Aquifer - System Compaction and Land Subsidence: Measurements, Analyses,
and Simulations - the Holly Site, Edwards Air Force Base, Antelope Valley,
California
By Michelle Sneed and D.L. Galloway
U.S. Geological Survey
Water Resources Investigations report 00-4015
Prepared in cooperation with the U.S. Department of the Air Force
Sacramento, California 2000
- Abstract
- Introduction
- Purpose and Scope
- Location
- Development of the Ground-Water Resource and Resulting Land Subsidence
- Previous Studies
- Hydrogeologic Setting
- Geologic Framework
- Aquifer Systems
- Ground-Water Levels
- Aquifer-System Compaction
- Analytical Approach
- Principle of Effective Stress
- Preconsolidation Stress
- Elastic and Inelastic Compressibility (Specific Storage)
- Aquifer-System Storage Coefficients
- Theory of Hydrodynamic Consolidation
- Parameter Range Estimates
- Vertical Hydraulic Conductivity
- Preconsolidation Stress
- Elastic and Inelastic Storage Coefficients (Specific Storage)
- Holly Model
- Formulation of Numerical Model
- Spatial and Temporal Discretization
- Boundary Conditions
- Initial Conditions
- Convergence Criteria and Mass Balance Criteria
- Assumptions and Limitations
- Simulations
- History Matching
- Sensitivity Analysis
- Analyses
- Simulated Compaction
- Future Compaction Scenarios
- Summary
- References Cited
FIGURES
- 1-4. Maps showing:
- 1. Location of Antelope Valley and the Holly site (8N/10W-1Q)
- 2. General surficial geology and location of ground-water subbasins and geologic section, Antelope Valley,
California
- 3. Location of selected well fields, observation wells, and bench marks near the Holly site (8N/10W-1Q)
in the south-central part of Edwards Air Force Base, Antelope Valley, California
- 4. Ground-water levels in the Lancaster subbasin, Antelope Valley, California, 1915
- 5. Lithologic and geophysical logs of the Holly site (8N/10W-1Q), Edwards Air Force Base,
Antelope Valley, California
- 6. Generalized geologic section showing relation of lacustrine
deposits to younger and older alluvium and aquifers in the Lancaster
and North Muroc subbasins, Edwards Air Force Base, Antelope Valley, California
- 7. Conceptual model of the aquifer systems at the Holly site (8N/10W-1Q) including the piezometers and the
borehole extensometer, Edwards Air Force Base, Antelope Valley, California
- 8. Map showing change in ground-water levels in the Lancaster subbasin, Antelope Valley, California, 1915-91
- 9. Map showing water-level surface of the confined aquifer system, spring 1992, location of selected wells, and
hydrographs of wells 8N/10W-28B1 (1951-97) and 9N/10W-24C1 (1952-99), Edwards Air Force Base,
Antelope Valley, California
- 10. Graphs showing water levels in piezometers HO-1, HO-2, HO-3, and HO-4 at the Holly site (8N/10W-1Q),
Edwards Air Force Base, Antelope Valley, California, 1990-97
- 11. Graphs showing water-level fluctuations in piezometers HO-1 and HO-3 at the Holly site (8N/10W-1Q),
Edwards Air Force Base, Antelope Valley, California
- 12. Map showing area of flowing wells, land subsidence, and two fissures in Antelope Valley, California, for
the period about 1930-92, and graphs showing ground-water levels in wells 7N/10W-05E1 and 7N/12W-15F1 and subsidence at bench marks 1171A and 474
- 13. Schematic diagram showing the borehole extensometer at the Holly site (8N/10W-1Q), Edwards Air
Force Base, Antelope Valley, California
- 14. Graph showing aquifer-system compaction and water levels measured at the Holly site (8N/10W-1Q),
Edwards Air Force Base, Antelope Valley, California
- 15. Diagram showing principle of effective stress, as applied to land subsidence
- 16-19. Graphs showing:
- 16. Compression of highly compressible clay and sand samples
- 17. Change in land-surface elevation for various time intervals for selected bench marks, and estimated
water levels (1908-97) for the middle aquifer near the Holly site (8N/10W-1Q), Edwards Air Force Base,
Antelope Valley, California
- 18. Combined water levels for piezometers HO-2 and HO-3 and cumulative vertical compaction at the
Holly extensometer, and applied stress and compaction at the Holly site (8N/10W-1Q), Edwards Air
Force Base, Antelope Valley, California, 1990-97
- 19. Sample time series used in stress/strain analyses of the Holly site (8N/10W-1Q), Edwards Air Force Base,
Antelope Valley, California
- 20. Diagram showing relation of model domain to the conceptual model and short normal resistivity log of the
Holly site (8N/10W-1Q), Edwards Air Force Base, Antelope Valley, California
- 21-31 Graphs showing:
- 21. Measured or estimated depth to water for piezometers HO-1, HO-2 and HO-3 (combined), and
HO-4 used in the 1990-97 model simulation of the Holly site (8N/10W-1Q), Edwards Air Force
Base, Antelope Valley, California
- 22. Water levels used for input in the historical model for the upper, middle, and lower aquifers at the
Holly site (8N/10W-1Q), Edwards Air Force Base, Antelope Valley, California
- 23. Simulated compaction and measured or estimated land subsidence at bench marks P1155 and LS42
near the Holly site (8N/10W-1Q), Edwards Air Force Base, Antelope Valley, California, 1908-97
- 24. History matches for 1990-97 for simulated and measured compaction and error and simulated and
measured displacement-stress trajectories for the Holly site (8N/10W-1Q), Edwards Air Force Base,
Antelope Valley, California
- 25. Distribution of error computed between measured and simulated compaction for 35 selected values
of K'v and S'skv of the aquitards at the Holly site (8N/10W-1Q), Edwards Air Force Base, Antelope
Valley, California
- 26. Simulated compaction by aquifer-system component, 1908-97, at the Holly site (8N/10W-1Q),
Edwards Air Force Base, Antelope Valley, California
- 27. Simulated deformation by aquifer-system component, 1990-97, at the Holly site (8N/10W-1Q),
Edwards Air Force Base, Antelope Valley, California
- 28. Hydraulic-head profiles of the Holly site (8N/10W-1Q), Edwards Air Force Base, Antelope Valley,
California, for 1908-97 and 1990-97
- 29. Future scenario--1996 pumping rates for 1997 to 2026 at the Holly site (8N/10W-1Q), Edwards Air
Force Base, Antelope Valley, California
- 30. Future scenario--1997 aquifer water levels held constant through year 2096 at the Holly site
(8N/10W-1Q), Edwards Air Force Base, Antelope Valley, California
- 31. Future scenario--no pumping for 1997 to 2096 at the Holly site (8N/10W-1Q), Edwards Air Force
Base, Antelope Valley, California
TABLES
1. Measured or estimated land-surface-elevation changes for selected bench
marks at Edwards Air Force Base, Antelope Valley, California
2. Summary of skeletal storage coefficients and equivalent skeletal specific
storages estimated from the results of the stress/strain analyses of the Holly
site (8N/10W-1Q), Edwards Air Force Base,Antelope Valley, California
3. Values of hydraulic parameters derived from the best history matches
between simulated aquifer-system compaction and measured or estimated compaction
at the Holly site (8N/10W-1Q), Edwards Air Force Base, Antelope Valley,
California
Abstract
Land subsidence resulting from ground-water-level declines has long been
recognized as a problem in Antelope Valley, California. At Edwards Air Force
Base (EAFB), ground-water extractions have caused more than 150 feet of
water-level decline, resulting in nearly 4 feet of subsidence. Differential land
subsidence has caused sinklike depressions and earth fissures and has
accelerated erosion of the playa lakebed surface of Rogers Lake at EAFB,
adversely affecting the runways on the lakebed which are used for landing
aircraft such as the space shuttles. Since 1990, about 0.4 foot of
aquifer-system compaction has been measured at a deep (840 feet) borehole
extensometer (Holly site) at EAFB. More than 7 years of paired
ground-water-level and aquifer-system compaction measurements made at the Holly
site were analyzed for this study. Annually, seasonal water-level fluctuations
correspond to steplike variations in aquifer-system compaction; summer
water-level drawdowns are associated with larger rates of compaction, and winter
water-level recoveries are associated with smaller rates of compaction. The
absence of aquifer-system expansion during recovery is consistent with the
delayed drainage and resultant delayed, or residual, compaction of thick
aquitards.
A numerical one-dimensional MODFLOW model of aquitard drainage was
used to refine estimates of aquifer-system hydraulic parameters that control
compaction and to predict potential future compaction at the Holly site. The
analyses and simulations of aquifer-system compaction are based on established
theories of aquitard drainage. Historical ground-water-level and land-subsidence
data collected near the Holly site were used to constrain simulations of
aquifer-system compaction and land subsidence at the site for the period
1908Ð90, and ground-water-level and aquifer- system compaction measurements
collected at the Holly site were used to constrain the model for the period
1990Ð97.
Model results indicate that two thick aqui- tards, which total 129 feet
or about half the aggregate thickness of all the aquitards penetrated by the
Holly boreholes, account for most (greater than 99 percent) of the compaction
measured at the Holly site during the period 1990Ð97. The results of three
scenarios of future water-level changes indicate that these two thick aquitards
account for most of the future compaction. The results also indicate that if
water levels decline to about 30 feet below the 1997 water levels an additional
1.7 feet of compaction may occur during the next 30 years. If water levels
remain at 1997 levels, the model predicts that only 0.8 foot of compaction may
occur during the same period, and even if water levels recover to about 30 feet
above 1997 water levels, another 0.5 foot of compaction may occur in the next 30
years. In addition, only a portion of the compaction that ultimately will occur
likely will occur within the next 30 years; therefore, the residual compaction
and associated land subsidence attributed to slowly equilibrating aquitards is
important to consider in the long-term management of land and water resources at
EAFB.
Water Resources of California
URL:http://ca.water.usgs.gov/rep/wrir004015/
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