bingham and Moore, 1975.

?

1,500

1,000

500

NAVD 88

-500

WEST EAST

Cross-section line shown on figure 4. Modified from Schlottmann and others, 1998

Alluvium not shown on cross section 

because units are very thin.

FEET

VERTICAL SCALE GREATLY EXAGGERATED

Mustang

Moore

Shawnee

Garber Sandstone and

Wellington Formation,

undifferentiated

Chase, Council Grove,

and Admire Groups

Pennsylvanian geologic units,

undifferentiated

(includes the Vanoss Formation)

A A׳

Base of fresh groundwater

Hennessey Group

(confining unit)

Saline water

CANADIAN

COUNTY

CLEVELAND COUNTY POTTAWATOMIE COUNTY

0 105

0 5 10 15 MILES

15 KILOMETERS

Stanley

Draper

Lake Potentiometric

surface Aquifer

thickness

Thickness

of fresh

groundwater

Central

Oklahoma

aquifer

Figure 5. Cross-section A–Aʹ diagram (shown on figure 4) showing bedrock geologic units of the Central Oklahoma aquifer.
10 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

in Kansas (not shown on figures, outside of map extents). The 

rock types, textures, and strata of the Garber Sandstone and 

Wellington Formation indicate deposition of sand, silt, and 

clay eroded from the Ozark, Ouachita, and Arbuckle uplifts 

during a marine regression. The sediments were carried by a 

complex river system and delta flowing from east to west into 

the Anadarko Basin (Breit, 1998). The fine-grained texture 

of the Hennessey Group, a siltstone and shale, deposited on 

top of the Garber Sandstone, indicates a return of a shallow 

marine system during a minor sea-level rise or transgression. 

A thin coating of hematite, an iron mineral, gives the 

formations in the area a reddish brown or purple color (Breit, 

1998). Commonly referred to as red beds, there is a disagreement on the origin of the iron in the formations. Breit (1998) 

states that the history of reddening began during deposition, 

but continued into deep burial.

There is substantial local geologic variation in the Garber 

Sandstone and Wellington Formation caused by the meandering nature of fluvial and deltaic systems. The sandstone-tomudstone ratio in these units generally decreases downdip 

to the west, north of the Cimarron River, and south of the 

Canadian River (Gates and others, 1983). 

Quaternary-Age Alluvium and Terrace Deposits

Alluvium and terrace deposits in the study area of 

Quaternary-age can be found along all major streams in the 

study area. These deposits are composed of lenticular beds 

of unconsolidated or loosely consolidated clays, silt, sand, 

and gravel with thicknesses ranging from 0 to 100 feet (ft) 

(Parkhurst and others, 1996). Terrace deposits along the 

North Canadian and Canadian Rivers are typically eolian in 

origin or are remnants of older alluvium and terrace deposits. 

These terrace deposits are topographically above the alluvium 

as a result of down cutting of the fluvial system with time. 

Although similar in composition, the alluvium is younger in 

age and is constantly being reworked by the modern river and 

eolian processes.

Permian-Age Geologic Units

Beneath or adjoining the alluvium and terrace deposits 

are consolidated bedrock units of Permian-age. The Permianage geologic units in the Central Oklahoma aquifer study 

area dip gently to the west at approximately 50 feet per mile 

(Bingham and Moore, 1975). There are no mapped or major 

structural features in the geologic units comprising the Central 

Oklahoma aquifer. The main structural feature in the area, the 

Oklahoma City anticline, is located in the subsurface below 

the Permian-age geologic units and has little effect on attitude 

or fracturing of the rock units of the Central Oklahoma aquifer 

(Carr and Marcher, 1977).

Hennessey Group

The Permian-age Hennessey Group overlies the western 

part of the Central Oklahoma aquifer and consists of interbedded red shale, clay, and some siltstone or fine-grained 

sandstone (Parkhurst and others, 1996). The Hennessey Group 

is composed of the Bison Formation, Salt Plains Formation, Kingman Formation, and the Fairmont Shale (Bingham 

and Moore, 1975). Although not considered to be part of the 

Central Oklahoma aquifer, the Hennessey Group outcrops 

in the western one-third of the aquifer area and acts as a 

confining layer because of its small transmissivity. Although 

transmissivity of this unit is small, there are small-yield wells 

completed in the Hennessey Group that provide enough 

groundwater for local domestic and stock use. Total thickness 

of the Hennessey Group ranges from 600 to 650 feet (Wood 

and Burton, 1968). However, in the study area the top parts of 

this group have been removed by erosion, resulting in thicknesses ranging from 0 to approximately 600 feet (Wood and 

Burton, 1968). A structure-contour map of the altitude of the 

base of Hennessey Group determined from correlation of geophysical logs was published in Christenson and others (1992), 

(fig. 6).

Garber Sandstone and Wellington Formation

In the study area, the Permian-age Garber Sandstone and 

Wellington Formation have similar lithologies and differentiating the two units in surface outcrops and in the subsurface by 

geophysical logs or core samples is difficult. Therefore, these 

two geologic units are treated as a single hydrogeologic unit 

in this report. The Garber Sandstone and Wellington Formation consist of cross-bedded, fine-grained sandstone with 

interbedded shale or mudstone (Bingham and Moore, 1975; 

Parkhurst and others, 1996; Breit, 1998). The sand grains in 

these two geologic units are generally rounded to sub-rounded 

quartz and are poorly cemented, mainly by hematite (Gates 

and others, 1983). Sand and clay lenses are common and 

make stratigraphic-unit correlation difficult in the study area. 

Generally, these two geologic units consist of about 75 percent 

sand in the central area of the aquifer decreasing to about 

25 percent sand to the north and south (Wood and Burton, 

1968). Fluvial and deltaic sedimentary structures, such as 

ripple marks, channel cuts, crevasse splays, and cross-bedding, 

are evident in the Garber Sandstone and Wellington Formation (Siemers and others, 2000), which implies that hydraulic 

properties are heterogeneous and specific hydrogeologic units 

are discontinuous. Where a full section is present, thickness 

of these units can range from 1,165–1,600 ft with a median 

thickness of 1,510 ft (Christenson and others, 1992). The 

Garber Sandstone and Wellington Formation are exposed at 

the surface in the central part of the study area but have been 

removed by erosion to the east. A structure-contour map of 

the base of the Wellington Formation, showing dipping to 

the west, determined from correlation of geophysical logs is 

shown figure 7.
Geology of the Central Oklahoma Aquifer 11

800

800

0 84 16 MILES

0 84 16 KILOMETERS

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Structure contours modified from Christenson and 

others, 1992

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

Extent of Central Oklahoma aquifer

Eastern extent of Hennessey Group 

confining unit

Structural contour—Shows altitude of the 

base of the Hennessey Group, in feet. 

Contour interval 50 feet. Datum is 

National Geodetic Vertical Datum 

of 1929

EXPLANATION

800

1,000

1,200

1,000

Lake

Arcadia Hiwassee Lake

Deep Fork River

Lake

Hefner

Lake

Overholser

Lake

 Thunderbird

Bell Cow Lake

Lake

 Stanley Draper Shawnee

Lakes

Wes Watkins

Reservoir

Meeker Lake

Guthrie Lake

Tecumseh Lake

Langston Lake

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Liberty Lake

Figure 6. Altitude of the base of the Hennessey Group (Hennessey confining unit).
12 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

-400

1,000

1,000

1,200

1,000

1,000

1,000

800

800

200

600

200

-600

-200

0

400

600

400

800

0

-800

0 84 16 MILES

0 84 16 KILOMETERS

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Structure contours modified from Christenson and 

others, 1992

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

EXPLANATION

Eastern extent of Hennessey Group 

confining unit

Extent of Wellington Formation

Structural contour—Shows altitude of the 

base of the Wellington Formation, in 

feet. Contour interval 100 feet. 

Datum is National Geodetic Vertical 

Datum of 1929

Extent of Central Oklahoma aquifer

0

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 7. Altitude of the base of the Wellington Formation.
Characteristics of the Central Oklahoma Aquifer 13

Little published research has focused on the stratigraphy 

of the Garber Sandstone and Wellington Formation, except for 

several more recent Master’s theses by Nkoghe-Nze (2002), 

Gromadzki (2004), Abbott (2005), and Kenney (2005). Those 

theses were funded by the Environmental Protection Agency 

to obtain a better understanding of the stratigraphy in the 

aquifer and how that stratigraphy might affect arsenic concentrations in production wells completed throughout the aquifer 

(Smith and others, 2009). The theses reported that the Garber 

Sandstone and Wellington Formation consisted of lithofacies 

characteristic of stacked channel bars, floodplain deposits, and 

related fluvial deposits. These lithofacies change abruptly and 

also grade gradually into one another vertically and horizontally, leading to considerable heterogeneity and discontinuity. The theses also state that the variable lithofacies, lack of 

continuous marker beds, and scarcity of fossils in the aquifer 

make traditional stratigraphic correlation difficult, especially over distances greater than 1 mile. Gromadski (2004) 

and Kenney (2005), using standard sieve analysis, reported 

that particle sizes in the Garber and Wellington sandstones 

sampled at the surface in the vicinity of Cleveland County 

were very-fine to fine-grained (0.125–0.25 millimeters) and 

moderately-well to well-sorted. The particle size and sorting in 

the sandstones was uniform across central Oklahoma. 

Nkoghe-Nze (2002) studied the petrography of the Garber Sandstone and Wellington Formation. Nkoghe-Nze (2002) 

included analysis of petrographic thin sections from 5 core 

samples and 17 outcrop samples to describe the particle size, 

sorting, sandstone grain types, depositional matrix, and porefilling cement. In addition to collecting point-count data from 

new thin sections, the study used data and thin sections from 

Breit and others (1990), which reported porosity ranging from 

17 to 30 percent from thin-section point counts in 7 cores from 

the Central Oklahoma aquifer. Nkoghe-Nze (2002) reported 

that the average porosity for outcrop samples was 14 percent 

and in core samples was 20 percent. Nkoghe-Nze (2002) also 

reported that the porosity in the sandstones was a primary, preserved porosity, defined as porosity developed as the sediment 

was deposited and includes inter- and intra-particle porosity 

(Tucker, 1981, p. 62). Average cement content was 20 percent 

in outcrop samples and 11 percent in core samples, indicating less cement is in the subsurface than in outcrops. Less 

percent cement in the subsurface than in outcrops indicates 

that cementation may not play a major role in the distribution 

of hydraulic conductivity in the subsurface. The compactional 

texture of the sandstones in thin sections and the absence of 

quartz cement (dolomite is the most common type of cement) 

indicate that the Garber Sandstone and Wellington Formation 

have never been deeply buried or heated to high temperatures.

Chase, Council Grove, and Admire Groups

Stratigraphically below the Wellington Formation are 

the Chase, Council Grove, and Admire Groups, which were 

considered to be undivided in the investigation described in 

this report. The Chase, Council Grove, and Admire Groups 

are composed of cross-bedded, fine-grained sandstone, shale, 

and thin limestone (Bingham and Moore, 1975). A structurecontour map of the base of Chase, Council Grove, and Admire 

Groups, showing a westward dip, determined from correlation of geophysical logs is shown in figure 8. Christenson and 

others (1992) state that where complete sections are present in wells, the combined thickness of these groups ranged 

from 570 to 940 feet with a median of 745 feet. Bingham 

and Moore (1975) referred to the Chase, Council Grove, and 

Admire Groups as the Oscar Group and assigned this Group 

to the Pennsylvanian-age system. Lindberg (1987) referred 

to these units as the Chase, Council Grove, and Admire 

Groups of Permian age. The term Oscar Group was not used 

in this study; terminology of Chase, Council Grove, and 

Admire Groups follows the usage of the USGS and is used in 

this report.

Pennsylvanian-Age Geologic Units

There are no Pennsylvanian-age geologic units in the 

Central Oklahoma aquifer, however the Vanoss Formation is 

described in this report because the Vanoss Formation is considered to be a hydrologic boundary of little to no flow.

Vanoss Formation

The Vanoss Formation is the oldest geologic formation in the study area. The Vanoss Formation underlies the 

Chase, Council Grove, and Admire Groups and outcrops 

locally along the eastern boundary of the study area (figs. 

4 and 5). The Vanoss Formation consists of red-brown to 

grey shale and intermittent thin limestone and sandstone beds 

that range in total thickness from 250 to 490 feet (Bingham 

and Moore, 1975). This formation acts as a lower confining unit to the Central Oklahoma aquifer, limiting vertical 

groundwater movement. 

Characteristics of the Central 

Oklahoma Aquifer

The geologic-unit description and information presented 

in this section provide the hydrogeology, hydrogeologic 

framework, and distribution of hydraulic properties used to 

form the numerical groundwater-flow model in the Central 

Oklahoma aquifer. In particular, model layers representing 

hydrogeologic units of similar hydrogeologic characteristics 

for the groundwater-flow model would be rather improbable 

to discern for the Central Oklahoma aquifer. Vertical and 

horizontal lithofacies change causes local heterogeneity 

and discontinuity of specific layers and the difficulty of 

stratigraphic-unit correlation indicated that hydraulic properties for the model would have to depend on data that generalized lithology and general grain size.
14 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

0

400

600

200

1,000

-1,400

-1,600

-1,200

-1,000

-800

-600

-400

800

-200

0 84 16 MILES

0 84 16 KILOMETERS

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Structure contours modified from Christenson and 

others, 1992

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

EXPLANATION

Eastern extent of Hennessey Group 

confining unit

Structural contour—Shows altitude of the 

base of the Chase, Council Grove, and 

Admire Groups, in feet. Contour interval 100 feet. Datum is National Geodetic 

Vertical Datum of 1929

Extent of Central Oklahoma aquifer

-1,600

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 8. Altitude of the base of the combined Chase, Council Grove, and Admire Groups.
Characteristics of the Central Oklahoma Aquifer 15

The hydrogeology component of this investigation 

focused on groundwater flow through various lithologies in 

the aquifer, but also incorporated streamflows and recharge 

that are hydraulically connected and part of the groundwaterflow system. Potentiometric-surface data (synoptic water 

levels) were analyzed to describe regional groundwater flow 

and long-term (greater than 10 years) changes in groundwater 

levels. Groundwater-level fluctuations were analyzed to 

determine daily and seasonal trends with potential causes for 

those trends being attributed to variations in precipitation and 

barometric pressure, groundwater withdrawals, and changes 

in water use. Streamflow and base-flow data were summarized and recharge was estimated using methods applied at 

different scales. 

Regional Groundwater Flow

An investigation by Parkhurst and others (1996) used a 

numerical groundwater-flow model combined with geochemical and petrographic data to describe the characteristics of the 

Central Oklahoma aquifer flow system. Results from their 

analysis indicated that groundwater in the shallow, local flow 

systems discharge to nearby streams and that the rate of flow 

and flux of water are greatest in these local flow systems, with 

transit times of tens to hundreds of years. Flow in the deeper 

part of the aquifer is slower and flowlines are longer than in 

the shallow, local flow systems. In this deeper flow system, 

groundwater flows under overlying small streams to discharge 

primarily to the Deep Fork and Little Rivers. 

Transit times for groundwater flow in the Central Oklahoma aquifer can vary by several orders of magnitude. In the 

shallow flow systems, transit times may be tens to hundreds of 

years. In deeper flow systems that start along drainage basin 

divides, transit times are greater than 5,000 years (Parkhurst 

and others, 1994). Groundwater-flow in the Central Oklahoma 

aquifer is slowest in the confined part of the Garber Sandstone 

and Wellington Formation and in the less transmissive parts of 

the unconfined flow system, which includes part of the Chase, 

Council Grove, and Admire Groups. Groundwater in the confined part of the aquifer comes from recharge primarily from 

a small area of the unconfined part of the aquifer near 35°23ʹ 

latitude and 97°23ʹ longitude (near Tinker Air Force Base, 

location shown on figure 1) as seen in the mound of water on 

the potentiometric-surface maps (figs. 9 and 10). 

The direction of horizontal regional groundwater flow 

can be inferred from potentiometric-surface maps of the 

Central Oklahoma aquifer. The elevation of the potentiometric 

surface is defined as the level to which water rises in tightly 

cased wells. An aquifer with substantial vertical flow can 

have multiple potentiometric surfaces. Potentiometric head 

in the Central Oklahoma aquifer changes with depth, so no 

single potentiometric surface could be mapped and no attempt 

was made to construct a potentiometric-surface map for the 

deep parts of the aquifer. Most of the deep wells completed 

in the aquifer are constructed with long gravel packs and 

multiple open intervals (screens, slots, or perforations) and are 

completed in more than one sandstone layer, each having a 

different hydraulic head (hereinafter referred to as head). The 

potentiometric surfaces described in this report approximate 

only the upper zone of saturation in the Central Oklahoma 

aquifer, sometimes referred to as the water table. 

Water levels were measured in multiple wells across 

the Central Oklahoma aquifer in 1986–87 and 2009. The 

first measurement was done in 1986–87 as part of previous 

studies of the geochemistry and hydrogeology of the aquifer (Parkhurst and others, 1996; Christenson and others, 

1992) and the second measurement was done in 2009 as part 

of this investigation. Wells measured for the 1986–87 and 

2009 surveys were shallow (depth from land surface less 

than 300 feet), predominantly used for domestic supply, and 

were completed in the different geologic units in the Central 

Oklahoma aquifer, including the alluvial and terrace deposits. 

Many (169) of the wells measured in 2009 also were measured 

for the 1986–87 potentiometric-surface map. 

1986–87 Potentiometric Surface

A 1986–87 potentiometric-surface map was compiled 

in Christenson and others (1992) and Parkhurst and others 

(1996); (fig. 9). Water levels shown on that map were measured in more than 300 wells between December 22, 1986, and 

April 24, 1987. The 1986–87 water levels (depth to water, in 

feet below land surface) ranged from 1.5 to 177 with a median 

of 32 feet. The regional slope of the water table was west to 

east with considerable local variation. The 1986–87 potentiometric-surface map shows “V” patterns that point upstream 

along the Deep Fork River, indicating the Deep Fork River 

was a drain for the groundwater-flow system, also known as a 

gaining stream. The potentiometric contours do not substantially show a “V” pattern in the vicinity of the North Canadian 

River, which indicates that there is little exchange of water 

between the aquifer and North Canadian River. The 1986–87 

potentiometric-surface map shows that no streams on the aquifer are major sources of water to the groundwater-flow system, 

for example, few streams demonstrate the “V” pattern pointing 

downstream that would indicate that a stream was a major 

source of water to the groundwater-flow system, also known 

as a losing stream. 

2009 Potentiometric Surface

Water levels were measured in 280 wells as part of this 

investigation between February 17, 2009, and March 13, 2009. 

The 2009 potentiometric surface was published by Mashburn 

and Magers (2011). The 2009 water levels, in feet below land 

surface, ranged from 3.1 to 233.7 with a median of 35.8 feet 

(fig. 10). The potentiometric-surface altitude was calculated 

by subtracting depth to water from land-surface altitude. 

The land-surface altitude used for the 2009 potentiometricsurface map was determined by using a differentially corrected 
16 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

1,000

1,100

950

900

1,100

1,150

1,050

950

900

1,000

1250

1,200

1,150

950

1,050

950

1,000

1,100

950

1,100

1,250

1,200

900

1,150

1,300

950

1,100

950

850

1,000

1,250

1,100

1,000

1,000

850

1,100

1,050

950

950

900

1,100

1,050

1,000

950

1,050

950

1,000

1,050

1,100

1,100

1,000

1,100

1,100

0 84 16 MILES

0 84 16 KILOMETERS

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Potentiometric-surface contours and wells from

Christenson and others, 1992

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

1,100

Extent of Central Oklahoma aquifer

Eastern extent of Hennessey Group 

confining unit

Potentiometric contour—Shows altitude

at which water level would have 

stood in tightly cased wells, 1986–87. 

Contour interval 50 feet

General direction of groundwater flow

Water-level measurement, 1986–87

EXPLANATION

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 9. Potentiometric-surface contours (1986–87) and direction of groundwater flow in the Central Oklahoma aquifer.
Characteristics of the Central Oklahoma Aquifer 17

1,050

1,100

1,150

1,200

1,100

950

1,050

1,250

950

1,100

1,200

850

900 1,250

1,150

1,100

1,050

1,000

1,200

1,100

1,050

1,000

1,000

950

900

1,000

950

900

850

900

950

1,000

1,050

1,100

1,150

950

1,150

1,100

1,050

1,000

1,300 North Canadian River

0 84 16 MILES

0 84 16 KILOMETERS

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

Canadian River

1,050

Extent of Central Oklahoma aquifer

Eastern extent of Hennessey Group 

confining unit

Potentiometric contour—Shows altitude

at which water level would have 

stood in tightly cased wells, 2009. 

Contour interval 50 feet

General direction of groundwater flow

Water-level measurement, 2009

EXPLANATION

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Potentiometric-surface contours and wells from

Mashburn and Magers, 2011

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 10. Potentiometric-surface contours (2009) and direction of groundwater flow in the Central Oklahoma aquifer.
18 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Global Positioning System receiver with an accuracy of 

0.5 foot and referenced to the North American Vertical Datum 

of 1988 (NAVD 88). Stream and lake elevations, which were 

obtained from a USGS 10-meter (32.8-foot) digital elevation 

model (DEM) (Gesch, 2007), were included when contouring 

the potentiometric surface, except for the western part of the 

aquifer that is confined by the overlying Hennessey Group 

where the Central Oklahoma aquifer is not considered to be 

hydraulically connected to the alluvial and terrace deposits 

above the Hennessey Group. The potentiometric-surface 

contours were generated in a geographic information system 

(GIS) by using stream and lake elevation data from the DEM 

and the potentiometric-surface altitudes determined at wells. 

The contours were adjusted manually based on professional 

judgment to address inconsistencies, especially near streams 

and lakes.

Comparison of Water Levels from 1986–87 

to 2009

The water levels compared in this section of the report 

are only from those wells in which measurements were made 

in both the 1986–87 and 2009 time periods (169 wells). This 

comparison does not take into account the variability of water 

levels during the intervening years. Various factors also play 

roles in water-level changes and some factors may affect 

water levels on diurnal, seasonal, or annual timescales. These 

factors include tides, barometric-pressure changes, groundwater gains and losses from precipitation and streams, and 

groundwater losses to withdrawals. Similarities between the 

two maps include a regional slope from west to east, the Deep 

Fork River appearing to act as a drain to the groundwater-flow 

system, and the appearance of little or no exchange of water 

between the aquifer and the North Canadian River.

A (Wilcoxon) signed-rank test was used to determine if 

the 2009 water levels changed significantly from the 1986–87 

water levels. A (Wilcoxon) signed-rank test is a nonparametric 

statistical hypothesis test used to compare two related samples or repeated measurements on a single sample to assess 

whether their population distributions differ. The null hypothesis for the (Wilcoxon) signed-rank test is that the average of 

the 2009 depth-to-water measurements is equal to the average 

of the 1986–87 depth-to-water measurements. The alternative 

hypothesis is that the average of the 2009 depth-to-water measurements is different than the average of the 1986–87 depthto-water measurements. Using a significance level of 0.025 for 

an upper-tailed test, the z critical value is 1.96. If the z test statistic is greater than the z-critical value, then the null hypothesis is rejected in favor of the alternative hypothesis. The signed 

rank sum was 8,182 and resulting z-test statistic was 6.42. 

The z-test statistic of 6.42 is greater than the z-critical value 

of 1.96. Therefore, the null hypothesis is rejected in favor 

of the alternative. This statistical test indicates that the 2009 

depth-to-water measurements increased from the 1986–87 

depth-to-water measurements, and this increase is statistically 

significant. The difference in the median depth-to-water measurements between the same wells for the two time periods 

was a decline of 3.75 feet. This decline in water levels was 

not consistent across the aquifer. There were some areas with 

declines in water levels and other areas in the aquifer where 

water levels increased. Water-level changes across an aquifer 

are caused by many factors and vary spatially. To determine an 

approximate amount of water this water-level decline indicates 

for the water from storage from the aquifer, the difference in 

median water levels can be multiplied by the porosity and area 

of the aquifer. A water-level decline of 3.75 feet multiplied 

by the area of the aquifer (3,000 square miles), multiplied 

by the minimum and maximum porosity expected for this 

aquifer (14 to 30 percent) resulted in a calculated change of 

water in storage from 1986 to 2009 ranging from 1,008,000 to 

2,160,000 acre-ft, assuming all water from storage came from 

unconfined conditions. This loss in storage from 1986–2009 

period, when averaged per year, was approximately 44,000 

to 94,000 acre-ft/yr. Some water from storage in parts of this 

aquifer may come from confined conditions. Water released 

from an aquifer under confined conditions may reduce the 

head, but the potentiometric surface can remain the same and 

the aquifer remains saturated. If the water released from the 

Central Oklahoma aquifer was under confined conditions, then 

this calculation (using changes in water levels) of water from 

storage under confined conditions would be greater than the 

storage calculated under unconfined conditions.

Several factors could have caused this decrease in water 

levels from 1986–87 to 2009 in the Central Oklahoma aquifer. 

A decrease in water levels indicates that more water is leaving 

the groundwater system than is entering the groundwater system. Less precipitation or an increase in the intensity of precipitation rates also could cause a reduction in recharge to the 

groundwater system. An increase in groundwater withdrawals 

could cause water levels and storage to decline. This decline 

in groundwater levels could reduce groundwater discharge to 

streams, especially those connected to the groundwater-flow 

system, such as the Deep Fork and Little River.

Aquifer Saturated Thickness

The 2009 potentiometric-surface contours (fig. 10) were 

subtracted from the base of freshwater contours (fig. 11) to 

construct a saturated-thickness map for the Central Oklahoma 

aquifer (fig. 12). The map of the base of fresh groundwater 

used in this study is the same map published in Christenson 

and others (1992) and Parkhurst and others (1996). Data 

points from Hart’s (1966) base of fresh groundwater map 

also were included in the base of fresh groundwater map by 

Christenson and others (1992). Hart’s (1966) base of freshwater maps was determined from geophysical logs and based 

on a dissolved solids concentration of 5,000 milligrams per 

liter (mg/L). For this study, the base of fresh groundwater was 

defined at 5,000 mg/L dissolved solids as described by Hart 

(1966), Christenson and others (1992), and Parkhurst and 
Characteristics of the Central Oklahoma Aquifer 19

600

500

400

600

700

700

600

700

700

600

500

600

800

700

900

800

400

500

700

700

500

500

800

500

600

800

800

500

600

800

500

600

500

600

700

800

600

800

800

300

700

900

800

500

800

300

700

700

400

700

800

800

700

500

600

0 84 16 MILES

0 84 16 KILOMETERS

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Contours modified from Christenson and others, 1992

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

Extent of Central Oklahoma aquifer

Eastern extent of Hennessey Group 

confining unit

Water-quality-zone contour—Shows 

altitude of the base of fresh 

groundwater (less than or equal to 

5,000 milligrams per liter dissolved 

solids), in feet. Contour interval 

100 feet. Datum is National 

Geodetic Vertical Datum of 1929

EXPLANATION

700

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 11. Altitude of the base of fresh groundwater [constructed by Christenson and others (1992) using geophysical logs].
20 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

0 84 16 MILES

0 84 16 KILOMETERS

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

North Canadian River

Canadian River

Extent of Central Oklahoma 

aquifer

Eastern extent of Hennessey 

Group confining unit

EXPLANATION

High: 1,000

Low: 0

Aquifer saturated thickness, 2000, in feet

Deep Fork River

Little River

Cimarron Rive r

Central Oklahoma aquifer from Runkle,

Christenson, and Rea, 1997

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 12. Saturated thickness (2009) in the Central Oklahoma aquifer.
Characteristics of the Central Oklahoma Aquifer 21

others (1996) (fig. 11). The OWRB regulates and permits only 

freshwater that has less than 5,000 mg/L dissolved solids. 

The saturated thickness of the Central Oklahoma aquifer 

in the eastern part of the aquifer in Lincoln and Pottawatomie counties is relatively thin, 200–300 feet, related to the 

thinner geologic units in that area that are caused by the dip 

of the formations and erosion (fig. 12). The thickest zone of 

saturation is about 1,000 feet located near 35°50ʹ latitude and 

97°23ʹ longitude (near Tinker Air Force Base, location shown 

on figure 1) along the extent of the Hennessey Group confining unit that allows freshwater recharge just to the east of the 

Hennessey Group extent and coincides with the deepest part of 

the base of freshwater (fig. 11) and the areas of higher percent 

sand in the aquifer (described in the Hydrogeologic Framework section of this report). The saturated thickness near 

35°50ʹ latitude and 97°05ʹ longitude in another relatively thick 

part of the aquifer in northwest Lincoln County is about 800 ft.

Water-Level Fluctuations

Water-level observations can be used to characterize 

responses of aquifers to different stresses, providing insight 

into hydraulic properties of an aquifer. For example, relatively 

smaller storage capacity of porous media tends to produce 

more water-level fluctuations with higher amplitudes. Conversely, porous media with larger storage capacity produces 

water-level responses with lower amplitudes, assuming similar 

withdrawal rates. Water-level responses also may indicate 

annual trends, seasonal variations, and the relation of groundwater levels to surface-water discharge. Long-term water-level 

data can be used to monitor the effects of regional groundwater supply development and climate variability, changes 

in storage and recharge, and to calibrate groundwater-flow 

models. Responses to precipitation events—or lack thereof—

also help to characterize an aquifer as confined or unconfined 

at different locations and depths.

 Annual water-level measurements available through 

OWRB’s Mass Measurement Program (Oklahoma Water 

Resources Board, 2013) and water-level data from the 

USGS National Water Information System (NWIS) database 

(U.S. Geological Survey, 2010b) were analyzed to determine 

the types of long-term (greater than 10 years) stresses in the 

aquifer (fig. 1). Continuous water-level recorders also were 

installed at 17 sites distributed across the aquifer extent during this aquifer study (2008–11) to characterize the geology, 

examine seasonal variability, and delineate potentially stressed 

areas of the aquifer. Water-level data from the USGS NWIS 

database also were retrieved to examine long-term pumping 

and precipitation trends (U.S. Geological Survey, 2010b). 

One of the greatest water demands during the early use 

of the aquifer was from the Oklahoma City oil field, which 

reached a peak in production during the mid-1930s. Jacobsen 

and Reed (1949) noted that there was 35 feet of drawdown 

during this time and that as oil-field activities decreased during 

the 1940s, recovery of water levels was not observed.

Water-level declines in the Norman area were noted by 

the Bureau of Reclamation (1958), that described how water 

levels were stable from 1947 to mid-year 1951, followed by 

water levels declining by 21–24 feet in several wells from 

mid-year 1951 to 1953. Wood and Burton (1968) noted that 

substantial water-level declines were observed in five wells 

from 1942 to 1963 in the Norman-Midwest City area. The 

hydrographs of those wells showed seasonal water-level 

fluctuations caused by pumping of the aquifer. During summer 

months, water demand typically increases and more water is 

pumped from the aquifer. In one well east of Norman, water 

levels were speculated to have declined from withdrawals 

“required to meet public supply and military demands in the 

Norman area during World War II” (Wood and Burton, 1968). 

Bureau of Reclamation (1958) states “available records 

from observation wells indicate that, since 1947, the static 

water level in the Midwest City-Tinker Air Force Base area 

(see fig. 1 for location) dropped about 50 feet, and in part of 

the Norman area the level has receded about 60 feet.” The 

water-level change in the Midwest City-Del City-Tinker Air 

Force Base area likely was caused by an increase in water 

demand during World War II. Other areas of this aquifer also 

have experienced water-level declines, most notably, the 

Edmond and Nichols Hills (near The Village; fig. 1) areas 

(Carr and Marcher, 1977).

Wickersham (1979) also reported the seasonal production 

pattern in a city of Norman well observed from March 1977 

through March 1978; during this time, water levels were the 

highest in June 1977, lowest in August 1977, and began to 

recover through March 1978. The wells that Wood and Burton 

(1968) monitored did not indicate any measurable response 

to precipitation. Additionally, the authors indicate that water 

levels in the shallow zones were affected by barometric pressure (Wood and Burton, 1968).

Water levels from 37 wells in the Central Oklahoma 

aquifer collected annually as part of the OWRB’s Mass 

Measurement Program were examined for long-term trends. 

Only 18 wells had a period of record of approximately 

10 years to determine long-term trends; 11 of the 18 wells are 

actively measured as part of the Mass Measurement Program 

and 8 wells have a period of record of more than 30 years. 

The hydrographs of some of these wells indicate a possible 

long-term precipitation-related pattern that could be related 

to a historical wet period in Oklahoma from the mid-1980s 

through the early 2000s. Hydrographs from several wells are 

shown in figure 13: OWRB identification numbers 9619 (total 

well depth (TD) = 134 feet), 9622 (TD = 87 feet), and 9624 

(TD = 110 feet). However, these wells do not have a period of 

record long enough to examine water-level trends before that 

wet period.

Well locations in areas of known regulated groundwater 

withdrawals were analyzed to determine how water-level 

trends were affected by localized pumping. Water-level data 

from several wells indicated possible effects from pumping (fig. 14). Examples include the following wells and data: 

OWRB well identification number 9623 (TD = 410 feet) is a 
22 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

90

80

70

80

60

40

20

0

Depth to water, in feet below land surface

1970 1980 1990 2000 2010

Year

72

66

60

54

48

A. Oklahoma Water Resources Board (OWRB) well identifier 9619 

C. OWRB well identifier 9624 

B. OWRB well identifier 9622

Figure 13. Water levels from 

Oklahoma Water Resources 

Board Mass Measurement 

Program wells showing 

possible long-term (greater 

than 10 years) precipitation 

response in the Central 

Oklahoma aquifer area (see 

figure 1 for locations and 

figs. 2 and 3 for long-term 

precipitation graphs).

golf-course irrigation well and has a high water-level variability; OWRB well identification number 9639 (TD = 148 feet) 

is a domestic well at which water levels declined throughout 

the 1980s and 90s; OWRB well identification number 28776 

(TD = 122 feet) is a domestic well at which water levels 

declined throughout the period of record that may be attributed 

to either domestic use, production from new city of Edmond 

water-supply wells beginning in 2006, or a major golf course 

about 1 mile away. 

Long-term continuous and periodic water-level data from 

wells were acquired from the NWIS database (U.S. Geological 

Survey, 2010b) and examined for pumping and precipitation trends; four examples are provided in figure 15. The 

well with the longest-term data, from 1943 to 1989, was 

350816097233101 (TD = 461 feet) with water levels in 

that well cycling between water-level decline and recovery, 

but had no general trend. The most noticeable stress shown 

by these hydrographs is the effect of groundwater pumping at well at sites 352646097231601 (TD = 800 feet) and 

352956097290001 (TD = 791 feet), where cycles of depression and recovery are observed. The data from those two 

sites differ in that water levels in well 352646097231601 
Characteristics of the Central Oklahoma Aquifer 23

gradually declined approximately 75 feet between 1950 and 

1957, whereas water levels in well 352956097290001 had no 

trend or a slight upward trend. Well 352646097231601 is near 

other production wells, indicating that the water-level decline 

in that well could be caused by long-term pumping. Well 

352956097290001 is near a groundwater well permitted for 

irrigation purposes, which probably contributes to the cyclic 

decline and recovery in water levels measured at that well. 

Water levels in USGS well 352449097293201 changed around 

1985, perhaps caused by greater precipitation during that time. 

There is no large-scale groundwater production within several 

miles of the site.

The OWRB installed continuous water-level recorders in 

17 wells during the study, collecting data from 2008 to 2012, 

to identify various stresses affecting water levels (fig. 1). 

Stresses observed included precipitation events, long-term 

precipitation, localized pumping, large-scale pumping, and 

barometric pressure.

Water-level responses from precipitation events were 

observed in six OWRB continuous water-level recorder 

wells: OWRB identification numbers 118584 (TD = 70 feet), 

100

80

60

40

54

48

42

36

1970 1980 1990 2000 2010

Year

120

110

100

90

Depth to water, in feet below land surface

A. Oklahoma Water Resources Board (OWRB) well identifier 9623

B. OWRB well identifier 9639

C. OWRB well identifier 28776

Figure 14. Water levels 

from Oklahoma Water 

Resources Board Mass 

Measurement Program wells 

showing possible response 

from localized groundwater 

pumping in the Central 

Oklahoma aquifer area (see 

figure 1 for locations and 

figs. 2 and 3 for long-term 

precipitation graphs).
24 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

127446 (TD = 183 feet), 127559 (TD = 140 feet), shown on 

figure 16, and 120577 (TD = 50 feet), 122378 (TD = 80 feet), 

and 122695 (TD = 120 feet). Four of those wells were completed in the Chase, Council Grove, and Admire Groups that 

appeared to respond to precipitation events, possibly related 

to lesser cumulative sandstone thickness and small storage in those groups (see OWRB well 118584 in figure 16). 

Water levels in two wells completed in the Garber Sandstone responded to precipitation events: OWRB well 127446 

responded to one precipitation event when more than 5 inches 

fell across the area, which was the largest precipitation event 

during the study; responses to precipitation in water levels in 

well OWRB 127559 were much smaller (fig. 16). 

A multi-year precipitation pattern was observed in nine 

OWRB continuous water-level recorder wells. The general 

pattern observed over the course of the study was measurement of shallower water levels during 2010 and into 2011, 

with deeper water levels measured during the summer and 

fall of 2011 (fig. 16). Water levels that did not have multi-year 

precipitation patterns may not have had a long enough period 

of record or were affected by other stresses, such as large-scale 

groundwater production.

Effects of pumping were observed in three OWRB 

continuous water-level recorder wells as shown by several 

cycles of drawdown and recovery curves in figure 17. One 

well (OWRB well 101448, TD = 460 feet) was about 50 feet 

from a production well with water-level drawdown and 

recovery curves of about 40 feet. The second well (OWRB 

well 109355, TD = 238 feet) was a ‘plugged-back’ oil field 

well and was possibly affected by a nearby (less than 1⁄4 mile 

away) housing addition that was irrigating lawns, with 

drawdown and recovery curves of 2 to 3 feet. The third well 

(OWRB well 129814, TD = 740 feet) was an unused production well near other production wells, with water-level drawdown and recovery curves of 2 to 3 feet. Small-scale pumping 

effects were observed in three additional OWRB continuous 

water-level recorder wells and consisted of small pumping 

cyclic patterns (not shown on figures).

Barometric-pressure change can cause groundwater-level 

fluctuations on daily timescales (Butler and others, 2011; 

Rasmussen and Crawford, 1997; Spane, 2002; and Tanaka 

and Davis, 1963). Wood and Burton (1968) described waterlevel fluctuations caused by barometric-pressure changes in 

the Central Oklahoma aquifer. The premise of this effect is 

EXPLANATION

1940 1950 1960 1970 1980 1990 2000

Year

300

250

200

150

100

Depth to water, in feet below land surface

U.S. Geological Survey well 352449097293201

U.S. Geological Survey well 352646097231601

U.S. Geological Survey well 352956097290001

U.S. Geological Survey well 350816097233101

Figure 15. Water levels from USGS wells showing possible pumping and precipitation responses in the Central Oklahoma aquifer 

area (see figure 1 for locations and figs. 2 and 3 for long-term precipitation graphs).
Characteristics of the Central Oklahoma Aquifer 25

that when barometric pressures increase, groundwater levels 

are suppressed or decline; and when barometric pressures 

decrease, groundwater levels rise.

Data from the water-level recorders were graphed to 

examine the effect of barometric-pressure changes on water 

levels of the Central Oklahoma aquifer. This examination revealed that most of the shallow wells responded to 

barometric-pressure changes. Figure 18 is an example showing water levels at OWRB well 94941 (TD = 160 feet) and 

barometric pressure from the Norman Mesonet Station. At this 

site, increasing barometric pressure decreased water levels 

whereas decreasing pressure was associated with shallower 

water levels, with a time lag between the pressure change and 

the change in water levels.

Water levels in 9 of the 17 wells with continuous waterlevel measurements were affected by barometric-pressure 

changes, water levels in 3 wells were affected by large-scale 

groundwater pumping, water levels in 2 wells appear to have 

OWRB well identifier 127559 

water level—Well completed in Garber Sandstone

Precipitation, Spencer 

Mesonet Station

EXPLANATION

OWRB well identifier 127446 

water level—Well completed in Garber Sandstone

Precipitation, Guthrie 

Mesonet Station

EXPLANATION

Oklahoma Water Resources 

Board (OWRB) well identifier 118584 water level— 

Well completed in Chase, 

Council Grove, and Admire 

Groups

Precipitation, Shawnee 

Mesonet Station

EXPLANATION

30

20

10

0

0

2

4

6

84

80

76

72

68

Depth to water, in feet below land surface

0

2

4

6

Precipitation, in inches

July 2008 January 2009 July 2009 January 2010 July 2010 January 2011 July 2011 January 2012

Date

54

52

50

48

46

0

1

2

3

4

5

Figure 16. Water levels from Oklahoma Water Resources Board continuous recorder wells showing possible long-term precipitation 

response in the Central Oklahoma aquifer area (see figure 1 for locations).
26 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Oklahoma Water Resources 

Board (OWRB) well identifier 101448 water level

EXPLANATION

360

320

280

240

200

80

76

72

Depth to water, in feet below land surface

January 2010 July 2010 January 2011 July 2011

Date

200

180

160

140

120

100

OWRB well identifier 109355 water level

EXPLANATION

OWRB well identifier 129814 water level

EXPLANATION

Figure 17. Water levels from Oklahoma Water Resources Board continuous recorder wells showing possible response 

from localized groundwater pumping in the Central Oklahoma aquifer area (see figure 1 for locations and figs. 2 and 3 for 

long-term precipitation graphs).
Characteristics of the Central Oklahoma Aquifer 27

been more affected by precipitation events than barometric 

changes, and water levels in 3 wells had periods of records for 

which local barometric-pressure data were not available.

The response of water levels in these wells measured for 

this investigation indicated that shallow wells were affected 

by barometric-pressure changes, precipitation, and pumping 

from nearby shallow wells. Water levels in deeper wells in the 

aquifer had minimal response to precipitation and barometricpressure changes, but respond to pumping from nearby deep 

wells. This response indicates there is low vertical hydraulic 

conductivity in this aquifer. The aquifer test, described in the 

Aquifer Hydraulic Properties section and appendix 1 in this 

report, indicated that water levels in shallow wells did not 

respond measurably to pumping from nearby deep wells during the time of the aquifer test. 

Withdrawals for Groundwater Use

The Central Oklahoma aquifer provides water for publicwater supply, irrigation, commercial, industrial, recreation, 

fish, wildlife, and domestic uses. The OWRB regulates the 

use of water from the aquifer with the exception of domestic use, which can be defined as (1) water use of less than 

5 acre-ft/yr for domestic (self-supplied) and agricultural 

purposes, or (2) water use for irrigation on land not exceeding 3 acres. A synopsis of the historical water use before the 

OWRB began keeping records is provided as background 

information about development of the aquifer. Regulated 

water-use data for the investigation described in this report 

were provided by the OWRB and domestic water use was 

estimated using census data. Water-use data for regulated and 

Atmospheric pressure at the Norman 

Mesonet Station

Oklahoma Water Resources Board (OWRB) 

well identifier 94941

EXPLANATION

28

26

24

22

Depth to water, in feet below land surface

28.2

28.6

29

29.4

Atmospheric pressure, in inches of mercury

1/1/2011 2/1/2011 3/1/2011 4/1/2011

Date

Figure 18. Water levels collected with a vented pressure transducer at Oklahoma Water Resources Board well site 94941 and 

atmospheric pressure measured at the Norman Mesonet Station in the Central Oklahoma aquifer.
28 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

domestic categories were incorporated into the groundwaterflow model and were important for quantifying the amount 

of water discharging from the Central Oklahoma aquifer and 

for understanding the effects of water use on the aquifer water 

budget. 

Historical Groundwater Use

Previous publications, such as Jacobsen and Reed 

(1949), Wood and Burton (1968), Mogg and others (1960), 

Benham Engineering Company, Inc. and Black & Veatch 

(1967), Bureau of Reclamation (1958), C.H. Guernsey and Co. 

(1959), and Gould (1905), provide an estimate of groundwater 

development and use from the Central Oklahoma aquifer 

before 1967, when the OWRB began keeping records on water 

use. This historical information can be important to decisionmakers trying to manage this aquifer into the future. Use of 

groundwater from the Central Oklahoma aquifer began in the 

late 1800s during the settlement of the Oklahoma Territory 

(Edmond Historical Society, oral commun., 2009). Early mass 

transportation was achieved by passenger trains running from 

Kansas and Texas into central Oklahoma (Edmond Historical 

Society, oral commun., 2009). Steam engines used during that 

era needed substantial amounts of water at regular distances. 

As a result, many towns, such as Guthrie, Edmond, Oklahoma 

City, Moore (Verbeck), Norman (Norman’s Camp), and Lexington were established along train routes (Edmond Historical 

Society, oral commun., 2009). Groundwater use from early 

statehood is difficult to evaluate because records are sparse or 

were not kept. Historical photographs can give some information about when and where groundwater withdrawal began. 

Photographs from the cities of Edmond (1889) and Moore 

(1900) show groundwater wells; Edmond’s water well was 

hand dug with a diameter of 30 feet, a depth of 128 feet, and 

took 2 years to construct (Edmond Historical Society, oral 

commun., 2009).

Other central Oklahoma communities used groundwater 

as their initial source of water. Britton’s first well was completed in 1900 (Gould, 1905) and Nichols Hills’ first wells 

were drilled in 1938 (Wood and Burton, 1968). In addition, the 

City of Norman holds Oklahoma’s oldest groundwater ‘Prior 

Right’, which was given a priority year of 1894, indicating 

that Norman began using groundwater at that time. Midwest 

City, Del City, and what is now the Tinker Air Force Base 

area, which partly relied on groundwater, developed in the 

early 1940s as a result of war activities (Wood and Burton, 

1968; Jacobsen and Reed, 1949). 

Drought conditions in 1939–40 and again in the 1950s 

forced Oklahoma City, which at the time relied predominantly 

on surface-water sources, to drill groundwater wells to supplement the city’s water supply (Jacobsen and Reed, 1949; Mogg 

and others, 1960; Wood and Burton, 1968). Since that time, 

Oklahoma City has relied increasingly on surface water and 

only maintains a few groundwater wells for possible future 

needs (Benham Engineering Company, Inc., and Black & 

Veatch, 1967).

Some publications attempted to quantify early groundwater use, either from documentation or through estimation. 

Wood and Burton (1968) estimated that 279,000 acre-ft/yr 

were withdrawn from the Central Oklahoma aquifer in 

Cleveland and Oklahoma Counties between 1900 and 1959. 

Bureau of Reclamation (1958) estimated groundwater use 

for the bedrock part of the aquifer (Central Oklahoma aquifer) to have been 13,300 acre-ft/yr in 1953. C.H. Guernsey 

and Co. (1959) estimated use in 1959 for the two-county 

area (Oklahoma and Cleveland Counties) to have been about 

17,900 acre-ft/yr. Much of the water use from 1938–63, 

approximately 40,000 acre-ft/yr, was used for oil field activities (Wood and Burton, 1968) with documented drawdowns 

of 35 feet in the Oklahoma City area (Jacobsen and Reed, 

1949). In 1963, the cities of Edmond, Midwest City, Nichols 

Hills, and Norman, Tinker Air Force Base, and the University 

of Oklahoma reported groundwater use of 14,085 acre-ft/yr 

(Wood and Burton, 1968).

Reported Groundwater Use

Since 1967, users of groundwater that have permits have 

been required to submit their annual water use to the OWRB. 

Groundwater-use data were available from these annual wateruse reports submitted by permit holders to the OWRB and 

typically include public-water suppliers, irrigators, industry, 

and businesses. The term ‘public-water supply’ is used herein 

to describe groundwater use for drinking water by municipalities, rural water districts, housing additions, trailer parks, 

churches, and schools. 

The OWRB reviewed, checked, and corrected 

groundwater-use data to ensure the quality of data included 

in the investigation described in this report. There were 

some cases where a permit holder failed to report water use 

to the OWRB, which are hereby referred to as unreported 

groundwater use. The OWRB attempted to acquire the missing unreported groundwater-use data by either requesting the 

information from the permit holders or retrieving monthly 

operational reports submitted by the municipalities to the 

Oklahoma Department of Environmental Quality. In cases 

where data could not be retrieved, an average of the intervening years for that permit holder was used to estimate the 

missing year’s groundwater-use data, herein referred to as 

estimated unreported groundwater use. 

Groundwater use from the Central Oklahoma aquifer 

bedrock and alluvium from 1967 to 2008, shown in figure 19, 

illustrates that most of the groundwater use was from the bedrock part of the aquifer (Central Oklahoma aquifer). Figure 20 

shows groundwater use, including estimated unreported 

groundwater use, categorized by type: public-water supply, 

irrigation, industrial, power, mining, commercial, recreation, 

and estimated unreported. Average annual reported groundwater use from the aquifer from 1967 to 2008 was about 

34,818 acre-ft/yr. Including estimated unreported groundwater 

use, average groundwater use from 1967 to 2008 was about 

37,367 acre-ft/yr (table 3) with public-water supply consuming 
Characteristics of the Central Oklahoma Aquifer 29

0

20,000

40,000

60,000

1967 1970 1975 1980 1985 1990 1995 2000 2005 2008

Year

Reported and estimated unreported groundwater use in acre-feet per year

Alluvium

EXPLANATION

Bedrock (Central Oklahoma aquifer)

Alluvium estimated unreported 

Bedrock (Central Oklahoma aquifer) estimated unreported 

Figure 19. Groundwater use from alluvium and bedrock sources in the Central Oklahoma aquifer, 1967–2008.

23,367 acre-ft/yr (table 4), or about 63 percent of the average 

annual reported and estimated unreported groundwater use.

Average groundwater use increased steadily from 1967 

through 1976 with an average of 30,148 acre-ft/yr (figs. 19 and 

20). Public-water supply from 1967 through 1976 accounted 

for 52 percent of the reported and estimated groundwater use. 

Commercial use from 1967 through 1976 accounted for about 

23 percent, largely because Tinker Air Force Base reported 

use as such (tables 3 and 4). Groundwater use from the aquifer 

during the 1977–88 period had an average annual reported 

groundwater use of about 40,113 acre-ft/yr. Public-water supply increased by about 55 percent from the 1967–76 period 

and accounted for 24,410 acre-ft/yr of use, or nearly 61 percent of the total use, whereas irrigation use increased by about 

20 percent (tables 3 and 4). The peak groundwater use during 

this period was about 45,346 acre-ft/yr in 1980. Reported 

and estimated groundwater use decreased by 5,044 acre-ft/yr, 

about 13 percent, during the 1989–94 period. This decrease 

in groundwater use may be attributed to a wet period with 

increased rainfall and less reliance on groundwater by the City 

of Edmond because of construction of Lake Arcadia (see fig. 4 

for location) as a water supply. During this 1989–94 period, 

public-water supply use of groundwater decreased by about 

24 percent and unreported use was highest.

During the 1995–2008 period average annual groundwater use increased by about 6,086 acre-ft/yr (17 percent), 

with a peak of annual water use from the aquifer of about 

45,642 acre-ft/yr in 1998. Public-water supply and irrigation 

use increased by about 62 percent and 30 percent, respectively, during the 1995–2008 period. Commercial water 

use decreased because before 1995, Tinker Air Force Base 

reported water use as commercial; afterward, its water use 

was reported as public-water supply. Industrial use decreased 

during each period from an average of 1,875 acre-ft/yr during 

1967–76 to 343 acre-ft/yr during 1995–2008.

During the 1995 to 2008 period, public-water supply was 

the predominant use of groundwater that accounted for about 

73 percent of reported and estimated use (fig. 21). Irrigation 

from 1995 to 2008 accounted for about 10 percent of groundwater use, with about one-half of that use being dedicated 

to golf courses. Other uses from 1995 to 2008 accounted for 

about 10 percent of reported and estimated groundwater use. 
30 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Public water supply

Irrigation

Industrial

Power

Mining

Commercial

Recreation

Estimated unreported 

EXPLANATION

0

20,000

40,000

60,000

Reported and estimated unreported groundwater use, in acre-feet per year

1967 1970 1975 1980 1985 1990 1995 2000 2005 2008

Year

[acre-ft/year, acre-feet per year]

Figure 20. Groundwater use and estimated unreported use by type from the Central Oklahoma aquifer, 1967–2008.

Table 3. Reported and estimated groundwater-use statistics for the Central Oklahoma aquifer, 1967–2008.

Statistic Reported and estimated annual water use (acre-feet per year)

1967–2008 1967–76 1977–88 1989–94 1995–2008

Average 37,367 30,148 40,113 35,069 41,155

Median 37,531 30,442 39,952 35,080 42,411

Minimum 21,576 21,576 37,234 33,542 35,360

Maximum 45,642 36,297 45,346 37,800 45,642
Characteristics of the Central Oklahoma Aquifer 31

Public water supply 

(73 percent)

29,989 acre-ft/year

Irrigation (10 percent)

4,108 acre-ft/year

Estimated

(7 percent)

2,904 acre-ft/year

Power (3 percent)

1,289 acre-ft/year

Commercial 

(3 percent)

1,209 acre-ft/year

Industrial (1 percent)

343 acre-ft/year Mining (2 percent)

738 acre-ft/year

Other (1 percent)

581 acre-ft/year

[acre-ft/year, acre-feet per year]

Figure 21. Average groundwater use by type from the Central 

Oklahoma aquifer, 1995–2008.

Table 4. Average annual reported and estimated groundwater use by type for the Central Oklahoma aquifer, 1967–2008.

[PWS, public water supply]

Time span Average annual reported water use (acre-feet per year)

PWS Irrigation Industrial Power Mining Commercial Other Estimated Total

1967–76 15,727 2,815 1,875 1,620 696 6,888 365 165 30,148

1977–88 24,410 3,369 1,386 863 1,185 6,048 392 2,459 40,113

1989–94 18,564 3,170 720 430 1,681 4,029 599 5,875 35,069

1995–2008 29,989 4,108 343 1,289 738 1,209 581 2,904 41,155

1967–2008 23,367 3,455 1,060 1,123 991 4,347 478 2,549 37,367

From 1995 to 2008, OWRB staff determined that 7 percent, 

or an average annual use of about 2,904 acre-ft/yr, was not 

reported. The years of greatest unreported groundwater were 

from 1988 to 2000, when an estimated average annual use of 

about 6,495 acre-ft/yr was not reported.

The two largest users of groundwater from the Central Oklahoma aquifer from 1995 to 2008 were the cities 

of Edmond and Moore (table 5 and fig. 22). Together, they 

accounted for about 10,780 acre-ft/yr, or about 26 percent of 

the reported and estimated unreported groundwater use. Nine 

of the ten highest users are public water providers; although 

Tinker Air Force Base (see fig. 1 for location) was one of the 

ten highest users, the base also uses water for other purposes. 

The largest users are located over the central part of the aquifer, where the largest deposits of sandstone facilitate larger 

withdrawals of water, described in more detail in the Hydrogeologic Framework section of this report. 

A large portion of the water used from the aquifer serves 

public water-supply systems. Public water providers include 

the cities of Bethany, Del City, Edmond, Midwest City, 

Moore, Mustang, Norman, and Purcell, among others (fig. 22). 

Most of the public water-supply providers rely on the bedrock 

part of the aquifer to supply their needs. The City of Bethany, 

however, relies on water from the alluvium and terrace deposits of the North Canadian River. 

Lake Arcadia (see fig. 6 for lake locations) was constructed in 1986 to augment the City of Edmond’s groundwater demand, which increased during the 1970s and early 

1980s. The rapid decline in groundwater use by Edmond is 

evident by the small consumption in 1989; however, by the 

late 1990s Edmond’s groundwater demand had reached preLake Arcadia demand levels (fig. 23). Similarly, groundwater 

use by local municipalities probably declined after the construction of Lake Hefner (constructed in 1947), Lake Overholser (in 1919), Lake Stanley Draper (in 1962), and Lake Thunderbird (in 1965) (see fig. 6 for lake locations). In addition, the 

City of Oklahoma City currently (2013) sells treated surface 

water to surrounding municipalities. The purchase of treated 

surface water from Oklahoma City allows municipalities to 

pump less groundwater. 
32 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Table 5. Largest users of groundwater from the Central Oklahoma aquifer from 1995 to 2008.

Water user

Reported and estimated annual water use (acre-feet per year)

Reported use Unreported 

(estimated) use

Sum of reported and 

estimated use

Edmond, City of 5,998 0 5,998

Moore, City of 3,237 1,545 4,782

Norman, City of 3,132 207 3,339

Bethany, City of 2,317 429 2,746

Tinker Air Force Base 2,391 143 2,534

Yukon, City of 2,157 0 2,157

Nichols Hills, City of 2,000 0 2,000

Oklahoma Gas & Electric Company 1,284 0 1,284

Mustang, City of 1,107 171 1,278

Purcell, City of 942 0 942

Domestic Groundwater Use

Domestic use from self-supplied wells (does not include 

domestic use from public supply) was estimated for input into 

the groundwater-flow model by using the 1990 census longform (http://www.census.gov/prod/1/90dec/cph4/appdxe.pdf) 

data and compared population changes from 1980, 2000, and 

2010 census data. 

The extrapolation method for estimating domestic 

groundwater use assumes that the population outside of the 

municipal water-supply service areas obtains water from 

domestic wells. The areas of high domestic use identified 

using this method coincide with the number of groundwater 

wells constructed in the Central Oklahoma aquifer. The patterns observed in the estimated domestic groundwater use 

are caused by increasing population in the suburban areas 

surrounding Oklahoma City. Development of water supplies 

east of Norman has continued to increase as well as east of 

Edmond, Oklahoma. Continued development in areas with 

higher domestic use potentially may lead to interferences of 

drawdown between domestic wells.

The census long-form questionnaire is a combination of 

the basic short-form questionnaire plus about 50 additional 

questions on socioeconomic and housing characteristics. The 

long form was distributed to about 15 percent of the population; the data from the long form are weighted to represent an 

estimate of the total population in a particular census tract. 

A census tract is a geographic region defined for the purpose 

of taking a census and usually coincides with city and town 

limits or other administrative areas. The 1990 census longform questionnaire contained a question on source of water, 

whether supplied by municipal or individual well. The 1990 

census long-form questionnaire was the only questionnaire 

that included a question on source of water. There were no 

questions of this nature on the 1980, 2000, or 2010 long-form 

questionnaire. The primary data used from the 1990 census 

to estimate domestic use for this investigation were the total 

population per census tract and the source of water. The 

1990 census data consisted of additional options to designate 

number of housing units served by a public or private water 

supply entity, number of housing units supplied by a drilled 

groundwater well (drilled wells are usually less than 1.5 feet 

in diameter), number of housing units supplied by a dug well 

(dug wells are usually larger than 1.5 feet in diameter and 

hand dug), and number of housing units supplied by other 

sources. For this investigation, the population per census tract 

was divided by the sum of housing units to obtain the number 

of persons per housing unit. The persons per housing unit 

number was multiplied by the sum of housing units supplied 

by a groundwater well and housing units supplied by a dug 

well to obtain the population served by a domestic well. Land 

area for each 1990 census tract was divided into the population 

served by a domestic well for each tract to estimate population served by a domestic well per square mile. The estimated 

1990 population served by a domestic well per square mile 

from census data were distributed across a 3,280-ft by 3,280-ft 

(1-km by 1-km) grid (fig. 24). 

Total population for 1990, 2000, and 2010 was used 

similarly to derive gridded total population datasets. The 

1980 census dataset (U.S. Census Bureau, 2013) was only 

available with county population. The gridded total population datasets were used to calculate a percent change from 

1980–90, 1990–2000, and 2000–10. The 1980–90 (fig. 25) 

and 1990–2000 (fig. 26) population change grids were applied 

to the grid of the 1990 population served by domestic well to 

derive gridded 1980 and 2000 population served by a domestic 
Characteristics of the Central Oklahoma Aquifer 33

Bethany

Del

City

Edmond

Guthrie

Midwest

City

Moore

Mustang

Norman

Oklahoma City

Shawnee

The Village

Yukon

Luther

Tecumseh

Purcell

Arcadia

Jones

Spencer

Choctaw

Nicoma

Park

Eason

0 84 16 MILES

0 84 16 KILOMETERS

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

EXPLANATION

Average annual groundwater use, 

in acre-feet per year

100 to 250

251 to 500

501 to 1,500

1,501 to 3,000

3,001 to 6,000

Extent of Central Oklahoma aquifer

Eastern extent of Hennessey Group 

confining unit

North

Canadian River

Canadian River

Deep Fork River

Little River

Cimarron Rive r

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 22. Average annual reported groundwater use by permitted user greater than 100 acre-feet/year from the Central 

Oklahoma aquifer, 1995–2008.
34 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

0

2,000

4,000

6,000

8,000

Reported and estimated groundwater use, in acre-feet per year 

1967 1970 1975 1980 1985 1990 1995 2000 2005 2008

Year

Lake Arcadia completed

Figure 23. Groundwater use by the City of Edmond from 1967–2008.

well (fig. 27). The 2000–10 population change was applied to 

the 2000 estimated population served by a domestic well grid 

to derive the 2010 population served by a domestic well estimate (fig. 28). This method assumes that the rate of change in 

population changes similarly to the rate of change in population served by domestic wells. 

An understanding of domestic water use from the Central 

Oklahoma aquifer can be obtained by examining domesticuse population density. In 1990, the areas of high domestic 

use based on 1990 census data are as follows: (1) along the 

I-35 corridor (shown on fig. 1) from northeast Oklahoma City, 

Okla. and west of Spencer to the Oklahoma and Logan county 

line, (2) an area north of Edmond, Okla. and south of Guthrie, 

Okla., known as Deer Creek, and (3) east of Oklahoma City 

near Spencer, Nicoma Park, and Choctaw, Okla. (fig. 24). 

Extrapolating to 2000, the estimated population served by 

a domestic groundwater well increased in the area east of 

Edmond, Okla. and to the west of Lake Arcadia, the area of 

southeast Oklahoma County and northeast Cleveland County, 

east of Norman, Okla., south of Moore, Okla., and western 

Logan County (fig. 27). The estimated domestic population 

using water from domestic wells in 2010 continued to increase 

in the area north of Edmond, Okla. and south of Guthrie, Okla. 

as well as southeast Oklahoma County and areas around and 

west of Moore, Okla. (fig. 28).

The grids of population served by domestic wells for 

1980, 1990, 2000, and 2010 needed a per capita daily wateruse rate to determine the domestic-use rate for those years. 

Estimates of per capita daily water use vary substantially. 

Stoner (1984) used 61 gallons per capita per day (gpcd) 

based on several methods, including those of Babbitt and 

Doland (1955) and Steel (1947). Kenny and others (2009) 

report 85 gpcd for Oklahoma based on regional methods to 

determine domestic per capita use rate. They define domestic 

use as including “indoor and outdoor uses at residences...

either self-supplied or provided by public providers.” The 

methods used to derive 85 gpcd were provided by the USGS 

(R.L. Tortorelli, U.S. Geological Survey, written commun., 

2009). The methods for Oklahoma did not distinguish between 

‘self-supplied’ and ‘public-supplied’ as is the case with other 

states (Tortorelli, 2009). Kenny and others (2009) indicate a 

national average for self-supplied and public-supplied use of 

89 gpcd and 99 gpcd, respectively. As a result, applying an allencompassing rate derived for Oklahoma may skew the results 

higher where a ‘self-supplied’ rate may be more realistic for 

domestic use. 
Characteristics of the Central Oklahoma Aquifer 35

Bethany

Del

City

Edmond

Guthrie

Midwest

City

Moore

Mustang

Norman

Oklahoma City

Shawnee

The Village

Yukon

Luther

Tecumseh

Purcell

Arcadia

Jones

Spencer

Choctaw

Nicoma

Park

Eason

0 84 16 MILES

0 84 16 KILOMETERS

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River Deep Fork River

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

EXPLANATION

Population served by a domestic 

well, 1990

0.0 to 2.0

No data or not surveyed

2.1 to 5.0

5.1 to 10.0

10.1 to 15.0

15.1 to 25.0

25.1 to 35.0

35.1 to 50.0

50.1 to 100.0

100.1 to 350.0

Eastern extent of Hennessey 

Group confining unit

Extent of Central Oklahoma 

aquifer

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 24. Population served by domestic wells during the year 1990 (per 3,280-foot by 3,280-foot grid) (U.S. Census Bureau, 

2013).
36 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Bethany

Del

City

Edmond

Guthrie

Midwest

City

Moore

Mustang

Norman

Oklahoma City

Shawnee

The Village

Yukon

Luther

Tecumseh

Purcell

Arcadia

Jones

Spencer

Choctaw

Nicoma

Park

Eason

0 84 16 MILES

0 84 16 KILOMETERS

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

EXPLANATION

Percent change in population, 1980–1990

Eastern extent of Hennessey Group 

confining unit

Extent of Central Oklahoma aquifer

-8.1 to 0.0

0.1 to 5.0

5.1 to 7.5

7.6 to 10.0

10.1 to 15.0

15.1 to 23.6

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Deep Fork River Deep Fork River

Figure 25. Percent change in population from 1980 to 1990 (per 3,280-foot by 3,280-foot grid) (U.S. Census Bureau, 2013). 
Characteristics of the Central Oklahoma Aquifer 37

Bethany

Del

City

Edmond

Guthrie

Midwest

City

Moore

Mustang

Norman

Oklahoma City

Shawnee

The Village

Yukon

Luther

Tecumseh

Purcell

Arcadia

Jones

Spencer

Choctaw

Nicoma

Park

Eason

0 84 16 MILES

0 84 16 KILOMETERS

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

CLEVELAND

COUNTY

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

EXPLANATION

Percent change in population, 

1990–2000

Eastern extent of Hennessey 

Group confining unit

Central Oklahoma aquifer 

extent

-0.73 to -0.50

-0.49 to -0.25

-0.24 to 0.00

0.01 to 0.25

0.26 to 0.50

0.51 to 1.00

1.01 to 60.00

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

OKLAHOMA

COUNTY

Deep Fork River Deep Fork River

Figure 26. Percent change in population from 1990 to 2000 (per 3,280-foot by 3,280-foot grid) (U.S. Census Bureau, 2013).
38 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Bethany

Del

City

Edmond

Guthrie

Midwest

City

Moore

Mustang

Norman

Oklahoma City

Shawnee

The Village

Yukon

Luther

Tecumseh

Purcell

Arcadia

Jones

Spencer

Choctaw

Nicoma

Park

Eason

OKLAHOMA

COUNTY

Deep Fork River Deep Fork River

0 84 16 MILES

0 84 16 KILOMETERS

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

CLEVELAND

COUNTY

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

EXPLANATION

Estimated population served by a 

domestic well, 2000

0.0 to 2.0

2.1 to 5.0

5.1 to 10.0

10.1 to 15.0

15.1 to 25.0

25.1 to 35.0

35.1 to 50.0

50.1 to 100.0

100.1 to 300.0

Eastern extent of Hennessey 

Group confining unit

Extent of Central Oklahoma 

aquifer

44

35

40

40

35

44

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

No data or not surveyed

Base from Horizon Systems Corporation, 2010, 

University of Oklahoma Center for Spatial Analysis, 

2013, and U.S. Census Bureau, 2001

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 27. Estimated population served by domestic wells during the year 2000 (per 3,280-foot by 3,280-foot grid).
Characteristics of the Central Oklahoma Aquifer 39

Bethany

Del

City

Edmond

Guthrie

Midwest

City

Moore

Mustang

Norman

Oklahoma City

Shawnee

The Village

Yukon

Luther

Tecumseh

Purcell

Arcadia

Jones

Spencer

Choctaw

Nicoma

Park

Eason

OKLAHOMA

COUNTY

Deep Fork River Deep Fork River

0 84 16 MILES

0 84 16 KILOMETERS

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

CLEVELAND

COUNTY

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

EXPLANATION

Estimated population served by a 

domestic well, 2010

0.0 to 2.0

2.1 to 5.0

5.1 to 10.0

10.1 to 15.0

15.1 to 25.0

25.1 to 35.0

35.1 to 50.0

50.1 to 100.0

100.1 to 350.0

Eastern extent of Hennessey 

Group confining unit

Extent of Central Oklahoma 

aquifer

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

No data or not surveyed

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 28. Estimated population served by domestic wells during the year 2010 (per 3,280-foot by 3,280-foot grid).
40 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

8,000

12,000

16,000

20,000

1970 1980 1990 2000 2010 2020

Estimated domestic groundwater use, in acre-feet per year

Year

Figure 29. Estimated domestic use derived for the Central Oklahoma aquifer from the 1980, 1990, 2000, and 2010 U.S. Census 

Bureau data.

Table 6. Cumulative population data and estimated domestic water use derived from the 1980, 1990, 2000, and 2010 census for the 

Central Oklahoma aquifer.

[--, not applicable]

Data type 1980 Percent change 

1980–1990 1990 Percent change 1990–2000 2000 Percent change 2000–2010 2010

Total population 793,198 9.77 870,699 12.42 978,852 12.09 1,097,198

Estimated population served 

by a domestic well 112,969 14.06 128,858 18.01 152,063 20.91 183,863

Estimated domestic use 

(acre-feet per year)* 10,756 -- 12,269 -- 14,478 -- 17,506

*Domestic use estimated using 85 gallons per capita per day.

For the Oklahoma Comprehensive Water Plan Report 

on the Central Watershed Planning Region (Oklahoma Water 

Resources Board, 2011), public-water supply entities were surveyed to determine daily per capita water use. In the Central 

Watershed Planning Region, major public water suppliers in 

the Central Oklahoma aquifer reported a range from 50 to 

216 gpcd with an average and median of 121 and 116 gpcd, 

respectively. However, these per capita water uses do not represent domestic residential use because most entities did not 

differentiate between use classes, such as industrial, commercial, and residential uses.

The City of Edmond, Oklahoma provided their water-use 

data from 2006 to 2010 (Fred Rice, City of Edmond, written 

commun., 2011). Categorized data were provided by commercial, industrial, public, and residential meters. Based on 

Edmond’s 2010 population of 81,405, residential daily per 

capita water use in 2010 was 94.7 gallons. The 3-month period 

with the lowest rate was January to March (56.3 gpcd) and 

the highest 3-month water-use period was August to October 

(143.5 gpcd).

Identifying an appropriate daily per-capita water-use 

rate to estimate domestic use is problematic; lower estimates 

tend to be limited to basic everyday residential needs, such as 

personal hygiene and laundry, whereas the larger quantities 
Characteristics of the Central Oklahoma Aquifer 41

reported by water-supply entities commonly include commercial and industrial use, as well as lawn irrigation. The 

estimate of 85 gpcd for Oklahoma (Kenny and others, 2009) 

is similar to the values derived for the City of Edmond and 

Oklahoma Comprehensive Water Plan reported values of 

dominantly rural public water-supply entities, such as the City 

of Harrah, Oklahoma (73 gpcd) (see fig. 1 for town locations) 

and the Town of Jones, Oklahoma (88 gpcd) (Oklahoma Water 

Resources Board, 2011). Therefore, a daily per capita wateruse rate of 85 gallons was multiplied by the grids of population served by domestic wells for 1980, 1990, 2000, and 

2010 to estimate domestic use per 3,280-ft by 3,280-ft (1-km 

by 1-km) grid for the Central Oklahoma aquifer (fig. 29 

and table 6). Average estimated domestic groundwater use 

from the aquifer in 1990 derived from census data was 

12,269 acre-ft/yr. The average domestic groundwater use for 

1980 to 2010 was estimated to be about 13,752 acre-ft/yr.

Streamflow and Base Flow

The major streams flowing across the Central Oklahoma 

aquifer are the Cimarron River, North Canadian River, and 

Canadian River. The flows in these streams are regulated by 

dams and increased by releases from sewage-treatment plants. 

Streamflow data are presented in this section to provide an 

estimate of the streamflow magnitudes in the Central Oklahoma aquifer study area. The streamflow data presented in 

table 7 are summarized through 2009 from the USGS Annual 

Water Data Report (U.S. Geological Survey, 2010a). 

Streamflow at the North Canadian River below Lake 

Overholser near Oklahoma City, Okla., streamflow-gaging 

station 07241000 (fig. 30) is regulated by Canton Lake (not 

shown on figures, outside of map extents), Lake Overholser, 

and flow diversions upstream from the streamflow-gaging 

station into Lake Overholser and Lake Hefner Canal. Days 

with no streamflow were documented at the North Canadian 

River below Lake Overholser near Oklahoma City, Okla., 

streamflow-gaging station during the 1953–55 water years. 

Streamflow at the Canadian River at Bridgeport, Okla., 

streamflow-gaging station (07228500) has been regulated 

upstream by Lake Meredith, Texas since 1964 (not shown on 

figures, outside of map extents). Streamflow at the Deep Fork 

at Warwick, Okla., streamflow-gaging station (07242380) has 

been regulated by Arcadia Lake from 1986 to present (2013). 

Streamflow at the Little River below Lake Thunderbird near 

Norman, Okla., streamflow-gaging station (07230000) has 

been regulated by Lake Thunderbird since 1965. Average daily 

mean streamflow in the study area ranged from 55.8 cubic feet 

per second (ft3/s) at streamflow-gaging station 07230000 for 

the period 1966–2009 to 255 ft3/s at streamflow-gaging station 

07242380 for the period 1988–2009. Total 2009 (water year) 

annual streamflow in the study area ranged from 6.9 million 

acre-ft at streamflow-gaging station 07230000 to 35.5 million 

acre-ft at streamflow-gaging station 07242380.

The part of streamflow that is discharged from groundwater is referred to as base flow. Base flow, for this report, 

is defined as the part of streamflow that is not from runoff. 

Discharge components of the Central Oklahoma aquifer 

consist of evaporation, plant transpiration, groundwater 

withdrawals, and discharge to streams. During the winter 

months, evaporation, plant transpiration and withdrawals from 

the shallow part of the aquifer (most regulated withdrawals 

are from the deeper parts of the aquifer) are considered to be 

minimal and discharge measurements were made when the 

runoff part of streamflow was considered to have dissipated. 

Discharge measurements made in unregulated streams during 

these conditions also are referred to as base flow, in which the 

entire flow in the stream channel is inferred to be groundwater 

discharge (table 8). Discharges measured in January 2009 

in the study area during base-flow conditions ranged from 

0.23 ft3/s at streamflow-gaging station 07241570 Deer Creek 

near Newalla, Okla., to 4.46 ft3/s at streamflow-gaging station 

07242378 Captain Creek near Wellston, Okla. Base flow is 

the largest water discharge by the Central Oklahoma aquifer 

(Parkhurst and others, 1996). 

Recharge

Recharge, for the investigation described in this report, is 

the process by which precipitation enters the groundwater-flow 

system at the upper zone of saturation. Recharge in the Central 

Oklahoma aquifer can be inferred to exist from two main 

processes: (1) infiltration of streamflow through stream channels and lake beds, and (2) infiltration of precipitation through 

the unsaturated zone above the aquifer. Factors that affect 

recharge are precipitation rates and amounts, vertical hydraulic 

conductivity, moisture capacity of the unsaturated zone, and 

slope of the land surface. Recharge is difficult to quantify and 

measure directly because recharge rates vary over short spatial 

and temporal scales, but there are several methods that can 

be used to estimate recharge rates. Some methods attempt to 

capture recharge rates at specified points and some methods 

estimate recharge at the basin or regional scale. Either of these 

types of methods can vary in timescale from hours to days.

In many drainage basins a substantial proportion of 

base flow began as groundwater recharge. Using base flow 

to estimate recharge requires several assumptions. First, base 

flow to a stream is assumed to be derived from the areally 

distributed recharge over the area of the basin and not from 

the regional flow system. Second, minimal water consumption and discharge is assumed, such as plant evapotranspiration or pumping wells in a basin. Lastly, recharge entering the 

saturated zone of the aquifer is assumed to discharge to the 

stream as base flow and does not leave the basin as part of the 

regional flow system. This method does not work well for losing streams, but the streams overlying the Central Oklahoma 

aquifer are assumed to be mostly gaining streams. Water lost 

to, or gained from these other sources is assumed to be less 
42 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma Table 7. Streamflows at USGS streamflow-gaging stations in the vicinity of the Central Oklahoma aquifer summarized through 2009. [--, not determined] Streamflow-gaging station Contributing/ noncontributing drainage area, in square miles Period summarized Flow regulated Average daily mean streamflow, in cubic feet per second Month that highest daily mean streamflow typically occurs Month that lowest daily mean streamflow typically occurs Water year 2009 total annual streamflow, in acre-feet Water year 2009 average daily mean streamflow, in cubic feet per second 07159100 Cimarron River near Dover, Okla. 15,713/4,926 1974–2009 No 881 May January 143,022,000 541 07241000 North Canadian River below Lake Over- holser near Oklahoma City, Okla. 13,222/4,899 1953–2009 Yes 187 June September* 26,744,700 101 07228500 Canadian River at Bridgeport, Okla. 25,276/4,801 1945–64 No 469 -- -- -- -- 07228500 Canadian River at Bridgeport, Okla. 25,276/4,801 1970–2009 Yes 318 May July 70,516,200 267 07242380 Deep Fork at Warwick, Okla. 532/0 1988–2009 Yes 255 June October 35,550,000 138 07230000 Little River below Lake Thunderbird near Norman, Okla. 257/0 1953–64 No 58.9 -- -- -- -- 07230000 Little River below Lake Thunderbird near Norman, Okla. 257/0 1966–2009 Yes 55.8 June September 6,882,720 26 *Days with no streamflow documented during water years 1953–55.
Characteristics of the Central Oklahoma Aquifer 43

1,100

1,050

950

900

1,100

1,150

1,050

950

900

1,000

1,250

1,200

1,050

1,000

1,150

1,100

950

1,050

950

1,000

1,100

950

1,100

1,250

1,200

900

1,150

1,000

1,300

950

1,100

950

850

1,000

1,250

950

1,100

1,000

1,000

850

1,100

1,050

950

950

900

1,100

1,050

1,000

950

1,050

1,000

1,100

1,100

0 84 16 MILES

0 84 16 KILOMETERS

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Potentiometric contours from Christenson and

others, 1992

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

COUNTY

POTTAWATOMIE

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Extent of Central Oklahoma aquifer

Eastern extent of Hennessey Group 

confining unit

Potentiometric contour—Shows altitude 

at which water level would have 

stood in tightly cased wells, 1986–87. 

Contour interval 50 feet

Groundwater-basin boundary (derived 

using potentiometric contours)

Streamflow-gaging station and identifier

EXPLANATION

1,100

Deep Fork at Warwick

Deep Fork near Arcadia

Little River near Tecumseh

Surface-water basins

07159400

07161450

07228940

07229325

07229365

07229422

07230000

07230200

07230205

07230500

07230725

07241000

07241570

07241580

07242350

07242371 07242378

07242380

07242530

07229325

07230302

Deep Fork River

Little River

Cimarron Rive r

North

Canadian

River

Canadian River

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 30. U.S. Geological Survey streamflow-gaging stations and selected surface-water basins and groundwater basins in 

the Central Oklahoma aquifer.
44 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Table 8. Streamflow measurements (at base flow) and calculated recharge rates from small selected streams located near the Central 

Oklahoma aquifer.

[--, recharge rate not calculated]

Station 

number Station name Drainage area (square miles) Date measured Discharge (cubic feet per second)

Recharge rate 

(inches per year)

07229325 Buckhead Creek near Lexington, 

Okla.

19.2 1987-12-10 1.77 1.25

1988-02-25 4.48 3.17

1988-09-01 0.395 --

1988-12-05 0.74 0.52

1989-03-16 2.78 1.97

2009-01-07 0.83 0.59

07229365 Pond Creek near Eason, Okla. 27.6 1987-12-10 2.05 1.01

1988-02-25 4.14 2.04

1988-09-01 0.145 --

1988-12-05 0.72 0.35

1989-03-16 0.389 0.19

2009-01-07 0.51 0.25

07230200 Pecan Creek near Stella, Okla. 15.5 1987-12-10 1.15 1.01

1988-02-25 2.55 2.23

1988-09-01 0 --

2009-01-07 0.92 0.81

07230205 Pecan Creek near Pink, Okla. 37.4 1987-12-10 3.17 1.15

1988-02-25 5.6 2.03

1988-09-01 0.389 --

1988-12-05 1.86 0.68

1989-03-16 5.78 2.10

2009-01-06 3.18 1.15

07230302 Jim Creek near Morvin, Okla. 11.2 1987-12-10 1.11 1.35

1988-02-25 1.81 2.20

1988-09-01 0.181 --

1988-12-05 0.67 0.81

1989-03-16 2.09 2.53

2009-01-05 1.14 1.38

07230725 Salt Creek near Remus, Okla. 101.88 2009-01-07 1.81 0.24

07241570 Deer Creek near Newalla, Okla. 15.3 1987-12-10 0.222 0.20

1988-02-25 1.36 1.21

1988-09-01 0 --

2009-01-06 0.23 0.20
Characteristics of the Central Oklahoma Aquifer 45

Table 8. Streamflow measurements (at base flow) and calculated recharge rates from small selected streams located near the Central 

Oklahoma aquifer.—Continued

[--, recharge rate not calculated]

Station 

number Station name Drainage area (square miles) Date measured Discharge (cubic feet per second)

Recharge rate 

(inches per year)

07241580 Unnamed tributary to Deer Creek 

near Newalla, Okla.

8.7 1987-12-10 0.163 0.25

1988-02-25 0.6 0.94

1988-09-01 0 --

2009-01-06 0.54 0.84

07242371 Wildhorse Creek at Luther, Okla. 18.2 1987-12-10 3.07 2.29

1988-02-25 4.06 3.03

1988-09-01 0.86 --

1988-12-05 2.89 2.16

1989-03-16 3.82 2.85

2009-01-06 2.7 2.02

07242378 Captain Creek near Wellston, Okla. 57.9 1987-12-10 7.09 1.66

1988-02-25 10.9 2.56

1988-09-01 1.13 --

1988-12-05 6.11 1.43

1989-03-16 11.4 2.67

2009-01-06 4.46 1.05

than the total recharge-base-flow relation, and thus the base 

flow is an approximation of surface recharge. 

Several basin-scale methods were used to quantify average annual recharge rates (that is, the quantity of recharge 

per unit of time) for surface-water basins in the study area. 

Recharge rates were estimated by using base-flow-discharge 

measurements (Szilagyi and others, 2003; Risser and others, 

2005) and using a recession-curve displacement method (Rutledge, 1998; Rorabaugh, 1964). The recession-curve displacement method provides estimates of recharge through multiple 

years for the period of record of streamflow analyzed, whereas 

the base-flow-discharge measurements provide an estimate of 

recharge each year that the stream was measured. In addition, 

recharge was calculated for the study area using the SoilWater Balance code (Westenbroek and others, 2010) that uses 

climate data with soil and land-use data to provide a spatial 

distribution of recharge.

Recharge from Base-Flow Discharge

Recharge estimated from base-flow-discharge measurements requires a number of simplifications and assumptions 

that likely are not met under actual conditions, but base-flowdischarge measurements provide a simple estimate of recharge 

accurate to an order of magnitude of actual amounts (Rutledge, 1998; Rorabaugh, 1964). Calculation of recharge from 

base-flow measurements assumes that an aquifer is in steadystate condition, for which discharge is equal to recharge. Base 

flow was measured during January 2009 at nine of the original 

sites used for the 1987–89 base-flow measurements reported 

in Parkhurst and others (1996; table 8). Six additional stream 

sites were selected for measuring streamflow during baseflow conditions for the investigation described in this report. 

Recharge rates were calculated from the base-flow measurements by dividing the discharge by the area of the drainage 

basin, which assumes that the area contributing groundwater 

to the stream is equal to the area of the drainage basin, and that 

all areas in the drainage basin are recharged at the same rate. 

Table 8 shows measured discharge at those streamflow sites 

and calculated recharge for the upstream drainage basins for 

each measurement date. 

Streams ideal for recharge-estimation measurements are 

streams that contain drainage basins completely in the aquifer, 

are not regulated, and do not have withdrawals of surface 

water, discharges from sewage-treatment plants, or substantial groundwater withdrawals in the drainage basin. The 

larger streams within the boundaries of the Central Oklahoma 

aquifer flow through a highly urbanized area. Therefore, most 

of these streams are regulated or have discharges or withdrawals, so they were not used for the recharge analysis. Recharge 

rates estimated from the 1987–89 streamflow measurements 

ranged from 0.19 inches per year at the Pond Creek near 
46 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Eason, Okla., streamflow-gaging station to 3.17 inches per 

year at the Buckhead Creek near Lexington, Okla., streamflow-gaging station. Recharge rates calculated for the 2009 

measurements ranged from 0.20 inches per year at the Deer 

Creek near Newalla, Okla., streamflow-gaging station to 

2.02 inches per year at the Wildhorse Creek at Luther, Okla., 

streamflow-gaging station. Recharge rates calculated from the 

streamflow measurements in 2009 are similar to recharge rates 

calculated from the 1987–89 streamflow measurements (table 

8). The streams listed in table 8 have basins completely in the 

aquifer, were not regulated for the period analyzed, and do not 

have substantial withdrawals and discharges in the streams or 

aquifer during the period analyzed.

Recharge from Rorabaugh Method

Another method used to estimate basin-scale recharge for 

this investigation was a recession-curve displacement method, 

developed by Rorabaugh (1964). As stated by Rutledge 

(1998), the Rorabaugh method is based on the measurement 

of the change in the total potential groundwater discharge as 

estimated at the critical time after a discharge peak by extrapolation from the pre-peak and the post-peak recession periods. 

The Rorabaugh method produces a recharge rate expressed 

as inches per year for the subsurface drainage basin, which 

is often assumed to be the surface-water drainage basin area. 

After analysis of the potentiometric-surface maps in the study 

area, the groundwater-drainage basin areas appeared to be 

different sizes than the surface water drainage basin areas 

(fig. 30). Therefore, the groundwater drainage basin areas 

were used in the Rorabaugh method for this investigation. The 

groundwater drainage basin areas were derived by using the 

2009 potentiometric-surface contours and assuming that little 

to no areal recharge enters the aquifer where the Hennessey 

Group confining unit overlies the aquifer. A series of computer programs by Rutledge (1998) were used to analyze daily 

stream-discharge data for three streamflow-gaging stations on 

the Central Oklahoma aquifer. The Deep Fork near Arcadia, 

Okla., (07242350) (fig. 31), Little River near Tecumseh, 

Okla., (07230500) (fig. 32), and Deep Fork at Warwick, Okla., 

(07242380) streamflow-gaging stations discharge data were 

analyzed using the Rorabaugh method to determine annual 

recharge rates for the groundwater drainage basins upstream 

from each streamgage. 

Streamflow data were collected at the Deep Fork near 

Arcadia, Okla., streamflow-gaging station for an unregulated 

period before the construction of Arcadia Lake Dam. Therefore, estimates of recharge were determined for the period 

1969 to 1983, resulting in an average annual recharge rate of 

4.1 inches per year (fig. 31). The groundwater drainage basin 

area above the Deep Fork near Arcadia, Okla., streamflowgaging station is estimated to be 122 square miles (fig. 30). 

Monthly precipitation data were retrieved from the National 

Climatic Data Center website (National Climatic Data Center, 

2010) for the nearest COOP station, Guthrie 5S (station number 3821) and the average for each quarter for comparison to 

the Deep Fork quarterly recharge. COOP stations are further 

described in the Climate section of this report. The stations 

used for the recharge analysis were not the same stations used 

for the climate summary because of the variations in periods 

of record. The average annual recharge rate also was estimated 

from the Deep Fork at Warwick, Okla., streamflow-gaging 

station data to be 3.5 inches per year, but was estimated for 

just a few years (1984 and 1985) for the unregulated period 

before construction of the Arcadia Lake Dam. The groundwater drainage basin area above the Deep Fork at Warwick, Okla., streamflow-gaging station was estimated to be 

562 square miles. Streamflow data were collected at the Little 

River near Tecumseh, Okla., streamflow-gaging station with 

data from 1943 to 1961 being suitable for recharge analysis, 

producing an average annual recharge rate of 1.3 inches per 

year (fig. 32). The groundwater drainage basin area above the 

Little River near Tecumseh, Okla., streamflow-gaging station 

is 428 square miles (fig. 30). Monthly precipitation data also 

were retrieved for the nearest COOP station, Meeker (station 

number 5779) (not shown on figures, outside of map extents) 

and the average for each quarter for comparison to the Little 

River quarterly recharge. 

Recharge rates calculated using the Rorabaugh method 

varied from 1.3 inches per year for the Little River near 

Tecumseh, Okla., streamflow-gaging station to 4.1 inches per 

year for the Deep Fork near Arcadia, Okla., streamflow-gaging 

station. A possible reason for this variation could be from different amounts of precipitation, but precipitation is similar for 

the periods analyzed for each station (figs. 31 and 32). Other 

reasons for the difference in recharge could be (1) errors in 

determining the size of the groundwater basin, and (2) differences in runoff between the two watersheds, likely caused 

by factors such as differences in paved area, slope, and clay 

content of the soil. The Deep Fork near Arcadia, Okla., and 

Deep Fork at Warwick, Okla., groundwater drainage basins 

extend south of the surface-water drainage basins and include 

recharge from the potentiometric high located near 35°23ʹ 

latitude and 97°23ʹ longitude and from part of the North Canadian River alluvium and terrace deposits (figs. 4 and 30). The 

recharge values calculated from the Rorabaugh method compare favorably with results from the previous investigation by 

Parkhurst and others (1996) that describe groundwater flowing 

under nearby streams to discharge primarily to the Deep Fork 

River. In addition, the Little River near Tecumseh, Okla., 

groundwater-drainage basin is located in a part of the aquifer 

that contains a lesser percent sand and lesser thickness than the 

part of the aquifer where the Deep Fork near Arcadia, Okla., 

and Deep Fork near Warwick, Okla., groundwater-drainage 

basins are located (further described in the Hydrogeologic 

Framework section of this report). The lesser percent sand 

and thickness of the aquifer in the Little River near Tecumseh, 

Okla., groundwater basin might have a smaller hydraulic conductivity and transmissivity and impede precipitation recharge 

to the aquifer in that area.
Characteristics of the Central Oklahoma Aquifer 47

0.1

1

10

100

1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983

Average annual recharge = 4.1 inches per year

 Quarterly recharge and precipitation, in inches per quarter

Year

EXPLANATION

Precipitation at Guthrie, Oklahoma (cooperative observer 

station, National Weather Service, 2011)

Estimated recharge

Figure 31. Graph showing estimated quarterly recharge rates and average annual recharge rate using the Rorabaugh method for the 

Deep Fork River near Arcadia, Oklahoma basin for the period 1969 to 1983.

0.01

1

10

100

1943 1944 1945 1946 1947 1948 1949 1950 1953 1954 1957 1958 1959 1960 1961

Average annual recharge = 1.3 inches per year

EXPLANATION

Precipitation at Meeker, Oklahoma (cooperative observer 

station, National Weather Service, 2011)

Estimated recharge

Quarterly recharge and precipitation, in inches per quarter

Year

0.1

1951 1952 1955 1956

Figure 32. Graph showing estimated quarterly recharge rates and average annual recharge rate using the Rorabaugh method for the 

Little River near Tecumseh, Oklahoma basin for the period 1943 to 1961.
48 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Recharge Calculated Using the Soil-Water 

Balance Code

The Soil-Water Balance (SWB) code (Westenbroek and 

others, 2010) uses climate data with soil and land-use data 

to estimate spatial distribution of recharge. Recharge was 

estimated on a regional scale using the SWB code developed 

by Westenbroek and others (2010). The SWB code calculates 

potential recharge as water that is surplus in the soil profile, 

which is the amount of precipitation infiltration that exceeds 

the storage capacity of the soil in the root zone and the 

demand from plants for evapotranspiration (ET). ET is calculated using the Hargreaves-Samani method (Hargreaves and 

Samani, 1985) using latitude and daily high and low temperatures. Soil properties also are used to estimate how much of 

the daily precipitation enters the soil profile and how much of 

the daily precipitation runs off. Land-cover properties (MultiResolution Land Characteristics Consortium, 2001) are used 

in the SWB to specify interception by plants and runoff curve 

numbers. SWB analysis increased soil moisture during growing seasons for cells that were coded as irrigated agriculture in 

the land-use data set to simulate the effects of irrigation. The 

analysis did not route irrigation runoff or track deep percolation from inefficient irrigation application methods. 

Soil properties were derived from the General Soil Map 

(STATSGO2; Natural Resources Conservation Service, 2006). 

Digital-elevation models were analyzed to determine the 

surface-water-flow direction for each grid cell, as described 

in Westenbroek and others (2010). These physical grids were 

assumed to remain constant during the model time period. The 

grid-cell size used for the SWB code was 3,280 by 3,280 feet 

(1 km by 1 km). Daily climate data included grids of precipitation, high temperature, and low temperature. Precipitation and 

temperature data were interpolated across the study area from 

National Weather Service weather stations (National Climatic 

Data Center, 2010), and after 1994 data from the Oklahoma 

Mesonet weather network (Oklahoma Climatological Survey, 

2011c) were included (fig. 1). 

Results of the SWB model analysis were total annual 

recharge grids that were time-averaged to average daily 

values at each grid cell for use in the groundwater-flow model 

(fig. 33). Average annual recharge for the gridded aquifer area 

for 1987 was 3.4 inches per year. Average annual recharge 

for the gridded aquifer area for the 1987–2009 period was 

4.6 inches, which was similar to the recharge rate calculated 

for the Deep Fork River using the Rorabaugh method. The 

minimum average annual recharge for the gridded aquifer area 

for the 1987–2009 period was 1.9 inches per year in 2006. The 

maximum average annual recharge for the gridded aquifer area 

for the 1987–2009 period was 8.5 inches per year during the 

year 2007. However, during model calibration (see Calibration 

Process sections) a scaling factor of 0.4 was applied to SWB 

recharge, which resulted in minimum and maximum values of 

0.76 inches per year in 2006 and 3.4 inches per year in 2007, 

respectively. Average annual recharge values for the gridded 

aquifer area for the 1987–2009 period with a scaling factor of 

0.4 applied, was 1.84 inches per year. Maximum values were 

calculated at focused recharge locations where surface water is 

concentrated by runoff to areas of lower altitudes.

Because SWB estimates deep percolation that may or 

may not contribute to the groundwater system, this model 

can overestimate recharge. Another limitation of the SWB 

code is that does not consider plant uptake from groundwater 

where the water table could be in the root zone for part or all 

of the year. The spatial distribution of recharge provided by 

SWB has, however, been shown to be an effective starting 

point for groundwater-flow model calibration (Stanton and 

others, 2012).

Aquifer Hydraulic Properties

Hydraulic properties refer to characteristics that affect 

groundwater flow through and storage of water in an aquifer. For this study, the principle hydraulic properties used to 

describe the Central Oklahoma aquifer were hydraulic conductivity, vertical anisotropy, transmissivity, and confined and 

unconfined storage coefficients. Hydraulic conductivity of the 

aquifer under isotropic conditions is defined as “the volume of 

water at the existing kinematic viscosity that will move in unit 

time under a unit hydraulic gradient through a unit area...” 

(Lohman, 1972). Hydraulic conductivity is expressed in units 

of length per time (feet per day in this report). Transmissivity 

is the rate that water is “transmitted through a unit width of 

the aquifer under a unit hydraulic gradient” (Lohman, 1972). 

Transmissivity is expressed in terms of length squared per 

time (square feet per day in this report).

A storage coefficient is the volume of water an aquifer 

releases from or takes into storage per unit surface area of the 

aquifer per unit change in head (Lohman, 1972), and is dimensionless. Storage of water in the Central Oklahoma aquifer is 

released under confined (storage coefficient) and unconfined 

(specific yield) conditions. Storage in confined aquifers is 

affected by additional stresses caused by the overburden of 

overlying rock and water. Water is released from storage in 

confined aquifers caused by the compressibility of the water 

and the aquifer matrix. Although the water is released from 

storage, the aquifer remains saturated. Water is released from 

storage in an unconfined aquifer as water drains from pore 

spaces, which is defined as specific yield.

The most difficult hydraulic property of the Central 

Oklahoma aquifer to quantify is anisotropy, which is the ratio 

of horizontal hydraulic conductivity to vertical hydraulic 

conductivity. Anisotropy has not been directly measured or 

estimated in the Central Oklahoma aquifer and that characterization was beyond the scope of this investigation. Estimations and assumptions used to characterize the vertical flow of 

water through the Central Oklahoma aquifer are described in 

the Groundwater-Flow Model Hydraulic Properties section of 

this report.

Aquifer hydraulic properties were compiled from previous publications about the aquifer, estimated from lithologic 
Characteristics of the Central Oklahoma Aquifer 49

0 84 16 MILES

0 84 16 KILOMETERS

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

EXPLANATION

0.000 to 0.002

Eastern extent of Hennessey 

Group confining unit

Extent of Central Oklahoma 

aquifer

0.003 to 0.005

0.006 to 0.009

0.010 to 0.011

0.012 to 0.014

0.015 to 0.016

0.017 to 0.019

0.020 to 0.026

0.027 to 0.040

0.041 to 0.065

Mean recharge, 1987–2009, in inches per 

day—Recharge for the groundwaterflow model was set to 0.4 times 

Soil-Water Balance recharge (see 

discussion in Groundwater-Flow 

Model section)

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 33. Average annual recharge calculated using the Soil-Water-Balance code (Westenbroek and others, 2010) for the 

Central Oklahoma aquifer for the period 1987–2009 in 3,280-ft by 3,280-ft grid cells.
50 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

and geophysical well logs, and calculated from a multiplewell aquifer test. Parkhurst and others (1996) reported 

geohydrologic-unit hydraulic conductivity for wells deeper 

than 500 feet in this aquifer of 0.30 to 7.1 feet per day, with a 

median of 1.5 feet per day. Gates and others (1983) compiled 

hydraulic data from existing aquifer tests and conducted additional aquifer tests as part of their study. Transmissivity values 

in their report ranged from 20 to 900 square feet per day, with 

a median of 400 square feet per day. Storage coefficient values 

were determined for several of the aquifer tests and ranged 

from 0.0001 to 0.0003. These small storage coefficients indicate that, even though the Central Oklahoma aquifer extends 

to land surface with a potentiometric surface below the top of 

the Central Oklahoma aquifer, the groundwater system acts as 

a confined system.

Previously published hydraulic conductivities of the 

Hennessey Group, which acts as an upper confining unit to the 

Central Oklahoma aquifer, derived from permeameter testing 

ranged from 1.1 x 10-6 to 1.1 x 10-4 ft/d, and derived from slug 

testing ranged from 8.5 x 10-8 to 3.1 x 10-4 ft/d (Becker and 

others, 1997). Wood and Burton (1968) completed six aquifer 

tests in the Central Oklahoma aquifer. Three aquifer tests completed near the University of Oklahoma determined transmissivity to be 400 to 700 square feet per day and that storage 

coefficients ranged from 0.0001 to 0.0003 (Wood and Burton, 

1968). An aquifer test completed in Midwest City, Okla., 

produced a transmissivity of 700 square feet per day and a 

storage coefficient of 0.0003, an aquifer test completed in 

Edmond, Okla., produced a transmissivity of 900 square feet 

per day and a storage coefficient of 0.0002, and an aquifer test 

completed in Nichols Hills, Okla. (near The Village; fig. 1), 

produced a transmissivity of 500 square feet per day and a 

storage coefficient of 0.0001 (Wood and Burton, 1968). Wood 

and Burton (1968) used the Theis (1935) nonequilibrium 

formula to analyze the aquifer tests, which assumes the aquifer 

is unconfined. Storage coefficients determined using the 

nonequilibrium formula do not account for water derived from 

low-permeability geologic units (such as the mudstones in the 

Central Oklahoma aquifer) and are likely to be less accurate 

for this aquifer but are included here for completeness. 

Wood and Burton (1968) suggested that the variability in the thickness of individual sandstone beds over short 

distances will cause the hydraulic properties and connectivity 

between wells to vary over short distances. They noted during 

the aquifer tests in Nichols Hills that water levels in two deep 

wells located 0.5 mile away from the pumping well decreased 

by about 10 feet, whereas water levels in three nearby shallow 

wells fluctuated slightly (less than a foot of change). 

Norman Aquifer Test

A multiple-well aquifer test was completed at a production well near Norman, Okla., (fig. 1) as part of this investigation to determine a transmissivity, hydraulic conductivity, and 

storage coefficient for the Central Oklahoma aquifer. Details 

and analyses of this aquifer test are provided in appendix 1. 

Transmissivity determined from the analytical solution was 

220 square feet per day. Using the screened interval of 90 feet 

in the production well, the geohydrologic-unit hydraulic conductivity was 2.4 feet per day. The average percent sand of the 

Central Oklahoma aquifer at that location was approximately 

70 percent (further described in the Hydrogeologic Framework section of this report). The analytical-model solutions 

indicated a leaky confined aquifer. The storage coefficient 

from the analytical solution was 0.0013, which is an order of 

magnitude higher than previously published storage coefficients for this aquifer (Wood and Burton, 1968; Gates and 

others, 1983). Storage coefficients reported in previous publications (Wood and Burton, 1968; Gates and others, 1983), 

using the nonequilibrium formula, do not account for water 

derived from low-permeability geologic units (such as the 

mudstones in the Central Oklahoma aquifer) and are likely to 

be underestimated. The transmissivity, hydraulic conductivity, 

and storage coefficient derived from the aquifer test done for 

this investigation are likely to be more accurate than hydraulic 

values derived using other methods, such as from grain size 

or laboratory tests of aquifer material. However, these hydraulic values represent local conditions and are not necessarily 

indicative of the hydraulic property values of larger areas. 

For example, if an aquifer test was completed in Edmond, 

Okla., the transmissivity and storage coefficient would likely 

be different than the test completed in Norman, Okla., and the 

aquifer at both sites may respond differently to the withdrawal. 

The hydraulic conductivity at this Norman, Okla., location was expected to be somewhat larger than the hydraulic 

conductivity measured at a site in the aquifer that contains less 

sandstone and more mudstone.

Hydrogeologic Framework

A hydrogeologic framework of the Central Oklahoma 

aquifer was developed to describe the lithology of the Central Oklahoma aquifer, including sandstones, siltstones, and 

mudstones. The objective of developing the hydrogeologic 

framework was to provide a three-dimensional representation 

of the lithologic variability of aquifer materials at a scale that 

captured the regional controls on groundwater flow for construction of the groundwater-flow model. The distribution and 

variability of mudstones interbedded with sandstones and siltstones were considered to be the major control on groundwater 

flow in the aquifer as there were no known major structural 

or karst features in the aquifer that might substantially affect 

groundwater flow. 

Percent Sand Data Sources and Standardization 

Methods

Lithologic and gamma-ray borehole logs, in conjunction with aquifer-test data, were used to develop the hydrogeologic framework. Lithologic logs and gamma-ray logs 
Hydrogeologic Framework 51

were converted to percent sand, which was used as a proxy to 

estimate initial hydraulic conductivity of the aquifer for the 

groundwater-flow model. An inventory of the available log 

data showed that neither lithologic nor gamma-ray borehole 

logs provided complete quality, depth, and geographic coverage of aquifer properties alone. However, a combination of 

these datasets provided adequate coverage to construct a threedimensional representation of percent sand in the aquifer.

Lithologic Logs

Available lithologic logs of varying depth, submitted to 

the OWRB by well drillers included descriptions of cuttings 

that were recorded as water-well boreholes were drilled. In the 

State of Oklahoma, there are no specified standards for lithologic descriptions by well drillers, leading to varying descriptions between drilling companies and individual well loggers. 

The OWRB provided the USGS with copies of lithologic 

logs for the Central Oklahoma aquifer. These data are stored 

in the OWRB water-well records database (Oklahoma Water 

Resources Board, 2013). 

Most lithologic logs include, at a minimum, categories 

for sandstone (often called sandrock) and mudstone (often 

called mudrock). Many drillers’ logs also contain intermediate 

lithologies, though the names used for these categories vary 

widely. To simplify and standardize the lithologic logs, the 

lithologic descriptions were reclassified into four categories 

that were used to estimate the percent sand of each depth interval. Lithology was categorized into mud, sandy mud, muddy 

sand, and sand, which can be conceptually simplified and 

quantified as a continuous series of textures from 0 percent 

sand (mudstone) to 100 percent sand (sandstone).

To estimate a percent sand from a lithologic log, each 

lithologic category was assigned a percent sand using a 

multiplier. For example, the sand category was assigned a bin 

percent sand range of 100 to 75 percent sand and a midpoint 

of 87.5 percent sand. The midpoint of each bin was used as 

a percent-sand multiplier to convert each lithologic category 

to a numeric value because the multiplier was a mean percent 

sand for each bin (fig. 34). The sand multiplier was 87.5 percent sand, the muddy sand multiplier was 62.5 percent sand, 

the sandy mud multiplier was 37.5 percent sand, and the 

mud multiplier was 12.5 percent sand. The percent sand was 

summarized into a total percent sand for each lithologic log 

using a weighted average of the length of the log. The maximum percent sand for any log was 87.5 and the minimum 

percent sand for any log was 12.5. These percent-sand ranges 

were consistent with the 16 to 88 percent sand described by 

Schlottman and others (1998) for rocks in the Central Oklahoma aquifer. Lithologic logs were categorical and of irregular 

frequency with depth. Therefore, summarizing percent sand 

for regular depth intervals (layers) using an automated process 

was not feasible.

Approximately 11,000 lithologic logs were used for the 

percent-sand analysis (fig. 35). Limitations of using lithologic 

logs include errors in spatial location, depth of intervals, and 

lithologic descriptions. Records with obvious errors were 

corrected to extract as much useful information as possible, or 

deleted from the database if the log appeared to be insufficient. 

Most of the lithologic logs in the OWRB database were 

from shallow, domestic wells, which typically only penetrate 

up to approximately 300 feet below land surface (fig. 36). 

Therefore, lithologic logs tend to over-represent the shallow 

aquifer and under-represent the deep aquifer. Lithologic logs 

of the Hennessey Group were not included in the percentsand analysis because many of these logs were from wells 

completed in localized sandstone members in the Hennessey 

Group most likely not connected to the Central Oklahoma 

aquifer. 

Gamma-Ray Logs

Radioactive elements occur naturally in depositional 

particles in sedimentary rocks. Finer particles (mudstones, 

claystones, shales) contain higher concentrations of radioactive elements. Larger particles (sandstones, sands, gravels) 

contain more silica and generally emit very low levels of 

radiation. Gamma-ray borehole logs are useful for differentiating fine-grained rocks (mudstones) that are less permeable 

than coarse-grained rocks (sandstones). For the Central Oklahoma aquifer, gamma-ray logs are useful for detecting changes 

in lithology and identifying potentially water-yielding rocks. 

Gamma-ray logs record by depth the total natural gamma-ray 

radiation emitted by rocks, specifically from the elements 

potassium, thorium, and uranium, which are present in larger 

amounts in mudstones and shales than in sandstones (Keys, 

1990). Gamma-ray logs used in the investigation described in 

this report recorded intensity of gamma-ray radiation in three 

different units: (1) American Petroleum Institute (API) units, 

(2) counts per second, or (3) microRoentgens per hour. The 

gamma-ray logs were obtained from numerous companies, 

Frontier Logging Corporation, and Association of Central 

Oklahoma Governments.

0 50 75 100

Percent sand

25

Sand Muddy sand Sandy mud Mud

87.5 37.5 12.5

Multiplier

62.5

Figure 34. Lithologic 

category bins for converting 

lithologic logs into percent 

sand.
52 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

0 84 16 MILES

0 84 16 KILOMETERS

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

EXPLANATION

Extent of Central Oklahoma aquifer

Eastern extent of Hennessey Group 

confining unit

Lithologic log (Oklahoma Water Resources 

Board, 2013)

Gamma-ray log (from numerous companies, 

Frontier Logging Corporation, and 

Association of Central Oklahoma 

Governments)

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 35. Locations of lithologic logs and gamma-ray logs used for hydrogeologic framework percent-sand analysis of the 

Central Oklahoma aquifer.
Hydrogeologic Framework 53

3,000

2,500

2,000

1,500

1,000

500

0

0 100 200 300 400 500 600 700 800 900 1,000

Number of lithologic logs Number of gamma-ray logs

Log depth, in feet below land surface

Sample size is 11,384 logs.

Bin size is 25 feet.

0

5

10

15

20

25

30

35

40

45

Sample size is 597 logs.

Bin size is 25 feet.

A 

B 

Figure 36. Distribution of depths of A) lithologic logs and B) gamma-ray logs used for hydrogeologic 

framework percent-sand analysis in the Central Oklahoma aquifer.
54 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

The approach used to classify percent sand from the 

gamma-ray data assumed that each gamma-ray log included 

at least one sand (87.5 percent sand) and at least one mud 

(12.5 percent sand). A sand was determined to correspond to 

the minimum intensity and a mud was determined to correspond to the maximum intensity on the gamma-ray log. A 

sand, or minimum intensity gamma-ray, was assigned a value 

of 87.5 percent sand and a pure mud, or maximum intensity 

gamma-ray, was assigned a value of 12.5 percent sand. All 

gamma-ray values between the minimum and maximum 

were scaled relative to the position of the value between the 

12.5 and 87.5 percent sand (fig. 37). This scaling technique 

was independent of the units of measure and normalized the 

gamma-ray logs to make them more comparable. The multipliers for each bin were the same as the multipliers used in the 

lithologic-log conversion (fig. 34).

Selection of the pure mudstone, or maximum gammaray value, was complicated by the presence of spikes in 

gamma-ray intensity. Spikes are anomalously high gammaray intensities that can be three to four times the gamma-ray 

intensity of normal mud. Zones of gamma-ray spikes are 

usually no more than a few feet in thickness, and occur locally, 

most notably near Nichols Hills, Okla. (near The Village; 

fig. 1), The cause of such spikes is unknown, but they could 

be related to increased concentrations of uranium and thorium, 

which emit gamma-ray radiation and can cause anomalously 

high readings. Increased gamma-ray intensities were documented in some core samples (Schlottmann and others, 1998) 

and described on page IV-8 in Gates and others (1983). The 

method used for this report to determine the mudstone/sandstone content would underestimate percent sand if spikes 

were included in the analysis for percent sand. Therefore, 

gamma-ray logs were screened for spikes using an automated 

objective process and a visual subjective process. The method 

of using the minimum and maximum gamma ray as indicators of percent sand for each log makes the method sensitive 

to the presence of spikes, so when identified, spikes were not 

included in the percent-sand analysis.

In areas where the gamma-ray logs contain the overlying Hennessey Group, the base of Hennessey Group structural 

contour map (fig. 6) was used for initial guidance as to where 

to omit the gamma-ray data for the Hennessey Group from the 

analysis. After this screening process, additional examination 

of the gamma-ray logs indicated in some cases, gamma-ray 

values near the top of the logs were much higher than the 

gamma-ray values for the Central Oklahoma aquifer. This 

anomaly was an indication that the structural contour map did 

not always portray the exact vertical location of the Hennessey Group, and the gamma-ray signatures provided a more 

detailed estimate of the depth to base of Hennessey Group. 

The base of freshwater-elevation contours were used to determine the base of the aquifer to remove the logs that penetrated 

below the base of the aquifer from the analysis (fig. 11).

100

300

0

200

500

700

400

600

800

0 50 100 150

Depth, in feet below land surface

Gamma, in American Petroleum Institute (API) units

100 75 50 0

Percent sand

25

Sand Muddy

sand

Sandy

mud

Mud

Figure 37. Scaling technique used to convert a gamma-ray log 

into percent sand for hydrogeologic framework percent-sand 

analysis in the Central Oklahoma aquifer.
Hydrogeologic Framework 55

Approximately 600 gamma-ray logs were used for the 

percent-sand analysis (fig. 35). Most of the gamma-ray logs 

used for the analysis were from water-production wells, 

and some oil and gas wells. Depths of the logs ranged from 

approximately 300 to 1,000 feet below land surface (fig. 36). 

The spatial coverage of the gamma-ray logs was denser in the 

western part of the aquifer where more water-production wells 

are located and sparser in the eastern part of the aquifer where 

more domestic wells have been drilled (fig. 35).

For this investigation, gamma-ray log signatures on paper 

were scanned and digitized, sampling every 0.5-foot using 

Neuralog software (Neuralog, Inc., 2010). The digitized logs 

were saved as text files in Log ASCII Standard format and 

as Microsoft Excel spreadsheets; gamma-ray log sites were 

established in the USGS NWIS database.

Gamma-ray log data were stored at 0.5-foot depth 

intervals and for consistency were summarized in the same 

manner as the lithologic-log data, with the same 4 bins of 

percent sand categories and the same maximum (87.5 percent) 

and minimum percent sand (12.5 percent) (fig. 37). All data 

points were assigned one of four multipliers corresponding to 

the midpoint of each bin (fig. 34). Next, these multipliers were 

summarized for each log by using a weighted average of the 

interval thickness.

Spatial Distribution of Percent Sand

Using gamma-ray logs to determine percent sand produced a dataset that could be summarized into percent sand 

for any defined depth interval. Lithologic logs were used to 

determine percent sand and produced a dataset of total percent 

sand for each log. To spatially distribute the percent sand for 

the hydrogeologic framework, the data points of lithologic log 

percent sand and gamma-ray log percent sand were incorporated into GIS. For spatial interpolations at different depth 

intervals, each lithologic log was represented by a single 

percent sand value. However, for gamma-ray logs, multiple 

percent sand values at 0.5-ft intervals were averaged for each 

interval thickness to be interpolated. 

To distribute percent sand between wells, an inverse 

distance-weighted interpolation method was used. Inverse 

distance-weighted interpolation estimates percent sand for any 

location without logs by using logs surrounding that location, 

giving higher weight to logs closest to that location (Esri, 

2007). Inverse distance-weighted interpolation assumes that 

logs closest to the location without logs are more similar to the 

unknown logs than logs farther away. 

Percent sand was interpolated for individual layers 

to build the hydrogeologic framework. The hydrogeologic 

framework grid was 3,280 ft by 3,280 ft (1 km by 1 km). 

Layers were horizontal and 100-ft thick (fig. 38). The top of 

the hydrogeologic framework was either the base of the Hennessey Group, where present (fig. 6), or the land surface. The 

bottom of the hydrogeologic framework was either the base of 

freshwater (figs. 5 and 11) (equivalent to 5,000 mg/L dissolved 

solids) or the base of the Chase, Council Grove, and Admire 

Groups (figs. 5 and 8). The base of the deepest layer was 

200 ft altitude above North American Vertical Datum 1988 

(NAVD 88). Each subsequent layer was 100 ft [30.48 meters 

(m)] higher. This approach produced 11 layers for the percentsand interpolation. The inverse distance-weighted method was 

used to interpolate between data points for each layer using a 

power of 3 and the maximum number of points was 300. The 

gamma-ray percent sand and the lithologic-log percent sand 

were used to interpolate percent sand between log locations, 

however, preference was given to gamma-ray-derived percent 

sand because gamma-ray logs were more detailed with depth. 

Therefore, lithologic-log locations that were within 9,843 ft 

(3 km) of a gamma-ray log location were omitted from the 

interpolation by using a buffer zone around the lithologic logs. 

The gamma-ray and lithologic logs located beyond 9,843 ft 

(3 km) from a gamma-ray log location were used in the 

inverse distance-weighted interpolation. The length of 9,843 ft 

(3 km) was chosen because any length less than 3 km resulted 

in predominant use of drillers’ logs in the interpolation.

Hydrogeologic Framework Results

The hydrogeologic framework produced a unique distribution of percent-sand values for each of the 11 horizontal 

layers (figs. 38 and 39). Percent-sand values for the horizontal 

layers were designated to be between 12.5 and 87.5 percent 

to remain consistent with previously published percent-sand 

values of 16 to 88 for rocks in the Central Oklahoma aquifer. 

Percent sand interpolated for the 4 deepest layers (8 through 

11) was determined from gamma-ray log data only. Percentsand values interpolated in layers 5 through 7 were determined 

from a combination of lithologic and gamma-ray log data. 

Percent sand interpolated for the shallowest layers (1 through 

4) were determined from lithologic log data only.

The median percent sand derived from gamma-ray logs 

was approximately 63, whereas the median percent sand from 

lithologic logs was approximately 53 (fig. 40). The range of 

percent sand from lithologic logs is higher than the range of 

percent sand from the gamma-ray logs (fig. 40). The differences in percent sand from the two data sources could be a 

result of the difference in sampling locations; the gamma-ray 

logs mostly capture the deeper zones of the western part of the 

aquifer, which contain thicker sections and larger percents of 

sandstone (Schlottman and others, 1998), but most lithologic 

logs used in this analysis are located in the eastern part of the 

aquifer (fig. 35), which contain thinner sections and lower 

percents of sandstone (Schlottman and others, 1998). Another 

possible cause of the difference in percent-sand estimates is 

that the two methods were fundamentally different.
56 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Groundwater-Flow Model

A numerical groundwater-flow model was constructed for 

the Central Oklahoma aquifer to simulate groundwater flow, 

build water budgets under various stresses, and to describe 

how groundwater storage may change under these stresses. 

The groundwater-flow model was calibrated using water-level 

observations and was subsequently used to evaluate various 

pumping scenarios projected to the year 2059 to evaluate the 

effects of pumping on the amount of water in storage in the 

Central Oklahoma aquifer. 

Conceptual Flow Model

A conceptual flow model is a narrative and schematic 

description of a groundwater-flow system, and an important 

component of constructing a numerical groundwater-flow 

model. The conceptual flow model describes how the groundwater-flow system is thought to function, and thus contains the 

framework and components that control the storage and flow 

of groundwater. The two key components of the conceptual 

flow model include the hydrologic boundaries and the water 

budget. The hydrologic system boundaries are parts of the 

flow system that interact with groundwater, providing a condition in which water enters or leaves the system. The water 

budget describes how much of the water in the flow system is 

accounted for by each of the boundaries. 

Hydrologic boundaries are important for achieving a 

unique solution to a simulation, and include internal and 

exterior types (Reilly, 2001). Internal hydrologic boundaries include wells, streams (streams also can be external if no 

appreciable flow moves under the stream), and lakes inside the 

model domain. Hydrologic boundaries at the lateral or vertical extents are exterior boundaries and can include confining 

units, faults, or lithofacies changes. The discretization of time 

that the model uses also is a boundary, but this boundary is 

described in the Numerical Groundwater-Flow Model Construction Simulation Periods section. 

External boundaries of the Central Oklahoma aquifer 

used in this model included: (1) zero-flow boundaries where 

the aquifer is absent or no substantial flow is assumed to cross 

that boundary, and (2) streams that interact with the aquifer. 

The east external boundary is considered to be zero-flow, as 

the Central Oklahoma aquifer becomes thin moving up-dip of 

the geologic units and is removed by erosion at the surface. 

The western boundary also is assumed to have zero flow as 

the part of the aquifer saturated with freshwater intersects the 

Hennessey Group confining unit. The northern boundary of 

the Central Oklahoma aquifer is assumed to be the Cimarron 

River, and the southern boundary is assumed to be the Canadian River. These rivers flow from west to east through areas 

where the freshwater zone of the aquifer is relatively thin and 

previous studies of the potentiometric surface indicate that 

little or no flow passes beneath the streams in either direction 

11

10

9

8

7

6

5

4

3

2

1

1,500

1,000

500

NAVD 88

-500

WEST EAST

Modified from Schlottmann and others, 1998

FEET

VERTICAL SCALE GREATLY EXAGGERATED

Mustang

Moore

Shawnee

Garber Sandstone and

Wellington Formation,

undifferentiated

Chase, Council Grove,

and Admire Groups

Pennsylvanian geologic units,

undifferentiated

 (includes the Vanoss Formation)

A A׳

Base of fresh groundwater

EXPLANATION

Model layer with layer number—

Dashed lines indicate areas not

analyzed for percent sand

Hennessey Group

(confining unit)

Alluvium not shown on cross section 

because units are very thin

Saline water

CANADIAN

COUNTY

CLEVELAND COUNTY POTTAWATOMIE COUNTY

0 105

0 5 10 15 MILES

15 KILOMETERS

Stanley

Draper

Lake Potentiometric

surface Aquifer

thickness

Thickness

of fresh

groundwater

Central

Oklahoma

aquifer

1

Figure 38. Cross-section A–Aʹ diagram (shown on figure 4) showing layers for which percent sand was interpolated in the 

hydrogeologic framework of the Central Oklahoma aquifer.
Groundwater-Flow Model 57

(figs. 10 and 12) (Christenson and others, 1992; Mashburn and 

Magers, 2011).

The lower external boundary of the Central Oklahoma 

aquifer is defined as either (1) the contact between the Chase, 

Council Grove, and Admire Groups (undifferentiated), a 

confining unit, and the Vanoss Formation (figs. 8 and 38) 

or (2) the depth of the base of freshwater (groundwater that 

contains less than 5,000 mg/L dissolved solids) (figs. 11 and 

38). On the eastern part of the model area, the lower boundary 

is defined as the contact with the Chase, Council Grove, and 

Admire Groups (undifferentiated), a confining unit (fig. 38). 

The map of the base of fresh groundwater shows the freshwater/saline interface intersecting the base of the Hennessey 

Group in the western part of the Central Oklahoma aquifer 

near the Oklahoma-Canadian/Kingfisher-Logan County line, 

which indicates that circulation of freshwater does not extend 

beyond this intersection (fig. 11). In addition, Hart (1966) also 

indicates a sharp increase from about 200 to 800 ft in elevation 

of the base of fresh groundwater near the Oklahoma-Canadian/Kingfisher-Logan County line. Therefore, the western 

extent of the Central Oklahoma aquifer was established at 

the freshwater/saline interface near the Oklahoma-Canadian/

Kingfisher-Logan County line. The potentiometric-surface 

map in Mashburn and Magers (2011) indicates that freshwater 

is present in the alluvium and Hennessey Group, but circulation of this freshwater in the Hennessey Group is assumed to 

be minimal because of low transmissivities.

The Central Oklahoma aquifer is believed to have a high 

vertical anisotropy ratio causing limited circulation and flow in 

deep parts of the aquifer (near the freshwater/saline interface). 

The recharge age of water sampled from deep wells in the 

Central Oklahoma aquifer has been found to be old, as much 

as 30,000 years (Parkhurst and others, 1996), indicating that 

under natural and stressed conditions, little to no mixing with 

this deep water takes place. If future pumping from deep parts 

of the aquifer is to be studied, however, this boundary would 

need to be further evaluated.

The top model boundary is assumed to be the ground 

surface, and is unconfined. The overlying Hennessey Group 

confining unit is assumed to have a small hydraulic conductivity and is included in the model. Limited flow is assumed 

to take place between the Hennessey Group and the Central 

Oklahoma aquifer, but the Hennessey Group was not setup in 

the model as a no-flow boundary. The alluvium and terrace 

deposits, associated with streams, overly the Central Oklahoma aquifer and were not differentiated for the model. The 

alluvium and terrace deposits were included in the top of the 

model, but no attempt was made to determine or simulate the 

flux through the alluvium and terrace deposits. 

Internal boundaries used in this model include wells, 

streams, and reservoirs. Reservoirs are considered to be 

general-head boundaries, which simulate flow into or out of 

a model cell from an external source. The simulation uses a 

linear relation between the head in the external source and 

the head in the model cell (Harbaugh, 2005). These boundaries provide controls of the potentiometric surface and the 

groundwater-flow system. Wells are discharge points where a 

known volume of water for each time period is removed from 

the model (Konikow and others, 2009). The wells used in this 

model were domestic and public-supply wells.

Stream boundaries were used to simulate all perennial 

streams in the model area. These boundaries can interact with 

the aquifer based on the head in the aquifer relative to the 

stream stage, and the conductivity of the streambed material. 

Water is routed through each stream reach and in each reach, 

the flux either to the stream or to the aquifer is determined. 

Other stream parameters include channel width, slope, roughness, and length. Much of the stream-groundwater interaction is assumed to take place in the overlying alluvial valley 

deposits, which were too thin to include as a hydrogeologic 

unit in the scope of this study. The total stream-aquifer flux 

was constrained using streamflow-gaging stations upstream 

and downstream from the Central Oklahoma aquifer.

Evapotranspiration, which removes water from the flow 

system where the groundwater is shallow enough to intersect 

the root zone, was not simulated in this model directly, but 

rather was estimated and removed from incoming precipitation when calculating surface recharge using the SWB code 

(described in the Recharge section of this report). Some 

unaccounted-for evapotranspiration probably occurs in riparian areas, but estimating the additional flux caused by vegetation was beyond the scope and objectives of this study. 

As previously described, recharge is defined here as 

amount of water that passes the soil root zone, percolates to 

the regional water table, and becomes part of the groundwaterflow system. Estimates from the SWB code provide a realistic spatial distribution of recharge across the model area, 

though the amount that reaches the aquifer is approximate 

and is adjusted when SWB-generated recharge is used in 

groundwater-flow models. 

Numerical Groundwater-Flow Model 

Construction

MODFLOW 2005 (Harbaugh, 2005) was used to simulate boundaries and fluxes in the Central Oklahoma aquifer 

for the numerical groundwater-flow model. The files for the 

model were constructed using ArcGIS Desktop to convert 

spatial data to tabular files that can be read by the MODFLOW 

program. The Central Oklahoma aquifer was simulated using 

a grid composed of 105 columns by 122 rows of 3,280-ft by 

3,280-ft (1-km by 1-km) size and 11 horizontal layers, each 

100-ft thick (30.48 meters) (figs. 38 and 41). Figure 39 shows 

the layers for the percent sand analysis, which were not analyzed for the Hennessey Group confining unit. However, the 

Hennessey Group is included in the model and the model layers would look similar to figures 38 and 39. Layers included 

the vertical thickness of the Central Oklahoma aquifer and the 

Hennessey Group confining unit, which was not in a dedicated layer, but distinguished by specification of a relatively 

small value of hydraulic conductivity. The entire aquifer was 
58 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

PAYNE CO OC R EHSI F GNI K

LOGAN CO

N CO AI DANAC

OC E LONI MES

Y CO DARG

POTTAWATOMIE

CO

MCCLAIN CO

OKLAHOMA

CO

CLEVELAND

CO

96°40’ 97° 97°20’ 97°40’

36°

35°40’35°20’

35°

PAYNE CO OC R EHSI F GNI K

LOGAN CO

N CO AI DANAC

OC E LONI MES

Y CO DARG

POTTAWATOMIE

CO

MCCLAIN CO

OKLAHOMA

CO

CLEVELAND

CO

96°40’ 97° 97°20’ 97°40’

36°

35°40’35°20’

35°

PAYNE CO OC R EHSI F GNI K

LOGAN CO

N CO AI DANAC

OC E LONI MES

Y CO DARG

POTTAWATOMIE

CO

MCCLAIN CO

OKLAHOMA

CO

CLEVELAND

CO

96°40’ 97° 97°20’ 97°40’

36°

35°40’35°20’

35°

PAYNE CO OC R EHSI F GNI K

LOGAN CO

LINCOLN CO

N CO AI DANAC

OC E LONI MES

Y CO DARG

POTTAWATOMIE

CO

MCCLAIN CO

OKLAHOMA

CO

CLEVELAND

CO

96°40’ 97° 97°20’ 97°40’

36°

35°40’35°20’

35°

PAYNE CO OC R EHSI F GNI K

LOGAN CO

N CO AI DANAC

OC E LONI MES

Y CO DARG

POTTAWATOMIE

CO

MCCLAIN CO

OKLAHOMA

CO

CLEVELAND

CO

96°40’ 97° 97°20’ 97°40’

36°

35°40’35°20’

35°

LINCOLN COLINCOLN CO

LINCOLN CO

LINCOLN CO

EXPLANATION

Percent sand—Percent sand was used to estimated the average 

hydraulic conductivity for each groundwater-flow model cell (see Numerical Groundwater-Flow Model Construction Hydraulic Properties section)

12.5 to 20.020.1 to 27.527.6 to 35.035.1 to 42.542.6 to 50.0

50.1 to 57.557.6 to 65.065.1 to 72.572.6 to 80.080.1 to 87.5

Layer 1 [1,200–1,300 feet above 

North American Vertical Datum of 1988 (NAVD 88)]

Central Oklahoma aquifer extentEastern extent of Hennessey Group confining unit—Line 

represents the contact of the base of the Hennessey Group with the Central Oklahoma aquifer. The Hennessey Group acts as a confining unit and overlies the western part of the Central Oklahoma aquifer

Lithologic log (Oklahoma Water Resources Board, 2013)Gamma-ray log

Layer 2 (1,100–1,200 feet above NAVD 88) Layer 3 (1,000–1,100 feet above NAVD 88)

Layer 4 (900–1,000 feet above NAVD 88) Layer 5 (800–900 feet above NAVD 88)

A

Central Oklahoma aquifer and Hennessey boundaries from Runkle, Christenson, and Rea, 1997. Base from Horizon Systems Corporation, 2010, and University of Oklahoma Center for Spatial Analysis, 2013Universal Transverse Mercator projection, Zone 14, North American Datum of 1983

Figure 39. Interpolated percent sand and log locations 

A) for layers 1 through 5 for the hydrogeologic framework and 

B) for layers 6 through 11 for the 

hydrogeologic framework.
Groundwater-Flow Model 59 Figure 39. Map showing iInterpolated percent sand and log locations A) for layers 1 through 5 for the hydrogeologic framework and B) for layers 6 through 11 for the hydrogeologic framework.—Continued

PAYNE CO O

C R 

E

H

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F

G

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LOGAN CO

N COAIDANAC

OC E LONIMES

Y CODARG

POTTAWATOMIE

CO

MCCLAIN CO

OKLAHOMA

CO

CLEVELAND

CO

96°40’ 97° 97°20’ 97°40’

36°

35°40’35°20’

35°

LINCOLN

CO

PAYNE CO O

C R 

E

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S

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F

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OC E LONIMES

Y CODARG

POTTAWATOMIE

CO

MCCLAIN CO

OKLAHOMA

CO

CLEVELAND

CO

96°40’ 97° 97°20’ 97°40’

36°

35°40’35°20’

35°

LINCOLN

CO

PAYNE CO O

C R 

E

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S

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OC E LONIMES

Y CODARG

POTTAWATOMIE

CO

MCCLAIN CO

OKLAHOMA

CO

CLEVELAND

CO

96°40’ 97° 97°20’ 97°40’

36°

35°40’35°20’

35°

LINCOLN

CO

PAYNE CO O

C R 

E

H

S

I

F

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N

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LOGAN CO

N COAIDANAC

OC E LONIMES

Y CODARG

POTTAWATOMIE

CO

MCCLAIN CO

OKLAHOMA

CO

CLEVELAND

CO

96°40’ 97° 97°20’ 97°40’

36°

35°40’35°20’

35°

LINCOLN

CO

PAYNE CO O

C R 

E

H

S

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OC E LONIMES

Y CODARG

POTTAWATOMIE

CO

MCCLAIN CO

OKLAHOMA

CO

CLEVELAND

CO

96°40’ 97° 97°20’ 97°40’

36°

35°40’35°20’

35°

LINCOLN

CO

PAYNE CO O

C R 

E

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OC E LONIMES

Y CODARG

POTTAWATOMIE

CO

MCCLAIN CO

OKLAHOMA

CO

CLEVELAND

CO

96°40’ 97° 97°20’ 97°40’

36°

35°40’35°20’

35°

LINCOLN

CO

Layer 6 (700–800 feet above NAVD 88) Layer 7 (600–700 feet above NAVD 88) Layer 8 (500–600 feet above NAVD 88)

Layer 9 (400–500 feet above NAVD 88) Layer 10 (300–400 feet above NAVD 88) Layer 11 (200–300 feet above NAVD 88)

B
60 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

600

500

400

300

200

100

0

10 18 26 34 42 50 58 66 74 82 90

Number of lithologic logs Number of gamma-ray logs

Percent sand

Sample size is 11,384 logs.

Bin size is 2 percent.

0

10

20

30

40

50

60

70

80

90

Sample size is 597 logs.

Bin size is 2 percent.

A 

B 

Figure 40. Derived percent sand distributions from A) lithologic logs and B) gamma-ray logs.
Groundwater-Flow Model 61

simulated as convertible, by which confined conditions are 

simulated when water level in a cell is above the top of the 

cell, and unconfined conditions are simulated when water level 

is below the top of the cell. If the water level drops below the 

bottom of the cell, the cell is simulated as ‘dry’, and becomes 

inactive. Rewetting was not simulated. The groundwater-flow 

equation was solved using the Preconditioned ConjugateGradient package (Harbaugh and others, 2000). 

Assumptions

Using the MODFLOW finite-difference flow model to 

simulate groundwater flow requires several assumptions about 

the system being modeled. Assumptions pertinent to this study 

include the following:

Water flows through the Central Oklahoma aquifer 

according to Darcian flow principles.—Water is assumed to 

be incompressible, aquifer properties are homogeneous and 

isotropic, and behave as if of infinite areal extent. Flow in each 

cell is laminar and not turbulent.

For the problem under consideration, the Central Oklahoma aquifer can be adequately simulated for an aquifer-scale 

water-supply issue using 3,280-ft by 3,280-ft cells, and 11 

model layers of 100-ft thickness.—Many parameters such as 

hydraulic conductivity and specific yield are known to change 

on a spatial scale much smaller than 3,280 ft. The average 

value of measured or interpolated parameters in cells are 

assumed to adequately model the average flow conditions in 

the Central Oklahoma aquifer. Also, though the parameters 

change on a local scale, they are not sampled on the scale of 

their spatial variance.

The hydrogeologic framework is assumed to be a suitable 

basis to capture the textures of the Central Oklahoma aquifer 

and represent the distribution of hydraulic conductivity of the 

aquifer for the groundwater-flow system.—Aquifer hydraulic 

properties change quickly in the vertical direction. Ideally, 

a MODFLOW model would use model layers that represent 

hydrogeologic units that have consistent and similar hydraulic 

properties. There are no discrete hydrogeologic units with consistent or distinctive properties in the Central Oklahoma aquifer, however the aquifer does have complex vertical flow paths 

that require multiple layers, particularly in the near-surface 

parts of the aquifer. Thus, assigning interpolated and average 

parameters to cells with a constant layer thickness is assumed 

to adequately simulate flow entering at the land surface, travel 

through a complex mix of lenticular sand bodies and mudstone 

beds, and discharge at wells and streams.

The groundwater-flow system was at an approximate 

equilibrium during the initial model period of 1987.—Because 

hydrologic data were not available for a period before groundwater resources were developed, a period when recharge and 

reported well withdrawals were similar was identified so that 

the flow system was not in a state of great flux. The year 1987 

had similar stresses in comparison with 1986 and 1985 and 

is assumed to suffice in avoiding the effects of calibrating a 

model to a system that is undergoing change on a time scale 

smaller than the model time steps.

Simulation Periods

Temporal model design is important as a boundary condition that must be scaled to achieve the study objectives of 

estimating the amount of water in storage and effects to this 

aquifer based on proposed management plans. Time periods 

of groundwater-system simulation can be as a steady-state or 

a transient model that includes changes in system stress and 

water in storage. In a steady-state simulation, the head in a 

given model cell does not change with time. The time discretization of the transient model is dependent on the objectives 

of the model, the rate of changes in stress on the system, and 

the available model inputs. The objectives of developing a 

groundwater-flow model were used to simulate flow in the 

Central Oklahoma aquifer and use a 50-year predictive model 

to estimate the effects of different pumping scenarios on available water in storage. Thus, a long-term transient model was 

needed that spanned wet and dry periods and periods of different pumping rates. Because two synoptic water-level measurement events were available for 1987 and 2009, and pumping 

increased slightly during this 23-year period, this period was 

selected for the transient model. The year 1987 was used as 

an initial quasi-steady-state calibration time period, and the 

transient model included 1987 and continued through 2009.

The period of the predictive model was 2010 through 

2059 (started using 2009 fluxes). Stress periods 1-year long 

were chosen because the largest stress on the aquifer was the 

reported well pumping, and the discharge rates reported for 

these wells were only available on an annual basis. 

Boundaries

Head-dependent and flux-boundary conditions used 

and described in this section are shown in figure 41. Headdependent flux boundaries are used to simulate flow into and 

out of aquifer cells based on a specified head in the headdependent flux cell. Specified flux boundaries are used in a 

numerical groundwater-flow model to simulate flow into and 

out of aquifer cells based on a specified flux rate. The flux rate 

is usually initially determined outside of MODFLOW, but 

can be adjusted in the groundwater-flow model. Specified flux 

boundaries can be used to represent recharge and withdrawal 

rates.

Streams

Stream boundaries were simulated using the Streamflow 

Routing Package version 2 (SFR2) for MODFLOW (Niswonger and Prudic, 2005). Simulated streamflow enters the 

model domain from the west in the Cimarron, North Canadian, and Canadian Rivers. The average annual daily mean 

streamflow at the streamflow-gaging stations nearest to the 

western extent of the active model area with at least 10 years 
62 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

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97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

Active cell

Inactive cell

EXPLANATION

Streamflow routing cell

General-head boundary cell

Extent of Central Oklahoma aquifer

Eastern extent of Hennessey Group 

confining unit

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Base from University of Oklahoma Center for Spatial 

Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Column 10, row 1 Column 105, row 1

Column 105, row 122

Figure 41. Numerical groundwater-flow model grid and boundary conditions for the Central Oklahoma aquifer study (cells are 

3,280-foot by 3,280-foot).
Groundwater-Flow Model 63

of record were used to determine inflow rates for each annual 

stress period in the model. Inflow for the Cimarron River was 

from the USGS streamflow-gaging stations near Dover, Okla., 

(07159100) (not shown on figures, outside of map extents). 

Inflow for the North Canadian River was determined from 

data collected at the USGS streamflow-gaging station below 

Lake Overholser near Oklahoma City, Okla., (07241000), and 

the flow entering the model in the Canadian River was determined from data collected at the USGS streamflow-gaging station at Bridgeport, Okla., (07228500) (not shown on figures, 

outside of map extents). 

Simulated streams that originate in the active model area 

include the Deep Fork and Little Rivers, and numerous small 

tributaries. The channel conductance for all stream segments 

was set at 1.5 meters per day, similar to that of unconsolidated fine sand and silt (Fetter, 1994). The channel widths 

of all modeled streams were provided by the OWRB (Maria 

Moreno, Oklahoma Water Resources Board, written commun., 

2011; fig. 42). The streambed altitude of each stream segment 

was derived from DEM grids (http://ned.usgs.gov/).

Lakes

Lakes were simulated as general head boundaries (GHB), 

which simulates flow into or out of a model cell based on the 

relative head between the cell and surrounding cells. The GHB 

package (Harbaugh, 2005) uses a linear relation between the 

head in the external source and the head in the model cell. 

Only lakes east of the Hennessey Group outcrop were modeled, including Arcadia, Bell Cow, Stanley Draper, Guthrie, 

Langston, Liberty, Meeker, Shawnee, Tecumseh, Thunderbird, 

and Wes Watkins (see fig. 6 for lake locations). Because the 

transient-stage levels in these lakes were not recorded, the 

head in GHB cells were set to the level of the lake provided on 

USGS topographic maps and was assumed to remain constant 

throughout the model run. Conductivity for each GHB cell 

was set at one-half the estimated hydraulic conductivity of the 

aquifer at that location to account for finer sediments that are 

typically at the bottom of lakes. Lakes with stream inflows 

were modeled with SFR2 and flow was routed through the 

lakes with no losses or interaction with the aquifer; the same 

discharge was assumed to leave the lake as entered. 

Recharge

Recharge was simulated in the numerical groundwaterflow model using the recharge package (RCH), which distributes recharge to the top of the model at a specified rate 

(Harbaugh, 2005). Spatial distribution of recharge rates for 

the simulated time periods for the groundwater-flow model 

were estimated using climate data and the SWB code. Because 

water leaving the root zone does not necessarily reach the 

water table, SWB recharge was adjusted using two multiplier 

grids. Recharge was applied to the uppermost model cells 

located near the land surface. Therefore, recharge was applied 

to parts of model layers because the land surface was not represented by only one layer (fig. 38). 

Withdrawals

Withdrawals from the Central Oklahoma aquifer were 

simulated in the numerical groundwater-flow model using the 

multi-node well package version 2 (MNW2), which simulates 

withdrawals from wells connected to more than one node of 

the finite-difference model grid (Konikow and others, 2009). 

MNW2 simulates pumping from multiple layers using the 

pumping head in each layer, the length of well screen in each 

layer, and the well losses caused by several factors such as 

wellbore-skin effect. During the simulation, if a layer went 

dry, the layer was excluded from pumping, which was useful 

for the depletion scenario simulation because a constant pumping rate could be set for a hypothetical well, and the aquifer 

could dry up without affecting the pumping until the lowest 

active layer was dry. The MNW2 package also provides for 

well-bore flow between layers. This flow can be an important 

aspect of the flow system if there are vertical head gradients, 

such as when a well at depth is pumping. Many of the modeled wells had well-bore flow.

Water use reported to the OWRB includes uses for public-supply, irrigation, industrial, power, mining, commercial, 

and other. Reported water use was compiled by the OWRB 

for the simulated time periods for the groundwater-flow model 

(figs. 19–23). The annual water use for each permit holder was 

related to specific wells so that these water-use data could be 

incorporated as withdrawals for each groundwater-flow model 

cell. The perforated intervals were provided for wells with 

well log information, and these intervals were assigned to the 

model layer in which they were located using MNW2. For 

wells without gravel pack and screen information, or lacking 

well-log information, withdrawals were assumed from each 

layer by using the completion depth. Wells for which reported 

use was simulated in the numerical groundwater-flow model 

are shown in figure 42. Domestic water use is not regulated 

by the State of Oklahoma and was estimated using census 

population data for the simulated time periods for the numerical groundwater-flow model as described in the Withdrawals 

for Groundwater Use section. 

Public-supply wells completed in the Central Oklahoma aquifer are typically constructed to depths ranging 

from approximately 350 to 800 feet below land surface 

with gun-perforated openings in stainless steel or polyvinyl 

chloride casing in a cement annulus, as described in OWRB 

well-completion reports for public-supply wells. Wells that 

are gun-perforated do not allow groundwater to flow into the 

well from the nonperforated zones. A small percent of publicsupply wells completed in this aquifer have gravel-packed 

annulus and screen, wire-wrap, or slotted openings. Reported 

wells were included in the model using their locations. The 

depth to the top and bottom of each perforation or screen was 

used to determine the layer from which they withdrew water. 

The pump was assumed to be placed at the midpoint of all 

perforations or screens. The total reported pumping for a given 

year was converted to cubic meters per day and applied to 

each well. If two wells were located in one model cell, MNW2 
64 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

0 84 16 MILES

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Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Stream channel widths from M. Moreno, Oklahoma

Water Resources Board, written commun., 2011

Municipal wells provided by Oklahoma Water

Resources Board, 2013

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

EXPLANATION

Stream channel width, in meters

4 to 5

6 to 12

13 to 21

22 to 65

66 to 179

Well from which reported use 

was simulated

Extent of Central Oklahoma aquifer

Eastern extent of Hennessey Group 

confining unit

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 42. Stream channel widths and wells from which reported use was simulated in the transient groundwater-flow model 

for the Central Oklahoma aquifer.
Groundwater-Flow Model 65

calculates the extraction from each layer, and MODFLOW 

takes the sum of all wells in each layer in each cell. 

Well drillers are required to submit well-completion 

reports to the OWRB for water wells drilled in the State of 

Oklahoma. The well-completion reports for domestic wells 

describe information about well construction, location, and 

owner, but no records are kept for quantities of water use from 

domestic wells. Domestic wells in the Central Oklahoma aquifer typically are completed to depths of less than 300 feet, with 

slotted polyvinyl chloride or stainless steel casing near the bottom of each well ranging to as much as 20–40 feet in length, 

as described in OWRB well-completion reports for domestic 

wells. The annulus in these domestic wells are usually gravel 

packed to as high as 15 or 20 feet below land surface allowing groundwater to flow into the well from multiple zones, 

although a larger percent of groundwater likely will flow into 

the well nearer to the location of the well pump intake in the 

screen. Irrigation wells completed in the aquifer typically are 

constructed similarly to domestic wells although irrigation 

wells may be completed to deeper depths. 

The depths (from well-completion reports) to which 

domestic wells are typically completed was analyzed by the 

OWRB (fig. 43). Domestic wells in the model were assigned 

a layer below the top of the model based on the depths at 

which most domestic wells are completed. Domestic use was 

incorporated into the model as a withdrawal using the MNW2 

package. As domestic wells are typically gravel-packed, the 

MNW2 package allowed domestic well extraction to be split 

over multiple layers for each model grid cell stack.

Hydraulic Properties

Hydraulic properties of the groundwater-flow model were 

estimated for the aquifer and the confining Hennessey Group. 

Hydraulic properties for the groundwater-flow model initially 

were estimated using the three-dimensional distribution of 

percent-sand values from the hydrogeologic framework. 

Hydraulic conductivity for model cells representing the 

Hennessey Group was set to 1.0 x 10-4 ft/d. The extent of the 

base of Hennessey Group for the model was determined from 

a previous structure-contour map of the altitude of the base of 

Hennessey Group (fig. 6). 

To estimate the average hydraulic conductivity in each 

model cell representing the Central Oklahoma aquifer, a 

mathematical relation was developed to relate the percent 

sand to the hydraulic conductivity using published values for 

fine sandstone and silty claystone. Hydraulic conductivity of 

3.3 feet per day (ft/d) was assumed for fine sandstone (sand 

from percent-sand analysis) and 0.33 ft/d for silty claystone (mud from percent-sand analysis) after Domenico and 

Schwartz (1998). This range spans grain sizes expected to be 

in the model cells and also includes the 2.4 ft/d hydraulic conductivity estimated at the Norman aquifer test. The minimum 

average percent sand for a cell estimated from lithologic and 

gamma-ray logs was 12.5 percent, and the maximum percent 

sand was 87.5 percent. Assuming that the minimum hydraulic 

conductivity of 0.33 ft/d is represented by 12.5 percent sand, 

and 3.3 ft/d is represented by 87.5 percent sand, and that a 

linear relation exists between percent sand and hydraulic conductivity, then the approximate average hydraulic conductivity 

for any cell was assumed to be:

Hk = (0.0396 × Ps ) − 0.165 (1)

where

Hk is the hydraulic conductivity in ft/d; and

Ps is the percent sand.

A similar relation was derived for the specific yield of 

the aquifer, with a linear relation between percent sand and 

specific yield being:

Sy = (0.0027 × Ps ) − 0.0233 (2)

where

Sy is the specific yield; and

Ps is the percent sand.

This relation is approximate, but no known field measurements exist in the Central Oklahoma aquifer in which a 

long-duration aquifer test to calculate Sy

 has been completed 

in an unconfined setting where percent sand was known. This 

method estimated the minimum specific yield to be 0.01 for 

silty claystone (mud from percent-sand analysis) and 0.21 for 

fine sandstone (sand from percent-sand analysis).

Anisotropy, or the ratio of horizontal to vertical hydraulic 

conductivity, also was estimated from the percent sand, but 

was not linear. The two longest axes of lenticular sand bodies 

were assumed to be horizontal. Though the sand bodies may 

be randomly distributed in a given area, the horizontal hydraulic conductivity will be higher than the vertical conductivity 

because any horizontal flow path will encounter more sand 

than a vertical flow path. The maximum anisotropy for the 

model was assumed to be 10. 

The confined storage coefficient value was assumed to 

be small (0.0001), similar to the values calculated in available 

aquifer tests, and was assumed to be uniform. This storage 

coefficient value was adjusted subsequently for each layer 

independently for model calibration, keeping a single storage 

coefficient value per layer.

Quasi-Steady-State Simulation

A quasi-steady-state model is a transient model that is run 

with constant aquifer stresses for one stress period. The quasisteady-state model was run to simulate the 1987 calendar year 

with equilibrium in flow and minimal changes in storage. The 

year 1987 was chosen for the steady-state model because there 

were few water-level data available for model calibration prior 

to this year. A quasi-steady-state model was chosen because 

there are pumping stresses in the aquifer during 1987. The 
66 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

0 84 16 MILES

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97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

Canadian River

NorthCa nadian Riv er

44

35

40 240

40

35

44

235

EXPLANATION

Depth below land surface, in feet

70

120

250

400

Extent of Central Oklahoma aquifer

Eastern extent of Hennessey Group 

confining unit

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Depths provided by Oklahoma Water Resources Board, 2013

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Figure 43. Depths from land surface that estimated domestic use was withdrawn for the transient groundwater-flow model 

for the Central Oklahoma aquifer.
Groundwater-Flow Model 67

initial model run was a long-duration transient model that was 

run until there was little change in water in storage, indicating 

that the flow system was in equilibrium with the inflows and 

outflows defined for 1987. This model was a quasi-steady-state 

model and there may have been some differences between this 

model and a model run in steady-state mode. 

Simulation Inputs

This section describes the simulation inputs that were 

not adjusted during the calibration process. These inputs 

include the vertical boundaries described in the Numerical 

Groundwater-Flow Model section, starting heads, estimated 

storage parameters, well-construction parameters, and specified heads in boundary conditions. Storage parameters were 

not used in the quasi-steady-state model because there was no 

time function and no change in storage. 

Two-dimensional arrays were derived for hydraulic 

conductivity, vertical anisotropy, and specific yield from 

percent sand across the model area using the methods 

described in the Aquifer Hydraulic Properties section of this 

report. The groundwater-flow model did not have layers that 

were assigned to specific hydrogeologic units. The layers by 

elevation with assigned hydraulic values provided a method 

to capture gradual vertical changes in hydraulic parameters 

and allow for the analysis of vertical flow in the Central 

Oklahoma aquifer.

Starting heads in the model were from the 1986 to 1987 

water-level measurements, described in the Regional Groundwater Flow section of this report. These water levels represented points on the uppermost potentiometric surface of the 

Central Oklahoma aquifer, and did not include any parts of the 

aquifer that behave as a confined aquifer because of the overlying Hennessey Group confining unit, or high local vertical 

anisotropy. This head was applied to all layers of the model to 

start the simulation, and heads in lower layers were allowed to 

adjust to stresses and estimated vertical anisotropy. 

Inflow to the Cimarron, North Canadian, and Canadian 

Rivers was set at a constant flow equal to the median mean 

daily flow for 1987 measured at the nearest upstream streamflow-gaging station. GHB heads were set at the average stage 

for the reservoir that each GHB cell represented. Conductivity 

for each GHB cell was set at one-half the estimated hydraulic 

conductivity of the aquifer at that location. 

Calibration Targets

A subset of water-level measurements made in 1987 was 

compared to simulated heads to determine how well the simulation mimicked actual groundwater conditions in an assumed 

equilibrium condition. The subset included observations that 

were not in the same cell as a pumping well or stream, or were 

too close to a GHB or no-flow boundary. A total of 262 head 

observations were included, which sampled layers 2–8.

Calibration Process

Parameters that were adjusted to affect quasi-steady-state 

model calibration included hydraulic conductivity, vertical anisotropy, and recharge. The methods used to estimate 

conductivity and recharge were assumed to better represent 

the spatial distribution of these parameters than the estimated 

value of the parameters. Thus, during calibration the spatial 

distribution was preserved as much as possible while adjusting 

estimated values. A block diagram of the hydraulic conductivity used in the model is shown in figure 44.

To evaluate the model calibration, the Head Observation 

(HOB) Package for MODFLOW (Hill and others, 2000) was 

used. This package compares head targets (head observations) 

in one or more layers to the heads generated by the simulation, 

and reports both heads and the difference—the residual—in 

an output file. The observed heads were each assigned to a 

model cell using the location, and one or more model layers 

using the total well depth below land surface (TD) or open 

intervals. The HOB Package adjusts the simulated head to 

multiple layers by weighting the heads simulated in each layer 

by the screened interval in the layer. The layers sampled were 

biased toward the shallow and middle layers, with no targets 

in layers 9, 10, or 11 (fig 45). Layer 1 also contained no targets. Because this model is a generalized depiction of highly 

Hydraulic conductivity,

 in feet per day

EXPLANATION

0.003281

0.003282 to 1.326

1.327 to 1.740

1.741 to 2.019

2.020 to 2.211

2.212 to 2.379

2.380 to 2.519

2.520 to 2.674

2.675 to 2.890

2.891 to 3.250

N

Figure 44. Horizontal hydraulic conductivity per model cell 

viewed from the southwest and truncated at model row 70, 

showing higher conductivity in the center of the aquifer and 

the low conductivity of the Hennessey Group on the west (red). 

Surface outline of the aquifer is shown in black and volume is 

shaded gray.
68 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

variable local hydraulic properties, there was expected to be 

a degree of error in the model; at some observation locations, 

head would not be sensitive to changes in any of the parameters being adjusted to calibrate the model. 

The initial method for calibrating the quasi-steady-state 

model was to scale a given parameter (hydraulic conductivity, 

vertical anisotropy, and recharge) for an entire layer array by 

the same multiplier and evaluate the change in model residuals—the difference between the observed head observations 

and the simulated heads. A multiplier was applied to each 

parameter one layer at a time, and the change in the summed 

squares of residuals recorded. The multiplier was then adjusted 

and the process started again.

Model runs consisted of using the interpolated 1987 

potentiometric surface as the initial heads for one run. The 

resulting heads were saved and used as the starting heads 

for the subsequent run. This process was repeated for 

10 model runs. At the end of the tenth run, the model massbalance discrepancy, the amount of water that entered or was 

released from storage, and head residuals were recorded. The 

mass-balance discrepancy indicates how well the numerical 

groundwater-flow model simulated the system water budget; 

the lower the discrepancy, the closer the model came to balancing the inflow with the outflow, and converged on a stable 

mathematical solution. 

The amount of water moving in or out of storage is 

an indication of how well the system is in equilibrium with 

the quasi-steady-state stresses. The simulation is in equilibrium when the amount of water moving in or out of storage 

approaches zero.

The summed square of simulation residuals is a measure 

of how well the entire model simulates the observations from 

the field (Hill and others, 2000). The lowest layers 9–11 have 

no observations, but also have no pumping wells or other 

boundaries, and thus are inferred to have little if any change 

in head.

When the summed squares of residuals were minimized 

by scaling parameter arrays, minor changes to local parameters were used to attempt to better match simulated heads with 

observed heads. Many times, however, heads in these areas 

were not sensitive to changes in parameters until unreasonable 

values for parameters were used. In these cases the parameters were not changed, and the residuals were considered to 

be caused by local variations in parameters that could not be 

included in the model.

The recharge grid was scaled equally in all cells to 

achieve the lowest sum of squared error to preserve the 

spatial distribution of potential recharge calculated using the 

SWB computer code. The best-fit scale factor for the average 

daily SWB recharge was 0.4. Recharge is dependent on the 

hydraulic conductivity of the aquifer, and hydraulic conductivity is fixed in a range defined by the percent sand and the 

characteristics of the aquifer. Thus, the recharge appears to be 

overestimated by the SWB code (fig. 33). Therefore, recharge 

for the groundwater-flow model was set to 0.4 multiplied by 

SWB recharge. Scaling back SWB recharge is not unusual for 

this aquifer because of the small hydraulic conductivity of the 

Central Oklahoma aquifer. 

Head targets were developed from the 1986–87 waterlevel measurements (points and contours shown on fig. 9) and 

the results of calibration are shown in a map of head-target 

residuals in figure 46 and a plot of observed heads from 2009 

as compared to simulated head throughout the transient model 

in figure 47. There was no apparent horizontal or vertical 

spatial bias to model error; the maximum residual was 75 ft 

(23 m), and the minimum was -70 ft (-21 m), and the average 

residual was 5.8 ft (1.78 m). The range in water levels from 

the 1986–87 measurements was 1.5 to 177 ft below land surface with a median of 32 ft. Graphing the simulated heads with 

the observed heads in figure 47 shows that most of the points 

follow a trend line with a slope of 0.86. Substantial scatter and 

targets in shallower model layers have higher residuals than 

targets in deeper layers. Layers below the top of the model had 

simulated heads that diverged more from the observed heads, 

possibly because they were not sensitive to recharge, and 

may have been affected by pumping and vertical anisotropy 

Model layer

Head target* count

120

100

80

60

40

200

180

160

140

20

0

1 2 3 4 5 6 7 8 9 10 11

*Head targets are head observations that the groundwater-flow model is 

calibrated to.

Figure 45. Distribution of head targets by model layer (some 

head targets were used for more than one layer).
Groundwater-Flow Model 69

0 84 16 MILES

0 84 16 KILOMETERS

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

EXPLANATION

-96 to -70

-69 to -50

-49 to -30

-29 to -10

-9 to 0

1 to 10

11 to 30

31 to 50

51 to 70

71 to 75

Central Oklahoma aquifer extent

Eastern extent of Hennessey Group 

confining unit

Head target residuals (observed–simulated), 

in feet—Head targets are head observations that the groundwater-flow model is 

calibrated to

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

North

Canadian R iver

Canadian River

Figure 46. Targets and residuals for the quasi-steady-state model for 1986–87 measurements.
70 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

not resolved in the model. A histogram of the residuals for 

1986–87 measurements (fig. 48) has a median of 0.74 ft with 

a mean of 0.16 ft, and skewed positive, indicating that the 

simulated heads are slightly lower than the observed heads, 

but most residuals were between zero and 15 ft. These results 

indicate that there is random error in the model, a large component of which is related to the discretization that could not 

accommodate local variation. Hydraulic heads in the aquifer 

have been well simulated using the spatial distribution of percent sand. This result is particularly evident where a simulated 

head that was much higher than an observed head was located 

close to a simulated head that was far too low. In these cases, 

no parameter adjusted in the model could account for this error 

because this adjusted parameter would in all likelihood affect 

both targets in the same way. 

The mass-balance discrepancy of the quasi-steady-state 

model was low, 0.003 percent, indicating outflows were only 

0.003 percent greater than inflows to the model when the 

model reached convergence. The flux into and out of storage 

was negligible.

Simulation Results

The quasi-steady-state simulation provided a reasonable 

equilibrium condition for the year 1987. Flow to and from 

storage was nearly zero during the transient run, and head 

residuals were minimized as much as possible by changing 

hydraulic conductivity, vertical anisotropy, recharge, and 

streambed conductance.

Transient Simulation 1987–2009

The transient model was constructed to cover the period 

from 1987 through 2009. Each year was chosen as a stress 

period, because pumping rates for reported wells were only 

available at annual intervals. Each stress period contained 

12 equal time steps.

Figure 48. Residuals from 

the head targets in the 

quasi-steady-state model for 

1986–87 measurements (total 

number of observations was 

262).

Figure 47. Simulated as compared to observed heads in the 

quasi-steady-state model for 1986–87 measurements (total 

number of observations was 262).

Observed minus simulated head, in feet

Observation count

70

60

50

40

30

20

10

0

-105 -90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90 105 120

700 800

Observed head, in feet

Simulated head, in feet

Head observation target

EXPLANATION

900 1,000 1,100 1,200 1,300

700

800

900

1,000

1,100

1,200

1,300

Simulated head equals 0.8619 (observed head) plus 141.5

Coefficient of determination (R2) equals 0.8563
Groundwater-Flow Model 71

Simulation Inputs

The hydraulic conductivity and vertical anisotropy from 

the quasi-steady-state model were used in the transient model 

and were not adjusted for calibration. Flow into streams 

entering the model were the median flow for each year at the 

nearest upstream streamflow-gaging station as described in the 

Conceptual Flow Model section of this report. 

Calibration Targets

Head targets included all available water-level measurements for the aquifer during the period of the simulation 

(1987–2009). The HOB package allows heads to be specified for a particular year (which corresponds to a specific 

stress period), and the number of days in that year. A total of 

395 head measurements were used in the calibration process, and some head measurements spanned multiple layers. 

Because of the two synoptic water-level collection events, the 

targets are biased toward the first and last stress periods, 1987 

and 2009.

Calibration Process

Parameters adjusted included the specific yield and 

specific storage of the aquifer, and the average annual recharge 

rate. Specific yield of the aquifer materials most greatly affects 

the flow field and heads when water moves in and out of 

storage. Specific storage is similar, but is only a factor when 

stresses affect a confined system, and these values are small, 

having minor effects on calibration in most cases. Specific 

storage is the amount of water per unit volume of a saturated 

formation that is stored or expelled from storage owing to 

compressibility of the mineral matrix and pore water per unit 

change in head, and has dimensions of 1/length (Fetter, 1994). 

Specific storage is a quotient of the storage coefficient and the 

aquifer thickness.

Specific yield was adjusted during calibration by scaling the entire array, which was derived from percent sand as 

described in the Groundwater-Flow Model Hydraulic Properties section of this report. Different scaling factors were used 

to determine the lowest sum of squared residuals for the entire 

transient array. Specific storage was not derived from percent 

sand, and was not known for any part of the aquifer. To get the 

best calibration and avoid bias, a constant was used for each 

layer. This value was adjusted until the lowest sum of square 

of residuals was determined.

Recharge calculated using SWB described in the 

Recharge section of this report was resampled to a daily average for each year and held constant because of the length of 

stress periods. Grids of average daily recharge were adjusted 

by a multiplier for the entire array to preserve the spatial distribution of the relative recharge amounts calculated by SWB. 

The recharge array was scaled by different amounts until the 

lowest sum of squared residuals was determined.

The results of the calibration are plotted in a map of 

model head targets and residuals for the targets in the last 

stress period (2009) of the model run (fig. 49), a plot of 

the observed as compared to simulated heads at all targets 

(fig. 50), and a histogram of the residuals from all targets 

in the transient model (fig. 51). Figure 49 also includes an 

approximate distribution of model error, expressed as the 

absolute value of the head residuals interpolated using inversedistance weighting across the active model area. Figure 49 is a 

map of the model head error; high model head error indicates 

areas with less confidence when the model is used to run predictive simulations.

Similar to the quasi-steady-state model, the best calibration was achieved when the SWB potential recharge grid for 

each year was scaled by 0.4, indicating that SWB may be 

overestimating deep percolation volumes related to precipitation. Therefore, a notable part of the deep percolation that 

advances below the root zone does not enter the Central Oklahoma aquifer, but is lost to evapotranspiration of surface water 

while still in the soil or in Quaternary-age alluvium overlying 

or adjoining the Central Oklahoma aquifer.

Simulation Results

The transient simulation included changes in pumping 

and recharge driven by changes in groundwater pumping and 

precipitation, respectively. These stresses on the Central Oklahoma aquifer did not cause large changes in head or flow patterns and appear to be much smaller than the amount of water 

in storage and recharge. The model budget, listed in table 9, 

indicates inflows and outflows to the model. The greatest 

budget discrepancy in the model was 0.09 percent of the total 

inflow, and the total discrepancy for the entire transient model 

run was 0.03 percent. 

The total flux to and from the model during the transient 

period is shown by category of boundary condition in figure 52; positive values are inflow to the model and negative 

values are outflow from the model. The largest inflow to the 

model is recharge, with water removed from storage, seepage 

from reservoirs, and stream loss to the aquifer being a smaller 

amounts. Outflow is dominated by base flow to streams and 

pumping from wells. The aquifer was in a deficit during this 

period because inflow to the system from storage was positive (for example, water removed from storage to meet the 

total outflow).

50-Year Predictive Simulation

The purpose of the 50-year predictive simulation was 

to estimate the change in groundwater in storage if water use 

continues for 50 years at 2009 rates. The period of the predictive model was 2010 through 2059. The predictive simulation 

used the calibrated transient model previously described. 
72 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

0 84 16 MILES

0 84 16 KILOMETERS

Central Oklahoma aquifer and Hennessey boundaries

from Runkle, Christenson, and Rea, 1997

97°40’ 97°20’ 97°00’ 96°40’

36°00’

35°40’

35°20’

35°00’

PAYNE

COUNTY

KINGFISHER

COUNTY

LOGAN

COUNTY

LINCOLN

COUNTY

CANADIAN

COUNTY

SEMINOLE

COUNTY

GRADY

COUNTY

PONTOTOC

COUNTY

POTTAWATOMIE

COUNTY

MCCLAIN

COUNTY

OKLAHOMA

COUNTY

CLEVELAND

COUNTY

Deep Fork River

Cimarron River

Little River

EXPLANATION

-107 to -90

-89 to -60

-59 to -30

-29 to -10

-9 to 0

1 to 10

11 to 30

31 to 60

61 to 90

91 to 120

Head target residuals (observed–simulated), in 

feet—Head targets are head observations 

that the groundwater-flow model is 

calibrated to

Head error, in feet

High: 119

Low: 0

Extent of Central Oklahoma aquifer

Eastern extent of Hennessey Group 

confining unit

Base from Horizon Systems Corporation, 2010, and 

University of Oklahoma Center for Spatial Analysis, 2013

Universal Transverse Mercator projection, Zone 14

North American Datum of 1983

Canadian RiveCa

r

nadian River

NorthCanadian River NorthCanadian River

Figure 49. Head residuals and error for the last stress period of the transient model, 1987–2009 (error is the absolute value of 

head residuals interpolated across the active model area). 
Groundwater-Flow Model 73

Simulation Inputs

The 50-year predictive simulation used the same model 

inputs as the calibrated transient model except for recharge 

and pumping. This study did not attempt to simulate effects 

from a predictive climate model. Therefore, recharge was held 

constant at the average flux for each cell that was specified 

for the 1987–2009 time period. Pumping was held constant 

at the 2009 average daily discharge for each well at about 

47,000 acre-feet/year. 

Estimation of the effect to water levels in the aquifer by 

continuously pumping at the 2009 pumping rate for 50 years 

was achieved by running the model without any pumping, and 

then running the model with pumping. The difference in heads 

and water in storage between those model runs was used to 

estimate the effects to storage in the aquifer. 

Simulation Results

Pumping at the 2009 rate for 50 years with constant 

recharge resulted in drawdown in upland areas (fig. 53) and 

reduction of water in storage (fig. 54). The recharge rate was 

substantially higher than the total pumping rate, but water 

discharge to streams combined with pumping created a deficit 

that was met by releasing of water from storage and a decrease 

in base flow to streams. Groundwater discharge to streams 

decreased by 100,000 acre-ft/yr over the 50-year simulation 

period (fig. 54).

700 800

Observed head, in feet

Simulated head, in feet

Head observation target

EXPLANATION

900 1,000 1,100 1,200 1,300

700

800

900

1,000

1,100

1,200

1,300

Simulated head equals 0.8477 (observed head) plus 155.57

Coefficient of determination (R2) equals 0.8464

Figure 50. Graph showing simulated as compared to observed 

heads in the transient model, 1987–2009 (total number of 

observations was 395).

-105 -90 -75 -60 -45 -30 -15 15 30 45 60 75 90 105

Observed minus simulated head, in feet

Observation count

120

100

80

60

40

20

0

0 120 135

Figure 51. Residuals from 

the head targets in the 

transient model, 1987–2009

(total number of observations 

was 395).
74 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Simulation of Available Water in Storage

The calibrated transient model also was run to determine 

how much water hypothetically could be extracted from the 

Central Oklahoma aquifer over a 50-year period (scenario 1), 

and the effects of pumping the temporary state-apportioned 

rate of 2 (acre-ft/acre)/yr (scenario 2). The purpose of this 

analysis was to provide estimates of the amount of water in 

storage in the Central Oklahoma aquifer.

Methods

The two scenarios used to determine the amount of water 

in storage is based on the concept of equal proportionate share 

described in the Introduction section in this report—the same 

rate of water extraction for the entire aquifer—which approximates a fully developed aquifer for future water use. The first 

scenario determined the discharge rate at which wells placed 

in every model cell would have to be pumped so that just 15 ft 

(4.57 meters) or less of saturated thickness remained in 50 percent of the aquifer area (50 percent of the model cells) after 

50 years. The second scenario was to pump 2 (acre-ft/acre)/yr 

from every model cell, and to determine the time at which 

one-half of the aquifer area was reduced to 15 ft or less of 

saturated thickness.

Table 9. Water budget and inflow-outflow discrepancy for the transient model.

Stress 

period Year Inflow to model in thousand acre-feet per year Outflow from model in thousand acre-feet per year

Storage Lakes Recharge Streams Wells Storage Lakes Streams Wells

1 1987 9.173 13.285 408.992 76.741 0.123 3.354 14.030 446.784 44.138

2 1988 112.931 13.488 292.778 79.235 0.111 16.453 13.750 423.290 44.132

3 1989 116.013 13.633 261.385 78.439 0.100 15.448 13.245 400.351 40.359

4 1990 54.295 13.633 357.563 78.695 0.098 38.031 13.224 413.220 39.586

5 1991 63.127 13.594 333.446 79.324 0.091 31.522 13.290 403.972 40.707

6 1992 53.684 13.634 340.810 79.297 0.086 31.779 13.291 402.561 39.878

7 1993 36.065 13.557 390.168 78.235 0.085 48.585 13.318 415.984 40.051

8 1994 65.470 13.595 317.364 77.721 0.081 22.216 13.167 396.420 42.400

9 1995 81.709 13.735 280.334 76.937 0.076 11.789 12.898 381.662 46.473

10 1996 135.698 13.987 202.768 77.836 0.070 11.953 12.408 356.703 49.111

11 1997 101.789 14.006 235.356 75.638 0.064 13.421 12.020 354.946 46.470

12 1998 46.858 13.908 346.039 76.616 0.066 43.608 12.228 376.853 50.661

13 1999 75.843 13.903 284.885 75.577 0.064 19.119 12.308 369.357 49.457

14 2000 26.610 13.867 375.618 76.533 0.064 44.378 12.519 385.062 50.523

15 2001 80.430 13.844 277.160 73.161 0.065 14.396 12.493 367.863 50.441

16 2002 81.061 13.974 257.254 76.406 0.056 11.373 12.157 356.851 48.203

17 2003 76.839 14.077 258.324 76.115 0.054 8.466 11.823 353.150 51.949

18 2004 177.958 14.395 113.036 75.688 0.051 4.985 11.264 317.155 47.311

19 2005 24.034 14.228 387.411 75.558 0.052 74.771 11.398 361.496 53.063

20 2006 137.364 14.334 163.966 76.854 0.049 13.090 11.225 322.045 45.981

21 2007 163.527 14.622 113.953 75.200 0.043 6.877 10.557 301.422 48.359

22 2008 11.518 14.347 464.839 76.665 0.051 144.522 11.038 364.617 47.265

23 2009 100.172 14.270 208.172 74.594 0.047 11.201 11.124 327.616 47.418
Groundwater-Flow Model 75

Thousands of acre-feet per day

Inflow

EXPLANATION

Outflow

30

20

10

0

-10

-20

-30

Storage Lakes

Recharge

Streams Wells

Total

Groundwater-flow model boundary

Figure 52. Water budget for the 

transient model showing total 

flux for the period 1987–2009, by 

boundary condition.

Drawdown, in feet

EXPLANATION

9.1

7.8

2.6

6.5

1.3

3.9

5.2

0

N

Figure 53. Drawdown in the Central Oklahoma aquifer numerical 

model after 50 years with 2009 pumping rates compared to the 

aquifer with no pumping.

These scenarios are somewhat unrealistic because though 

hydraulic conductivity varies throughout the aquifer and there 

is substantial vertical anisotropy, the lower model boundary is 

not a no-flow boundary in reality. Under these pumping conditions, some upward migration of saline water would result, but 

this migration was not modeled for this study. Determination 

of the degree to which saline water upwardly migrates was 

beyond the scope of this study. 

Simulation Inputs

For scenario 1, the transient model was run for a period 

of 50 years with a hypothetical well in each model cell and 

pumped from every active layer at that location. The same 

pumping rate was assigned to each well, and the rate was 

increased incrementally for a number of model runs until the 

number of cells with a saturated thickness of 15 ft (4.57 m) or 

less equaled 50 percent of the model gridded area. The MNW2 

(Multi-Node Well) package allows each well to stop pumping 

from a cell if that cell dries out during the transient model run.

For scenario 2, the calibrated transient model was run 

with a multinode well in each cell that was set to discharge 

2 (acre-ft/acre)/yr for more than a maximum period of 

50 years. The saturated thickness was periodically recorded 

during the 50-year run to determine the year in which one-half 

of the cells were below 15 ft of saturated thickness.
76 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Storage coefficient and specific yield affect the amount of 

water in storage and were increased and decreased by 10 percent in both scenarios. Storage coefficient and specific yield 

were adjusted using the same method described in the Sensitivity Analysis section of this report. 

Simulation Results

For scenario 1, the pumping rate at all cells that reduced 

the saturated thickness in one-half of the cells to or below 15 ft 

(4.57 m) after 50 years was approximately between 1.1 and 

1.5 (acre-ft/acre)/yr using 10 percent increase and decrease in 

specific yield. (fig. 55). Simulated heads in scenario 1 indicate 

that water levels decreased and some model cells went dry 

first in the eastern part of the aquifer where aquifer thickness 

is less than 300 ft (fig. 56). The last area of the aquifer with 

substantially decreased water levels was where the aquifer is 

the thickest, which is north of Moore near Tinker Air Force 

Base (see fig. 1 for location). During the 2010–59 depletion 

scenario, drawdown also was observed below the Hennessey 

Group (confining unit) in the western part of the aquifer. 

This drawdown below the Hennessey is not visible on fig. 56 

because of the aspect of the maps. Groundwater in the Hennessey Group did not drawdown because the low transmissivity of the Hennessey causes groundwater to be retained in the 

shale and there was no pumping simulated from the Hennessey Group. Throughout this scenario, pumped water was 

coming from storage in the aquifer. 

The results of scenario 2 are shown in figure 57. The 

aquifer was estimated to be 50 percent depleted after between 

Thousands of acre-feet per year

150

100

50

-150

0

-100

-50

-200

200

250

300

-250

-300

Recharge

EXPLANATION

Flow from storage

2009 pumpage

Out to streams (base flow)

Year

0 5 10 15 20 25 30 35 40 45 50

Figure 54. 50-year 

predictive model budget 

showing recharge, water 

removed from storage, 

groundwater pumpage, 

and base flow to streams 

assuming constant recharge 

and pumping at estimated 

2009 rates (50-year predictive 

simulation).
Groundwater-Flow Model 77

35 and 41 years of pumping 2 (acre-ft/acre)/yr using 10 percent increase and decrease in specific yield. This analysis 

indicates that scenario 2 pumping rate of 2 (acre-ft/acre)/yr is 

not sustainable for more than 41 years if every landowner with 

a potential well in each acre in the Central Oklahoma aquifer 

exercised their temporary right to pump at that rate.

Sensitivity Analysis

A sensitivity analysis was performed on the model, which 

determines the sensitivity of the calibrated simulation to 

changes in calibration parameters (hydraulic conductivity, specific yield, specific storage, vertical anisotropy, and recharge). 

The sensitivity of model heads to changes in these parameters 

is thus important because the uncertainty in these parameters 

could have an important effect on the simulation results.

Methods

All observations were used with the transient simulation for the sensitivity analysis because the quasi-steady-state 

model was run as part of the transient simulation. The parameters used in the transient model were the hydraulic conductivity, the specific yield, specific storage, vertical anisotropy, 

and recharge. Each parameter was scaled across the model by 

multiplying the two-dimensional array for each layer or the 

recharge for each year by a constant, reducing the multiplier 

by 10 percent and 20 percent, and increasing the multiplier 

by 10 percent and 20 percent. For each model run, the average change in head at observation points (from the calibrated 

model) was recorded. 

Sensitivity Analysis Results

Simulated hydraulic head at head targets in the transient 

simulation responded to changes in hydraulic conductivity, 

specific yield, vertical anisotropy, and recharge and are shown 

in figure 58, and listed in table 10. The model was most sensitive to recharge, as a 20-percent decrease in recharge caused 

a 2.58-ft (0.79-m) drop in average head, and a 20-percent 

increase in recharge caused a 2.56-ft (0.78-m) rise in average head. The average change in head was inversely proportional to changes in hydraulic conductivity, with a 20-percent 

decrease in hydraulic conductivity resulting in a 1.24-ft (0.38-

m) rise in average head; a 20-percent increase in hydraulic 

conductivity caused a 0.85-ft (0.26-m) drop in average head. 

The model was only slightly sensitive to specific yield, with a 

20-percent decrease in specific yield producing a 0.33-ft (0.10-

m) drop in average head, and a 20-percent increase in specific 

yield causing a 0.25-ft (0.08-m) increase in average head. A 

20-percent decrease in vertical anisotropy caused 0.016-ft 

(0.005-m) rise in head , and a 20-percent increase in vertical 

anisotropy caused a 0.013-ft (0.004-m) drop in average head.

Small values of sensitivity resulting from changes in 

storage were most likely related to relatively constant pumping rates, which were smoothed even further by the availability of annual pumping data rather than seasonal or monthly, 

and a lack of transient head observations that would record 

seasonal or monthly head changes induced by aquifer stresses. 

Pumping data were only available in annual totals, which 

were used in the model as daily average pumping. Thus, with 

small stresses, water was not moved in and out of storage 

sufficiently to cause simulated water levels to be sensitive to 

storage parameters.

Equal-share continuous pumping rate [(acre-feet per acre) per year]

Percentage of basin with less than or equal to

15 feet saturated thickness

60

50

40

30

20

70

10

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

10-percent decrease in Sy (specific yield)

EXPLANATION

50-year transient model

10-percent increase in Sy

0

0

Figure 55. Percent of aquifer 

that had less than or equal to 

15 feet of saturated thickness 

at various pumping rates at 

the end of a 50-year period 

(scenario 1).
Head altitude, in feet

EXPLANATION

1,200

1,030

860

520

690

350

A. 1 Year B. 25 Years

C. 50 Years

N

N

N

78 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Figure 56. Central Oklahoma aquifer altitude of the water table (head) 

after 1, 25, and 50 years of pumping for the 2009–58 depletion-scenario 

simulation. (Model cells that go dry between each time step disappear 

from the surface of the model. Areas not depleted, in red, are beneath 

lakes and rivers).

Percentage of basin with less than or equal to

15 feet saturated thickness

60

50

40

30

20

70

10

10-percent decrease in Sy (specific yield)

EXPLANATION

Pumping 2 (acre-feet per acre) per year

10-percent increase in Sy

0

Years elapsed

15 20 25 30 35 40 45 50 55

Figure 57. Percent of 

aquifer that had less than or 

equal to 15 feet of saturated 

thickness at a pumping rate of 

2 (acre-feet per acre) per year 

(scenario 2).
Model Simplifications, Assumptions, and Limitations 79

Table 10. Sensitivity of simulated heads to changes in parameters in the transient model.

Parameter Average change in head, in feet

20-percent decrease 10-percent decrease 10-percent increase 20-percent increase

Horizontal hydraulic conductivity 1.24 0.63 -0.42 -0.85

Specific yield -0.33 -0.16 0.12 0.25

Vertical anisotropy 0.016 0.006 -0.006 -0.013

Specific storage 0.003 0.003 0.0003 0.003

Recharge -2.58 -1.29 1.28 2.56

Recharge

EXPLANATION

Horizontal hydraulic conductivity

Specific yield

Percent change in parameter

Mean head change, in feet

3

2

-2

1

-1

0

-3

-25 -20 -15 -10 -5 0 5 10 15 20 25

Figure 58. Changes in simulated heads at head targets in the transient model with percent changes in selected 

model parameters.

Model Simplifications, Assumptions, 

and Limitations

All models are generalizations of the systems represented 

and are based on assumptions with inherent limitations. The 

model presented herein is a regional-scale model that uses 

relatively large cells, and only includes large bodies of surface 

water. Thus, the model is limited by the spatial definition of 

the model grid. The model is limited in how detailed the interactions between the Central Oklahoma aquifer and surface 

water can be portrayed. This model also does not discretely 

distinguish between the alluvium and terrace deposits along 

the Cimarron, North Canadian, and Canadian Rivers and 

bedrock parts of the Central Oklahoma aquifer. These deposits 

are in the model and are represented by increased horizontal 

conductivity where detected by logs, such as along the North 

Canadian River east of the extent of the Hennessey Group. 

However, no water budget can be created by this model to 

estimate the flux of water between the alluvium and terrace 

aquifers and the Central Oklahoma aquifer.

The initial model run was a long-duration transient model 

that was run until there was little change in water in storage, 

indicating that the flow system was in equilibrium with the 

inflows and outflows defined for 1987. This is a quasi-steadystate model and there may be some differences between this 

model and a model run in steady-state mode. 

The lithology of the Central Oklahoma aquifer is highly 

variable, with no continuous internal confining units or conductive zones. Vertical changes in hydraulic conductivity are 
80 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

much more variable than can be captured in 100-ft (30.48-m) 

layers. Thus, the model layers are constructed as an approximation of a complex natural system and the variation in 

conductivity was estimated using the vertical anisotropy in 

hydraulic conductivity. These simplifications limit what the 

model can simulate with regard to specific well drawdown and 

vertical gradients near wells or well fields. This model design 

assumes that the percent of sand in the formations as estimated 

from gamma-ray and lithologic logs was a reasonable starting 

point for estimating the horizontal hydraulic conductivity of 

the aquifer. 

The reported groundwater-use data provided by the 

OWRB have several assumptions and estimated values. The 

method used to determine the domestic groundwater use was 

based on population changes. This method has limitations in 

the assumption that the rate of change in population served 

by domestic wells changes similarly to the rate of change 

in total population. In addition, exact amounts of reported 

groundwater use are unknown because wells are not metered 

or uses logged. 

The flow model was calibrated to water-level observations. There was no attempt to calibrate to streamflow observations, which limits the use of this model to simulate daily or 

seasonal streamflows or effects to daily or seasonal streamflows. However, the model can be used to simulate long-term 

effects of pumping on water levels and annual streamflows.

To simulate the equal proportionate share approach with 

the model, a well must be placed in every cell and pumped at 

equal rates. Model cell sizes were 3,280 ft by 3,280 ft (1 km 

by 1 km), so by placing a well in each cell, the equal proportionate share of 2 (acre-ft/acre)/yr would indicate that the wells 

would have to pump at a rate of 494 (acre-ft/1 square-km 

model cell)/yr. The assumption for the depletion scenario is 

that wells completed in the aquifer could actually withdraw 

this large amount of water. The depletion scenario does not 

take into account low hydraulic conductivities that would 

prevent large amounts of water from being pumped. The 

depletion scenario pumps at high rates until there is 15 ft of 

saturated thickness, a point at which the pumping shuts off. 

In addition, with only 15 ft of saturated thickness remaining in some areas, saline water would most likely upcone or 

migrate into the freshwater zone (aquifer). This model does 

not account for potential saline migration that might limit the 

extent of freshwater or decrease the amount of freshwater.

The model presented in the investigation described in this 

report considers the base of freshwater to be a no-flow boundary. This approach could be problematic if groundwater from 

the aquifer were used at a high rate (depletion) near the freshwater/saline interface that could cause saline water to migrate 

upgradient near the base of freshwater or horizontally near the 

western extent of freshwater near the freshwater/saline interface. This model does not account for potential saline-water 

migration that might limit the extent of freshwater or decrease 

the amount of freshwater. The potential of saline-water migration could be modeled as part of future investigations for the 

aquifer, but would require some additional data collection and 

geochemical and variable-density modeling. 

Summary

The Central Oklahoma (Garber-Wellington) aquifer 

underlies about 3,000 square miles of central Oklahoma and 

water from the aquifer is used for public, industrial, commercial, agricultural, and domestic supply of water. The study area 

for this investigation was the extent of the Central Oklahoma 

aquifer. With the exception of Oklahoma City, all of the 

larger communities in central Oklahoma rely either solely or 

partly on groundwater from this aquifer. The Oklahoma City 

metropolitan area, incorporating parts of Canadian, Cleveland, 

Grady, Lincoln, Logan, McClain, and Oklahoma Counties, has 

a population of approximately 1.2 million people, estimated 

from the 2010 census and is expected to increase by 20 percent from 2000 to 2030. Growing cities need to locate reliable 

water supplies to sustain their projected populations. As areas 

are developed for groundwater supply, increased groundwater 

withdrawals may cause decreases in long-term aquifer water 

storage. The U.S. Geological Survey, in cooperation with the 

Oklahoma Water Resources Board, investigated the hydrogeology and simulated groundwater flow in the aquifer using a 

numerical groundwater-flow model. 

The purpose of this report is to describe an investigation 

of the Central Oklahoma aquifer that included analyses of the 

geology, hydrology, hydrogeologic framework of the aquifer, 

and construction of a numerical groundwater-flow model. The 

groundwater-flow model was used to simulate groundwater 

levels and for water-budget analysis. The calibrated transient 

model was used to evaluate changes in groundwater storage 

associated with increased future water demands.

The Central Oklahoma aquifer consists of Quaternaryage alluvium and terrace deposits and the Permian-age Garber 

Sandstone, Wellington Formation, and Chase, Council Grove 

and Admire Groups. Groundwater flows between these geologic units and many wells are completed in the study area in 

the Quaternary-age and Permian-age units. Alluvium and terrace deposits in the study area are composed of lenticular beds 

of unconsolidated or loosely consolidated clays, silt, sand, 

and gravel and are found along all of the major streams. In the 

study area, the Permian-age Garber Sandstone and Wellington 

Formation have similar lithologies and differentiating the two 

in surface outcrops and in the subsurface by geophysical logs 

or core samples is difficult. The investigation described in this 

report focuses more on the Permian-age units because water 

in the Quaternary-age alluvium and terrace is volumetrically 

a small fraction of water in the Permian-age units. The Garber 

Sandstone and Wellington Formation consist of cross-bedded, 

fine-grained sandstone with shale or mudstone interbedded. 

Stratigraphically below the Wellington Formation are the 

Chase, Council Grove, and Admire Groups that are composed of cross-bedded, fine-grained sandstone, shale, and thin 
Summary 81

limestone. The Permian-age Hennessey Group overlies the 

western part of the Central Oklahoma aquifer and consists of 

interbedded red shale, clay, and some siltstone or fine-grained 

sandstone. The Hennessey Group acts as a confining layer 

because of its small transmissivity.

Analysis of regional groundwater flows indicates that 

groundwater in the shallow, local flow systems discharges to 

nearby streams and the rate of flow and flux of water are greatest in these local flow systems. Flow in the deeper part of the 

aquifer is slower and flowlines are longer than in the shallow, 

local flow systems. In this deeper flow system, groundwater 

flows under small streams to discharge primarily to the Deep 

Fork and Little River. Flow in the Central Oklahoma aquifer 

is slowest in the confined part of the Garber Sandstone and 

Wellington Formation and in the less transmissive parts of the 

unconfined flow system, which includes part of the Chase, 

Council Grove, and Admire Groups. Groundwater in the confined part of the aquifer comes from recharge primarily from 

a small area of the unconfined part of the aquifer near 35°23ʹ 

latitude and 97°23ʹ longitude as seen in the mound of water on 

the potentiometric-surface maps.

Water levels were measured in 280 wells as part of this 

investigation between February 17, 2009, and March 13, 2009. 

The 2009 water levels, in feet below land surface, ranged 

from 3.1 to 233.7, with a median of 35.8 feet. Water levels 

were measured in more than 300 wells between December 22, 

1986, and April 24, 1987, and water levels, in feet below land 

surface, ranged from 1.5 to 177 with a median of 32 feet. 

Water levels from 2009 were compared to water levels from 

1986–87. Wells in which there was a measurement for both the 

1986–87 and 2009 time periods were compared (169 wells). A 

statistical test was done to determine if the 2009 water levels 

changed significantly from the 1986–87 water levels. This 

statistical test indicated that the 2009 depth-to-water measurements have increased from the 1986–87 depth-to-water 

measurements, and this increase is statistically significant. 

The difference in the median depth-to-water measurements 

for the two time periods was 3.75 feet. A water level decline 

of 3.75 feet multiplied by the area of the aquifer (3,000 square 

miles), multiplied by the minimum and maximum porosity expected for this aquifer (14 to 30 percent) resulted in a 

calculated change of water in storage from 1986–87 to 2009 

that ranged from 1,008,000 to 2,160,000 acre-feet, assuming all water from aquifer storage came from the unconfined 

conditions. This loss in storage from the 1986–2009 period, 

when averaged per year, resulted in approximately 44,000 to 

94,000 acre-ft/yr.

Water levels from wells in the Oklahoma Water 

Resources Board Mass Measurement Program and the 

U.S. Geological Survey National Water Information System databases indicate that water levels in shallow wells are 

affected by barometric-pressure changes, precipitation, and 

pumping from nearby shallow wells. Water levels in deeper 

wells in the aquifer had minimal response to precipitation and 

barometric-pressure changes, but respond to pumping from 

nearby deep wells.

Groundwater-use data were compiled and included public 

water suppliers, irrigators, industry, and businesses. Including 

estimated unreported groundwater use, average groundwater 

use from 1967 to 2008 was about 37,367 acre-feet/year with 

public-water supply consuming 23,367 acre-feet/year, or about 

63 percent of the average annual reported and estimated unreported groundwater use. Domestic use was estimated by using 

the 1990 census long-form data and population change compared to 1980, 2000, and 2010 census data. Average estimated 

domestic groundwater use from the aquifer from 1980 to 2010 

was about 13,752 acre-feet/year.

The major streams flowing across the Central Oklahoma 

aquifer are the Cimarron River, North Canadian River, and 

Canadian River. The flows in these streams are regulated by 

dams and increased by releases from sewage-treatment plants. 

Average daily mean streamflow in the study area ranged from 

55.8 cubic feet/second at streamflow-gaging station 07230000 

Little River below Lake Thunderbird near Norman, Okla., for 

the period 1966–2009 to 255 cubic feet/second at streamflowgaging station 07242380 Deep Fork at Warwick, Okla., for 

the period 1988–2009. Discharges measured in January 2009 

in the study area during base-flow conditions ranged from 

0.23 cubic feet/second at streamflow-gaging station 07241570 

Deer Creek near Newalla, Okla., to 4.46 cubic feet/second 

at streamflow-gaging station 07242378 Captain Creek near 

Wellston, Okla.

Recharge rates to the Central Oklahoma aquifer were 

estimated or calculated using a basin-scale base-flowdischarge method, a basin-scale recession-curve displacement (Rorabaugh) method, and a regional-scale method using 

the Soil-Water Balance code. Recharge rates calculated for 

the 2009 measurements ranged from 0.20 inches per year at 

Deer Creek near Newalla, Okla., streamflow-gaging station 

to 2.02 inches per year at Wildhorse Creek at Luther, Okla., 

streamflow-gaging station. Recharge rates calculated using 

the Rorabaugh method varied from 1.3 inches per year at the 

Little River near Tecumseh, Okla., to 4.1 inches per year at the 

Deep Fork near Arcadia, Okla. Average annual recharge from 

the Soil-Water Balance code for the gridded aquifer area for 

the 1987–2009 period was 4.6 inches. However, during model 

calibration, a scaling factor of 0.4 was applied to Soil-Water 

Balance recharge, which resulted in 1.84 inches per year of 

average annual recharge values for the gridded aquifer area for 

the 1987–2009 period.

Aquifer hydraulic properties were estimated from 

lithologic and geophysical well logs, and were measured at 

a site where a multiple-well aquifer test was completed for 

this investigation. Transmissivity from the aquifer test at a 

production well near Norman, Okla., determined as part of this 

study, was 220 square feet per day. Using the screened interval 

of 90 feet in the production well, the geohydrologic-unit 

hydraulic conductivity was 2.4 feet per day. Analytical model 

solutions indicated a leaky confined aquifer. The storage 

coefficient from the analytical solution was 0.0013. This storage coefficient indicates that, even though the Central Oklahoma aquifer extends to land surface with a potentiometric 
82 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

surface below the top of the Central Oklahoma aquifer, the 

groundwater system acts as a confined system due to laterally 

extensive interbedded mudstone and large contrasts in vertical 

hydraulic conductivity. 

The objective of developing the hydrogeologic framework of the Central Oklahoma aquifer system was to provide a 

three-dimensional representation of the lithologic variability of 

aquifer materials at a scale that captured the regional controls 

on groundwater flow for input to the groundwater-flow model. 

Lithologic logs and gamma-ray logs were converted to percent 

sand, which was used as a proxy in the estimation of initial 

hydraulic conductivity of the aquifer for the groundwater-flow 

model. Percent sand was interpolated between logs to spatially 

distribute percent sand across the study area. 

Approximately 11,000 lithologic logs were used for 

the percent-sand analysis. Most of the lithologic logs maintained by the Oklahoma Water Resources Board are from 

shallow, domestic-use wells, which typically only penetrate 

to approximately 300 feet below land surface. Therefore, 

lithologic logs tend to over-represent the shallow aquifer and 

under-represent the deep aquifer. To simplify and standardize 

the lithologic logs, the lithologic descriptions for each depth 

interval were reclassified into one of four categories that were 

used to estimate the percent sand of each interval. Lithology 

was classified into four lithologic categories: mud, sandy mud, 

muddy sand, and sand, which can be conceptually simplified 

and quantified as a continuous series of textures from 0 percent sand (mudstone) to 100 percent sand (sandstone). As the 

Central Oklahoma aquifer uniformly consists of very fine to 

fine grained sand and moderately well to well sorted grains, 

percentages of sand were assumed to be linearly distributed 

across the four lithologic categories. Each lithologic category 

was assigned a percent sand using a multiplier. For example, 

the sand category was assigned a bin percent sand range of 

100 to 75 percent sand and a midpoint of 87.5 percent sand. 

The midpoint of each bin was used as a percent-sand multiplier because the midpoint was considered an average percent 

sand for each bin. The sand multiplier was 87.5 percent sand, 

the muddy sand multiplier was 62.5 percent sand, the sandy 

mud multiplier was 37.5 percent sand, and the mud multiplier 

was 12.5 percent sand. The percent sand was summarized into 

a total percent sand for each lithologic log using a weighted 

average of the interval thickness. 

Approximately 600 gamma-ray logs also were used for 

the percent-sand analysis. Most of the gamma-ray logs used 

for the analysis were from public-supply wells, and some oil 

and gas wells. Depths of the logs ranged from approximately 

300 to 1,000 feet below land surface. The approach to classify percent sand from the gamma-ray data assumed that each 

gamma-ray log included at least one sand (87.5 percent sand) 

and at least one mud (12.5 percent sand). A sand was determined to be the minimum intensity on the gamma-ray log and 

a mud was determined to be the maximum intensity on the 

gamma-ray log. A sand, or minimum intensity gamma-ray, 

was assigned a value of 87.5 percent sand and a pure mud, 

or maximum intensity gamma-ray, was assigned a value of 

12.5 percent sand. All of the gamma-ray values between the 

minimum and maximum were scaled relative to the position 

of the value between the 12.5 and 87.5 percent sand. This 

scaling technique was independent of the units of measure and 

normalized the gamma-ray logs to make the logs more comparable. Gamma-ray data were stored at 0.5-foot depth intervals 

and for consistency were summarized in the same manner 

as the lithologic-log data, with the same 4 bins of percent 

sand categories and the same maximum (87.5 percent) and 

minimum percent sand (12.5 percent). All data points were 

assigned one of four multipliers corresponding to the midpoint 

of each bin. Next, these multipliers were summarized for each 

log by using a weighted average of the interval thickness. 

To spatially distribute the percent sand for the hydrogeologic framework, the data points of lithologic-log percent 

sand and gamma-ray log percent sand were incorporated into 

a Geographic Information System. For spatial interpolations at 

different depth intervals, each lithologic log was represented 

by a single percent sand value. However, for gamma-ray 

logs, multiple percent-sand values at 0.5-foot intervals were 

averaged for each interval thickness to be interpolated. An 

inverse distance-weighted interpolation method was used to 

estimate percent sand for locations without logs. The gammaray percent sand and the lithologic-log percent sand were used 

to interpolate percent sand between log locations, but preference was given to gamma-ray-derived percent sand because 

gamma-ray logs were more detailed with depth. 

A MODFLOW groundwater-flow model was developed 

to simulate groundwater flow and build water budgets in the 

Central Oklahoma aquifer. The Central Oklahoma aquifer was 

simulated using a grid comprised of 3,280-feet by 3,280-feet 

(1-kilometer by 1-kilometer) cells and 11 horizontal layers, 

each 100-feet thick (30.48 meters). The quasi-steady-state 

model was run to simulate the 1987 calendar year with 

equilibrium in flow and minimal changes in storage. Initial 

hydraulic conductivity used for the groundwater-flow model 

ranged from 0.33 to 3.3 feet per day and was estimated for 

each model cell using the percent sand from the hydrogeologic framework. The quasi-steady-state model was calibrated 

to a subset of the 1986–87 water levels. Parameters that 

were adjusted to affect quasi-steady-state model calibration 

included hydraulic conductivity, vertical anisotropy, and 

recharge. Recharge for the groundwater-flow model was set 

to 0.4 multiplied by the Soil-Water Balance recharge estimate. 

There was no apparent horizontal or vertical spatial bias to 

model error and the residuals indicated that the simulated 

heads are slightly lower than the observed heads, but most 

residuals were near zero. These results indicate that there is 

random error in the model, a large component of which is 

related to the discretization that could not accommodate local 

variation in flow properties. The hydraulic heads in the aquifer 

have been well simulated using the spatial distribution of 

percent sand. 

The transient groundwater-flow model was constructed to 

represent the period from 1987 through 2009. Because pumping rates for public water-supply wells were only available 
Selected References 83

on annual intervals, each year was chosen as a stress period. 

The transient model was calibrated to all available water-level 

measurements for the aquifer during the period of the simulation (1987–2009). Parameters adjusted during the transient 

calibration process included the specific yield and specific 

storage of the aquifer, and the average annual recharge rate. 

The largest flux to the model is recharge, with water removed 

from storage, seepage from reservoirs, and water lost from 

the aquifer to streams being approximately equal to recharge. 

Outflow was dominated by base flow to streams and pumping 

from wells. Water was removed from storage to meet the total 

outflow which indicates the aquifer was in a deficit (losing 

water) during this period.

The purpose of the 50-year predictive simulation was 

to estimate the change in groundwater in storage if water 

use continues for 50 years at 2009 rates. The 50-year predictive simulation used the same model inputs as the calibrated 

transient model except for recharge and pumping. Because 

this study did not attempt to simulate effects from a predictive 

climate model, recharge was held constant at the average flux 

for each cell that was specified for the 1987–2009 time period. 

Pumping was held constant at the 2009 average daily discharge for each well. To estimate the effects to water levels in 

the aquifer by the 2009 pumping rate continuing for 50 years, 

the model was run without any pumping, and then run with 

pumping. The difference in hydraulic heads and water in storage between those model runs was used to estimate the effect 

of pumping to storage in the aquifer. Pumping at the 2009 rate 

for 50 years with constant recharge resulted in drawdown in 

upland areas and reduction of water in storage. The recharge 

rate was substantially larger than the total pumping rate, but 

water discharge to streams combined with pumping created a 

deficit that was met by releasing water from aquifer storage 

and decreasing base flow to streams. 

The calibrated transient model also was run to determine 

how much water could hypothetically be extracted from the 

Central Oklahoma aquifer in a 50-year period (scenario 1), 

and the effects of pumping the temporary state-apportioned 

rate of 2 (acre-feet/acre)/year (scenario 2). The purpose of 

this analysis was to provide estimates of the amount of water 

in storage in the Central Oklahoma aquifer. These scenarios 

were used to simulate the equal proportionate share by placing 

a well in every model cell and pumping at a constant rate. 

The first scenario determined the discharge rate at which 

wells placed in every model cell would have to be pumped so 

that just 15 feet (4.57 meters) or less of saturated thickness 

remained in 50 percent of the aquifer area (50 percent of the 

model cells) after 50 years. The second scenario was to pump 

2 (acre-feet/acre)/year from every model cell, and to determine 

the time at which one-half of the aquifer area was reduced 

to 15 feet or less of saturated thickness. For scenario 1, the 

pumping rate at all cells that reduced the saturated thickness 

in one-half of the cells to or below 15 feet (4.57 meters) after 

50 years was between 1.1 and 1.5 (acre-feet/acre)/year. The 

results of scenario 2 indicate the aquifer would be 50 percent depleted after between 35 and 41 years of pumping 

2 (acre-feet/acre)/year using 10 percent increase and decrease 

in specific yield. This analysis indicates that scenario 2 pumping rate of 2 (acre-feet/acre)/year is not sustainable for more 

than 41 years if every landowner with a potential well in each 

acre in the Central Oklahoma aquifer exercised their temporary right to pump at that rate.

Selected References

Abbott, B.N., 2005, Subsurface geology of arsenic-bearing 

Permian sedimentary rocks in the Garber-Wellington interval of the Central Oklahoma aquifer, Cleveland County, 

Oklahoma: Master’s thesis, Oklahoma State University, 

p. 112.

Agarwal, R.G., 1980, A new method to account for producing time effects when drawdown type curves are used to 

analyze pressure build up and other test data: Presented 

at the Society of Petroleum Engineers Annual Technical 

Conference and Exhibition, Sept.21–24, Dallas, Texas, SPE 

paper 9289.

Babbitt, H.E., and Doland, J.C., 1955, Water supply and engineering: New York, McGraw-Hill, 608 p.

Becker, C.J., Overton, M.D., Johnson, K.S., and Luza, K.V., 

1997, Geologic and hydraulic characteristics of selected 

shaly geologic units in Oklahoma: U.S. Geological Survey 

Water-Resources Investigations Report 96–4303, 25 p.

Benham Engineering Company, Inc., and Black & Veatch, 

1967, Comprehensive report and master plan of water 

works improvements for the city of Oklahoma City, 

Oklahoma: 183 p.

Bingham, R.H., and Moore, R.L., 1975, Reconnaissance of the 

water resources of the Oklahoma City quadrangle central 

Oklahoma: Oklahoma Geological Survey Hydrologic 

Atlas 4, 4 sheets, scale 1:250,000.

Breit, G.N., 1998, The diagenetic history of Permian rocks 

in the Central Oklahoma Aquifer: U.S. Geological Survey 

Water-Supply Paper 2357–A, p. 45–67.

Breit, G.N., Rice, C.A., Esposito, K.J., and Schlottmann, J.L., 

1990, Mineralogy and petrography of Permian rocks in the 

Central Oklahoma Aquifer: U.S. Geological Survey OpenFile Report 90–678, 50 p.

Bureau of Reclamation, 1958, Norman Project, Oklahoma: 

House Document 420, 85th Congress, 2nd Session, 146 p.

Butler, J.J., Jin, W., Mohammed, G.A., and Reboulet, E.C., 

2011, New insights from well responses to fluctuations in 

barometric pressure: Ground Water, v. 49, no. 4, p. 525–533.
84 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Carr, J.E., and Marcher, M.V., 1977, A preliminary appraisal 

of the Garber-Wellington aquifer southern Logan and northern Oklahoma Counties Oklahoma: U.S. Geological Survey 

Open-File Report 77–278, 23 p.

C.H. Guernsey & Co., 1959, Additional water supply, proposed surface-water reservoir on Little River, Norman 

Project, for cities of Norman, Midwest City, Del City: 

Oklahoma City, C.H. Guernsey & Co.

Christenson, S.C., and Carpenter, L.K., 1992, Ground-water 

quality of the central Oklahoma (Garber-Wellington) 

Aquifer conference; proceedings: U.S. Geological Survey 

Open-File Report 92–116, 24 p.

Christenson, S.C., Morton, R.B., and Mesander, B.A., 1992, 

Hydrogeologic maps of the Central Oklahoma Aquifer, 

Oklahoma: U.S. Geological Survey Hydrologic Investigations Atlas HA–724, 3 sheets, scale 1:250,000.

Domenico, P.A., and Schwartz, F.W., 1998, Physical and 

chemical hydrogeology (2d): New York, N.Y., John Wiley 

& Sons, Inc., 528 p.

Driscoll, F.G., 1986, Groundwater and Wells (2d ed.): St.Paul, 

Minn., Johnson Filtration Systems, 1,089 p.

Esri, 2007, Implementing Inverse Distance Weighted 

(IDW), Release 9.2, accessed on January 20, 2012, 

at http://webhelp.esri.com/arcgisdesktop/9.2/index.

cfm?TopicName=Implementing%20Inverse%20

Distance%20Weighted%20(IDW).

Fetter, A.W., 1994, Applied hydrogeology (3d ed.): Upper 

Saddle River, N.J., Prentice-Hall, 691 p.

Gates, M.M., Marsh, J.H., and Fryberger, J.S., 1983, Technical considerations for the development plan of the GarberWellington aquifer: Norman, Oklahoma, Engineering 

Enterprises, Inc., v. 1, p. IV–33. 

Gesch, D.B., 2007, The National Elevation Dataset, in Maune, 

David, ed., Digital elevation model technologies and applications: The DEM Users Manual, 2nd Edition: Bethesda, 

Maryland, American Society for Photogrammetry and 

Remote Sensing, p. 99–118.

Gould, C.N., 1905, Geology and water resources of Oklahoma: U.S. Geological Survey Water Supply and Irrigation 

Paper 148, 178 p.

Gromadzki, G.A., 2004, Outcrop-based gamma-ray characterization of arsenic-bearing lithofacies in the GarberWellington Formation, Central Oklahoma aquifer (Central 

Oklahoma aquifer), Cleveland County, Oklahoma: Master’s 

thesis, Oklahoma State University, 232 p.

Hantush, M.S., 1960, Modification of the theory of leaky 

aquifers: Journal of Geophysical Research., v. 65, no. 11, 

p. 3713–3725.

Hantush, M.S., 1961a, Drawdown around a partially penetrating well: Journal of the Hydraulics Division, Proceedings of 

the American Society of Civil Engineering, v. 87, no. HY4, 

p. 83–98.

Hantush, M.S., 1961b, Aquifer tests on partially penetrating 

wells: Journal of the Hydraulics Division, Proceedings of 

the American Society of Civil Engineers, v. 87, no. HY5, 

p. 171–194.

Hantush, M.S., and Jacob, C.E., 1955, Non-steady radial flow 

in an infinite leaky aquifer: American Geophysical Union 

Transactions, v. 36, p. 95–100.

Harbaugh, A.W., 2005, MODFLOW-2005, The U.S. Geological Survey modular ground-water model—The GroundWater Flow Process: U.S. Geological Survey Techniques 

and Methods, book 6, chap. A16, variously paged.

Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, 

M.G., 2000, MODFLOW-2000, the U.S. Geological Survey 

modular ground-water model—User guide to modularization concepts and the Ground-Water Flow Process: 

U.S. Geological Survey Open-File Report 00–92, 121 p.

Hargreaves, G.H., and Samani, Z.A., 1985, Reference crop 

evapotranspiration from temperature: Applied Engineering 

in Agriculture, v. 1, no. 2, p. 98–99.

Hart, D.L., Jr., 1966, Base of fresh ground water in southern Oklahoma: U.S. Geological Survey Hydrologic Atlas 

HA-223, 2 sheets, scale 1:250,000.

Heran, W.D., Green, G.N., and Stoeser, D.B., 2003, A digital 

geologic map database for the state of Oklahoma: U.S. Geological Survey Open-File Report 2003–247, 12 maps.

Hill, M.C., Banta, E.R., Harbaugh, A.W., and Anderman, 

E.R., 2000, MODFLOW-2000, the U.S. Geological Survey 

modular ground-water model—User guide to the observation, sensitivity, and parameter-estimation processes and 

three post-processing programs: U.S. Geological Survey 

Open-File Report 00–184, 210 p.

Hydrosolve, Inc., 2011, Aqtesolv for Windows: Hydrosolve, 

Inc., accessed January 30, 2011, at http://www.aqtesolv.com.

Horizon Systems Corporation, 2010, National Hydrography 

Dataset Plus (NHDPlus): Horizon Systems Corporation, 

accessed November 1, 2010, at http://www.horizon-systems.

com/nhdplus/.

Jacobsen, C.L., and Reed, E.W., 1949, Ground-Water supplies 

in the Oklahoma City area, Oklahoma: Oklahoma Geological Survey Mineral Report no. 20, 27 p.

Kenney, K.M., 2005, Outcrop-based lithofacies and depositional setting of arsenic-bearing Permian red beds in the 

Central Oklahoma aquifer, Cleveland County, Oklahoma– 

Master’s thesis, Oklahoma State University, 299 p.
Selected References 85

Kenny, J.F., Barber, N.L., Hutson, S.S., Linsey, K.S., 

Lovelace, J.K., and Maupin, M.A., 2009, Estimated use of 

water in the United States in 2005: U.S. Geological Survey 

Circular 1344, 52 p.

Keys, W.S., 1990, Borehole geophysics applied to groundwater investigations: U.S. Geological Survey Techniques of 

Water-Resource Investigation 02-E2, 150 p.

Konikow, L.F., Hornberger, G.Z., Halford, K.J., and Hanson, 

R.T., 2009, Revised multi-node well (MNW2) package for 

MODFLOW ground-water flow model: U.S. Geological 

Survey Techniques and Methods, book 6, chap. A30, 67 p.

Lindberg, F.A., ed., 1987, Correlation of stratigraphic units 

of North America (COSUNA) project, Texas-Oklahoma 

tectonic region: American Association of Petroleum Geologists, 1 sheet.

Lohman, S.W., 1972, Definitions of selected ground-water 

terms—Revisions and conceptual refinements: U.S. Geological Survey Water-Supply Paper 1988, 21 p.

Mashburn, S.L., and Magers, Jessica, 2011, Potentiometric 

surface in the Central Oklahoma (Garber-Wellington) 

aquifer, Oklahoma, 2009: U.S. Geological Survey Scientific 

Investigations Map 3147, 1 sheet, scale 1:24,000. 

Mogg, J.L., Schoff, S.L., and Reed, E.W., 1960, Groundwater 

Resources of Canadian County, Oklahoma: Oklahoma Geological Survey Bulletin 87, 112 p.

Multi-Resolution Land Characteristics Consortium (MRLC), 

2001, National Land Cover Database: U.S. Geological 

Survey, accessed August 22, 2011, at http://www.mrlc.gov/

nlcd01_data.php.

National Climatic Data Center, 2010, Locate Weather Observation Station Record: accessed July 14, 2010, at http://

www.ncdc.noaa.gov/oa/climate/stationlocator.html.

National Weather Service, 2011, What is the Coop Program?, 

accessed August 30, 2011, at http://www.weather.gov/om/

coop/what-is-coop.html.

Natural Resources Conservation Service, 2006, Digital general 

soil map of U.S., accessed October 13, 2009, at http://

datagateway.nrcs.usda.gov/.

Neuralog, Inc., 2010, Automated Well Log Digitizing Software: accessed January 30, 2010, at http://www.neuralog.

com/pages/NeuraLog.html.

Niswonger, R.G., and Prudic, D.E., 2005, Documentation 

of the Streamflow-Routing (SFR2) Package to include 

unsaturated flow beneath streams—A modification to SFR1: 

U.S. Geological Survey Techniques and Methods book 6, 

chap. A16, 50 p.

Nkoghe-Nze, S.C., 2002, A reconnaissance study of controls 

on aquifer quality in the Central Oklahoma Aquifer: Master’s thesis, Oklahoma State University, 68 p.

Oklahoma Climatological Survey, 2011a, The climate of 

Oklahoma County: accessed October 2011, at http://climate.

ok.gov/county_climate/Products/County_Climatologies/

county_climate_oklahoma.pdf.

Oklahoma Climatological Survey, 2011b, Daily time series 

using cooperative observer (COOP) data: accessed June 8, 

2011, at http://climate.ok.gov/index.php/climate/category/

my_county_or_town.

Oklahoma Climatological Survey, 2011c, Daily data retrieval, 

accessed October 2011, at http://www.mesonet.org/index.

php/weather/daily_data_retrieval.

Oklahoma Department of Commerce, 2012, County and MSA 

population projections 2000–2030: accessed April 16, 

2012, at http://www.okcommerce.gov/Data-And-Research/

Downloads/Population-Projections.

Oklahoma Statutes Title 82 Section 1020.5, 2011, Determination of Maximum Annual Yield.

Oklahoma Water Resources Board, 2010, Taking and use 

of groundwater, Title 785, Chapter 30: accessed December 12, 2011, at http://www.owrb.ok.gov/util/rules/pdf_rul/

RulesCurrent2010/Ch30.pdf.

Oklahoma Water Resources Board, 2011, 2012 Oklahoma 

Comprehensive Water Plan August 2011 Draft Report on 

the Central Watershed Planning Region: 149 p.

Oklahoma Water Resources Board, 2013, Water Well Record 

Search, accessed January 1, 2013, at http://www.owrb.

ok.gov/wd/search/search.php?type=wl.

Parkhurst, D.L., Christenson, S.C., and Breit, G.N., 1996, 

Ground-water-quality assessment of the Central Oklahoma 

Aquifer, Oklahoma; Geochemical and geohydrologic 

investigations: U.S. Geological Survey Water-Supply Paper 

2357–C, 101 p.

Parkhurst, D.L., Christenson, S.C., and Schlottmann, J.L., 

1989, Ground-water quality assessment of the Central 

Oklahoma Aquifer, Oklahoma; Analysis of available waterquality data through 1987: U.S. Geological Survey OpenFile Report 88–728, 80 p. 

Parkhurst, D.L., Christenson, S.C., and Schlottmann, J.L., 

1994, Ground-water quality assessment of the Central 

Oklahoma Aquifer, Oklahoma; Analysis of available waterquality data through 1987: U.S. Geological Survey WaterSupply Paper 2357–B, 74 p. 

Rasmussen, T.C., and Crawford, L.A., 1997, Identifying 

and removing barometric pressure effects in confined and 

unconfined aquifers: Ground Water, v. 35, no. 3, p. 502–511.
86 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Reilly, T.E., 2001, System and boundary conceptualization 

in ground-water flow simulation: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, 

chap. B8, 26 p.

Risser, D.W., Gburek, W.J., and Folmar, G.J., 2005, Comparison of methods for estimating ground-water recharge and 

base flow at a small watershed underlain by fractured bedrock in the eastern United States: U.S. Geological Survey 

Scientific Investigations Report 2005–5038, 31 p. 

Rorabaugh, M.I., 1964, Estimating changes in bank storage 

and groundwater contribution to streamflow: International Association of Scientific Hydrology, publication 63, 

p. 432–441.

Runkle, D.L., Christenson, S.C., and Rea, Alan, 1997, Digital 

data sets that describe aquifer characteristics of the Central 

Oklahoma Aquifer in central Oklahoma: U.S. Geological 

Survey Open-File Report 96–454, 2 disks.

Rutledge, A.T., 1998, Computer programs for describing the 

recession of ground-water discharge and for estimating 

mean ground-water recharge and discharge from streamflow 

records—Update: U.S. Geological Survey Water-Resources 

Investigations Report 98–4148, 43 p.

Schlottmann, J.L., and Funkhouser, R.A., 1991, Chemical 

analysis of water samples and geophysical logs from cored 

test holes drilled in the Central Oklahoma aquifer, Oklahoma: U.S. Geological Survey Open-File Report 91–464, 

58 p.

Schlottmann, J.L., Mosier, E.L., and Breit, G.N., 1998, 

Arsenic, chromium, selenium, and uranium in the Central 

Oklahoma Aquifer, in Christenson, Scott, and Havens, J.S., 

eds., Ground-water quality assessment of the Central Oklahoma Aquifer, Oklahoma—Results of investigations: U.S. 

Geological Survey Water-Supply Paper 2357–A, p.119–179.

Siemers, W.A., Stanley, T.M., and Suneson, N.H., 2000, Geology of Arcadia Lake parks-an introduction and field-trip 

guide: Oklahoma Geological Survey, Information Series 7, 

p. 3–9.

Smith, S.J., Paxton, S.T., Christenson, S.C., Puls, R.W., and 

Greer, J.R., 2009, Flow contribution and water quality with 

depth in a test hole and public-supply wells: Implications 

for arsenic remediation through well modification, Norman, 

Oklahoma, 2003–2006: Environmental Protection Agency 

600/R-09/036, 57 p.

Spane, F.A., 2002, Considering barometric pressure in groundwater flow investigations: Water Resources Research, v. 36, 

no. 6, p. 1078–1095.

Stanton, J.S., Ryter, D.W., and Peterson, S.M., 2012, Effects of 

linking a soil-water-balance model with a groundwater-flow 

model: Ground Water, v. 51, no. 4, p. 613–622.

Steel, E.W., 1947, Water supply and sewerage: New York, 

McGraw-Hill, 666 p.

Stoner, J.D., 1984, Estimate of self-supplied domestic water 

use in Oklahoma during 1980: U.S. Geological Survey 

Water-Resources Investigations Report 83–4223, 20 p.

Szilagyi, Jozef, Harvey, F.E., and Ayers, J.F., 2003, Regional 

estimation of base recharge to ground water using water 

balance and a base-flow index: Ground Water, v. 41, no. 4, 

p. 504–513.

Tanaka, H.H., and Davis, L.V., 1963, Ground water Rush 

Springs sandstone in the Caddo County Area, Oklahoma: 

Oklahoma Geological Survey Circular 61, 63 p.

Theis, C.V., 1935. The relation between the lowering of the 

piezometric surface and the rate and duration of discharge 

of a well using groundwater storage: American Geophysical 

Union Transactions, v. 16, p. 519–524.

Tortorelli, R.L., 2009, Water use in Oklahoma 1950–2005: 

U.S. Geological Survey Scientific Investigations Report 

2009–5212, 49 p.

Tucker, M.E., 1981, Sedimentary petrology an introduction: 

Blackwell Scientific Publications, Geoscience Texts, v. 3, 

252 p.

University of Oklahoma Center for Spatial Analysis, 2013, 

accessed September 19, 2013, at http://geo.ou.edu/

DataFrame.htm. 

U.S. Board on Geographic Names, 2013, Domestic and Antarctic Names – State and Topical Gazetteer Download Files: 

accessed August 1, 2013, at http://geonames.usgs.gov/.

U.S. Census Bureau, 2013, Census of Population and Housing: U.S. Census Bureau, accessed September 19, 2013, at 

http://www.census.gov/prod/www/decennial.html.

U.S. Census Bureau, 1990, 1990 Summary tape file 3 technical documentation, accessed September 19, 2013, at http://

www.census.gov/prod/www/decennial.html.

U.S. Census Bureau, 2001, Redistricting Census TIGER/Line 

Files, accessed September 19, 2013, at http://www.census.

gov/geo/maps-data/data/tiger.html.

U.S. Department of Agriculture, 2004, Hydrology—USDANRCS National Engineering Handbook, Part 630, Chapter 9: Washington D.C., 14 p.

U.S. Geological Survey, 2010a, Water-resources data for the 

United States, water year 2009: U.S. Geological Survey 

Water-Data Report WDR-USGS-2009, accessed November 21, 2011, at http://wdr.water.usgs.gov/wy2009/search.

jsp.
Selected References 87

U.S. Geological Survey, 2010b, National Water Information 

System data available on the World Wide Web (Water Data 

for the Nation), accessed November 21, 2009, at http://

waterdata.usgs.gov/nwis/.

Westenbroek, S.M., Kelson, V.A., Dripps, W.R., Hunt R.J., 

and Bradbury, K.R., 2010, SWB—A modified Thornth-

waite-Mather Soil-Water-Balance code for estimating 

groundwater recharge: U.S. Geological Survey Techniques 

and Methods, book 6, chap. A31, 60 p.

Wickersham, G., 1979, Ground water resources of the south-

ern part of the Garber-Wellington ground water basin, in 

Cleveland and Southern Oklahoma Counties and parts 

of Pottawatomie County, Oklahoma: Oklahoma Water 

Resources Board, Hydrologic Investigations Publication 86, 

3 sheets, scale 1:380,160.

Wilcoxon, F., 1945, Individual comparisons by ranking meth-

ods: Biometrics Bulletin, v. 1, no. 6, p. 80–83.

Wood, P.R., and Burton, L.C., 1968, Ground-water resources 

in Cleveland and Oklahoma Counties, Oklahoma: Okla-

homa Geological Survey Circular 71, 75 p.

Ziegler, A.M., 1990, Phytogeographic patterns and continental 

configurations during the Permian Period, in McKerrow, 

W.S., and Scotese, C.R., eds., Paleozoic paleogeography 

and biogeography: The Geological Society of London 

Memoir no. 12, p. 363–379.

Appendix
90 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

Appendix 1. Aquifer Test

A multiple-well aquifer test was completed at a production well near Norman, Okla., as part of this report to 

determine transmissivity and a storage coefficient for the 

Central Oklahoma aquifer (fig. 1–1). The production well was 

completed to a depth of 530 feet below land surface and sealed 

to a depth of 265 feet. The production well was screened from 

300 to 320 feet below land surface, 400 to 420 feet, 430 to 

450 feet, 460 to 480 feet, and 500 to 510 feet with a screen 

diameter of 10.75 inches. There were three observation wells 

located near the production well that were completed at various depths. The deep observation well, located 45.5 feet from 

the production well, was completed to a depth of 460 feet 

below land surface and sealed to a depth of 415 feet. The 

deep observation well was screened from 430 to 460 feet 

below land surface with a diameter of 6 inches. The middle 

observation well was completed to a depth of 235 feet below 

land surface, screened from 205 to 225 feet with a diameter 

of 6 inches and sealed to 190 feet. The shallow observation 

well was completed to a depth of 170 feet below land surface, 

screened from 140 to 160 feet with a diameter of 6 inches 

and sealed to 125 feet. The production and observation wells 

are completed in the Garber Sandstone-Wellington Formation (undifferentiated) just to the east of the outcrop extent of 

the Hennessey Group (see geologic units on figs. 4 and 5 in 

the Geology of the Central Oklahoma Aquifer section of this 

report). The production-well pump was started at 10:30 AM 

on March 1, 2011. The pump ran at a rate of 190 gallons 

per minute for 7 days and shut off at 3:15 PM on March 8, 

2011. Water levels to document recovery in the observation 

wells were measured from March 8 through March 16, 2011. 

Water-levels measured in the shallow and middle observation 

wells indicated that the pumping was not causing measurable 

drawdown in the water levels in those wells. Therefore, only 

the data from the deep observation well were analyzed for the 

aquifer test (fig. 1–2).

The aquifer test was analyzed by using the AQTESOLV 

software package (Hydrosolve, Inc., 2011). The depths of the 

production and observation wells with casing information 

were input to the AQTESOLV program to correct for partial 

penetration of the aquifer. Several model solutions were tried 

for the pumping period of the test, but the best fit was the 

Hantush for leaky confined aquifers solution (Hantush, 1960; 

Hantush, 1961a; and Hantush, 1961b) (fig. 1–3). Water levels 

from the recovery period of the test were matched and the best 

fit was the Hantush-Jacob for leaky confined aquifers solution 

(Agarwal, 1980; Hantush and Jacob, 1955) (fig. 1–4). 

Transmissivity from the analytical solution was 

220 square feet per day (fig. 1–3). Using the screened interval of 90 feet in the production well, the geohydrologic-unit 

hydraulic conductivity is 2.4 feet per day. The average percent 

sand of the Central Oklahoma aquifer at the location and of 

this aquifer test is approximately 70 percent. The storage 

coefficient from the analytical solution was 0.0013 (fig. 1–3), 

which is an order of magnitude higher than previously published storage coefficients for this aquifer.

Mid-depth well

235 feet deep

Deep well

460 feet deep

Shallow well

170 feet deep

Production well

530 feet deep

Well house

Gate

45.5 feet

Figure 1–1. Layout of the aquifer test in the Central Oklahoma 

aquifer. (Not to scale).
Appendix 1. Aquifer Test 91

200

220

240

260

280

300

320

0 5,000 10,000 15,000 20,000 25,000

Depth to water, in feet

Time since pumping began, in minutes

EXPLANATION

U.S. Geological Survey station 351543097211801 water level

Figure 1–2. The deep 

observation well water-level 

during the pumping (March 

1–8) and recovery periods 

(March 8–16) of the Norman 

aquifer test in the Central 

Oklahoma aquifer, 2011.

1 10 100 1,000 10,000 100,000

0.01

0.1

1

10

100

Time, in minutes

Displacement, in feet

Model best fit of head

Model best fit of derivative

Change in head in the deep observation well 

(U.S. Geological Survey station 351543097211801)

Derivative of change in head in deep observation well

Parameters:

Transmissivity: 224 feet squared per day

Storage coefficient: 0.001363

Hantush solution

Leaky aquifer model

EXPLANATION

Figure 1–3. Pumping 

drawdown data curves and 

derivatives with best-fit 

Hantush method with aquitard 

storage solution for leaky 

confined aquifer analysis

(Hantush, 1960).
92 Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma

0.1 1 10 100 1,000

0.001

0.01

0.1

1

10

100

Agarwal equivalent time, in minutes

Recovery, in feet

Model best fit of head

Model best fit of derivative

Change in head in the deep observation well 

(U.S. Geological Survey station 351543097211801)

Derivative of change in head in deep observation well

Parameters:

Transmissivity: 271.2 feet squared per day

Storage coefficient: 0.001987

Hantush solution

Leaky aquifer model

EXPLANATION

Figure 1–4. Water-level recovery data in Agarwal equivalent time with best-fit curve for the 

recovery analysis (Agarwal, 1980; Hantush and Jacob, 1955).
Publishing support provided by: 

Rolla and Lafayette Publishing Service Centers

For more information concerning this publication, contact: 

Director, Oklahoma Water Science Center 

U.S. Geological Survey 

202 NW 66th St., Bldg. 7 

Oklahoma City, Oklahoma 73116 

(405) 810-4400

Or visit the Oklahoma Water Science Center Web site at: 

http://ok.water.usgs.gov/
ISSN 2328-031X (print)

ISSN 2328-0328 (online)

http://dx.doi.org/0.3133/sir20135219

Mashburn and others—Hydrogeology and Simulation of Groundwater Flow in the Central Oklahoma (Garber-Wellington) Aquifer, Oklahoma—SIR 2013–5219