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Home , Bear Butte, Black Hills, Deadwood Formation, Hogback (geology), Reptile Gardens, Spearfish Formation

Prepared in cooperation with the Bureau of Reclamation, Department of Environment and Natural Resources, and the West Dakota Water Development District Ground-Water Resources in the Area, South Dakota

Water-Resources Investigations Report 03-4049

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

Ground-Water Resources in the Black Hills Area, South Dakota

By Janet M. Carter and Daniel G. Driscoll, U.S. Geological Survey, and J. Foster Sawyer, South Dakota Department of Environment and Natural Resources

Water-Resources Investigations Report 03-4049

Prepared in cooperation with the Bureau of Reclamation, South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District U.S. Department of the Interior GALE A. NORTON, Secretary

U.S. Geological Survey Charles G. Groat, Director

The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Government.

Rapid City, South Dakota: 2003

For additional information write to: District Chief U.S. Geological Survey 1608 Mt. View Road Rapid City, SD 57702 Copies of this report can be purchased from: U.S. Geological Survey Information Services Building 810 Box 25286, Federal Center , CO 80225-0286 CONTENTS

Abstract ...... 1 Introduction ...... 1 Ground-Water Processes ...... 2 Description of Study Area...... 3 Climate ...... 3 ...... 4 Ground Water ...... 6 Availability of Ground-Water Resources ...... 7 Characteristics of Major Aquifers ...... 8 General Characteristics ...... 8 Ground-Water Levels ...... 9 Characteristics of Minor Aquifers ...... 9 Water Quality of Ground-Water Resources...... 27 General Characteristics for Major Aquifers...... 27 General Characteristics for Minor Aquifers...... 30 Ground-Water Quality Relative to Water Use ...... 30 Summary ...... 32 References ...... 33 Glossary...... 35

FIGURES

1. Schematic diagram showing (A) porosity and permeability; and (B) aquifers and confining beds ...... 2 2. Map showing area of investigation for the Black Hills Hydrology Study...... 3 3. Graph showing long-term trends in precipitation for the Black Hills area, water years 1931-98...... 4 4. Stratigraphic column for the Black Hills ...... 4 5. Map showing distribution of hydrogeologic units in the Black Hills area ...... 5 6. Geologic cross section A-A′ ...... 6 7. Schematic diagram showing simplified hydrologic setting of the Black Hills area ...... 7 8. Boxplots showing distribution of well yields from selected aquifers ...... 9 9-13. Maps showing depth to top of: 9. ...... 10 10. Madison ...... 11 11. Minnelusa Formation ...... 12 12. Minnekahta Limestone ...... 13 13. Inyan Kara Group ...... 14 14-18. Maps showing generalized thickness of: 14. Deadwood Formation ...... 15 15. Madison Limestone and Englewood Formation ...... 16 16. Minnelusa Formation ...... 17 17. Minnekahta Limestone ...... 18 18. Inyan Kara Group ...... 19 19-23. Map showing potentiometric surface of: 19. Deadwood aquifer ...... 20 20. Madison aquifer and locations of major artesian springs ...... 21 21. Minnelusa aquifer and locations of major artesian springs...... 22 22. Minnekahta aquifer ...... 23 23. Inyan Kara aquifer...... 24 24. Map showing saturated thickness of the Madison aquifer...... 25 25. Map showing saturated thickness of the Minnelusa aquifer ...... 26 26. Selected hydrographs illustrating trends in ground-water levels...... 27 27. Map showing water temperature in the Madison aquifer ...... 28 28. Map showing specific conductance in the Madison aquifer ...... 28 29. Map showing specific conductance in the Minnelusa aquifer ...... 29 30. Map showing specific conductance in the Inyan Kara aquifer ...... 29 31. Graph showing relation between dissolved solids and well depth for Madison aquifer ...... 30 32. Boxplots showing hardness for selected aquifers ...... 30 33. Map showing hardness in the Inyan Kara aquifer ...... 31 34. Map showing sulfate concentrations in the Minnelusa aquifer ...... 31 35. Map showing radon concentrations in the Deadwood aquifer...... 32

TABLE

1. Summary of the characteristics of major aquifers in the study area ...... 8

Contents III CONVERSION FACTORS, VERTICAL DATUM, AND WELL-NUMBERING SYSTEM

Multiply By To obtain acre-foot 1,233 cubic meter acre-foot 0.001233 cubic hectometer foot 0.3048 meter gallons per minute 0.06309 liter per second inch 2.54 centimeter inch 25.4 millimeter mile 1.609 kilometer square mile 259.0 hectare square mile 2.590 square kilometer

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

° C = (° F - 32) / 1.8 Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD of 1929).

OTHER ABBREVIATIONS, ACRONYMS, AND SYMBOLS USED

mg/L milligrams per liter µg/L micrograms per liter pCi/L picocuries per liter

GWSI Ground Water Site Inventory database USEPA U.S. Environmental Protection Agency MCL Maximum Contaminant Level SMCL Secondary Maximum Contaminant Level USGS U.S. Geological Survey

Boxplots are a useful and concise graphical display for summarizing the distribution of a data set. Two different types of boxplots are used in this report. In both types, the center of the data (known as the median) is shown as the center line of the box. The variation or spread of the data (known as the interquartile range) is shown by the box height. • Maximum The first type is a truncated boxplot, and is used for all 90th percentile boxplots that do not show water-quality data. In the 75th percentile truncated boxplot, the whiskers are drawn only to the * Mean 90th and 10th percentiles of the data set. Thus, Median values included in the largest 10 percent and the 25th percentile smallest 10 percent of the data are not shown. The 10th percentile mean, maximum, and minimum values for the data ° Minimum set are shown.

° Outlier data value more than 3 times the The second type is a standard boxplot, and is used for interquartile range outside the quartile all boxplots that show water-quality data. In the × Outlier data value less than or equal to 3 and standard boxplot, the whiskers are drawn only to the more than 1.5 times the interquartile range last data value that is within 1.5 times the outside the quartile interquartile range (height of the box). Values Data value less than or equal to 1.5 times outside 1.5 times the interquartile range are called the interquartile range outside the quartile “outliers.” For water-quality data, these outliers are 75th percentile of interest when comparing to water-quality Median standards and general distribution of extreme values. 25th percentile Data value less than or equal to 1.5 times the interquartile range outside the quartile

°∼ Spring Water table

IV Contents Ground-Water Resources in the Black Hills Area, South Dakota

By Janet M. Carter and Daniel G. Driscoll, U.S. Geological Survey, and J. Foster Sawyer, South Dakota Department of Environment and Natural Resources

ABSTRACT in the Minnelusa aquifer; and radon con- resources within the Black Hills area. The centrations in the Deadwood aquifer. Black Hills Water Management Study was a The availability of ground-water Water quality of the major aquifers companion study conducted by the Bureau of resources in the Black Hills area is influ- generally is very good in and near outcrop Reclamation during 1992-2002 to evaluate enced by many factors including location, areas but deteriorates progressively with alternatives for management of water local recharge and ground-water flow distance from the outcrops. In the Min- resources in the area. Information summa- rized in this report was initially assembled in conditions, and structural features. Thus, nelusa aquifer, an abrupt increase in con- conjunction with these two studies. This the availability of ground water can be centrations of dissolved sulfate occurs report was produced in cooperation with the extremely variable throughout the Black downgradient from outcrop areas, where a Bureau of Reclamation, South Dakota Hills area, and even when water is avail- zone of active anhydrite dissolution Department of Environment and Natural able, it may not be suitable for various occurs. Resources, and West Dakota Water Develop- uses depending on the water quality. Most limitations for the use of ment District. ground water are related to aesthetic qual- The major bedrock aquifers in the The purpose of this report is to describe Black Hills area are the Deadwood, ities associated with hardness and high ground-water resources in the Black Hills Madison, Minnelusa, Minnekahta, and concentrations of chloride, sulfate, area. Availability and quality of water in the Inyan Kara aquifers. Minor bedrock sodium, manganese, and iron. Very few major aquifers (Deadwood, Madison, Min- aquifers occur in other hydrogeologic health-related limitations exist for ground nelusa, Minnekahta, and Inyan Kara) and units, including confining units, due to water; most limitations are for radionu- various minor aquifers in the Black Hills area fracturing and interbedded permeable clides, such as radon and uranium. In are described. Information collected and layers. addition, high concentrations of arsenic compiled from both the Black Hills have been measured in a few samples Hydrology Study and the Black Hills Water Various information and maps are from the Minnelusa aquifer. Management Study that relates to the avail- presented in this report that describe avail- ability of ground water in the Black Hills area ability and quality of ground-water is presented in this report. Specifically, this resources in the Black Hills area. How- INTRODUCTION report contains maps showing: (1) distribu- ever, there is no guarantee of obtaining tion of hydrogeologic units; (2) depth to the usable water at any location due to the Ground water originating in the Black top of the five formations that contain major extreme potential variability in conditions Hills area is used for municipal, industrial, aquifers; (3) thickness of the five formations that can affect the availability and quality agricultural, and recreational purposes that contain major aquifers; (4) potentio- throughout much of western South Dakota. of ground water in the area. Maps pre- metric maps for the five major aquifers; The Black Hills area is an important recharge sented in this report include the distribu- (5) saturated thickness of the Madison and area for aquifers in the northern . Minnelusa aquifers; (6) water temperature in tion of hydrogeologic units; depth to the About 45 percent of the recent population the Madison aquifer; (7) specific conduc- top of the five formations that contain growth in the Black Hills area has occurred in tance in the Madison, Minnelusa, and Inyan major aquifers; thickness of the five for- unincorporated areas where water-supply Kara aquifers; (8) hardness in the Inyan Kara mations that contain major aquifers; systems are not provided by municipalities aquifer; (9) sulfate concentrations in the potentiometric maps for the five major (Carter and others, 2002). Adequate water Minnelusa aquifer; and (10) radon concentra- aquifers; saturated thickness of the Madi- supplies for various uses can be difficult to obtain at some locations in the Black Hills tions in the Deadwood aquifer. More detailed son and Minnelusa aquifers; water tem- area. information regarding ground-water perature in the Madison aquifer; specific The Black Hills Hydrology Study was resources in the Black Hills area was summa- conductance in the Madison, Minnelusa, conducted by the U.S. Geological Survey rized by Carter and others (2002) and and Inyan Kara aquifers; hardness in the (USGS) during 1990-2002 to assess the Driscoll and others (2002) from a series of Inyan Kara aquifer; sulfate concentrations quantity, quality, and distribution of water previous topical reports.

Introduction 1 GROUND-WATER PROCESSES called recharge. Ground water is recharged soil or rock and how well the spaces are con- from rain water and snowmelt or from water nected. Porosity is the percentage of the soil Precipitation falling on the ’s sur- that leaks through the bottom of some lakes or rock volume that is occupied by pore face generally infiltrates into the soil horizon, and streams. Water can be discharged from an space, which is void of material. Permeability unless the soil is saturated or the infiltration aquifer by pumping from a well or by flowing is the measure of how well the spaces are capacity is exceeded. As water infiltrates into naturally from a spring. An aquifer is the connected (fig. 1A). An estimated one mil- the ground, some of it clings to particles of underground soil or rock through which lion cubic miles of the world’s ground water soil or to roots of plants just below the land ground water can easily move and which is stored within one-half mile below the land surface. Water not used by plants can move supplies usable quantities of water to wells or surface (U.S. Geological Survey, 1994). deeper into the ground through spaces or springs. An aquifer may be only a few feet cracks in the soil, sand, or rocks, until it thick to hundreds of feet thick; it may lie a Consolidated rock may contain frac- reaches a water table or a confining unit (such few feet below the land surface to thousands tures, small cracks, pore spaces, spaces as clay or ). The top of the water in the of feet below; it may underlie just a few acres between layers, and solution openings—all soil, sand, or rocks (top of the saturated zone) or as much as thousands of square miles. of which can hold water and may be con- is called the water table, and the water that nected. Vertical fractures may intersect hori- fills the spaces and cracks is called ground Rock materials may be classified as water. A confining unit is a relatively low- consolidated or unconsolidated. Consoli- zontal openings, enabling water to move from permeability layer of rock through which dated rocks (often called bedrock) may one layer to another. Water can dissolve water cannot easily move. After reaching the consist of limestone, dolomite, , carbonate rocks, such as limestone, to form water table or confining unit, the water then siltstone, shale, or . Unconsolidated solution openings through which water can fills the spaces (voids) and cracks above the rock consists of granular material such as move both horizontally and vertically. , water table or above the confining unit. sand, , silt, and clay. The amount of such as Wind and Jewel Cave (two of The process of infiltration of water ground water that can flow through soil or the largest caves in the world; fig. 2), are from the land surface to ground water is rock depends on the size of the spaces in the examples of large solution openings.

A Porosity and permeability

UNCONSOLIDATED MATERIAL ROCK

HIGH PERMEABILITY (water can easily flow)

Water-filled Water-filled pores fractures or solution openings LOW PERMEABILITY (water cannot easily flow)

B Aquifers and confining beds

Water-table Artesian well well Land surface PotentiometricPPotentiometricotentiometric surfacessurfaceurface

ZONE SANDSSANDAND CapillaryCCapillaryapillary UNSAT- URATED UNCONFINED fringeffringeringe AQUIFER e r u s

WellWell s

WaterWater tabletable e screenscreen r p

n a i s e t r

CONFINING Artesian pressure A BED CLAY

SSolutionolution CONFINED LIMESTONELIMESTONE

SATURATED ZONE openingopening AQUIFER

FractureFracture

Figure 1. Schematic diagram showing (A) porosity and permeability (modified from Clark and Briar, 1993); and (B) aquifers and confining beds (modified from Heath, 1983).

2 Ground-Water Resources in the Black Hills Area, South Dakota o 104o 45' 103 30' Indian Horse o Belle Fourche 44 45' Reservoir Cr EXPLANATION Owl Newell BELLE Creek OUTCROP OF MADISON LIMESTONE Creek Nisland (from Strobel and others, 1999) F BELLE FOURCHE O UR CHE RIVER OUTCROP OF MINNELUSA FORMATION Hay Creek R (from Strobel and others, 1999) E BUTTE CO Vale R I V TER LAWRENCE CO MEADE CO REDWA APPROXIMATE EXTENT OF THE BLACK Cox Saint Creek HILLS AREA, REPRESENTED BY Lake Crow Onge

Creek GENERALIZED OUTER EXTENT OF reek 30' Gulch Spearfish C THE OUTCROP OF THE INYAN KARA Whitewood Bear x GROUP (modified from Strobel and others, Gulch Butte Bottom Creek e 1999) ls Bear a Creek F Whitewood Butte Higgins Cr Creek Squ STURGIS Spearfish a Central Tinton w Cr City li Iron Cr ka o ood DEADWOOD l Cr w A 15' 103 ad Beaver Cr e D Cr Lead Bear h nnie Cr s A erry i trawb f S r Cr Creek Tilford a e Whitetail p Cheye Elk S nne Crossing Little Creek Roubaix ek Creek N Elk re Elk

Little . C 15' h F Boxelde fis o r r Piedmont a k e Ellsworth R r p a S Air Force S. Fork p i Base d Nemo

Rapid Cr C Creek r Blackhawk Cold S pri Cr ng ee s k Box Elder k For Rochford s adN o . For Rapid h k Ca R stle RAPID CITY Castle Cr Beav e Rapid r k Pactola Creek C C ree r C e re Reservoir e e Creek

k k Castle V Deerfield ictoria Creek Reservoir Spring o S. Fork r

44 C l e Cast Rockerville Sheridan Creek Creek Lake Hill City Mt. Rushmore National Keystone Memorial yon an Spring Harney Hayward LIMESTONE PLATEAU Iron C Peak n Mountain o x y x

n PENNINGTON CO

n Battle o a Cr y Sylvan Spok Hermosa C n CUSTER CO Lake an a Iron e Creek Creek s C le o Calamity Grace Bear B French Peak Creek CUSTER x Gulch Redbird e Gillette idg Creek Cool 45' Jewel Cave CUSTER National Monument Beaver E STAT French Fairburn PARK

Canyon Creek ighl H an Lame Canyon d C Creek o tt Wind Cave o Pringle n National Park w Creek o

o

WYOMING d

Wind Johnny

Cave SOUTH DAKOTA SOUTH Dewey Onyx Beaver Creek Red Cave

k Creek

o RIVER Hell o Buffalo Gap r 30' B d Creek l

o

C FALL RIVER CO H on ot roo ny B k Ca HOT SPRINGS Minnekahta Fall Oral R

CHEYENNE Cascade Springs SOUTH DAKOTA Black Oahe Edgemont Horsehead Hills Reservoir Mi Angostura ss ou o Creek Reservoir Creek r 43 15' d i oo w Area n o tt River o Igloo Creek shown C Provo

Hat

Base modified from U.S. Geological Survey digital data, 01020MILES 1:100,000, 1977, 1979, 1981, 1983, 1985 Rapid City, Office of City Engineer map, 1:18,000, 1996 Universal Transverse Mercator projection, zone 13 01020KILOMETERS

Figure 2. Area of investigation for the Black Hills Hydrology Study.

Unconsolidated materials in the Black aquifer is higher than the water table of the Outcrops of the Madison Limestone Hills area generally consist of sand and unconfined aquifer overlying the confined and Minnelusa Formation, which are areas gravel, boulders, silt, or clay deposited by aquifer. Artesian wells will flow where the where these geologic formations occur at the streams or in lakes. Alluvial deposits (allu- potentiometric surface is above the land land surface, are shown in figure 2. The gen- vium) generally are adjacent to streams in the surface. Semiconfining units contain some eralized outer extent of the outcrop of the flood plain. Well-sorted unconsolidated layers with low permeability but may Inyan Kara Group, which approximates the material can store large quantities of ground transmit some water to and from adjacent outer extent of the Black Hills area, also is water. The coarser materials—sand and aquifers. shown in figure 2. gravel—readily yield water to wells. Ground water can occur in aquifers under two different conditions. Where water- Climate table conditions occur, water does not fill the DESCRIPTION OF STUDY AREA formation containing aquifer material all the way to the top and the aquifer is considered The study area (fig. 2) consists of the The overall climate of the Black Hills unconfined. Where an aquifer is completely topographically defined Black Hills and adja- area is continental, which is characterized filled with water (fully saturated) and is over- cent areas located in western South Dakota. generally by low precipitation amounts, hot lain by a confining unit, the water can be con- The Black Hills are situated between the summers, cold winters, and extreme varia- fined under pressure and can rise above the and Belle Fourche Rivers. The tions in both precipitation and temperatures. top of the aquifer in an artesian well to a level study area includes most of the larger com- Local climatic conditions are affected by representing the potentiometric surface. In munities in western South Dakota and topography, with generally lower tempera- the schematic shown in figure 1B, the poten- contains about one-fifth of the State’s popula- tures and higher precipitation at the higher tiometric surface of the confined (artesian) tion. altitudes.

Description of Study Area 3 Long-term trends in precipitation for Geology vertical (or chronological) sequence of geo- water years 1931-98 for the study area are logic units of the Black Hills, is shown in shown in figure 3; a water year is the 12- Throughout geologic time, the Black figure 4. The geologic units are grouped into month period, October 1 through Hills area has experienced frequent periods of stratigraphic intervals representing hydro- September 30, and is designated by the cal- inundation by seas, extended , moun- geologic units comprising various aquifers, endar year in which it ends. Annual precipita- tain building, and intrusion by igneous rocks; confining units, and semiconfining units, as tion for the study area averaged 18.61 inches thus, the geology of the study area is very shown in the explanation for figure 5. and has ranged from 10.22 inches in water complex. The Black Hills uplift formed as an Figure 5 shows outcrops of the hydrogeo- year 1936 to 27.39 inches in water year 1995 elongated about 60 to 65 million years logic units and locations of numerous struc- (Driscoll, Hamade, and Kenner, 2000). ago. Numerous structural features, such as tural features in the study area. folds and fractures, were created by the defor- mation and displacement of rocks during the The oldest geologic units in the study uplift. Pairs of large anticlines (folds in which area are the -age crystalline the strata dip away from the axis like an arch) (igneous and metamorphic) rocks, which are and synclines (folds in which the strata dip exposed in the central core of the Black Hills 30 toward the axis like a trough) occur on the (fig. 5). Surrounding the Precambrian-age northern and southern flanks of the Black crystalline core is a layered series of sedi- Hills and plunge away from the uplift into the mentary rocks including , sand- 20 surrounding plains. Numerous smaller anti- stones, and that are exposed in roughly clines, synclines, and domes, along with concentric rings around the uplifted flanks of numerous faults and monoclines, occur the Black Hills, as shown in figure 5. The IN INCHES 10 throughout the Black Hills area. Igneous bedrock sedimentary units generally dip Annual precipitation intrusions, such as , were away from the flanks of the Black Hills as Long-term average ANNUAL PRECIPITATION, ANNUAL (18.61 inches) emplaced on the northern flanks of the uplift shown in the geologic cross section (fig. 6), 0 19301940 1950 1960 1970 1980 1990 2000 during the period. which shows the geologic units in a verti- WATER YEAR The is divided into cal cut along the line A-A′ in figure 5. Fol- four eras and spans from the Precambrian Era lowing are descriptions for the Paleozoic- and Figure 3. Long-term trends in precipitation for the (earliest) to the Era (latest). A -age sedimentary units in the Black Black Hills area, water years 1931-98. stratigraphic column, which portrays the Hills area.

ABBREVIATION FOR ERATHEM SYSTEM THICKNESS STRATIGRAPHIC GEOLOGIC UNITIN FEET DESCRIPTION INTERVAL

UNDIFFERENTIATED ALLUVIUM, TERRACES QUATERNARY QTac AND COLLUVIUM 0-50 Sand, gravel, boulders, and clay. & TERTIARY (?) CENOZOIC Tw WHITE RIVER GROUP 0-300 Light colored clays with sandstone channel fillings and local limestone lenses. TERTIARY Tui INTRUSIVE IGNEOUS ROCKS -- Includes rhyolite, latite, , and phonolite. Principal horizon of limestone lenses giving teepee buttes.

Dark-gray shale containing scattered concretions. PIERRE SHALE 1,200-2,700

Widely scattered limestone masses, giving small teepee buttes.

Black fissile shale with concretions.

NIOBRARA FORMATION 180-300 Impure and calcareous shale.

Kps Light-gray shale with numerous large concretions and sandy layers. 1350-750 Dark-gray shale. Impure slabby limestone. Weathers buff. GREENHORN FORMATION 225-380 Dark-gray calcareous shale, with thin Orman Lake limestone at base. MESOZOIC Gray shale with scattered limestone concretions. BELLE FOURCHE SHALE 150-850 Clay spur bentonite at base. MOWRY SHALE 125-230 Light-gray siliceous shale. Fish scales and thin layers of bentonite. MUDDY NEWCASTLE SANDSTONE SANDSTONE 0-150 Brown to light-yellow and white sandstone. SKULL CREEK SHALE 150-270 Dark-gray to black siliceous shale. GRANEROS GROUP FALL RIVER FORMATION 10-200 Massive to thin-bedded, brown to reddish-brown sandstone.

Kik Yellow, brown, and reddish-brown massive to thinly bedded sandstone, pebble conglom- LAKOTA FORMATION 35-700 erate, siltstone, and claystone. Local fine-grained limestone and coal. GROUP INYAN KARA 0-220 Green to maroon shale. Thin sandstone. UNKPAPA SS 0-225 Massive fine-grained sandstone. Greenish-gray shale, thin limestone lenses. Ju 250-450 Glauconitic sandstone; red sandstone near middle. SPRING FORMATION 0-45 Red siltstone, gypsum, and limestone. Red silty shale, soft red sandstone and siltstone with gypsum and thin limestone layers. R 375-800 T Ps Gypsum locally near the base. Pmk MINNEKAHTA LIMESTONE 125-65 Thin to medium-bedded, fine grained, purplish-gray laminated limestone. Po OPECHE SHALE 1 Red shale and sandstone. 25-150 Yellow to red cross-bedded sandstone, limestone, and anhydrite locally at top.

P Pm MINNELUSA FORMATION 1375-1,175 Interbedded sandstone, limestone, dolomite, shale, and anhydrite. PENNSYLVANIAN Red shale with interbedded limestone and sandstone at base. PALEOZOIC

MISSISSIPPIAN MADISON (PAHASAPA) LIMESTONE 1<200-1,000 Massive light-colored limestone. Dolomite in part. Cavernous in upper part. MDme

DEVONIAN ENGLEWOOD FORMATION 30-60 Pink to buff limestone. Shale locally at base. WHITEWOOD (RED RIVER) FORMATION 10-235 Buff dolomite and limestone. Ou WINNIPEG FORMATION 10-150 Green shale with siltstone. Massive to thin-bedded brown to light-gray sandstone. Greenish glauconitic shale, flaggy OCd 1 DEADWOOD FORMATION 0-500 dolomite, and flat-pebble limestone conglomerate. Sandstone, with conglomerate locally at the base. UNDIFFERENTIATED IGNEOUS AND PRECAMBRIAN pCu METAMORPHIC ROCKS Schist, slate, quartzite, and arkosic grit. Intruded by diorite, metamorphosed to amphibolite, and by granite and .

1 Modified based on drill-hole data Modified from information furnished by the Department of Geology and Geological Engineering, South Dakota School of Mines and Technology (written commun., January 1994)

Figure 4. Stratigraphic column for the Black Hills.

4 Ground-Water Resources in the Black Hills Area, South Dakota o o 45' 103 30' 104 EXPLANATION Indian Horse HYDRO- STRATI- o Belle Fourche 44 45' Reservoir Cr GEOLOGIC GRAPHIC MAP UNITS Owl Newell UNITS UNITS BELL Creek Creek Unconsolidated E QTac Alluvium, terraces, and Nisland units colluvium, undifferentiated F BELLE FOURCHE O White River UR Tw White River Group CHE RIVER aquifer Hay Creek R Tertiary Tui Undifferentiated intrusive E Vale BUTTE CO intrusive I V igneous rocks ER R MEADE CO units REDWAT LAWRENCE CO Cretaceous- Cox Kps Pierre Shale to Skull Creek Saint Creek sequence Lake Crow Onge confining Shale, undifferentiated unit Creek reek Inyan Kara Gulch Spearfish C Kik Inyan Kara Group 30' Bear aquifer Whitewood x Butte Gulch Jurassic- Ju Morrison Formation to Bottom sequence Creek e ls semiconfining Gypsum Spring Formation, Bear a Creek F unit undifferentiated Whitewood Butte Higgins Spearfish Cr STURGIS Creek Squ TRPs Spearfish Formation Spearfish a Central confining Tinton Cr w CityCr ali unit Iron od DEADWOOD lk o Cr wo A 103 ad 15' Minnekahta Beaver Cr e Pmk Minnekahta Limestone D Cr Lead Bear aquifer h nnie s A Cr rry i trawbe f S r Cr Creek Tilford Opeche a Po Opeche Shale e confining Whitetail p

S Cheyenne Elk unit Crossing Littl Minnelusa Creek Roubaix e Creek PPm Minnelusa Formation Elk eek aquifer N r Elk 15' Little C . Boxelder ish F Madison rf o MDme a r Piedmont Madison (Pahasapa) Lime- e k aquifer Ellsworth p R stone and Englewood

S S. Fork Rapid a Air Force p Base Formation i Nemo d

C Ordovician- Blackhawk Creek Cold Sp Cr r sequence Ou Whitewood Formation and rin Cr g semiconfining Winnipeg Formation ee s k Box Elder k For Rochford unit s adN o . Fo Deadwood h rk C Rapid OCd Deadwood Formation R ast RAPID CITY aquifer Castle le A' Be Cr av er Rapid Precambrian pCu Undifferentiated igneous C ek Pactola Creek r C e aquifer e C r and metamorphic rocks e r Reservoir k e Creek ek Castle V Deerfield icto a Creek

ri pring r Reservoir S 44o S. Fork C AA'LINE OF GEOLOGIC SECTION l e A Cast Rockerville Sheridan Creek FAULT—Dashed where approxi- Creek Lake mated. Bar and ball on down- Hill City Mt. Rushmore thrown side National Keystone ANTICLINE—Showing trace of axial Memorial yon plane and direction of plunge. an Spring Harney Hayward C Iron LIMESTONE PLATEAU Peak Dashed where approximated n Mountain o x y x

n PENNINGTON CO SYNCLINE—Showing trace of axial

n Battle o a Cr Hermosa y Sylvan Spok plane and direction of plunge. C a n CUSTER CO Lake n a Iron e Creek Dashed where approximated C Creek s e l MONOCLINE—Showing trace of o Calamity Grace Bear B Peak Creek axial plane. Dashed where French x Gulch CUSTER approximated Redbird e Gillette idg Creek Cool DOME—Symbol size approximately 45' Jewel Cave CUSTER proportional to size of dome. National Dome asymmetry indicated by Monument STATE Beaver French Fairburn arrow length

PARK

Canyon Creek ighl H an Lame Canyon d C Creek o tt Wind Cave o Pringle n National Park w

Creek o

o

WYOMING d

Wind Johnny

Cave SOUTH DAKOTA SOUTH Onyx Beaver Creek Dewey Cave Red

k Creek

o RIVER Hell o Buffalo Gap 30' r B d Creek l

o CO C FALL RIVER H on ot ny Brook Ca HOT SPRINGS Minnekahta Fall Oral R

CHEYENNE Cascade Springs

Edgemont Horsehead

Angostura o Creek Reservoir Creek 43 15' d oo w n o tt Igloo o Creek

C Provo 01020MILES

Hat 01020KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985 Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13

Figure 5. Distribution of hydrogeologic units in the Black Hills area (modified from Strobel and others, 1999).

Description of Study Area 5 WEST EAST WYOMING SOUTH DAKOTA

A Castle Creek South Fork A'

FEET Castle Creek South Fork

LIMESTONE PLATEAU FEET PPm OCd 7,000 7,000 MDme 6,000 6,000 Rapid Creek MDme Rapid Creek 5,000 Rapid Creek 5,000 Rapid Creek OCd Kik PPm Pmk Rapid City 4,000 Po Ju Rapid Creek QTac QTac 4,000 3,000 pCu 3,000 pCu Kps 2,000 2,000 1,000 1,000 TR Ps 0 0 VERTICAL EXAGGERATION X5 0 246810MILES VERTICAL DATUM IS NGVD OF 1929 042 68 10 KILOMETERS

Figure 6. Geologic cross section A-A′ (modified from Strobel and others, 1999). Location of section is shown in figure 5. Abbreviations for stratigraphic intervals are explained in figure 4.

The oldest sedimentary unit in the study Opeche Shale, which is overlain by the confining units, due to fracturing and inter- area is the Cambrian- and Ordovician-age Minnekahta Limestone. bedded permeable layers. In general, ground- Deadwood Formation, which is composed The Permian-age Minnekahta Lime- water flow in these aquifers is radially away primarily of brown to light-gray sandstone, stone is a fine-grained, purple to gray lami- from the central core of the Black Hills. The shale, limestone, dolomite, and local basal nated limestone (Strobel and others, 1999). bedrock aquifers primarily receive recharge conglomerate (Strobel and others, 1999). The Minnekahta Limestone is overlain by the from infiltration of precipitation on outcrops, In the northern and central Black Hills, the Spearfish Formation. and the Madison and Minnelusa aquifers also Deadwood Formation is overlain by The Spearfish Formation is a red, silty receive substantial recharge from streamflow Ordovician-age rocks, which include the shale with interbedded red sandstone and silt- losses. The unconsolidated units, which Whitewood and Winnipeg Formations. In the stone (Strobel and others, 1999). Massive include alluvium, terraces, and colluvium, southern Black Hills, where the Whitewood gypsum deposits are scattered throughout the are considered aquifers where saturated. and Winnipeg Formations are absent, the Spearfish Formation. Because gypsum is Alluvial deposits along streams commonly Deadwood Formation is overlain by the easily dissolved by water, numerous sink- are used as local aquifers. Englewood Formation, which generally is holes in the Spearfish Formation have Many of the sedimentary units contain present throughout the Black Hills area developed, especially in the northern Black aquifers, both within and beyond the study except in the crystalline core. The Englewood Hills (Epstein, 2000). Overlying the area. Within the Paleozoic-age rock interval, Formation is overlain by the Madison Lime- Spearfish Formation are Mesozoic-age units aquifers in the Deadwood Formation, stone. that are composed primarily of shale, silt- Madison Limestone, Minnelusa Formation, The -age Madison Lime- stone, and sandstone deposits. These units and Minnekahta Limestone are used exten- stone is a massive, gray to buff limestone with include the Cretaceous-age Inyan Kara sively. The aquifers are collectively confined some dolomite (Strobel and others, 1999). Group. by the underlying Precambrian-age rocks and The Madison Limestone was deposited by The Inyan Kara Group consists of the the overlying Spearfish Formation. Individu- shallow seas and subsequently was exposed Lakota Formation and overlying Fall River ally, these aquifers are separated by minor at land surface for approximately 50 million Formation. A resistant of Cretaceous- confining layers or by low-permeability years. During this period of extensive ero- age , mostly of the Lakota Forma- layers within the individual units. Extremely sion, rainwater, made slightly acidic during tion, completely encircles the Black Hills and variable leakage can occur between these its passage through the air, infiltrated slowly stands hundreds of feet above the sur- aquifers (Peter, 1985; Greene, 1993). down through the limestone, dissolving the rounding prairie. This ridge, known as the Confined (artesian) conditions gener- limestone and forming caves in the rocks Cretaceous , forms the general ally exist within the bedrock aquifers in loca- (Gries, 1996). The process of dissolving min- boundary between the Black Hills and the tions where an upper confining layer is eral and rock materials is called dissolution. prairie (Gries, 1996). The Lakota Formation present except in areas close to the formation As the caves collapsed, many of them broke consists of yellow, brown, and reddish- outcrop. Under confined conditions, water in through to the land surface, creating sink- brown, massive to thinly bedded sandstone, a well will rise above the top of the aquifer in holes. This process is called karstification, pebble conglomerate, siltstone, and claystone which it is completed. Flowing wells will which results in a type of topography (with that were deposited by rivers (Gott and result when drilled in areas where the poten- caves and sinkholes) called karst. Numerous others, 1974); locally there are lenses of lime- tiometric surface (level to which water will caves and fractures occur within the upper stone and coal. The Fall River Formation is a rise) is above the land surface. Flowing wells part of the Madison Limestone (Peter, 1985). brown to reddish-brown, fine-grained sand- and artesian springs that originate from The Madison Limestone is overlain by the stone, thin bedded at the top and massive at confined aquifers are common around the Minnelusa Formation. the bottom (Strobel and others, 1999). The periphery of the Black Hills. The Pennsylvanian- and Permian-age Inyan Kara Group is overlain by a thick The Precambrian-age basement rocks Minnelusa Formation consists mostly of sequence of various shale units with some generally have low permeability and form the yellow to red sandstone, limestone, dolomite, interbedded sandstone and limestone units. lower confining unit for the series of sedi- and shale (Strobel and others, 1999). In addi- mentary aquifers (fig. 7). However, localized tion to sandstone and dolomite, the middle aquifers occur in many locations in the crys- part of the formation contains anhydrite, Ground Water talline core of the Black Hills where sec- which can be easily dissolved by water, and ondary permeability (developed after the shale (DeWitt and others, 1986). The upper The hydrologic setting of the Black rock was formed) has resulted from weath- part of the Minnelusa Formation also may Hills area is schematically illustrated in ering and fracturing. Water-table (uncon- contain anhydrite, which generally has been figure 7. The major bedrock aquifers are the fined) conditions generally occur in these dissolved in or near the outcrop areas, occa- Deadwood, Madison, Minnelusa, Minne- localized aquifers, and topography can sionally forming collapse features. The kahta, and Inyan Kara aquifers. Minor bed- strongly influence ground-water flow direc- Minnelusa Formation is overlain by the rock aquifers occur in other units, including tions.

6 Ground-Water Resources in the Black Hills Area, South Dakota Minnelusa Formation LIMESTONE PLATEAU Limestone EXPLANATION Madison Formation MAJOR AQUIFER ood adw De CONFINING UNIT SPRING

Precambrian igneous and Alluvial metamorphic rocks aquifer

Deadwood Water table Potentiometric

Formation surface of the Flowing well Madison Spring Inyan Kara conduit aquifer Group Cave M M in inn n ekah elu ta Lim sa estone M F a orma dis tion on Dip of sedimentary rocks exaggerated. Limestone Relative thickness NOT to scale.

Figure 7. Schematic diagram showing simplified hydrologic setting of the Black Hills area. Schematic diagram generally corresponds with geologic cross section shown in figure 5.

Overlying the Precambrian-age rocks is Formation and sandstone and anhydrite in the thickness. The Minnekahta aquifer receives the Deadwood aquifer, which is contained upper portion. Shales in the lower portion of recharge primarily from precipitation on the within the Deadwood Formation and is used the Minnelusa Formation act as confining outcrop and some additional recharge from primarily near outcrop areas. Regionally, the layers to the underlying Madison aquifer; streamflow losses. The overlying Spearfish Precambrian-age rocks act as an underlying however, the extent of hydraulic separation Formation acts as a confining unit to the confining unit to the Deadwood aquifer, and between the two aquifers varies greatly Minnekahta aquifer and to other aquifers in the Whitewood and Winnipeg Formations, between locations and is not well defined. the underlying Paleozoic-age rock interval. where present, act as overlying semicon- Collapse breccia associated with dissolution Hence, most of the artesian springs occur fining units (Strobel and others, 1999). of interbedded anhydrite in the Minnelusa near the outcrop of the Spearfish Formation. Where the Whitewood and Winnipeg Forma- Formation may enhance secondary porosity Within the Mesozoic-age rock interval, tions are absent, the Deadwood aquifer is in to the aquifer (Long and others, 1999). The the Inyan Kara aquifer is used extensively, contact with the overlying Englewood Minnelusa aquifer receives substantial and aquifers in various other formations are Formation, which is considered similar in recharge from streamflow losses and precipi- used locally. The Inyan Kara aquifer receives hydrologic characteristics to the lower tation on the outcrop. Streamflow recharge to recharge primarily from precipitation on the Madison Limestone. the Minnelusa aquifer generally is less than to outcrop. The Inyan Kara aquifer also may The Madison aquifer generally occurs the Madison aquifer because much stream- receive recharge from leakage from aquifers within the karstic upper part of the Madison flow is lost to the Madison aquifer before in the underlying Paleozoic-age rock interval Limestone, where numerous fractures and reaching the outcrop of the Minnelusa (Swenson, 1968; Gott and others, 1974). As solution openings have created extensive sec- Formation. The Minnelusa aquifer is con- much as 4,000 feet of Cretaceous-age shales ondary porosity and permeability. The entire fined by the overlying Opeche Shale. act as the upper confining unit to aquifers in Madison Limestone and Englewood Forma- The Madison and Minnelusa aquifers the Mesozoic-age rock interval. tion were included in the delineation of the are distinctly different aquifers, but are con- Madison aquifer for this study. Thus, in this nected hydraulically in some areas. Many of report, outcrops of the Madison Limestone the artesian springs have been interpreted as and Englewood Formation (fig. 5) are originating at least partially from upward AVAILABILITY OF GROUND-WATER referred to as the outcrop of the Madison leakage from the Madison aquifer; however, RESOURCES Limestone for simplicity. The Madison the overlying Minnelusa aquifer and other aquifer receives recharge from streamflow aquifers probably contribute to artesian The availability of ground-water losses and precipitation on the outcrop. Low- springflow in many locations. Although the resources in the Black Hills area is influenced permeability layers in the lower part of the confining layers in the lower parts of the by many factors including location, local Minnelusa Formation generally act as an Madison and Minnelusa aquifers generally recharge and ground-water flow conditions, upper confining unit to the Madison aquifer. do not transmit water at a high rate, their and structural features. Thus, the availability However, collapse related to karst features in capacity to store water could influence how of ground water can be extremely variable the top of the Madison Limestone and frac- these aquifers respond to stress (Long and throughout the Black Hills area. The suit- turing related to the Black Hills uplift may Putnam, 2002). ability of available water supplies also can be have reduced the effectiveness of the over- The Minnekahta aquifer, which overlies limited by water quality, as discussed later in lying confining unit in some locations. the Opeche Shale, is contained within the this report. This section of the report provides The Minnelusa aquifer occurs within Minnekahta Limestone. The Minnekahta information and maps that describe potential layers of sandstone, dolomite, and anhydrite aquifer typically is very permeable, but well availability of ground-water resources in the in the lower portion of the Minnelusa yields can be limited by the small aquifer Black Hills area. Readers are cautioned that

Availability of Ground-Water Resources 7 there is no guarantee of obtaining usable recoverable because some of the water is con- Minnekahta aquifers could have well yields water at any location due to the extreme tained in unconnected pore spaces. Thus, as high as 1,000 gallons per minute in local- potential variability in conditions that can effective porosity, which is the porosity of a ized areas. Low well yields are possible in affect the availability and quality of ground rock that consists of interconnected voids, some locations for all the major aquifers. water in the area. was used in estimating the amount of recov- Maps showing estimated depths to tops erable water in storage (table 1). Where of formations that contain the major aquifers aquifer units are not fully saturated (generally (Deadwood, Madison, Minnelusa, Minne- Characteristics of Major Aquifers in and near outcrop areas), the saturated kahta, and Inyan Kara) are presented in thickness is less than the formation thickness figures 9-13. The depths shown are to the top General descriptions of aquifer charac- and the aquifer is unconfined. For the of the formations, which are not necessarily teristics and ground-water levels, with Madison and Minnelusa aquifers, it was pos- the depths to the tops of the water-bearing emphasis on the major aquifers, are presented sible to delineate the saturated thickness of layers. In fact, water-bearing layers in any in this section of the report. A series of maps the unconfined portions of these aquifers, as given formation may be minimal or absent at showing the depth and thickness of selected discussed later in this report. Average satu- many locations, especially in areas on or near geologic formations, and the potentiometric rated thicknesses of the unconfined and con- the outcrops. Readers are cautioned that rela- surface and saturated thickness of selected fined portions of the Madison and Minnelusa tively large errors in estimated depths can aquifers, also is presented. aquifers were used in storage estimates for occur because of large potential uncertainties these aquifers. For the other major aquifers, in estimated altitudes for tops of formations General Characteristics full saturation was assumed because more especially in areas with limited well and test- detailed information was not available. hole data. Aquifer characteristics, including area, The total volume of recoverable water Maps showing generalized thicknesses thickness, and storage volume, are presented stored in the major aquifers (including the of the formations that contain major aquifers in table 1 for the major aquifers in the study Precambrian aquifer) within the study area is are presented in figures 14-18. Thicknesses area. Aquifer characteristics for the Precam- estimated as 256 million acre-feet, which is shown are estimated formation thicknesses brian aquifer also are presented with the slightly more than 10 times the maximum and are not necessarily indicative of saturated major aquifers because numerous wells are storage of Oahe Reservoir, a large reservoir thicknesses at any given location. In fact, the completed in this aquifer in the crystalline on the northeast of the study formations may have little saturation or may core of the Black Hills. area (fig. 2). Although the volume of stored even be dry at many locations, especially in Localized aquifers occur in the igneous ground water is very large, the water quality areas on or near outcrops. Readers are again and metamorphic rocks that make up the may not be suitable for all uses in some parts cautioned that relatively large errors in esti- crystalline core of the Black Hills and are of the study area, as discussed in a following mated thicknesses can occur. referred to collectively as the Precambrian section of this report. The largest storage Maps showing estimated potentio- volume is for the Inyan Kara aquifer because aquifer. The Precambrian aquifer is not con- metric surfaces for the major aquifers are pre- of the large effective porosity (0.17). Storage tinuous and ground-water conditions are con- sented in figures 19-23. The potentiometric trolled mainly by secondary permeability in the Minnelusa aquifer is larger than in the contours on the maps show the approximate caused by fracturing and weathering. The Madison aquifer, primarily because of larger altitude to which water would rise in tightly aquifer is considered to be contained in the average saturated thickness. cased, nonpumping wells. In general, the area where the Precambrian-age rocks are Well yields (fig. 8) for wells completed direction of ground-water flow is perpendic- exposed in the central core, which has an area in the major aquifers were obtained from the ular to the potentiometric contours and in the of approximately 825 square miles in the USGS Ground Water Site Inventory (GWSI) direction of the hydraulic gradient (water study area. The thickness of the Precambrian database. The mean well yields for the aqui- flows from higher hydraulic head to lower aquifer has been estimated by Rahn (1985) to fers generally are much higher than the hydraulic head). In general, ground-water be generally less than 500 feet, which was median well yields because some well yields flow in the major aquifers is radially outward considered the average saturated thickness are very high. Well yields generally are lower from the uplifted area. However, structural for calculations of the estimated amount of for wells completed in the Precambrian features, such as folds and faults, and other recoverable water in storage (table 1). Wells aquifer than for the major aquifers (fig. 8) factors may have sufficiently large local in the Custer area have been completed at because the Precambrian aquifer is not con- influences on ground-water flow directions. depths greater than 1,000 feet, indicating that tinuous and most of the available water is Flow directions may be nearly parallel to localized aquifers are thicker in some loca- stored in fractures. The Madison aquifer has potentiometric contours in some locations, tions. The Precambrian aquifer is mostly the potential for high well yields, and the especially in the Madison aquifer (Long, unconfined, but may have locally confined mean well yield is higher in the Madison 2000). Readers are again cautioned that conditions. aquifer than the other major aquifers. The relatively large errors in mapped potentio- Large amounts of water are stored Minnelusa aquifer also has the potential metric contours can occur due to insufficient within the major aquifers, but not all of it is for high well yields. The Deadwood and data.

Table 1. Summary of the characteristics of major aquifers in the study area [--, no data]

Maximum Average Estimated amount Area formation saturated Effective of recoverable Aquifer (square miles) thickness thickness porosity1 water in storage2 (feet) (feet) (million acre-feet) Precambrian 35,041 -- 1500 0.01 2.6 Deadwood 4,216 500 226 .05 30.5 Madison 4,113 1,000 4521 .05 562.7 Minnelusa 3,623 1,175 6736 .05 570.9 Minnekahta 3,082 65 50 .05 4.9 Inyan Kara 2,512 900 310 .17 84.7 Combined storage for major aquifers 256.3

1From Rahn (1985). 2Storage estimated by multiplying area times average saturated thicknesses times effective porosity. 3The area used in storage calculation was the area of the exposed Precambrian-age rocks, which is 825 square miles. 4Average saturated thickness of the confined area of the Madison aquifer. The unconfined area had an average saturated thickness of 300 feet. 5Storage values are the summation of storage in the confined and unconfined areas. 6Average saturated thickness of the confined area of the Minnelusa aquifer. The unconfined area had an average saturated thickness of 142 feet.

8 Ground-Water Resources in the Black Hills Area, South Dakota 561 137 166 433 64 246 10,000 5,000 EXPLANATION 2,000 561 Number of wells with 1,000 yield data 500 Maximum 200 90th percentile 100 * 75th percentile 50 * * * Mean 20 * * Median 10 * 25th percentile 5 10th percentile 2 Minimum 1 0.5

0.2

WELL YIELD, IN GALLONS PER MINUTE YIELD, WELL 0.1 0.05

0.02 0.01 Precambrian Deadwood Madison Minnelusa Minnekahta Inyan Kara AQUIFER

Figure 8. Distribution of well yields from selected aquifers (data obtained from U.S. Geological Survey Ground Water Site Inventory database).

Maps showing estimated saturated respond quickly to climatic conditions. seldom is used because of generally more thicknesses of the unconfined areas of the Nearly all of the hydrographs for these aqui- reliable sources in the adjacent Madison or Madison and Minnelusa aquifers are shown fers (Driscoll, Bradford, and Moran, 2000) Deadwood aquifers. Local aquifers can exist in figures 24 and 25, respectively. Both the show a downward water-level trend prior to in the Spearfish confining unit where gypsum Madison and Minnelusa aquifers are uncon- 1993, as illustrated in the example hydro- and anhydrite have been dissolved, causing fined in and near outcrop areas, but generally graphs for a well pair completed in the increased porosity and permeability; these are confined (fully saturated) at some dis- Madison and Minnelusa aquifers (fig. 26A). aquifers are referred to as the Spearfish tance away from outcrops. In general, satu- This downward trend can be partially attrib- aquifer in this report. The Jurassic-sequence rated thicknesses are estimated as less than uted to dry climatic conditions in the Black semiconfining unit consists of shales and 200 feet for most outcrop areas. These areas Hills area during this period. Precipitation sandstones. Overall, this unit is semicon- may be especially susceptible to water-level amounts generally were above average after fining because of the low permeability of the fluctuations resulting from drought condi- 1993 (fig. 3), and water levels increased rap- interbedded shales; however, local aquifers tions, and these formations may be predomi- idly (fig. 26A). In general, there is very little nantly dry in many of these areas regardless exist in some formations such as the Sun- indication of long-term water-level declines dance and Morrison Formations. These aqui- of precipitation conditions. In most areas, the from ground-water withdrawals in any of the fers are referred to as the Sundance and Madison and Minnelusa aquifers are fully bedrock aquifers in the Black Hills area Morrison aquifers in this report. saturated within a short distance downgra- (Carter and others, 2002), as shown by the dient of the outcrops. However, in the south- long-term hydrograph for the Redwater The Cretaceous-sequence confining west part of the study area, neither aquifer is Minnelusa well (fig. 26B). unit mainly includes shales of low perme- fully saturated for a distance of about 6 miles Of the hydrographs for the 71 observa- ability, such as the Pierre Shale; local aquifers downgradient of the respective outcrops. tion wells presented by Driscoll, Bradford, in the Pierre Shale are referred to as the Pierre and Moran (2000), the aquifer in this report. Within the Graneros Ground-Water Levels Madison well showed the largest water-level Group, the Newcastle Sandstone contains an fluctuation of about 111 feet (fig. 26C). important minor aquifer referred to as the Daily water-level data were collected Larger water-level fluctuations at other loca- Newcastle aquifer. Because water-quality for 71 observations wells for the Black Hills tions in the Black Hills area may be possible. characteristics (discussed in a subsequent Hydrology Study. Hydrographs for these Such fluctuations could result in dry wells or section of this report) are very different wells through water year 1998 were pre- reduced pumping capacity during periods of between the Newcastle aquifer and the other sented by Driscoll, Bradford, and Moran declining water levels. units in the Graneros Group, data are pre- (2000). Hydrographs for four of these wells sented for the Newcastle aquifer separately are presented in figure 26 to illustrate the from the other units in the Graneros Group, fluctuations in water levels that can occur in Characteristics of Minor Aquifers known as the Graneros aquifer in this bedrock aquifers in the Black Hills area. For report. the hydrographs presented in this report, solid In addition to the major aquifers, many lines indicate continuous records and dashed other aquifers are used in the study area. The Tertiary intrusive units are present only lines indicate periods with discontinuous Newcastle Sandstone, White River Group, in the northern Black Hills, and generally are records, which may be based only on periodic and the unconsolidated units are considered relatively impermeable, although “perched” manual measurements in some cases. to contain aquifers where saturated (Strobel ground water often is associated with intru- Water levels can be affected by several and others, 1999). In addition, many of the sive sills. The White River aquifer consists of factors including pumping of nearby wells semiconfining and confining units shown in various discontinuous units of sandstone and and climatic conditions. Long-term water- figure 5 may contain local aquifers. This sec- channel sands along the eastern flank of the level declines could have various effects, tion of the report provides a brief overview Black Hills; local aquifers can exist where including changes in ground-water flow from Strobel and others (1999) of other aqui- saturated conditions occur. Unconsolidated patterns, reduction in springflow, increased fers in the study area that are contained in units of Tertiary or Quaternary age, including pumping costs, and dry wells. A large per- various units from oldest to youngest. alluvium, terraces, colluvium, and wind- centage of the observations wells completed The Whitewood Formation, where blown deposits, all have the potential to be in the Madison and Minnelusa aquifers present, can contain a local aquifer that local aquifers where they are saturated.

Availability of Ground-Water Resources 9 o 104o 45' 103 30' Indian Horse EXPLANATION o 44 45' Belle Fourche Cr T. 9 N. OUTCROP OF DEADWOOD Reservoir Owl Newell FORMATION (from Strobel BELL Creek Creek and others, 1999) E Nisland F DEADWOOD FORMATION ABSENT BELLE FOURCHE O (from Carter and Redden, 1999e) UR T. 8 N. CHE RIVER

Hay Creek DEPTH TO TOP OF DEADWOOD R

E BUTTE CO Vale FORMATION, IN FEET (from I V ER R CE CO MEADE CO Jarrell, 2000a) REDWAT LAWREN Less than 200 Cox T. 7 N. Saint Creek 200 to 400 Lake Crow Onge 400 to 600 Creek eek Cr 600 to 800 30' Gulch Spearfish Bear T. 6 N. 800 to 1,000 Whitewood x Butte Gulch 1,000 to 1,500 Bottom Creek e ls 1,500 to 2,000 Bear a Creek F 2,000 to 2,500 Whitewood Butte Higgins Creek Cr STURGIS Squ T. 5 N. 2,500 to 3,000 Spearfish a Central Tinton Cr w CityCr ali Iron od DEADWOOD lk o 3,000 to 3,500 Cr wo A 103 ad 15' Beaver Cr e 3,500 to 4,000 D Cr Lead Bear h nnie s A Cr erry i trawb 4,000 to 4,500 f S r Cr Creek Tilford T. 4 N. a

e Whitetail 4,500 to 5,000 p

S Cheyenne Elk Crossing 5,000 to 5,500 it Creek L tle Roubaix Elk eek Creek 5,500 to 6,000 N r Elk 15' Little C . Boxelder ish F 6,000 to 6,500 rf o a r Piedmont T. 3 N. e k Ellsworth No data p R

S S. Fork Rapid a Air Force p Base i Nemo d C Blackhawk Creek Cold Sp Cr r rin Cr g ee s k Box Elder T. 2 N. k For Rochford s adN o . Fo h rk C Rapid RAPID CITY R astl B Castle e C ea r ve r Rapid C k Pactola Creek r C e e e C r T. 1 N. e r Reservoir k e Creek ek Castle V Deerfield icto a Creek

ri pring r Reservoir S 44o S. Fork C l e Cast Rockerville Sheridan Creek T. 1 S. Creek Lake Hill City Mt. Rushmore National Keystone Memorial yon an Harney Iron Hayward LIMESTONE PLATEAU C Peak

n Spring Mountain T. 2 S.

o n x

y O x o PENNINGTON C n Battle

a y Cr Sylvan pok Hermosa n S C CO a a CUSTER Lake Iron ne C Cree Creek s k le o Calamity Grace Bear B T. 3 S. French Peak Gulch Creek CUSTER x Redbird e Gillette idg Creek Cool 45' Jewel Cave CUSTER National Monument STATE Beaver French Fairburn T. 4 S.

PARK

Canyon Creek ighl H an Lame Canyon d C Creek o Wind Cave tt o T. 5 S. National Park n Pringle Creek w o

WYOMING o d

Wind Johnny Cave Creek SOUTH DAKOTA SOUTH Beaver Dewey Onyx Red Cave T. 6 S.

k Creek

o RIVER Hell o Buffalo Gap 30' r B d Creek l

o FALL RIVER CO n C H yo ot roo an T. 7 S. B k C HOT SPRINGS Minnekahta Fall Oral R R. 8 E. R. 9 E. CHEYENNE Cascade Springs T. 8 S.

Edgemont Horsehead Angostura T. 9 S. o Creek Reservoir Creek 43 15' d oo w n o tt o R. 6 E. R. 7 E. Igloo Creek R. 5 E. C 01020MILES Provo T. 10 S.

Hat 01020KILOMETERS

R. 1 E. R. 2 E. R. 3 E. R. 4 E. Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985 Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13

Figure 9. Depth to top of Deadwood Formation.

10 Ground-Water Resources in the Black Hills Area, South Dakota