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Hydrologic Investigations of Deep Ground-Water Flow in the Chihuahuan Desert, Texas. Digital Download

RI0205D

Hydrologic Investigations of Deep Ground-Water Flow in the Chihuahuan Desert, Texas, by W. F. Mullican III and R. K. Senger. 60 p., 28 figs., 4 tables, 1992. doi.org/10.23867/RI0205D. Digital Version.

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RI0205D. Hydrologic Investigations of Deep Ground-Water Flow in the Chihuahuan Desert, Texas, by W. F. Mullican III and R. K. Senger. 60 p., 28 figs., 4 tables, 1992. doi.org/10.23867/RI0205D. Downloadable PDF.


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ABSTRACT
Regional and local hydrologic investigations were conducted in Trans-Pecos Texas as part of a study to evaluate potential sites for a low-level radioactive waste repository. The area is approximately 40 mi (65 km) southeast of El Paso in the Hueco Bolson, a fault-bounded desert basin that developed in the late Tertiary. Ground water in the principal study area is found in Hueco Bolson silts and sands at depths of 361 ft (110 m) and 478 ft (146 m), and at depths of 592 ft (180 m) in Cretaceous limestones. The unsaturated zone consists of approximately 50 ft (15 m) of alluvial silt, sand, and gravel underlain by 300 to 500 ft (91 to 152 m) of lacustrine and fluvial clay, silt, and fine sand. The scope of this investigation included (1) evaluating groundwater resources in the area, (2) determining ground-water flow paths and velocities, and (3) testing hydrologic hypotheses using ground-water flow models.


Development of ground-water resources in the vicinity of the principal study area is limited by (1) costs of drilling and completing wells and of producing water at depths typically greater than 400 ft (122 m) and (2) extremely low aquifer productivity. Transmissivities of aquifers in bolson and Cretaceous strata, as revealed by 12 aquifer tests, range from approximately 0.19 to 290.0 ft2/d (0.018 to 26.9 m2/d); corresponding permeabilities range from 0.0015 to 2.82 ft/d (0.0005 to 0.861 m/d). A composite potentiometric surface based on water levels measured in available wells, assuming hydrologic interconnection of the Diablo Plateau aquifer, Hueco Bolson silt and sand aquifer, and Rio Grande alluvium aquifer, indicates that ground water is recharged on the Diablo Plateau and flows to the south and southwest toward the Rio Grande beneath the bolson pediment. Little, if any, groundwater recharge occurs through the bolson surficial sediments, because of a high degree of precipitation runoff and extremely high evapotranspiration rates. A planar ground-water flow model was constructed to investigate the dominant controls on the regional flow pattern. The inferred distribution of permeability zones focuses flow from the Diablo Plateau in the eastern part of the study area toward Cretaceous outcrops in the footwall of the Campo Grande fault, creating a ridge in the potentiometric surface. The relatively low hydraulic heads reflected in the valley in the potentiometric surface near the principal study area are caused by preferential drainage along relatively permeable bolson deposits to the west and southwest toward the Rio Grande. Water-chemistry data, particularly data on tritium, carbon-14, and total dissolved solids, generally support the interpreted flow pattern; some discrepancies can be related to paleohydrologic effects associated with the incision of the Rio Grande during Quaternary time.

 

Keywords: aquifer characteristics, aquifer test, Chihuahuan Desert, ground water, ground-water resources, Hueco Bolson, paleohydrology, Texas, Diablo Plateau

CONTENTS

Abstract

Introduction
Hydrogeologic Setting

Previous Regional Hydrologic Investigations

Methods

Aquifer Test Results
     Well 22 Aquifer Tests

     Wells 72 and 73 Aquifer Tests
     Well 91 Aquifer Test

     Well 94 Aquifer Test

     Well 98 Aquifer Tests
     Aquifer Test 6
     Aquifer Test 7

     Well 99 Aquifer Test
     Well 107 Aquifer Test

     Well 126 Aquifer Test
Summary of Hydraulic Properties
Evaluation of Ground-Water Resources, Hudspeth County

Water Water Supply
Hydraulic-Head Distribution

Modeling of Regional Ground-Water Flow

Conceptual Model of Ground-Water Flow

Boundary conditions

Delineation of permeability zones

     Diablo Plateau aquifer

     Hueco Bolson silt and sand aquifer
     Rio
Grande alluvial aquifer

     Additional permeability zones

Discussion of Simulation Results

Relationship between Ground-Water Flow and Water Chemistry
Implication to Paleohydrologic Conditions in the Hueco Bolson

Conclusions

Acknowledgments

References

 

FIGURES

1. Location of water wells and one spring within the regional hydrologic study area

2. Hydrologlc cross section A-A’ illustrating general geometry of hydrostratigraphic units relationship between potentiometric surface and stratigraphy from the Diablo Plateau to the Rio Grande
3. Geologic and hydrologic units in the regional study area

4. Fluctuations in water levels of wells in study area

5. Schematic diagrams of well 22 during aquifer test and well 22* after recompletion

6. Hydrologlc plots of data from aquifer test conducted in well 22, October 5-6. 1988

7. Hydrologlc piots of data from aquifer test conducted in well 22*. October 10-13, 1989

8. Schematic diagram of wells 72 and 73 during aquifer tests conducted in November and December 1989

9. Hydrologlc plots of data from aquifer test conducted in well 73, November 26 to December 18, 1989

10. Discharge rates for aquifer test conducted in well 73, April 11 to May10, 1990

11. Hydrologic plots of data from aquifer test conducted in well 72, April 11 to May 10, 1990

12. Hydrologic plots of data from aquifer test conducted in well 73, April 11 to May 10, 1990

13. Hydrologlc plots of data from aquifer test conducted in well 72. October 10, 1990

14. Hydrologic plots of data from aquifer test conducted in well 91, April 28, 1989

15. Hydrologic plots of data from aquifer test conducted in well 94, October 1-3, 1989

16. Schematic diagram of well 98 during aquifer tests conducted in May and September 1989

17. Hydrologlc plots of data from aquifer test conducted in well 98, May 30-31, 1989

18. Hydrologlc plots of data from aquifer test conducted in well 98*,September 14-15, 1989

19. Hydrologtc plots of data from aquifer test conducted in well 99, November 9-12, 1988

20. Hydrologlc plots of data from aquifer test conducted in well 107, September 30, 1989

21. Schematic drawing of well 126 during slug test

22. Hydrologlc plots of data from aquifer test conducted in well 126, September 13, 1989

23. Photographs of dirt tank located west of study area taken immediately before and after rainfall event in July 1988

24. Potentiometric surface map of regional hydrologic study area

25. Distribution of total dissolved solids and tritium concentrations of water samples collected at wells in the area

26. Delineation of permeability zones in the model area that are incorporated in the planar ground-water flow model

27. Distribution of simulated hydraulic heads for simulation S-34

28. Streamlines and fluxes calculated for each element on the basis of simulation S-34

TABLES

1. Summary of pumping-test results iil bolson deposits

2a. Transmissivity results of aquifer test analyses for wells evaluated during study
2b. Permeability results of aquifer test analyses for wells evaluated during study

2c. Transmissivity and permeability results of aquifer (slug) test analyses for wells evaluated during study

2d. Dates and hydrologic conditions during aquifer tests
3. Water wells within 10 mi of principal study area

4. Transmissivities assigned to permeability zones in the model


Citation
Mullican, W. F., III, and Senger, R. K., 1992, Hydrologic Investigations of Deep Ground-Water Flow in the Chihuahuan Desert, Texas: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 205, 60 p.

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