U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2019–5014

Prepared in cooperation with the Elbert County Board of County Commissioners

Groundwater-Level Elevations in the Denver Basin Bedrock 

Aquifers of Elbert County, Colorado, 2015–18
Cover. Cover is a montage of photographs taken in Elbert County, Colorado, between August and 

December 2018. Photographs by C.A. Penn, U.S. Geological Survey.
Groundwater-Level Elevations in the 

Denver Basin Bedrock Aquifers of 

Elbert County, Colorado, 2015–18

By Colin A. Penn and Rhett R. Everett

Prepared in cooperation with the Elbert County Board of County Commissioners

Scientific Investigations Report 2019–5014

U.S. Department of the Interior

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

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2019

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as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Penn, C.A., and Everett, R.R., 2019, Groundwater-level elevations in the Denver Basin bedrock aquifers of Elbert 

County, Colorado, 2015–18: U.S. Geological Survey Scientific Investigations Report 2019–5014, 50 p., 

https://doi.org/10.3133/sir20195014.

ISSN 2328-0328 (online)
iii

Contents

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

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................3

Previous Studies ...................................................................................................................................3

Description of Study Area ...................................................................................................................3

Description of the Denver Basin Aquifer System............................................................................5

Study Methods ...............................................................................................................................................5

Identifying Target Areas and Well Selection ...................................................................................5

Geodetic Survey of Wells ....................................................................................................................6

Groundwater-Level Measurements and Groundwater-Level Elevations....................................9

Discrete Groundwater-Level Measurements and Groundwater-Level Elevations ..........9

Continuous Groundwater-Level Measurements and Groundwater-Level 

Elevations ......................................................................................................................12

Accessing Data..........................................................................................................................12

Groundwater-Level Summary, Groundwater-Level Elevation Trend Analysis, and 

Mapping..................................................................................................................................12

Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County ................14

Discrete Groundwater-Level Elevation Summary and Trends ....................................................14

Continuous Groundwater-Level Elevation Summary and Trends ...............................................14

Potentiometric-Surface and Difference Maps ..............................................................................21

Future Work ..................................................................................................................................................21

Summary........................................................................................................................................................21

References Cited..........................................................................................................................................24

Appendix 1. Groundwater-Well Measurement Diagram ...................................................................27

Appendix 2. Hydrographs Showing Groundwater-Level Elevation Through Time for Wells 

in the Elbert County Groundwater-Level Monitoring Network. ..............................................28

Appendix 3. Discrete Groundwater-Level Elevation Trends .............................................................49

Acknowledgments

The authors would like to thank the residents of Elbert County, especially the well owners 

who allowed access to their property. The authors also acknowledge the participation of the 

Elbert County Board of County Commissioners and Water Advisory Council. The U.S. Geological 

Survey and Elbert County Board of County Commissioners acknowledge the Colorado Water 

Conservation Board for partially funding the study. The authors also acknowledge U.S Geological 

Survey colleagues Evan Gohring and Jordan Skipwith for assistance with collecting and 

processing data related to this study.
iv

Figures

1. Location of the Denver Basin aquifer system and geologic lines of section A, A–A'

and B, B–B’ near Elbert County, Colorado................................................................................2

2. Location of groundwater-level monitoring network wells with aquifer of

completion, Elbert County, Colorado. Well name abbreviations are as follows:

UDAW, upper Dawson aquifer; LDAW, lower Dawson aquifer; DENV, Denver

aquifer; ARAP, Arapahoe aquifer; LARA, Laramie-Fox Hills aquifer ....................................4

3. Generalized geologic cross sections A, A–A’, west to east, and B, B–B', south to

north, through the Denver Basin aquifer system. See figure 1 for cross section

locations and table 1 for bedrock aquifer descriptions within each geologic unit...........6

4. Location of wells completed in Denver Basin bedrock aquifers, predicted

100-foot drawdown, well density, and areas of interest in the Arapahoe aquifer, for

groundwater-level monitoring in Elbert County, Colorado.....................................................8

5. Distribution of significant trends in discrete groundwater-level elevations, by

aquifer, Elbert County, Colorado...............................................................................................18

6. Distribution of significant trends in discrete groundwater-level elevations in the

upper Dawson and lower Dawson aquifers near the towns of Elizabeth and Kiowa,

Elbert County, Colorado .............................................................................................................19

7. Estimated potentiometric surface of the upper Dawson aquifer in April 2018 and

change in hydraulic head between April 2015 and April 2018, western Elbert

County, Colorado.........................................................................................................................22

8. Estimated potentiometric surface of the lower Dawson aquifer in April 2018 and

change in hydraulic head between April 2015 and April 2018, western Elbert

County, Colorado.........................................................................................................................23

1.1. Diagram showing example measurement point and groundwater-level

measurement using A, a calibrated steel tape with chalk, and B, a calibrated

electrical tape .............................................................................................................................27

2.1. Groundwater-level hydrograph for DENV 17, USGS site number 

390755104172501, Elbert County, Colorado .............................................................................28

2.2. Groundwater-level hydrograph for ARAP 8, USGS site number 

390800104172601, Elbert County, Colorado .............................................................................28

2.3. Groundwater-level hydrograph for LARA 7, USGS site number 

390817104040301, Elbert County, Colorado .............................................................................29

2.4. Groundwater-level hydrograph for DAWMAS26, USGS site number

390935104301001, Elbert County, Colorado .............................................................................29

2.5. Groundwater-level hydrograph for UDAW 19, USGS site number 

391126104354701, Elbert County, Colorado .............................................................................30

2.6. Groundwater-level hydrograph for DAWMAS27, USGS site number

391148104294101, Elbert County, Colorado .............................................................................30

2.7. Groundwater-level hydrograph for ARAP 7, USGS site number 

391208104053301, Elbert County, Colorado .............................................................................31

2.8. Groundwater-level hydrograph for DENV 16, USGS site number 

391257104173601, Elbert County, Colorado .............................................................................31

2.9. Groundwater-level hydrograph for LDAW 16, USGS site number 

391502104273601, Elbert County, Colorado .............................................................................32

2.10. Groundwater-level hydrograph for DAWMAS22, USGS site number

391545104335401, Elbert County, Colorado .............................................................................32

2.11. Groundwater-level hydrograph for LARA 6, USGS site number 

391609104014001, Elbert County, Colorado .............................................................................33
v

2.12. Groundwater-level hydrograph for LARA 5, USGS site number 

391621104012001, Elbert County, Colorado .............................................................................33

2.13. Groundwater-level hydrograph for ARAPMAS27, USGS site number

391740104072401, Elbert County, Colorado .............................................................................34

2.14. Groundwater-level hydrograph for DENV 15, USGS site number

391811104140301, Elbert County, Colorado .............................................................................34

2.15. Groundwater-level hydrograph for DENV 14, USGS site number

391821104270601, Elbert County, Colorado .............................................................................35

2.16. Groundwater-level hydrograph for LDAW 15, USGS site number

391829104385301, Elbert County, Colorado .............................................................................35

2.17. Groundwater-level hydrograph for ARAPMAS22, USGS site number

391834104205601, Elbert County, Colorado .............................................................................36

2.18. Groundwater-level hydrograph for DAWMAS28, USGS site number

391848104261401, Elbert County, Colorado .............................................................................36

2.19. Groundwater-level hydrograph for DENMAS05, USGS site number

391851104204501, Elbert County, Colorado .............................................................................37

2.20. Groundwater-level hydrograph for DAWMAS16, USGS site number

391852104391301, Elbert County, Colorado .............................................................................37

2.21. Groundwater-level hydrograph for UDAW 18, USGS site number

391915104375001, Elbert County, Colorado .............................................................................38

2.22. Groundwater-level hydrograph for UDAW 14, USGS site number

391924104374101, Elbert County, Colorado .............................................................................38

2.23. Groundwater-level hydrograph for ARAP 6, USGS site number 

391946104114501, Elbert County, Colorado .............................................................................39

2.24. Groundwater-level hydrograph for LDAW 12, USGS site number

392058104364401, Elbert County, Colorado .............................................................................39

2.25. Groundwater-level hydrograph for LDAW 14, USGS site number

392125104323701, Elbert County, Colorado .............................................................................40

2.26. Groundwater-level hydrograph for UDAW 17, USGS site number

392130104341401, Elbert County, Colorado .............................................................................40

2.27. Groundwater-level hydrograph for DAWMAS21, USGS site number

392131104351701, Elbert County, Colorado .............................................................................41

2.28. Groundwater-level hydrograph for UDAW 12, USGS site number

392133104310201, Elbert County, Colorado .............................................................................41

2.29. Groundwater-level hydrograph for UDAW 16, USGS site number

392203104342301, Elbert County, Colorado .............................................................................42

2.30. Groundwater-level hydrograph for UDAW 15, USGS site number

392355104382001, Elbert County, Colorado .............................................................................42

2.31. Groundwater-level hydrograph for ARAPMAS28, USGS site number

392400104150601, Elbert County, Colorado .............................................................................43

2.32. Groundwater-level hydrograph for ARAP 5, USGS site number 

392434104142701, Elbert County, Colorado .............................................................................43

2.33. Groundwater-level hydrograph for LARA 3, USGS site number 

392616103591001, Elbert County, Colorado .............................................................................44

2.34. Groundwater-level hydrograph for LARA 4, USGS site number 

392635103590001, Elbert County, Colorado .............................................................................44

2.35. Groundwater-level hydrograph for LDAW 13, USGS site number

392724104341901, Elbert County, Colorado .............................................................................45
vi

2.36. Groundwater-level hydrograph for UDAW 13, USGS site number

392856104393801, Elbert County, Colorado .............................................................................45

2.37. Groundwater-level hydrograph for DENV 13, USGS site number

393012104310701, Elbert County, Colorado .............................................................................46

2.38. Groundwater-level hydrograph for UDAW 11, USGS site number

393016104392601, Elbert County, Colorado .............................................................................46

2.39. Groundwater-level hydrograph for ARAP 4, USGS site number 

393225104073601, Elbert County, Colorado .............................................................................47

2.40. Groundwater-level hydrograph for DAWMAS19, USGS site number

393227104343401, Elbert County, Colorado .............................................................................47

2.41. Groundwater-level hydrograph for ARAP 3, USGS site number 

393251104073701, Elbert County, Colorado .............................................................................48

2.42. Groundwater-level hydrograph for DENV 12, USGS site number

393350104151701, Elbert County, Colorado .............................................................................48

Tables

1. Physical characteristics of bedrock aquifers in the Denver Basin aquifer system..........7

2. Well identification and location information, and a summary of discrete

groundwater-level measurements from April 2015 to June 2018 in

Elbert County, Colorado .............................................................................................................10

3. Summary of discrete groundwater-level elevations, April 2015 to June 2018,

Elbert County, Colorado. ............................................................................................................15

4. Statistically significant trends in discrete static groundwater-level elevations,

April 2015 to June 2018, Elbert County, Colorado ..................................................................17

5. Statistical summary of continuous daily maximum groundwater-level elevations,

January 2016 to June 2018, Elbert County, Colorado............................................................20

6. Trends in continuous and discrete daily maximum groundwater-level elevations,

2015 to June 2018, Elbert County Colorado.............................................................................20

3.1. Trends in discrete static groundwater-level elevations, April 2015 to June 2018, 

Elbert County, Colorado .............................................................................................................49
vii

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

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

Flow rate

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

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

°F = (1.8 × °C) + 32.

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

°C = (°F – 32) / 1.8.

Datum

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

(NAVD 88).

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

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

Abbreviations

ARAP Arapahoe aquifer

CDWR Colorado Division of Water Resources

CWCB Colorado Water Conservation Board

DENV Denver aquifer

ECBOCC Elbert County Board of County Commissioners

GNSS Global Navigation Satellite System

LARA Laramie-Fox Hills aquifer

LDAW Lower Dawson aquifer

LSD land-surface datum

MP measuring point

NAD 83 North American Datum of 1983

NAVD 88 North American Vertical Datum of 1988

NWIS National Water Information System

OPR Observation-Prediction

OPUS Online Positioning User System

PPR Parameter-Prediction

RTK Real-time Kinematic

UDAW Upper Dawson aquifer

UTM Universal Transverse Mercator

WGS 84 World Geodetic System of 1984

USGS U.S. Geological Survey
Groundwater-Level Elevations in the Denver Basin 

Bedrock Aquifers of Elbert County, Colorado, 2015–18

By Colin A. Penn and Rhett R. Everett

Introduction

Elbert County is a mostly rural county in eastern Colorado 

and part of the western extent of the U.S. Great Plains. Public 

and domestic water users in Elbert County rely on groundwater 

withdrawals from bedrock aquifers in the Denver Basin aquifer 

system (herein referred to as Denver Basin bedrock aquifers) to meet their water-supply demands. In 2010, estimated 

withdrawals were 0.67 million gallons per day (Mgal/d) for 

public supply and 1.76 Mgal/d for domestic supply, which are 

13 percent and 33 percent, respectively, of total Elbert County 

groundwater withdrawals (5.27 Mgal/d; Maupin and others, 2014). Withdrawals for irrigation (45 percent), livestock 

(8 percent), and mining (1 percent) are the remaining Elbert 

County groundwater use. Population and corresponding water 

use has increased substantially in the county over the past 2 

decades (1999–2018) and is expected to continue to rise in 

the future (Forsgren Associates Inc., 2018). The population 

of Elbert County from 1990 to 2000 increased from 9,646 to 

19,872 (+106 percent), from 2000 to 2010 increased to 23,086 

(+16 percent), and from 2010 to 2017 increased to 25,642 

(+11 percent) (U.S. Census Bureau, 1996, 2000, 2017). Any 

continued increase in population, agriculture, or industry likely 

would lead to an increase in water demand that requires a 

proportional increase in water supply. Zoning regulations in the 

county stipulate that any new subdivision development must 

show 300 years of adequate water supply, including groundwater, as part of the permitting process (Elbert County, 2009).

Elbert County is surrounded by counties that also rely 

heavily on groundwater withdrawals from Denver Basin 

bedrock aquifers (fig. 1). To the west, Douglas County had an 

estimated 26.82 Mgal/d of groundwater withdrawals in 2010 

(Maupin and others, 2014). Urban and suburban development in Douglas County has continued to increase, especially 

in areas that border Elbert County (Douglas County, 2018), 

putting further demand on groundwater resources in the area 

(Moore and others, 2007). The surrounding Arapahoe and 

El Paso Counties also rely on groundwater and withdrew 

an estimated 34.36 Mgal/d and 23.86 Mgal/d, respectively, 

in 2010 (Maupin and others, 2014). Long-term groundwater monitoring in the Denver Basin bedrock aquifers by the 

Colorado Division of Water Resources (CDWR) indicates negative changes in groundwater-level elevations in all bedrock 

Abstract

Public and domestic water supplies in Elbert County, 

Colorado, rely on groundwater withdrawals from five bedrock 

aquifers in the Denver Basin aquifer system (lower Dawson, 

upper Dawson, Denver, Arapahoe, and Laramie-Fox Hills) 

to meet water demands. Increased pumping in response 

to regional population growth and development has led to 

declining groundwater levels in neighboring Douglas County. 

The U.S. Geological Survey, in cooperation with the Elbert 

County Board of County Commissioners, began a study in 

2015 to monitor groundwater levels within Elbert County. 

The purpose of this study is to report on groundwater levels 

measured between April 2015 and June 2018, and analyze 

trends and changes in groundwater-level elevations throughout 

the county.

Discrete groundwater levels were measured at 42 wells 

within Elbert County. Six of those wells contained equipment 

to make and record continuous groundwater-level measurements at hourly intervals. All five aquifers had wells with a 

rise in groundwater-level elevation and wells with a decline 

in groundwater-level elevation, based on a relative change 

in groundwater-level elevation between the April 2015 and 

April 2018 measurements. All aquifers except the upper 

Dawson had more wells with significant negative trends 

in discrete groundwater-level elevations than significant 

positive trends; however, at least one well within the upper 

Dawson, lower Dawson, Arapahoe, and Laramie-Fox Hills 

aquifers had a significant positive trend. Wells screened in 

the lower Dawson aquifer consistently had the most significant negative trends, with an average trend of −1.96 feet 

per year (ft/year). The upper Dawson, Denver, Arapahoe, 

and Laramie-Fox Hills aquifers had average trends of 

0.03 ft/year, −1.04 ft/year, −0.46 ft/year, and −0.65 ft/year, 

respectively. Trends in continuous groundwater-level elevations were in agreement with significant trends in discrete 

groundwater-level elevations. Potentiometric-surface maps 

of the upper and lower Dawson aquifers for April 2015 and 

April 2018 show that differences in hydraulic head from the 

two measurement periods were greatest along the western 

part of Elbert County. Results of this study could guide 

future groundwater monitoring in the county and aid in longterm planning of water resources. 
2 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 1. Location of the Denver Basin aquifer system and geologic lines of section A, A–A’ and B, B–B’ near Elbert 

County, Colorado.

B

A'

B'

A

A A'

ADAMS

ARAPAHOE 

ELBERT

LINCOLN

EL PASO

BOULDER

LARIMER

LOGAN

MORGAN

WASHINGTON

WELD

BROOMFIELD

CLEARCREEK GILPIN

JEFFERSON

DENVER

TELLER

FREMONT

PARK Colorado Front Range Mountains

Palmer Divide

Big Sandy

Creek

South Platte River

Kiowa Creek

West Bijou Creek East Bijou Creek

Middle Bijou Creek Bijou Creek

Boulder

DOUGLAS

Upper Dawson 

Lower Dawson 

Denver 

Arapahoe 

Laramie-Fox Hills 

EXPLANATION

Aquifer extent

Elbert County study

 area boundary

Line of section

Base from U.S. Geological Survey digital data, 2014

Universal Transverse Mercator, Zone 13

North American Datum of 1983

Denver Basin aquifer extent from Paschke, 2011

0 5 10 15 20 KILOMETERS

0 5 10 15 20 MILES

104°30' 104°00' 103°30'

40°00'

39°30'

39°00'

105°00'

DENVER

Greeley

Watkins

Castle Rock

Elbert

Elizabeth Kiowa

Parker

Agate

Limon

Colorado

Springs

COLORADO

ELBERT

COUNTY

Denver Basin

extent

Arkansas River
Introduction 3

aquifers over the past 10 years (2007–17); however, more 

recent measurements (5- and 1-year changes) are inconsistent 

(Flor, 2017). Of the 290 wells monitored by CDWR in Denver 

Basin bedrock aquifers, 27 wells are in Elbert County.

Recognizing a need to better understand the future of 

water resources in Elbert County, the Elbert County Board of 

County Commissioners (ECBOCC) commissioned a comprehensive 5-year study of water resources and future demand 

scenarios (Forsgren Associates Inc., 2018). They also made a 

commitment to monitoring groundwater levels in the Denver 

Basin bedrock aquifers. The U.S. Geological Survey (USGS), 

in cooperation with ECBOCC, began a study in 2015 to 

measure groundwater levels in Denver Basin bedrock aquifers 

throughout Elbert County. The goals of this study were to 

establish a countywide groundwater-level monitoring network, 

make routine measurements of groundwater levels, and assess 

changes in groundwater-level elevations over the study period. 

Continuation of the monitoring network will aid in the longterm planning of water resources. 

Purpose and Scope

The purpose of this report is to present an analysis of 

groundwater-level changes and trends in groundwater-level 

elevations in the Denver Basin bedrock aquifers in Elbert 

County, Colo., from April 2015 to June 2018. Forty-two wells 

are included in the monitoring network where discrete groundwater levels are measured bi-monthly (February, April, June, 

August, October, and December; fig. 2). At 6 of the 42 wells, a 

vented pressure transducer with an internal data logger records 

hourly groundwater-level measurements (also referred to as 

continuous groundwater levels). This report presents details of 

the well-selection process, a summary of groundwater levels 

measured during the study period, and a trend analysis of 

groundwater-level elevations in Elbert County.

Previous Studies

Groundwater levels in Elbert County historically have 

been measured by the Colorado Water Conservation Board 

(CWCB), CDWR, and USGS. McConaghy and others 

(1964) present measurements from 1956 to 1963 made by 

CWCB. Major and others (1983) report measurements from 

1956 through 1981 made by USGS, and Flor (2017) more 

recently published groundwater levels measured by CDWR 

with varying periods of record through 2017. In neighboring Douglas County, a similar groundwater-level monitoring 

network, maintained by the USGS, has been operating since 

2011 (Everett, 2014). Changes in groundwater levels, population growth, and water supply are topics of ongoing interest 

in Elbert County and the surrounding area (Moore and others, 

2007; Forsgren Associates Inc., 2018).

Many previous studies have examined the geologic 

structure and hydrologic conditions of the Denver Basin 

bedrock aquifers and surrounding areas. These studies, listed 

or summarized in Wireman and Romero (1989) and Paschke 

(2011), were crucial to the development of a groundwater 

flow model (Robson, 1987) and a fully three-dimensional 

MODFLOW-2000 groundwater flow model (Paschke, 2011) of 

the Denver Basin aquifer system. The Kiowa Core, drilled on 

the Elbert County Fairgrounds in Kiowa, Colo., in 1999, provides a near-continuous record of geophysical properties for all 

bedrock aquifers in the Denver Basin aquifer system (Raynolds 

and others 2001). The 2,256-foot (ft) core was analyzed for 

hydrologic properties, leading to a better understanding of 

specific yield (Woodard and others, 2002) and hydraulic 

conductivity (Barkmann, 2004) in the basin, which helped to 

inform the MODFLOW-2000 model (Paschke, 2011). 

Description of Study Area

Elbert County is a mostly rural, 1,850-square-mile 

(mi2) county in eastern Colorado with an eastern border 

approximately 90 miles from the eastern border of Colorado. 

The northwestern corner of Elbert County is approximately 

35 miles southeast of Denver, and the southwestern corner of 

the county is approximately 35 miles northeast of Colorado 

Springs (fig. 1). Neighboring counties are Arapahoe County 

to the north, Douglas County to the west, El Paso County 

to the southwest, and Lincoln County to the southeast and 

east. Natural vegetation is dominantly drought-resistant, high 

plains grasses that consist of Bouteloua gracilis (blue grama), 

Bouteloua dactyloides (buffalograss), Pascopyrum (wheatgrass), and Fescuta sp. (fescue). Ridgelines and rolling hills in 

the central and western parts of the county have large stands 

of Pinus ponderosa (ponderosa pine), and numerous riparian 

corridors support stands of Populus deltoides (cottonwood) 

and Salix, sp. (willow) (Elbert County Planning Commission, 

2018). No perennial streams flow through the county; however, many intermittent streams originate in the county, including Kiowa Creek; East, Middle, and West Bijou Creeks, which 

flow to the South Platte River; and Big Sandy Creek, which 

flows to the Arkansas River.

The population of Elbert County has been increasing 

since the 1990 census. Rapid growth occurred from 1990 

to 2000, and more steady growth has occurred since 2000. 

Western parts of the county are close to the urban corridor 

surrounding Denver and neighboring Douglas County urban 

centers, Castle Rock, and Parker. The 5-year water-supply 

study (Forsgren Associates Inc., 2018) focused on areas 

within the county expected to have the most development; 

these include the northwestern part of the county east of the 

city of Parker, called the Northwest Planning Area, and an 

area surrounding the towns of Elizabeth and Kiowa, called 

the Elizabeth–Kiowa Planning Area. The Elizabeth-Kiowa 

and Northwest Planning Areas are currently experiencing 

higher rates of growth and development than other parts of 

the county and include clustered development of subdivisions (Elbert County Planning Commission, 2018; Forsgren 

Associates Inc., 2018).
4 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 2. Location of groundwater-level monitoring network wells with aquifer of completion, Elbert County, Colorado. Well name 

abbreviations are as follows: UDAW, upper Dawson aquifer; LDAW, lower Dawson aquifer; DENV, Denver aquifer; ARAP, Arapahoe 

aquifer; LARA, Laramie-Fox Hills aquifer.

EL PASO

WASHINGTON 

LINCOLN

ELBERT

ARAPAHOE

DOUGLAS

DAWMAS21

DAWMAS26

DENV 16

DENV 17

ARAP 8

ARAP 7 DAWMAS27 UDAW 19

DAWMAS22

LDAW 16

ARAPMAS27 ARAPMAS22

DENV 15

LDAW 15

DAWMAS28

DENV 14

UDAW 12

LARA 6

UDAW 17 DENMAS05

DAWMAS16

ARAP 6

UDAW 14

UDAW 16

LDAW 14

ARAPMAS28

UDAW 15 ARAP 5

LARA 4

LARA 3

LDAW 13

UDAW 13

UDAW 11 DENV 13

ARAP 4 DAWMAS19

ARAP 3

DENV 12

LARA 5

LARA 7

UDAW 18

LDAW 12

Alluvial deposits 

Upper Dawson 

Lower Dawson 

Denver 

Arapahoe 

Laramie-Fox Hills 

Upper Dawson 

Lower Dawson 

Denver 

Arapahoe 

Laramie Fox Hills 

Well with pressure transducer

Well identification number

EXPLANATION

Aquifer extent

Elbert County study

 area boundary

Well indicating aquifer of completion

DENV 17

Base from U.S. Geological Survey digital data, 2014

Universal Transverse Mercator, Zone 13

North American Datum of 1983

Denver Basin aquifer extent from Paschke, 2011

0 4 8 12 16 KILOMETERS

0 4 8 12 16 MILES

39°30'

39°15'

39°00'

104°45' 104°30' 104°15' 104°00' 103°45'

Kutch

Matheson

Cedar Point

Bijou

Beck Sand

Draw Crossing

Simla

Elbert

Elizabeth

Fondis

Kiowa

Ponderosa Park

COLORADO

ELBERT

COUNTY
Study Methods 5

Description of the Denver Basin Aquifer System

 The Denver Basin aquifer system is bound on the western 

edge by the base of the Colorado Front Range and extends into 

the eastern plains of Colorado, covering an area of approximately 7,000 mi2

 (fig. 1). The northernmost extent ends near 

the city of Greeley in Weld County, whereas the southern extent 

passes under the topographic Palmer Divide and ends southeast of Colorado Springs in El Paso County. The Denver Basin 

aquifer system is composed of several bedrock aquifers, which 

underlie Quaternary alluvial aquifers (Paschke, 2011). The bedrock aquifers in the basin have a synclinal structure composed of 

Late Cretaceous to Tertiary-age sandstone bedrock separated by 

unnamed claystone confining units (Fenneman, 1931; Robson, 

1987; Paschke, 2011) and confined underneath by the Cretaceous 

Pierre Shale (fig. 3, table 1). The four bedrock aquifers, from 

oldest (deepest) to youngest (shallower), are the Laramie-Fox 

Hills aquifer in the Laramie Formation and Fox Hills Sandstone, 

Arapahoe aquifer in the Arapahoe Formation, Denver aquifer in 

the Denver Formation, and Dawson aquifer in the Dawson Formation. The Arapahoe and Dawson aquifers are divided by discontinuous confining units into upper and lower aquifers in parts 

of the basin. In Elbert County, the Dawson aquifer is divided 

into upper and lower aquifers. Parts of the basin are overlain by 

unconfined alluvial aquifers. Outcrops of each aquifer can be 

found along the outer edge of their extents and are generally considered unconfined, whereas confined conditions exist towards 

the interior of the basin in each aquifer where it is overlain by a 

younger confining unit (Paschke, 2011).

Many previous studies have examined the extent, 

thickness, age, and physical properties of each aquifer. The 

physical characteristics of the Denver Basin bedrock aquifers 

are summarized in table 1. Studies from which the information in table 1 was acquired include Romero (1976), Kirkham 

and Ladwig (1979), Schneider (1980), Robson and others 

(1981a), Robson and others (1981b), Robson (1987), Crifasi 

(1992), Raynolds and others (2001), Raynolds (2002, 2004), 

and Paschke (2011).

Study Methods

This section describes the methods used to identify 

target areas in Elbert County, which were used to select study 

wells, complete a Global Navigation Satellite System (GNSS) 

survey of well land-surface elevations, make and process 

groundwater-level measurements, access data, analyze trends 

in groundwater-level elevations throughout the county, and 

derive potentiometric-surface and difference maps from static 

groundwater-level measurements.

Identifying Target Areas and Well Selection

Areas within Elbert County were targeted for routine 

groundwater-level measurements using a combination of 

groundwater model statistics, groundwater model pumping scenarios, well density, and property access. The USGS 

MODFLOW-2000 groundwater model of the Denver Basin 

aquifer system from Paschke (2011) was used to determine 

areas within the county where groundwater-level observations could improve future model parameter calibration and 

decrease model uncertainty. A model analysis tool, OPR-PPR, 

combines Parameter-Prediction (PPR) statistics and Observation-Prediction (OPR) statistics to evaluate model uncertainty 

and its relation to observed data (Hill and Tiedeman, 2007; 

Tonkin and others, 2007). A statistic output from OPR-PRR, 

referred to by Tonkin and others (2007) as the OPA statistic, is defined as the percent change in parameter standard 

deviation caused by omitting or adding one or more observations. The OPA statistics for several pilot observation points 

in the Arapahoe aquifer in the Denver Basin model were 

combined into a single statistic called the Combined Observation-Parameter statistic (Paschke, 2011). Areas with a high 

statistic correspond to areas where the addition of observations could be used to decrease parameter uncertainty in the 

Arapahoe aquifer in future model calibration. The Combined 

Observation-Parameter statistic from Paschke (2011) identified areas in the north-central and northwestern parts of the 

county, indicated in figure 4 by dark grey shading, where 

additional observations could be beneficial if wells completed 

in the Arapahoe aquifer are accessible. 

Future water-use scenarios presented in Paschke 

(2011) also were used to identify areas (target areas) where 

drawdown from pumping may affect groundwater levels. 

Water-use scenarios from 2003 through 2053 were simulated 

with the Denver Basin aquifer system model, and estimated 

drawdown maps, by aquifer, for the basin were created. 

Areas with a predicted drawdown greater than or equal to 

100 ft were identified in the western half of the county, predominantly along the northwestern border (fig. 4). Although 

these predictions are not definitive, they can guide monitoring efforts by identifying areas where future problems could 

arise. Areas of predicted drawdown greater than or equal to 

100 ft in the upper and lower Dawson aquifers fall within the 

Northwest and Elizabeth-Kiowa Planning Areas identified by 

the ECBOCC as focus areas for water-supply study and planning (Forsgren Associates Inc., 2018). 

After target areas were identified, existing wells within 

the county were mapped by aquifer of completion using data 

from the CDWR well permit database (Colorado Department 

of Natural Resources, 2018). The density of wells was used to 

identify areas where monitoring could be conducted (fig. 4). 

Property owners with domestic supply wells in target areas 

were contacted through door-to-door solicitation. The primary 

focus was aimed at selecting wells in the upper Dawson, lower 

Dawson, and Denver aquifers, based on discussions with 

the ECBOCC. Several wells completed in the Arapahoe and 

Laramie-Fox Hills aquifers but outside target areas also were 

included to assess groundwater levels countywide. Forty-two 

domestic supply wells were initially selected for the network, 

including 11 in the upper Dawson aquifer, 10 in the lower 
6 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 3. Generalized geologic cross sections A, A–A’, west to east, and B, B–B’, south to north, through the Denver Basin 

aquifer system. See figure 1 for cross section locations and table 1 for bedrock aquifer descriptions within each geologic unit.

7,000

6,000

5,000

4,000

3,000

A' FEET FEET

7,000

6,000

5,000

4,000

3,000

A

FEET

SOUTH NORTH

WEST EAST

7,000

6,000

5,000

4,000

3,000

B'

8,000

FEET

7,000

6,000

5,000

4,000

3,000

B

8,000

VERTICAL EXAGGERATION X 32

NORTH AMERICAN VERTICAL DATUM 1988

Modified from Robson, 1987

A

B

DENVER Watkins

South Platte River

Pierre Shale

Denver Formation Arapahoe Formation

Laramie Formation

Fox Hills Sandstone

Colorado

Springs

Watkins

South Platte River

Pierre Shale

Denver Formation

Arapahoe Formation

Laramie Formation Fox Hills Sandstone

Castle Rock Conglomerate

Dawson Formation

Greeley

0 10 20 30 KILOMETERS

0 10 20 30 MILES

Dawson aquifer, 7 in the Denver aquifer, 9 in the Arapahoe 

aquifer, and 5 in the Laramie-Fox Hills aquifer (table 2, fig. 2). 

Six of these wells were instrumented with a pressure transducer and data logger: 2 in the upper Dawson aquifer, 2 in the 

lower Dawson aquifer, 1 in the Denver aquifer, and 1 in the 

Laramie-Fox Hills aquifer. Instrumented wells were chosen 

on the basis of location, well access, and willingness of well 

owner to allow instrumentation.

Geodetic Survey of Wells

A measuring point (MP) was established on the casing 

of each well as a consistent point from which to make measurements (appendix fig. 1.1). The height of each MP above 

the land surface was manually measured. The elevation of 

each well’s MP was determined using a real-time kinematic 

(RTK)–GNSS, following the methods described in Rydlund 
Table 1. Physical characteristics of bedrock aquifers in the Denver Basin aquifer system.[See figure 1 for extent and location of aquifers and exent and location of Elbert County. mi2, square mile; ft, foot; UDAW, upper Dawson aquifer; LDAW, lower Dawson aquifeARAP, Arapahoe aquifer; LARA, Laramie-Fox Hills aquifer; N/A, not applicable]

Bedrock

aquifer Aquifer

Total 

surface 

area 

(mi2)

Area 

within 

Elbert 

County

(mi2)

Minimum 

thickness 

(ft)

Maximum 

thickness 

(ft)

Average 

wateryielding 

thickness 

(ft)

Composition Age

Upper Dawson UDAW 600 302

100 1,100 100–400

Dawson Formation: interbedded fluvial 

conglomerate, sandstone, siltstone, shale

Tertiary

Lower Dawson LDAW 1,400 423 Denver DENV 3,200 830 600 1,200 100–300

Denver Formation: interbedded shale, 

claystone, siltstone, sandstone, coal, and volcanic ash and rocks

Late Cretaceo

Early Tert

Arapahoe ARAP 4,700 1,160 400 700 200–300

Arapahoe Formation: interbedded conglomerate, sandstone, siltstone, shale Late Cretace

Laramie-Fox 

Hills LARA 7,000 1,538 10 400 150

Laramie Formation: very fine- to 

medium-grained sandstone with interstitial silt and clay Late Cretace

Fox Hills Sandstone Formation: very fine grained silty sandstone and shaly 

siltstone with interbedded shale

Sources:Romero, 1976Kirkham and Ladwig, 1979Schneider, 1980Robson and others, 1981aRobson and others, 1981bRobson, 1987Crifasi, 1992Raynolds and others, 2001Raynolds, 2002Raynolds, 2004Paschke, 2011
8 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 4. Location of wells completed in Denver Basin bedrock aquifers, predicted 100-foot drawdown, well density, and areas of 

interest in the Arapahoe aquifer, for groundwater-level monitoring in Elbert County, Colorado.

ELBERT

ARAPAHOE

EL PASO

WASHINGTON 

LINCOLN

DOUGLAS

<1

1 to 5

>5 to 10

>10 to 20

>20 to 30

>30 to 40 Upper Dawson 

Lower Dawson 

Denver 

Arapahoe 

Laramie Fox Hills 

EXPLANATION

Well density per

 square mile

Elbert County study

 area boundary

Well indicating aquifer of completion

Upper Dawson aquifer

Lower Dawson aquifer

Denver aquifer

Arapahoe aquifer

Laramie-Fox Hills aquifer

>40 to 50

>50 to 75

>75 to 100

Area of interest from the

 combined Observation-

 Parameter statistic for

 the Arapahoe aquifer

 (Paschke, 2011)

High

Low

Predicted 100 feet of drawdown from

 December 31, 2003, to December 31,

 2053 (Paschke, 2011)

Base from U.S. Geological Survey digital data, 2014

Universal Transverse Mercator, Zone 13

North American Datum of 1983

Denver Basin aquifer extent from Paschke, 2011

0 4 8 12 4 KILOMETERS

0 4 8 12 16 MILES

39°30'

39°15'

39°00'

104°45' 104°30' 104°15' 104°00' 103°45'

Kutch

Matheson

Cedar Point

Agate

Bijou

Beck Sand

Draw Crossing

Simla

Elbert

Elizabeth

Fondis

Kiowa

Ponderosa Park

COLORADO

ELBERT

COUNTY
Study Methods 9

and Densmore (2012). The MPs at 39 wells were surveyed in 

July or August 2017, and the MPs at 3 wells were surveyed 

in May 2018. Surveys were completed with a RTK–GNSS 

base station equipped with a radio to communicate with a 

RTK–GNSS rover equipped with a GNSS receiver and a 

data logger. The rover was fixed to a survey rod with known 

height and a bubble level. Each base station was located at a 

fixed position, and a static survey was performed for a period 

of 2–4 hours. The rover was used to identify the coordinates 

and elevation of each MP while communicating with a base 

station. At most wells, the MP was surveyed twice to check 

measurement accuracy. Location data from the base station 

static surveys were submitted to the National Geodetic 

Survey’s Online Positioning User Service (OPUS) web portal 

(National Geodetic Survey, 2018) for processing. The corrected base station data from the OPUS solution were used to 

correct all MP locations, which are projected in the Universal Transverse Mercator (UTM) Zone 13 North coordinate 

system; North American Datum of 1983 (NAD 83) horizontal datum; and North American Vertical Datum of 1988 

(NAVD 88), Geoid 12B, ellipsoid World Geodetic System 

1984 (WGS 84) vertical datum.

The land-surface datum (LSD) of each well was calculated by subtracting the well MP height from the MP elevation 

determined by the survey. Coordinates and elevation for each 

well are summarized in table 2. By computing the elevation of 

LSD for each well on a consistent coordinate system, horizontal datum, and vertical datum, groundwater levels can be 

accurately compared across Elbert County.

Groundwater-Level Measurements and 

Groundwater-Level Elevations

This section presents the methods used for making and 

processing the discrete and continuous groundwater-level 

measurements analyzed in this study. Groundwater levels are 

presented as depth to groundwater in ft. below LSD. Calculated groundwater-level elevations are presented in ft above 

NAVD 88.

Discrete Groundwater-Level Measurements and 

Groundwater-Level Elevations

Groundwater levels were routinely measured in 42 wells 

(table 2) during the study period, April 2015 to June 2018. 

Routine measurements were discontinued at one well, 

common name DENV 13 (table 2), in June 2016 and at 

well LARA 4 in October 2017 because of difficulties with 

well access. Routine measurements were suspended at well 

UDAW 18 from December 2016 to December 2017 during a 

change in property ownership. Manual measurements were 

made bi-monthly (February, April, June, August, October, 

December) except for a few instances when well access was 

temporarily restricted. The procedures for making manual 

groundwater-level measurements are outlined in Cunningham and Schalk (2011), with the exception that a breakaway weight was not used because of concerns it could get 

entangled with pump wiring or piping.

For each measurement, a calibrated steel tape was 

lowered down the well to record the depth to groundwater 

from the well MP (appendix fig. 1.1). In instances where 

a steel tape could not be used (such as excessive moisture 

causing fouled readings, erratic levels due to pumping, difficulties with a well access port), a calibrated electrical tape 

was used (appendix fig. 1.1). In each instance, the depth 

to groundwater from the MP was recorded to the nearest 

0.01 ft and corrected for the height of the MP above LSD to 

give a final reading of measured depth to groundwater below 

LSD. To determine whether the groundwater level measured 

in the well was static and to follow USGS protocol as a 

quality-control measure, a second check measurement was 

made, typically 3–5 minutes after the first. Measurements 

that differed by 0.02 ft or less were considered static and a 

reliable measurement. 

When the check measurement did not agree with the 

original measurement, additional measurements were made 

until the reason for lack of agreement was determined, or 

results were shown to be reliably representative of field conditions. Subsequent measurements were taken to document 

the status of the groundwater level in the well. If consecutive measurements indicated a rising groundwater level 

(decreasing depth to groundwater), the well was considered 

to be recovering from recent pumping, and the highest 

groundwater level (smallest depth to groundwater) measured 

during the field visit was assigned a status of “R,” indicating recently pumped. Typical reasons for recently pumped 

wells include water use for lawn irrigation systems, washing 

machines, or flushing toilets. If consecutive measurements 

indicated a slowly decreasing groundwater level (increasing 

depth to groundwater), the well was considered to be affected 

by one or more wells pumping nearby from the same aquifer, 

and the highest groundwater level measured during the field 

visit was assigned a status of “S,” indicating nearby pumping. Typical reasons for nearby pumping include agricultural 

operations or domestic use. If the pump in the well was 

cycling on and off, the measured depth to groundwater was 

usually erratic and did not follow a pattern. If the well owners were available, they were asked to temporarily suspend 

water use during the field visit so that an “R” status could 

be obtained. If the pump could not be turned off, the highest 

groundwater level (smallest depth to groundwater) measured 

during the field visit was given the status of “P,” indicating 

pumping. Static measurements, which were made 80 percent 

of the time, are ideal for assessing changes and trends in 

aquifer groundwater levels.
Table 2. Well identification and location information, and a summary of discrete groundwater-level measurements from April 2015 to June 2018 in Elbert Co[Site identification numbers in this table are hyperlinked to the data in NWIS Web http://dx.doi.org/10.5066/F7P55KJN. See figure 2 for well locations. Bold, indicates site instrtransducer. Underline, indicates sites with no pump in well. NAD 83, North American Datum of 1983; NAVD 88, North American Vertical Datum of 1988; ft, foot; bls, below lapumped; “S”, nearby pumping; “P”, pumping; LSD, land-surface datum; UDAW, upper Dawson aquifer; LDAW, lower Dawson aquifer; DENV, Denver aquifer; ARAP, ArapahFox Hills aquifer; °, degrees; ‘, minutes; “, seconds] Site identification number Aquifer Common name Latitude (NAD 83) (degrees, minutes, seconds) Longitude (NAD 83) (degrees, minutes, seconds) Elevation of LSD (ft above NAVD 88) Well depth (ft bls) Total measure- ments Number of static measure- ments Number of measure- ments with status “R” Number of measure- ments with status “S” Number o

measure

ments wit

status “P

390935104301001 UDAW DAWMAS26 39° 09' 90935" −104° 30' 010.5" 7,200.00 500 18 12 5 0 1 

391126104354701 UDAW UDAW 19 39° 11' 126.6" −104° 35' 547.8" 7,118.00 401 21 17 4 0 0 

391545104335401 UDAW DAWMAS22 39° 15' 545.5" −104° 33' 354.6" 6,835.00 360 20 20 0 0 0 391915104375001 UDAW UDAW 18 39° 19' 28.24" −104° 37' 50.16" 6,759.62 340 10 9 1 0 0 391924104374101 UDAW UDAW 14 39° 19' 24.51" −104° 37' 46.62" 6,783.97 300 24 24 0 0 0 392130104341401 UDAW UDAW 17 39° 21' 29.54" −104° 34' 15.42" 6,678.27 270 20 12 8 0 0 392133104310201 UDAW UDAW 12 39° 21' 131.9" −104° 31' 06.46" 6,613.45 225 25 25 0 0 0 392203104342301 UDAW UDAW 16 39° 22' 03.34" −104° 34' 22.54" 6,638.05 312 20 20 0 0 0 392355104382001 UDAW UDAW 15 39° 23' 355.8" −104° 38' 820.9" 6,585.00 290 20 18 2 0 0 392856104393801 UDAW UDAW 13 39° 28' 57.89" −104° 39' 38.05" 6,403.45 300 20 19 1 0 0 393016104392601 UDAW UDAW 11 39° 30' 17.99" −104° 39' 26.73" 6,276.70 340 20 19 1 0 0 

391148104294101 LDAW DAWMAS27 39° 11' 148.9" −104° 29' 941.7" 6,960.00 475 20 18 2 0 0 

391502104273601 LDAW LDAW 16 39° 15' 502.2" −104° 27' 735.8" 6,750.00 441 20 6 13 1 0 391829104385301 LDAW LDAW 15 39° 18' 25.51" −104° 38' 49.21" 6,754.82 743 20 13 6 1 0 391848104261401 LDAW DAWMAS28 39° 18' 848.8" −104° 26' 614.9" 6,740.00 388 19 16 3 0 0 391852104391301 LDAW DAWMAS16 39° 18' 52.56" −104° 39' 12.96" 6,798.32 720 20 8 11 1 0 392058104364401 LDAW LDAW 12 39° 20' 58.84" −104° 36' 44.49" 6,606.29 540 22 21 1 0 0 392125104323701 LDAW LDAW 14 39° 21' 25.24" −104° 32' 38.44" 6,599.92 415 20 19 0 1 0 

392131104351701 LDAW DAWMAS21 39° 21' 31.49" −104° 35' 17.53" 6,513.63 435 20 14 6 0 0 

392724104341901 LDAW LDAW 13 39° 27' 727.1" −104° 34' 417.1" 6,305.00 440 20 18 2 0 0 393227104343401 LDAW DAWMAS19 39° 32' 27.27" −104° 34' 34.47" 6,257.95 320 25 24 1 0 0 390755104172501 DENV DENV 17 39° 07' 55.35" −104° 17' 25.48" 6,440.23 480 16 2 13 0 1 391257104173601 DENV DENV 16 39° 12' 58.39" −104° 17' 38.35" 6,298.93 140 20 20 0 0 0 

391811104140301 DENV DENV 15 39° 18' 825.5" −104° 13' 358.1" 6,005.48 280 20 15 5 0 0 

391821104270601 DENV DENV 14 39° 18' 821.6" −104° 27' 706.4" 6,644.00 923 19 14 4 1 0 391851104204501 DENV DENMAS05 39° 18' 851.9" −104° 20' 045.5" 6,080.00 545 20 15 2 0 3 

393012104310701 DENV DENV 13 39° 30' 012.5" −104° 31' 107.3" 6,245.00 534 8 7 1 0 0 393350104151701 DENV DENV 12 39° 33' 51.99" −104° 15' 17.07" 5,587.61 161 23 23 0 0 0 390800104172601 ARAP ARAP 8 39° 08' 00.68" −104° 17' 23.86" 6,426.37 730 20 9 8 0 3 
Table 2. Well identification and location information, and a summary of discrete groundwater-level measurements from April 2015 to June 2018 in Elbert Co[Site identification numbers in this table are hyperlinked to the data in NWIS Web http://dx.doi.org/10.5066/F7P55KJN. See figure 2 for well locations. Bold, indicates site instrtransducer. Underline, indicates sites with no pump in well. NAD 83, North American Datum of 1983; NAVD 88, North American Vertical Datum of 1988; ft, foot; bls, below lapumped; “S”, nearby pumping; “P”, pumping; LSD, land-surface datum; UDAW, upper Dawson aquifer; LDAW, lower Dawson aquifer; DENV, Denver aquifer; ARAP, ArapahFox Hills aquifer; °, degrees; ‘, minutes; “, seconds]

Site

identification 

number

Aquifer Common name

Latitude

(NAD 83)

(degrees,

minutes,

seconds)

Longitude

(NAD 83)

(degrees,

minutes,

seconds)

Elevation of 

LSD

(ft above 

NAVD 88)

Well 

depth

(ft bls)

Total 

measurements

Number 

of static 

measurements

Number of 

measurements with 

status “R”

Number of 

measurements with 

status “S”

Number o

measure

ments wit

status “P

391208104053301 ARAP ARAP 7 39° 12' 09.62" −104° 05' 33.73" 6,131.66 320 20 17 3 0 0 391740104072401 ARAP ARAPMAS27 39° 17' 40.17" −104° 07' 24.14" 5,867.46 130 18 15 3 0 0 391834104205601 ARAP ARAPMAS22 39° 18' 834.6" −104° 20' 42056" 6,140.00 832 20 16 4 0 0 

391946104114501 ARAP ARAP 6 39° 19' 47.26" −104° 11"' 45.41" 6,159.61 580 20 19 1 0 0 

392400104150601 ARAP ARAPMAS28 39° 24' 00.71" −104° 15' 06.36" 5,921.21 434 20 19 1 0 0 392434104142701 ARAP ARAP 5 39° 24' 37.75" −104° 14' 24.48" 6,082.67 425 20 20 0 0 0 393225104073601 ARAP ARAP 4 39° 32' 24.71" −104° 07' 39.92" 5,473.72 287 20 13 7 0 0 

393251104073701 ARAP ARAP 3 39° 32' 52.91" −104° 07' 37.25" 5,487.00 360 20 14 6 0 0 

390817104040301 LARA LARA 7 39° 08' 12.65" −104° 04' 04.33" 5,937.18 438 20 12 6 0 2 391609104014001 LARA LARA 6 39° 16' 12.29" −104° 01' 26.33" 5,753.80 340 20 19 1 0 0 

391621104012001 LARA LARA 5 39° 16' 20.73" −104° 01' 32.11" 5,746.10 400 20 19 1 0 0 

392616103591001 LARA LARA 3 39° 26' 17.16" −103° 59' 11.98" 5,495.98 340 22 22 0 0 0 392635103590001 LARA LARA 4 39° 26' 38.58" −103° 58' 59.23" 5,480.04 221 16 15 1 0 0 
12 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

In this report, groundwater-level elevation is calculated from groundwater level below 

LSD according to the following equation:

Groundwater-level elevation = LSD − Water level below LSD (1)

where

Groundwater-level elevation is groundwater-level elevation, in ft above NAVD 88;

LSD is land-surface datum, in ft above NAVD 88; and

Water level below LSD	 is measured depth, in ft, to groundwater below land-surface 

datum.

Continuous Groundwater-Level Measurements and Groundwater-Level 

Elevations

Six of the 42 wells in the monitoring network were instrumented with a pressure 

transducer containing an internal data logger (table 2, fig. 2). The pressure transducers are 

vented and rated for a 69-ft range in freshwater elevation, with a manufacturer accuracy of 

±0.05 percent at 15 degrees Celsius (In-Situ Inc., 2017). The transducers are suspended in the 

well on a vented communication cable that allows the user to download data from the instrument while the transducer remains in place. The internal data logger was programmed to 

record depth to groundwater below LSD every hour, based on a static manual groundwaterlevel measurement at the time the transducer was deployed, following the methods described 

in Cunningham and Schalk (2011).

Each transducer was downloaded and serviced during each bi-monthly site visit. At the 

time of each manual groundwater-level measurement, a concurrent instantaneous transducer 

groundwater-level measurement was recorded. In instances where the transducer measurement 

had drifted greater than 0.10 ft from the concurrent discrete groundwater-level measurement, 

the data logger was reset to match the discrete value for depth to groundwater. The continuous groundwater-level records were corrected to discrete groundwater-level measurements to 

account for instrument drift. Processing of the continuous groundwater-level measurements 

followed USGS guidelines (Freeman and others, 2004). Like discrete measurements, a continuous hourly record of groundwater-level elevation was calculated using equation 1. Daily values 

of groundwater-level elevations (medians, minimums, and maximums) were derived from the 

hourly groundwater-level elevation values. 

Accessing Data

All discrete and continuous groundwater levels summarized in this report are publicly 

available through the USGS National Water Information System (NWIS) Web Interface at 

http://dx.doi.org/10.5066/F7P55KJN. The NWIS website provides an interface for accessing 

site information and data collected by the USGS and is regularly updated to reflect the most 

current data. Users of the interface can retrieve USGS data by category, region, site number, or 

many other criteria and produce tables and graphs for web viewing or export. In digital copies 

of this publication, site identification numbers in table 2 are hyperlinked to each well’s NWIS 

web page. Data accessible from NWIS can be downloaded in R statistical software with the 

USGS dataRetrieval R package (Hirsch and De Cicco, 2015).

Groundwater-Level Summary, Groundwater-Level Elevation Trend 

Analysis, and Mapping

After measurement of, and corrections to, discrete and continuous groundwater levels, 

all groundwater levels used in this report went through an internal review and an independent approval process. In this report, minimum and maximum groundwater-level elevations 

are summarized by calendar year, and the relative change in groundwater-level elevation is 
Study Methods 13

computed as the difference between the April 2015 and April 2018 measurements. The difference in groundwater-level elevation from April 2015 to April 2018 was chosen so difference 

values would be comparable to those reported in Flor (2017), where differences were computed from measurements typically made in April and May of selected years. At wells with 

continuous hourly groundwater-level elevations, a dataset of daily maximum groundwaterlevel elevations was derived from the maximum hourly groundwater-level elevation measured each day. The daily maximum groundwater-level elevation values tend to represent 

periods of the day when pumping is not occurring at the well or in nearby wells and has not 

occurred recently. Median and minimum daily groundwater-level elevations derived from 

hourly measurements may have been affected by periods of pumping in most cases and thus 

may not reflect static conditions. The daily maximum groundwater-level elevations were used 

for reporting and trend analysis on continuous data.

Trends in groundwater-level elevations throughout Elbert County were determined by 

testing discrete and continuous groundwater-level elevations through time. A linear regression 

(eq. 2) and a linear regression with seasonality terms (eq. 3) (Helsel and Hirsch, 2002) for every 

well in the network were modeled using the R statistical program and the R Stats Package 

(R Core Team, 2018).

Y = β0 + (β1 × T) (2)

where

Y is groundwater-level elevation, in ft above NAVD 88;

T is time, in decimal years;

β0 is intercept, in ft above NAVD 88; and

β1 is slope coefficient of T, in ft/year.

Y = β0 + (β1 × T) + (β2 × sin(2πT)) + (β3 × cos(2πT)) (3)

where

Y is groundwater-level elevation, in ft above NAVD 88;

T is time, in decimal years;

β0 is intercept, in ft above NAVD 88;

β1 is slope coefficient of T, in ft/year;

β2 is coefficient of seasonal sine term, years; and

β3 is coefficient of seasonal cosine term, in years.

The slope coefficient of time (β1) is herein referred to as the trend in groundwater-level 

elevation. Only static groundwater levels were used for trend tests on discrete groundwaterlevel elevations to remove the effect of pumping on trends. A trend test was considered statistically significant when the probability value (p-value) of β1 was less than or equal to 0.10 

and when the coefficient of determination (R2) was greater than or equal to 0.40. A negative 

trend indicates generally declining groundwater-level elevations in the well through time, and 

a positive trend indicates generally rising groundwater-level elevations in the well through 

time. If both trend tests were significant, the test with the highest R2 was reported. Trends in 

groundwater-level elevations through time (ft/year), based on significant trend tests, are summarized by well and by aquifer in this report.

Potentiometric-surface maps show the hydraulic head distribution of an area with contour lines of equal hydraulic head. Groundwater flow is from areas of high hydraulic head to 

areas of low hydraulic head; flow direction is perpendicular to the contours. The Ordinary 

Kriging (default options) and Contour functions in ArcMap Spatial Analyst Toolbox (Esri Inc., 

1999–2016) were used to derive the hydraulic head distribution from static measurements in 

the county. Differences in the hydraulic head distribution from two or more points in time can 

highlight areas where groundwater-level elevations are rising or declining. Hydraulic head 

distributions were derived from static measurements in the upper Dawson and lower Dawson 

aquifers for April 2015 and April 2018.
14 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Groundwater-Level Elevations in the 

Denver Basin Bedrock Aquifers of 

Elbert County

During April 2015 to June 2018, more than 800 discrete 

and 5,800 continuous groundwater-level measurements were 

made in the Elbert County groundwater network. Hydrographs 

showing groundwater-level elevation through time for 

each well in the network are provided in appendix 2.

Discrete Groundwater-Level Elevation Summary 

and Trends

Groundwater levels in each of the Denver Basin bedrock aquifers varied both temporally and spatially. In general, 

groundwater-level elevations were lowest during summer and 

fall and recovered to higher elevations in winter and spring 

(table 3, appendix 2). Some wells exhibited strong seasonal 

fluctuations of several feet (for example, well UDAW 14, 

appendix fig. 2.22), whereas others show minimal seasonality with fluctuations less than 1 ft between measurements (for 

example, well DENV 16, appendix fig. 2.8). Seasonal variations are caused by natural processes, including precipitation 

and evapotranspiration in aquifer zones connected to the land 

surface and timing of aquifer recharge in confined aquifer 

zones (Paschke, 2011). Human activities, such as increased 

irrigation for agriculture (during the growing season) and 

domestic pumping (for lawns), can also affect seasonal variations. Relative changes in discrete groundwater-level elevations between the April 2015 and April 2018 measurements 

are presented in table 3. The 25 wells that exhibited a negative 

change represent a decline in groundwater-level elevation 

between the two measurements, whereas the 13 wells that 

exhibited a positive change represent a rise in groundwaterlevel elevation between the two measurements; 1 well 

exhibited no change. The largest groundwater-level elevation 

declines, based on static measurements, occurred in the lower 

Dawson and Arapahoe aquifers. The largest groundwater-level 

elevation rises, based on static measurements, occurred in 

the upper Dawson aquifer. All aquifers contained at least one 

well where the groundwater-level elevation rose and one well 

where groundwater-level elevation declined from April 2015 

to April 2018. It is important to note that relative changes do 

not represent trends in groundwater-level elevation at a given 

well over the study period.

Of the 42 wells monitored in the study period, 20 exhibited statistically significant trends in groundwater-level elevations, based on the linear regression test (table 4, appendix 

table 3.1). Only wells with significant trends are summarized 

in table 4. Some wells had insufficient static measurements to 

ascertain whether a significant trend existed. Continued monitoring and more static measurements at the wells where trends 

were not significant may increase the likelihood of significant 

trend occurrence at those wells in the future. All aquifers except 

the upper Dawson had more wells with significant negative 

trends in groundwater-level elevations than wells with significant positive trends; however, at least one well within the upper 

Dawson, lower Dawson, and Arapahoe aquifers had a significant positive trend. For all aquifers except the upper Dawson, 

the average trend in groundwater-level elevation was negative, 

indicating generally declining groundwater-level elevations in 

those aquifers (table 4). The upper Dawson aquifer had 2 wells 

with negative trends and 3 wells with positive trends, with an 

average trend of 0.03 ft/year, a maximum positive trend of 

0.28 ft/year, and a maximum negative trend of −0.26 ft/year. 

The lower Dawson aquifer had negative trends at 5 wells and a 

positive trend at only 1 well at the eastern edge of the aquifer’s extent. The average trend in the lower Dawson aquifer 

was −1.96 ft/year, with one positive trend of 0.13 ft/year and a 

maximum negative trend of −4.91 ft/year. The Denver aquifer 

had only one well with a significant trend of −1.04 ft/year. 

The Arapahoe aquifer had 4 wells with negative trends and 

1 well with a positive trend. The average trend in the Arapahoe 

aquifer was −0.46 ft/year; the Arapahoe aquifer had a single 

positive trend of 0.38 ft/year and a maximum negative trend of 

−0.94 ft/year. The Laramie-Fox Hills aquifer had three wells 

with negative trends, an average trend of −0.65 ft/year, and a 

maximum negative trend of −0.73 ft/year. Except for the lower 

Dawson and Denver aquifers, all aquifers had significant trends 

that were within a narrow range of ±1 ft/year. The magnitude 

of negative groundwater-level elevation trends in the lower 

Dawson aquifer had a larger range than the other four aquifers, 

ranging from −0.25 ft/year to −4.91 ft/year, with 4 of the 5 

negative trends in excess of 1 ft/year.

Significant trends are relatively consistent for grouping 

and distribution throughout Elbert County, except for wells 

in the upper Dawson aquifer along the western border of the 

county, which have positive and negative trends (fig. 5). Wells 

that are in very close proximity and in the same aquifer generally agree in trend significance and direction (for example, 

LARA 5 and LARA 6, ARAP 3 and ARAP 4, DAWMAS21 

and LDAW 12). A focus on the Elizabeth-Kiowa and Northwest Planning Areas (Forsgren Associates Inc., 2018) shows 

that the directionality of trends in the upper Dawson aquifer varies by location, whereas trends in the lower Dawson 

aquifer are consistently negative, especially LDAW 12 and 

DAWMAS21 in close proximity to the town of Elizabeth, 

Colo. (fig. 6). The locations of wells with negative trends in the 

lower Dawson aquifer are also central to the aquifer’s extent.

Continuous Groundwater-Level Elevation 

Summary and Trends

Hydrographs of continuous groundwater-level elevations 

from the six wells containing pressure transducers were generally in agreement with discrete groundwater levels measured 

at the same well (appendix fig. 2.22, 2.24, 2.28, 2.33, 2.40, 

2.42). Groundwater-level elevations were generally highest 

during winter and spring and lowest during summer and fall, 

except for DENV 12 (appendix fig. 2.42), which does not have 
Table 3. Summary of discrete groundwater-level elevations, April 2015 to June 2018, Elbert County, Colorado.—Continued[See table 2 and figure 2 for well locations. R15, indicates April 2015 water level has status R (recently pumped). R18, indicates April 18 water level has status R (recently pumped). P15, indicates April P (pumping). P18, indicates April 2018 water level has status P (pumping). See “Study Methods” section for details. ft, foot; NAVD 88, North American Vertical Datum of 1988; UDAW, upper Dawson aquifer; DENV, Denver aquifer; ARAP, Arapahoe aquifer; LARA, Laramie-Fox Hills aquifer; --, no measurements; M, site missing either April 2015 or April 2018 measurement]

Site

identification

number

Aquifer Common name

2015 2016 2017 January 

Maximum

groundwater

elevation

(ft above

NAVD 88)

Date of

maximum

measurement

Minimum

groundwater

elevation

(ft above

NAVD 88)

Date of

minimum

measurement

Maximum

groundwater 

elevation

(ft above

NAVD 88)

Date of

maximum

measurement

Minimum

groundwater

elevation

(ft above

NAVD 88)

Date of 

minimum 

measurement

Maximum 

groundwater 

elevation 

(ft above 

NAVD 88)

Date of 

maximum 

measurement

Minimum 

groundwater 

elevation 

(ft above 

NAVD 88)

Date of 

minimum 

measurement

Maximum 

groundwater 

elevation 

(ft above 

NAVD 88)

Date o

maxim

measu

ment

390935104301001 UDAW DAWMAS26 6,851.60 2015-12-11 6,850.95 2015-10-05 6,851.27 2016-02-15 6,850.38 2016-08-12 6,851.40 2017-02-03 6,851.05 2017-06-16 6,851.49 2018-04

391126104354701 UDAW UDAW 19 6,854.73 2015-12-11 6,854.05 2015-06-15 6,854.68 2016-12-08 6,854.08 2016-08-12 6,854.89 2017-12-05 6,854.29 2017-08-04 6,855.04 2018-04

391545104335401 UDAW DAWMAS22 6,668.98 2015-06-11, 2015-12-11 6,668.07 2015-08-07 6,669.13 2016-06-03 6,668.44 2016-10-07 6,669.42 2017-04-13 6,668.52 2017-08-04 6,669.42 2018-04391915104375001 UDAW UDAW 18 6,597.95 2015-12-14 6,594.23 2015-10-05 6,598.00 2016-06-06 6,594.83 2016-08-10 -- -- -- -- 6,598.16 2018-02391924104374101 UDAW UDAW 14 6,600.57 2015-06-11 6,597.50 2015-10-05 6,600.63 2016-02-19 6,597.77 2016-08-10 6,600.84 2017-02-01 6,598.18 2017-06-26 6,600.63 2018-02392130104341401 UDAW UDAW 17 6,486.41 2015-04-09 6,482.77 2015-10-08 6,486.31 2016-04-04 6,483.26 2016-08-10 6,486.23 2017-02-06 6,483.01 2017-06-26 6,486.32 2018-04392133104310201 UDAW UDAW 12 6,440.41 2015-06-08, 2015-10-02 6,440.11 2015-08-12 6,440.85 2016-12-05 6,440.25 2016-10-06 6,441.06 2017-03-31 6,440.31 2017-08-03 6,441.41 2018-04392203104342301 UDAW UDAW 16 6,454.73 2015-12-03 6,448.77 2015-10-08 6,456.31 2016-12-05 6,447.32 2016-08-10 6,457.70 2017-02-06 6,449.86 2017-06-26 6,457.69 2018-04392355104382001 UDAW UDAW 15 6,396.90 2015-04-10 6,393.50 2015-10-08 6,395.94 2016-02-19 6,392.11 2016-08-10 6,396.25 2017-04-03 6,393.73 2017-06-26 6,396.15 2018-04392856104393801 UDAW UDAW 13 6,239.55 2015-04-10 6,230.64 2015-10-08 6,240.95 2016-04-08 6,228.87 2016-08-12 6,240.27 2017-04-03 6,230.27 2017-08-02 6,240.07 2018-02393016104392601 UDAW UDAW 11 6,180.61 2015-06-10 6,178.01 2015-10-08 6,181.58 2016-06-06 6,179.11 2016-10-04 6,182.46 2017-04-03 6,179.13 2017-10-11 6,181.54 2018-04

391148104294101 LDAW DAWMAS27 6,689.54 2015-06-11 6,688.10 2015-10-05 6,689.73 2016-04-07 6,687.71 2016-08-12 6,689.81 2017-04-13 6,688.54 2017-08-04 6,689.82 2018-04

391502104273601 LDAW LDAW 16 6,602.18 2015-04-02 6,597.77 2015-08-07 6,601.97 2016-04-07 6,597.22 2016-10-07 6,602.54 2017-02-03 6,599.48 2017-04-13 6,602.50 2018-02391829104385301 LDAW LDAW 15 6,556.99 2015-06-11 6,540.94 2015-10-05 6,556.58 2016-06-03 6,537.06 2016-10-07 6,553.21 2017-04-13 6,541.20 2017-08-01 6,552.31 2018-02391848104261401 LDAW DAWMAS28 6,477.84 2015-12-11 6,474.17 2015-08-07 6,476.20 2016-12-08 6,472.59 2016-08-12 6,475.93 2017-04-13 6,473.53 2017-10-04 6,481.28 2018-06391852104391301 LDAW DAWMAS16 6,536.19 2015-04-02 6,506.02 2015-10-05 6,537.70 2016-04-07 6,507.86 2016-10-07 6,531.82 2017-02-03 6,508.96 2017-10-04 6,533.54 2018-04392058104364401 LDAW LDAW 12 6,445.36 2015-04-02 6,417.96 2015-10-05 6,441.14 2016-04-08 6,416.47 2016-08-09 6,437.49 2017-04-03 6,410.56 2017-10-04 6,435.82 2018-04392125104323701 LDAW LDAW 14 6,451.32 2015-04-09 6,447.35 2015-10-01 6,452.27 2016-06-02 6,447.11 2016-08-09 6,452.67 2017-04-03 6,446.60 2017-08-03 6,451.72 2018-02

392131104351701 LDAW DAWMAS21 6,426.25 2015-04-09 6,415.28 2015-10-08 6,424.48 2016-06-06 6,410.72 2016-10-12 6,420.38 2017-04-03 6,408.16 2017-10-12 6,418.96 2018-04

392724104341901 LDAW LDAW 13 6,182.30 2015-06-10 6,174.10 2015-12-10 6,182.47 2016-06-06 6,164.35 2016-10-04 6,178.34 2017-04-03 6,164.58 2017-08-09 6,180.16 2018-04393227104343401 LDAW DAWMAS19 6,046.81 2015-12-14 6,045.89 2015-10-08 6,046.41 2016-12-05 6,045.79 2016-08-11 6,046.20 2017-04-03 6,045.04 2017-12-13 6,045.78 2018-02390755104172501 DENV DENV 17 6,183.88 2015-06-08 6,176.09 2015-12-10 6,179.54 2016-02-12 6,175.46 2016-04-04 6,180.19 2017-12-12 6,168.95 2017-06-15 6,161.15 2018-06391257104173601 DENV DENV 16 6,216.99 2015-04-09 6,216.58 2015-06-08 6,217.02 2016-10-06 6,216.61 2016-04-04 6,216.92 2017-03-31 6,216.54 2017-12-12 6,216.86 2018-04

391811104140301 DENV DENV 15 5,865.73 2015-06-05 5,862.98 2015-04-03 5,865.70 2016-06-01 5,863.98 2016-10-03 5,864.95 2017-01-30 5,863.51 2017-03-30 5,865.77 2018-02

391821104270601 DENV DENV 14 6,404.46 2015-06-11 6,401.05 2015-10-05 6,404.98 2016-06-03 6,399.79 2016-12-08 6,403.82 2017-04-13 6,399.61 2017-10-04 6,402.64 2018-02391851104204501 DENV DENMAS05 5,833.79 2015-06-05 5,779.70 2015-04-03 5,832.96 2016-04-01 5,779.25 2016-06-01 5,832.36 2017-02-06 5,829.88 2017-08-07 5,832.53 2018-04

393012104310701 DENV DENV 13 5,915.61 2015-06-10 5,885.59 2015-08-04, 2015-10-08 5,911.90 2016-02-19 5,907.60 2016-06-06 -- -- -- -- -- -- 393350104151701 DENV DENV 12 5,473.64 2015-12-04 5,473.34 2015-04-03 5,474.02 2016-10-03 5,473.34 2016-04-01 5,473.72 2017-03-30 5,473.13 2017-12-06 5,473.52 2018-06
Table 3. Summary of discrete groundwater-level elevations, April 2015 to June 2018, Elbert County, Colorado.—Continued [See table 2 and figure 2 for well locations. R15, indicates April 2015 water level has status R (recently pumped). R18, indicates April 18 water level has status R (recently pumped). P15, indicates April P (pumping). P18, indicates April 2018 water level has status P (pumping). See “Study Methods” section for details. ft, foot; NAVD 88, North American Vertical Datum of 1988; UDAW, upper Dawson aquifer; DENV, Denver aquifer; ARAP, Arapahoe aquifer; LARA, Laramie-Fox Hills aquifer; --, no measurements; M, site missing either April 2015 or April 2018 measurement] Site identification number Aquifer Common name 2015 2016 2017 January 

Maximum ground- water elevation (ft above NAVD 88) Date of maximum measurement Minimum ground- water elevation (ft above NAVD 88) Date of minimum measurement Maximum ground- water elevation (ft above NAVD 88) Date of maximum measure- ment Minimum ground- water elevation (ft above NAVD 88) Date of minimum measure- ment Maximum ground- water elevation (ft above NAVD 88) Date of maximum measure- ment Minimum ground- water elevation (ft above NAVD 88) Date of minimum measure- ment Maximum ground- water elevation (ft above NAVD 88) Date o

maximu

measur

ment 

390800104172601 ARAP ARAP 8 6,050.72 2015-08-03 6,041.77 2015-10-01 6,051.45 2016-08-11 6,048.77 2016-02-12 6,048.92 2017-08-07 6,044.14 2017-06-15 6,048.37 2018-02391208104053301 ARAP ARAP 7 5,985.15 2015-12-10 5,984.64 2015-08-03 5,984.83 2016-02-12 5,984.24 2016-06-02 5,985.17 2017-03-31 5,984.58 2017-08-07 5,984.62 2018-02391740104072401 ARAP ARAPMAS27 5,810.69 2015-08-03 5,810.28 2015-04-09 5,811.22 2016-06-02 5,810.15 2016-10-06 5,811.58 2017-08-03 5,810.62 2017-06-15 5,811.62 2018-04391834104205601 ARAP ARAPMAS22 5,830.48 2015-06-05 5,828.36 2015-12-03 5,830.09 2016-04-01 5,826.99 2016-08-09 5,829.35 2017-02-06 5,827.80 2017-10-05 5,829.25 2018-02

391946104114501 ARAP ARAP 6 5,867.06 2015-06-05 5,866.84 2015-08-06 5,867.22 2016-06-01 5,860.62 2016-10-03 5,867.74 2017-12-06 5,866.82 2017-01-30 5,868.06 2018-04

392400104150601 ARAP ARAPMAS28 5,715.55 2015-06-05 5,714.33 2015-10-02 5,716.07 2016-06-01 5,714.53 2016-08-08 5,715.85 2017-03-30 5,714.46 2017-07-31 5,715.37 2018-02392434104142701 ARAP ARAP 5 5,749.14 2015-06-05 5,748.19 2015-10-02 5,748.81 2016-02-11 5,745.81 2016-08-08 5,747.79 2017-01-30 5,746.86 2017-10-05 5,747.09 2018-02393225104073601 ARAP ARAP 4 5,423.12 2015-06-05 5,421.63 2015-10-02 5,423.28 2016-06-01 5,421.48 2016-10-03 5,422.95 2017-03-30 5,421.80 2017-06-22, 2017-10-05 5,422.35 2018-04

393251104073701 ARAP ARAP 3 5,379.79 2015-12-04 5,378.16 2015-10-02 5,380.43 2016-02-11 5,368.19 2016-10-03 5,377.17 2017-12-06 5,373.51 2017-07-31 5,377.99 2018-02

390817104040301 LARA LARA 7 5,801.43 2015-06-08 5,796.11 2015-10-01 5,800.89 2016-06-02 5,798.19 2016-10-06 5,800.57 2017-02-02 5,797.01 2017-06-15 5,799.89 2018-02391609104014001 LARA LARA 6 5,609.56 2015-06-08 5,608.72 2015-08-03 5,609.37 2016-06-02 5,607.55 2016-10-06 5,608.54 2017-03-31 5,607.01 2017-10-12 5,607.85 2018-04

391621104012001 LARA LARA 5 5,606.37 2015-06-08 5,605.37 2015-10-01 5,606.05 2016-02-12 5,604.35 2016-10-06 5,605.37 2017-03-31 5,603.90 2017-10-12 5,604.74 2018-04

392616103591001 LARA LARA 3 5,413.41 2015-12-04 5,402.01 2015-06-05 5,414.08 2016-04-01 5,405.35 2016-08-08 5,414.19 2017-03-30 5,403.92 2017-07-31 5,413.61 2018-04392635103590001 LARA LARA 4 5,404.00 2015-12-04 5,387.85 2015-06-05 5,404.77 2016-06-01 5,393.36 2016-08-08 5,404.57 2017-03-30 5,390.35 2017-06-23 -- -- 
Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County 17

Table 4. Statistically significant trends in discrete static groundwater-level elevations, April 2015 to June 2018, Elbert County, 

Colorado.

[See table 2 and figure 2 for well locations. ft, foot; p-value, probability value; R2, coefficient of determination; UDAW, upper Dawson aquifer; LDAW, lower 

Dawson aquifer; DENV, Denver aquifer; ARAP, Arapahoe aquifer; LARA, Laramie-Fox Hills aquifer; <, less than]

Site

identification

number

Aquifer Common

name

Trend in

groundwater 

elevation

(ft/year)

Trend slope

p-value

Linear

regression

R2

391126104354701 UDAW UDAW 19 0.15 0.004 0.69

391924104374101 UDAW UDAW 14 −0.26 0.045 0.75

392130104341401 UDAW UDAW 17 −0.22 0.027 0.89

392133104310201 UDAW UDAW 12 0.21 <0.001 0.69

393016104392601 UDAW UDAW 11 0.28 0.056 0.70

Average: 0.03

391148104294101 LDAW DAWMAS27 0.13 0.005 0.91

391829104385301 LDAW LDAW 15 −1.68 0.046 0.82

392058104364401 LDAW LDAW 12 −4.91 <0.001 0.86

392131104351701 LDAW DAWMAS21 −3.16 <0.001 0.96

392724104341901 LDAW LDAW 13 −1.88 0.012 0.84

393227104343401 LDAW DAWMAS19 −0.25 <0.001 0.59

Average: −1.96

391821104270601 DENV DENV 14 −1.04 0.005 0.67

Average: −1.04

391740104072401 ARAP ARAPMAS27 0.38 <0.001 0.87

391834104205601 ARAP ARAPMAS22 −0.73 0.001 0.63

392434104142701 ARAP ARAP 5 −0.69 <0.001 0.66

393225104073601 ARAP ARAP 4 −0.30 0.020 0.63

393251104073701 ARAP ARAP 3 −0.94 0.001 0.70

Average: −0.46

390817104040301 LARA LARA 7 −0.54 0.043 0.58

391609104014001 LARA LARA 6 −0.73 <0.001 0.84

391621104012001 LARA LARA 5 −0.69 <0.001 0.88

Average: −0.65

a strong seasonal pattern (table 5). Trends in the continuous 

daily maximum groundwater-level elevations agreed with 

the trend direction and magnitude calculated from discrete 

groundwater-level elevations, except for LARA 3, which did 

not have a significant trend in discrete groundwater-level 

elevations, and DENV 12, which did not have significant 

trends for discrete or continuous groundwater-level elevations 

(table 6). 

The trend for discrete data at LARA 3 (appendix fig. 2.33) 

was not significant, but indicates a slightly rising groundwater 

level, whereas the trend for continuous data indicates a slightly 

declining level. The disagreement between continuous and 

discrete data trends may be caused by the pronounced and 

nonuniform seasonal pattern. Adjacent to the well, agricultural 

irrigation operations strongly affect groundwater levels in summer. Discrete measurements at a nearby well (LARA 4, appendix 

fig. 2.34) show a similar drop in summer groundwater levels. 

The hydrograph for LARA 3 (fig. 2.33) shows daily maximum 

groundwater-level elevation data, highlighting the additional 

information that continuous measurements provide about 

groundwater-level changes between discrete measurements. 

The two wells in the upper Dawson aquifer with continuous measurements had differing trend directions. UDAW 14 

(appendix fig. 2.22) exhibited a negative trend of −0.31 ft/year, 

whereas UDAW 12 (appendix fig. 2.28) exhibited a slightly 

positive trend of 0.06 ft/year (table 6). This is consistent with 
18 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

ELBERT

ARAPAHOE

EL PASO

WASHINGTON 

LINCOLN

DOUGLAS ARAPMAS27

ARAPMAS22

ARAP 5

ARAP 4

ARAP 3

DENV 14

LARA 7

LARA 6

LARA 5

DAWMAS27

UDAW 14 UDAW17

DAWMAS21

LDAW 13

DAWMAS19

UDAW 19

LDAW 15

LDAW 12

UDAW 12

UDAW 11

Alluvial deposits 

Upper Dawson 

Lower Dawson 

Denver 

Arapahoe 

Laramie-Fox Hills 

Positive

Negative

No trend

0.13 to 0.5

0.5 to 2.0

2.0 to 5.0

EXPLANATION

Aquifer extent

Elbert County study

 area boundary

Trend

Slope, in feet

 per year

Upper Dawson 

Lower Dawson 

Denver 

Arapahoe 

Laramie Fox Hills 

Well indicating aquifer of completion

Base from U.S. Geological Survey digital data, 2014

Universal Transverse Mercator, Zone 13

North American Datum of 1983

Denver Basin aquifer extent from Paschke, 2011

0 4 8 12 4 KILOMETERS

0 4 8 12 16 MILES

39°30'

39°15'

39°00'

104°45' 104°30' 104°15' 104°00' 103°45'

Kutch

Matheson

Cedar Point

Agate

Bijou

Beck Sand

Draw Crossing

Simla

Elbert

Elizabeth

Fondis

Kiowa

Ponderosa Park

COLORADO

ELBERT

COUNTY

Figure 5. Distribution of significant trends in discrete groundwater-level elevations, by aquifer, Elbert County, Colorado.
Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County 19

Figure 6. Distribution of significant trends in discrete groundwater-level elevations in the upper Dawson and lower Dawson 

aquifers near the towns of Elizabeth and Kiowa, Elbert County, Colorado.

ELBERT

ARAPAHOE

DOUGLAS

DENV 17 Well identification number

DOUGLAS

LDAW 15

LDAW 12

DAWMAS21

LDAW 13

DAWMAS19

UDAW 14

UDAW 17

UDAW 11

UDAW 12

ARAPMAS22

DENV 14

The Pinery

Kiowa

Elizabeth

Franktown

Ponderosa Park

39°30'

39°20'

104°40' 104°30' 104°20'

Alluvial deposits 

Upper Dawson 

Lower Dawson 

Denver 

Positive

Negative

No trend

0.13 to 0.5

0.5 to 2.0

2.0 to 5.0

EXPLANATION

Aquifer extent

Elbert County study

 area boundary

Trend Slope, in feet

 per year Upper Dawson 

Lower Dawson 

Denver 

Arapahoe 

Well indicating aquifer of completion

Base from U.S. Geological Survey digital data, 2014

Universal Transverse Mercator, Zone 13

North American Datum of 1983

Denver Basin aquifer extent from Paschke, 2011

0 1.5 3 4.5 6 KILOMETERS

0 1.5 3 4.5 6 MILES

Parker

COLORADO

ELBERT

COUNTY
Table 5. Statistical summary of continuous daily maximum groundwater-level elevations, January 2016 to June 2018, Elbert County, Colorado. [See table 2 and figure 2 for well locations, and appendix 2 for complete hydrographs. ft, foot; NAVD 88, North American Vertical Datum of 1988; UDAW, upper Dawson aquifaquifer; DENV, Denver aquifer; LARA, Laramie-Fox Hills aquifer; Jan.; January; Feb., February; Mar., March; Apr., April; Aug., August; Sep,. September; Oct., October; Nov.

Site identification number Aquifer Common name 2016 2017 Janua

Maximum ground- water elevation (ft above NAVD 88) Month of maximum Minimum ground- water elevation (ft above NAVD 88) Month of minimum Maximum ground- water elevation (ft above NAVD 88) Month of maximum Minimum ground- water elevation (ft above NAVD 88) Month of minimum Maximum ground- water elevation (ft above NAVD 88) Mon

max

391924104374101 UDAW UDAW 14 6,601.24 May 6,597.45 Aug. 6,601.22 Feb. 6,596.95 Sep. 6,600.81 F392133104310201 UDAW UDAW 12 6,441.32 Dec. 6,440.00 Nov. 6,441.45 Apr. 6,440.13 Oct. 6,441.53 A392058104364401 LDAW LDAW 12 6,443.69 May 6,413.89 Sep. 6,438.73 Mar. 6,411.04 Oct. 6,436.40 A393227104343401 LDAW DAWMAS19 6,046.71 Apr. 6,045.35 Nov. 6,046.69 Mar. 6,044.75 July 6,046.49 F393350104151701 DENV DENV 12 5,474.27 Nov. 5,473.27 Nov. 5,474.14 Mar. 5,473.24 Oct. 5,474.30 F392616103591001 LARA LARA 3 5,414.46 May 5,402.33 Aug. 5,414.47 Apr. 5,401.91 July 5,413.85 A

Table 6. Trends in continuous and discrete daily maximum groundwater-level elevations, 2015 to June 2018, Elbert County Colorado. [See table 2 and figure 2 for well locations. Negative trend values indicate negative trend; positive trend values indicate positive trend. Discrete groundwater level trends from table 4 and table 3.1. POR, period of record; ft, foot; p-value, probability value; R2, coefficient of determination; UDAW, upper Dawson aquifer; LDAW, lower Dawson aquifer; DENV, Denver aquifer; LARA, Laramie-Fox Hills aquifer; italics, indicates trend is not signifcant; <, less than] Site identification number Aquifer Common name POR start date POR end date Trend test Trend in groundwater elevation (ft/year) Trend slope p-value Linear regression R2 391924104374101 UDAW UDAW 14 2015-10-06 2018-06-07 Continuous groundwater elevation trend: −0.31 <0.001 0.85 Discrete groundwater elevation trend: −0.26 0.045 0.75 392133104310201 UDAW UDAW 12 2015-08-13 2018-06-05 Continuous groundwater elevation trend: 0.06 <0.001 0.48 Discrete groundwater elevation trend: 0.21 <0.001 0.69 392058104364401 LDAW LDAW 12 2015-08-08 2018-06-07 Continuous groundwater elevation trend: −3.73 <0.001 0.90 Discrete groundwater elevation trend: −4.91 <0.001 0.86 393227104343401 LDAW DAWMAS19 2015-11-07 2018-06-07 Continuous groundwater elevation trend: −0.18 <0.001 0.49

Discrete groundwater elevation trend: −0.25 <0.001 0.59

393350104151701 DENV DENV 12 2016-02-12 2018-06-03 Continuous groundwater elevation trend: −0.03 <0.001 0.11

Discrete groundwater elevation trend: −0.04 0.354 0.01

392616103591001 LARA LARA 3 2015-08-07 2018-06-03 Continuous groundwater elevation trend: −0.61 <0.001 0.43

Discrete groundwater elevation trend: 0.33 0.626 0.44
Summary 21

trends associated with wells in the upper Dawson aquifer that 

had only discrete measurements; these wells had positive and 

negative trends (table 4). The two wells in the lower Dawson 

aquifer (LDAW12 and DAWMAS19; table 6) have negative 

trends in continuous groundwater-level elevations that are consistent with trends for discrete groundwater-level elevations but 

vary in magnitude. LDAW 12 (appendix fig. 2.24), close to the 

town of Elizabeth, Colo., had a negative trend of −3.73 ft/year, 

whereas farther north DAWMAS19 (appendix fig. 2.40) had a 

negative trend of only −0.18 ft/year (table 6, fig. 6). 

Potentiometric-Surface and Difference Maps

Potentiometric-surface maps were derived from static 

groundwater-level measurements made during April 2015 and 

April 2018 in the upper and lower Dawson aquifers. Only wells 

with a static April 2015 and a static April 2018 measurement 

were used to derive the maps; to remove the effect of pumping on the derivation and to keep the derivation points used by 

ArcMap Spatial Analyst Toolbox consistent between measurement periods. The potentiometric surface as 100-ft-interval 

contours for April 2018, and the differences in hydraulic head 

between April 2015 and April 2018, in the upper and lower 

Dawson aquifers are shown in figures 7 and 8, respectively.

Groundwater flow in the upper and lower Dawson 

aquifers in western Elbert County, based on the derived 

potentiometric-surface maps, is generally from south to north. 

The difference maps of hydraulic head show that the two 

aquifers had lower hydraulic head values along the western 

border of Elbert County in April 2018 than April 2015 

(figs. 7 and fig. 8). Elsewhere in the upper Dawson aquifer, 

the hydraulic head values were generally the same or slightly 

elevated, especially northeast of Elizabeth, Colo., and extending towards the northeastern extent of the aquifer (fig. 7). The 

lower Dawson aquifer had lower hydraulic head values in most 

of the study area, with the greatest differences near Elizabeth, 

Colo., and extending towards the western border (fig. 8). Only 

small parts of the lower Dawson aquifer between Elizabeth and 

Kiowa, Colo., and southeast of Elbert, Colo., had higher head 

values in April 2018 than in April 2015 (fig. 8). 

Negative trends in groundwater-level elevations in the 

upper and lower Dawson aquifers in the western part of the 

county could coincide with increased development in Elbert 

County and Douglas County. According to the CDWR well 

permit database (Colorado Department of Natural Resources, 

2018), from January 2015 to June 2018, 335 new domestic 

water-supply wells were constructed in the upper and lower 

Dawson aquifers, mostly in eastern Douglas County and 

western Elbert County. Parts of the upper and lower Dawson 

aquifers in Elbert County where levels are rising, coinciding 

with positive changes and trends, could indicate the presence 

of outcrops of the aquifers that are localized recharge zones, 

especially towards the outer extent of the lower Dawson 

aquifer where unconfined flow conditions may exist and in the 

upper Dawson aquifer, which is unconfined throughout and 

has the greater recharge (Paschke, 2011). 

Future Work

Results from this study can be used to focus future monitoring efforts and aid local water-resource managers with decisions on water use within Elbert County. Continued monitoring 

and analysis are needed to confirm whether the groundwaterlevel elevation comparisons and trends from this study persist 

beyond the study period. Continued monitoring and more 

static measurements at wells with no significant trend in this 

study may lead to significant trends in the future by providing 

more data points as input to linear regressions. Additionally, 

instrumenting more wells with continuous groundwater-level 

monitors would provide a more in-depth record of patterns in 

groundwater levels between discrete measurements. Future 

monitoring efforts can focus less on aquifers with small 

groundwater-level declines and areas with little development 

in the eastern part of the county and focus more on aquifers 

with substantial negative trends and areas experiencing greater 

development. Additional monitoring could include soliciting 

more homeowners for well access, measuring water levels in or 

instrumenting existing CDWR wells, or installing new monitoring wells in the county. A regional study and analysis that 

includes groundwater-level data from other monitoring networks in the Denver Basin aquifer system could provide a better 

understanding of how groundwater levels are changing beyond 

the Elbert County border and how those changes could affect 

groundwater resources in Elbert County. The regional study 

could produce regional water-level trend maps and regional 

potentiometric surface and hydraulic-head difference maps. It 

could provide additional calibration data, which could be used 

to update and improve the Denver Basin groundwater model. 

Summary

Residents in Elbert County, Colorado, rely on groundwater withdrawals to meet public and domestic water-supply 

needs throughout the county. Withdrawals from the five 

bedrock aquifers in the Denver Basin aquifer system (lower 

Dawson, upper Dawson, Denver, Arapahoe, and LaramieFox Hills) in Elbert County and in neighboring counties have 

increased to meet the demand of a growing population. The 

U.S. Geological Survey, in cooperation with the Elbert County 

Board of County Commissioners, began a study in 2015 to 

establish a network of wells and measure groundwater levels 

on a bi-monthly interval. Six of the 42 wells in the study were 

instrumented with pressure transducers to record groundwater levels hourly. The purposes of this study were to measure 

groundwater levels between April 2015 and June 2018 and 

analyze groundwater-level elevation changes and trends 

throughout the county.

Measurements made in all wells were used to calculate 

changes and trends in groundwater-level elevations in all five 

Denver Basin bedrock aquifers within Elbert County. Relative 

changes between April 2015 and April 2018 were calculated 

using discrete measurements. Trends were calculated using 
22 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

ELBERT

ARAPAHOE

DOUGLAS

6,400

6,500

6,600

6,800

6,300

6,700

6,200

UDAW 15

DAWMAS22

UDAW 12

UDAW 11

UDAW 14

DAWMAS26

UDAW 19

UDAW 16

−0.81 to −0.01 

0.00 to 2.00

2.01 to 3.62

EXPLANATION

Well and identification number

Elbert County study area boundary

6,800

UDAW 19

Estimated potentiometric contour

 April 2018, in feet above NAVD 88,

contour interval 100 feet

Difference in hydraulic head, April

 2018 to April 2015, in feet

Base from U.S. Geological Survey digital data, 2014

Universal Transverse Mercator, Zone 13

North American Datum of 1983 0 2 4 6 8 10 KILOMETERS

0 2 4 6 8 10 MILES

104°50' 104°40' 104°30' 104°20'

39°30'

39°20'

39°10'

Fondis

Elizabeth

Elbert

Kiowa

Ponderosa Park

COLORADO

ELBERT

COUNTY

Figure 7. Estimated potentiometric surface of the upper Dawson aquifer in April 2018 and change in hydraulic head between 

April 2015 and April 2018, western Elbert County, Colorado.
Summary 23

Figure 8. Estimated potentiometric surface of the lower Dawson aquifer in April 2018 and change in hydraulic head between April 

2015 and April 2018, western Elbert County, Colorado.

ELBERT

ARAPAHOE

DOUGLAS

6,400

6,200

6,600

6,500

6,100

6,300

DAWMAS27

LDAW 12

LDAW 13

LDAW 15

DAWMAS19

DAWMAS28

DAWMAS21

LDAW 14

−10.00 to −8.01

−8.00 to −6.01

−6.00 to −4.01

EXPLANATION

Well and identification number

Elbert County study area boundary

−4.00 to −2.01

−2.00 to −0.01

0.00 to 2.00

6,800

LDAW 15

Estimated potentiometric contour

 April 2018, in feet above NAVD 88,

contour interval 100 feet

Difference in hydraulic head, April

 2018 to April 2015, in feet

Base from U.S. Geological Survey digital data, 2014

Universal Transverse Mercator, Zone 13

North American Datum of 1983 0 2 4 6 8 10 KILOMETERS

0 2 4 6 8 10 MILES

104°50' 104°40' 104°30' 104°20'

39°20'

39°30'

39°10'

Ponderosa Park

Elizabeth Kiowa

Elbert Fondis

COLORADO

ELBERT

COUNTY
24 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

linear regression models, static discrete groundwater-level 

elevations, and continuous daily maximum groundwater-level 

elevations. The spatial distribution of hydraulic head in April 

2018, and the relative changes in hydraulic head from April 

2015 to April 2018, were mapped in the upper Dawson and 

lower Dawson aquifers.

All five aquifers had wells with a rise in groundwaterlevel elevation and wells with a decline in groundwaterlevel elevation, based on the relative change in the groundwater-level elevation between the April 2015 and April 

2018 measurements. The upper Dawson, lower Dawson, 

Denver, Arapahoe, and Laramie-Fox Hills aquifers had 

average trends of 0.03 foot per year (ft/year), −1.96 ft/year, 

−1.04 ft/year, −0.46 ft/year, and −0.65 ft/year, respectively. 

Trends in groundwater-level elevations in the upper Dawson 

aquifer were not consistent. Some wells had declining levels 

and some rising levels, but all trends in this aquifer were 

within a range of ± 1 ft/year. The heterogeneity in trend 

direction and location could be an indication of local zones 

of recharge. The magnitude of negative groundwater-level 

elevation trends in the lower Dawson aquifer had a larger 

range than the other four aquifers, ranging from −0.25 ft/year 

to −4.91 ft/year, with 4 of 5 negative trends in excess of 

1 ft/year and an average discrete trend of −1.96 ft/year. 

Negative trends in the lower Dawson aquifer were concentrated along the western border of Elbert County, which is 

central to the aquifer’s extent. The only positive trend in 

groundwater-level elevation in the lower Dawson aquifer 

occurred for a well at the eastern edge of the aquifer’s extent. 

Of the seven wells where water levels were monitored in the 

Denver aquifer, a statistically significant trend was observed 

in only one well (-1.04 ft/year). A longer study period and 

more static measurements could increase the frequency of 

significant trends. Like trends for the upper Dawson aquifer, 

groundwater-level elevation trends at wells in the Arapahoe 

aquifer and Laramie-Fox Hills aquifer were all within a 

range of ± 1 ft/year. Trends in continuous groundwaterlevel elevations were in agreement with significant trends in 

discrete groundwater-level elevations. Potentiometric-surface 

maps of the upper and lower Dawson aquifers for April 2015 

and April 2018 show that differences in hydraulic head from 

the two measurement periods were greatest along the western 

part of Elbert County. 

Results of this study can be used by local water-resource 

managers to make decisions about water use within Elbert 

County and could be used to guide future groundwater monitoring options. Results also could be used for a regional study 

of groundwater-level elevations in the Denver Basin aquifer 

system to provide additional calibration data for the Denver 

Basin groundwater flow model.

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Publishing support provided by the Science Publishing Network, 

Denver Publishing Service Center

For more information concerning the research in this report, contact the

Director, USGS Colorado Water Science Center

Box 25046, Mail Stop 415

Denver, CO 80225

(303) 236-4882

Or visit the Colorado Water Science Center website at

https://co.water.usgs.gov/
Appendix 1 27

Appendix 1. Groundwater-Well Measurement Diagram

Figure 1.1. Diagram showing example measurement point and groundwater-level measurement using A, a calibrated steel 

tape with chalk, and B, a calibrated electrical tape. Modified from Cunningham and Schalk, 2011. (Values are in feet)

Measuring

point (MP)

MP hold

0.85

Water level

1.28

(Wetted

chalk mark)

Well

casing

Land-surface

datum (LSD)

12.86 (Depth to water corrected for LSD)

14.99

13.71 (Depth to water from MP)

1’

Measuring

point (MP)

MP hold

0.85

Water level

Well

casing

Land-surface

datum (LSD)

12.86 (Depth to water corrected for LSD)

13.71 (Depth to water from MP)

A B

Appendix 1
28 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Appendix 2. Hydrographs Showing Groundwater-Level Elevation Through Time 

for Wells in the Elbert County Groundwater-Level Monitoring Network.

Hydrographs showing groundwater-level elevation through time for each well in this study are presented in this appendix. 

Measurement periods vary but are generally from April 2015 to June 2018 for discrete measurements and summer/fall 2015 to 

June 2018 for continuous measurements. Daily maximum groundwater-level elevation, in feet above North American Vertical 

Datum of 1988, is plotted for continuous measurements. Daily median and minimum values were not plotted, but data are 

available; see the “Accessing Data” section. Discrete measurement symbols vary by status; see “Study Methods” section for a 

description of the status codes. UDAW, upper Dawson aquifer; LDAW, lower Dawson aquifer; DENV, Denver aquifer; ARAP, 

Arapahoe aquifer; LARA, Laramie-Fox Hills aquifer. 

Figure 2.1. Groundwater-level hydrograph for DENV 17, USGS site number 390755104172501, 

Elbert County, Colorado.

6,158

6,160

6,162

6,164

6,166

6,168

6,170

6,172

6,174

6,176

6,178

6,180

6,182

6,184

6,186

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

EXPLANATION

Groundwater level

Static

Recently pumped

Pumping

Appendix 2

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,021

6,023

6,025

6,027

6,029

6,031

6,033

6,035

6,037

6,039

6,041

6,043

6,045

6,047

6,049

6,051

6,053

EXPLANATION

Groundwater level

Static

Recently pumped

Pumping

Figure 2.2. Groundwater-level hydrograph for ARAP 8, USGS site number 390800104172601, 

Elbert County, Colorado.
Appendix 2 29

Figure 2.4. Groundwater-level hydrograph for DAWMAS26, USGS site number 390935104301001, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,849

6,850

6,851

6,852

6,853

EXPLANATION

Groundwater level

Static

Recently pumped

Pumping

Figure 2.3. Groundwater-level hydrograph for LARA 7, USGS site number 390817104040301, 

Elbert County, Colorado.

\\IGSKAHCMVSFS002\Jeff\den19-0011_penn\den19-0011_fig02.03.ai

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,794

5,796

5,798

5,800

5,802

5,804

EXPLANATION

Groundwater level

Static

Recently pumped

Pumping
30 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 2.6. Groundwater-level hydrograph for DAWMAS27, USGS site number 391148104294101, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,686

6,687

6,688

6,689

6,690

6,691

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.5. Groundwater-level hydrograph for UDAW 19, USGS site number 391126104354701, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,853

6,854

6,855

6,856

6,857 EXPLANATION

Groundwater level

Static

Recently pumped
Appendix 2 31

Figure 2.7. Groundwater-level hydrograph for ARAP 7, USGS site number 391208104053301, 

Elbert County, Colorado.

5,983

5,984

5,985

5,986

5,987

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.8. Groundwater-level hydrograph for DENV 16, USGS site number 391257104173601, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,215

6,216

6,217

6,218

6,219 EXPLANATION

Groundwater level status

Static
32 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 2.10. Groundwater-level hydrograph for DAWMAS22, USGS site number 391545104335401, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,667

6,668

6,669

6,670

6,671

EXPLANATION

Groundwater level

Static

Figure 2.9. Groundwater-level hydrograph for LDAW 16, USGS site number 391502104273601, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,595

6,597

6,599

6,601

6,603

6,605

EXPLANATION

Groundwater level

Static

Recently pumped

Nearby pumping
Appendix 2 33

Figure 2.11. Groundwater-level hydrograph for LARA 6, USGS site number 391609104014001, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,605

5,606

5,607

5,608

5,609

5,610

5,611

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.12. Groundwater-level hydrograph for LARA 5, USGS site number 391621104012001, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,602

5,603

5,604

5,605

5,606

5,607

5,608 EXPLANATION

Groundwater level

Static

Recently pumped
34 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 2.14. Groundwater-level hydrograph for DENV 15, USGS site number 391811104140301, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,861

5,862

5,863

5,864

5,865

5,866

5,867

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.13. Groundwater-level hydrograph for ARAPMAS27, USGS site number 391740104072401, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,809

5,810

5,811

5,812

5,813 EXPLANATION

Groundwater level

Static

Recently pumped
Appendix 2 35

Figure 2.15. Groundwater-level hydrograph for DENV 14, USGS site number 391821104270601, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,397

6,399

6,401

6,403

6,405

6,407

EXPLANATION

Groundwater level

Static

Recently pumped

Nearby pumping

Figure 2.16. Groundwater-level hydrograph for LDAW 15, USGS site number 391829104385301, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,535

6,537

6,539

6,541

6,543

6,545

6,547

6,549

6,551

6,553

6,555

6,557

6,559

EXPLANATION

Groundwater level

Static

Recently pumped

Nearby pumping
36 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 2.18. Groundwater-level hydrograph for DAWMAS28, USGS site number 391848104261401, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,470

6,472

6,474

6,476

6,478

6,480

6,482

6,484

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.17. Groundwater-level hydrograph for ARAPMAS22, USGS site number 391834104205601, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,823

5,825

5,827

5,829

5,831

5,833

EXPLANATION

Groundwater level

Static

Recently pumped
Appendix 2 37

Figure 2.19. Groundwater-level hydrograph for DENMAS05, USGS site number 391851104204501, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,774

5,779

5,784

5,789

5,794

5,799

5,804

5,809

5,814

5,819

5,824

5,829

5,834

5,839

EXPLANATION

Groundwater level

Static

Recently pumped

Pumping

Figure 2.20. Groundwater-level hydrograph for DAWMAS16, USGS site number 391852104391301, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,501

6,506

6,511

6,516

6,521

6,526

6,531

6,536

6,541

EXPLANATION

Groundwater level

Static

Recently pumped

Nearby pumping
38 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 2.22. Groundwater-level hydrograph for UDAW 14, USGS site number 391924104374101, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,594

6,596

6,598

6,600

6,602

6,604

EXPLANATION

Groundwater level

Static

Continuous record

 groundwater level

Daily maximum

Figure 2.21. Groundwater-level hydrograph for UDAW 18, USGS site number 391915104375001, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,593

6,594

6,595

6,596

6,597

6,598

6,599

6,600

EXPLANATION

Groundwater level

Static

Recently pumped
Appendix 2 39

Figure 2.23. Groundwater-level hydrograph for ARAP 6, USGS site number 391946104114501, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,858

5,860

5,862

5,864

5,866

5,868

5,870

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.24. Groundwater-level hydrograph for LDAW 12, USGS site number 392058104364401, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,405

6,410

6,415

6,420

6,425

6,430

6,435

6,440

6,445

6,450

Groundwater level

Static

Recently pumped

EXPLANATION

Continuous record

 groundwater level

Daily maximum
40 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 2.26. Groundwater-level hydrograph for UDAW 17, USGS site number 392130104341401, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,481

6,482

6,483

6,484

6,485

6,486

6,487

6,488

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.25. Groundwater-level hydrograph for LDAW 14, USGS site number 392125104323701, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,444

6,446

6,448

6,450

6,452

6,454

EXPLANATION

Groundwater level

Static

Nearby pumping
Appendix 2 41

Figure 2.27. Groundwater-level hydrograph for DAWMAS21, USGS site number 392131104351701, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,406

6,408

6,410

6,412

6,414

6,416

6,418

6,420

6,422

6,424

6,426

6,428

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.28. Groundwater-level hydrograph for UDAW 12, USGS site number 392133104310201, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,439

6,440

6,441

6,442

6,443

EXPLANATION

Groundwater level

Static

Continuous record

 groundwater level

Daily maximum
42 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 2.30. Groundwater-level hydrograph for UDAW 15, USGS site number 392355104382001, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,391

6,392

6,393

6,394

6,395

6,396

6,397

6,398

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.29. Groundwater-level hydrograph for UDAW 16, USGS site number 392203104342301, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,445

6,447

6,449

6,451

6,453

6,455

6,457

6,459

EXPLANATION

Groundwater level

Static
Appendix 2 43

Figure 2.31. Groundwater-level hydrograph for ARAPMAS28, USGS site number 392400104150601, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,713

5,714

5,715

5,716

5,717

5,718

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.32. Groundwater-level hydrograph for ARAP 5, USGS site number 392434104142701, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,744

5,745

5,746

5,747

5,748

5,749

5,750

5,751

EXPLANATION

Groundwater level

Static
44 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 2.34. Groundwater-level hydrograph for LARA 4, USGS site number 392635103590001, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,385

5,387

5,389

5,391

5,393

5,395

5,397

5,399

5,401

5,403

5,405

5,407

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.33. Groundwater-level hydrograph for LARA 3, USGS site number 392616103591001, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,399

5,401

5,403

5,405

5,407

5,409

5,411

5,413

5,415

5,417

EXPLANATION

Groundwater level

Static

Continuous record

 groundwater level

Daily maximum
Appendix 2 45

Figure 2.35. Groundwater-level hydrograph for LDAW 13, USGS site number 392724104341901, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,162

6,164

6,166

6,168

6,170

6,172

6,174

6,176

6,178

6,180

6,182

6,184

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.36. Groundwater-level hydrograph for UDAW 13, USGS site number 392856104393801, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,226

6,228

6,230

6,232

6,234

6,236

6,238

6,240

6,242

EXPLANATION

Groundwater level

Static

Recently pumped
46 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 2.38. Groundwater-level hydrograph for UDAW 11, USGS site number 393016104392601, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,177

6,178

6,179

6,180

6,181

6,182

6,183

6,184

EXPLANATION

Groundwater level

Static

Recently pumped

Figure 2.37. Groundwater-level hydrograph for DENV 13, USGS site number 393012104310701, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,880

5,885

5,890

5,895

5,900

5,905

5,910

5,915

5,920

EXPLANATION

Groundwater level

Static

Recently pumped
Appendix 2 47

Figure 2.40. Groundwater-level hydrograph for DAWMAS19, USGS site number 393227104343401, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

6,043

6,044

6,045

6,046

6,047

6,048

Groundwater level

Static

Recently pumped

EXPLANATION

Continuous record

 groundwater level

Daily maximum

Figure 2.39. Groundwater-level hydrograph for ARAP 4, USGS site number 393225104073601, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,420

5,421

5,422

5,423

5,424

5,425

EXPLANATION

Groundwater level

Static

Recently pumped
48 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Figure 2.42. Groundwater-level hydrograph for DENV 12, USGS site number 393350104151701, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,472

5,473

5,474

5,475

5,476 EXPLANATION

Groundwater level

Static

Continuous record

 groundwater level

Daily maximum

Figure 2.41. Groundwater-level hydrograph for ARAP 3, USGS site number 393251104073701, 

Elbert County, Colorado.

2015 2016 2017 2018 2019

Date

Groundwater elevation above North A

merican

Vertical Datum of 1988, in feet

5,366

5,368

5,370

5,372

5,374

5,376

5,378

5,380

5,382

EXPLANATION

Groundwater level

Static

Recently pumped
Appendix 3 49

Appendix 3. Discrete Groundwater-Level Elevation Trends

Appendix 3 Table 3.1. Trends in discrete static groundwater-level elevations, April 2015 to June 2018, Elbert County, Colorado.—Continued

[See table 2 and figure 2 for well locations. ft, foot; p-value, probability value; R2, coefficient of determination; UDAW, upper Dawson aquifer; LDAW, lower 

Dawson aquifer; DENV, Denver aquifer; ARAP, Arapahoe aquifer; LARA, Laramie-Fox Hills aquifer; Lin. Reg., Linear Regression; Lin. Reg. Seas., Linear 

Regression with Seasonality terms; --, insufficient data to compute trend; <, less than] 

Site

identification

number

Aquifer Common

name

Trend

test

Trend in 

grounwater

level (ft/year)

Trend

slope 

p-value

Linear

regression

R2

390935104301001 UDAW DAWMAS26 Lin. Reg. −0.01 0.943 −0.10

Lin. Reg. Seas. −0.02 0.777 0.35

391126104354701 UDAW UDAW 19 Lin. Reg. 0.15 0.043 0.20

Lin. Reg. Seas. 0.15 0.004 0.69

391545104335401 UDAW DAWMAS22 Lin. Reg. 0.12 0.219 0.03

Lin. Reg. Seas. 0.09 0.130 0.61

391915104375001 UDAW UDAW 18 Lin. Reg. −0.26 0.592 −0.09

Lin. Reg. Seas. −0.53 0.186 0.58

391924104374101 UDAW UDAW 14 Lin. Reg. −0.17 0.498 −0.02

Lin. Reg. Seas. −0.26 0.045 0.75

392130104341401 UDAW UDAW 17 Lin. Reg. 0.03 0.894 −0.10

Lin. Reg. Seas. −0.22 0.027 0.89

392133104310201 UDAW UDAW 12 Lin. Reg. 0.25 <0.001 0.48

Lin. Reg. Seas. 0.21 <0.001 0.69

392203104342301 UDAW UDAW 16 Lin. Reg. 0.79 0.326 0.00

Lin. Reg. Seas. 0.45 0.236 0.78

392355104382001 UDAW UDAW 15 Lin. Reg. −0.24 0.470 −0.03

Lin. Reg. Seas. −0.24 0.168 0.75

392856104393801 UDAW UDAW 13 Lin. Reg. −0.07 0.948 −0.06

Lin. Reg. Seas. −0.70 0.146 0.82

393016104392601 UDAW UDAW 11 Lin. Reg. 0.31 0.206 0.04

Lin. Reg. Seas. 0.28 0.056 0.70

391148104294101 LDAW DAWMAS27 Lin. Reg. 0.15 0.237 0.03

Lin. Reg. Seas. 0.13 0.005 0.91

391502104273601 LDAW LDAW 16 Lin. Reg. −0.21 0.675 −0.19

Lin. Reg. Seas. −0.41 0.347 0.42

391829104385301 LDAW LDAW 15 Lin. Reg. −0.72 0.674 −0.07

Lin. Reg. Seas. −1.68 0.046 0.82

391848104261401 LDAW DAWMAS28 Lin. Reg. 0.22 0.710 −0.06

Lin. Reg. Seas. 0.37 0.528 −0.03

391852104391301 LDAW DAWMAS16 Lin. Reg. −2.06 0.746 −0.14

Lin. Reg. Seas. −0.03 0.983 0.94

392058104364401 LDAW LDAW 12 Lin. Reg. −3.23 0.188 0.04

Lin. Reg. Seas. −4.91 <0.001 0.86

392125104323701 LDAW LDAW 14 Lin. Reg. −0.03 0.944 −0.06

Lin. Reg. Seas. −0.25 0.346 0.71

392131104351701 LDAW DAWMAS21 Lin. Reg. −2.91 0.048 0.23

Lin. Reg. Seas. −3.16 <0.001 0.96

392724104341901 LDAW LDAW 13 Lin. Reg. −2.65 0.104 0.10

Lin. Reg. Seas. −1.88 0.0120 0.84

393227104343401 LDAW DAWMAS19 Lin. Reg. −0.28 <0.001 0.41

Lin. Reg. Seas. −0.25 <0.001 0.59
50 Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Table 3.1. Trends in discrete static groundwater-level elevations, April 2015 to June 2018, Elbert County, Colorado.—Continued

[See table 2 and figure 2 for well locations. ft, foot; p-value, probability value; R2, coefficient of determination; UDAW, upper Dawson aquifer; LDAW, lower 

Dawson aquifer; DENV, Denver aquifer; ARAP, Arapahoe aquifer; LARA, Laramie-Fox Hills aquifer; Lin. Reg., Linear Regression; Lin. Reg. Seas., Linear 

Regression with Seasonality terms; --, insufficient data to compute trend; <, less than] 

Site

identification

number

Aquifer Common

name

Trend

test

Trend in 

grounwater

level (ft/year)

Trend

slope 

p-value

Linear

regression

R2

390755104172501 DENV DENV 17 Lin. Reg. −60.02 -- --

Lin. Reg. Seas. −60.02 -- --

391257104173601 DENV DENV 16 Lin. Reg. 0.01 0.733 −0.05

Lin. Reg. Seas. 0.01 0.829 −0.12

391811104140301 DENV DENV 15 Lin. Reg. −0.16 0.297 0.01

Lin. Reg. Seas. −0.18 0.148 0.41

391821104270601 DENV DENV 14 Lin. Reg. −1.12 0.017 0.34

Lin. Reg. Seas. −1.04 0.005 0.67

391851104204501 DENV DENMAS05 Lin. Reg. 1.44 0.444 −0.03

Lin. Reg. Seas. 1.08 0.574 −0.05

393012104310701 DENV DENV 13 Lin. Reg. 0.96 0.945 −0.20

Lin. Reg. Seas. −1.55 0.861 0.55

393350104151701 DENV DENV 12 Lin. Reg. −0.05 0.307 0.00

Lin. Reg. Seas. −0.04 0.354 0.01

390800104172601 ARAP ARAP 8 Lin. Reg. −0.17 0.704 −0.12

Lin. Reg. Seas. 0.56 0.323 0.38

391208104053301 ARAP ARAP 7 Lin. Reg. −0.83 0.060 0.16

Lin. Reg. Seas. −0.79 0.087 0.12

391740104072401 ARAP ARAPMAS27 Lin. Reg. 0.38 <0.001 0.87

Lin. Reg. Seas. 0.38 <0.001 0.87

391834104205601 ARAP ARAPMAS22 Lin. Reg. −0.63 0.017 0.30

Lin. Reg. Seas. −0.73 0.001 0.63

391946104114501 ARAP ARAP 6 Lin. Reg. 0.38 0.314 0.00

Lin. Reg. Seas. 0.36 0.326 0.05

392400104150601 ARAP ARAPMAS28 Lin. Reg. 0.01 0.931 −0.06

Lin. Reg. Seas. −0.03 0.719 0.43

392434104142701 ARAP ARAP 5 Lin. Reg. −0.66 <0.001 0.55

Lin. Reg. Seas. −0.69 <0.001 0.66

393225104073601 ARAP ARAP 4 Lin. Reg. −0.23 0.193 0.07

Lin. Reg. Seas. −0.30 0.020 0.63

393251104073701 ARAP ARAP 3 Lin. Reg. −0.87 0.012 0.37

Lin. Reg. Seas. −0.94 0.001 0.70

390817104040301 LARA LARA 7 Lin. Reg. −0.74 0.014 0.41

Lin. Reg. Seas. −0.54 0.043 0.58

391609104014001 LARA LARA 6 Lin. Reg. −0.70 <0.001 0.66

Lin. Reg. Seas. −0.73 <0.001 0.84

391621104012001 LARA LARA 5 Lin. Reg. −0.65 <0.001 0.66

Lin. Reg. Seas. −0.69 <0.001 0.88

392616103591001 LARA LARA 3 Lin. Reg. 0.52 0.566 −0.03

Lin. Reg. Seas. 0.33 0.626 0.44

392635103590001 LARA LARA 4 Lin. Reg. −0.38 0.866 −0.07

Lin. Reg. Seas. 0.35 0.839 0.43

Penn and Everett—Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18—SIR 2019–5014

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20195014