1) Water level data from the edges of the Denver Basin do not show consistent declines as some reports have suggested. Data from multiple locations show stable or rising water levels over several years. 2) Accurate water level data collection requires proper methods, timing of measurements, probe calibration, and accounting for time since well rehabilitation. Inconsistent or infrequent data collection can lead to incorrect conclusions about water level trends. 3) While some areas have seen water level declines, the Denver Basin aquifers as a whole still contain large volumes of groundwater. Improved data collection and sharing is needed to better understand groundwater conditions across the basin.

1. Living on the Edge in the Denver Basin:
Fact or Fiction?
Theresa Jehn-Dellaport, P.G.
Matthew J. Welsh
Jehn Water Consultants, Inc.

2. Introduction
 Overview of the
Denver Basin
 Recent focus on
water level trends
 Data Collection
Methods
 Results of Accurate
Data Collection from
the edges of the
Basin

5. Denver Basin Geologic Cross-
section
G G’
Quaternary Deposits
Late Eocene Rocks
Dawson Group Sequence D1
Dawson Group Sequence D2
Laramie Formation
Fox Hills Sandstone
Pierre Shale
Modified from: Barkmann, P. Denver Basin Field Trip Guide

6. District 8

7. Recent Studies
 South Metro Water Supply (SMWSA)
Study, 2003
 Colorado Water Conservation Board
Statewide Water Supply Initiative, 2004;
 SMWSA Regional Master Plan, 2007;
 Citizen’s Guide to Denver Basin
Groundwater, 2007;
 Draft SMWSA Regional Aquifer
Assessment, 2010;
 Several Others.

8. Water Sources in South Metro Area
(SMWSA, 2007)

9. Denver Basin Use in South Metro
Area
 ~467,000,000 af total in Denver Basin
 ~83,000,000 af total in District 8
 ~35,000 af used in District 8 in 2008
 556 af injected in 2008

10. Water Use in District 8
Total Available
(af/yr)
Total Withdrawn
2008 (af/yr)
Injected 2008 (af/yr)

11. The Sky is Falling

12. Chicken Little
 Aquifers are
progressing from
confined to
unconfined;
 Edges of the Denver
Basin are considered
more vulnerable to
water level declines;
 Increased demand
(Moore et
due to population al., 2007)
growth:

13. Pump it Dry
1200
1000
800
600
400
200
0
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

14. Data Considerations
 Quality of Water Level
Data depends on:
 Method;
 Measurement
timing/interval;
 Probe calibration;
 Time since
rehabilitation.

15. Data Collection Methods
 Airline;
 Pressure Transducer;
 Datalogger;
 Supervisory Control and
Data Acquisition
(SCADA).

16. Timing of Measurement
 Infrequent data –
incorrect
assumptions;
 Favorite day
approach;
 Once a year
whether we need it
or not;
 Twice a day.

17. Timing of Measurement
Minute Readings
0
Pressure Transducer, Datalogger,
50
1-minute recording interval
100
150
Depth to Water (ft)
200
250
300
350 Monthly Readings
400
4800
450
11/2 11/7 11/12 11/17 11/22 11/27 4700
Date
4600
Top of the Arapahoe
4500
Water Elevation (ft.)
Current Pump Setting
4400
4300
4200
Airline, No Datalogger, 4100
Bottom of Screened Interval
Monthly recording interval 4000
Date

18. Probe Calibration
 Reference elevation;
 Cannot assume that probe sits at bottom of
monitoring tube;
 Calibrate depth setting with physical static
water level;
 Conduct diagnostics when equipment is at the
surface.

19. Time Since Rehabilitation

20. Time Since Rehabilitation
Dually Completed Arapahoe Aquifer Water Levels, 2002 to 2009
900 250
Top of Arapahoe
1000
200
Depth below surface (ft.)
1100
Pumping rate (gpm)
150
1200
100
1300 Depth to Water
Pumping rate
Bottom of Arapahoe
50
1400
Well Rehabilitation
1500 0
5/1/2002 5/1/2003 5/1/2004 5/1/2005 5/1/2006 5/1/2007 5/1/2008 5/1/2009

21. Data Which Do Not Support the
“Water Levels Are Falling”

22. Water Levels From the Edge

23. Small Town near Eastern Edge
Small Town Water Levels
Arapahoe Aquifer, April 2008 to November 2009
0 70
Water level
Flow rate
60
200
50
400
Depth from surface (ft.)
Flow rate (gpm)
40
Top of Arapahoe
600
30
800
20
1000
Bottom of Arapahoe 10
1200 0
Apr-08 Jun-08 Aug-08 Oct-08 Dec-08 Feb-09 Apr-09 Jun-09 Aug-09 Oct-09

24. Small Town near Eastern Edge
Small Town Water Levels
Laramie-Fox Hills Aquifer, 2000 to November 2009
0 120
Water level
200
Flow rate
100
400
600 80
Depth from surface (ft.)
Flow rate (gpm)
800
60
1000
1200 40
Top of Laramie-Fox HIlls
1400
20
1600 Bottom of Laramie-Fox Hills
1800 0
Nov-00 Nov-01 Nov-02 Nov-03 Nov-04 Nov-05 Nov-06 Nov-07 Nov-08 Nov-09

25. Water Levels From the Edge

26. Sedalia Water and Sanitation
District
Sedalia Water and Sanitation District
Arapahoe Well A-1 Water Levels, 2000 to Present
5100
Top of Arapahoe
5000
Elevation (feet)
4900
4800
4700
Bottom of Arapahoe
4600
May-00 Feb-01 Nov-01 Aug-02 May-03 Feb-04 Nov-04 Aug-05 May-06 Mar-07 Dec-07 Sep-08 Jun-09 Mar-10

27. Private Development, Western
Edge
Private Development, Western Edge
Arapahoe Well A-1, 2006 vs. 2010
5000
Top of Arapahoe
4900
Water Level has risen 1 ft over 4 years
4800
Elevation (feet)
4700
4600
4500
Bottom of Arapahoe
4400
Apr-06 Oct-06 Apr-07 Oct-07 Apr-08 Oct-08 Apr-09 Oct-09

28. Castle Pines
Castle Pines Metropolitan District
Well A-12 Water Levels from 2002 through February 2010
5000 900
4900 800
Top of Arapahoe
4800 700
4700 600
Water elevation (ft.)
Flow rate (gpm)
4600 500
4500 400
Water elevation
4400 300
Flow rate
4300 200
Bottom of Arapahoe
4200 100
4100 0
Jun-02 Jun-03 Jun-04 Jun-05 Jun-06 Jun-07 Jun-08 Jun-09

29. Conclusions and
Recommendations
 Using data which are not
reflective of a true static
water level leads to
incorrect conclusions:
 Use Judgment
 Collection of data in the
Denver Basin takes
time, patience and
networking
 Data are not linear

30. Conclusions and
Recommendations
 We need to be good
stewards of the
resource
 There needs to be one
agency for compiling
and disseminating
water level data.
 Well permits need to
require that data are
recorded and submitted
to the agency.