ER-4536

CONCEPTUALIZATION AND CHARACTERIZATION OF THE HYDROLOGIC SYSTEM IN THE CARLSBAD CAVERNS NATIONAL PARK REGION/ NEW MEXICO

b y

Richard S. Tallman

ARTHUR LAKES LIBRARY COLORADO SCHOOL O f MINES GOLDEN, CO 80401 ProQuest Number: 10781230

All rights reserved

INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted.

In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest

ProQuest 10781230

Published by ProQuest LLC(2018). Copyright of the Dissertation is held by the Author.

All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC.

ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 ER-4536

A thesis submitted to the Faculty and Board of Trustees of the- Colorado School of Mines in partial fulfillment of the requirements for the degree of Master of Engineering

(Geological Engineer).

Golden, Colorado

Date K m M. /6. m

Signed: Richard S. Tallman

Approved: enneth E. Kolm Thesis Advisor

Golden, Colorado

Date

-— Roger Slatt Professor and Head Department of Geology and Geological Engineering

ii ER-4536

ABSTRACT

This report describes the hydrologic system of the

Carlsbad Caverns National Park (CCNP) Region, New Mexico.

Recent pressure to drill oil and natural gas wells in the vicinity of the CCNP has prompted a need to better understand and predict the hydrology of the area, in order to help assess potential environmental impacts.

Results of this study include a regional numerical model, estimated ranges and distributions of hydrologic parameters, and the identification of local hydrologic control mechanisms in the Guadalupe Ridge area. A regional hydrologic model delineates the area as a closed basin; bounded to the south, west and north by ground-water divides, and to the east by the Pecos River. The general direction of ground-water flow is shown to be towards the northeast; from regional recharge high in the Guadalupe

Mountains to regional discharge along the Pecos River.

Modeling efforts result in estimated ranges of the hydrologic parameters. Precipitation is shown to range from

25 inches per year in the Guadalupe Mountains to 13 inches per year in the Pecos River Valley. Recharge is estimated to average about ten percent of precipitation. Fracture

iii ER-453 6

orientations define two transmissivity tensors of N75-90°E and NO—15°W. Hydraulic conductivity values range from 1 to

5 00 feet per day, and are shown to increase towards the discharge zone.

Locally significant structural and topographic controls are identified in the immediate area of CCNP. These control mechanisms include fracturing and folding associated with the Capitan Reef Complex.

iv ER-4536

TABLE OP CONTENTS

Page ABSTRACT ...... iii

LIST OF FIGURES ...... vii

LIST OF TABLES ...... X

ACKNOWLEDGEMENTS ...... xi

Chapter 1. INTRODUCTION ...... 1

1.1 Purpose and Objectives ...... 1 1.2 Location and Geography ...... 2 1.3 Previous Work ...... 2 1.4 General Approach ...... 9

1.4.1 Data Gathering and Preparation ...... 10 1.4.2 Conceptualization and Characterization . . . 10 1.4.3 Hydrogeologic Model Development ...... 13 1.4.4 Hydrologic System Model Development.... 14 1.4.5 Numerical Modeling ...... 15

Chapter 2. SURFACE CHARACTERIZATION ...... 17

2 .1 Topography...... 17 2.2 G e o m o r p h o l o g y ...... 2 0 2.3 C l i m a t e ...... 24 2.4 Surface W a t e r ...... 25 2.5 V e g e t a t i o n...... 30

Chapter 3. HYDROGEOLOGIC FRAMEWORK ...... 33

3.1 Geologic History Since the Pennsylvanian .... 33 3.2 Stratigraphy...... 34

3.2.1 Delaware Basin Sediments ...... 41 3.2.2 The Shelf Aquifer ...... 42 3.2.3 The Capitan Aquifer ...... 43

3.3 S t r u c t u r e ...... 44

3.3.1 Folding Along Guadalupe Ridge ...... 45 3.3.2 Fractures Along Guadalupe Ridge ...... 5 0

v ER-4536

3.3.3 Regional Drainage Basin Divides ...... 57

Chapter 4. THE HYDROLOGIC SYSTEM ...... 59

4.1 Hydrologic D a t a ...... 59 4.2 Perched Aquifers ...... 61 4.3 Guadalupe R i d g e ...... 63 4.4 The Regional System ...... 64

4.4.1 Boundary Conditions ...... 64 4.4.2 Recharge ...... 65 4.4.3 Ground water Flow ...... 66 4.4.4 Discharge ...... 73

Chapter 5. NUMERICAL MODEL OF THE REGIONAL HYDROLOGIC SYSTEM ...... 74

5.1 Model Application ...... 74

5.1.1 Introduction ...... 74 5.1.2 Geometry and Grid Orientation ...... 76 5.1.3 Boundary Conditions ...... 7 6 5.1.4 Input Parameters ...... 83

5.2 Steady State Model Results ...... 89

5.2.1 Variable Head Nodes ...... 91 5.2.2 Constant Head Nodes and Mass Balance . . . .96

5.3 Sensitivity Analysis of Recharge and Hydraulic Conductivity ...... 98

Chapter 6. SIGNIFICANT RESULTS AND RECOMMENDATIONS . . 100

6.1 Summary of Significant Results ...... 100 6.2 Recommendations for Future Wo r k ...... 103

REFERENCES CITED ...... 105

SELECTED BIBLIOGRAPHY ...... 108

APPENDIX A: WELL DATABASE ...... 112

APPENDIX B: MODEL INPUT AND OUTPUT FILES 12 0

vi ER-4536

LIST OF FIGURES

1. Study area location...... 3

2. Study area boundaries and extent...... 4

3. Four primary aquifers in the region...... 7

4. Generalized cross section showing relative permeabilities...... 8

5. study approach showing specific applications to this study...... 11

6. Generalized topographic map ...... 18

7. Topographic and geomorphic features of the study area...... 21

8. Drainage patterns; derived from drainage overlay, 1:100,000...... 23

9. Contour of estimated annual precipitation, in inches per year...... 2 6

10. Distribution of springs and seeps in the study area. 2 7

11. Conceptual perched water table surfaces with topographic profiles of the bottom of: a) Dark Canyon, and b) Rocky Arroyo ...... 2 9

12. General distribution of vegetation in the study area. 32

13. Cross section looking east, along reef escarpment, showing associated structure 3 6

14. Stratigraphic column showing correlation of Permian formations...... 37

15. Generalized geologic map of the study area...... 38

16. Hydrostratigraphic column of Permian units...... 39

vii ER-4536

17. Cross section looking north, showing Huapache monocline and associated structure...... 46

18. Block diagram showing the relationship of structural controls to the distribution of caves and springs on Guadalupe Ridge...... 47

19. Lineaments of surface drainage segments in the Serpentine Bends Quadrangle...... 51

20. Rose diagram of drainage segment lineaments in the Serpentine Bends Quadrangle...... 52

21. Rose diagram of linear passages in Carlsbad Cavern. . 54

22. Comparison of plan-view outlines of: a) Carlsbad Cavern, b) Rattlesnake Canyon and c) Slaughter Canyon...... 55

23. Primary drainage basin divides...... 58

24. Schematic diagram of the regional hydrologic system. 60

25. Potentiometric surfaces of the perched aquifers in the shelf units...... 62

26. Conceptual contour map of the regional potentiometric surface in the Shelf Aquifer...... 67

27. Conceptual contour map of the regional potentiometric surface in the Capitan Aquifer...... 68

28. Cross section showing the mixing of waters in the regional discharge zone near Carlsbad, New Mexico ...... 71

29. Contour of the bottom of layer 1 ...... 77

30. Contour of the bottom of layer 2 ...... 78

31. Cross section of the numerical model looking northeast, along reef axis...... 79

32. Boundary conditions for layer 1 ...... 80

33. Boundary conditions for layer 2 ...... 81

viii ER-4536

34. Recharge array, in inches per year...... 85

35. Hydraulic conductivity array for layer 1 ...... 87

36. Hydraulic conductivity array for layer 2 ...... 88

37. Contour of heads in layer 1 ...... 92

38. Contour of heads in layer 2 ...... 93

39. Relationship of elevations of lost circulation zones to numerically derived heads...... 95

40. Cumulative gain to Pecos River from Capitan Aquifer...... 97

ix ER-4536

LIST OF TABLES

1. Primary data base used in this study...... 12

2. Attributes of the four major habitat types found in the study area...... 31

3. Estimated aquifer parameters ...... 40

4. Cave data ...... 49

5. System budget of numerical model ...... 90

6. Comparison of measured head values in wells to numerically predicted heads ...... 94

x ER-4536

ACKNOWLEDGEMENTS

I would like to express my appreciation to my thesis committee: Dr. Keenan Lee, Dr. Richard Harlan and Dr.

Kenneth Kolm. This report is, in large measure, the result of their insight, understanding and support. I would also like to acknowledge the support and assistance of my co­ workers at SRTI in Denver. By covering many of my responsibilities in the office and the field, they allowed me the time required to complete this report.

Most importantly, I would like to thank my family, LuAnn and Emily, for putting up with me and lending purpose to my work.

xi ER-4536 1

Chapter 1

INTRODUCTION

The Bureau of Land Management (BLM) has prepared a draft

Environmental Impact Statement (BLM, 1992) regarding the impacts from reasonable foreseeable development of oil and gas resources within Dark Canyon in Eddy County, New Mexico.

Major resources that may be impacted include Lechuguilla

Cave, Carlsbad Cavern National Park (CCNP), and the Capitan

Aquifer, which supplies water to the town of Carlsbad, New

Mexico (BLM, 1992). To fully evaluate the environmental impact of such developments, the hydrologic system of the area must be understood.

1.1 Purpose and Objectives

The purpose of this investigation is to develop a better understanding of the hydrogeology in the CCNP region.

The study evaluates the hydrogeology of the area using an approach outlined by Kolm (1993).

Study objectives include the development of primary and interpretive data bases, conceptualization and characterization of the hydrogeologic framework, formation of a hydrologic system model, and the development of a ER-4536 2

numerical flow model. Conclusions are drawn by comparing these results to existing conceptual models.

1.2 Location and Geography

CCNP is located in Eddy County, of southeastern New

Mexico (Figure 1). The study area, which includes CCNP, ranges from the crest of the Guadalupe Mountains in the west to Carlsbad, New Mexico and the Pecos River Valley in the east, and from the Seven Rivers Embayment in the north to the Black River and the Delaware Basin in the south (Figure

2). Main areas of anthropogenic activity in the study area include the towns of Carlsbad and Whites City, and the CCNP cavern entrance. Unimproved dirt roads allow access along the floors and rims of many canyons in the area.

1.3 Previous Work

The study area centers around part of the Capitan Reef complex, one of the best-exposed and most studied fossil reef complexes in the world. The geology of the area has been studied extensively by many geologists, including King

(1942, 1948), Newell, et. al. (1953), Hayes (1964), Kelley

(1971), Hiss (1976), and James (1985). King (1948) was the first to compile a detailed geologic map of the area. He also described the stratigraphic relationship of the rocks ER-4536 3

0 L 0 R A D O

2B3* 330

>&4< OKLA.

’6 6 6 <

84'

'85<

Gallup Santa Fe 1541

\fbuquerque 40 1&61

'60' 23 /84< N Socorro 380'

RoswelL

180'

170' Las Cruces 'so'

•f*

Figure X: Study area location (modified from BLM, 1992). Figure 2: study area boundaries (base map modified from Hayes, 1964). ER-4536 5

in the Delaware Basin to those of the Reef Zone. Newell et al. (1953) contributed detailed descriptions of the rock units in the area. Kelley (1971) and Hayes (1964) show detailed geologic structure of the Guadalupe Mountains area that includes the Huapache thrust fault zone, and a series of subparallel northeast-trending normal faults.

James (1985) provides a summary of the stratigraphy in the study area. Jagnow (1991) and the Bureau of Land

Management (1992) provide generalized cross-sections of the study area that illustrate the stratigraphic facies framework in the region. Ward, et. al. (1986) described the

Capitan reef facies and related Permian hydrocarbon accumulations.

Intensive studies have been undertaken to examine the formation of caves in the study area. These have been most recently summarized in several works by Hill (1987, 1990) and Jagnow (1989). The formation of these caves may be related to oxygenated meteoric waters that percolated through these fractures to mix with hydrogen sulfide-rich waters from depth to form sulfuric acid, which is a viable agent for cave development (Hill, 1990) .

A brief summary of water resources evaluations to date is provided by the Bureau of Land Management (1992). A general description of the water resources in Eddy County ER-4536 6

was made by Hendrickson and Jones (1952). The ground-water hydrology has been previously studied by Bjorklund and Motts

(1959), Motts (1968), and Hiss (1980).

Bjorklund and Motts (1959) published a generalized map, as part of a USGS open file report, that defines the approximate areal extent of four primary aquifers in the

Carlsbad area (see Figure 3). Aquifer boundaries were defined by changes in lithology between the basinal, reef zone and shelf (or backreef) facies. In addition, the Pecos

River Valley alluvium was defined as a separate aquifer system. This widely accepted classification scheme defines the aquifers strictly on the basis of lithology. No investigation was conducted on lineament trends or fracture orientations. Limited structural control in the vicinity of

Guadalupe Ridge was inferred, but no analysis was conducted on the distribution of caves, springs or geomorphic features. Regional fracture-flow was thought to be stratigraphically controlled from a recharge area in the

Guadalupe Mountains to a discharge area in the vicinity of

Carlsbad.

In 1968, Motts expanded the definition of the aquifers in the region based on their effective permeabilities.

Figure 4 (after Motts, 1968) is a cross section of the

Guadalupe Ridge area and Mott's interpretation of the ER-4536 7

R. 2 1 E. 2 3 2524 26 28 2927 30 R. 31 E.

EXPLANATION

Artesia □ Shelf formations

Capitan limestone (reef aquifer)

Pecos River valley alluvium

L ake Me M iHan

j j ^j^ Slack River valley alluvium 20 Lake Avalon I 2524 ~ - 28 302927 R. 31 E. R.2I E.22 23

22

23

2 4

25

26 NEW TEXAS

Figure 3: Four primary aquifers in the region (from Bjorklund and Motts, 1959). ER-4536 8

SHELF SHELF CARBONATE REEF ZONE BASIN EVAPORITE FACIES FACIES FACIES FACIES

PREDOMINANTLY PREDOMINANTLY PREDOMINANTLY •* ------EVAPORITES--- ► DOLOMITE--- ■>-«— PREDOMINANTLY LIMESTONE SANDSTONE -- m y x v w x v ^ \ \ \ \ \ ^ ~ r sotx x x x >cx x x x > r x — y “ r r y r a x x kvx k y x T T H " r —v ■ v - y - y ^ r 1 ' ■ r ^ y x x 'xx'^'3t^r“r i'~ KXXXXXXXXXXX^ \ K \ ' T SANDSTONES INTERBEDDED WITH CARBONATES AND EVAPORITES GENERALLY GENERALLY LOW EXTREMELYHIGHEXTREMELYLOW MODERATE PERMEABILITY PERMEABILITY — - 'Permeability

PERMEABILITY UMESTONE AQUIFER i------SHELF 'AQUIFERS

Figure 4: Generalized cross section showing relative permeabilities (from Motts, 1968). ER-4536 9

relative permeabilities of different lithologic zones.

There were no ranges of quantitative values assigned to the different units. Ground-water flow was still considered

controlled by lithology, but by recognizing the existence of a high permeability zone in the carbonate shelf units, Motts had refined the earlier conceptual model.

Hiss (1980) again redefined the Capitan Aquifer on the basis of lithology and similar permeabilities. This

included the Goat Seep Limestone, as well as a highly fractured high permeability zone in the gradational portion of the Shelf Aquifer that abuts the reef. Again, flow was said to be controlled by fractures which were controlled by lithology.

This report demonstrates the effect of structure and topography on the hydrologic system in addition to lithologic controls. Also, estimated ranges of hydrologic parameters are' developed where only qualitative observations have been made in the past.

1.4 General Approach

Conceptualization and characterization of the CCNP region is accomplished by using methods detailed by Kolm

(1993). As it applies to this report, this approach is based on intensive studies of the region's geology, ER-4536 10

geomorphology, hydrology and vegetation. Distributed data from these natural systems are used to augment limited point-source well data for the area. Using this approach, available point-source data are combined with distributed data in a final model (Figure 5).

1.4.1 Data Gathering and Preparation. Data of all scales are gathered in various formats including maps, aerial photography, tables and charts. An extensive literature search is conducted, and the data organized into a primary data base (table 1). Drainage trace and lineament maps are developed, as well as maps showing the distribution of vegetation types, caves and springs. These interpretive products are then added to the data base.

1.4.2 Conceptualization and Characterization. Hydrologic system conceptual model development is defined as "the procedures that will result in the general notion or idea of the hydrologic elements, active hydrologic processes, and the interlinkages and hierarchy of elements and processes"

(Kolm, 1993). The resulting preliminary conceptual model includes a qualitative assessment of how water enters, moves through, and leaves the hydrologic system. The potentiometric surfaces of each aquifer in the hydrologic ER-4536 11

Conceptualization & Characterization of Hydrologic Systems

Data Gathering and Preparation-*

Primary Data Base

Field (On-site) Conceptualization-*

Hydrologic System Conceptual Model

Surface and Subsurface Characterization-*

Subsurface Geologic Framework Model

Hydrogeologic Characterization-*

Hydrogeologic Model

Hydrologic System Characterization-*

Hydrologic System Model

Numerical Model Selection, Design, Simulation-*

Numerical Model of Hydrologic System

Figure 5s Study approach showing specific applications to this study (after Kolm, 1993). ER-4536 12

Table is Primary data base used in this study (modified from Kolm, 1993).

Geology and Geomorphology

(a) Geologic maps and stratigraphic columns (b) Surficial geologic map (c) Geologic cross sections (d) Lithologic descriptions and drillers' logs (e) Topographic maps (f) Drainage trace map (g) Aerial photos (h) Cave data.

Hydrology

(a) Water well data; ground-water elevations and hardness (b) Potentiometric surface maps by other investigators (c) Data on springs and seeps (d) Surface-water data (e) Qualitative descriptions of aquifer properties.

Vegetation

(a) Description of vegetation communities (b) Description of general distribution.

Climate

(a) Precipitation Data.

Hydrology

(a) Well data (b) Zones of lost circulation. ER-4536 13

system are also conceptualized at this time. This

conceptual model is used for characterization and the

application of analytical mathematical models.

An interpretive data base is developed through surface and subsurface characterization. Geomorphologic analysis, drainage pattern analysis and vegetation maps are developed as part of the surface analysis. Subsurface geologic

framework conceptualization is conducted using geologic maps, structural data, fault zones and lineament maps, geologic cross sections and drill logs. These data are combined to form an initial hydrologic characterization.

1.4.3 Hvdroqeoloqic Model Development. Surface and subsurface characterization of the area is conducted and the results are applied to the existing conceptual model.

Hydrogeologic unit thicknesses, hydrogeologic properties of the units, structural discontinuities, and geologic and topographic continuity of the framework are all included in the resulting hydrogeologic model (Kolm, 1993; Anderson and

Woessner, 1991).

Hydrostratigraphic units are characterized using geologic maps, stratigraphic columns, hydrologic data, and parameter estimation techniques. Effective permeability, values are assigned to bedrock units based on aquifer tests, ER-4536 14

field observations, or parameter estimates found in existing literature. These hydrostratigraphic units are then reclassified as aquifers or confining units on the basis of their hydraulic properties.

Hydrostructural units are characterized using a fault and fracture zone map, cave maps, spring and vegetation distribution, and hydrologic data. The distribution of structural and geomorphic (karst) discontinuities, including type, distribution and thickness, has been determined during surface and subsurface characterization. Therefore, these units are reclassified as aquifers (conduits) or confining units (barriers) on the basis of their respective hydraulic properties. The effects of faults and fracture systems on the hydrologic system are determined using the methods of

Anna (1986), Peter and others (1988), and Kolm and Downey

(in press). These methods include gathering existing fault maps, fault mapping, structural analysis, and analyzing the surface evaluation of anomalous drainage patterns, topographic alignments, and linear vegetation patterns.

1.4.4 Hvdrologic System Model Development. A hydrologic system model is developed using the primary and interpreted data bases, the conceptual model, and the hydrogeologic model. This procedure integrates all of these products to ER-4536 15

determine the: l) type and distribution of recharge; 2)

type and distribution of discharge; 3) flow path vectors; 4)

type and distribution of boundary conditions; and 5) potentiometric surfaces.

A spatial analysis of map data is conducted to

determine type and distribution of recharge. The CCNP/Dark

Canyon study area has multiple sources of recharge. Each of

the following sources are evaluated: 1) infiltration from precipitation, 2) infiltration from surface-water bodies, 3)

leakage from other aquifers through faults, fracture zones, karst, or confining units and 4) lateral flux through study area boundaries.

A spatial analysis of map data is also conducted to determine type and distribution of discharge. The following vertical and lateral sources are evaluated: 1) springs and seeps, 2) surface-water bodies, 3) evapotranspiration, 4) well discharge', 5) leakage to other aquifers through faults, fracture zones, karst, or confining units, and 6) lateral flux through study area boundaries.

1.4.5 Numerical Modeling. A numerical flow model is developed using MODFLOW to quantify the hydrologic system model. Input parameters are determined from the hydrogeologic and hydrologic system models, and therefore ER-453 6 16

incorporate field (on-site) conceptualization, surface and subsurface characterization, and the hydrogeologic framework model. ER-4536 17

Chapter 2

SURFACE CHARACTERIZATION

This chapter examines the topography, geomorphology, climate, surface water and vegetation in the CCNP region.

Once characterized, each of these factors will be used to help define the hydrologic system.

2.l Topography

The Guadalupe Plateau is a fluvially dissected block of moderate to high relief that dips gently to the northeast.

The Delaware Basin borders the plateau to the south, along the Capitan Reef escarpment. The plateau is bounded in the west by the Big Dog Valley, and in the east by the Pecos

River. Within the interior of the block, the Seven Rivers

Embayment forms an area of low relief in the north.

Elevation in the study area ranges from 3,100 feet on the Pecos River to 7,2 00 feet along the crest of the

Guadalupe Highlands. A generalized topographic map is shown in Figure 6. Low lying areas are typically flat, and include the Seven Rivers Embayment, the Pecos River Valley, and the Delaware Basin. The uplands, including the

Guadalupe Mountains and Guadalupe Ridge, are more dissected, and tend to support local hydrologic systems in addition to ER-4536 18

5 miles 10 Contour Interval = 500 feet N

Carlsbad!

Rocky Arroyo

Last Chance Canyon

R22E R24E R 2 6 E

Figure 6: Generalized topographic map of the study area. ER-4536 19

the regional system.

The Guadalupe Mountains play a major role in defining the regional hydrologic system. Generally, the entire regional system is driven by the topographic relief of the

Guadalupe Mountains. The gentle regional dip to the east- northeast moves water from the Guadalupe Mountains in the west to the Pecos River in the east. The western flow boundary of the system is defined by the ground-water divide along the crest of the Guadalupe Mountains. Indirectly, the mountains also affect the hydrologic system by helping to control the area's climate and vegetation.

East of the Guadalupe Mountains, the topography is generally discontinuous; dissected by canyons and arroyos.

The dissected terrain found along the reef escarpment effectively reduces recharge into the Capitan Aquifer by diverting surface runoff through canyons and into the

Delaware Basin'. North of Guadalupe Ridge and east of the mountains, a table-land topography has developed which effects the hydrologic system. The elevation gained by the

Hess Hills, Hackberry Hills and the Cueva Escarpment is great enough to drive local ground-water flow. ER-4536 20

2.2 Geomorphology

A generalized map of the area's geomorphology is given in Figure 7. The relative maturity of the geomorphology in the area decreases with the amount of topographic relief.

The prominent reef escarpment/ which marks the southern edge of Guadalupe Ridge, is formed by the resistant Capitan

Limestone. Deep canyons have cut back into the escarpment from the south, forming broad alluvial fans that extend out into the Delaware Basin. This area, along Guadalupe Ridge and the reef escarpment, represents the most dissected terrain in the study area.

North of Guadalupe Ridge, outcrops of backreef units cover the landscape. The Seven Rivers Embayment is a topographical depression caused by differential erosion of evaporites from the Queen and Seven Rivers Formations. This has left an area of low relief and moderate to poor dissection. South and east of the embayment, the Hess

Hills, Azotea Mesa and Seven River Hills remain topographically positive. These moderately dissected hills are capped by more resistant carbonate tongues of the Seven

Rivers Formation (Hayes, 19 64). South of the Hess Hills, incision of ancestral meandering drainage patterns are evident in Dark Canyon and Walnut Canyon. ER-4536 21

Seven Rivers C a rlsb a d

Hackberry ^ E m b a y m e n t Hills

P eco s E s c a rp m e n t G u a d alu p e R iver

Alluvial

V a lle y ;

M o u n ta in s

Delaware Basin

R22E R24E

Figure 7: Geomorphic features. Dark lines denote areas of high relief, cross hatching denotes well dissected areas. ER-4536 22

The Guadalupe Mountains come to an abrupt end along the

Big Dog Valley Fault scarp, which defines the western edge of the hydrologic system. The Huapache escarpment, formed by the Huapache monocline, marks the eastern edge of the mountains. These mountains are characterized as well dissected areas of high relief.

The Pecos River Valley to the east was formed in the easily eroded rocks of the Ochoa Series. The Pecos River is thought to have been formed by the interconnection of sinkholes and channels in a karst terrain (Hiss, 1976), and has since formed a broad alluvial valley. This area is characterized as having low relief and poor drainage dissection.

Figure 8 is a generalized map showing the different drainage patterns found in the area. This distribution demonstrates that patterns change dramatically with lithology and structure. The massive limestone of the

Capitan Reef is dominated by a rectangular pattern; the result of fracture-flow control within the unit. Because ground-water flow is also controlled by fractures, this surface pattern may closely mirror ground-water flow patterns. This connection between surface-water and ground­ water flow will be addressed in detail later in chapter 3.

Immediately adjacent to the reef escarpment, parallel ER-4536 23

miles

R22E R24E R26E

5 Rectangular E2 Sub-parallel

'\ Sub-rectangular Dendritic

Parallel

Figure 8: Drainage patterns; derived from drainage overlay, is 100,ooo. ER-4 53 6 24

and sub-parallel drainage patterns occur. Some of these drainages are parallel to the reef complex, and coincide with structural features. Others are normal to the escarpment, and also may be controlled by fractures.

The dendritic patterns in the Seven Rivers Embayment,

Pecos River Valley and Delaware Basin are typical of alluvial valleys and lithologic controls (Ritter, 1978).

The backreef shelf deposits display a semi-rectangular pattern. This indicates fracture control that is less developed than that of the Capitan Limestone.

2.3 Climate

The climate of the Carlsbad area is typical of the semiarid southwestern United States. The driest year on record was 192 4, when 2.95 inches of precipitation were measured in Carlsbad. The wettest year was 1941, when

Carlsbad recorded 33.94 inches. To date, 1993 appears to be a normal year for precipitation (National Resources Planning

Board, 1992; Bjorklund and Motts, 1959). Temperature extremes that have been recorded in Carlsbad range from a high of 112°F to a low of -17°F.

Two U.S. Weather Bureau observation stations are located in the area: one in Carlsbad, and one at the Cavern entrance. The Mayhill ranger station is located northwest ER-4536 25

of the study area, and the weather there is typical of the eastern slope of the Guadalupe Mountains. Data from the

Carlsbad, CCNP and Mayhill weather stations shows average annual precipitation values of about 13 inches, 16 inches and 25 inches respectively (National Resources Planning

Board, 1992; Bjorklund and Motts, 1959). The amount of precipitation varies across the study area primarily as a function of topography (Figure 9). Approximately 75 percent of the precipitation in the area is derived from afternoon thunderstorms that occur during the 210-day growing season from May to October. Flash floods in the canyons and arroyos of the study area are caused by run off from these events.

2.4 Surface Water

Given the lack of well data in areas distant from the town of Carlsbad, the distribution and stratigraphic position of springs and seeps become important hydrologic system indicators. In addition, the extent of perennially flowing rivers and streams may indicate the distribution of local and regional aquifers.

The distribution of springs in the study area is shown in Figure 10. Locations were determined by using topographic maps, aerial photographs and field observations. T25S T23S T21S iue : otu o etmtd nul rcptto, in precipitation, annual estimated of Contour 9: Figure topography. inches per year. Based on vegetation distribution and and distribution vegetation on Based year. per inches ER-4536 ObservationPoints ie 5 miles 0 26 ER-4536 27

Pecos Tansill % Spring or Seep Res. River

Perennial Reach Carlsbad Spg. ----

CD

X-Bar Ranch

R22E R 2 4 £ R265

Figure 10: Distribution of springs and seeps in the study area. ER-4536 28

The presence of riparian ecosystems was used as an indicator of springs and seeps.

Spring distribution is typically the result of local discharge from perched aquifers, and indicates structural control of ground-water flow in the CCNP area. Abundant springs and riparian vegetation surrounding Carlsbad Springs and Tansill Reservoir, both near the town of Carlsbad on the

Pecos River, represent a large area of regional discharge

(Figure 13).

In addition to this reach of the Pecos River, perennial reaches occur in two other locations in the study area (Figure 13). The first is a 3-mile reach of Dark

Canyon just above the X-Bar Ranch and Serpentine Bends. The second is located in Rocky Arroyo, west of Carlsbad. In both cases, the discharge sustaining stream flow is derived from perched aquifers. The underlying impervious layers are exposed at the' surface in these locations because the slope of the ground is greater than that of the dipping beds. In

Dark Canyon, this change in slope occurs as the canyon crosses the Huapache Monocline. In Rocky Arroyo, the change in slope is the result of a lithologic change encountered as the arroyo leaves the Seven Rivers Embayment. Figure 11 illustrates this in cross section, and shows the conceptual perched water tables superimposed on the respective ER-4536 29

a) Dark Canyon

Topography

Perched Water Table Spring

Impermeable Layer Perennial Reach

Topographic Gradient Change X-Bar Ranchi Resulting from the Huapache Monocline

b) Rocky Arroyo

Seven Rivers Embayment Topography

Perched Water Table Spring

Impermeable Layer Perennial Reach

Topographic Gradient Change resulting from a Lithologic Change

Figure 11: Conceptual perched water table surfaces with topographic profiles of the bottom of: a) Dark Canyon/ and b) Rocky Arroyo. ER-4536 30

topographic profiles of the bottom of Dark Canyon and Rocky

Arroyo-. The occurrence of perched aquifers in the study area is discussed later in chapter 4.

2.5 Vegetation

There are four major habitat types in the study area

(BLM, 1992). Table 2 is a general outline of the species, location and hydrologic significance of each of these major habitats. Their areal distribution in the study area is shown in Figure 12. Springs, seeps and surface-water bodies can be readily identified from aerial photographs on the basis of the associated dense riparian vegetation. ER-4536 31

Table 2s Attributes of the four major habitat types found in the study area (BLM,1992; Mutel and Emerick, 1992).

Pinon/Juniper Forest - Regional recharge indicator. - Found at higher elevations, along ridge tops, and in the heads of some drainages. - Dominated by pinon pine and one-seed juniper; mountain mahogany, oaks, rabbit brush and sumac are also present.

Mixed Shrub Hill - Xerophytic response indicator. - Found on side slopes and low ridge tops; transition zone between drainage bottoms and high mountain ridges. Cover most of the study area east of the Guadalupe Mountains. - Species present include acacia, yucca, sotol, lechuguilla, century plants (agave), mesguite, creosote bush, ocotillo and a variety of cacti.

Grass Flat - Potential recharge indicator. - Covers alluvial valleys and much of the Delaware Basin and Seven Rivers Embayment. - Species present include tobosa grass, salt grass, vinemesquite, and sparsely scattered yucca.

Riparian - Phreatophytes; perennial flow and ground-water discharge indicator. - Found at springs and in the bottoms of arroyos and drainages in areas of perennial surface or near-surface ground-water flow. - Commonly found are the desert willow, netleaf hackberry, big-toothed maple, oaks, and black walnut (also called the mexican or little walnut). ER-4536 32

R ip arian

G ra s s F la t C a rls b a d

M ix e d Shrub Hill

Pinon

Juniper

R ip a ria n -

Pinon Juniper 3 r F o re s t

R iparian G rass F la t

R22E R24E R25E

Figure 12: General distribution of vegetation in study area. ER-4536 33

Chapter 3

HYDROGEOLOGIC FRAMEWORK

This chapter describes the hydrogeologic framework that controls the hydrologic system. In addition to a summary of the geologic history, the stratigraphy and structure of units in the area are examined and related to the hydrologic system.

3.1 Geologic History Since the Pennsylvanian

Permian units in this area were greatly affected by the subsidence of the Delaware Basin, which probably started during the Pennsylvanian (Kelley, 1971). The basin margin became the site of lime-bank deposition and barrier-reef growth. In the backreef area to the northwest, a sequence of dolomite, limestone, siltstone and evaporites was deposited whil,e fine-grained clastic sediments were being deposited in the basin to the southeast. As the reef grew upward and basinward, deposition along the basin margin was affected by mild folding parallel to the reef front.

Toward the end of Permian time, the waters of the

Delaware Basin became supersaline, which ended reef growth.

Evaporite deposits filled the basin, and covered the shelf area along with carbonates and clastic sediments. During ER-4536 34

the Cretaceous Period, the shallow sea advanced over the

area and retreated for the last time. At the end of the

Cretaceous, the area underwent a period of broad uplifting.

The resulting elevation gain and regional dip of sediments

to the east established an ancestral drainage pattern on the

Guadalupe block, and allowed cave solution to begin (Newell

et al., 1954).

The Guadalupe Mountains were probably uplifted in the

late Pliocene or early Pleistocene (Hayes, 1964). At that time, the existing drainage system was superimposed on the uplifted block, and an extensive limestone cave system, which includes Carlsbad Cavern, was formed. The present topography is the result of continued erosion of the uplifted sedimentary rocks of the Guadalupe block.

3.2 Stratigraphy

The underlying rocks in the study area range in age from Precambrian to Early Permian. Precambrian rocks are overlain by a series of sandstones and dolomites of

Ordovician age, including the Bliss Sandstone, El Paso

Formation, and Montoya Dolomite. In turn, these units are overlain by the Fusselman Dolomite (Silurian), Percha shale

(Devonian), and a Mississippian cherty limestone.

Pennsylvanian rocks vary in thickness from zero to 4,000 ER-4536 35

feet, and are influenced by Pennsylvanian tectonic activity

(Kelley, 1971) .

Permian rocks outcropping within the study area have been separated into three distinct regional facies (Figure

13). These are (from southeast to northwest) the basinal or forereef facies, the marginal or reef zone facies, and the backreef or shelf facies (Newell et al., 1953). Each of these facies has a distinct geology and geomorphology. A stratigraphic correlation of the Permian units in the study area can be found in Figure 14; a generalized geologic map of the area is shown in Figure 15.

A hydrostratigraphic column of the Permian rocks in the area is shown in Figure 16. The saturated thickness, hydrogeological description, and an estimated range of effective hydraulic conductivity is assigned for each unit.

Table 3 outlines these parameters for the two primary aquifers in this system: the Shelf Aquifer and the Capitan

Aquifer. The two are distinguished primarily on the basis of effective conductivity. In general, the Capitan Aquifer is thought to have an effective conductivity one to two orders of magnitude greater than that of the Shelf Aquifer

(Motts, 1968). Conductivity values were determined on the basis of published general ranges and previous work (Table

3). Harlan, Kolm and Guttentag (1989) give a range of ER-4536 36

CAPITAN SHELF AQUIFERS AQUIFER NORTH SOUTH

TOP OF GUAOALUPIAN AGE ROCKS

ARTESIA GROUP . y TA N S ILL FM YATES FM * BAS S SAN AM>RES LIMESTONE AQUIFERS SEVEN RIVERS FM CAPITAN v I LIM ESTO NE^ raij- ^

8ELL CANYON GOAT SEEP FM LIMESTONE GROUP MOUNTAIN L Of AWAKE

TOPOGRAPHIC FACIES NAME ANO POSITION DOMINANT LITHOLOGY CHERRY CANYON Bernal facies (red shale, siltrfone FM BACK-SHELF and sandstone)

v I Chalk Bluff facies ( evaporates and MIO-SHELF x v ■nterbedded dolomite and tdndstone) BRUSHY CANYON FM

Carlsbad facies ( dolomite with inter NEAR SHELF-EDGE beaded siltstone and sandstone)

APPROXIMATE SCALE METERS I FEET Reef or bank facies (limestone - ipOO Adapted from several »o.':ei "c uomg SHELF-MARGIN Tait anc otners IiRbl 5 e^o Toad and dolomite) 200-1 (1969) »nc. especai'*, “ e »»->e' 1971). 200000 FEET I Basin facies (sandstone with BASIN 50000 METERS interbedded limestone)

Figure 13: Cross section looking east, along reef escarpment, showing associated structure.

ARTHUR LAKES LIBRARY COLORADO SCHOOL Of MINES GOLDEN, CO 80401 - ER-4536 37

NORTHWEST SHELF MARGINAL AREA DELAWARE BASIN 277ZZ.

ialado Formation

Castile Formation

Tansill Formation

a Yates Formation Capitan Limestone Bell Canyon Formation

Seven Rivers Formation

Queen Formation Cherry Canyon Goat Seep Dolomite cn Grayburg Formation Formation a

Sandstone tongue ^

San Andres Brushy Canyon Formation Limestone

?— Cutoff Shale

Victorio Peak

Limestone co Yeso Formation Bone Spring Limestone TO

Hueco Limestone Wolfcamp (? ) Formation

Figure 14: Stratigraphic column showing correlation of Permian Formations (from Hayes, 1964). ER-4536 38

liJ Alluvium rm Ochoa Series Evaporites i=l Capitan Formation KN Tansili Formation YA Yates Formation ff'f'r Seven Rivers Formation

Queen Formation

Grayburg Formation 5 miles 10 □ San Andres Formation

C a r sbaa

R22E R24E R26E

Figure 15: Generalized geologic map of the study area (Hayes, 1964; Motts, 1968). Newell et al, 1953; Hayes, 1964; and Kelley,1971). and 1964; Hayes, 1953; al, et Newell Figure 16s Hydrostratigraphic column of Permian units (after (after units of Permian column Hydrostratigraphic 16s Figure ER-453 ER-453 6

Capitan Aquifer Shelf Aquifers Reef Facies Backreef Facies 200 200 - feet:300 of Tongue Sandstone the Formation Cherry Canyon 0 - feet:500 Goat Seep Limestone 475 feet:475 formation Grayburg 275 275 feet: Yates formation 335 335 feet: RiversSeven Formation 360 360 feet: formation Queen 1000 1000 -feet: 1500 Capitan Limestone 125 125 feet:Tansill formation 0 - 0 0 3 feet: Alluvium Forms the Forms bottom of the regional hydrologic system. Well sorted layer;sandstone with littlecompetant fracturing perched aquifersperched with stock well s. perched aquifersperched with stock wells. Fractured Fractured aquifer with confining beds; contains Fractured Fractured aquifer with confining beds; contains sand sand stones and siltstones. sand stones and siltstones. Fractured Fractured dolomite inter with bedded a few Interbedded Interbedded dolomite/limestone with brownish Interbedded dolomite/limestone with brownish Thinly laminated dolomite/limestone. sandstone and siitstonesandstone layers. Highly permeable; covers ofand bottoms arroyos canyons Highly fractured aquif efflelds small of amounts water. Aquifer with confiningfew beds. Seven RiversSeven Embaymenl Yields ofwater good quality to domestic wells in the brownish siitstonebrownish layers;Thiniy to very littleThickly dolomitebedded interbedded with sands. Massive limestoneMassive from an formed organic reef. Relatively high effective permeability; yields water Contains a highly fractured massive member, cavernous and and a less highly fractured forereef breccia member. and and Whites City. of qualitygood in large to amounts the oftowns Carlsbad Probably Probably contains water, but not developed by wells due due to excessive depths. toMassive thickly limestone/dolomite.bedded Semi-confining detrital layers 39 ER-4536 40

Table 3: Estimated aquifer parameters.

Hydroiogic Unit Geologic Units Summary Description Saturated •Range of Thickness; Effective feet Hydraulic Conductiv­ ity; fpd

Shelf Aquifers Tansill Formation Thinly laminated dolomite/limestone; highly fractured. 0 - 125 1 to 100

Yates Formation Highly fractured dolomite/limestone with 0-275 sandstone/siitstone confining beds forming perched aquifers.

Seven Rivers Highly fractured dolomite/limestone with 0 - 335 Formation sandstone/siitstone confining beds forming perched aquifers.

Queen Formation Fractured dolomite with few detrital confining beds. 0-360

Grayburg Formation Bedded dolomite with confining layers of siitstone. 0-475

Capitan Aquifer Capitan Limestone Formed from organic reef. Massive layer is highly 0 - 1500 10 to 1000 fractured and cavernous, forereef breccia member less fractured. Provides water source for Carlsbad.

Goat Seep Limestone Thickly bedded limestone, dolomite. Probably 0-500 contains ground-water, but depth is excessive.

* Basis for vaiues: Harlan et al (1989), Freeze and Cherry (1979); aquifer tesi information in similar geologic frameworks. ER-4536 41

effective hydraulic conductivity for fractured limestone as

1 to la,000 feet per day. Previous studies in the Carlsbad area present only relative permeability values for the different aquifers (Bjorklund and Motts, 1959; Motts, 1968).

3.2.1 Delaware Basin Sediments. The units of the basinal facies are located in the low-lying Delaware Basin, and are mainly overlain with alluvium. Guadalupian Formations of the Delaware Basin make up the Delaware Mountain Group. They are, in ascending order, the Brushy Canyon, Cherry Canyon and Bell Canyon Formations. They range in thickness from about 2700 to 3500 feet (King, 1948). These formations are comprised mostly of fine grained sandstones and siltstones interbedded with carbonates. Above the Guadalupe Series is the Castile Formation of the Ochoa Series; predominantly anhydrite. Overlying the Castile is a solution breccia which represents the Salado Formation. The Rustler

Formation was then deposited as the youngest Permian formation in the area.

The basinal sediments are relatively impermeable, and so form a barrier to regional flow in the Capitan Aquifer.

The bottom of the regional hydrologic system is defined by the presence of a sandstone tongue of the Cherry Canyon

Formation that extends shelfward beneath the Capitan Aquifer ER-4536 42

and Shelf Aquifer, and grades into the upper member of the

San Andreas Limestone (Boyd, 1958). This sandstone layer was first defined by King (1948) as a persistent, competent

layer 2 00 to 3 00 feet thick that outcrops in the study area in Last Chance Canyon. At this location, Sitting Bull

Springs occurs intermittently as ground water flowing along the top of this relatively impermeable layer is forced to the surface. This demonstrates the sandstone tongue can act as a barrier to vertical flow (Bjorklund and Motts, 1959).

3.2.2 The Shelf Aquifer. The backreef or shelf facies is represented in the Guadalupe Series by the San Andres

Limestone and the Artesia Group (Figure 14). The base of the Guadalupe Series is within the San Andres Formation.

The uppermost part of the San Andres grades laterally into the Sandstone Tongue of the Cherry Canyon Formation. The

Artesia Group consists of, in ascending order, the Grayburg,

Queen, Seven Rivers, Yates and Tansill Formations (King,

1948). The top of the Tansill Formation marks the top of the Guadalupian Series.

Lithologic units of the shelf facies are thinly-bedded limestones and dolomites which are interbedded with sandstone and siitstone beds. Individual shelf formations are defined and differentiated by the number of sandstone ER-4536 43

and siitstone beds in each formation. The Queen, Grayburg and Yates Formations contain numerous sandstone layers, while the Seven Rivers and Tansill Formations contain few

(Motts, 19 68).

Shallow perched aquifers are found locally in the shelf facies, where underlying sandstone beds have formed relative barriers to vertical flow (Bjorklund and Motts, 1959). The amount of vertical flow from these shallow perched aquifers into the underlying deep regional water table is unclear.

3.2.3 The Capitan Aquifer. The reef-zone facies of the

Guadalupian reef complex consists of the Capitan and Goats

Seep Limestones. The Capitan Aquifer, principal water supply for the City of Carlsbad and Whites City, is bounded to the southeast by a relatively impermeable basinal facies.

To the northwest, it is limited by a gradational change to lower-yielding rocks of the backreef shelf facies (BLM,

1992; Hiss, 1980).

The Capitan Limestone is differentiated into two distinct subfacies: the massive subfacies and the reef-talus breccia subfacies (Newell et al., 1948). The massive member represents the organic reef mass, while the breccia member is a dolomitized forereef talus deposit consisting of detrital reef fragments and fossils. In its present ER-4536 44

position, the breccia underlies the massive core of the reef because of the continuous upward and basinward growth of the reef. The breccia member has a lower effective permeability than the massive member. In the Big Room of Carlsbad

Cavern, the spectacular flowstone and other water-induced cave decorations are abundant in the massive facies, but are virtually absent in the breccia facies. This occurrence is directly related to the volume of ground water that flows through each subfacies; the fracture system within the massive member is far more extensive than that of the breccia member.

The Capitan interfingers into the Tansill, Yates and

Seven Rivers Formations, while the Goat Seep Formation grades into the Queen and Grayburg Formations of the shelf facies (Hayes, 1964). The Goat Seep Formation is more dolomitic than the Capitan. It is probably hydraulically connected with'the Capitan and has a high effective permeability, though little is known about this formation because of its depth and a lack of penetrating wells.

3.3 Structure

The primary structural feature in the region is the

Guadalupe uplift. It dips gently to the northeast, is bounded on the west by the Big Dog Canyon graben, and on the ER-453 6 45

east by the Huapache monocline (Hayes, 19 64). The oldest known structural feature in the area is the buried

Pennsylvanian Huapache thrust fault zone (Figure 17). This fault zone trends to the northwest, and was uplifted to the southwest. The exact orientation and extent of this fault zone is unknown, although deep well borings have shown it to be a reverse fault with the southwestward block being upthrown (Hayes, 19 64). Later Permian units were draped over this fault zone, and formed the Huapache monocline during the Cenozoic uplifting of the Guadalupe Mountains

(Hayes, 1964).

3.3.1 Folding Along Guadalupe Ridcre. Other structural features in and around the Guadalupe Ridge area control flow locally, and directly affect the hydrologic system within

CCNP. Parallel to the reef escarpment, and intersecting the

Huapache monocline, is a zone of folds about 5 miles wide characterized by the Walnut Canyon syncline and the

Guadalupe Ridge anticline. Smaller folds, referred to here as the Reef anticline and the Dark Canyon syncline, flank the two larger features.

Figure 18 shows the relationship on Guadalupe Ridge between these local structural features and the distribution of springs and caves. The springs occur where a canyon, following a synclinal valley, intersects an impervious ER-4536 46

7000*. 400CT-J

^ ^ ^-■■■“ •* ' ■ ------».j — — v,— -.- —...... ■ *- —

Hu geo Limestone tPermik/n

Hueco LUneacone tPenniani

Misatsaippian in fl Ue^oman

•p-i giire 17 s cross section looking north showing the Huapache fault zone and associated structure. ER-4536 47

(Plunging Anticline and Syncline)

Spring

Arrows depict flow.

Semi-confining Detrital Layers of Sandstone and Siitstone

Carbonate Aquifers (fracture flow)

Figure 18: Block diagram showing the relationship of structural controls to the distribution of caves and springs on Guadalupe Ridge. ER-4536 48

sandstone bed along the flank of an anticlinal ridge.

Recharge that infiltrates to deeper impervious layers will

likely follow a similar path, and will be collected in the adjacent syncline.

Table 4 shows the location and geologic setting of

eleven major caves in the region. Note that only four of these are located within the Capitan Limestone, and that they are not restricted to specific lithologic units. This table shows the two basic factors that control cave formation are: 1 ) mineralogy, and 2 ) availability of oxygenated meteoric ground water. The mineralogy of the

Shelf Aquifer becomes more calcitic, and the units more cavernous, towards the basin margin (Motts, 19 68). Like the springs in the area, caves are distributed along anticlinal flanks, where infiltrating meteoric water flows along fractured carbonate layers.

Ground-water movement into and along synclinal troughs probably began with the Tertiary folding (Hayes, 1964).

Immediately adjacent and parallel to the reef escarpment, one such trough, the Walnut Canyon syncline, extends from the western edge of the Guadalupe Plateau to Whites City.

Several Canyons, to include Big, Slaughter, Rattlesnake and

Walnut, follow this synclinal valley. The regional lineament that connects these drainages is evidence of an ER-4536 49

Table 4: Cave Data (from Hayes, 19 64).

Location of entrance Maximum Name of cave Formation in which Principal joint Brief description Maximum vertical range formed directions length (feet) (feet) Sec. T.(S.) R.(E.)

Black ______29 25 22 Seven Rivera. N. 10° W.1. Three closely spaced U nknow n... Unknown parallel passages with a short connecting cross chamber,1 B urnet 1______35 22 21 San Andres N. 30° W.1. One joint-controlled 55 + 3 2 5 + 3 Limestone. passage.3 Carlsbad ______31 24 25 Entrance in Approx N. 75° Very large joint- 4,600. 1,025 Tansill; most of E. and N . controlled chambers, cave in Capitan 15° W . corridors, and narrow Limestone 4 passages on several (fig- 27). levels. Chim ney______2 25 24 Capitan Lime­ Unknown. Vertical slot ______Negligible.. 150(7) 1 stone. Cottonwood___ 6 26 22 Seven Rivers____ N. 15° W.1... Simple linear chamber 1 ,3 0 0 ± ___ 225 1 G oat ______11 25 23 Capitan Lime­ Approx N. 35° Broad elongate chamber.. 5 0 0 + ...... 100 + stone. W. H idden______29 25 22 Seven Rivers____ N. 10° W., N. Six or seven straight U nknow n.. Unknown 30° W ., N . narrow joint-controlled 80° E .1 passages.1 Lechuguilla ___ 28 24 24 Y ates ______N. 60° E., N. Chimney opening into a 215____... 100 30° W . linear chamber with short narrow side passages. Mudgetts _____ 21 24 24 Seven Rivers_____ N. 75° E.1. One straight horizontal 7 5 0 + »___ Slight chamber.1 N e w ...______23 25 23 Capitan Lime­ N. 20° W., N. Large sinuous chamber 1,150...... 250 stone. 60° E. with several long sub­ parallel side passages, some of which are interconnected. Sitting Bull___ 3 24 22 Tufa of Quater­ None. Formed by the irregular 100+ ___ Slight nary age. growth of calcareous tufa.

1 Brett (1949). i Moran’s (1955, p. 258) belief that sandstone beds found in Carlsbad Cavern 1 Not shown on plate 1. may be sholfward tongues of the Delaware Mountain Oroup is not substantiated. 1 Tloward (1935). On the basis of both lateral and vertical position they are probably toncues of the basal part of the V-tes Formation as originally suggested by T . H . Black (1954, p. 136). ER-4536 50

ancestral drainage that followed this synclinal valley

continuously; referred to here as Walnut Creek (Bjorklund and Motts, 1959).

3.3.2 Fractures Along Guadalupe Ridge. The orientation of linear surface drainage segments in the Serpentine Bends quadrangle are shown in Figure 19. The Serpentine Bends quadrangle was used for this investigation because it contained examples of every drainage pattern present in the study area. It also spans three different drainage basins, and is representative of the Guadalupe Ridge area.

Figure 20 is a rose diagram of the lineaments shown in

Figure 19. All segment lengths were plotted equally in this diagram. Two distinct lineament sets, trending N45-90°E and

N0-15°W, are approximately parallel to and normal to the reef escarpment. The orientation of these lineament sets coincides with' known fracture sets associated with the reef complex (Newell et al., 1953; Bjorklund and Motts, 1959;

Hayes, 1964), as well as the folds which parallel the reef.

This indicates that the surface drainages on Guadalupe Ridge are controlled by these structural features.

CCNP caves are generally aligned with these same northeast-trending fractures that are parallel to the fold axes of the Tertiary anticlines and synclines (BLM, 1992). ER-4536 51

Figure 19: Lineaments of surface drainage segments in the Serpentine Bends quadrangle. ER-4536 52

Reef Escarpment is oriented at approximately N50E.

Orientation of Lineaments Measured

N30W N30E N46E N46W

N60E N60W

N75W N75E

N90W N90E

Percentage of Lineaments Measured

Figure 20: Rose diagram of drainage segment lineaments in the Serpentine Bends quadrangle. All segment lengths are weighed and plotted equally. ER-4536 53

A rose diagram of the mapped linear passages in Carlsbad

Cavern, is shown in Figure 21. Again, all segment lengths were plotted equally in this diagram. Two distinct lineament sets, trending N75-90°E and N0-15°W, are approximately parallel to and normal to the reef escarpment.

A comparison of the two rose diagrams in Figures 20 and

21 shows that the orientations of linear stream segments and caves are the same, relative to the reef escarpment. This demonstrates that caves and streams have formed along the same fault and fracture sets associated with the reef complex. In addition, this shows that rectangular drainage patterns in carbonates can be used to determine the dominant transmissivity tensors in the study area, and can be used to determine system flow directions. With time, carbonate solution may increase the transmissivity of the system, but the transmissivity tensor will remain the same.

This relationship between ground-water flow (and therefore cave formation) and surface-water drainages implies that other caves in the area that existed in the east may have been exhumed by surface-water drainage.

Figure 22 shows a plan-view representation of Carlsbad

Cavern as compared to outlines of Rattlesnake and Slaughter

Canyons. This comparison demonstrates the effect of continued limestone dissolution on the continuity of the ER-4536 54

Reef Escarpment is oriented at approximately N80E.

Orientation of Lineaments Measured

NO N15W N15E N30W N30E N45E N46W

N60E N60W

N75W N76E

N90W N90E

36% 5%

23% 7%

2% 0%

0% 0%

0% ^ --- 2% 14% Percentage of Lineaments Measured

Figure 21: Rose diagram of linear passages in Carlsbad Cavern. All segment lengths are weighted and plotted equally. ER-4536 55

^\M ajor Lineament

Reef Trend Reef Trend a) Carlsbad Cavern b) Rattlesnake Canyon

Location Map

Reef Trend c) Slaughter Canyon

Figure 22: Comparison of plan-view outlines of: a) Carlsbad Cavern/ b) Rattlesnake Canyon and c) Slaughter Canyon. ER-4536 56

Capitan Aquifer. At Carlsbad Cavern, the ground surface along the reef escarpment has not yet been breached. The surface-water system still serves to recharge the Capitan

Aquifer. In Rattlesnake and Slaughter Canyons, continued dissolution has breached the upper part of the Capitan

Aquifer.

The effects of this structure-related dissection on the regional hydrologic system are substantial; leaving the lower portions of the Capitan Aquifer (primarily the less permeable forereef breccia member) as the only continuous unit in the regional system. This may cause a decrease in the effective hydraulic conductivity of the aquifer.

Another effect of this dissection is a loss of recharge into the regional system. The canyons serve to remove potential recharge from the Capitan Aquifer by allowing overland flow to leave the system; flowing into the Black River Valley to the south. On,a localized scale, these extensive fractures interconnect most of the hydrologic units vertically, and allows for the whole system to be conceptualized as having matrix flow-like properties on a regional scale.

The lineament formed by the Huapache fault zone extends to the south directly through Rattlesnake Canyon, where surface-water flow has incised through the reef escarpment along this ancient fault zone. The results are shown in ER-453 6 57

Figure 22; a prominent drainage in Rattlesnake Canyon trends

to the-northwest. This further demonstrates the effect of

fractures on the hydrologic system.

3.3.3 Regional drainage basin divides. Figure 23 shows a generalized view of the primary drainage basin divides. A clear direction of approximately N45°E is defined/ which does not coincide with the structural features of the reef complex. Rather, the regional flow tends to follow the regional dip of Tertiary rocks in the study area. In turn, the regional dip is controlled by the orientation of basement faults, like the Big Valley fault (Ritter, 1978).

This basement structural pattern may also be reflected in some of the observed linear drainage segments shown in

Figure 19. It is significant that ground-water flow is controlled not only by the immediate surroundings of the reef complex, but also by the overall tectonic setting of the region. T25S T23S T 2 1S Figure 23: Primary drainage basin divides. basin drainage Primary 23: Figure ER-4536 at hne Canyon Chance Last ok rroyo A Rocky ak Canyon Dark Carlsbad miles 58 ER-4536 59

Chapter 4

THE HYDROLOGIC SYSTEM

This chapter will present the regional ground-water

flow system, as well as local control mechanisms in the

Guadalupe Ridge area.

Combining the hydrostratigraphy and hydrostructure of the area reveals a complex hydrogeologic system that has both lithologic and structural controls, and aspects of both regional and local flow systems. Figure 24 is a schematic cross section of the hydrologic system. Generally, ground water flows along the regional dip from a major recharge area in the west to a major discharge area in the east.

Some infiltrating water is retained by detrital layers that act as barriers to vertical flow, creating shallow perched aquifers above a regional potentiometric surface a depth.

4.1 Hvdrolocric Data

Water well data of the study area are sparse, and are summarized in APPENDIX A. Several wells have been developed in the area immediately south and west of Carlsbad. The potentiometric surface in these wells is almost flat between

Carlsbad and Whites City; the head rises about one foot every 4 miles. ER-4536 60

Recharge

111 ! Major Recharge Area 1 ' I •Perched water tables Folding along Guadalupe Ridge Major Discharge Area Regional water

River

along □rain Delaware asin units

Figure 24: Schematic cross section of the regional hydrologic system. ER-4536 61

Drillers' logs from seven oil and gas wells north of

Walnut•Canyon in T 24 S, R 24 E allow elevation measurements

of the base of the Capitan Aquifer, but no ground-water data were recorded. Another line of four wells extends westward

from the town of Carlsbad, across the Seven River Embayment, to Texas Hill in T 22 S, R 21 E. These wells give an

indication of ground-water elevation in the Shelf Aquifer, and can be used for limited calibration during numerical modeling. Several wells within the study area recorded zones of lost circulation or cavities.

In addition to well data, Lake of the White Roses in

Lechuguilla Cave is believed to represent the regional water table at 3,130 feet (BLM, 1992). Other caves in the area, including Carlsbad Cavern, are completely above the regional water table.

4.2 Perched ♦Aquifers

Sandstone and siitstone layers that are present in some backreef units act as barriers to the vertical flow of infiltrating local recharge. The result is a series of shallow perched water tables within the Shelf Aquifer above the regional potentiometric surface. Figure 25 is a contour map estimating the potentiometric surfaces associated with the largest of these perched aquifers in and around the ER-4536 62

A Avalon 1 ■ " lt 1 1 1 1 l~t I ""I ■ 1 1 H nco

SEV.E N ' R\l V E R S Kj3

Corlsbod

'e |'M J 3 A^'M E \N 1 BARRERA I , / 1 V..- . ^ . . V-. - . r 1 1

A 0 A»L U P E

4 000

*. to 31 h J a /1 R.24E. R.27C 2 3 4 5 u. u «

CXrUMATtOK

DATA rr JOfimfiL ;*ir ta;s io iriT

itiia*tcrr iit'ilc.xtc -ItHmJ* »atia flnitiioJ above ranti ien leval. • i*~ fcrtvV.ion. Qrol:e:t !liu*« i:»>tleate lwlftlnllr Unto.

ft "— 0 -- 9--- ft 3."5< Jcntour Interval 1 Tout. Kitln aoiie o f auti.rat '.o«.

■ — — — — 3.40C Dralrn *\*V.l*{lll~ to Carli^ftJ 5» rii. x. ■ »■ ■ ■ — Jt- 3,600 Cunto'tr Interval 10* feet, ^re h'rt M iitr,b«arin<: r.one. -0 D & -- &• 3,700 ifrnioo into 3o«*«ll Conto'ir Intorvul 10/ feat. B «aln Main .o«o o." cnt-«r*t«a..«

Figure 25: Potentiometric surfaces of perched aquifers in the shelf units. ER-4536 63

Seven Rivers Embayment (Bjorklund and Motts, 1959). In

cases where the confining layer intersects the ground

surface, springs occur. If flow is sufficient, this may produce perennial stream reaches. Examples of this can be

found in Dark Canyon and Rocky Arroyo. The amount of flow

from these shallow perched aquifers into the underlying regional water table is unclear.

4.3 Guadalupe Ridge

In the Guadalupe Ridge area, these perched systems are

further affected by the local topography and structural geology. Infiltrating ground water flows down the flanks of anticlinal ridges into and along synclinal axes. Springs and caves are formed along flowpaths; indicators of the local system. Traces of the ancient Walnut Creek signify a previous structurally controlled surface-water channel adjacent to the reef that is still followed by several canyons today.

Significant canyons along the reef escarpment include

Big, Slaughter, Rattlesnake and Walnut. These topographic breaks are important hydrologically as they represent discontinuities in the Capitan Aquifer. They also divert potential recharge in the form of surface runoff out of the system and into the Delaware Basin. Large alluvial fans ER-453 6 64

have formed at the mouth of each canyon, and extend into the basin. These fans represent the recharge that has been lost to surface and near-surface flow.

4.4 The Regional System

Underlying the shallow local systems that are controlled by structure and topography is a regional hydrologic system. This deep regional system is controlled by the regional geologic setting.

4.4.1 Boundary Conditions. The fault-scarp face along the

Big Dog Valley Graben forms a regional ground-water divide and the western flow boundary of the hydrologic system. The eastern boundary of the system is along the Pecos River, which defines a fixed-head boundary (at 3100 feet) and the regional discharge area. A flow boundary exists on the basinward side of the Capitan Aquifer, to the south and east, formed by its contact with basinal evaporites of the

Ochoa Series and the reef escarpment.

The bottom of the regional hydrologic system is bounded and defined by the prominent sandstone tongue of the Cherry

Canyon Formation. When present, this sandstone layer acts as a barrier to vertical flow, and force water in the Shelf

Aquifer to migrate down-dip, towards the Pecos River Valley. ER-4536 65

Beyond the areal extent of this sandstone bed, water is

allowed to infiltrate deeper into the San Andreas Limestone

Aquifer. This aquifer directs flow northward, out of this

region, and into the Roswell Basin (Bjorklund and Motts,

1959). The northern flow boundary of this system is,

therefore, determined by the extent of the Cherry Canyon

sandstone.

4.4.2 Recharge. Generally, the entire hydrologic system is driven by the topographic relief of the Guadalupe Mountains.

Recharge occurs high in the Guadalupe Mountains along the western boundary of this system in the form of direct infiltration of precipitation; mainly thunderstorms

(Bjorklund and Motts, 1959) (Figure 24). This meteoric water infiltrates both the Capitan and Shelf Aquifers, and moves eastward in the general direction of the Pecos River.

The Capitan Aquifer is subsequently recharged by ground water from the Shelf Aquifer.

Regional recharge distribution is a function of climate and elevation. Evidence of a regional recharge area includes the presence of Pinon/Juniper forests that cover the Guadalupe Highlands.

Large precipitation events create overland flow which collects in canyons and narrow valleys of the Guadalupe ER-4536 66

uplands. This recharges a thin layer of alluvium that

covers' canyon floors, and in turn infiltrates to recharge

the Shelf Aquifer. About once every three years, enough

surface flow collects in Dark Canyon to cause a flash flood

(Bjorklund and Motts, 1959; BLM, 1992). Such events cause

local recharge through canyon bottoms far to the east of the

Guadalupe Mountains. Turbid, silty ground water has been observed in Carlsbad municipal wells immediately following

flash floods (Bjorklund and Motts, 1959).

4.4.3 Ground-water Flow. Contour maps of the regional potentiometric surfaces are shown in Figures 2 6 and 27.

These maps are based on the topographic continuity of the aquifers, the hydrogeologic framework, well data, locations of recharge and discharge areas, and boundary conditions.

Flow movement in the Shelf Aquifer is generally from the recharge area in the Guadalupe Mountains in the west to the east-northeast, along the regional dip into the Capitan

Aquifer. In the Capitan Aquifer, flow movement is from southwest to northeast along the reef axis and structural trends towards a discharge area along the Pecos River near the town of Carlsbad.

Ground-water flow paths in the CCNP region are affected by a variety of controlling factors. The amount of flow T25S T23S T21S potentiometric surface in the Shelf Aquifer. Shelf the in surface potentiometric iue 6 Cneta cnor a o te regional the of map contour Conceptual 26: Figure ER-4536 ContourInterval 2E 2E R26E R24E R22E =100 feet 67 potentiometric surface in the Capitan Aquifer. Capitan the in surface potentiometric iue2: ocpul otu mp f h regional the of map contour Conceptual 27: Figure T25S T23S T21S ER-4536 Contourfeet =Interval50 2E 2E R26E R24E R22E 68 ER-4536 69

through a given unit is directly related to the extent of fractures, which is in turn a function of lithology

(Bjorklund and Motts, 1959). Massive limestone and dolomite units are more highly fractured and, therefore, act as aquifers. Detrital sandstone and siltstone units contain relatively less substantial interconnected fracture networks, and act as less permeable units and relative barriers to flow (Motts, 1968).

The Shelf Aquifer is a combination of several aquifer units of the Artesia series in the backreef facies. The fracture network of the Shelf Aquifer is relatively consistent, however, and allows them to act as one hydrologic unit regionally. Regional flow in the Shelf

Aquifer is unconfined, and is generally to the northeast

(Figure 27). A regional ground-water surface exists at depth which appears closely related to water levels in the

Capitan Aquifer. A series of interbedded moderate to low permeability layers form perched aquifers in the Shelf

Aquifer. These perched aquifers flow generally eastward; their connection to an underlying regional potentiometric surface is unclear (Motts, 1968).

In this report, the Capitan Aquifer refers to the unit as defined by Hiss (1980), since its boundaries were designated on the basis of effective permeabilities. This ER-4536 70

includes the Goat Seep Limestone, as well as a highly fractured high permeability zone in the gradational portion of the Shelf Aquifer that abuts the reef (Table 3). Ground water in the Capitan Aquifer flows through a solution- enhanced fracture network located primarily within the massive member of the Capitan Limestone (Hiss, 1980). As a result, flow follows the reef axis to the northeast toward the town of Carlsbad. Ground water from the Shelf Aquifer flows generally eastward and into the Capitan Aquifer. The

Capitan Aquifer is characterized as a "french drain" or

"collection gallery" for the Guadalupe Plateau. This aquifer collects ground water which originates in the

Guadalupe highlands and Shelf Aquifer, and discharges it into the Pecos River Valley Alluvium in the area around

Carlsbad Springs (Figure 26).

The Capitan Aquifer is unconfined in most locations.

The exception is in the regional discharge area, where it is confined by the overlying evaporites of the Ochoa series

(Figure 28). Local structural features also affect ground­ water flow in and around Guadalupe Ridge, as demonstrated in this report.

The effective hydraulic conductivity of lower elevations is thought to be greater than that of the dissected Guadalupe Highlands for two reasons. First, in ER-4536 71

W Pecos River

'~T2msilI formation

33 ies

ites W

,\X\ v\x \\>^\ \

\ \ \

- Relatively hard water of alluvium.

- Relatively soft water of Capitan Aquifer.

- Mixed water of intermediate hardness.

Figure 28: Cross section showing the mixing of waters in the regional discharge zone near Carlsbad, New Mexico (modified from Bjorklund and Motts, 1959). ER-4536 72

the upper reaches of the system, most of the flow in the

Capitan Aquifer is restricted to the lower segments of the

aquifer; to include the less permeable forereef breccia member.

Secondly, the eastern portion of the study area, near

the town of Carlsbad, has been less affected by regional uplift and, therefore, has experienced a more constant topographic elevation through time. Periodic fluctuations

in the water table may have allowed oxidizing conditions to penetrate deep into the aquifer during periods of low ground-water elevations, causing dissolution along fractures. These solution channels would then be re­ submerged during wetter climatic conditions as ground-water levels rise to their former elevations. Water-table fluctuations would also have effected the upper reaches of the system, but the dissolution effects would have remained primarily above the water table, due to continued regional uplifting. This scenario results in large solution features below the water table in the areas of lower elevation around

Carlsbad, and solution channels located above the regional water table, as caves, in the higher elevations. Cave distribution and drill records of lost circulation zones in the eastern part of the study area support this theory (BLM,

1992) . ER-4536 73

4.4>4 Discharge. The largest regional discharge area in this hydrologic system is at Carlsbad Springs (Figure 24).

At this location, the Pecos River has down cut through the evaporites of the Ochoa Series to penetrate the Capitan

Limestone. The Capitan Aquifer is, therefore, allowed to discharge to the Pecos River alluvium in the Carlsbad area, as well as directly into the Pecos River (Figure 28).

Geochemical evidence helps to substantiate the hypothesis that there is a lack of eastward flow in the Capitan Aquifer beyond the Pecos River, and to demonstrate the mixing of relatively soft water from the Capitan Aquifer with relatively hard water from the Pecos River valley alluvium

(Bjorklund and Motts, 1959).

Figure 28 shows the mixing of waters in the discharge area schematically. Ground water follows the Capitan

Aquifer underneath the Pecos River Valley alluvium.

Initially, a higher head in the alluvium causes movement of alluvial water into the Capitan Aquifer. Mixing yields an intermediate aqueous composition, which is then discharged through the alluvium into springs and seeps that feed the

Pecos River. ER-4536 74

Chapter 5

NUMERICAL MODEL OF THE REGIONAL

HYDROLOGIC SYSTEM

The purpose of numerically modeling this study area is

to establish a preliminary steady state model that can be used as a tool to check the boundary conditions, mass balance, and general direction of ground-water flow in the deep regional system. MODFLOW was used to mathematically

simulate the regional fracture flow effectively as porous media flow. In this way, effective permeability ranges can be estimated for the different aquifers. This computer code

is well documented, verified and widely accepted for simulating two- or three-dimensional ground-water flow.

5.1 Model Application

A characterized model of the regional hydrologic system was developed using the hydrogeologic model, surface and subsurface characterization, and the primary data base.

Data from this hydrologic system model were integrated into the mathematical model.

5.1.1 Introduction. The conceptual model used in preparing this numerical model is based on the work presented in ER-453 6 75

chapters 2, 3 and 4 of this report. Two aquifer layers are used to represent the Shelf Aquifer (layer 1) and the

Capitan Aquifer (layer 2) in a quasi-three-dimensional model. Ground-water flow between the two aquifers is controlled by a vertical conductance layer. Both aquifers receive recharge by infiltration of precipitation, and the

Capitan Aquifer is subsequently recharged by flow from the

Shelf Aquifer. Discharge from the capitan occurs in the form of leakage into the Pecos River Valley alluvium.

Evapotranspiration in the area is assumed to be negligible because of the depth to the saturated zone. Anthropogenic effects are considered minimal, and the aquifer is assumed to be in steady state.

Data preparation for the model combined the characterization, hydrogeologic model and hydrologic system model as presented in this report. This included: geologic maps and cross sections (Figures 7, 8 , and 9); stratigraphic sections (Figures 6 and 16); topographic maps and analysis

(Figures 10 and 14); distribution of precipitation, vegetation, and springs in the area (Figures 11, 12, 13,

15); and the distribution of caves (Figures 17, 20, and 21).

Other data included: structural contour maps of subsurface lithologic units (Hayes, 1964), ground-water and aquifer ER-4536 76

base elevations from well data (Appendix A), and field

observations made on the surface and in caves.

5.1.2 Geometry and Grid Orientation. The model covers an area of 1,056 square miles. A grid was developed that

includes 33 columns and 32 rows; each grid block representing a section (one square mile)• The grid is oriented along cardinal directions since flow direction varies from due north to due east. This grid orientation coincides with the orientation of fractures in the study area (Figures 2 0 and 21). For convenience, grid lines correspond to township and range lines.

Two layers are defined to represent the regional ground-water system on the basis of estimated effective hydraulic conductivities as presented in chapter 4. Their areal extent and thicknesses were determined from geologic and structural*maps of the area, drillers1 logs, and scale cross sections (Newell et al., 1953; Hayes, 1964). contour maps that represent the input arrays for the bottoms of each aquifer are shown in Figures 29 and 30. A cross section of the model is shown in Figure 31.

5.1.3 Boundary Conditions. The boundary condition arrays for each layer are shown in Figures 32 and 33. The model is T25S T23S T21S ER-4536 iue2: otu o te otm f ae 1 atr Hayes/ (after 1 Layer of bottom the of Contour 29: Figure 94 Kle, 1971) Kelley, 1964; R22E 4000 otu nevl 2 feet 0 20 = Interval Contour R24E miles 5 R26E 77 T25S T23S T21S iue 0 Cnor f h bto o lyr (fe Hayes, (after 2 layer of bottom the of Contour 30: Figure 94 Kle, 1971). Kelley, 1964; ER-4536 2E 2E R26E R24E R22E otu nevl 20 feet 200 = Interval Contour miles 5 Carlsbad 78 ER-453 6 79

Cross Section of Numerical Model

Recharge

Shelf Aquifers (VCONT)

Capitan Aquifer

Figure 31: Cross section of numerical model looking northeast, along the reef axis. T25S T23S T21S iue 2 Budr cniin fr ae 1. layer for conditions Boundary 32: Figure _.i ER-4536 ” ' j ______i._ i J _ r 1 ” 2E 2E R26E R24E R22E / 1 i ' ------i i i NoFlowBoundary r . J . .. ! --- i i i i i --- miles 5 1 1 I * -- i i i j . Carlsbad i i i 80 T25S T23S T21S iue 3 Budr cniin fr ae 2. layer for conditions Boundary 33: Figure ER-453 ER-453 6 NoBoundaryFlow j .j R22E Constant Head Constant Boundary R24E mls 10 miles 5 Carls R26E A N 81 ER-4536 82

designed to be large enough to include the ground-water

divided, or no-flow boundaries, that define the Capitan and

Shelf Aquifer boundaries completely. In this way, mass balance estimates can be made without having to assume flux

into or out of the model from other systems or aquifers.

The basis for defining boundary conditions is the hydrologic system model presented in chapter 4. The fault-

scarp face along the Big Dog Canyon Graben forms a regional ground-water divide, and the western boundary of the study area. To the southeast, both layers are given no-flow boundaries to represent the reef escarpment and the

lithologic boundary with the low-permeability units of the

Delaware Basin.

The bottom of the hydrologic system is bounded and defined by the prominent sandstone tongue of the Cherry

Canyon Formation. Beyond the areal extent of this sandstone bed, water is Allowed to infiltrate deeper into the San

Andreas Limestone. This aquifer directs flow northward, out of this region, and into the Roswell Basin. The northern flow boundary of this system is, therefore, defined by the areal extent of the Cherry Canyon sandstone.

The Pecos River valley is used to define a fixed-head boundary at 310 0 feet to represent the natural discharge area surrounding Carlsbad Springs and the Pecos River. ER-4536 83

5.1.4 Input Parameters. Within the Block-centered Flow package in MODFLOW, layer types were assigned to each aquifer. Layer 1 was designated as a "type 1" aquifer, meaning the layer would remain unconfined for the duration of the model computation, and its saturated thickness would be allowed to vary with changes in water-table elevation.

Layer 2 was designated a "type 3" aquifer, meaning the layer may be confined or unconfined at different times and places during the model computation. This option allows the greatest degree of flexibility, and still allows the aquifer's saturated thickness to vary when it is unconfined.

The Shelf Aquifer is given a column-to-row anisotropy factor of 0.5. This means that the transmissivity or hydraulic conductivity in layer 1 in an east-west direction is twice that in a north-south direction. This is used to represent the hydrostructural conditions discussed in

Chapter 3 that tend to direct flow in the Shelf Aquifer to the east.

The value of vertical conductance (VCONT) used between layers is 0.02. This value was derived from the following equation to represent a highly conductive zone that borders the Shelf Aquifer.

VCONT = (b,_ + bMne + b^)'1 = (500 + 100 + 1000) 1 = 0.02 2Kt KMIie 2K: 10 1000 200 ER-4536 84

This quasi-layer is used to estimate the effect of the

increased effective permeabilities in shelf units as they become more calcitic adjacent to the Capitan Limestone.

This increase in permeability is discussed in chapter 3, and has been noted by other investigators (Bjorklund and Motts,

1959; MottS/ 1968; Hiss, 1980).

Recharge is distributed into the numerical model in accordance with the hydrologic system model, as discussed in chapter 4. Figure 34 shows a contour map of the recharge array used in the numerical model. Values of recharge across the region range from less that 1.0 inches per year in low-lying areas to as much as 11 inches per year in the

Guadalupe Mountains. The basis for these values is generally a function of the distribution of precipitation.

Initially, precipitation values were multiplied by a factor of 10%. The final array used factors ranging from 5% to

4 0%. The cany'on bottoms are assigned recharge values relatively greater than their surrounding areas. This represents the collection of some precipitation as overland flow in the canyons prior to infiltration.

Recharge in the area was input as "type 3" recharge.

This means that the recharge at each node is applied to the uppermost active cell in the vertical column, provide there is no constant head cell above it. This option allows iue 4 Rcag ary i ice pr year. per inches in array/ Recharge 34: Figure T25S T23S T21S ER-4536 R22E 2E R26E R24E 5 miles Carlsbad 85 i ER-4536 86

direct infiltration into the Capitan Aquifer (layer 2) in

outcrop locations.

The hydraulic conductivity array used for each layer is

given in Figures 35 and 36. The conductivity of layer 1 is

consistently one to two orders of magnitude lower than that

of layer 2. These values were estimated on the basis of the

hydrogeologic model presented in chapter 3, and modified

during the trial and error calibration process to allow mass

balance (Anderson and Woessner, 1992). The result was the

first numerically derived estimates of effective hydraulic

conductivities in the region.

As discussed in chapter 3, hydraulic conductivity values assigned to higher elevations were generally reduced

to simulate the dissection of the Guadalupe Highlands. This array also supported the fact that in the upper reaches of

the system, most of the flow in the Capitan Aquifer is restricted to the lower segments of the aquifer; to include the less permeable forereef breccia member. Additionally, drill records of lost circulation zones and subterranean cavities in the lower elevations (BLM, 1992) demonstrate the solution-enhanced permeability of this area. On this basis, conductivity values were assigned to the Shelf Aquifer ranging from 1.0 fpd in the high recharge zones to 10.0 fpd in the lower reaches of the basin. The Capitan Aquifer was iue 5 Hdalc odciiy ra fr ae 1- layer for array conductivity Hydraulic 35: Figure T25S T23S T21S R22E 2ER26E R24E Allvaluesday. perarein feet 5 ie 10 miles Carlsbad A T25S T23S T21S iue 6 Hdalc odciiy ra fr ae 2. layer for array conductivity Hydraulic 36: Figure ER-4536 R22E mls 10 miles 5 R24E Alldayvaluesper in are feet Carlsbad R26E 88 ER-4536 89

assigned hydraulic conductivity values ranging from 10.0 fpd

in the higher elevations to 50 0 fpd in lower areas. These values are consistent with effective hydraulic conductivity ranges assigned to similar rock types universally (Harlan,

Kolm, and Gutentag, 1989; Freeze and Cherry, 1979) .

5.2 Steadv-state Model Results and Calibration

In this steady-state model, convergence criteria were set at a tolerance of 0.1 feet maximum head change. These criteria were achieved in 85 steps. Initially, the model did not converge. The majority of maximum head changes appear along the southeast and northwest no-flow boundaries in both layers. Analyzing the spacial array of these changes identifies large head changes in corner cells and cells that are isolated from flow on three sides. Because all maximum head changes were negative, the acceleration constant was increased incrementally to 1.50; above this value, the model diverged. By adjusting the acceleration constant, these fluctuations were reduced, and the model converged.

The overall volumetric budget for the model is given in

Table 5. The mass balance of the system has a +2.60% discrepancy. All water entering the model is in the form of recharge, and all of the water that leaves the model does so ER-4536 90

Table 5: System budget of numerical model.

VOLUMETRIC BUDGET

CUMULATIVE VOLUMES L**3 RATES FOR THIS TIME STEP L * 3 /T

IN: IN:

STORAGE = .00000E+00 STORAGE = .00000E+00 C O N S T A N T H E A D = .OOOOOE+OO C O N S T A N T H E A D = .OOOOOE+OO RECHARGE = .47003E+07 RECHARGE = .47003E+07 TOTAL IN = .47003E+07 TOTAL IN = .47003E+07

OUT: OUT:

STORAGE = .00000E+00 STORAGE = .00000E+00 CONSTANT HEAD = .45797E+07 CONSTANT HEAD = .45797E+07 R E C H A R G E = .OOOOOE+OO RECHARGE = .00000E+00 TOTAL OUT = .45797E+07 TOTAL OUT = .45797E+07 IN - OUT = .12058E+06 IN - OUT = .12058E+06

% DISCREPANCY = 2.60 % DISCREPANCY = 2.60 ER-453 6 91

through the constant head nodes at the Pecos River. This allows- for future studies to focus on recharge mechanisms and heterogeneities associated with hydraulic conductivities of the various hydrogeologic units.

5.2.1 Variable Head Nodes. Contours of steady-state head surfaces in each layer are displayed in Figures 37 and 38.

The general shape and magnitude of these contours are similar to the potentiometric surfaces described by the hydrologic system model in chapter 4. Between Lechuguilla

Cave and the town of Carlsbad, well data are available to calibrate the model (see Appendix A). Table 6 compares the measured head values from these wells to those predicted by the numerical model. A standard error is given as a percentage of the saturated thickness. Figure 39 demonstrates the relationship between lost-circulation zones discovered during well drilling and head values derived numerically. The heads predicted by the numerical model for points near the discharge zone are consistently above the cavity zones (20 out of 22 points). This is consistent with the predictions of the hydrologic system model. For wells in other parts of the system (areas of higher elevation) the cavities are primarily above the predicted heads (15 out of

21 points). This again is consistent with expected cave T25S T23S T21S iue 7 Cnoro has n ae 1. layer in heads of Contour 37: Figure R43 92 ER-4536 ContourInterval 2E 2E R26E R24E R22E =100 feet miles5 Carlsbad T25S T23S T21S iue 8 Cnoro has n ae 2. layer in heads of Contour 38: Figure ER-4536 Contourfeet Interval= 50 R22E = 10 feet 10 = = 5 feet = 5 \ V \ t \ W \ W \ t \ V \

R24E 3

705 miles 5 _ Carlsbad R2SE 93 ER-4536 94

Table 6 : : Comparison of measured head values in wells to numerically predicted heads.

Well Aquifer Measured Head Model Head Difference Saturated ■"Error Number\Localion (feet) (feet) (feet) Thickness {% of (feet) Saturated Thickness)

22.26.01.233 Capitan 3105 3100 5 1500 0.3

21.26.36.221 Capitan 3103 3100 3 1500 0.2

22.25.20 Capitan 3105 3103 2 1500 0.1

22.24.23 Shelf 3350 3400 50 1200 4.1

22.23.22 Shelf 3800 3850 50 1000 5.0

* Calibration criteria of 5 % error. C0 Q. D> (D I -0 0.02 -D)0-i (D3c Z iue 9 Rltosi o eeain o ls circulation lost of elevations of Relationship 39: Figure zones to numerically derived heads. derived numerically to zones ER-4536 3000 2000 4000 5000 1000 0

1 3 5 6 5 4 3 2 1 0 ot iclto eeain (10 ft) (x1000 elevations circulation Lost er icag Zn + te Points Other + Zone Discharge Near 95 ER-4536 96

distribution as discussed in chapter 4.

The head contours also appear consistent with conceptual water table contours produced by other investigators (Motts, 1968; BLM, 1992) near the discharge area around Carlsbad.

5.2.2 Constant Head Nodes. Bjorklund and Motts (19 59) reported measured gains of the Pecos River in the Carlsbad

Springs area in 1954, when the Tansill Reservoir was temporarily drained and several dozen springs were exposed for investigation. Figure 40 shows this gain cumulatively as measured in 1954. This represents the only quantitative measurement of ground-water discharge of the hydrologic system.

A total of 4.56 x 106 cfd (or 52.8 cfs) are removed from the model at the constant head nodes along the Pecos

River. With an area of 1.9 x 108 ft2, and a K = 500 fpd, this results in a hydraulic gradient of about one foot every

4 miles; consistent with observed values. The total flux leaving the model, 52.8 cfs, varies by only 1.5% from the ground-water discharge of the Capitan Aquifer measured along the Pecos River in 1954. ER-4536 97

R.26 E. R. 27 E.

14 CARLSBAD TANS ILLUL JAM/ irr

Figure 40: Cumulative gain to Pecos River derived from ground-water flow from the Capitan Aquifer (from Bjorklund and Motts, 1959). ER-4536 98

5.3 Sensitivity Analysis of Recharge and Conductivity

The input values used for recharge and hydraulic

conductivity are non-unique. Several different combinations

of these two variables could yield similar results. It is

important, therefore, to understand the general effects that

changes in each of these variables will have on the model.

A sensitivity analysis of recharge values revealed that

the heads of cells in the upper reaches of the basin are

sensitive to changes in recharge. A 50% increase in recharge yielded an average head change of more than 100

feet. Cells with lower elevations seemed relatively less

sensitive to recharge changes. The same 5 0% increase only raised heads about 10 feet.

A sensitivity analysis of hydraulic conductivity values revealed that head values in cells located in the lower elevations are very sensitive to changes in conductivity.

When hydraulic'conductivity values were decreased by an order of magnitude, heads in the lower reaches of the system were raised by an average of 1000 feet. The gradient of ths potentiometric surface in this area was increased from 1 foot per mile to 10 feet per mile. Heads in the higher elevations were also affected by this change in conductivity values, but to a lesser extent. Heads in the upper section ER-4536 99

of the model increased an average of about 400 feet, and the hydraulic gradient was lessened. ER-4536 100

Chapter 6

SIGNIFICANT RESULTS AND RECOMMENDATIONS

This chapter is a summary of the significant results of this study, as they pertain to its initial purpose and objectives. Recommendations are made for continued

investigation to improve on the analysis and overall understanding of the hydrologic system in the CCNP region.

6.1 Summary of Significant Results

This investigation has contributed, in several ways, to the understanding of the CCNP regional hydrologic system.

Results include a regional numerical model, estimated ranges and distributions of hydrologic parameters, and the identification of local hydrologic control mechanisms in the

Guadalupe Ridge area.

Two prima'ry aquifers are identified in the region: the

Shelf Aquifer, consisting of backreef deposits in the

Capitan Reef Complex, and the Capitan Aquifer, which consists primarily of the Capitan and Goat Seep Limestones.

The system is recharged by direct precipitation; typically in the form of thunderstorms in the Guadalupe Mountains.

Ground water flows along the regional dip to the northeast until it is collected in the Capitan Aquifer. Acting as a ER-4536 101

"french drain"/ the Capitan Aquifer directs the ground water to a regional discharge zone along the Pecos River (Figure

24) .

Using a study method outlined by Kolm (1993)/ the first numerical model of the region is developed. The model shows that an average volume of about 4.6xl06 cubic feet of water enters and leaves the system each day. Furthermore, the model delineates the regional system as a closed basin, bounded to the south, west and north by ground-water divides, and to the east by the Pecos River. The general direction of ground-water flow is shown to be towards the northeast; from the Guadalupe Mountains to the town of

Carlsbad, New Mexico on the Pecos River.

This modeling effort has resulted in the estimation and array of hydrologic parameters in the study area.

Precipitation and recharge values are distributed on the basis of hydrologic data, vegetation cover and topography

(Figures 9 and 34). Precipitation is shown to range from 2 5 inches per year in the Guadalupe Mountains to 13 inches per year in the Pecos River Valley. Recharge is estimated to average about ten percent of precipitation. Recharge values are estimated to range from 1 inch per year in the lower elevations to 11 inches per year in the Guadalupe Mountains.

kmm LAKES LIBRARY COLORADO SCHOOL Of MINES G01DE* 00 30*01 ER-4536 102

A study of linear surface drainage segments and linear

cave passages revealed fracture orientations in the CCNP area (Figures 20 and 21). These orientations define two transmissivity tensors of the regional system; one approximately N75-9 0°E, the other N0-15°W.

Hydraulic conductivity values are estimated to range from 10 to 500 feet per day in the Capitan Aquifer, and from

1 to 10 feet per day in the Shelf Aquifer (Figures 35 and

36). Generally, the hydraulic conductivity of both aquifers is shown to increase towards the discharge zone.

Regional potentiometric surface of the two primary aquifers are estimated numerically (Figures 37 and 38).

When compared to head measurements taken from existing wells, model heads of the Capitan and Shelf Aquifers calibrate to within 0.5% and 5.0% of saturated thickness respectively.

Locally significant structural and topographic controls were identified in the immediate area of CCNP along

Guadalupe Ridge. These hydrologic control mechanisms include: 1) structural control by folding parallel to the reef escarpment, 2) topographic control within the canyons in the area, 3) loss of potential recharge to overland flow into the Delaware Basin, 4) topographic discontinuity of the

Capitan Aquifer, 5) orientation of fractures in the area, ER-4536 103

including the Huapache Fault zone, that define ground-water

flow direction.

6.2 Recommendations for Future Work

This report presents an overview of the regional hydrologic system. In order to completely understand the hydrologic system of the CCNP area, additional detailed studies and modeling efforts are required. Local control mechanisms along Guadalupe Ridge, that were identified in chapter 4, warrant further research.

Numerical models of these local sites would require finer model grids, more model layers, and flux boundaries that would simulate the external stresses of the regional system on the local model. The potentiometric surfaces and fluxes predicted by the regional model could be used to help estimate boundary conditions for these smaller site-specific models.

Further data collection will be required to fully assess the hydrogeology in the immediate CCNP area.

Specifically, potentiometric and geochemical data could be gained from further surveys of Lechuguilla Cave and Carlsbad

Cavern. In addition, detailed studies of recharge and hydraulic conductivity would improve the hydrogeologic and hydrologic system models. A full scale well data collection ER-4536 104

project would undoubtedly uncover additional hydrologic data. ER-4536 105

REFERENCES CITED

Anderson, M.P. and Woessner, W.W. 1991. Applied groundwater modeling; simulation of flow and advective transport. San Diego; Academic Press, Harcouirt Brace Jovanovich.

Boyd, D.W. 1958. Permian sedimentary facies, central guadalupe mountains, New Mexico. New Mexico Bureau of Mines and Mineral Resources Bulletin. 49.

Bureau of Land Management, Carlsbad Resource Area. 1992. Dark canyon environmental impact statement (draft)• BLM publication Number BLM-NM-PT-92-012-4110. Carlsbad, New Mexico: BLM.

Bjorklund, L.J., and Motts, W.S. 1959. Geology and water resources of the Carlsbad area, Eddy County, New Mexico. U.S. Geological Survey open-file report.

Fetter, C.W. 1988. Applied Hydrogeology. 2nd edition. Columbus, OH: Merrill Publishing Company.

Hayes, P. T. 1964. Geology of the Guadalupe Mountains, New Mexico. U.S. Geological Survey Professional Paper 446.

Hendrickson, G. E., and Jones, R. J. 1952. Geology and ground-water resources of Eddy County, New Mexico. New Mexico Bureau of Mines and Mineral Resources Ground Water Report 3.

Hill, C. A. 1987. Geology of Carlsbad Cavern and other caves in the Guadalupe Mountains, New Mexico and Texas. New Mexico Bureau of Mines and Mineral Resources Bulletin 117.

______. 1990. Sulfuric acid speleogenesis of Carlsbad Cavern and its relationship to hydrocarbons, Delaware Basin, New Mexico and Texas. AAPG Bulletin, Vol. 74. No. 11; 1685-1694.

Hiss, w. L. 1976. structure of the Permian-Guadalupian- Capitan Aquifer, southeast New Mexico and west Texas. New Mexico Bureau of Mines and Mineral Resources Resource Map 6. ER-4536 106

______. 198 0. Movement of ground water in Permian- Guadalupian aquifer systems, southeastern New Mexico and western Texas. New Mexico Geological Society Guidebook. 31st Field Conference. Trans-Pecos Region: 281-294.

Jagnow, D. H. 1989. Geology of Lechuguilla Cave, New Mexico. Subsurface and outcrop examination of the Capitan shelf margin, northern Delaware Basin: SEPM Core Workshop No. 13: 459-466.

______. 1991. Cross section and lineament map. Geologic Subcommittee Report: BLM/Karst Task Force. Roswell, New Mexico: BLM.

James, A. D. 1985. Producing characteristics and depositional environments of lower Pennsylvanian reservoirs, Parkway-Empire south area, Eddy County, New Mexico. AAPG Bulletin. Vol. 69. No. 7: 1043-1063.

Kelley, V.C., 1971. Geology of the Pecos country, southeastern New Mexico. New Mexico Bureau of Mines and Mineral Resources Memoir 24.

King, P. B. 1948. Geology of the southern Guadalupe Mountains, Texas. U.S. Geological Survey Professional Paper 215.

Kolm, K. E. 1993. Conceptualization and characterization of hydrologic systems. International Ground-Water Modeling Center Publication. GWMI 31-01.

______. In review. Hydrology of structural discontinuities in the Amargosa Desert, Nevada. Bulletin of the Association of Engineering Geologists.

Meissner, F.F. 1972. Cyclical sedimentation in mid-Permian strata. Cyclical sedimentation in the Permian Basin: West Texas Geological Society Publication 72-18: 203- 232.

Motts, W. S. 19 68. The Control of ground-water occurrence by lithofacies in the Guadalupian Reef Complex near Carlsbad, New Mexico. Geological Society of America Bulletin. Vol. 79. 283-298.

Mutel, C.F. and Emerick, J.C. 1992. From grassland to glacier. Boulder: Johnson Printing. ER-4536 107

Newell, N.D., with Rigby, J. K., Fischer, A. G., Whiteman, A. J., Hickox, J. E., and Bradley, J. S. 1953. The Permian Reef Complex of the Guadalupe Mountains region# Texas and New Mexico. San Francisco: W.H. Freeman.

Ritter, D.F. 1978. Process geomorphology. Dubuque, IA: Wm. C. Brown Company.

Silver, B.A. and Todd, R.G. 1969. Permian cyclic strata; northern Midland and Delaware Basins. AAPG Bulletin. Vol. 53. No. 5 : 2223-2251.

Tait, D.B., Ahlen, J.L. 1962. Artesia Group of New Mexico and West Texas. AAPG Bulletin. Vol. 46. No. 1: 504- 517.

Ward, R. F., St. C. Kendall, C. G., and Harris, P. M. 1986. Upper Permian (Guadalupian) facies and their association with hydrocarbons - Permian Basin, west Texas and New Mexico: AAPG Bulletin. Vol. 70. No. 3. 239-262. ER-453 6 108

SELECTED BIBLIOGRAPHY

Anderson, M.P. and Woessner, W.W. 1991. Applied groundwater modeling: simulation of flow and advective transport. San Diego: Academic Press, Harcourt Brace Jovanovich.

Anna, L.A. 1986. Geologic framework of the ground-water system in Jurassic and Cretaceous rocks in the northern great plains, in parts of Montana, North Dakota, South Dakota, and Wyoming. U.S. Geological Survey Professional Paper 1402-B.

Boyd, D.W. 1958. Permian sedimentary facies, central guadalupe mountains, New Mexico. New Mexico Bureau of Mines and Mineral Resources Bulletin. 49.

Bureau of Land Management, Carlsbad Resource Area. 1992. Dark canyon environmental impact statement (draft). BLM publication Number BLM-NM-PT-92-012-4110. Carlsbad, New Mexico: BLM.

Bjorklund, L.J., and Motts, W.S. 1959. Geology and water resources of the Carlsbad area, Eddy County, New Mexico. U.S. Geological Survey open-file report.

Busby, J.P., Kimball, B.A., Downey, J.S., and Peter, K.D. 1992. Geochemistry of ground-water aquifers and confining units of the northern Great Plains in parts of Montana, North Dakota, South Dakota, and Wyoming. U.S. Geological Survey Professional Paper 1402-F.

Compton, R.R. 19 62. Manual of field geology. New York: John Wiley & Sons.

Downey, J.S. 1984. Geohydrology of the Madison and associated aquifers in parts of Montana, North Dakota, South Dakota, and Wyoming. U.S. Geological Survey Professional Paper 1273-G.

______. 1986. Geohydrology of bedrock aquifers in the northern great plains in parts of Montana, North Dakota, South Dakota, and Wyoming. U.S. Geological Survey Professional Paper 1402-E. ER-4536 109

Fetter, C.W. 1988. Applied Hydrogeology. 2nd edition. Columbus, OH: Merrill Publishing Company.

Hayes, P. T. 19 64. Geology of the Guadalupe Mountains, New Mexico. U.S. Geological Survey Professional Paper 44 6.

Hendrickson, G. E., and Jones, R. J. 1952. Geology and ground-water resources of Eddy County, New Mexico. New Mexico Bureau of Mines and Mineral Resources Ground Water Report 3.

Hill, C. A. 1987. Geology of Carlsbad Cavern and other caves in the Guadalupe Mountains, New Mexico and Texas. New Mexico Bureau of Mines and Mineral Resources Bulletin 117.

______. 1990. Sulfuric acid speleogenesis of Carlsbad Cavern and its relationship to hydrocarbons, Delaware Basin, New Mexico and Texas. AAPG Bulletin. Vol. 74. No. 11: 1685-1694.

Hiss, W. L. 1976. Structure of the Permian-Guadalupian- Capitan Aquifer, southeast New Mexico and west Texas. New Mexico Bureau of Mines and Mineral Resources Resource Map 6.

______. 1980. Movement of ground water in Permian- Guadalupian aquifer systems, southeastern New Mexico and western Texas. New Mexico Geological Society Guidebook# 31st Field Conference, Trans-Pecos Region: 281-294.

Jagnow, D. H. 1989. Geology of Lechuguilla Cave, New Mexico. Subsurface and outcrop examination of the Capitan shelf margin# northern Delaware Basin: SEPM Core Workshop No. 13: 459-466.

______. 1991. Cross section and lineament map. Geologic Subcommittee Report: BLM/Karst Task Force. Roswell, New Mexico: BLM.

James, A. D. 1985. Producing characteristics and depositional environments of lower Pennsylvanian reservoirs, Parkway-Empire south area, Eddy County, New Mexico. AAPG Bulletin. Vol. 69# No. 7: 1043-1063. ER-4536 110

Kelley, V.C., 1971. Geology of the Pecos country, southeastern New Mexico. New Mexico Bureau of Mines and Mineral Resources Memoir 24.

King, P. B. 19 48. Geology of the southern Guadalupe Mountains, Texas. U.S. Geological Survey Professional Paper 215.

Kolm, K. E. 1993. Conceptualization and characterization of hydrologic systems. International Ground-Water Modeling Center Publication# GWMI 31-01.

______. In review. Hydrology of structural discontinuities in the Amargosa Desert, Nevada. Bulletin of the Association of Engineering Geologists.

Lamoureaux, P.E. and Powell, W.J. 1960. Stratigraphic and structural guides to the development of water wells and well fields in limestone terrain. International Association of Scientific Hydrology# Pub. 52. 363-375.

McDonald, M. G., and Harbaugh, A. W. 1988. A modular three-dimensional finite-difference ground-water flow model. U.S. Geological Survey Technigues of Water- Resources Investigations# Book 6.

Meissner, F.F. 1972. Cyclical sedimentation in mid-Permian strata. Cyclical sedimentation in the Permian Basin; West Texas Geological Society Publication 72-18: 203- 232.

Motts, W. S. 19 68. The Control of ground-water occurrence by lithofacies in the Guadalupian Reef Complex near Carlsbad, New Mexico. Geological Society of America Bulletin# Vol. 79. 283-298.

Mutel, C.F. and Emerick, J.C. 1992. From grassland to glacier. Boulder: Johnson Printing.

Newell, N.D., with Rigby, J. K., Fischer, A. G., Whiteman, A. J., Hickox, J. E., and Bradley, J. S. 1953. The Permian Reef Complex of the Guadalupe Mountains region# Texas and New Mexico. San Francisco: W.H. Freeman. ER-453 6 111

Peter, K.D., Kolm, K.E., Downey, J.S., and Nichols, T.C. 1988. Lineaments: significance, criteria for determination, and varied effects on ground-water systems — a case history in the use of remote sensing. Geotechnical Applications of Remote Sensing and Remote Data Transmission. ASTM STP 967: 46-68.

Parizek, R.R. 1976. On the nature and significance of fracture traces and lineaments in carbonate and other terrains. Karst Hydrology and Water Resources. Ft. Collins, CO: Water Resources Publications.

Ritter, D.F. 1978. Process geomorphology. Dubuque, IA: Wm. C. Brown Company.

Silver, B.A. and Todd, R.G. 1969. Permian cyclic strata; northern Midland and Delaware Basins. AAPG Bulletin. Vol. 53. No. 5 : 2223-2251.

Tait, D.B., Ahlen, J.L. 19 62. Artesia Group of New Mexico and West Texas. AAPG Bulletin. Vol. 46. No. 1 : 504- 517.

Ward, R. F., St. C. Kendall, C. G., and Harris, P. M. 1986. Upper Permian (Guadalupian) facies and their association with hydrocarbons - Permian Basin, west Texas and New Mexico: AAPG Bulletin. Vol. 70. No. 3. 239-262.

White, W.B. 1969. Conceptual models for carbonate aquifers. Ground Water. Vol 7, No. 3. 15-22. ER-4536 112

APPENDIX A

Well Database ER-4536 113

Table A-1. UelL Data Showing Base of Capitan Aquifer in the CCMP Area

• Well Number (Location) Surface elevation (ft) Elevation of Capitan Base (ft)

1 24.24.13.234 4428 3860 2 24.24.14.412 4518 • 3900 3 24.24.14.212 4242 3600 4 24.24.15.143 4388 3192 5 24.24.16.123 4050 2596 6 24.24.22.242 4643 3328 7 24.24.23.121 4639 2240 After BLM (1992). ER-4536 114

Table A-2. Weil Data Showing Elevation of Uater in Welts

Aquifer Uell Number (Location) Ground Surface Elevation of Uater Elevation (ft) Surface (ft) 1 Capitan 22.26.01.233 3130 3105 2 Capi tan 21.26.36.221 3120 3103 3 Capi tan 22.25.20 3800 3105 4 Shelf 22.24.23 4100 3350 5 Shelf 22.23.22 4050 3850 Source: Bjorklund and Motts (1959). ER-4536 115

Table A-3. Elevations of Cavities and Lost-circulation Zones

(Compiled by Dark Canyon EIS Team from Sources Listed Belov, 1992)

Listed below are wells which have been interpreted to have intercepted cavities, lost circulation zones, or have had cementing problems. The definitions for the terms used precede the table.

Wall Name: Name of the operator and well in the well record or other source.

Well Number: The number is based on the numbering system of the New Mexico State Engineer Office. For instance, well 21.26.31.241 is in the northwest quarter of the southeast quarter of the northeast quarter of Section 31, Township 21 south, Range 26 east.

Surface Elevation: The average elevation of the land surface near the well, in feet above sea level.

Cavity Depth: Depth of the cavity, lost-circulation zone, top of cement, or porous zone, in feet below land surface.

Cavity Elevation: Elevation of the cavity, lost-circulation zone, top of cement, or porous zone, in feet above sea level.

Type : The type of zone encountered; CA = cavity or crevice, LC = lost-circulation zone, TC = top of cement, when cement did not circulate to the surface, PZ = zone of increased porosity from borehole geophysical logs.

Source: Source of records used; BM = Bjorklund and Motts, 1959, HJ = Hendrickson and Jones, 1952, WR = well-completion or cementing records submitted to the Bureau of Land Management, U. S. Geological Survey, or New Mexico Oil Conservation Commission, TF = report of the Cave and Karst Task Force, CNL = borehole-compensated neutron porosity log, DTB = reported drilling-time break, SL = sonic log.

Surface Cavity Well Naat Well Nuaber Elevation Depth Elevation Type Source

Bobbit Well 21.26.31.241 . 3306 611 2695 CA KJ Water Well

Nat. Stock Well 22.22.32.344 4560 898 3662 CA HJ ER-4536 116

Water Well

Discovery Co. 22.24.05.414 4286 146 4140 LC WR Walt Can. 5 Fed. 1 369 3917 LC WR

John H. Trigg 22.24.06.111 3935 719 3216 TCWR Fed. IB 1-6

Superior Oil Co. 22.24.19.110 4578 200 4378 CA WR Cone Butte 1 1500 3078 TC WR

James E. Logan 22.24.24.234 3997 418 3S79 TC WR Rain Spring 1

Gulf Oil Corp. 22.24.26.323 40817 70 4011 CA WR Truitt Ranch 1 94 3987 CA WR 120 3961 CA WR 148 3933 CA WR

Atlan. Richfield 22.25.06.112 3741 1428 2313 TC WR Walt Canyon 3

Pennzoil Un. Inc. 22.25.08.421 3590 45 3545 TC WR Annie Brown 1 800 2790 TC WR

Belco Pet. Corp. 22.25.16.213 3708.4 917 2791 LC WR Pennzoil State 1

Belco Pet. Corp. 22.25.16.324 3628 630 2998 TCWR Pennzoil State 2

Siete 0 & G Co. 22.25.17.133 3830? 247 3853 LC WR Blackfoot Fed. 1 297 3533 TC WR 815 3015 LC WR 1763 2067 LC WR

Morris Antweil 22.25.19.412 3736 910 2826 LC WR Indian Wells 1

Siete 0 & G Co. 22.25.21.413 3610? 180 3430 LC WR Apache Fed. 1 202 3408 TC WR 253 3357 TC WR 1088 2522 TC WR 1125 2485 LC WR

Coquina Oil Corp. 22.25.23.422 3440 707 2733 TC WR ' FAF Fed. 1

Glenn Cope 22.25.30.224 3752 334 3418 LC WR Fed. 30 Com 1

Monsanto Co. 22.25.30.413 3869 1300 2569 TC WR Stein Fed. 1

Bluebird Oil Co. 22.26.03.214 3240 65 3175 CA BM Bluebird Well 345 2895 CA BM 535 2705 CA BM

Morris Antweil 22.26.03.231 3220 304 2880 LC/TC WR Valle Feliz 1

Amoco Prod. Co. 22.26.09.323 3353.6 440 2914 TC WR ER-4536 117

Lancaster Spr. Com 1 1340+ <2014 TC WR

Prim. Fuels Inc. 22.26.19.141 3409.1 206 3203 TC WR Amoco 19 Fed. 4 650 2759 LC WR 865 2544 TC WR

Prim. Fuels Inc. 22.26.19.231 3384.7 665 2720 TC. WR Amoco Fed. 3

Windham Well 22.26.20.312 3346 200 3146 CA HJ Water Well

Chevron USA, Inc. 22.26.21.413 3350? 301 3049 LC WR Lee K Fed. 1 318 3032 TCWR 900 2450 LC WR

Internorth, Inc. 23.24.06.242 4243.2 166 4077 LC WR Azotea Mesa Fed. 1 230 4013 TCWR

Cities Serv. Oil 23.24.08.322 4310 62 4248 TC WR Azotea Mesa Fed. 1 142 4168 TC WR

Amoco Prod. Co. 23.24.17.211 4239 120 4119 TCWR Fed. BL 1

Exxon Corp. 23.24.25.322 3853 788 3065 TC WR Ross Fed. 1

Yates Pet. Corp. 23.24.27.413 3860 83 3777 LC WR Crooked Creek Com 1 360 3500 LC WR 378 3482 LC WR

Exxon Corp. 23.25.01.312 3695 34 3661 TC WR Squaw Fed. 3 203 3492 LC WR 480 3215 TC WR 544 3151 LC WR 610 3085 TC WR 710 2985 TC WR

Hanagan Pet. Co. 23.25.11.242 3724 330 3394 TC WR Sheep Draw 1 610 3114 TC WR

Exxon Corp. 23 .25.24.242 3446 240 3206 TC WR Mary Fed. 4 318 3128 TC WR 346 3100 TC WR 390 3056 TC WR 689 2757 TC WR 762 2684 TC WR 892 2554 TC WR 1038 2408 TC WR

Amoco Prod. Co. 23.25.31.343 3881.1 500 3381 TC WR State IB Com 1

Exxon Corp. 23.25.36.421 3868 1384 2484 CA WR ER State 1 1390 2478 TC WR

Humble Oil Co. 23.26.31.124 3765 390 3375 TC WR North White City 1 420 3345 TC WR 520 3245 TC WR

Union Oil Co. 24.22.17.114 5690 226 5464 CA WR ER-4536 118

Fed White 1

Franklin, A & F 24.22.31.231 5828.3 340 5488 LC/TC WR Turkey Draw 1' 1207 4621 TC WR

Inexco Oil Co. 24.23.04.412 4399.2 125 4274 TC WR Goodwin State 1

Yates Pet. Corp. 24.23.25.324 4517 273 4244 TC WR Serpentine Bends 1 1050 3467 TCWR

Humble Oil Co. 24.23.30.432 5303 35 5268 LC WR Huapache Unit 12

Gulf Oil Corp. 24.24.09.342 4038 80 3958 TC WR Franklin Fed. 1 260 3778 LC WR

Yates Pet. Corp. 24.24.10.322 4177 1110 3067 PZ CNL Lechuguilla Can. BP Fed. 1

Meridian Oil Inc. 24.24.12.234 4032 680 • 3352 LC WR Jurnegan State Com 2

W.A. Moncrief Jr. 24.24.13.234 4428 1230 3198 LC TF Baldrige Can. Fed. Com 1

W.A. Moncrief Jr. 24.24.14.212 4242 719 3523 LC WR Baldrige Can. Fed. 2 985 3257 TC WR

W.A. Moncrief Jr. 24.24.15.143 4388 122 4266 LC TF Lechuguilla Can. 5 130 4228 LC TF

Water Well Test 24.24.16.442 4430 1115 3315 CA WR Test Well

Stock Well 24.24.19.434 4380 600 3780 LC WR Rock Bottom Well

Yates En. Corp.. 24.24.20.143 4277.6 66 4212 LC WR Sidewinder 1

W.A. Moncrief Jr. 24.24.22.242 4643 239 4404 LC TF Guadalupe Fed. 1 371 4272 TCTF 418 4225 LC WR 1120 3523 LC TF 1324 3319 TC WR 1570 3073 PZ CNL 1815 2828 PZ CNL 1870 2773 PZ CNL 1910 2733 PZ CNL 2065 2578 PZ CNL 2195 2448 PZ CNL

W.A. Moncrief Jr. 24.24.22.244 4643 1770 2873 PZ DTB Water Well Test 1791 2852 PZ DTB

W.A. Moncrief Jr. 24.24.23.121 4639 300 4339 LC TF Ridge Fed. 1 455 4184 LC TF 1460 3179 TC WR 1680 2959 PZ CNL 1770 2869 PZ CNL ER-4536 119

Inexco Oil Co. 24.25.02.142 4042 3642 TCWR Robb Spring 1 3042 TC WR

Amoco Prod. Co. 24.25.06.243 3894.2 1680 2214 PZ CNL State IX Com 1 1950 1944 PZ' CNL 2100 1794 PZ CNL 2420 1474 PZ CNL 2530 1364 PZ CNL

Amoco Prod. Co. 24.25.06.310 3825.7 1450 2376 PZ CNL HK Com 1 1920 1906 PZ CNL 2150 1676 PZ CNL

HNG Oil Co. 24.25.10.123 4039 1350 2689 PZ SL Horseshoe Bend 10 Com 1 1970 2069 PZ SL 2200 1839 PZ SL 2420 1619 PZ SL 2510 1529 PZ SL 2650 1389 PZ SL

David Fasken 24.25.18.134 4359.8 998 3362 LC WR Maralo State Com 1-Y

David Fasken 24.25.IS.134a 4359.8 1015 3345 LC WR Maralo State Com 1

Chaparral Prod. 24.25.24.234 3856 481 3375 CA WR Wood Canyon 1-Y 837 3019 LC WR

Superior Oil Co. 24.25.25.143 3578 680 2898 PZ SL Caverns Fed. Com 1

C & K Pet. Inc. 24.26.17.142 3491.5 727 2765 LC WR Exxon Fed. Com 1 750 2742 TC WR

C & K Pet. Inc. 24.26.17.414 3435 620 2815 PZ SL Exxon Fed. C o m '2 1070 2365 PZ SL 1210 2225 PZ SL

Gulf Oil Corp. 24.26.20.233 3379 1160 2219 PZ SL Estill AD Fed. 2

Taken from BLM (1992). ER-4536 12 0

APPENDIX B

Model Input and Output Files

Disk Instructions ER-4536 121

DISKETTE CONTENTS: VOLUME LABEL ER-4 53 6

FILE NAME CONTENTS (ASCII text files)

CARLSBAD.BAS Numerical model input for MODFLOW BASIC package.

CARLSBAD.BCF Numerical model input for MODFLOW BLOCK CENTERED FLOW package.

CARLSBAD.OC Numerical model input for MODFLOW OUTPUT CONTROL package.

CARLSBAD.RCH Numerical model input for MODFLOW RECHARGE package.

CARLSBAD.SIP Numerical model input for MODFLOW STRONGLY IMPLICIT PROCEDURE package.

M O D .OUT Numerical model input summary and output file from MODFLOW.