Water Resources of Mellette and

Todd Counties, South Dakota

Water-Resources Investigations Report 98-4146

Prepared in cooperation with the Rosebud Sioux Tribe, Mellette County,

West River Water Development District, and the

South Dakota Geological Survey

U.S. Department of the Interior

U.S. Geological Survey

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHITE RIVER

Sand

Creek

Crazy

HoleCr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

White

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek Cottonwood

Creek

Creek

Pine

North Branch

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail 83

18

18

83

63

63

44

44

53

MELLETTE COUNTY MELLETTE COUNTY

TODD COUNTY TODD COUNTY

MELLETTE COUNTY

TODD COUNTY
U.S. Department of the Interior

U.S. Geological Survey

Water Resources of Mellette and

Todd Counties, South Dakota

By Janet M. Carter

Water-Resources Investigations Report 98-4146

Prepared in cooperation with the Rosebud Sioux Tribe, Mellette County,

West River Water Development District, and the

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

Bruce Babbitt, Secretary

U.S. Geological Survey

Thomas J. Casadevall, Acting 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. Geological Survey.

Rapid City, South Dakota: 1998

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

Branch of Information Services

Box 25286

Denver, CO 80225-0286
Contents III

CONTENTS

Abstract.................................................................................................................................................................................. 1

Introduction ........................................................................................................................................................................... 2

Purpose and scope ....................................................................................................................................................... 2

Methods of investigation ............................................................................................................................................. 5

Generalized geology .................................................................................................................................................... 5

Acknowledgments ....................................................................................................................................................... 10

Water resources...................................................................................................................................................................... 10

Precipitation................................................................................................................................................................. 10

Surface water ............................................................................................................................................................... 10

Drainage basins.................................................................................................................................................. 10

Streams .............................................................................................................................................................. 10

Flow duration........................................................................................................................................... 16

Flood information.................................................................................................................................... 16

Lakes.................................................................................................................................................................. 18

Water quality...................................................................................................................................................... 18

Ground water ............................................................................................................................................................... 18

Shallow aquifers ................................................................................................................................................ 23

Alluvial aquifers ...................................................................................................................................... 24

Ogallala aquifer ....................................................................................................................................... 24

Arikaree aquifer....................................................................................................................................... 29

White River aquifer ................................................................................................................................. 33

Bedrock aquifers................................................................................................................................................ 38

Pierre Shale aquifer ................................................................................................................................. 38

Dakota Sandstone aquifer........................................................................................................................ 42

Inyan Kara aquifer ................................................................................................................................... 42

Minnelusa and Madison aquifers............................................................................................................. 44

Water quality...................................................................................................................................................... 44

Water use ............................................................................................................................................................................... 62

Summary and conclusions ..................................................................................................................................................... 65

References cited..................................................................................................................................................................... 67

ILLUSTRATIONS

1. Index map of South Dakota showing location of Mellette and Todd Counties, status of county

investigations, and locations of main physiographic divisions................................................................................... 3

2. Map showing locations of selected wells, test holes, and lines of hydrogeologic section in

Mellette and Todd Counties........................................................................................................................................ 4

3. Well-numbering system .............................................................................................................................................. 8

4. Generalized geologic map showing surficial geology of study area .......................................................................... 9

5. Structure contour map for the top of the Pierre Shale ................................................................................................ 11

6. Structure contour map for the top of the White River Group ..................................................................................... 12

7. Structure contour map for the top of the Arikaree Formation .................................................................................... 13

8. Map showing locations of drainage basins and U.S. Geological Survey streamflow-gaging

stations in Mellette and Todd Counties....................................................................................................................... 14

9. Daily-duration hydrographs for indicated percentage of time flow of the Little White River

below White River (station 06450500) in Mellette County was equal to or greater than that

shown, water years 1957-95 ....................................................................................................................................... 17
IV Contents

ILLUSTRATIONS—Continued

10. Daily-duration hydrographs for indicated percentage of time flow of the Keya Paha River at

Wewela (station 06464500) in Tripp County was equal to or greater than that shown,

water years 1957-95 ................................................................................................................................................... 17

11. Trilinear diagrams showing proportional concentrations of major ions for the Little White River........................... 21

12. Boxplots showing monthly variations in specific conductance for the Little White River above

Rosebud (station 06449300), 1981-95 ....................................................................................................................... 22

13. Boxplots showing variations in specific conductance at selected sites located on the

Little White River, 1950-95........................................................................................................................................ 22

14. Map showing extent and thickness of alluvial aquifers ............................................................................................. 25

15. Map showing potentiometric surface of alluvial aquifers .......................................................................................... 26

16. Graphs showing water-level fluctuations in alluvial aquifers and cumulative monthly departure

from normal precipitation at Valentine, Nebraska ..................................................................................................... 27

17. Hydrogeologic section A-A' showing aquifers of Quaternary, Tertiary, and Cretaceous

age in Todd County .................................................................................................................................................... 28

18. Map showing potentiometric surface of the Ogallala aquifer .................................................................................... 30

19. Graphs showing water-level fluctuations in the Ogallala aquifer and cumulative monthly

departure from normal precipitation at Valentine, Nebraska ..................................................................................... 31

20. Hydrogeologic section B-B' showing aquifers of Quaternary, Tertiary, and Cretaceous age in Todd County .......... 32

21. Map showing potentiometric surface of the Arikaree aquifer.................................................................................... 34

22. Graphs show water-level fluctuations in the Arikaree aquifer and cumulative monthly

departure from normal precipitation at Valentine, Nebraska ..................................................................................... 35

23. Hydrogeologic section C-C' showing aquifers of Quaternary, Tertiary, and Cretaceous

age in Mellette and Todd Counties............................................................................................................................. 36

24. Map showing potentiometric surface of the White River aquifer .............................................................................. 37

25. Graphs showing water-level fluctuations in the White River aquifer and cumulative

monthly departure from normal precipitation at Valentine, Nebraska ....................................................................... 39

26. Hydrogeologic section D-D' showing aquifers of Quaternary, Tertiary, and Cretaceous

age in Mellette and Todd Counties............................................................................................................................. 40

27. Map showing potentiometric surface of the Pierre Shale aquifer .............................................................................. 41

28. Graphs showing water-level fluctuations in the Dakota Sandstone aquifer and cumulative

monthly departure from normal precipitation at Valentine, Nebraska. ...................................................................... 43

29. Trilinear diagrams showing proportional concentrations of major ions in ground-water

samples ...................................................................................................................................................................... 53

30. Boxplots of chemical constituents in ground-water samples ..................................................................................... 55

31. South Dakota irrigation-water classification diagram................................................................................................ 63

TABLES

1. Generalized stratigraphic column showing geologic units and some of their characteristics ................................ 6

2. Summary of data for streamflow-gaging stations in and near Mellette and Todd Counties................................... 15

3. Summary of chemical analyses for the Little White River at gaging stations above Rosebud and

below White River, 1950-95................................................................................................................................... 19

4. Summary of the characteristics of major aquifers in Mellette and Todd Counties................................................. 23

5. Summary of chemical analyses for ground water................................................................................................... 45

6. Significance of chemical and physical properties of water .................................................................................... 59

7. Ground- and surface-water withdrawals in Mellette and Todd Counties during 1995........................................... 62

8. Estimated withdrawal of ground water in Mellette County during 1995 ............................................................... 64

9. Estimated withdrawal of ground water in Todd County during 1995 .................................................................... 64

VERTICAL DATUM

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—a geodetic 

datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called 

Sea Level Datum of 1929.
Abstract 1

Water Resources of Mellette and Todd Counties,

South Dakota

By Janet M. Carter

ABSTRACT

Mellette and Todd Counties are located in 

south-central South Dakota and have a combined 

area of 2,694 square miles. The White River and 

its tributaries, which include the Little White 

River, drain Mellette County and about one-half of 

Todd County. Tributaries to the Niobrara River, 

which include the Keya Paha River, drain the other 

one-half of Todd County. The average discharge 

of the Little White River is about 56 cubic feet per 

second as the river enters Todd County and is 

about 131 cubic feet per second as it discharges to 

the White River in northern Mellette County. The 

average discharge of the Keya Paha River just outside Todd County is about 39 cubic feet per 

second. The average annual runoff for Mellette 

and Todd Counties ranges from 0.94 to 2.36 inches 

based on records from nine streamflow-gaging 

stations in and near the counties. The average 

annual runoff is 1.62 inches, which compares with 

the average annual precipitation of about 

19 inches.

In Todd County, shallow wells completed in 

the alluvial, Ogallala, Arikaree, and White River 

aquifers generally can supply water that has low 

concentrations of dissolved solids, is fresh, and is 

soft to moderately hard. Ground water from 

shallow aquifers is limited in Mellette County; 

therefore, deep wells, often greater than 

1,000 feet, are sometimes installed. The Pierre 

Shale often is used to supply rural domestic and 

stock wells in Mellette County even though well 

yields are low and the water has high dissolved 

solids, is moderately saline, and is very hard.

Alluvial aquifers are present in both 

counties and store an estimated 1.6 million acrefeet of water. The water quality of the alluvial 

aquifers is dependent on the underlying deposits, 

and generally the water has low concentrations of 

dissolved solids, is fresh, and is soft to moderately 

hard where underlain by the Ogallala and Arikaree 

Formations; has moderate concentrations of dissolved solids, is slightly saline, and is hard where 

underlain by the White River Group; and has high 

concentrations of dissolved solids, is saline, and is 

very hard where underlain by the Pierre Shale. 

Also, yields often are lower where the alluvial 

aquifers are underlain by the Pierre Shale.

The Ogallala aquifer is present in only Todd 

County, and the Arikaree aquifer is present 

throughout most of Todd County and southwestern 

and south-central Mellette County. The Ogallala 

aquifer contains an estimated 17 million acre-feet 

of water in storage, and the Arikaree aquifer contains an estimated 50 million acre-feet of water in 

storage. Both aquifers generally are suitable for 

irrigation, and yields from these aquifers are sometimes greater than 1,000 gallons per minute. 

Nitrate concentrations in 13 out of 92 water 

samples collected from the Ogallala aquifer 

exceeded the Primary Drinking Water Maximum 

Contaminant Level (MCL) of 10 milligrams per 

liter. In 11 out of 46 samples collected from the 

Arikaree aquifer, arsenic concentrations exceeded 

the MCL of 50 micrograms per liter. 
2 Water Resources of Mellette and Todd Counties, South Dakota

The White River aquifer, where present, is 

usually the shallowest source of ground water in 

Mellette County. The White River aquifer also is 

used in northern Todd County where the Ogallala 

and Arikaree aquifers are not present. The White 

River aquifer contains an estimated 50 million 

acre-feet of water in storage. Reported yields from 

the aquifer range from 1 to 30 gallons per minute, 

which generally is insufficient to support irrigation 

in most areas. However, yields are sufficient for 

livestock-watering and rural-domestic purposes. 

In both counties, the Pierre Shale is the shallowest bedrock aquifer and is exposed at the land 

surface throughout most of Mellette County. This 

aquifer is used primarily in Mellette County. 

Although the aquifer contains an estimated maximum of 1.5 million acre-feet of water in storage, it 

is not a viable source of ground water because the 

aquifer is relatively impermeable, yields are low, 

and water usually can be obtained from shallower 

sources, especially in Todd County. Reported 

yields from the Pierre Shale aquifer range from 

1 to 8 gallons per minute.

Because few test holes and wells penetrate 

below the Pierre Shale, little is known about the 

extent of the deeper bedrock aquifers. All wells 

completed in the Dakota Sandstone, Inyan Kara, 

and Minnelusa and Madison aquifers in the 

counties are used for stock-watering purposes. 

High concentrations of dissolved solids and hard 

water are characteristic of the water quality in the 

bedrock aquifers. Depths to the top of the deeper 

bedrock aquifers range from 1,270 feet to greater 

than 2,000 feet below land surface.

INTRODUCTION

In 1992, the U.S. Geological Survey (USGS) in 

cooperation with the Rosebud Sioux Tribe, Mellette 

County, West River Water Development District, and 

the South Dakota Geological Survey, began a 5-year 

investigation to describe and quantify the water 

resources of Mellette and Todd Counties. This investigation was needed because of the limited information 

available on the surface- and ground-water resources in 

Mellette and Todd Counties. This information is 

needed by local, county, State, and Tribal officials to 

develop sound water-management plans.

Mellette and Todd Counties, which comprise the 

study area, are located in south-central South Dakota 

(fig. 1). Mellette County has an area of 1,306 square 

miles, and Todd County has an area of 1,388 square 

miles. According to the U.S. Census Bureau, the 1995 

population was 2,002 in Mellette County and 9,105 in 

Todd County. The climate is subhumid, and the 

average annual precipitation is about 19 inches in both 

counties. Most of the land area is used for range or 

native hay production, and the main source of income 

in both counties is cattle ranching. Less than 

15 percent of the land is used for crops, which include 

wheat, sorghum, oats, corn, and alfalfa.

The White River forms the northern boundary of 

Mellette County. Most of the area of the two counties 

is rolling, and numerous deep valleys drain into the 

White River to the north or into the Niobrara River to 

the south in Nebraska. The headwaters to the Keya 

Paha River are located in Todd County. All of Mellette 

County and the northern part of Todd County are in the 

Great Plains physiographic province. The southern 

part of Todd County is in the Sand Hills physiographic 

province (fig. 1).

The original boundaries of the Rosebud Indian 

Reservation included all or nearly all of Mellette, Todd, 

Gregory, and Tripp Counties, and a small portion of 

Lyman County. In the early 1900’s, the Rosebud 

Reservation was opened for homesteading. As a result, 

scattered tracts of non-Indian owned land are present in 

both Mellette and Todd Counties. In 1975, the 

Rosebud Indian Reservation boundary was revised to 

include only Todd County (fig. 2).

Purpose and Scope

 The results of a 5-year water-resources study of 

Mellette and Todd Counties are presented in this report. 

Specifically, this report includes descriptions of the 

quantity, quality, and availability of surface and ground 

water, the extent of the major shallow and bedrock 

aquifers, and surface- and ground-water uses in the two 

counties.
Introduction 3 Figure 1. Index map of South Dakota showing location of Mellette and Todd Counties, status of county investigations, and locations of main physiographic divisions (physiographic divisions modified from Flint, 1955; Fenneman, 1946).

104o 103o 102o 101o 100o 99o 98o 97o

45o

44o

43o

Black Hills Black Hills

Sand Hills Sand Hills

Central Central

Lowland Lowland

Great

Plains

HARDING HARDING

BUTTE

MEADE

LAWRENCE LAWRENCE

PENNINGTON PENNINGTON

CUSTER

FALL RIVER FALL RIVER SHANNON SHANNON

BENNETT BENNETT

TODD

MELLETTE MELLETTE

JACKSON JACKSON

HAAKON

ZIEBACH ZIEBACH

DEWEY

STANLEY STANLEY

JONES

LYMAN

TRIPP DOUGLAS DOUGLAS HUTCHINSON HUTCHINSON TURNER

BRULE AURORA DAVISON DAVISONHANSON MC COOK MC COOK MINNEHAHA MINNEHAHA

MOODY LAKE MINER SANBORN SANBORN JERAULD JERAULD BUFFALO BUFFALO

SULLY

HUGHES

HYDE HAND

BEADLE

KINGSBURY KINGSBURY BROOKINGS BROOKINGS

LINCOLN LINCOLN

UNION CLAY

YANKTON YANKTON BON HOMME

GREGORY GREGORY

CHARLES MIX CHARLES MIX

PERKINS PERKINS

CORSON

DEUEL

HAMLIN

CODINGTON CODINGTON

GRANT

CLARK SPINK

FAULK POTTER

WALWORTHWALWORTH

CAMPBELL CAMPBELL MC PHERSON MC PHERSON

EDMUNDS EDMUNDS

BROWN

MARSHALL MARSHALL

DAY

ROBERTS ROBERTS

Black Hills

Sand Hills

Central

Lowland

Great

Plains

HARDING

BUTTE

MEADE

LAWRENCE

PENNINGTON

CUSTER

FALL RIVER SHANNON

BENNETT

TODD

MELLETTE

JACKSON

HAAKON

ZIEBACH

DEWEY

STANLEY

JONES

LYMAN

TRIPP DOUGLAS HUTCHINSON TURNER

BRULE AURORA

DAVISON

HANSON

MC COOK MINNEHAHA

MOODY LAKE MINER SANBORN

JERAULD BUFFALO

SULLY

HUGHES

HYDE HAND

BEADLE

KINGSBURY BROOKINGS

LINCOLN

UNION CLAY

YANKTON BON HOMME

GREGORY

CHARLES MIX

PERKINS

CORSON

DEUEL

HAMLIN

CODINGTON

GRANT

CLARK

SPINK

FAULK POTTER

WALWORTH

CAMPBELL MC PHERSON

EDMUNDS

BROWN

MARSHALL

DAY

ROBERTS

0 20 40 600 20 40 60

MILES

KILOMETERS

EXPLANATION

STUDY AREAINVESTIGATION IN PROGRESSINVESTIGATION COMPLETED AND REPORTS PUBLISHEDINVESTIGATION NOT SCHEDULED

PHYSIOGRAPHIC DIVISION
4 Water Resources of Mellette and Todd Counties, South Dakota

Figure 2. Locations of selected wells, test holes, and lines of hydrogeologic section in Mellette and Todd Counties.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHITE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43o

45'

43o

30'

43o

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100o45' 100o30'

R. 26 W. R. 25 W.

100o15'

43o

00'

Sand

Creek

Crazy

Hole Cr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

83

18

18

83

63

63

44

44

53

BENNETT COUNTY JACKSON COUNTY

JONES COUNTY

LYMAN COUNTY TRIPP COUNTY

White

Lake

A A'

D'

C'

D

C

B

B'

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000

TEST HOLE OR OBSERVATION WELL--Aquifer description and driller's logs

 are available from the U.S. Geological Survey

LINE OF HYDROGEOLOGIC SECTION

ROSEBUD INDIAN RESERVATION

TEST HOLE OR WELL SITE (not drilled for this study)--Aquifer description and

 driller's logs are available from the U.S. Geological Survey

A A'

EXPLANATION
Introduction 5

Methods of Investigation

 Methods of investigation included analyses of 

streamflow records, a well inventory, analyses of preexisting drillers’ logs, test drilling and observationwell installation, measurement of static water levels, 

compilation of chemical analyses of surface- and 

ground-water samples, and analyses of water uses. 

Seventy-eight test holes were drilled; of these, 56 

observation wells were installed for the study. 

Although the drilling was concentrated in Mellette and 

Todd Counties, a few of the test holes and wells were 

drilled in Bennett County just outside the western 

boundary of Todd County, in Jones County just outside 

the northern boundary of Mellette County, and in Tripp 

County just outside the eastern boundary of Todd 

County. The locations of test holes and observation 

wells drilled specifically for this study and the locations of four lines of hydrogeologic section are shown 

in figure 2. The locations of additional test holes and 

private or public wells used to help determine the structure contours of the formations and the extent, thickness, yield, potentiometric surface, and water quality of 

the aquifers also are shown in figure 2. 

Many ground-water samples were collected and 

analyzed for this study. In 1990, 100 private domestic 

wells were sampled prior to the development of the 

water-resources investigation study. Between 1994 

and 1996, samples were collected from 47 of the 56 

observation wells installed for the study; between 1990 

and 1994, an additional 12 wells, which included 

private and observation wells, were sampled for a 

nitrate study conducted by the USGS in Todd County. 

The sampling methods, quality-assurance procedures, 

and water-quality analyses for these studies are presented by Carter (1997). Between 1991 and 1995, 

samples were collected from 21 wells, which included 

community, private, and observation wells, for an 

arsenic study conducted by the USGS in Todd County. 

The sampling methods, quality-assurance procedures, 

and water-quality analyses for the arsenic study are 

presented by Carter and others (1998).

All data collection sites are numbered according 

to the Federal land survey system of western South 

Dakota (fig. 3). The local number consists of the township number followed by “N,” range number followed 

by “W,” and section number, followed by a maximum 

of four uppercase letters that indicate, respectively, the 

160-, 40-, 10-, and 2.5-acre tract in which the well is 

located. These letters are assigned in a counterclockwise direction beginning with “A” in the northeast 

quarter. A serial number following the last letter is 

used to distinguish between wells in the same 2.5-acre 

tract. Thus, well 38N28W36ABCB is in the NW1

/4 of 

the SW1

/4 of the NW1/4 of the NE1/4 of section 36 in 

township 38 north and range 28 west.

Generalized Geology

As a result of different depositional environments in the past in western South Dakota, the geology 

in the study area consists mostly of marine, fluvial, and 

unconsolidated deposits ranging in age from the 

Precambrian to the present (table 1). In this report, 

descriptions of the geology is limited to deposits in 

Mellette and Todd Counties. Granitic rocks of Precambrian age dating to about 1,460 million years before 

present are located in a narrow strip across the southern 

edge of the study area (Richard Hammond, South 

Dakota Geological Survey, written commun., 1998); 

however, the rocks are not exposed at the surface. A 

geologic map showing the surficial deposits for 

Mellette and Todd Counties is shown in figure 4. 

Surficial deposits range from sedimentary rocks of 

Cretaceous age to unconsolidated deposits of 

Quaternary age.

Sedimentary rock sequences of Paleozoic and 

Mesozoic age were deposited by alternating transgressive and regressive seas. In the two counties, these 

rocks are composed mainly of limestone, dolomite, 

siltstone, sandstone, and shale. Rocks of Cambrian, 

Silurian, Devonian, Triassic, and Jurassic age are 

missing in the study area. The Red River and Winnipeg 

Formations, the Madison Limestone, and Minnelusa 

Formation are examples of transgressive seas. The 

study area was covered by seas from the Mississippian 

through the early Permian periods. From the late Permian period through the beginning of the Cretaceous 

period, deposits primarily were continental. Continental deposits are formed on land rather than in the sea 

and may include sediments of lake, swamp, wind, 

stream, or volcanic origin. Deposition and erosion of 

continental deposits prevailed throughout this time 

until another marine transgression occurred during the 

early Cretaceous period. Deposits during the Cretaceous period primarily were shale (Darton, 1905). 

Tertiary rocks generally consist of poorly consolidated 

claystones, siltstones, sandstones, and shale deposited 

in fluvial (stream/river) and lacustrine (lake) environments. Unconsolidated deposits of Quaternary age 

include terrace gravels, graded fluvial sand and gravels 

(alluvium), and eolian (windblown) sand. Glaciation 

during the Quaternary period did not affect the study 

area (Flint, 1955).
6 Water Resources of Mellette and Todd Counties, South Dakota Table 1. Generalized stratigraphic column showing geologic units and some of their characteristics Era System Formation or deposit Thickness (feet)1 Description and origin2 Remarks2

Cenozoic

Quaternary

Alluvium 0-35 Brown, varies between clay, silts, fine to coarse sand, and 

gravel. Generally sandy along the Little White River and other streams that flow over deposits of Tertiary age. Generally clayey with some thin sand beds along intermittent streams that flow over the Pierre Shale. Fluvial.

Locally, deposits are moderately permeable along the Little 

White River and relatively impermeable along streams that 

flow over the Pierre Shale. Yields generally are adequate to supply domestic and stock wells except along streams that flow over the Pierre Shale. Water is fresh, low in concentrations of dissolved solids, and soft to moderately hard except in deposits underlain by the Pierre Shale.

Windblown sand 

deposits

0-150 Brown, unconsolidated, very fine to medium grained, 

uniform, quartz sand; characterized by dune topography and blowouts. Eolian.

Generally very permeable and water bearing; yields are 

adequate to supply stock and domestic wells except where deposits are small.

Terrace deposits 0-105 Brown, silty clay, sand, and gravel. Commonly, the silty and 

sandy layers are partly cemented, and the gravel and sand beds commonly are interbedded with laminated silty clay. Fluvial.

Generally water bearing in the basal portion of the deposits. 

Yields are usually adequate to supply stock and domestic wells. Water is fresh, low in concentrations of dissolved solids, and soft to moderately hard except in areas where the water-bearing deposits are underlain by the Pierre Shale.

Tertiary

Ogallala Formation 0-240 Tan to olive, fine- to medium-grained sandstone with some 

silty clay. Upper unit of Ogallala Formation also is known as the Ash Hollow Formation and the lower unit as the Valentine Formation. Fluvial.

Permeable and generally water-bearing; yields are adequate 

to supply stock and domestic wells and can supply irrigation wells in some areas. Water is fresh, low in concentrations of dissolved solids, and soft to moderately hard.

Arikaree Formation 0-620 Pinkish tan to red; consists of poorly consolidated, tuffaceous 

sandstone, siltstone, shale, and silty clay. The Rosebud Formation sometimes is differentiated as a unit within the Arikaree Formation. Basal unit is composed mostly of silts and sands. Fluvial.

The upper part of the formation generally is impermeable, but 

can yield small amounts of water from fractures, joints, and silty layers. The basal part is moderately permeable and can supply water for domestic and stock wells. Water is fresh, low in concentrations of dissolved solids, and soft to moderately hard.

White River Group 

(undifferentiated)

0-470 Yellow to brown, poorly consolidated siltstone and claystone 

with some beds of fine-grained sand. Units of the White River Group sometimes are differentiated into the Brule and Chadron Formations. Fluvial.

Permeability varies from impermeable to moderately 

permeable, depending on the clay content. Yields are usually adequate to supply water to stock and domestic 

wells. Water is slightly saline, moderate in concentrations of dissolved solids, and hard depending on the proximity of the aquifer to the Pierre Shale.

Mesozoic

Cretaceous

Pierre Shale 600-1,3953 Bluish-black shale with some layers of bentonite. Marine. Most of the formation is relatively impermeable. Can yield 

small amounts of water if fractures or sandy zones are present. Typically not considered an aquifer. Water is saline, high in concentrations of dissolved solids, and very hard.

Niobrara Formation 125-1754 Tan to gray, highly calcareous shale. Commonly described 

by drillers as “chalk.” Marine.

Water-bearing traits are largely unknown. May yield 

sufficient water for some purposes.
Introduction 7

1Based on interpretation and projection of data from electric logs and drillers’ logs. 2Based on interpretation of data collected during study and from drillers’ logs. 3From Ellis and others (1972).4From Ellis and others (1971).5Mesozoic

From Agnew and Tychsen (1965).

Cretaceous

Carlile Shale 300-4004 Light grayish blue to black, noncalcareous shale. Marine. Nearly impermeable. Water-bearing traits are largely 

unknown.

Greenhorn Formation 100-1204 Tan, bluish, white, or gray calcareous shale. Marine. Water-bearing traits are largely unknown.Graneros Shale 130-2004 Dark-gray non-calcareous shale. Marine. Nearly impermeable. Water-bearing traits are largely 

unknown.

Dakota Formation 

(Dakota Sandstone)

270-3404 Interbedded tan to white sandstone and dark-colored shale. 

Sandstone is composed of loose to well-cemented, very fine to coarse quartz sand; cement most commonly is calcium carbonate. Marine.

Permeable sandstone beds yield moderate quantities of water 

under artesian pressure for stock and domestic wells. The water is highly mineralized and cannot be used for irrigation purposes.

Skull Creek Shale 95-1504 Dark bluish-gray shale. Marine. Relatively impermeable. Water-bearing traits are largely 

unknown.

Inyan Kara Group 

undifferentiated

100-2754 White to light-gray or tan sandstone and siltstone; contains 

beds of gray to black and reddish to buff shale. The Inyan Kara Group sometimes is divided into the Fall River and Lakota Formations. Continental to marginal marine.

Permeable sandstone beds yield moderate quantities of water 

under artesian pressure for stock and domestic wells. The water is highly mineralized and cannot be used for irrigation purposes.

Paleozoic

Permian and

PennsylvanianMinnelusa Formation 300-5304 Consists of interbedded sandstone, siltstone, dolomite, limestone, anhydrite, and shale. Marine. Permeable zones can yield adequate water for stock and domestic wells under artesian pressure. Water is lower in dissolved solids than the Dakota Sandstone and Inyan Kara aquifers. Can be used for irrigation on crops that are tolerant of salt with proper salinity management.

MississippianMadison Formation 90-2404 Light gray to buff, varies from pure limestone to pure dolomite with various combinations of the two. Marine. Permeable zones can yield adequate water for stock and domestic wells under artesian pressure. Water is lower in dissolved solids than the Dakota Sandstone and Inyan Kara aquifers. Can be used for irrigation on crops that are tolerant of salt with proper salinity management. Ordovician Red River and Winnipeg Formations (undifferentiated) 0-1704 The Red River Formation mostly consists of dolomite, and the Winnipeg Formation mostly consists of sandstones5. Marine.

Precambrian Granite.
8 Water Resources of Mellette and Todd Counties, South Dakota

Figure 3. Well-numbering system. The well number consists of the township number, followed by “N,” the range number 

followed by “W,” and the section number followed by a maximum of four uppercase letters that indicate, respectively, the 

160-, 40-, 10-, and 2 1/2-acre tract in which the well is located. These letters are assigned in a counterclockwise direction 

beginning with “A” in the northeast quarter. A serial number following the last letter is used to distinguish between wells 

in the same 2 1/2-acre tract.

36

A B

C D

A B

C

D

C

A

B

C D

D

A

B

1

2

3

4

5

6

12

11

10

9

8

7

13

14

15

16

17

24

23

22

21

20

19

25

26

27

28

29

30

18

35

34

33

32

31

R. 28 W.

T. 38 N.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

T. 36 N.

T. 37 N.

T. 38 N.

T. 39 N.

T. 40 N.

T. 41 N.

T. 42 N.

T. 43 N.

T. 44 N.

T. 45 N.

T. 35 N.

R. 31 W.

R. 32 W.

R. 33 W.

R. 27 W. R. 28 W.

R. 29 W.

R. 30 W.

R. 25 W.

R. 26 W.

Well

38N28W36ABCB
Introduction 9

Figure 4. Generalized geologic map showing surficial geology of study area (modified from Ellis and others, 1971).

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHITE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43o

45'

43o

30'

43o

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100o45' 100o30'

R. 26 W. R. 25 W.

100o15'

43o

00'

White

Lake

Sand

Creek

Crazy

HoleCr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

BENNETT COUNTY JACKSON COUNTY

JONES COUNTY

LYMAN COUNTY TRIPP COUNTY

83

18

18

83

63

63

44

44

53

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000

Alluvium

QUATERNARY UNCONSOLIDATED 

 DEPOSITS

TERTIARY SEDIMENTARY

 DEPOSITS

CRETACEOUS SEDIMENTARY

 DEPOSITS

Windblown sand deposits

Pierre Shale

White River Group

Ogallala Formation

EXPLANATION

Qa

Qa

Qa

Qa

Qa

Qa

Qa

Qwd

Qwd

Qwd

To

To

To

To

To

To

Ta

Ta

Ta

Tw

Tw

Tw

Tw

Kp

Kp

Kp

Kp

Tw

Tw

Ta

Ta Arikaree Formation

Tw

Kp
10 Water Resources of Mellette and Todd Counties, South Dakota

Known water-bearing bedrock formations in the 

study area include the Madison Limestone of 

Mississippian age, the Minnelusa Formation of Pennsylvanian and Permian age, and the Inyan Kara Group, 

Dakota Sandstone, and Pierre Shale of Cretaceous age 

(table 1). The youngest bedrock formation, the Pierre 

Shale, is exposed at land surface throughout most of 

Mellette County. The bedrock surface is the boundary 

between the bedrock formations and the overlying 

poorly consolidated Tertiary formations and surficial 

deposits. The Tertiary deposits in the study area are 

exposed at land surface (fig. 4), except where covered 

by unconsolidated deposits or where missing. The 

Tertiary deposits in the study area, from oldest to 

youngest, are the White River Group of Eocene and 

Oligocene age, the Arikaree Formation of Miocene 

age, and the Ogallala Formation of Pliocene age. A 

generalized map showing the unconsolidated deposits 

and outcrops of the Tertiary formations and Pierre 

Shale is shown in figure 4. Structure contour maps, 

which show the altitude of the tops of the formations, 

were constructed based on driller’s logs and data 

collected during this study for the Pierre Shale (fig. 5), 

the White River Group (fig. 6), and the Arikaree 

Formation (fig. 7). Unconsolidated deposits of 

Quaternary age within the study area consist of alluvial, 

terrace, and windblown sand deposits.

Acknowledgments

Many people have assisted with the development 

and implementation of the study. In particular, Syed 

Huq, Charles Mack, and John Whiting of the Office of 

Water Resources of the Rosebud Sioux Tribe and Sena 

Lauritsen of the Mellette/Todd Water Resources 

Coordination Project provided valuable assistance with 

the collection of water-quality samples and other 

hydrologic data. The South Dakota Geological Survey 

drilled the test holes and installed the observation wells 

for the study. Dick Hammond and Patricia Hammond 

of the South Dakota Geological Survey provided 

valuable insight and technical guidance for the study. 

Appreciation is expressed to the Mellette County 

officials and the West River Water Development 

District personnel for their cooperation during this 

study. The cooperation of residents of Mellette and 

Todd Counties for providing information concerning 

their private wells is appreciated.

WATER RESOURCES

Precipitation

The average precipitation at Wood in Mellette 

County and at a precipitation station located 14 miles 

south of Mission in Todd County from 1961-90 was 

18.96 inches and 19.32 inches, respectively (U.S. 

Department of Commerce, 1994). The total annual 

volume of water from precipitation in Mellette and 

Todd Counties is about 2,751,000 acre-feet. About 

8 percent of the average annual precipitation becomes 

streamflow (230,000 acre-feet); however, this quantity 

varies from year to year and month to month because of 

climatic conditions.

Surface Water

The surface-water resources in Mellette and 

Todd Counties include rivers, streams, and lakes. The 

major rivers are the White River, Little White River, 

and Keya Paha River. Some of the smaller streams 

include Blackpipe Creek, Antelope Creek, and 

Rosebud Creek. Two of the largest lakes in the study 

area are Antelope Lake (an artificial lake) and White 

Lake, which are located in Todd County.

Drainage Basins

The major drainage basins within the study area 

are the White River Basin and the Niobrara River Basin 

(fig. 8). The White River and Niobrara River, in 

Nebraska, flow easterly into the Missouri River. All of 

Mellette County and about 51 percent of Todd County 

is drained by the White River and its tributaries 

(1,306 square miles in Mellette County and about 

710 square miles in Todd County). About 49 percent 

of Todd County is drained by tributaries of the Niobrara 

River (about 680 square miles), which include the Keya 

Paha River.

Streams

Four streamflow-gaging stations are located 

within the study area (fig. 8) and five gaging stations 

are located in adjacent counties. A summary of streamflow-gaging records for sites in and near Mellette and 

Todd Counties is presented in table 2.
Water Resources 11

Figure 5. Structure contour map for the top of the Pierre Shale.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHTE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43¡

45'

43¡

30'

43o

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100o45' 100¡30'

R. 26 W. R. 25 W.

100o15'

43o

00'

Sand

Creek

Crazy

Hole Cr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

83

18

18

83

63

63

44

44

53

BENNETTE COUNTY JACKSON COUTNY

JONES COUNTY

LYMAN COUNTY TRIPP COUTNY

White

Lake

2000

2000

2200

2200

2250

2250

2300

1950

1850

1900

1900

1950

2050

2050

2150

2150

2350

2300

2250

2200

2150

2100 2050

2000

1950

2100

2100

2350

2283

2181

2363

2157

2221

2283

2272

2233

2340

2294

2146

2250

2242

2168

2184

2198

2181

2199

2253

2247

2038

1975 1975

1974

2042

2115

1933

2051 2050

1969

1919

1963

1933

1858

1869

1876

1832

1903

1940

2034

1846

1933

2363

2196 1979

1986

2283

2157

2160

2264

2221

2264

2287

1947

2006

2276

2394

2355

2276 2153

2072

2053

2078

2110

2284

2297

2184

2283

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000 EXPLANATION

APPROXIMATE AREA UNDERLAIN BY THE PIERRE SHALE (modified from

 Ellis and others, 1971)

STRUCTURE CONTOUR--Shows altitude of top of the Pierre Shale. Dashed

 where inferred. Contour interval 50 feet. Datum is sea level.

WELL OR TEST HOLE THAT PENETRATED PIERRE SHALE--Number is

 altitude of the top of the Pierre Shale, in feet above sea level

APPROXIMATE AREA OF PIERRE SHALE EXPOSED AT LAND SURFACE

 (modified from Ellis and others, 1971)

1940

2300
12 Water Resources of Mellette and Todd Counties, South Dakota

Figure 6. Structure contour map for the top of the White River Group.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHTE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43¡

45'

43o

30'

43o

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100¡45' 100o30'

R. 26 W. R. 25 W.

100o15'

43o

00'

Sand

Creek

Crazy

Hole Cr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

83

18

18

83

63

63

44

44

53

BENNETTE COUNTY JACKSON COUTNY

JONES COUNTY

LYMAN COUNTY TRIPP COUTNY

White

Lake

2400

2450

2500

2550

2550

2600

2350

2350

2400

2500

2450

2350

2400

2400

2450

2450

2550

2500

25002450

2300

2250

2200

2200

2200

2250

2250 2250

2300

2300

2250

2350

2300

2350 2400

23502300

2450

2400

2250

2200

2200

2300

23002350

2150

2400

2450

2443

2417

2306

2395

2448

2425

2492

2450 2447

2462

2488

2475 2560 2553

2550

2530

2648

2552

2565

2570 2565

2500

2495

2500

2493

2359

2490

2424 2537

2430

2305

2351

2320

2425

2405 2450

2340 2345 2365

2338 2533

2358

2420

2404

2417

2465

2409

2422 

2340

2365

2298

2457

2400

2447

2435

2203

2435

2495

2440

2537

2569

2440

2332

2500

2362

2498

2440

2510

2378

2376

2504

2555 2484

2339

2224

2446

2281

2384

2384

2228

2228

2203

2252 2219

2279

2231

2327

2256

2247 2307 2281

2277 2120

2405

2265

2119

2345

2213

2209

2210

2236

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000 EXPLANATION

APPROXIMATE AREA UNDERLAIN BY THE WHITE RIVER GROUP (modified from

 Ellis and others, 1971)

STRUCTURE CONTOUR--Shows altitude of top of the White River Group. Dashed

 where inferred. Contour interval 50 feet. Datum is sea level.

WELL OR TEST HOLE THAT PENETRATED WHITE RIVER GROUP--Number is

 altitude of the top of the White River Group, in feet above sea level

APPROXIMATE AREA OF WHITE RIVER GROUP EXPOSED AT LAND SURFACE

 (modified from Ellis and others, 1971)

2265

2500
Water Resources 13

Figure 7. Structure contour map for the top of the Arikaree Formation.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHTE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43o

45'

43o

30'

43¡

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100o45' 100o30'

R. 26 W. R. 25 W.

100o15'

43o

00'

Sand

Creek

Crazy

Hole Cr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

83

18

18

83

63

63

44

44

53

BENNETTE COUNTY JACKSON COUTNY

JONES COUNTY

LYMAN COUNTY TRIPP COUTNY

White

Lake

2700

2700

2750

2750

2800

2850

2900

2950

3000

2950

3050

3100

2700

2700

2700

2700

2700

2800

2750

2750

2650

2650

2650

2650

2550

2600

2600

2750

2650 2750

2750

2800

2600

2600

2650

2650

2650

2450

2500

2500 2550

2600

2550

25002450

2450

2400

2670

2620

2790

2660

2700 2695

2647

2805

2615

2636

2626

2670

2585

2660

2652

2632

2570

2560

2640

2675

2680

2770

2930

2770

2790

2805

2701

2670

2702

2710 2670 2590

2660

2645

27432700 2695 2620

2615

2636

2626

2515

2569

2641

2610

2660

2684

2646 2650

2641

2672

2609

2535

2532

2610

2628

2623 2670

2601

2637

2586 2619

2683 2724

2524

2610

2680

2530

2570

2485

2502

2520

2520

2493

2468

2614

2691

2750

2949

2765

2800

2719

27102756

2765 2770

2735

2755

2647 2695

2685

2732

2722 2770

2632

2632

2638 2655

2602

2613

2646

2640

2656 2601

2595

2740

2660

2603

2549

2570

2665 2645 2585

2520 2608

2600

2610

2654 2505

2655

2529 2560

2437

2500

2486

2390

2401

2448 2432

2480 2449

2413

2638 2619

2581

2508

2651

2547

2809

2795

2700

2737

2681

2660

2677

2652

2629

2628

2621

2694

2713 2783

2693

2694

2572

2500

2496

2364

2717

2769

2756

2865 2770

2765

2735

2805

2546

2658

2652

2588

2672

2673

2632

2531

2454

2542

2575

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000 EXPLANATION

APPROXIMATE AREA UNDERLAIN BY THE ARIKAREE FORMATION (modified

 from Ellis and others, 1971)

STRUCTURE CONTOUR--Shows altitude of top of the Arikaree Formation. Dashed

 where inferred. Contour interval 50 feet. Datum is sea level.

WELL OR TEST HOLE THAT PENETRATED ARIKAREE FORMATION--Number is

 altitude of the top of the Arikaree Formation, in feet above sea level

APPROXIMATE AREA OF ARIKAREE FORMATION EXPOSED AT LAND SURFACE

 (modified from Ellis and others, 1971)

2770

2700
14 Water Resources of Mellette and Todd Counties, South Dakota

Figure 8. Locations of drainage basins and U.S. Geological Survey streamflow-gaging stations in Mellette and Todd 

Counties.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHITE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43o

45'

43o

30'

43o

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100o45' 100o30'

R. 26 W. R. 25 W.

100o15'

43o

00'

Sand

Creek

Crazy

Hole Cr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

83

18

18

83

63

63

44

44

53

BENNETT COUNTY JACKSON COUNTY

JONES COUNTY

LYMAN COUNTY TRIPP COUTNY

White

Lake

NIOBRARA RIVER BASIN NIOBRARA RIVER BASIN

WHITE RIVER BASIN WHITE RIVER BASIN

Middle White River Basin Middle White River Basin

Little White River Basin Little White River Basin

Lower White River Basin Lower White River Basin

Middle Niobrara River Basin Middle Niobrara River Basin

Keya Paha River Basin Keya Paha River Basin

06449400

06449300

06449500

06450500

WHITE RIVER BASIN

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000

NIOBRARA RIVER BASIN

Middle White River Basin

Little White River Basin

Lower White River Basin

Middle Niobrara River Basin

Keya Paha River Basin

DRAINAGE BASIN

DRAINAGE SUBBASIN

STREAMFLOW-GAGING STATION--

 Number is station identification

EXPLANATION

O6449400
Surface Water 15

1Outside study area.

Table 2. Summary of data for streamflow-gaging stations in and near Mellette and Todd Counties

Station

number Station name

 Drainage 

area 

(square 

miles)

Noncontributing 

drainage 

area 

(square 

miles)

Period of 

record used 

(water year)

Streamflow

(cubic feet per second)

Extreme flow Annual flow

Maximum 

instantaneous Minimum daily Average 25th percentile Median 50th percentile 75th percentile

106447230 Blackpipe Creek near Belvidere 250 0 1993-95 3,500 0.00 31.8 15.0 19.9 60.5106447500 Little White River near Martin 310 80 1939,

1963-95

1,190 0.60 20.1 15.6 18.8 22.5

106449100 Little White River near Vetal 590 175 1960-95 3,540 9.0 55.7 45.8 56.3 65.0

06449300 Little White River above Rosebud 890 260 1982-95 2,190 20 110 94 111 12406449400 Rosebud Creek at Rosebud 50.8 0 1975-95 670 .00 7.54 6.98 7.44 8.1006449500 Little White River near Rosebud 1,020 260 1944-95 4,640 10 113 99 116 12506450500 Little White River below White River 1,570 260 1950-95 13,700 7.0 131 100 128 149

106464100 Keya Paha River near Keyapaha 466 0 1982-95 852 2.4 39.1 25.0 40.0 49.4106464500 Keya Paha River at Wewela 1,070 0 1939-95 5,430 .00 73.4 47.5 59.0 99.0
16 Water Resources of Mellette and Todd Counties, South Dakota

The average flow of the Little White River is 

about 56 cubic feet per second as the river enters Todd 

County near Vetal (station 06449100). The average 

flow of the Little White River is about 131 cubic feet 

per second as it discharges to the White River in 

northern Mellette County based on the average discharge of the most downstream gaging station (station 

06450500). The Keya Paha River near Keyapaha 

(station 06464100) has an average flow of about 

39 cubic feet per second.

The average annual runoff for the nine gaging 

stations ranges from 0.94 to 2.36 inches and averages 

1.62 inches. The average annual runoff for the Little 

White River for the period of record is 1.18 inches 

(63 acre-feet per square mile) near Martin, 1.82 inches 

(97 acre-feet per square mile) near Vetal, 2.36 inches 

(126 acre-feet per square mile) above Rosebud, 

2.03 inches (108 acre-feet per square mile) near 

Rosebud, and 1.37 inches (73 acre-feet per square 

mile) below White River. For Rosebud Creek, which is 

a tributary to the Little White River, the average annual 

runoff at Rosebud for the period of record is 

2.03 inches (108 acre-feet per square mile). The 

average annual runoff for the period of record for the 

Keya Paha River near Keyapaha is 1.14 inches 

(61 acre-feet per square mile) and for the Keya Paha 

River at Wewela is 0.94 inches (50 acre-feet per square 

mile). The average annual runoff for Blackpipe Creek 

near Belvidere is 1.73 inches (92 acre-feet per square 

mile).

Streamflow is directly affected by precipitation 

and evapotranspiration. Streams generally receive 

more than one-half of their flow from discharge from 

the aquifers, especially during the winter months, when 

the stage in the streams often is lower than the hydraulic heads in the aquifers. Numerous ephemeral springs 

occur along the Little White River. 

Flow Duration

Daily-duration hydrographs for the indicated 

percentage of time daily mean streamflow is exceeded 

for the Little White River below White River (station 

06450500) in Mellette County is shown in figure 9. 

The duration hydrographs show the maximum and 

minimum daily flows and the 20-, 50-, and 80-percent 

exceedance values for the period 1957-95. Streamflow 

for the indicated hydrographs can be expected to be 

equaled or exceeded 20, 50, and 80 percent of the time, 

respectively, on any individual day. For example, on 

April 1, a flow equal to or exceeding 113 cubic feet per 

second can be expected 80 percent of the time, a discharge equal to or exceeding 186 cubic feet per second 

can be expected 50 percent of the time, and a flow 

equal to or exceeding 249 cubic feet per second can be 

expected 20 percent of the time. Flows are highest 

during late winter and spring when runoff of snowmelt 

and rainfall are greatest. Streamflow gradually 

decreases during late spring and summer due to 

increasing evapotranspiration and decreasing precipitation. Flows are lowest from fall to mid-winter. There 

are no days when the flow was less than 10 cubic feet 

per second for the 39-year period shown.

Because there are no gaging stations within the 

study area on the Keya Paha River, daily-duration 

hydrographs for the indicated percentage of time daily 

mean streamflow is exceeded is shown in figure 10 for 

the Keya Paha River at Wewela (station 06464500) in 

southwest Tripp County. The period of record used to 

construct the duration hydrographs is 1957-95. Flows 

of the Keya Paha River are highest during late winter 

and spring and lowest from fall to mid-winter. 

Although a flow equal to or exceeding 10 cubic feet per 

second can be expected 80 percent of the time on any 

individual day, there are several days during some years 

when there was no flow at the Keya Paha River at 

Wewela station. 

Flood Information

 Flooding from snowmelt and rainfall during the 

spring is common along the White River and parts of 

the Little White River because of numerous ice jams. 

Flood-stage data are not available in Mellette and Todd 

Counties, but data are available for two gaging stations 

located on the White River outside the study area. At 

the gaging station located near Kadoka in Jackson 

County, flood stage of the White River is 13 feet 

(Tresté Huse, National Weather Service, Rapid City, 

S. Dak., written commun., 1997). Flood stage of the 

White River near Oacoma in Lyman County is 15 feet 

(Tresté Huse, National Weather Service, Rapid City, 

S. Dak., written commun., 1997). Maps of flood prone 

areas along the White River in Mellette County, at a 

scale of about 2.64 inches to the mile, can be obtained 

from the USGS District office in Rapid City, South 

Dakota.
Surface Water 17

Figure 9. Daily-duration hydrographs for indicated percentage of time flow of the Little White River below White River 

(station 06450500) in Mellette County was equal to or greater than that shown, water years 1957-95.

Figure 10. Daily-duration hydrographs for indicated percentage of time flow of the Keya Paha River at Wewela 

(station 06464500) in Tripp County was equal to or greater than that shown, water years 1957-95.

10

10,000

100

1,000

Maximum

20 Percent

50 Percent

Minimum

80 Percent

OCT NOV DEC JAN FEB MAR MAY JUN APR JUL AUG SEP

FLOW, IN CUBIC FEET PER SECOND

Maximum

20 Percent

50 Percent

Minimum

80 Percent

1

10

10,000

1,000

100

OCT NOV DEC JAN FEB MAR MAY JUN APR JUL AUG SEP

FLOW, IN CUBIC FEET PER SECOND
18 Water Resources of Mellette and Todd Counties, South Dakota

Lakes

Few natural lakes exist within the study area. 

Although many manmade lakes exist in the study area, 

most generally occupy less than 10 acres and are used 

for stock-watering purposes. White Lake, located in 

south-central Todd County near the South DakotaNebraska border (fig. 8), is the largest natural lake in 

the study area with a surface area of about 160 acres 

and an average elevation of 2,783 feet above sea level. 

Antelope Lake, an artificial lake located near Antelope 

in north-central Todd County (fig. 8), has a surface area 

of about 95 acres and an average elevation of 2,521 feet 

above sea level. Other lakes within the study area have 

a surface area of less than 50 acres.

Water Quality

 Water-quality data are available in the USGS 

NWIS water-quality database for several stream sites 

located in Mellette and Todd Counties. Because little 

water-quality data are available for the lakes in the 

study area, this section discusses only the water-quality 

data from streams. 

A summary of chemical analyses is shown in 

table 3 for the Little White River at the gaging stations 

above Rosebud (station 06449300) and below White 

River (station 06450500). The dominant chemical 

species in water are calcium and bicarbonate at the site 

above Rosebud and calcium, bicarbonate, and sulfate at 

the site below White River (fig. 11). 

Specific conductance, a measure of total dissolved solids (TDS), data also are available for two 

streams that have gaging stations within 10 miles of the 

study area. The mean specific conductance was 

760 μS/cm (microsiemens per centimeter at 25° 

Celsius) for 31 samples collected between 1992-95 on 

Blackpipe Creek near Belvidere (station 06447230), 

and 447 μS/cm for 144 samples collected between 

1981-95 on the Keya Paha River near Keyapaha 

(station 06464100).

Most water-quality constituents and properties in 

streams vary with the volume of streamflow. For 

example, specific conductance shows a typical seasonal 

pattern due to variations in streamflow at Little White 

River above Rosebud (station 06449300) for the period 

of October 1981 through August 1995 (fig. 12). Conductance values are lowest in February and March, 

during the high flows of spring snowmelt, which causes 

dilution of TDS. The highest conductance values occur 

in November-January and are the result of low-flow 

and ice conditions. Conductance at this site ranged 

from 219 μS/cm on March 9, 1994, when the daily 

mean discharge was 684 cubic feet per second to 

580 μS/cm on November 18, 1991, when the daily 

mean discharge was 111 cubic feet per second. 

Specific conductance at the site Little White River 

below White River (06450500) (not included in fig. 12) 

ranged from 210 μS/cm when the mean daily discharge 

was 2,000 cubic feet per second to 1,350 μS/cm when 

the mean daily discharge was 116 cubic feet per 

second. This cyclic pattern occurs at other sites along 

the Little White River and is similar to patterns shown 

by other water-quality constituents.

In addition to seasonal variability, specific conductance values varied between the sites located on the 

Little White River in Mellette and Todd Counties. 

Generally, specific conductance increases from 

upstream to downstream. For example, specific conductance increases from station 06449300 above 

Rosebud to station 06450500 below White River 

(fig. 13); the mean conductance was 312 μS/cm above 

Rosebud, 346 μS/cm at Rosebud Creek, 327 μS/cm 

near Rosebud, and 386 μS/cm below White River. The 

increase in conductance probably is at least partly 

attributed to the underlying geology. Three upstream 

sites overlie either the Arikaree or Ogallala Formations, 

which generally supply lower TDS; the downstream 

site overlies the Pierre Shale, which generally supplies 

higher TDS.

Ground Water

The shallow aquifers in the study area are the 

alluvial, Ogallala, Arikaree, and White River aquifers. 

The bedrock aquifers are the Pierre Shale, Dakota 

Sandstone, Inyan Kara, and Minnelusa and Madison 

aquifers. 

In Todd County, ground water generally can be 

obtained from shallow wells (less than 300 feet) completed either in alluvial deposits or in deposits of 

Tertiary age (Ogallala Formation, Arikaree Formation, 

or White River Group). Ground water is more difficult 

to obtain in Mellette County because the Pierre Shale is 

exposed throughout much of the county (fig. 4), which 

means that the younger Tertiary deposits have been 

eroded and are not present in these areas. Water is 

difficult to obtain from the Pierre Shale, plus concentrations of dissolved solids are high and water is hard, 

thus deep wells (greater than 1,000 feet) are sometimes 

drilled in Mellette County to obtain ground water.
Surface Water 19

Table 3. Summary of chemical analyses for the Little White River at gaging stations above Rosebud and below White River, 

1950-95

[Results based on data stored in USGS NWIS water-quality database. Results in milligrams per liter except as indicated. One milligram 

per liter (mg/L) is approximately equal to one part per million. One microgram per liter (μg/L) is equal to one part per billion; μS/cm, 

microsiemens per centimeter at 25° Celsius; --, not analyzed or not determined; <, less than indicated detection limit; ND, specifically analyzed for but not detected, and detection limit unknown]

Property or

dissolved constituent

06449300 Little White River above Rosebud (1981-95)

Number of

samples Mean Median Minimum Maximum

Specific conductance (μS/cm) 157 312 305 219 580

pH (standard units) 111 8.0 8.1 7.1 9.4

Hardness, as CaCO3 60 113 114 66 134

Solids, residue at 180° C 61 234 232 151 292

Solids, sum of constituents 57 202 192 114 269

Calcium 60 36 37 21 43

Magnesium 62 6 6 3 8

Sodium 62 22 21 10 31

Potassium 62 10 9 6 14

Bicarbonate 1 167 167 167 167

Alkalinity 105 149 147 65 195

Sulfate 61 16 15 6 30

Chloride 62 4 3.2 0.8 17.0

Fluoride 27 0.5 0.5 0.3 0.7

Silica 23 49 49 38 56

Nitrogen, nitrate 22 0.6 0.5 0.1 1.6

Nitrite plus nitrate 61 0.6 0.5 <0.1 1.6

Phosphorus, orthophosphate 59 0.18 0.18 0.02 0.47

Aluminum (μg/L) 33 138 90 20 1,500

Arsenic (μg/L) 60 8 8 5 13

Barium (μg/L) 51 89 100 <2 180

Boron (μg/L) 57 45 40 30 80

Cadmium (μg/L) 60 <10 <10 <10 <10

Chromium (μg/L) 19 <1 <1 <1 1

Cobalt (μg/L) 16 <3 <3 <3 <3

Copper (μg/L) 62 4 3 <1 29

Iron (μg/L) 62 90 35 5 1,100

Lead (μg/L) 59 1 <1 <1 20

Lithium (μg/L) 33 21 19 <4 50

Manganese (μg/L) 62 7 5 1 48

Mercury (μg/L) 59 <0.1 <0.1 <0.1 3.8

Molybdenum (μg/L) 1 2 2 2 2

Nickel (μg/L) 18 1 <1 <1 5

Selenium (μg/L) 109 <1 <1 <1 1

Silver (μg/L) 19 <1 <1 <1 <1

Strontium (μg/L) 33 202 210 <0.5 250

Vanadium (μg/L) 1 9 9 9 9

Zinc (μg/L) 95 14 8 <3 150
20 Water Resources of Mellette and Todd Counties, South Dakota

Table 3. Summary of chemical analyses for the Little White River, 1950-95—Continued

Property or

dissolved constituent

06450500 Little White River below White River (1950-95)

Number of

samples Mean Median Minimum Maximum

Specific conductance (μS/cm) 321 386 360 210 1350

pH (standard units) 147 7.7 7.8 7.0 8.9

Hardness, as CaCO3 147 143 129 102 435

Solids, residue at 180° C 132 305 283 220 948

Solids, sum of constituents 92 283 258 174 915

Calcium 143 47 42 34 141

Magnesium 143 6 6 2 26

Sodium 147 30 27 18 109

Potassium 94 10 9 6 15

Bicarbonate 145 197 194 144 262

Alkalinity 0 -- -- -- --

Sulfate 144 46 28 14 445

Chloride 144 2 2 ND 9

Fluoride 75 0.5 0.4 0.2 1.1

Silica 79 51 53 5 84

Nitrogen, nitrate 0 -- -- -- --

Nitrite plus nitrate 0 -- -- -- --

Phosphorus, orthophosphate 0 -- -- -- --

Aluminum (μg/L) 0 -- -- -- --

Arsenic (μg/L) 47 ND ND ND ND

Barium (μg/L) 0 -- -- -- --

Boron μg/L) 94 93 80 30 290

Cadmium (μg/L) 47 ND ND ND ND

Chromium (μg/L) 0 -- -- -- --

Cobalt (μg/L) 47 ND ND ND ND

Copper (μg/L) 0 -- -- -- --

Iron, total (μg/L) 17 34 20 ND 190

Lead (μg/L) 47 ND ND ND ND

Lithium (μg/L) 0 -- -- -- --

Manganese, total (μg/L) 1 110 110 110 110

Mercury (μg/L) 0 -- -- -- --

Molybdenum (μg/L) 0 -- -- -- --

Nickel (μg/L) 0 -- -- -- --

Selenium (μg/L) 47 ND ND ND 80

Silver (μg/L) 0 -- -- -- --

Strontium (μg/L) 0 -- -- -- --

Vanadium (μg/L) 0 -- -- -- --

Zinc (μg/L) 0 -- -- -- --
Surface Water 21

Figure 11. Trilinear diagrams (Piper, 1944) showing proportional concentrations of major ions for the Little White River.

Calcium + Magnesium

Sulfate

Sodium + Potassium

Chloride + Fluoride + Nitrate + Sulfate

Bicarbonate + Carbonate

Magnesium

Calcium Chloride + Fluoride + Nitrate

80

60

40

20

80

80

60

40

20

20

20

40

60

80

40

60

80

60

40

20

20

80

60

40

20

40

60

80

80

60

40

20

LITTLE WHITE RIVER ABOVE ROSEBUD (station 06449300)

Calcium + Magnesium

Sulfate

Sodium + Potassium

Chloride + Fluoride + Nitrate + Sulfate

Bicarbonate + Carbonate

Magnesium

Calcium Chloride + Fluoride + Nitrate

80

60

40

20

80

80

60

40

20

20

20

40

60

80

40

60

80

60

40

20

20

80

60

40

20

40

60

80

80

60

40

20

LITTLE WHITE RIVER BELOW WHITE RIVER (station 06450500)
22 Water Resources of Mellette and Todd Counties, South Dakota

Figure 12. Monthly variations in specific conductance for the Little White River above Rosebud (station 06449300), 1981-95.

Figure 13. Variations in specific conductance at selected sites located on the Little White River, 1950-95.

OCT NOV DEC JAN FEB MAR MAY JUN APR JUL AUG SEP

SPECIFIC CONDUCTANCE,

IN MICROSIEMENS PER CENTIMETER

600

580

560

540

520

500

480

460

440

420

400

380

360

340

320

300

280

260

240

220

200

16 10 9 17 14 9 15 15 17 11 14 10

14

75th percentile concentration

Largest concentration within 1.5 interquartile ranges above

 the 75th percentile

Concentration within 1.5 to 3.0 interquartile ranges above

 the 75th percentile

Concentration within 1.5 to 3.0 interquartile ranges below

 the 25th percentile

Concentration greater than 3 interquartile ranges above

 the 75th percentile

Number of samples

Smallest concentration within 1.5 interquartile ranges below

 the 25th percentile

50th percentile concentration (median)

25th percentile concentration

SPECIFIC CONDUCTANCE,

IN MICROSIEMENS PER CENTIMETER

1,500

1,400

1,300

1,200

1,100

1,000

900

800

700

600

500

400

300

200

100

0

Station 06449300

(above Rosebud)

(1981-95)

Station 06449400

(Rosebud Creek)

(1974-95)

Station 06449500

(near Rosebud)

(1977-95)

Station 06450500

(below White River)

(1950-95)

157 216 176 321

157

75th percentile concentration

Largest concentration within 1.5 interquartile ranges above

 the 75th percentile

Concentration within 1.5 to 3.0 interquartile ranges above

 the 75th percentile

Concentration within 1.5 to 3.0 interquartile ranges below

 the 25th percentile

Concentration greater than 3 interquartile ranges above

 the 75th percentile

Concentration greater than 3 interquartile ranges below

 the 25th percentile

Number of samples

Smallest concentration within 1.5 interquartile ranges below

 the 25th percentile

50th percentile concentration (median)

25th percentile concentration
Ground Water 23

The boundaries of five aquifers were delineated 

for this study: the alluvial, Ogallala, Arikaree, White 

River, and Pierre Shale aquifers. Because little information is available regarding the deeper aquifers in the 

study area (including the Dakota Sandstone, Inyan 

Kara, and Minnelusa and Madison aquifers), only their 

hydraulic properties will be discussed. For purposes of 

this report, alluvial aquifers include saturated portions 

of terrace and windblown deposits. The Minnelusa and 

Madison aquifers will be discussed together because 

the deepest wells in the study area are completed in 

both aquifers. A summary of the aquifers in the study 

area is presented in table 4.

Shallow Aquifers

The shallow aquifers in the study area consist 

primarily of unconsolidated sand and gravel or poorly 

consolidated sandstones and siltstones. Alluvial 

aquifers are found in both Mellette and Todd Counties; 

however, the water has high dissolved solids, is moderately saline, and is very hard in Mellette County where 

alluvial deposits are underlain by the Pierre Shale. The 

Ogallala aquifer is present in only Todd County. The 

Arikaree aquifer is present throughout most of Todd 

County and in only small areas of Mellette County. 

The White River aquifer is present in both counties, but 

the aquifer primarily is used only in Mellette County 

because shallower water usually can be obtained in 

Todd County. 

Because the aquifer material within each of the 

formations can vary greatly even within a section of 

land, it was not possible to delineate specific waterbearing deposits within each formation. All formations 

were assumed to be fully saturated. Therefore, in the 

following discussions, the term “aquifer” refers to the 

entire formation where saturated and not to any particular interval within that formation. The following paragraph describes some of the other aquifer and 

formation names used in other reports to describe the 

shallow geologic units in the study area.

The High Plains aquifer system is a regional 

aquifer that consists mainly of deposits of Quaternary 

and Tertiary age that are hydraulically connected 

(Dugan and others, 1994). The High Plains aquifer 

system extends from southern South Dakota to Texas.

1

Arithmetic mean from test-hole data; all formations assumed to be fully saturated. 2Storage estimated by multiplying average thickness times areal extent times a porosity of 0.20 for all aquifers except Pierre Shale; a porosity

of 0.001 was used in storage calculation for Pierre Shale. 3

Based on irrigation-water classification diagram (fig. 31).

4Though water quality generally is suitable for irrigation, in most places yields will be insufficient to support irrigation. 5

Maximum value because saturated thickness probably is much less than average thickness. 6

Average thickness greater than indicated because not all test holes fully penetrated the aquifer. 7

Minimum value because average thickness greater than indicated. 8

Minimum values because no information available on depths in Todd County.

9

Though generally suitable for irrigation, in some places the water in the aquifer is not suitable.

Table 4. Summary of the characteristics of major aquifers in Mellette and Todd Counties

[--, data insufficient for estimate]

Aquifer name

Estimated 

areal extent 

(square 

miles)

Maximum 

thickness

(feet)

Average 

thickness1

(feet)

Range in depth 

below land

surface to top 

of aquifer

(feet)

Range of 

water level 

(feet below or 

above (+) land 

surface

Estimated 

amount of 

water in 

storage2

(million

acre-feet)

Range in 

reported well 

yields

(gallons per 

minute)

Suitable

for 

irrigation3

Alluvial 440 104 29 0 - 94 0 - 94 1.6 1 - 125 Yes4

Ogallala 950 239 137 0 - 164 3 - 164 17 1 - 1,250 Yes

Arikaree 1,360 618 290 0 - 406 +18 - 170 50 1 - 1,005 Yes

White River 1,720 469 229 0 - 789 +6 - 261 50 1 - 30 Yes4

Pierre Shale 2,694 1,294 900 0 - 1,204 2 - 200 51.5 1 - 8 No

Dakota 

Sandstone

2,694 336 6236 1,270 - 2,348 +102 - 450 781 10 - 100 No

Inyan Kara -- 275 6136 81,915 - 2,450 +289 - 300 -- 9 - 160 No

Minnelusa and 

Madison

-- 882 6608 82,105 - 2,448 +79 - 44 -- 25 - 40 Yes9
24 Water Resources of Mellette and Todd Counties, South Dakota

The principal aquifer in this system is the Ogallala; the 

Arikaree and Brule aquifers also are included in this 

system. The Brule Formation is the upper unit of the 

White River Group and the Chadron Formation is the 

lower unit. In some studies, it has been possible to distinguish between the two units of the White River 

Group; however, because the lithologic units could not 

be distinguished in most of the study area, the White 

River Group was not subdivided in this report. Additionally, references are sometimes made to the Rosebud 

Formation, which is part of the Arikaree Formation, 

and to the Ash Hollow and Valentine Formations, 

which are part of the Ogallala Formation.

In the following sections, monthly precipitation 

data were compiled from annual summaries (U.S. 

Department of Commerce, 1957-94) to determine the 

cumulative departure from normal precipitation. The 

National Weather Service station at Valentine, 

Nebraska, located 10 miles south of the South DakotaNebraska border on highway 83, was used because it 

had a more complete record than the stations at Wood 

and Mission.

Alluvial Aquifers

The major alluvial deposits are located along the 

Keya Paha, Little White, and White Rivers and associated tributaries, and are considered aquifers where 

saturated. Generally, the alluvial aquifers that overlie 

the Pierre Shale are essentially impermeable because of 

the high percentage of clay and supply only a small 

amount of water. Also, some alluvial aquifers along the 

White River are not in hydraulic connection with the 

river (Ellis and others, 1971), and therefore do not yield 

an adequate supply of water.

The composition of the alluvial deposits varies 

from clayey silt to gravel. Deposits that overlie Tertiary 

deposits are composed mainly of sand and gravel in 

comparison to deposits that overlie the Pierre Shale, 

which generally contain a greater percentage of clay. 

Alluvial aquifers underlie about 440 square miles of 

the study area and contain an estimated 1.6 million 

acre-feet of water in storage. The saturated thickness of 

the alluvial deposits along streams generally ranges 

from about 10 to 40 feet (fig. 14) and averages 29 feet. 

The thicknesses of two terrace deposits in Mellette 

County exceeded 100 feet, although only about 10 feet 

of these deposits were saturated. The general direction 

of ground-water flow in the alluvial aquifers is toward 

the streams and rivers and downstream (fig. 15). Water 

in alluvial aquifers along the Little White River, 

Blackpipe, Oak, and White Thunder Creeks generally 

flows north; water in aquifers along the Keya Paha and 

White Rivers generally flows east. 

Records of long-term water-level fluctuations in 

well 43N28W8CCDC in Mellette County and well 

38N28W32BBBB in Todd County (fig. 16) correlate 

well with long-term precipitation data, although the 

correlation is more evident in the Mellette County well. 

The water-level decline from 1974-76 was caused by 

below-normal precipitation. The increase in water 

levels from 1991-95 was caused by above-normal 

precipitation.

Recharge to the alluvial aquifers is by infiltration 

of precipitation, stream loss when the stream stage is 

higher than the hydraulic head in the aquifer, and discharge from springs originating in Tertiary aquifers. 

Generally, the greatest recharge occurs in the spring 

after snowmelt. Infiltration rates generally range 

between 1 and 6 inches/hour in the alluvial deposits 

(U.S. Soil Conservation Service, 1974, 1975), so 

precipitation is a major source of recharge to these 

deposits. Discharge from the aquifer is by withdrawals 

of water from domestic and stock wells and by evapotranspiration from the aquifer. The cyclic pattern of 

recharge and discharge is evident in the water-level 

fluctuations of well 38N28W32BBBB (fig. 16). Every 

year, the water level is highest in the spring due to 

snowmelt and high streamflows, and is lowest during 

the summer and fall months when potential evapotranspiration is the greatest and precipitation decreases.

The only available information concerning the 

hydraulic properties of the alluvial aquifers in the study 

area was specific capacity data stored in the USGS 

NWIS ground-water database for eight wells completed in alluvial deposits. The specific capacity of a 

well is the rate of discharge of water from a well 

divided by the drawdown of the water level within the 

well (Lohman and others, 1972). The specific capacity 

of the 8 alluvial wells ranged from 6 to 900 square feet 

per day with an average of 400 square feet per day.

Ogallala Aquifer

The Ogallala aquifer is present throughout most 

of Todd County, but not in Mellette County. A hydrogeologic section (A-A') across the southern boundary 

of Todd County (fig. 17) shows the Ogallala aquifer 

and the underlying Arikaree and White River aquifers. 

The Ogallala Formation is overlain by unconsolidated 

deposits consisting of alluvium and windblown sand 

deposits in the southwestern part of Todd County.
Ground Water 25

Figure 14. Extent and thickness of alluvial aquifers.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHTE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43o

45'

43o

30'

43o

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100o45' 100o30'

R. 26 W. R. 25 W.

100o15'

43o

00'

Sand

Creek

Crazy

Hole Cr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

83

18

18

83

63

63

44

44

53

BENNETTE COUNTY JACKSON COUTNY

JONES COUNTY

LYMAN COUNTY TRIPP COUTNY

White

Lake

18+

23+ 28+ 52+

6+

33+

27+

34+

28+

55+

25+

26+

26+

23

25+ 22+ 39+

42+ 27+

21+

37+

34+

32+

30+

32+

48+

12+ 10

33+

22+

33+

15+

22+

48+

38+ 48+

35+

40+ 42+

32+

33+

27+

16+

25+32+

17+

50+

45+ 72+

40+

27+

10

18

25

24

10

24

23

44

13

14

16

35

30

12

38

5

5

14

18

23

5

28

24 10

30

33 38

18

38

19

48

35

26

40

41

14

18

20

7

22

71 10

20

18+

23+ 28+ 52+

6+

33+

27+

34+

28+

55+

25+

26+

26+

23

25+ 22+ 39+

42+ 27+

21+

37+

34+

32+

30+

32+

48+

12+ 10

33+

22+

33+

15+

22+

48+

38+ 48+

35+

40+ 42+

32+

33+

27+

16+

25+32+

17+

50+

45+ 72+

40+

27+

10

18

25

24

10

24

23

44

13

14

16

35

30

12

38

5

5

14

18

23

5

28

24 10

30

33 38

18

38

19

48

35

26

40

41

14

18

20

7

22

71 10

20

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000

EXPLANATION

APPROXIMATE AREA UNDERLAIN BY ALLUVIAL AQUIFERS

 (modified from Ellis and others, 1971)

WELL OR TEST HOLE--Numbers are saturated thickness, in feet, of aquifer.

 A plus (+) indicates a thickness greater than shown.

32+
26 Water Resources of Mellette and Todd Counties, South Dakota

Figure 15. Potentiometric surface of alluvial aquifers.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHTE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43o

45'

43o

30'

43o

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100o45' 100o30'

R. 26 W. R. 25 W.

100o15'

43o

00'

Sand

Creek

Crazy

Hole Cr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

83

18

18

83

63

63

44

44

53

BENNETTE COUNTY JACKSON COUNTY

JONES COUNTY

LYMAN COUNTY TRIPP COUNTY

White

Lake

2150

2200

2200

2150

2100

2050

2000

2100

2150

2200

2250

2200

2250

1950

1900

1850

1900 1950

2000

2050

2150

2150

1800

1850

1900

1950

2050

2000

2200

2150

2150

2100

2000

1950

1800

2000

2050

2150

1750

2150

2100

2050

2050

1900

2050

2000

1950

1900

1850

1800

1700

1750

1700

1750

1800

1850

1650

2400

2350

2300

2250

2000

2000

2050

2050

1950

1900

1850

1800

2200

2150

2400

2350

2450

2100

2400

2350

2300

2250

2250

2200 2200

2050

2300

2250

2100

2200

2150

2650

2600

2550

2500

2450

2400

2350

2300

2250

2450

2550

2500

2450

2350

2500

2450

2450

2400

2400

2350 2250 2300

2500

2500

2550

2600

2650

2700

2750

2800

2400

2300

2400

2600

2500

2350

2450

2400

2350

2300

2250

2200

2200

2600

2550

2650

2500

2500

2450

2400

2350

2300

2450

2100

2150

2150

2200

2250

2250 2300

2600

2550

2500

2450

2400

2350

2300

2350

2400

2450

2500

2550

2600

2650

2700

2800

2750

2700

2650

2600

2550

2500

2750 3000

2950

2900

2850

2800

2800 2800

2850

2247 2067

2060

1928 2094

2104

2275

2091

2298

1866

2531

2310

2493

2291

2280

2246 2244

2218

2145

1918

2179

1932

2194

1995

1950

2201 2300 2055

2153

1924

1863

1855 1845

2160

2104

1806 1793 2107

1795

1794

1978

2124

2137

1909

2043

2068

2199

2131

2131 2125

2108

1836

1790 1983

1709

1870

2080 2095

2043

1937

2055

1697

1988

1960

1635

1879 1895

1673

1650

1765 1909

1752

1817

1979 1826 1930

1875 18421863

2196

2196

2136

2133

2154

2156 2198

2214

2268

2238

2458 2256

2068

2035

2124

2367

2112

2217

2178

2589

2465

2545

2560

2325

2390

2290

2606

2421

2311

2613 2648

1775

2648

2404

2419

1649

2025

2431

2784

1997

1792

1807

1759 1775

2033

2621 2614

2409

2254

1997

1792

1807

1759 1775

2033

2621 2614

2409

2254

2247 2067

2060

1928 2094

2104

2275

2091

2298

1866

2531

2310

2493

2291

2280

2246 2244

2218

2145

1918

2179

1932

2194

1995

1950

2201 2300 2055

2153

1924

1863

1855 1845

2160

2104

1806 1793 2107

1795

1794

1978

2124

2137

1909

2043

2068

2199

2131

2131 2125

2108

1836

1790 1983

1709

1870

2080 2095

2043

1937

2055

1697

1988

1960

1635

1879 1895

1673

1650

1765 1909

1752

1817

1979 1826 1930

1875 18421863

2196

2196

2136

2133

2154

2156 2198

2214

2268

2238

2458 2256

2068

2035

2124

2367

2112

2217

2178

2589

2465

2545

2560

2325

2390

2290

2606

2421

2311

2613 2648

1775

2648

2404

2419

1649

2025

2431

2784

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000

EXPLANATION

APPROXIMATE AREA OF ALLUVIAL AQUIFERS (modified from Ellis and others, 1971)

POTENTIOMETRIC CONTOUR--Shows altitude at which water would have stood

 in tightly cased, nonpumping wells in 1996. Dashed where inferred. Contour interval

 50 feet. Datum is sea level.

WELL--Number is altitude of water level, in feet above sea level 2431

2500

GENERAL DIRECTION OF GROUND-WATER FLOW
Ground Water 27

Figure 16. Water-level fluctuations in alluvial aquifers and cumulative monthly departure from normal precipitation at 

Valentine, Nebraska. WATER LEVEL, IN FEET BELOW LAND SURFACE

CUMULATIVE MONTHLY DEPARTURE FROM

NORMAL PRECIPITATION, IN INCHES

7

8

9

10

11

12

8

10

12

14

16

18

20

10

-10

0

-20

-30

-40

1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996

WELL 38N28W32BBBB, ALLUVIAL AQUIFER, TODD COUNTY

WELL 43N28W 8CCDC, ALLUVIAL AQUIFER, MELLETTE COUNTY

Base Period 1961-90
28 Water Resources of Mellette and Todd Counties, South Dakota

Figure 17. Hydrogeologic section A-A′ showing aquifers of Quaternary, Tertiary, and Cretaceous age in Todd County. (The location of section A-A′ is shown in fig. 2).

0246 MILES0246 KILOMETERS

3,2003,1003,0002,9002,8002,7002,6002,5002,4002,3002,2002,1002,0001,9001,800

FEET

A

A'

DATUM IS SEA LEVEL VERTICAL SCALE IS GREATLY EXAGGERATED

EXPLANATION

QUATERNARY UNCONSOLIDATED DEPOSITS

Alluvial aquiferWindblown sand deposits

Qa

Qwd

CRETACEOUS SEDIMENTARY DEPOSITS

CONTACT--Dashed where inferredTEST HOLE

Pierre Shale aquifer Kp

TERTIARY SEDIMENTARY DEPOSITS

Ogallala aquiferArikaree aquiferWhite River aquifer

ToTa

Tw

Qa

Qa

Qa

Qa

Qa

Qa

To

To

To

To

Ta

Ta

Ta

Tw

Tw

Tw

Kp

Kp

Kp

Qwd

Qwd

35N33W20ACBB

35N32W9BABB4

35N31W10CBBC2

35N30W5DDCC

35N29W7BBBB

35N29W21BBBB

35N29W2DDDD3

35N28W15BBBD

35N27W3BBBB3

35N26W10CBBA

36N26W31ADDD

35N25W20BBBC2

35N25W13DADD3

Spring Creek

Minnechaduza Creek

Sand Creek
Ground Water 29

The Ogallala Formation consists primarily of 

poorly consolidated, fine- to medium-grained sandstone with some interbedded clay and silt. The saturated sandstones and silt of the Ogallala Formation 

make up the Ogallala aquifer. The depth to the top of 

the aquifer ranges from 0 to 164 feet below land surface, and the average thickness is 137 feet (table 4). 

The aquifer underlies about 950 square miles in Todd 

County and contains about 17 million acre-feet of water 

in storage. Generally, the aquifer is thickest in the central portion of Todd County, where use of the aquifer for 

irrigation is highest. The potentiometric surface of the 

Ogallala aquifer is shown in figure 18. Most of the 

aquifer is under water-table conditions, except in the 

southwest part of Todd County where the aquifer is 

confined by well-cemented or concretion beds in the 

upper part of the Ogallala Formation. The depth to 

water in wells generally is less than 10 feet below land 

surface where the aquifer is confined. Under watertable conditions, the depth to water ranges from 3 to 

greater than 150 feet below land surface. The aquifer 

has the highest yield potential of the aquifers in the 

study area; the maximum reported well yield is 

1,250 gallons per minute (table 4).

Records of long-term water-level fluctuations in 

well 36N30W13BBBB and well 37N28W21CCCC 

(fig. 19) correlate well with long-term precipitation 

data prior to 1990. The water-level decline in 1981 was 

caused by below-normal precipitation. The increase in 

water levels from 1982 to 1984 was caused by abovenormal precipitation. However, the water-level decline 

in both wells since 1990 does not correspond with 

below-normal precipitation; rather, the decline 

probably was caused by increased withdrawals of water 

for irrigation. In general, regional studies of the Ogallala aquifer indicate that water levels have not substantially declined in South Dakota due to irrigational 

development (Dugan and others, 1994). Predictions for 

further development of the Ogallala aquifer in South 

Dakota indicate that the water-level declines through 

2020 generally will be less than 10 feet in most areas of 

Todd County (Luckey and others, 1988). 

Recharge to the Ogallala aquifer primarily is by 

infiltration of precipitation on outcrops of the Ogallala 

Formation or overlying windblown sand deposits 

(fig. 4) and by stream loss as streams cross the outcrop 

of the Ogallala Formation when the stream stage is 

higher than the hydraulic head in the aquifer. Infiltration rates generally are greater than 2 inches/hour in the 

Ogallala Formation and generally are greater than 

6 inches/hour in the overlying windblown sand 

deposits (U.S. Soil Conservation Service, 1974), so 

precipitation is a major source of recharge to the 

aquifer. Discharge from the aquifer is through withdrawals from domestic, public, stock, and irrigation 

wells; by loss to streams and springs; and by evapotranspiration from the aquifer where the aquifer is at 

or near land surface. 

Transmissivity is the rate at which water of the 

prevailing kinematic viscosity is transmitted through a 

unit width of the aquifer under a unit hydraulic gradient (Lohman and others, 1972). Transmissivities of 

the Ogallala aquifer were estimated for the waterbearing sediments of 10 test holes along the boundary 

between Todd County and Nebraska; transmissivities 

ranged from 800 to 9,200 square feet per day, with an 

average of 2,800 square feet per day (Newport, 1959). 

Additionally, specific capacity data stored in the 

USGS NWIS ground-water database were available 

for 65 wells completed in the Ogallala aquifer. The 

specific capacity ranged from 2 to 2,400 square feet 

per day, with an average of 600 square feet per day. 

Hydraulic conductivity is the volume of water an 

aquifer will transmit under a unit hydraulic gradient, 

through a unit cross-sectional area, measured at right 

angles to the direction of flow (Lohman, 1972). 

Transmissivity is equal to the hydraulic conductivity 

times the saturated thickness of the aquifer. Average 

hydraulic conductivities of the Ogallala aquifer in 

south-central South Dakota, estimated from 205 well 

logs, ranged from 3.6 to 160 feet per day, with an 

average of 30 feet per day (Kolm and Case, 1983).

Arikaree Aquifer

The Arikaree aquifer is present throughout most 

of Todd County, but is present in only a small part of 

southwestern Mellette County. The Arikaree Formation is not present along the eastern boundary of Todd 

County (fig. 7). The absence of the Arikaree aquifer 

in eastern Todd County also is shown in the hydrogeologic section B-B' (fig. 20).

The Arikaree Formation is predominantly composed of pinkish-tan to red, clayey, tuffaceous siltstones and sandstones. The Arikaree aquifer is 

composed primarily of the saturated sandstones and 

siltstones within the Arikaree Formation. The depth to 

the top of the aquifer ranges from 0 to 406 feet below 

land surface, and the average thickness is 290 feet 

(table 4). The aquifer underlies approximately 

1,360 square miles of the study area and contain about
30 Water Resources of Mellette and Todd Counties, South Dakota

Figure 18. Potentiometric surface of the Ogallala aquifer.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHTE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43o

45'

43o

30'

43o

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100o45' 100o30'

R. 26 W. R. 25 W.

100o15'

43o

00'

Sand

Creek

Crazy

Hole Cr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Creek

Antelope

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

83

18

18

83

63

63

44

44

53

BENNETTE COUNTY JACKSON COUNTY

JONES COUNTY

LYMAN COUNTY TRIPP COUNTY

White

Lake

2900

2800

2900 3000

3050

2950

2850

2800

2850

2900

2950

3000

2900

2500

2500

2550

2550

2600

2600

2650

2650

2800

2800

2800

2800

2400

24002500

25002600

2850

2850

2600

2500

2800

2750

2750

2750

2700

2700

2700

2876

2882

2855

2646

2728

2749

2835

2785 2706

2497

2915 2580

2803

2848

2853

2810

2585 2662

2731

2765

2763

2879

2595

2847

2715

2821

2578

2739 2772

2819

2711

2437

2505

2470

2467

2601

2468

2628

2614

2644

2810

3009

2793 2780

2741

2753

3035

2974 2912 2814 2890

2850

2849

2854 2847

2876

2882

3009 2948

3032

2956

2918

2776 2715

2871 2855

2811

2777

2737

2644 2817

2646

2728

2749

2644

2596

2751

2955

2829

2835 2842

2815

2726

2787 2744 2725

2931

2895

2960

2833

2927

2625

2668 2785 2522 2710 2679 2578

2706 2652 2625

2687

2699

2621 2875

2497 2829 2780

2497

2808 2833

2660 2833 2680

2630

2605

2810 2511

2532 2515

2527 2848 2756 2610

2614 2856

2545

2665

2623 2915

2780 2669

2765 2580

2803

2603

2741

2876

2797

2849

2828

2422

2609

2677 2783 2707

2739 2800

2772

2819

2813

2887 2815

2864

2843

2823 2794 2818

2870 2825

2831 2848 2944 2853 2842

2855

2784

2870 2838 2820

2810

2387 2437

2585 2662

2714 2772

2741

2753 2760 2731 2765

2800

2807

2765

2800

2763

2879

2377

2505 2407

2470

2467

2601

2468

2741

2628

2614

2775

2595 2748

2711

2682

2817

2817

2793 2847

3032

2715

2821

2842

2753

2809

2662

2575

2490 2435

2792

2745

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000

EXPLANATION

APPROXIMATE AREA UNDERLAIN BY THE OGALLALA AQUIFER (modified from Ellis and others, 1971)

POTENTIOMETRIC CONTOUR--Shows altitude at which water would have stood in tightly cased, nonpumping

 wells in 1996. Dashed where inferred. Contour interval 50 feet. Datum is sea level.

WELL--Number is altitude of water level, in feet above sea level 2745

2900

GENERAL DIRECTION OF GROUND-WATER FLOW
Ground Water 31

Figure 19. Water-level fluctuations in the Ogallala aquifer and cumulative monthly departure from normal precipitation at 

Valentine, Nebraska. WATER LEVEL, IN FEET BELOW LAND SURFACE CUMULATIVE MONTHLY DEPARTURE FROM NORMAL PRECIPITATION, IN INCHES

71.0

71.5

72.0

72.5

73.0

73.5

74.0

43

44

45

46

47

48

49

50

40

30

20

10

0

-10

WELL 36N30W13BBBB, OGALLALA AQUIFER, TODD COUNTY

WELL 37N28W21CCCC, OGALLALA AQUIFER, TODD COUNTY

Base Period 1961-90

1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994
32 Water Resources of Mellette and Todd Counties, South Dakota

Figure 20. Hydrogeologic section B-B′ showing aquifers of Quaternary, Tertiary, and Cretaceous age in Todd County. (The location of section B-B′is shown in fig. 2.)

0246 MILES0246 KILOMETERS

3,2003,1003,0002,9002,8002,7002,6002,5002,4002,3002,2002,1002,0001,9001,800

FEET

B

B'

DATUM IS SEA LEVEL VERTICAL SCALE IS GREATLY EXAGGERATED

EXPLANATION

QUATERNARY UNCONSOLIDATED DEPOSITS

Alluvial aquifer Qa

CRETACEOUS SEDIMENTARY DEPOSITS

CONTACT--Dashed where inferredTEST HOLE

Pierre Shale aquifer

Kp

TERTIARY SEDIMENTARY DEPOSITS

Ogallala aquiferArikaree aquiferWhite River aquifer

ToTa

Tw

To

To

Qa

Qa

Ta

Ta

Ta

Tw

Tw

Tw

Kp

Kp Kp

39N33W15DDDD

39N32W19BBBB

39N32W27AAAA

39N31W27BBBB

39N30W20DAAD

39N29W26DBAA

38N29W13ADDC2

38N27W7DDDD

39N27W35AAAB

39N26W36BABB

38N25W1ACDD

Little White River

Antelope Creek

Antelope Creek

Qa

Qa Qa

Qa

Qa

Chunker Swimmer Creek

Cut Meat Creek
Ground Water 33

50 million acre-feet of water in storage. The aquifer is 

thickest in southern Todd County. The potentiometric 

surface of the Arikaree aquifer is shown in figure 21. 

About one-half of the aquifer is under water-table conditions and one-half is confined. The aquifer is confined where overlain by impermeable materials in the 

Ogallala Formation, and the deeper part of the aquifer 

is under confined conditions where impermeable 

material exists in the upper part of the formation. Two 

flowing observation wells completed in the Arikaree 

aquifer are located at 36N33W17BACA. Water levels 

in the aquifer generally are within 60 feet of land 

surface under confined conditions, and range from 3 to 

greater than 150 feet under water-table conditions. 

Yields from the aquifer, which range from 1 to 

1,005 gallons per minute (table 4), are dependent on the 

percentage of clay in the formation, consolidation of the 

materials, and well construction. Yields usually are not 

as great as those from the Ogallala aquifer, but are substantially greater than yields from the under-lying 

White River aquifer (table 4).

Records of long-term water-level fluctuations in 

well 40N32W21BBBB in Mellette County (fig. 22) 

correlate well with long-term precipitation data; 

records from well 37N29W22CCCC in Todd County 

do not correlate as well possibly because of distance 

from the outcrop. The Arikaree Formation is exposed 

at land surface at the well site in Mellette County 

(fig. 4), and infiltration of precipitation directly 

recharges the aquifer; therefore, the water-level fluctuations correlate well with precipitation data. Waterlevel fluctuations at both wells show the typical cyclic 

pattern of higher water levels during the spring due to 

precipitation recharge and lower water levels in the fall 

due to evapotranspiration and decreasing precipitation. 

Recharge to the Arikaree aquifer primarily is by 

infiltration of precipitation on the outcrops of the 

Arikaree Formation (fig. 4) and by stream loss as 

streams cross the outcrop of the Arikaree Formation 

when the stream stage is higher than the hydraulic head 

in the aquifer. The greatest recharge to the aquifer 

occurs during the spring after snowmelt and during 

storm events. Infiltration rates generally range between 

0.6 and 1.2 inches/hour (U.S. Soil Conservation Service, 1974, 1975). Discharge from the aquifer is 

through withdrawals from domestic, stock, and irrigation wells; by evapotranspiration where the aquifer is at 

or near land surface; and by discharge from springs to 

alluvial aquifers and streams when the hydraulic head 

in the Arikaree aquifer is higher than the hydraulic head 

in the alluvial aquifers or stage in the streams.

Specific capacity data stored in the USGS 

NWIS ground-water database for 184 wells completed 

in the Arikaree aquifer ranged from 2 to 2,000 square 

feet per day, with an average of 90 square feet per day. 

Analyses of four aquifer tests conducted near Pine 

Ridge, South Dakota, by Greene and others (1991) 

yielded a hydraulic conductivity of 13 feet per day and 

a transmissivity of 1,250 square feet per day in the 

unconfined Arikaree aquifer. In the confined Arikaree 

aquifer, the hydraulic conductivity was reported as 

1 foot per day and the transmissivity was 300 square 

feet per day (Greene and others, 1991). A core sample 

from the Arikaree Formation in Nebraska had a 

hydraulic conductivity of about 2 feet per day (Bradley, 1956).

White River Aquifer

The White River aquifer is present throughout 

most of Todd County and in western and south-central 

Mellette County. The White River aquifer is used as a 

water source in northern Todd County where the 

Ogallala and Arikaree aquifers are not present. The 

aquifer is used in Mellette County where present 

because it is usually the shallowest source of water. A 

hydrogeologic section (C-C') from the northwestern 

boundary of Mellette County to the south-central part 

of Todd County (fig. 23) shows the White River aquifer where present.

The White River aquifer consists predominantly 

of the saturated, poorly consolidated siltstones and 

claystones and interbedded sand layers within the 

White River Group. The depth to the top of the aquifer 

ranges from 0 to 789 feet below land surface, and the 

average thickness is 229 feet (table 4). This aquifer 

underlies approximately 1,720 square miles of the 

study area and contains about 50 million acre-feet of 

water in storage. The White River aquifer is thickest in 

western Todd County and southwestern Mellette 

County. The potentiometric surface of the aquifer is 

shown in figure 24. The aquifer is under water-table 

conditions where it is at or near the land surface, and is 

confined where overlain by the Ogallala Formation 

and/or the Arikaree Formation (fig. 4). Thus, most of 

the aquifer is confined in the study area. One observation well (107 feet deep) completed in the aquifer at 

37N25W24BCBB currently flows. Two shallower 

observation wells (less than 60 feet deep) completed in 

the aquifer at this same location do not flow, but water 

levels in both wells are within 10 feet of land surface. 

Water levels in the aquifer generally are less than 

100 feet below land surface under both water-table and 

confined conditions, but water-level depths exceeding
34 Water Resources of Mellette and Todd Counties, South Dakota

Figure 21. Potentiometric surface of the Arikaree aquifer.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHTE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43o

45'

43o

30'

43o

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100o45' 100o30'

R. 26 W. R. 25 W.

100o15'

43o

00'

Sand

Creek

Crazy

Hole Cr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

83

18

18

83

63

63

44

44

53

BENNETTE COUNTY JACKSON COUNTY

JONES COUNTY

LYMAN COUNTY TRIPP COUNTY

White

Lake

2900

2800

3000 2800

3000

3000

2500

2500

2500

2500

2500

2700

2700

2700

2700

2700

2500

2600

2600

2600

2600

2600

2400

2400

2900

2900

2900

2800

2800

2800

2800

2800

2500

2700

2600

2500

2500

2500

2700

2505 2605

2610 2554

2685

2521

2549

2650 2538 2650

2690 2714

2602

2506

2497

2638 2794

2700 2602

2563

2477 2928

2779 2735

2673

2539 2608

2626

2492

2638

2683

2615

2468

2545

2643 2604

2570

2909 2882

2692

2476

2444 2498 2421

2525

2397

2470

2584

2611

2506 2510 2525

2602

2483

2646

2590

2766

2562

2504

2734

2622

2736

2605

2649

2642

2712

2416

2505 2605

2660

2610 2554

2675

2685

2844 2786

2453

2521

2549

2475

2650 2538

2771 2630

2690

2650

2605

2690 2714

2602

2786

2506

2497

2638 2794

2655

2700 2734

2622

2602

2563

2477 2928

2685

2853

2734

2631

2820 2860

2800 2779 2735

2666

2733 2673 2721

2538

2528

2732

2539

2529 2608

2585

2626

2723

2696

2667

2704

2625 2492

2638

2520

2650

2835 2820

2542

2636

2642

2683

2630

2615

2584

2468

2454

2551

2507

2508

2545

2475

2567

2552

2600

2616

2398 2524

2595

2527

2712

2643

2589

2604

2690 2592 2548 2575

2520 2525

2495

2528

2667 2649

2570

2736

2882

2831

2909

2933

2720

2627

2692

2735

2476

2848 2669

2612

2780 2718 2673

2648

2673

2645

2630

2642

2610

2828

2468

2444

2605

2560

2515

2548

2536 2450

2501 2430

2390

2375

2362

2353 2404 2416

2560

2498

2456 2421

2525 2536

2514

2583

2416

2426

2420

24402416

2397

2343

2418

2601

2349

2488

2476 2498

2469

2454

2480 2470

2628 2584

2611

2477

2514 2537

2506 2510 2525

2615

2505

2568 2598

2624 2602

2586

2459

2483

2646

2646 2595

2471

2590

2780

2613

2810

2490

2766

2829

2776

2582

2460

2526

2815

2562

2431

2516 2504

2823

2876

3032

2930

2821

2753

2661

2490

2539

2570

2554

2609

2714

2749

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000

EXPLANATION

APPROXIMATE AREA UNDERLAIN BY THE ARIKAREE AQUIFER (modified from Ellis and others, 1971)

POTENTIOMETRIC CONTOUR--Shows altitude at which water would have stood in tightly cased,

 nonpumping wells in 1996. Dashed where inferred. Contour interval 100 feet. Datum is sea level.

WELL--Number is altitude of water level, in feet above sea level 2749

2900

GENERAL DIRECTION OF GROUND-WATER FLOW
Ground Water 35

Figure 22. Water-level fluctuations in the Arikaree aquifer and cumulative monthly departure from normal precipitation at 

Valentine, Nebraska. WATER LEVEL, IN FEET BELOW LAND SURFACE

CUMULATIVE MONTHLY DEPARTURE FROM

NORMAL PRECIPITATION, IN INCHES

0

5

10

15

2.0

25

96

98

100

102

104

106

108

30

20

10

0

-10

WELL 40N32W21BBBB, ARIKAREE AQUIFER, MELLETTE COUNTY

WELL 37N29W22CCCC, ARIKAREE AQUIFER, TODD COUNTY

Base Period 1961-90

1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994
36 Water Resources of Mellette and Todd Counties, South Dakota

Figure 23. Hydrogeologic section C-C′ showing aquifers of Quaternary, Tertiary, and Cretaceous age in Mellette and Todd Counties. (The location of section C-C′ is shown in fig. 2.)

0246 MILES0246 KILOMETERS

3,2003,1003,0002,9002,8002,7002,6002,5002,4002,3002,2002,1002,0001,9001,800

FEET

C

C'

DATUM IS SEA LEVEL VERTICAL SCALE IS GREATLY EXAGGERATED

EXPLANATION

QUATERNARY UNCONSOLIDATED DEPOSITS

Alluvial aquiferTerrace deposit

Qa

Qt

CONTACTTEST HOLE

CRETACEOUS SEDIMENTARY DEPOSITS

Pierre Shale aquifer Kp

TERTIARY SEDIMENTARY DEPOSITS

Ogallala aquiferArikaree aquiferWhite River aquifer

ToTa

Tw

Tw

Kp

Kp

Kp

2S26E20BCCB

45N31W33BADD

44N31W9BBBB

44N31W28CCCB

43N31W17DADD

42N31W8AAAD

42N31W8DAAA

41N31W5DADD

41N31W33BCAD

40N30W4DDCC

40N29W15CDDD

39N29W1DBAB

39N29W26DBAA

38N29W13ADDC2

38N28W32BBBB

37N28W7BBBC

37N28W30BBAA

37N28W30CCCB

36N29W14DDDD

35N29W2DDDD3

North Branch Pine Creek

Cottonwood Creek

Yakmi Creek

Yakmi Creek

South Branch Pine Creek

Little White River

Antelope Creek

Antelope Creek

White Lake

White River

Tw

Tw

Ta

Tw

Qt

Tw

Qa

Qa

Tw

Tw

Tw

Tw

Ta

Ta

To

To

Qa

Qa

Tw

Qa

Qa

Qa

Qt

Qa

Qt
Ground Water 37

Figure 24. Potentiometric surface of the White River aquifer.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHTE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43o

45'

43o

30'

43o

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100o45' 100o30'

R. 26 W. R. 25 W.

100o15'

43o

00'

Sand

Creek

Crazy

Hole Cr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

83

18

18

83

63

63

44

44

53

BENNETTE COUNTY JACKSON COUNTY

JONES COUNTY

LYMAN COUNTY TRIPP COUNTY

White

Lake

2550

2550

2600

2600

2350

2400

2450

2500

2500

2300

2500

2450

2400

2400

2450

2350

2300

2400

2450

2350 2300

2450

2450

2400

2350

2500

2350

2350

2350

2300 2450

2400

2300

2300

2450

2400 2500

2550

2500

2450

2400

2513

2465

2284

2420

2633

2494

2398 2343

2524 2494 2390 2442

2432

2391

2444 2382

2500

2374

2451

2386

2402

2486

2600 2354

2394

2364

2305

2259

2480 2460 2340 2550 2525 2475 2535 2545 2557

2578 2277 2475 2525

2484

2477

2598

2570 2424

2331

2615

2580

2301

2584

2512

2323

2433

2452 2480

2403

2470

2450

2330

2410

2470

2450

2466

2449

2318

2332 2366

2331 2309

2356

2384

2345 2440

2301 2285 2474

2387

2365

2363

2277

2267

2420

2308

2337

23302338

2329 2314

2332

2377

2348

2430

2439

2403

2280 2346

2412

2428

2465

2293

2370

2274 2352

2490

2621

2529 2532

2394

2305

2533

2536

2536

2397

2568

2297

2513

2465

2284

2420

2633

2494

2398 2343

2524 2494 2390 2442

2432

2391

2444 2382

2500

2374

2451

2386

2402

2486

2600 2354

2394

2364

2305

2259

2480 2460 2340 2550 2525 2475 2535 2545 2557

2578 2277 2475 2525

2484

2477

2598

2570 2424

2331

2615

2580

2301

2584

2512

2323

2433

2452 2480

2403

2470

2450

2330

2410

2470

2450

2466

2449

2318

2332 2366

2331 2309

2356

2384

2345 2440

2301 2285 2474

2387

2365

2363

2277

2267

2420

2308

2337

23302338

2329 2314

2332

2377

2348

2430

2504

2439

2444

2403

2280 2346

2412

2428

2465

2293

2370

2274 2352

2490

2621

2529 2532

2394

2305

2533

2536

2536

2397

2376

2568

2297

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000

EXPLANATION

APPROXIMATE AREA UNDERLAIN BY THE WHITE RIVER AQUIFER (modified from Ellis and others, 1971)

POTENTIOMETRIC CONTOUR--Shows altitude at which water would have stood in tightly cased, nonpumping

 wells in 1996. Dashed where inferred. Contour interval 50 feet. Datum is sea level.

WELL--Number is altitude of water level, in feet above sea level 2912

2900
38 Water Resources of Mellette and Todd Counties, South Dakota

200 feet below land surface have been recorded in 

northwestern Todd County and southwestern Mellette 

County. Yields from the aquifer range from 1 to 

30 gallons per minute (table 4), and are dependent on 

the percentage of clay in the formation, consolidation 

of the siltstones and sandstones, thickness of the siltstones and sandstones, and well construction. Yields 

generally are sufficient for domestic and stockwatering purposes.

Records of long-term water-level fluctuations in 

well 40N32W32BBBB in Mellette County and in well 

37N25W23ADAD in Todd County (fig. 25) correlate 

reasonably well with long-term precipitation data. 

However, the below-normal precipitation during 

1974-76 does not correlate with water-level fluctuations in the Todd County well, and the cause of the 

water-level decline in the Mellette County well in 1979 

is not known. Both wells show an increase in water levels due to above-normal precipitation beginning in 

1992-93 through the end of the period shown.

Recharge to the White River aquifer primarily is 

by infiltration of precipitation on the outcrops of the 

White River Group (fig. 4), and by stream loss as 

streams cross the outcrop of the White River Group 

when the stream stage is higher than the hydraulic head 

in the aquifer. The greatest recharge to the aquifer 

occurs during the spring after snowmelt and during 

storm events. Infiltration rates range from less than 

0.06 to 0.6 inches/hour (U.S. Soil Conservation 

Service, 1974, 1975). Discharge from the aquifer is 

through withdrawals from domestic and stock wells, by 

evapotranspiration where the aquifer is at or near land 

surface, and by discharge from springs to alluvial 

deposits and streams when the hydraulic head in the 

aquifer is higher than the hydraulic head in the alluvial 

deposits or the stage in the streams.

Specific capacity data stored in the USGS NWIS 

ground-water database were available for 26 wells 

completed in the White River aquifer. The specific 

capacity ranged from 2 to 2,500 square feet per day, 

with an average of 160 square feet per day. 

Bedrock Aquifers

The bedrock aquifers in the study area include 

the Pierre Shale, Dakota Sandstone, Inyan Kara, and 

Minnelusa and Madison aquifers. The Pierre Shale 

aquifer, which is the shallowest bedrock aquifer in the 

study area, generally is used only in Mellette County as 

a source of ground water. Few wells have been completed in the deeper aquifers because of cost and 

because water usually can be obtained from a 

shallower aquifer or from other sources. Most of the 

available bedrock-aquifer information in the study area 

is from wells located in northern Mellette County. Test 

drilling for this study usually stopped just below the 

upper contact of the Pierre Shale. Therefore, other than 

the Pierre Shale, the deeper bedrock aquifers were not 

penetrated during the test drilling.

Pierre Shale Aquifer

The Pierre Shale aquifer is present throughout 

the study area. The upper part of the Pierre Shale 

generally is weathered and fractured. The Pierre Shale 

typically is not considered an aquifer in South Dakota, 

except in localities like Mellette County where individuals rely on the aquifer because it is the shallowest 

source of ground water available. Where the Pierre 

Shale is used to supply water, wells usually are completed in the weathered shale. The shale is exposed at 

the land surface throughout most of Mellette County 

and is overlain by the Tertiary deposits throughout most 

of Todd County (fig. 4). A hydrogeologic cross-section 

(D-D') from north to south along the eastern edge of 

Mellette and Todd Counties (fig. 26) shows that the 

Pierre Shale aquifer is the shallowest water source in 

eastern Mellette County, except where alluvial deposits 

are present. In eastern Todd County, the Pierre Shale is 

overlain by the White River Group and Ogallala Formation. As previously discussed, the Arikaree Formation is not present in eastern Todd County.

The Pierre Shale predominantly is a black shale. 

The depth to the top of the Pierre Shale in the study area 

ranges from 0 to greater than 1,200 feet (table 4). The 

aquifer contains an estimated maximum of 1.5 million 

acre-feet of water in storage (table 4). This aquifer 

generally is not a viable source of ground water 

because the aquifer is relatively impermeable, yields 

are low, and water usually can be obtained from shallower aquifers, especially in Todd County. The potentiometric surface of the aquifer is shown in figure 27. 

The potentiometric surface for the aquifer throughout 

most of Todd County could not be drawn because of 

insufficient data. Because the aquifer is used as a water 

source mainly in Mellette County, where the formation 

generally is present at or near the land surface, the 

aquifer is under water-table conditions. The general 

direction of ground-water flow in the Pierre Shale 

aquifer is to the north. Yields from the aquifer ranged 

from 1 to 8 gallons per minute (table 4) and are dependent on the amount of fracturing and the percentage of 

clay and sand present in the shale. No long-term waterlevel records were available for wells completed in the 

Pierre Shale.
Ground Water 39

Figure 25. Water-level fluctuations in the White River aquifer and cumulative monthly departure from normal precipitation 

at Valentine, Nebraska. WATER LEVEL, IN FEET BELOW LAND SURFACE CUMULATIVE MONTHLY DEPARTURE FROM NORMAL PRECIPITATION, IN INCHES

9

10

11

12

13

15

14

16

12

14

16

18

20

22

24

10

0

-10

-20

-40

-30

WELL 37N25W23ADAD, WHITE RIVER AQUIFER, TODD COUNTY

WELL 40N32W32BBBB, WHITE RIVER AQUIFER, MELLETTE COUNTY

Base Period 1961-90

1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
40 Water Resources of Mellette and Todd Counties, South Dakota

Figure 26. Hydrogeologic section D-D′ showing aquifers of Quaternary, Tertiary, and Cretaceous age in Mellette and Todd Counties. (The location of section D-D′ is shown in fig. 2.)

0246 MILES0246 KILOMETERS

2,8002,7002,6002,5002,4002,3002,2002,1002,0001,9001,8001,7001,6001,5001,400

FEET

D

D'

DATUM IS SEA LEVEL VERTICAL SCALE IS GREATLY EXAGGERATED

EXPLANATION

QUATERNARY UNCONSOLIDATED DEPOSITS

Alluvial aquiferTerrace deposit

Qa

Qt

CRETACEOUS SEDIMENTARY DEPOSITS

CONTACTTEST HOLE

Pierre Shale aquifer

Kp

TERTIARY SEDIMENTARY DEPOSITS

Ogallala aquiferWhite River aquifer

To

Tw

Kp

Kp

Kp

Kp

Qa

43N25W9CACA

43N25W32DDDD2

41N25W11DDDD

40N25W1AAAA

100N79W33CBBB

99N79W29DADD

38N25W1ACDD

37N25W2AAAA

37N25W12BBBB

37N25W24BCBB2

96N79W28BADB

95N79W16BAAB

35N25W13DADD3

Oak Creek

Keya Paha River

Sand Creek

Qa

Qt

Qa

Qt

Qt

To

Tw

Tw

To

To
Ground Water 41

Figure 27. Potentiometric surface of the Pierre Shale aquifer.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

Rosebud

Norris

Okreek

Mission Antelope

St. Francis

Parmelee

Wood

WHTE RIVER

T.

36

N.

T.

37

N.

T.

38

N.

T.

39

N.

T.

40

N.

T.

41

N.

T.

42

N.

T.

43

N.

T. 44 N.

T. 45 N.

T.

35

N.

43o

45'

43o

30'

43o

15'

R. 33 W. R. 32 W. R. 31 W.

101o

R. 27 W. R. 29 W. R. 28 W.

R. 30 W.

100o45' 100o30'

R. 26 W. R. 25 W.

100o15'

43o

00'

Sand

Creek

Crazy

Hole Cr

Keya

Paha River

Rock

Eagle

Creek

Creek

Antelope

Lake

Antelope

Antelope

Creek

Creek

Creek

Spring

Creek

Little

Spring

Creek

Beads Cr

White

Rosebud Cr

East

Br

Br

West

Soldier

Phister Creek

Cut

Cr

Gray

Cr

Meat

Creek

River

Black

Pipe

Creek

Larvie

Creek

Yakmi Creek

Cottonwood

Creek

Creek

North Branch Pine

South

Branch

White

River

Creek

White

Thunder

Creek

Kaiser

White Horse Cr

Chunker

Swimm er

Creek

Minnech aduza

Oak

Creek

Eagletail

83

18

18

83

63

63

44

44

53

BENNETTE COUNTY JACKSON COUNTY

JONES COUNTY

LYMAN COUNTY TRIPP COUNTY

White

Lake

2200

2100

2100

1900

1900

2000

2000

2200

2200

2000

1900

2000

2300

2300

2300

2100

2100

1900

2029

2284 2138

2141

2122 2195

2260

2099

2146

2045

2101

2195

2145

2188

2144

2144

2021

2000 2042 1980

2045

2115 2027

1888

2137 1997 2000

2018 2125

2150

2055

2054

2173

2246 2064

2124

2192 2132

2085

2227

2120 2096

2216

2213

2108

2049

2296

2156

2190 2055

2207

2173

2285

2288

2264 2309

2245

2240

2231

2264

2114 2094 2156

2195

2083 2128

2011

2029 2070

1895

1965

2092

1970 2068 1974

1810

2009

2109

1925

2030

2102 2034

1896 1947 1947 2317

1860

2225 2250

2176

2091 2030

2080

2275

2012

1988

2074

2277

2182

2327

2165

2205

2253

1982

2330

2029

2284 2138

2141

2122 2195

2260

2099

2146

2045

2101

2195

2145

2188

2144

2144

2021

2000 2042 1980

2045

2115 2027

1888

2137 1997 2000

2018 2125

2150

2055

2054

2173

2246 2064

2124

2192 2132

2085

2227

2120 2096

2216

2213

2108

2049

2296

2156

2190 2055

2207

2173

2285

2288

2264 2309

2245

2240

2231

2264

2114 2094 2156

2195

2083 2128

2011

2029 2070

1895

1965

2092

1970 2068 1974

1810

2009

2109

1925

2030

2102 2034

1896 1947 1947 2317

1860

2225 2250

2176

2091 2030

2080

2275

2012

1988

2074

2277

2182

2327

2165

2205

2253

1982

2330

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base from U.S. Geological Survey

digital data 1:100,000

EXPLANATION

APPROXIMATE AREA UNDERLAIN BY THE PIERRE SHALE AQUIFER (modified from Ellis and others, 1971)

POTENTIOMETRIC CONTOUR--Shows altitude at which water would have stood in tightly cased, ninpumping

 wells in 1996. Dashed where inferred. Contour interval 100 feet. Datum is sea level.

WELL--Number is altitude of water level, in feet above sea level 2912

2300

GENERAL DIRECTION OF GROUND-WATER FLOW
42 Water Resources of Mellette and Todd Counties, South Dakota

Recharge to the Pierre Shale aquifer primarily is 

by infiltration of precipitation on the outcrops of the 

Pierre Shale (fig. 4). The greatest recharge to the 

aquifer occurs during the spring after snowmelt and 

during storm events. Infiltration rates generally are less 

than the lowest rate (0.06 inches/hour) measured by the 

U.S. Soil Conservation Service (1974, 1975). Discharge from the aquifer is through withdrawals from 

domestic and stock wells and by evapotranspiration 

where the aquifer is at or near land surface.

Based on modified slug tests conducted at a site 

in central South Dakota, the horizontal hydraulic conductivity of the unweathered Pierre Shale aquifer 

ranges from about 10-5 to 10-6 feet per day (Bredehoeft 

and others, 1983). Bredehoeft and others (1983) 

suggested that the hydraulic conductivity of the Pierre 

Shale aquifer decreases with depth, and that much of 

the flow in the shale occurs through fractures.

Dakota Sandstone Aquifer

The Dakota Sandstone aquifer underlies the 

entire study area and contains more than an estimated 

81 million acre-feet of water in storage. However, only 

a few test holes and wells penetrate the Dakota Sandstone in the study area, and all but two were drilled in 

Mellette County. The Dakota Sandstone consists of 

interbedded sandstones and shales. The depth to the 

top of the aquifer ranges from 1,270 to 2,348 feet below 

land surface (table 4). Because the formation is overlain by at least five formations primarily composed of 

shale (table 1), the aquifer is under confined conditions, 

and wells completed in the Dakota Sandstone aquifer 

are likely to flow when drilled in topographically low 

areas, such as near streams. Known flowing wells completed in the Dakota Sandstone aquifer are located at 

42N28W22, 43N27W14, and 43N27W3. Reported 

yields from the aquifer range from 10 to 100 gallons 

per minute (table 4).

The potentiometric surface was not constructed 

for the Dakota Sandstone aquifer because of insufficient data. Regional potentiometric maps of the aquifer 

(Schoon, 1971) approximate the hydraulic head altitude to range from 2,150 feet above sea level along the 

western boundary of Mellette and Todd Counties to 

1,950 feet along the eastern boundary. The contours 

generally trend north-south; therefore, the general 

direction of ground-water flow in the Dakota Sandstone 

aquifer is from west to east in the study area.

Records of long-term water-level fluctuations in 

wells completed in the Dakota Sandstone aquifer 

located at 41N26W30DDCB and 43N30W8BBCD in 

Mellette County (fig. 28) correlate poorly with longterm precipitation data. Water levels in the two observation wells have declined 31 to 50 feet since 1963 

because discharge has exceeded recharge.

The major sources of recharge to the Dakota 

Sandstone aquifer are infiltration of precipitation on 

outcrops of the Dakota Sandstone (mostly in the Black 

Hills area) and leakage from other aquifers (Schoon, 

1971; Miller and Rahn, 1974). Discharge from the 

aquifer in the study area is through withdrawals from 

stock wells. 

Miller and Rahn (1974) reported a hydraulic 

conductivity from a single-well aquifer test at Box 

Elder, South Dakota, of about 1 foot per day and a 

transmissivity of about 200 square feet per day for the 

Dakota Sandstone. Bredehoeft and others (1983) 

calculated an average hydraulic conductivity of about 

5 feet per day from approximately 500 drilling records 

in South Dakota. 

Inyan Kara Aquifer

The extent of the Inyan Kara Group in the study 

area is not known. The only test holes and wells that 

penetrate the Inyan Kara Group are located in northern 

Mellette County. The depth to the top of the Inyan Kara 

Group is greater than 1,900 feet below land surface 

(table 4). The Inyan Kara Group consists predominantly of sandstones and siltstones containing loose to 

well-cemented sand. Because the formation is overlain 

by the Dakota Sandstone and five shale formations 

(table 1), the aquifer is confined, and wells completed 

in this aquifer are likely to flow when drilled in topographically low areas. Known flowing wells completed in the aquifer are located in Mellette County in 

42N28W22, 42N30W12, 43N26W33, and 

45N32W36. Reported yields from the aquifer range 

from 9 to 160 gallons per minute (table 4).

The potentiometric surface was not constructed 

for the Inyan Kara aquifer because of insufficient 

water-level data. The potentiometric surface of the 

Inyan Kara aquifer in northern Mellette County is presented in Ellis and others (1971). The altitude of the 

potentiometric surface ranges from 2,250 feet above 

sea level in northwestern Mellette County to 2,150 feet 

in central Mellette County. The potentiometric contours generally trend east-west; therefore, the general 

direction of ground-water flow in the aquifer is from 

north to south (Ellis and others, 1971). No long-term 

water-level records were available for wells completed 

in the Inyan Kara aquifer in either Mellette or Todd 

County.
Ground Water 43

Figure 28. Water-level fluctuations in the Dakota Sandstone aquifer and cumulative monthly departure from normal 

precipitation at Valentine, Nebraska. WATER LEVEL, IN FEET BELOW LAND SURFACE CUMULATIVE MONTHLY DEPARTURE FROM NORMAL PRECIPITATION, IN INCHES

155

160

165

170

175

185

180

190

90

100

110

120

130

140

150

10

0

-10

-20

-40

-30

WELL 41N26W30DDCB, DAKOTA SANDSTONE AQUIFER, MELLETTE COUNTY

WELL 43N30W8BBCD, DAKOTA SANDSTONE AQUIFER, MELLETTE COUNTY

Base Period 1961-90

1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990
44 Water Resources of Mellette and Todd Counties, South Dakota

The major source of recharge to the aquifer is by 

infiltration of precipitation on outcrops of the Inyan 

Kara Group (mostly in the Black Hills area), groundwater inflow mostly from Wyoming and North Dakota, 

and leakage from underlying units (Case, 1984). 

Discharge from the Inyan Kara aquifer in the study area 

is through withdrawals from stock wells. 

No specific-capacity or aquifer-test data were 

available for wells completed in the Inyan Kara aquifer 

in or near the study area. Aquifer properties of 

hydraulic conductivity and transmissivity possibly are 

similar to those in the Dakota Sandstone aquifer based 

on conductivity values compiled by Case (1984).

Minnelusa and Madison Aquifers

The Minnelusa Formation and Madison Limestone are combined for purposes of this report because 

almost all wells at this depth are completed in both the 

Minnelusa and Madison aquifers. The extent of the 

Minnelusa and Madison Formations in the study area is 

not known. The Minnelusa Formation consists primarily of interbedded sandstone, siltstone, limestone, 

dolomite, anhydrite, and shale. The composition of the 

Madison Limestone varies from pure limestone to pure 

dolomite with combinations of the two. The aquifers 

are confined because they are overlain by many confining deposits. Wells completed in the Minnelusa and/or 

the Madison aquifers are likely to flow when drilled in 

topographically low areas. Known flowing wells are 

located in Mellette County at 42N28W22, 42N28W30, 

42N25W32, and 42N26W34. Yields from the aquifers 

range from 25 to 40 gallons per minute (table 4).

The major source of recharge to the Minnelusa 

and Madison aquifers is infiltration of precipitation and 

streamflow on outcrops of the these formations in the 

Black Hills area (Peter, 1985). Discharge from the 

aquifers in the study area is through withdrawals from 

stock wells and leakage to other aquifers (Case, 1984). 

The potentiometric surface for the Minnelusa 

and Madison aquifers was not drawn because of insufficient water-level data. Ellis and others (1971) 

approximate the potentiometric surface of the 

Minnelusa and Madison aquifers throughout most of 

Mellette County. The altitude of the potentiometric 

surface in Mellette County ranges from 2,400 feet 

above sea level in the northwest to 2,150 feet in the 

southeast. The general trend of the contours is southwest-northeast; therefore, the general direction of 

ground-water flow in the aquifers is from the northwest 

to the southeast (Ellis and others, 1971). No long-term 

water-level measurements were available for either 

aquifer in the study area. 

Although the hydraulic properties of the 

Minnelusa and Madison aquifers have been studied 

extensively in the Black Hills area, no known information exists for these aquifers in areas in or near the 

study area. Because the hydraulic properties determined in the Black Hills would not be comparable to 

those in this study area due to the uplift and karstification in the Black Hills, no hydraulic properties are 

given in this report for the Minnelusa and Madison 

aquifers.

Water Quality

The chemical quality of water in the aquifers in 

the study area varies widely, both within and between 

aquifers. The chemical quality among the aquifers of 

Tertiary age is the most similar. A summary of chemical analyses of water for each aquifer, based on data 

stored in the USGS NWIS water-quality database, is 

presented in table 5.

In the following discussions, hardness and 

salinity are used to characterize the quality of water 

from the aquifers. Water that has a hardness less than 

61 mg/L (milligrams per liter) is considered soft; 61 to 

120 mg/L, moderately hard; 121 to 180 mg/L, hard; 

and more than 180 mg/L, very hard (Heath, 1983). 

Salinity is based on the dissolved solids concentrations. 

Water that has a dissolved solids concentration less 

than 1,000 mg/L is considered fresh; 1,000 to 

3,000 mg/L, slightly saline; 3,000 to 10,000 mg/L, 

moderately saline; 10,000 to 35,000 mg/L, very saline; 

and more than 35,000 mg/L, briny (Heath, 1983).

The quality of water in the alluvial aquifers 

varies greatly between locations and is dependant on 

the deposits that underlie the unconsolidated deposits. 

The alluvial aquifers generally yield water that has low 

concentrations of dissolved solids, is fresh, and is soft 

to moderately hard where underlain by the Ogallala and 

Arikaree Formations; has moderate concentrations of 

dissolved solids, is slightly saline, and is hard where 

underlain by the White River Group; and has high concentrations of dissolved solids, is slightly saline, and is 

very hard where underlain by the Pierre Shale. 

Because of this variation, calcium and bicarbonate 

generally are the dominant species in the alluvial water 

where underlain by the deposits of Tertiary age, and 

sodium and chloride generally are the dominant species 

where underlain by the Pierre Shale (fig. 29).
Ground Water 45

Table 5. Summary of chemical analyses for ground water

[Results based on data stored in USGS NWIS water-quality database. Results in milligrams per liter except as indicated. One milligram 

per liter (mg/L) is approximately equal to one part per million. One microgram per liter (μg/L) is approximately equal to one part per billion; μS/cm, microsiemens per centimeter at 25° Celsius; --, not analyzed or not determined; <, less than indicated detection limit;

ND, specifically analyzed for but not detected, and detection limit unknown]

Property or

dissolved constituent

Alluvial aquifers

Number of

samples Mean Median Minimum Maximum

Specific conductance (μS/cm) 46 1,580 1,210 229 4,600

pH (standard units) 51 7.3 7.5 6.6 8.3

Carbon dioxide 20 12 9.9 1.7 24

Hardness, as CaCO3 52 518 273 77 2,060

Solids, residue at 180° C 48 1,140 724 175 3,820

Solids, sum of constituents 43 1,200 1,040 177 3,440

Calcium 52 156 94 25 527

Magnesium 52 31 14 2 196

Sodium 50 152 81 8.1 570

Potassium 47 14 13 6.5 33

Bicarbonate 26 326 317 117 600

Alkalinity 25 323 318 107 668

Sulfate 52 478 194 ND 2,000

Chloride 52 28 13 ND 160

Fluoride 49 0.5 0.4 0.1 4

Silica 36 33 31 12 60

Nitrogen, nitrate 40 1.0 0.3 ND 9.2

Phosphorus, orthophosphate 11 0.04 0.04 ND 0.12

Aluminum (μg/L) 4 -- <5 <5 7.5

Arsenic (μg/L) 17 13 7 <1 44

Barium (μg/L) 5 127 124 12 330

Boron (μg/L) 17 409 354 20 940

Cadmium (μg/L) 9 -- <1 <1 2.4

Chromium (μg/L) 9 -- <1 <1 <10

Cobalt (μg/L) 0 -- -- -- --

Copper (μg/L) 6 6.2 <1 4.5 18

Iron (μg/L) 29 627 60 ND 3,200

Lead (μg/L) 9 -- <1 <1 2

Lithium (μg/L) 0 -- -- -- --

Manganese (μg/L) 23 597 250 <1 4,400

Mercury (μg/L) 7 -- <1 <1 <1

Molybdenum (μg/L) 3 2.4 2 1.8 3.4

Nickel (μg/L) 0 -- -- -- --

Selenium (μg/L) 16 7.7 2 <1 60

Silver (μg/L) 2 -- 31 <1 60

Strontium (μg/L) 0 -- -- -- --

Vanadium (μg/L) 3 2.1 2.1 1.1 3.2

Zinc (μg/L) 9 38 29 <3 120
46 Water Resources of Mellette and Todd Counties, South Dakota

Table 5. Summary of chemical analyses for ground water—Continued

Property or

dissolved constituent

Ogallala aquifer

Number of

samples Mean Median Minimum Maximum

Specific conductance (μS/cm) 150 397 361 227 911

pH (standard units) 157 7.5 7.5 6.8 8.4

Carbon dioxide 93 10 8.6 0.8 33

Hardness, as CaCO3 143 171 164 21 415

Solids, residue at 180° C 70 280 256 180 619

Solids, sum of constituents 126 237 210 134 632

Calcium 143 55 52 7.3 130

Magnesium 143 8.0 8.0 ND 42

Sodium 142 12 6.0 ND 180

Potassium 139 8.6 8.0 1.0 24

Bicarbonate 102 217 215 109 453

Alkalinity 41 183 174 129 340

Sulfate 142 9.2 4.0 ND 145

Chloride 147 7.0 3.6 ND 220

Fluoride 54 0.4 0.3 0.2 4.6

Silica 45 60 59 50 73

Nitrogen, nitrate 92 5.5 1.3 <0.1 44

Phosphorus, orthophosphate 28 0.06 0.02 <0.01 2.3

Aluminum (μg/L) 2 -- <5 <5 <5

Arsenic (μg/L) 20 4.8 3.8 1.0 12

Barium (μg/L) 8 166 115 98 360

Boron μg/L) 30 94 40 ND 780

Cadmium (μg/L) 8 -- <1 <1 3.5

Chromium (μg/L) 8 1.0 1.0 <1 2.9

Cobalt (μg/L) 0 -- -- -- --

Copper (μg/L) 3 4.0 5.0 ND 7.0

Iron (μg/L) 47 40 8 <0.1 320

Lead (μg/L) 8 2.7 1.0 <1 13

Lithium (μg/L) 0 -- -- -- --

Manganese (μg/L) 29 2 0.3 <1 20

Mercury (μg/L) 4 -- <0.1 <0.1 <0.1

Molybdenum (μg/L) 0 -- -- -- --

Nickel (μg/L) 0 -- -- -- --

Selenium (μg/L) 23 1.2 <1 <1 10

Silver (μg/L) 4 -- <1 <1 <2

Strontium (μg/L) 0 -- -- -- --

Vanadium (μg/L) 0 -- -- -- --

Zinc (μg/L) 6 24 20 12 54
Ground Water 47

Table 5. Summary of chemical analyses for ground water—Continued

Property or

dissolved constituent

Arikaree aquifer

Number of

samples Mean Median Minimum Maximum

Specific conductance (μS/cm) 68 510 425 238 1,730

pH (standard units) 80 7.6 7.6 7.1 8.5

Carbon dioxide 20 7.9 6.9 2.2 25

Hardness, as CaCO3 73 104 91 10 499

Solids, residue at 180° C 67 357 300 172 1,200

Solids, sum of constituents 67 347 299 140 1,180

Calcium 78 34 31 3.6 170

Magnesium 78 4.0 2.9 ND 19

Sodium 74 68 66 4.1 170

Potassium 71 11 10 1.1 26

Bicarbonate 44 243 234 122 587

Alkalinity 52 211 192 109 534

Sulfate 75 31 20 ND 170

Chloride 77 9.6 3.9 <0.1 110

Fluoride 58 0.7 0.5 <0.1 3.1

Silica 57 64 65 31 77

Nitrogen, nitrate 45 2.1 1.1 <0.05 39

Phosphorus, orthophosphate 26 0.24 0.09 0.007 1.1

Aluminum (μg/L) 7 -- <5 <5 39

Arsenic (μg/L) 46 29 13 2 110

Barium (μg/L) 3 110 140 39 150

Boron μg/L) 25 141 105 30 630

Cadmium (μg/L) 26 -- <1 <1 <1

Chromium (μg/L) 26 0.7 <1 <1 2

Cobalt (μg/L) 0 -- -- -- --

Copper (μg/L) 23 4.1 2 <1 17

Iron (μg/L) 51 24 <3 ND 230

Lead (μg/L) 26 -- <1 <1 2.0

Lithium (μg/L) 0 -- -- -- --

Manganese (μg/L) 44 31 7 ND 500

Mercury (μg/L) 25 -- <0.1 <0.1 0.6

Molybdenum (μg/L) 15 2.2 1.4 <1.0 5.3

Nickel (μg/L) 0 -- -- -- --

Selenium (μg/L) 42 1.7 1.0 <1.0 20

Silver (μg/L) 0 -- -- -- --

Strontium (μg/L) 0 -- -- -- --

Vanadium (μg/L) 15 25 12 6 150

Zinc (μg/L) 26 71 11 <3 960
48 Water Resources of Mellette and Todd Counties, South Dakota

Table 5. Summary of chemical analyses for ground water—Continued

Property or

dissolved constituent

White River aquifer

Number of

samples Mean Median Minimum Maximum

Specific conductance (μS/cm) 22 1,010 764 296 3,280

pH (standard units) 22 7.2 7.4 6.7 8.0

Carbon dioxide 3 12 11 7.1 16

Hardness, as CaCO3 20 187 137 19 1,130

Solids, residue at 180° C 20 659 471 211 2,450

Solids, sum of constituents 19 653 466 215 2,310

Calcium 20 64 46 6.4 360

Magnesium 20 6.7 3.6 0.1 55

Sodium 20 154 103 5.1 650

Potassium 20 9.6 9.1 1.4 20

Bicarbonate 10 309 316 161 469

Alkalinity 17 310 288 137 589

Sulfate 20 97 17 <1 1,300

Chloride 20 93 9.8 1 860

Fluoride 20 0.5 0.4 <0.1 1.7

Silica 20 42 45 11 65

Nitrogen, nitrate 18 1.5 0.7 <0.005 7.6

Phosphorus, orthophosphate 13 0.2 0.05 0.02 0.8

Aluminum (μg/L) 3 -- <5 <5 8.3

Arsenic (μg/L) 9 6.5 7 <1 14

Barium (μg/L) 2 195 195 120 270

Boron μg/L) 10 784 110 20 2,170

Cadmium (μg/L) 2 -- <1 <1 1

Chromium (μg/L) 2 -- 1.5 <1 2

Cobalt (μg/L) 0 -- -- -- --

Copper (μg/L) 0 -- -- -- --

Iron (μg/L) 9 32 11 <3 92

Lead (μg/L) 2 -- <1 <1 <1

Lithium (μg/L) 0 -- -- -- --

Manganese (μg/L) 9 98 9 <1 810

Mercury (μg/L) 2 -- <0.1 <0.1 <0.1

Molybdenum (μg/L) 0 -- -- -- --

Nickel (μg/L) 0 -- -- -- --

Selenium (μg/L) 9 1.2 <1 <1 5

Silver (μg/L) 0 -- -- -- --

Strontium (μg/L) 0 -- -- -- --

Vanadium (μg/L) 0 -- -- -- --

Zinc (μg/L) 2 7.5 7.5 4 11
Ground Water 49

Table 5. Summary of chemical analyses for ground water—Continued

Property or

dissolved constituent

Pierre Shale aquifer

Number of

samples Mean Median Minimum Maximum

Specific conductance (μS/cm) 21 2,350 1,740 530 6,200

pH (standard units) 21 7.0 7.1 6.6 8.0

Carbon dioxide 2 9.2 9.2 7.3 11

Hardness, as CaCO3 24 739 484 25 2,230

Solids, residue at 180° C 24 1,870 1,380 336 5,990

Solids, sum of constituents 20 1,720 1,170 331 4,940

Calcium 24 216 160 7.6 582

Magnesium 24 49 27 0.9 280

Sodium 24 277 190 13 830

Potassium 21 15 12 4.3 33

Bicarbonate 2 368 368 278 457

Alkalinity 19 335 326 122 550

Sulfate 24 886 565 <1 3,000

Chloride 24 93 34 4.5 790

Fluoride 24 0.6 0.4 <0.1 2.5

Silica 21 23 21 11 45

Nitrogen, nitrate 23 4.1 0.7 <0.1 40

Phosphorus, orthophosphate 5 0.05 0.02 0.01 0.12

Aluminum (μg/L) 0 -- -- -- --

Arsenic (μg/L) 5 -- <1 <1 5

Barium (μg/L) 5 87 27 18 280

Boron μg/L) 2 195 195 130 260

Cadmium (μg/L) 5 -- <1 <1 2

Chromium (μg/L) 5 -- <1 <1 2

Cobalt (μg/L) 0 -- -- -- --

Copper (μg/L) 0 -- -- -- --

Iron (μg/L) 6 319 60 5 1,700

Lead (μg/L) 5 -- <1 <1 <1

Lithium (μg/L) 0 -- -- -- --

Manganese (μg/L) 7 188 100 <1 500

Mercury (μg/L) 5 -- <0.1 <0.1 <0.1

Molybdenum (μg/L) 0 -- -- -- --

Nickel (μg/L) 0 -- -- -- --

Selenium (μg/L) 6 4.7 3.5 <1 10

Silver (μg/L) 0 -- -- -- --

Strontium (μg/L) 0 -- -- -- --

Vanadium (μg/L) 0 -- -- -- --

Zinc (μg/L) 5 171 55 10 390
50 Water Resources of Mellette and Todd Counties, South Dakota

Table 5. Summary of chemical analyses for ground water—Continued

Property or

dissolved constituent

Dakota Sandstone aquifer

Number of

samples Mean Median Minimum Maximum

Specific conductance (μS/cm) 15 2,880 2,780 2,440 4,080

pH (standard units) 13 7.7 7.7 7.1 8.6

Carbon dioxide 7 27 12 4 107

Hardness, as CaCO3 13 92 43 19 400

Solids, residue at 180° C 12 1,910 1,890 1,450 2,900

Solids, sum of constituents 12 1,870 1,870 1,450 2,780

Calcium 13 27 13 6 130

Magnesium 13 6 2 1 19

Sodium 13 640 650 390 970

Potassium 13 12 11 7 20

Bicarbonate 11 700 670 260 1,000

Alkalinity 1 303 303 303 303

Sulfate 13 652 620 120 1,200

Chloride 13 170 100 39 440

Fluoride 11 3 4 2 5

Silica 11 23 22 12 30

Nitrogen, nitrate 8 0.07 <0.1 ND 0.25

Phosphorus, orthophosphate 2 -- 0.02 <0.01 0.03

Aluminum (μg/L) 1 10 10 10 10

Arsenic (μg/L) 2 -- <1 <1 <1

Barium (μg/L) 2 -- <100 <100 <100

Boron μg/L) 10 3,100 3,300 510 5,000

Cadmium (μg/L) 2 -- <1 <1 <1

Chromium (μg/L) 2 -- <1 <1 <1

Cobalt (μg/L) 1 -- ND ND ND

Copper (μg/L) 1 -- ND ND ND

Iron (μg/L) 6 330 80 20 1,500

Lead (μg/L) 2 -- <1 <1 <1

Lithium (μg/L) 1 170 170 170 170

Manganese (μg/L) 5 -- ND ND 130

Mercury (μg/L) 1 <0.1 <0.1 <0.1 <0.1

Molybdenum (μg/L) 1 <1 <1 <1 <1

Nickel (μg/L) 1 -- ND ND ND

Selenium (μg/L) 3 -- <1 <1 10

Silver (μg/L) 1 -- ND ND ND

Strontium (μg/L) 1 530 530 530 530

Vanadium (μg/L) 1 15 15 15 15

Zinc (μg/L) 2 -- <20 <20 <20
Ground Water 51

Table 5. Summary of chemical analyses for ground water—Continued

Property or

dissolved constituent

Inyan Kara aquifer

Number of

samples Mean Median Minimum Maximum

Specific conductance (μS/cm) 3 4,130 4,320 2,480 5,590

pH (standard units) 3 7.5 7.9 7.2 7.9

Carbon dioxide 3 15 15 13 18

Hardness, as CaCO3 3 473 160 130 870

Solids, residue at 180° C 3 3,090 3,060 2,140 4,070

Solids, sum of constituents 3 2,940 3,000 1,960 3,860

Calcium 3 136 51 18 340

Magnesium 3 34 7.1 3.2 93

Sodium 3 824 1,050 131 1,290

Potassium 3 16 17 9.8 20

Bicarbonate 3 580 740 130 870

Alkalinity 3 478 607 108 718

Sulfate 3 1,400 1,300 1,100 1,800

Chloride 3 207 180 180 260

Fluoride 3 3.7 3.9 2.8 4.4

Silica 3 30 30 28 32

Nitrogen, nitrate 3 0.2 0.1 0.1 0.4

Phosphorus, orthophosphate 0 -- -- -- --

Aluminum (μg/L) 0 -- -- -- --

Arsenic (μg/L) 0 -- -- -- --

Barium (μg/L) 0 -- -- -- --

Boron μg/L) 3 1,437 1,900 210 2,200

Cadmium (μg/L) 0 -- -- -- --

Chromium (μg/L) 0 -- -- -- --

Cobalt (μg/L) 0 -- -- -- --

Copper (μg/L) 0 -- -- -- --

Iron (μg/L) 3 2,733 1,300 1200 5,700

Lead (μg/L) 0 -- -- -- --

Lithium (μg/L) 0 -- -- -- --

Manganese (μg/L) 3 183 140 140 270

Mercury (μg/L) 0 -- -- -- --

Molybdenum (μg/L) 0 -- -- -- --

Nickel (μg/L) 0 -- -- -- --

Selenium (μg/L) 1 ND ND ND ND

Silver (μg/L) 0 -- -- -- --

Strontium (μg/L) 0 -- -- -- --

Vanadium (μg/L) 0 -- -- -- --

Zinc (μg/L) 0 -- -- -- --
52 Water Resources of Mellette and Todd Counties, South Dakota

Table 5. Summary of chemical analyses for ground water—Continued

Property or

dissolved constituent

Minnelusa and Madison aquifers

Number of

samples Mean Median Minimum Maximum

Specific conductance (μS/cm) 2 2,060 2,060 1,510 2,610

pH (standard units) 2 7.2 7.2 7.1 7.3

Carbon dioxide 0 -- -- -- --

Hardness, as CaCO3 3 970 810 800 1,300

Solids, residue at 180° C 3 1,560 1,270 1,190 2,220

Solids, sum of constituents 3 1,440 1,170 1,160 1,990

Calcium 3 287 250 240 370

Magnesium 3 63 48 47 94

Sodium 3 60 35 27 119

Potassium 3 15 13 11 21

Bicarbonate 3 143 140 140 150

Alkalinity 3 118 114 114 125

Sulfate 3 817 680 670 1,100

Chloride 3 104 42 40 230

Fluoride 3 1.5 1.7 1.0 1.7

Silica 3 34 39 24 40

Nitrogen, nitrate 2 -- 0.3 ND 0.5

Phosphorus, orthophosphate 1 <0.01 <0.01 <0.01 <0.01

Aluminum (μg/L) 1 20 20 20 20

Arsenic (μg/L) 1 3 3 3 3

Barium (μg/L) 1 <100 <100 <100 <100

Boron μg/L) 3 140 170 70 180

Cadmium (μg/L) 1 <2 <2 <2 <2

Chromium (μg/L) 1 ND ND ND ND

Cobalt (μg/L) 0 -- -- -- --

Copper (μg/L) 1 ND ND ND ND

Iron (μg/L) 3 2,413 890 450 5,900

Lead (μg/L) 1 3 3 3 3

Lithium (μg/L) 1 60 60 60 60

Manganese (μg/L) 3 90 50 30 190

Mercury (μg/L) 1 3.4 3.4 3.4 3.4

Molybdenum (μg/L) 1 3 3 3 3

Nickel (μg/L) 0 -- -- -- --

Selenium (μg/L) 1 <1 <1 <1 <1

Silver (μg/L) 0 -- -- -- --

Strontium (μg/L) 1 4,600 4,600 4,600 4,600

Vanadium (μg/L) 0 -- -- -- --

Zinc (μg/L) 1 330 330 330 330
Ground Water 53

Figure 29. Trilinear diagrams showing proportional concentrations of major ions in ground-water samples.

Calcium + Magnesium

Sulfate

Sodium + Potassium

Chloride + Fluoride + Nitrate + Sulfate

Bicarbonate + Carbonate

Magnesium

Calcium Chloride + Fluoride + Nitrate

80

60

40

20

80

80

60

40

20

20

20

40

60

80

40

60

80

60

40

20

20

80

60

40

20

40

60

80

80

60

40

20

WHITE RIVER AQUIFER

Calcium + Magnesium

Sulfate

Sodium + Potassium

Chloride + Fluoride + Nitrate + Sulfate

Bicarbonate + Carbonate

Magnesium

Calcium Chloride + Fluoride + Nitrate

80

60

40

20

80

80

60

40

20

20

2040

60

80

40

60

80

60

40

20

20

80

60

40

20

40

60

80

80

60

40

20

PIERRE SHALE AQUIFER

Calcium + Magnesium

Sulfate

Sodium + Potassium

Chloride + Fluoride + Nitrate + Sulfate

Bicarbonate + Carbonate

Magnesium

Calcium Chloride + Fluoride + Nitrate

80

60

40

20

80

80

60

40

20

20

20

40

60

80

40

60

80

60

40

20

20

80

60

40

20

40

60

80

80

60

40

20

DAKOTA SANDSTONE AQUIFER

Calcium + Magnesium

Sulfate

Sodium + Potassium

Chloride + Fluoride + Nitrate + Sulfate

Bicarbonate + Carbonate

Magnesium

Calcium Chloride + Fluoride + Nitrate

80

60

40

20

80

80

60

40

20

20

20

40

60

80

40

60

80

60

40

20

20

80

6040

20

40

60

80

80

60

40

20

ALLUVIAL AQUIFERS

Calcium + Magnesium

Sulfate

Sodium + Potassium

Chloride + Fluoride + Nitrate + Sulfate

Bicarbonate + Carbonate

Magnesium

Calcium Chloride + Fluoride + Nitrate

80

60

40

20

80

80

60

40

20

20

20

40

60

80

40

60

80

60

40

20

20

80

60

40

20

40

60

80

80

60

40

20

OGALLALA AQUIFER

Calcium + Magnesium

Sulfate

Sodium + Potassium

Chloride + Fluoride + Nitrate + Sulfate

Bicarbonate + Carbonate

Magnesium

Calcium Chloride + Fluoride + Nitrate

80

60

40

20

80

80

60

40

20

20

20

40

60

80

40

60

80

60

40

20

20

80

60

40

20

40

60

80

80

60

40

20

ARIKAREE AQUIFER

Number of samples = 49 Number of samples = 20

Number of samples =134 Number of samples = 23

Number of samples = 73 Number of samples = 12
54 Water Resources of Mellette and Todd Counties, South Dakota

The Ogallala aquifer is a calcium-bicarbonate 

water type, and the Arikaree aquifer is a calcium 

sodium bicarbonate water type (fig. 29). Generally, the 

Ogallala and Arikaree aquifers yield water that has low 

concentrations of dissolved solids, is fresh, and is soft 

to moderately hard. The dominant species in the White 

River aquifer generally are calcium, sodium, and bicarbonate (fig. 29). The water quality of the White River 

aquifer varies and is dependent on depth and proximity 

of the aquifer to the Pierre Shale. Like the alluvial 

aquifers, the closer the water-bearing deposits of the 

White River Group are to the Pierre Shale, the higher in 

dissolved solids concentrations, more saline, and 

harder the water.

The bedrock aquifers generally yield hard, saline 

water with high concentrations of dissolved solids. The 

dominant species in the Pierre Shale aquifer vary from 

calcium to sodium and from bicarbonate to sulfate 

(fig. 29). In the Dakota Sandstone aquifer, the dominant species generally are sodium and sulfate (fig. 29). 

The Dakota Sandstone aquifer generally is the only 

bedrock aquifer that yields soft to moderately hard 

water with a mean concentration of 92 mg/L (table 5). 

Water from all other bedrock aquifers generally is hard 

to very hard with means ranging from 473 to 970 mg/L 

(table 5). The water type of the Inyan Kara aquifer generally is a sodium or calcium sulfate type and the water 

type of the Minnelusa and Madison aquifer generally is 

a calcium sulfate type (Ellis and others, 1971). 

Although the concentrations of dissolved solids in the 

Minnelusa and Madison aquifers are lower than the 

other bedrock aquifers, the water is very hard ranging 

from 800 to 1,300 mg/L (table 5).

Boxplots are presented in figure 30 for the alluvial, Ogallala, Arikaree, White River, and Pierre Shale 

aquifers for each of the constituents listed in table 5 that 

had a minimum of 10 analyses in samples from at least 

two aquifers. The Inyan Kara, Minnelusa, and Madison 

aquifers were not included in the boxplots because the 

maximum number of analyses for each constituent was 

three. The boxplots not only show the variations of the 

constituents within each aquifer, but also allow a comparison of the general water-quality characteristics 

between the aquifers. For example, the highest nitrate 

concentrations were detected in the Ogallala aquifer 

and the highest arsenic concentrations in the Arikaree 

aquifer.

The significance of the chemical and physical 

properties of water and, if applicable, the U.S. 

Environmental Protection Agency (USEPA) 

Maximum Contaminant Level (MCL) and Secondary 

Maximum Contaminant Level (SMCL) are presented 

in table 6 and shown in figure 30. The MCL’s are 

established for contaminants that, if present in drinking 

water, may cause adverse human health effects; MCL’s 

are enforceable health-based standards (U.S. 

Environmental Protection Agency, 1994a). The 

SMCL’s are established for contaminants that can 

adversely affect the odor or appearance of water and 

result in discontinuation of use of the water; SMCL’s 

are nonenforceable, generally non-health-based 

standards that are related to the aesthetics of water use 

(U.S. Environmental Protection Agency, 1994a).

Water samples collected from wells completed in 

alluvial aquifers exceeded the USEPA MCL’s for the 

following regulated constituents: 1 sample out of 49 

analyzed for fluoride exceeded the MCL of 4.0 mg/L, 

and 1 sample out of 16 analyzed for selenium exceeded 

the MCL of 50 μg/L (micrograms per liter). The 

median concentrations for dissolved solids and manganese exceeded the SMCL’s for these constituents. 

Almost one-half of the samples collected from alluvial 

wells exceeded the SMCL for sulfate and about onethird exceeded the SMCL for iron.

Two constituents analyzed in samples collected 

from the Ogallala aquifer exceeded the respective 

MCL’s: 1 sample out of 54 exceeded the fluoride MCL, 

and 13 samples out of 92 exceeded the nitrate MCL of 

10 mg/L. Only a few samples exceeded the SMCL’s 

for dissolved solids (5 out of 70 samples) and iron 

(1 out of 48 samples). The Rosebud Sioux Tribe 

reported high nitrate concentrations in the Ogallala 

aquifer in a small area of Todd County (Huq, 1989). 

An investigation of ground-water quality, with 

emphasis on nitrate concentrations, in shallow aquifers 

(including the Ogallala, Arikaree, and White River 

aquifers) in parts of Mellette and Todd County was 

conducted by Hammond (1994). This investigation 

concluded that both point and non-point sources of 

contamination were impacting the ground water in 

Todd County, and that point sources of contamination 

were impacting the ground water in Mellette County. 

The USGS also investigated nitrate concentrations in a 

small area of Todd County that had high concentrations 

in the Ogallala aquifer; the data from this investigation 

is presented by Carter (1997).
Ground Water 55

Figure 30. Boxplots of chemical constituents in ground-water samples.

7,000

6,500

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

5,500

6,000

SPECIFIC CONDUCTANCE,

IN MICROSIEMENS PER CENTIMETER

46 150 68 22 21 15 52 143 73 20 24 13

51 157 80 22 21 13 43 126 67 19 20 12

20 93 20 3 2 7

2,400

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

2,200

HARDNESS,

IN MILLIGRAMS PER LITER

6.4

6.6

6.8

7.0

7.2

7.4

7.6

7.8

7.9

8.0

8.2

8.4

8.6

pH, IN STANDARD UNITS

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

5,500

SOLIDS, SUM OF CONSTITUENTS,

IN MILLIGRAMS PER LITER

Alluvial Ogallala Arikaree White River Pierre

Shale

Dakota

Sandstone

Pierre

Shale

Dakota

Sandstone

AQUIFER

120

0

10

20

30

40

50

60

70

80

90

100

110

CARBON DIOXIDE,

IN MILLIGRAMS PER LITER

Alluvial Ogallala Arikaree White River

AQUIFER

48 70 67 20 24 13

6,500

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

5,500

6,000

SOLIDS, RESIDUE AT 180¡ C,

IN MILLIGRAMS PER LITER
56 Water Resources of Mellette and Todd Counties, South Dakota

Figure 30. Boxplots of chemical constituents in ground-water samples.--Continued

650

600

0

50

100

150

200

250

300

350

400

450

500

550

CALCIUM,

IN MILLIGRAMS PER LITER

52 143 78 20 24 13 47 139 71 20 21 13

52 143 78 20 24 13 26 102 44 10 2 11

50 142 74 20 24 13

2,400

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

2,200

POTASSIUM,

IN MILLIGRAMS PER LITER

0

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

MAGNESIUM,

IN MICROGRAMS PER LITER

0

100

200

300

400

500

600

700

800

900

1,000

1,100

BICARBONATE,

IN MILLIGRAMS PER LITER

Alluvial Ogallala Arikaree White River

0

100

200

300

400

500

600

700

800

900

1,000

1,100

SODIUM,

IN MILLIGRAMS PER LITER

Alluvial Ogallala Arikaree White River

25 41 52 17 19 1

0

100

150

200

250

300

350

400

450

550

600

650

700

750

ALKALINITY,

IN MILLIGRAMS PER LITER

Pierre

Shale

Dakota

Sandstone

Pierre

Shale

Dakota

Sandstone

AQUIFER AQUIFER
Ground Water 57

Figure 30. Boxplots of chemical constituents in ground-water samples.--Continued

3,200

2,600

2,800

3,000

2,400

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

2,200

SULFATE,

IN MILLIGRAMS PER LITER

52 142 75 20 24 13 36 45 57 20 21 11

52 147 77 20 24 13 40 92 45 0 18 23

49 54 58 20 24 11

85

65

70

75

80

0

10

15

20

25

30

35

40

45

50

55

60

SILICA,

IN MILLIGRAMS PER LITER

0

100

200

300

400

500

600

700

800

900

1,000

CHLORIDE,

IN MILLIGRAMS PER LITER

0

5

10

15

20

25

30

35

40

45

50

NITRATE,

IN MILLIGRAMS PER LITER

Alluvial Ogallala Arikaree White River

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

FLUORIDE,

IN MILLIGRAMS PER LITER

Alluvial Ogallala Arikaree White River

11 28 26 13 5 2

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

PHOSPHORUS,

IN MILLIGRAMS PER LITER

NO SAMPLE

Pierre

Shale

Dakota

Sandstone

Pierre

Shale

Dakota

Sandstone

AQUIFER AQUIFER
58 Water Resources of Mellette and Todd Counties, South Dakota

Figure 30. Boxplots of chemical constituents in ground-water samples.--Continued

120

0

10

20

30

40

50

60

70

80

90

100

110

ARSENIC,

IN MICROGRAMS PER LITER

17 20 46 9 5 2 23 30 44 9 7 5

17 30 25 10 2 10 16 23 42 9 6 3

29 48 51 9 6 6

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

MANGANESE,

IN MICROGRAMS PER LITER

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,500

5,000

BORON,

IN MICROGRAMS PER LITER

0

5

10

15

20

25

30

35

40

45

65

50

55

60

SELENIUM,

IN MICROGRAMS PER LITER

Alluvial Ogallala Arikaree White River

Alluvial Ogallala Arikaree White River

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

3,400

2,000

2,200

2,400

2,600

2,800

3,000

3,200

IRON,

IN MICROGRAMS PER LITER

Detection limit

EXPLANATION

75th percentile concentration

Largest concentration within 1.5 interquartile ranges above

 the 75th percentile

Concentration within 1.5 to 3.0 interquartile ranges above

 the 75th percentile

Concentration greater than 3 interquartile ranges above

 the 75th percentile

Single sample

Number of samples

Smallest concentration within 1.5 interquartile ranges below

 the 25th percentile

50th percentile concentration (median)

25th percentile concentration

48

Maximum contaminant level (mandatory) (USEPA, 1994a)

Secondary maximum contaminant level (recommended)

Pierre (USEPA, 1994a)

Shale

Dakota

Sandstone

AQUIFER

Pierre

Shale

Dakota

Sandstone

AQUIFER
Ground Water 59

Table 6. Significance of chemical and physical properties of water

Constituent or 

property Limit Significance

Specific conductance A measure of the ability of water to conduct an electrical current; varies with temperature. 

Magnitude depends on concentration, kind, and degree of ionization of dissolved 

constituents; can be used to determine the approximate concentration of dissolved solids. 

Values are reported in microsiemens per centimeter at 25° Celsius.

pH 6.5-8.5 units

(recommended)

A measure of the hydrogen ion concentration; pH of 7.0 indicates a neutral solution, pH values 

less than 7.0 indicate acidity, pH values greater than 7.0 indicate alkalinity. Water generally 

becomes more corrosive with decreasing pH; however, excessively alkaline water also may be 

corrosive.

Temperature Affects the usefulness of water for many purposes. Generally, users prefer water of uniformly 

low temperature. Temperature of ground water tends to increase with increasing depth to the 

aquifer.

Hardness (as

 CaCO3)

Related to the soap-consuming characteristics of water; results in formation of scum when soap 

is added. May cause deposition of scale in boilers, water heaters, and pipes. Hardness 

equivalent to the bicarbonate and carbonate in water is called carbonate hardness; hardness in 

excess of this concentration is called noncarbonate hardness. Water that has a hardness less 

than 61 mg/L is considered soft; 61-120 mg/L, moderately hard; 121-180 mg/L, hard; and 

more than 180 mg/L, very hard (Heath, 1983).

Calcium plus

 magnesium

Cause most of the hardness and scale-forming properties of water (see hardness).

Sodium plus

 potassium

Large concentrations may limit use of water for irrigation and industrial use and, in combination 

with chloride, give water a salty taste. Abnormally large concentrations may indicate natural 

brines, industrial brines, or sewage.

Percent sodium Ratio of sodium to total cations in milliequivalents per liter expressed as a percentage. 

Important in irrigation waters; the greater the percent sodium, the less suitable the water for 

irrigation.

Sodium-adsorption

 ratio (SAR)

A ratio used to express the relative activity of sodium ions in exchange reactions with soil. 

Important in irrigation water; the greater the SAR, the less suitable the water for irrigation.

Bicarbonate In combination with calcium and magnesium forms carbonate hardness.

Sulfate 250 mg/L

(recommended)

Sulfates of calcium and magnesium form hard scale. Large concentrations of sulfate have a 

laxative effect on some people and, in combination with other ions, give water a bitter taste.

Chloride 250 mg/L

(recommended)

Large concentrations increase the corrosiveness of water and, in combination with sodium, give 

water a salty taste.

Fluoride 4.0 mg/L

(mandatory)

2.0 mg/L

(recommended)

Reduces incidence of tooth decay when optimum fluoride concentrations present in water 

consumed by children during the period of tooth calcification. Potential health effects of 

long-term exposure to elevated fluoride concentrations include dental and skeletal fluorosis 

(U.S. Environmental Protection Agency, 1994b).

Silica (as SiO3) Forms hard scale in pipes and boilers and may form deposits on blades of steam turbines. 

Inhibits deterioration of zeolite-type water softeners.

Dissolved solids 500 mg/L

(recommended)

The total of all dissolved mineral constituents, usually expressed in milligrams per liter. The 

concentration of dissolved solids may affect the taste of water. Water that contains more than 

1,000 mg/L is unsuitable for many industrial uses. Some dissolved mineral matter is 

desirable, otherwise the water would have no taste. The dissolved solids concentration 

commonly is called the water’s salinity and is classified as follows: fresh, 0 to 1,000 mg/L; 

slightly saline, 1,000 to 3,000 mg/L; moderately saline, 3,000 to 10,000 mg/L; very saline, 

10,000 to 35,000 mg/L; and briny, more than 35,000 mg/L (Heath, 1983).

Nitrite (as N) 1 mg/L

(mandatory)

Commonly formed as an intermediate product in bacterially mediated nitrification and 

denitrification of ammonia and other organic nitrogen compounds. Thus it often, though not 

always, may indicate pollution by sewage, feedlot or barnyard drainage, or some similar 

source. Nitrite has a toxic effect similar to that of nitrate, but stronger for given 

concentrations.
60 Water Resources of Mellette and Todd Counties, South Dakota

Nitrate (as N) 10 mg/L

(mandatory)

Concentrations greater than local background levels may indicate pollution by feedlot runoff, 

sewage, or fertilizers. Concentrations greater than 10 mg/L, as nitrogen, may be injurious 

when used in feeding infants.

Phosphate Essential to plant growth. Concentrations greater than local background levels may indicate 

pollution by fertilizer or sewage.

Aluminum 0.05-0.2 mg/L

(recommended)

No known necessary role in human or animal diet. Nontoxic in the concentrations normally 

found in natural water supplies. Elevated dissolved aluminum concentrations in some low pH 

waters can be toxic to some types of fish (Hem, 1985).

Arsenic 50 μg/L

(mandatory)

No known necessary role in human or animal diet, but is toxic. A cumulative poison that is 

slowly excreted. Can cause nasal ulcers; skin cancer; damage to the kidneys, liver, and 

intestinal walls; and death.

Barium 2,000 μg/L

(mandatory)

Toxic; used in rat poison. In moderate to large concentrations can cause death; smaller 

concentrations cause damage to the heart, blood vessels, and nerves.

Boron Essential to plant growth, but may be toxic to crops when present in excessive concentrations in 

irrigation water. Sensitive plants show damage when irrigation water contains more than 

670 μg/L and even tolerant plants may be damaged when boron exceeds 2,000 μg/L. The 

recommended limit is 750 μg/L for long-term irrigation on sensitive crops (U.S. 

Environmental Protection Agency, 1986).

Cadmium 5 μg/L

(mandatory)

A cumulative poison; very toxic. Not known to be either biologically essential or beneficial. 

Believed to promote renal arterial hypertension. Elevated concentrations may cause liver and 

kidney damage, or even anemia, retarded growth, and death.

Chromium 100 μg/L

(mandatory)

No known necessary role in human or animal diet. In the hexavalent form is toxic, leading to 

intestinal damage and to nephritis.

Copper 1,000 μg/L

(recommended)

Essential to metabolism; copper deficiency in infants and young animals results in nutritional 

anemia. Large concentrations of copper are toxic and may cause liver damage. Some people 

can detect the taste of as little as 1 to 5 mg/L of copper.

Iron 300 μg/L

(recommended)

Forms rust-colored sediment; stains laundry, utensils, and fixtures reddish brown. 

Objectionable for food and beverage processing. Can promote growth of certain kinds of 

bacteria that clog pipes and well openings.

Lead 50 μg/L

(mandatory)

15 μg/L

(recommended)

A cumulative poison, toxic in small concentrations. Can cause lethargy, loss of appetite, 

constipation, anemia, abdominal pain, gradual paralysis in the muscles, and death. If 1 in 10 

samples of a public supply exceed 15 μg/L, the USEPA recommends treatment to remove lead 

and monitoring of the water supply for lead content (U.S. Environmental Protection Agency, 

1991).

Lithium Reported as probably beneficial in small concentrations (250 to 1,250 μg/L). Reportedly may 

help strengthen the cell wall and improve resistance to genetic damage and to disease. 

Lithium salts are used to treat certain types of psychosis.

Manganese 50 μg/L

(recommended)

Causes gray or black stains on porcelain, enamel, and fabrics. Can promote growth of certain 

kinds of bacteria that clog pipes and well openings.

Mercury 2 μg/L

(mandatory)

No known essential or beneficial role in human or animal nutrition. Liquid metallic mercury 

and elemental mercury dissolved in water are comparatively nontoxic, but some mercury 

compounds, such as mercuric chloride and alkyl mercury, are very toxic. Elemental mercury 

is readily alkylated, particularly to methyl mercury, and concentrated by biological activity. 

Potential health effects of exposure to some mercury compounds in water include severe 

kidney and nervous system disorders (U.S. Environmental Protection Agency, 1994b).

Molybdenum In minute concentrations, appears to be an essential nutrient for both plants and animals, but in 

large concentrations may be toxic.

Nickel 100 μg/L

(mandatory)

Very toxic to some plants and animals. Toxicity for humans is believed to be very minimal.

Table 6. Significance of chemical and physical properties of water–Continued

Constituent or 

property Limit Significance
Ground Water 61

Selenium 50 μg/L

(mandatory)

Essential to human and animal nutrition in minute concentrations, but even a moderate excess 

may be harmful or potentially toxic if ingested for a long time (Callahan and others, 1979). 

Potential human health effects of exposure to elevated selenium concentrations include liver 

damage (U.S. Environmental Protection Agency, 1994b).

Silver 100 μg/L

(recommended)

Causes permanent bluish darkening of the eyes and skin (argyria). Where found in water is 

almost always from pollution or by intentional addition. Silver salts are used in some 

countries to sterilize water supplies. Toxic in large concentrations.

Strontium Importance in human and animal nutrition is not known, but believed to be essential. Toxicity 

believed very minimal--no more than that of calcium.

Vanadium Not known to be essential to human or animal nutrition, but believed to be beneficial in trace 

concentrations. May be an essential trace element for all green plants. Large concentrations 

may be toxic.

Zinc 5,000 μg/L

(recommended)

Essential and beneficial in metabolism; its deficiency in young children or animals will retard 

growth and may decrease general body resistance to disease. Seems to have no ill effects 

even in fairly large concentrations (20,000 to 40,000 mg/L), but can impart a metallic taste or 

milky appearance to water. Zinc in drinking water commonly is derived from galvanized 

coatings of piping.

Table 6. Significance of chemical and physical properties of water–Continued

Constituent or 

property Limit Significance

Water samples collected from wells completed in 

the Arikaree aquifer did not exceed the USEPA MCL’s 

for any regulated constituent with the following exceptions: 1 sample out of 45 analyzed for nitrate exceeded 

the MCL, and 11 samples out of 46 analyzed for arsenic 

exceeded the MCL of 50 μg/L. In samples from the 

Arikaree aquifer, 1 out of 58 samples exceeded the 

SMCL for fluoride, 7 out of 67 samples for dissolved 

solids, and 4 out of 44 samples for manganese. An 

investigation of high arsenic concentrations in the 

Arikaree aquifer in the Grass Mountain area, located 

about 5 miles northwest of Rosebud in Todd County, 

was conducted by the USGS in cooperation with the 

Rosebud Sioux Tribe and the South Dakota Geological 

Survey during 1991-96. The results of the investigation 

indicate that the source of arsenic is natural and probably sourced by volcanic ash in the Arikaree Formation 

(Carter and others, 1998). Arsenic may be high in the 

aquifer in other parts of Mellette and Todd Counties 

because two of the samples with arsenic concentrations 

that exceeded the MCL were not collected near the 

Grass Mountain area but were located in eastern Todd 

County (Carter, 1997). 

No water samples collected from wells completed in the White River aquifer exceeded the USEPA 

MCL’s for any regulated constituent, although almost 

one-half of the samples exceeded the SMCL for 

dissolved solids. A few samples also exceeded the 

SMCL’s for sulfate (4 out of 20 samples), manganese (1 

out of 9 samples), and chloride (3 out of 20 samples).

The only constituent concentration that exceeded 

an MCL in samples collected from the Pierre Shale 

aquifer was nitrate (3 out of 23 samples). The median 

concentrations for dissolved solids, sulfate, and manganese exceeded the SMCL’s for these constituents. 

Some samples from the Pierre Shale aquifer also 

exceeded the SMCL’s for chloride (2 out of 24 

samples), fluoride (2 out of 24 samples), and iron (1 out 

of 7 samples).

Water samples collected from wells completed in 

the Dakota Sandstone aquifer exceeded the USEPA 

MCL’s for fluoride. Of the 11 samples analyzed for 

fluoride, 5 equalled or exceeded the MCL and 10 

exceeded the SMCL. The median concentrations for 

dissolved solids and sulfate exceeded the SMCL’s for 

these constituents. Concentrations from some of the 

samples collected from the Dakota Sandstone aquifer 

also exceeded the SMCL’s: 4 out of 13 for chloride, 1 

out of 6 for iron, and 2 out of 5 for manganese.

In samples collected from the Inyan Kara 

aquifer, the MCL for fluoride was exceeded in 1 of the 

3 samples, and the SMCL for fluoride was exceeded for 

all 3 samples. For the 3 samples collected, the minimum concentrations for dissolved solids, sulfate, iron, 

and manganese exceeded the SMCL’s for these constituents. One sample exceeded the SMCL for chloride.
62 Water Resources of Mellette and Todd Counties, South Dakota

The MCL for mercury was exceeded in one 

sample collected from the Minnelusa and Madison 

aquifers. The minimum concentrations of the three 

samples exceeded the SMCL’s for dissolved solids, 

sulfate, and iron. Two of the 3 samples exceeded the 

SMCL for manganese.

The general suitability of water for irrigation 

from the aquifers in the study area can be determined 

by using the South Dakota irrigation-water diagram 

(fig. 31). The diagram is based on South Dakota irrigation-water standards (revised January 7, 1982) and 

shows the State’s water-quality and soil-texture 

requirements for the issuance of an irrigation permit. 

Generally, most water from the Ogallala and Arikaree 

aquifers is suitable for irrigation. The quality of water 

from alluvial aquifers and the White River aquifer generally is suitable for irrigation, but yields probably are 

not sufficient in most areas. Limited irrigation may be 

supported by alluvial aquifers in areas where the permeability is very high and in areas where the aquifer is 

hydraulically connected to a perennial stream. A few 

wells completed in the White River aquifer are used to 

support irrigation in Mellette County. The Pierre 

Shale, Dakota Sandstone, and Inyan Kara aquifers are 

unsuitable for irrigation because of high sodiumadsorption ratios coupled with high specific conductances. Water from the Minnelusa and Madison 

aquifers can be used for irrigation under certain soil 

conditions (fig. 31), although currently no irrigationuse data have been reported for either aquifer in 

Mellette and Todd Counties.

Water from eight aquifers in the study area 

generally is suitable for livestock watering. Suitability 

of water for domestic and municipal purposes is limited 

in the bedrock aquifers because of high dissolved 

solids. Generally, water from the shallow aquifers 

(alluvial, Ogallala, Arikaree, and White River aquifers) 

is suitable for all water uses, except where constituent 

concentrations exceed the MCL’s. 

WATER USE

Withdrawal of water during 1995 for use in 

Mellette and Todd Counties was about 10,560 acre-feet 

(table 7). The withdrawal was about 1,220 acre-feet in 

Mellette County and about 9,340 acre-feet in Todd 

County. Surface-water withdrawal was about 780 acrefeet in Mellette County, of which 54 percent was used 

for livestock and 46 percent for irrigation. Surfacewater withdrawal was about 630 acre-feet in Todd 

County, of which 59 percent was used for livestock and 

41 percent for irrigation. About 60 percent of the water 

used for stock watering in both counties was derived 

from surface-water sources and 40 percent from 

ground-water sources. In Mellette County, 86 percent 

of the water used for irrigation was derived from surface-water sources and 14 percent from ground-water 

sources. In Todd County, only 3 percent of the water 

used for irrigation was from surface-water sources, and 

97 percent was from ground-water sources. Ground 

water was the source of all water used for municipal 

and rural-domestic purposes in both counties.

1

Total percentage may not equal sum of components because of rounding.

Table 7. Ground- and surface-water withdrawals in Mellette and Todd Counties during 1995

[From F.D. Amundson, U.S. Geological Survey, written commun., 1997]

Source

Total Municipal Rural-domestic Livestock Irrigation

Acre-feet Percent Acre-feet Percent Acre-feet Percent Acre-feet Percent Acre-feet Percent

Mellette County

Ground water 437 4.1 45 0.4 56 0.5 280 2.7 56 0.5

Surface water 784 7.4 0 0 0 0 426 4.0 358 3.4

Todd County

Ground water 8,713 82.5 123 1.2 582 5.5 246 2.3 7,762 73.5

Surface water 627 5.9 0 0 0 0 370 3.5 257 2.4

Total, both 

counties

10,561 1100 168 1.6 638 6.0 1,322 12.5 8,433 179.9
Water Use 63

Figure 31. South Dakota irrigation-water classification diagram (based on South Dakota standards (revised Jan. 7, 

1982) for maximum allowable specific conductance and adjusted sodium-adsorption-ratio values for which an 

irrigation permit can be issued for applying water under various soil-texture conditions. Water an be applied under 

all conditions at or above the plotted point, but not below it, provided other conditions as defined by the State 

Conservation Commission are met (from Koch, 1983)).

A1 A2 A1 A2 A1 A2

B1

C1

B2 B1

C1 B2

D2 E1

D3 E2 E1 B3

C2

D1

B3

B1

B2

C2 C1

C3 D1

D2

E3 E2 C2

C3

D3

E3 C3

B3

0 3 6 7 8 9 10 11 12

3,100

3,000

2,900

2,800

2,700

2,600

2,500

2,400

2,300

2,200

2,100

2,000

1,900

1,800

1,700

1,600

1,500

1,400

1,300

1,200

1,100

1,000

ADJUSTED SODIUM-ADSORPTION RATIO (SAR)

MULTIPLIED BY 0.7

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER AT 25¡ CELSIUS 

(ECx10 AT 25¡ C) ADJUSTED FOR CALCIUM, SULFATE, AND RAINFALL 6

EXPLANATION

SOIL TEXTURE

 Sand

 Loamy sands, sandy loams

 Loams, silts, silt loams

 Sandy clay loams, silty clay

 loams, clay loams

 Silty clays, sandy clays, clays

DEPTH BELOW LAND SURFACE

 TO A MORE-PERMEABLE OR

 LESS-PERMEABLE MATERIAL

 40 inches or less to a more-

 permeable material

 40 to 72 inches to a more-

 permeable material

 20 to 60 inches to a less-

 permeable material

SPECIFIC CONDUCTANCE

 Maximum values are based on

 12 inches or less average

 rainfall during the frost-free

 season. For each additonal 

 inch of rainfall, the maximum

 values of conductivity may be 

 increased by 100. Average

 growing season rainfall for

 Mellette and Todd Counties is

 14 inches, so the conductivity of

 each plotted value has been

 reduced by 200 microsiemens.

 For water having more than

 200 milligrams per liter of

 calcium and more than 960

 milligrams per liter of sulfate,

 the maximum conductance

 value may be increased by 400

 microsiemens.

A

B

C

E

1

2

3

AVERAGE CHEMICAL QUALITY OF

 SHALLOW AQUIFERS

AVERAGE CHEMICAL QUALITY OF

 BEDROCK AQUIFERS

D

Alluvial

Ogallala

Arikaree

White River

Pierre Shale

Minnelusa and Madison

Inyan Kara--Arrows indicates

 water properties plot ouside of

 boundaries of the graph

Dakota Sandstone--Arrow indicates

 water properties plot outside of

 boundaries of the graph

900

800

700

600

500

400

300

200

100
64 Water Resources of Mellette and Todd Counties, South Dakota

Withdrawal of ground water in Mellette County 

during 1995, summarized in table 8, was almost 

440 acre-feet. Aquifer withdrawals were estimated 

from available water-use data in the USGS NWIS 

ground-water database. About 66 percent of the 

ground water used was supplied by shallow aquifers, 

and about 34 percent was supplied by bedrock aquifers. 

Most of the ground water was supplied by alluvial aquifers (about 31 percent) and the Pierre Shale aquifer 

(about 24 percent). The deeper bedrock aquifers only 

supplied about 9 percent of the ground water. Most of 

the ground water used in Mellette County was for 

stock-watering purposes (64 percent).

Withdrawal of ground water in Todd County 

during 1995, summarized in table 9, was about 

8,710 acre-feet. Almost 100 percent of the ground 

water used was supplied by shallow aquifers. The 

Ogallala aquifer supplied about 84 percent of the 

ground water used in Todd County. Other than the 

Pierre Shale, no bedrock aquifers supply water in Todd 

County. Most of the ground water (89 percent) was 

used for irrigation.

1Total percentage may not equal sum of components because of rounding.

1Total percentage may not equal sum of components because of rounding

Table 8. Estimated withdrawal of ground water in Mellette County during 1995

Source

Total Municipal Rural-domestic Livestock Irrigation

Acre-feet Percent Acre-feet Percent Acre-feet Percent Acre-feet Percent Acre-feet Percent

Shallow aquifers

Alluvial 134 30.7 31 7.0 11 2.5 73 16.7 19 4.3

Arikaree 73 16.7 3 0.7 25 5.7 20 4.6 25 5.7

White River 83 19.0 4 1.0 8 1.8 59 13.5 12 2.7

 Subtotal 290 66.4 38 8.7 44 110.1 152 134.8 56 112.8

Bedrock aquifers

Pierre Shale 106 24.2 0 0 10 2.3 96 22.0 0 0

Dakota Sandstone 26 5.9 7 1.6 2 0.5 17 3.9 0 0

Inyan Kara 10 2.3 0 0 0 0 10 2.4 0 0

Minnelusa and Madison 5 1.1 0 0 0 0 5 1.1 0 0

 Subtotal 147 133.6 7 1.6 12 12.7 128 129.3 0 0

Total, all aquifers 437 100 45 10.3 56 12.8 280 64.1 56 112.8

Table 9. Estimated withdrawal of ground water in Todd County during 1995

Source

Total Municipal Rural-domestic Livestock Irrigation

Acre-feet Percent Acre-feet Percent Acre-feet Percent Acre-feet Percent Acre-feet Percent

Shallow aquifers

Alluvial 44 0.5 0 0 38 0.4 6 0.1 0 0

Ogallala 7,355 84.4 41 0.5 125 1.4 102 1.2 7,087 81.3

Arikaree 1,228 14.1 82 0.9 357 4.1 114 1.3 675 7.8

White River 81 0.9 0 0 59 0.7 22 0.2 0 0

 Subtotal 8,708 1100 123 1.4 579 6.6 244 2.8 7,762 89.1

Bedrock aquifers

Pierre Shale 5 0 0 0 3 0 2 0 0 0

 Subtotal 5 0 0 0 3 0 2 0 0 0

Total, all aquifers 8,713 100 123 1.4 582 16.7 246 2.8 7,762 89.1
Summary and Conclusions 65

SUMMARY AND CONCLUSIONS

Mellette and Todd Counties, located in southcentral South Dakota, have a combined area of 

2,694 square miles. The main source of income is 

ranching. The average annual precipitation is about 

19 inches. The White River forms the northern 

boundary of Mellette County and the South DakotaNebraska border forms the southern boundary of Todd 

County. The major water resources of the counties are 

surface water and ground water from shallow and bedrock aquifers. 

The major rivers in Mellette and Todd Counties 

are the White, Little White, and Keya Paha Rivers. All 

of Mellette County and 51 percent of Todd County is 

drained by the White River, in Nebraska, and its tributaries; 49 percent of Todd County is drained by the Niobrara River and its tributaries, which include the Keya 

Paha River. The average flow of the Little White River 

is about 56 cubic feet per second as the river enters 

Todd County, and the average flow of the Little White 

River is 131 cubic feet per second at the most downstream streamflow-gaging station in Mellette County. 

The Keya Paha River near Keyapaha (just outside Todd 

County) has an average flow of about 39 cubic feet per 

second. The average annual runoff for the counties 

ranges from 0.94 to 2.36 inches and averages 

1.62 inches based on records from nine gaging stations 

in and near the counties. Bicarbonate, calcium, and sulfate are the dominant chemical species in the water of 

the Little White River. Surface-water quality varies 

seasonally with volume of streamflow. Generally, the 

concentrations of dissolved constituents increase from 

upstream to downstream. 

The geology of Mellette and Todd Counties consists mostly of marine, fluvial, and eolian deposits. The 

major shallow aquifers in the counties are the alluvial, 

Ogallala, Arikaree, and White River aquifers. The 

bedrock aquifers include the Pierre Shale, Dakota 

Sandstone, Inyan Kara, and Minnelusa and Madison 

aquifers.

In Todd County, ground water generally can be 

obtained from shallow wells completed in the alluvial, 

Ogallala, Arikaree, or White River aquifers. In 

Mellette County, the Pierre Shale is present at the land 

surface throughout most of the county, which means 

that the Ogallala, Arikaree, and White River aquifers 

are not present. Because shallow ground-water sources 

in Mellette County often are not available, deep 

bedrock aquifer wells, often greater than 1,000 feet, are 

sometimes installed.

The boundaries of four shallow aquifers 

(alluvial, Ogallala, Arikaree, and White River) and 

one bedrock aquifer (Pierre Shale) were delineated for 

this study. Alluvial aquifers are present in both Mellette and Todd Counties; however, the water has high 

concentrations of dissolved solids, is saline, and is 

very hard in Mellette County where the alluvial deposits are underlain by the Pierre Shale. Also, deposits 

overlying the Pierre Shale are relatively impermeable 

and may not yield an adequate supply of water. The 

major alluvial aquifers are located along the Keya 

Paha, Little White, and White Rivers. The average 

thickness of the alluvial aquifers is 29 feet. Alluvial 

aquifers underlie about 440 square miles of the study 

area and store an estimated 1.6 million acre-feet of 

water. Recharge to the alluvial aquifers is by infiltration of precipitation, stream loss, and discharge from 

springs originating in the Tertiary deposits. Discharge 

from the alluvial aquifers is through withdrawals from 

domestic and stock wells and by evapotranspiration 

from the aquifer. Water from the alluvial aquifers primarily is used for stock-watering and rural-domestic 

purposes; however, it can be used to support irrigation 

in some areas of Mellette County.

The Ogallala aquifer is present throughout most 

of Todd County, but not in Mellette County. The 

aquifer underlies 950 square miles in Todd County 

and contains an estimated 17 million acre-feet of 

water in storage. The depth to the top of the Ogallala 

aquifer ranges from 0 to 164 feet below land surface, 

and the average thickness is 137 feet. The aquifer is 

thickest in central Todd County, and is under watertable conditions except in southwestern Todd County, 

where it is confined. Recharge to the Ogallala aquifer 

is by infiltration of precipitation on the outcrops of the 

Ogallala Formation or overlying windblown sand 

deposits and by stream loss. The primary discharge 

from the aquifer is through withdrawals from domestic, public, stock, and irrigation wells; by loss to 

streams and springs; and by evapotranspiration. The 

aquifer has the highest yield potential of the eight 

aquifers in the study area; the maximum reported well 

yield is 1,250 gallons per minute.

The Arikaree aquifer is present throughout most 

of Todd County, although it is absent in the eastern part 

of the county. The Arikaree is present in only a small 

part of southwestern Mellette County. The Arikaree 

aquifer underlies about 1,360 square miles in Mellette 

and Todd Counties and contains an estimated 50 

million acre-feet of water in storage. The depth to the 
66 Water Resources of Mellette and Todd Counties, South Dakota

top of the aquifer ranges from 0 to 406 feet below land 

surface, and the average thickness is 290 feet. About 

one-half of the aquifer is under water-table conditions 

and one-half is confined. Yields from the Arikaree 

aquifer range from 1 to 1,005 gallons per minute and 

generally are not as high as those from the Ogallala 

aquifer, but yields are often sufficient to support irrigation. Recharge to the Arikaree aquifer is by infiltration 

of precipitation on the outcrops of the Arikaree 

Formation and by stream loss. Discharge is through 

withdrawals from domestic, stock, and irrigation wells; 

by evapotranspiration; and by discharge from springs to 

alluvial aquifers and streams.

The White River aquifer is present throughout 

most of Todd County and in western and south-central 

Mellette County. Other than alluvial aquifers, the 

White River aquifer, where present, is the shallowest 

source of ground water in Mellette County. In Todd 

County, the White River aquifer is used mostly where 

the Ogallala and Arikaree aquifers are not present. The 

White River aquifer underlies approximately 

1,720 square miles of the study area and contains an 

estimated 50 million acre-feet of water in storage. The 

depth to the top of the White River aquifer ranges from 

0 to 789 feet below land surface, and the average thickness is 229 feet. Most of the aquifer is confined. 

Although the water quality of the White River aquifer 

generally is suitable for irrigation purposes, well yields 

are not sufficient. The reported yields of the White 

River aquifer in the counties range from 1 to 30 gallons 

per minute. Recharge to the aquifer is by infiltration of 

precipitation on outcrops of the White River Group and 

by stream loss. Discharge from the aquifer is by withdrawals from domestic and stock wells, evapotranspiration, and discharge from springs to alluvial deposits 

and streams.

The Pierre Shale is the shallowest bedrock 

aquifer and is exposed at the land surface throughout 

most of Mellette County. Although the Pierre Shale is 

present throughout both counties, it is used as an 

aquifer only in Mellette County to supply ruraldomestic and stock wells. The aquifer contains an estimated maximum of 1.5 million acre-feet of water in 

storage; however, it is not a viable source of ground 

water because water can usually be obtained from shallower aquifers, yields are low, and the aquifer is relatively impermeable. Reported yields from the Pierre 

Shale aquifer range from 1 to 8 gallons per minute. The 

depth to the top of the Pierre Shale ranges from 0 to 

greater than 1,200 feet in the study area. The Pierre 

Shale aquifer, where used, is under water-table conditions. Recharge to the aquifer is primarily by infiltration of precipitation on outcrops of the Pierre Shale, 

and discharge is through withdrawals from domestic 

and stock wells and by evapotranspiration.

Little is known about the deeper bedrock 

aquifers (Dakota Sandstone, Inyan Kara, and 

Minnelusa and Madison) because few test holes and 

wells penetrate below the Pierre Shale. All but two of 

the deeper test holes and wells are located in Mellette 

County so the extent of some of the bedrock aquifers in 

Todd County is not known. Recharge to all of the 

deeper bedrock aquifers primarily is by infiltration of 

precipitation on outcrops of the formations, which 

occurs mainly in the Black Hills. In the study area, 

discharge from the bedrock aquifers is through withdrawals from stock wells.

The Dakota Sandstone aquifer underlies both 

counties and contains more than 81 million acre-feet of 

water in storage. The depth to the top of the Dakota 

Sandstone ranges from 1,270 to 2,348 feet below land 

surface. Reported yields from the Dakota Sandstone 

aquifer range from 10 to 100 gallons per minute.

The areal extent of the Inyan Kara, and 

Minnelusa and Madison aquifers in Todd County is not 

known. The depth to the top of these aquifers generally 

is at least 1,900 feet below land surface. The 

Minnelusa and Madison aquifers are the only bedrock 

aquifers that generally are suitable for irrigation. 

Reported yields from the Inyan Kara aquifer range 

from 9 to 160 gallons per minute, and yields from the 

Minnelusa and Madison aquifers range from 25 to 

40 gallons per minute.

The chemical quality of water in the aquifers in 

the counties varies widely, both within and between 

aquifers. The chemical quality among the aquifers of 

Tertiary age is the most similar. The quality of water 

from the alluvial aquifers is dependant on the underlying deposits; the water generally has low concentrations of dissolved solids, is fresh, and is soft to moderately hard where underlain by the Ogallala and 

Arikaree Formations; has moderate concentrations of 

dissolved solids, is slightly saline, and is hard where 

underlain by the White River Group; and has high concentrations of dissolved solids, is saline, and is very 

hard where underlain by the Pierre Shale. Calcium and 

bicarbonate generally are the dominant species in 

alluvial water where underlain by the Tertiary deposits, 

and sodium and chloride are the dominant species 

where underlain by the Pierre Shale. One out of 49 

samples from the alluvial aquifers exceeded the 
References Cited 67

USEPA Primary Drinking-Water Regulations 

Maximum Contaminant Level (MCL) for fluoride, and 

1 out of 16 samples exceeded that MCL for selenium.

Calcium and bicarbonate are the dominant 

species in water from the Ogallala aquifer; calcium, 

sodium, and bicarbonate are the dominant species in 

water from the Arikaree aquifer. The water of both the 

Ogallala and Arikaree aquifers generally has low concentrations of dissolved solids, is fresh, and is soft to 

moderately hard. In samples collected from the 

Ogallala aquifer, 1 out of 54 exceeded the MCL for 

fluoride, and 13 out of 92 exceeded the MCL for nitrate. 

In samples collected from the Arikaree aquifer, 1 out of 

45 samples exceeded the MCL for nitrate, and 11 out of 

46 samples exceeded the MCL for arsenic.

The dominant species in water from the White 

River aquifer are calcium, sodium, and bicarbonate. 

The water quality from this aquifer is dependant on 

depth and proximity of the aquifer material to the Pierre 

Shale. The water is higher in dissolved solids, more 

saline, and hard where the water-bearing deposits are 

close to the Pierre Shale. 

The bedrock aquifers generally yield a hard water 

with high concentrations of dissolved solids. The 

Dakota Sandstone aquifer yields the softest water of the 

bedrock aquifers. Concentrations of dissolved solids in 

the bedrock aquifers are lowest in the Minnelusa and 

Madison aquifers, which would allow water from these 

aquifers to be used for irrigation.

Withdrawal of water during 1995 in Mellette and 

Todd Counties was about 10,560 acre-feet. More surface water than ground water was used by Mellette 

County, although all water used for municipal and 

rural-domestic purposes was from ground water. Most 

of the ground water used in Todd County (89 percent) 

was for irrigation.

REFERENCES CITED

Agnew, A.F., and Tychsen, P.C., 1965, A guide to the stratigraphy of South Dakota: South Dakota Geological 

Survey Bulletin 14, 195 p.

Bradley, Edward, 1956, Geology and ground-water resources 

of the Upper Niobrara River Basin, Nebraska and Wyoming: U.S. Geological Survey Water-Supply Paper 

1368, 70 p.

Bredehoeft, J.D., Neuzil, C.E., and Milly, P.C.D., 1983, 

Regional flow in the Dakota aquifer—A study of the 

role of confining layers: U.S. Geological Survey WaterSupply Paper 2237, 45 p.

Callahan, M.A., Slimak, M.W., Gabel, N.W., May, I.P., 

Fowler, C.F., Freed, J.R., Jennings, Patricia, Durfee, 

R.L., Whitmore, F.C., Maestri, Bruno, Mabey, W.R., 

Holt, B.R., and Gould, Constance, 1979, Water-related 

environmental fate of 129 priority pollutants, 

Volume I—Introduction and technical background, 

metals and inorganics, pesticides and PCBs: U.S. 

Environmental Protection Agency, Office of Water 

Planning and Standards, Office of Water and Waste 

Management, EPA-440/4-79-029a [variously paged].

Carter, J.M., 1997, Water-quality data from 1990 through 

1996 for the water resources investigation of Mellette 

and Todd Counties, South Dakota: U.S. Geological 

Survey Open-File Report 97-248, 75 p.

Carter, J.M., Sando, S.K., Hayes, T. S., and Hammond, 

R.H., 1998, Source, occurrence, and extent of arsenic 

in the Grass Mountain area of the Rosebud Indian Reservation, South Dakota: U.S. Geological Survey 

Water Resources Investigations Report 98-4286, 90 p.

Case, H.L., III, 1984, Hydrology of Inyan Kara and DakotaNewcastle aquifer system, South Dakota, in Jorgensen, D.G., and Signor, D.C., eds., Geohydrology of 

the Dakota aquifer, Proceedings of the first C.V. Theis 

Conferences on Geohydrology: Worthington, Ohio, 

The National Water Well Association, p. 147-165.

Darton, N.H., 1905, Preliminary report on the geology and 

underground water resources of the Central Great 

Plains: U.S. Geological Survey Professional Paper 32, 

433 p.

Dugan, J.T., McGrath, Timothy, and Zelt, R.B., 1994, 

Water-level changes in the High Plains aquifer—Predevelopment to 1992: U.S. Geological Survey Water 

Resources Investigations Report 94-4027, 56 p.

Ellis, M.J., Adolphson, D.G., and Ficken, J.H., 1972, Basic 

hydrogeologic data, Rosebud Indian Reservation, 

South Dakota: South Dakota Geological Survey Water 

Resources Report No. 6, 111 p.

Ellis, M.J., Ficken, J.H., and Adolphson, D.G., 1971, 

Hydrology of the Rosebud Indian Reservation, South 

Dakota: U.S. Geological Survey Hydrologic Investigations Atlas HA-335.

Fenneman, N.M., 1946, Physical divisions of the United 

States: U.S. Geological Survey map prepared in 

cooperation with the Physiographic Commission, U.S. 

Geological Survey, scale 1:700,000 (reprinted 1964).

Flint, R. F., 1955, Pleistocene geology of eastern South 

Dakota: U.S. Geological Survey Professional Paper 

262, 173 p.

Greene, E.A., Anderson, M.T., and Sipe, D.D., 1991, Aquifer tests and water-quality analyses of the Arikaree 

Formation near Pine Ridge, South Dakota: U.S. 

Geological Survey Water-Resources Investigations 

Report 91-4005, 45 p.
68 Water Resources of Mellette and Todd Counties, South Dakota

Hamilton, L.J., and Howells, L.W., 1996, Water resources of 

Spink County, South Dakota: U.S. Geological Survey 

Water-Resources Investigations Report 96-4056, 68 p.

Hammond, P.D., 1994, Ground water quality investigation in 

selected areas of Todd and Mellette Counties, South 

Dakota: South Dakota Geological Survey Open-File 

Report 68-UR, 36 p.

Heath, R.C., 1983, Basic ground-water hydrology: U.S. 

Geological Survey Water-Supply Paper 2220, 84 p.

Hem, J.D., 1985, Study and interpretation of the chemical 

characteristics of natural water: U.S. Geological 

Survey Water-Supply Paper 2254, 263 p.

Huq, S.Y., 1989, Annual report of the Office of Water 

Resources of the Rosebud Sioux Tribe, Rosebud, South 

Dakota.

Koch, N.C., 1983, Irrigation-water classification diagram for 

South Dakota: South Dakota Academy of Science 

Proceedings, v. 62, p. 107-114.

Kolm, K.E., and Case, H.L., III, 1983, A two-dimensional, 

finite-difference model of the High Plains aquifer in 

southern South Dakota: U.S. Geological Survey WaterResources Investigations Report 83-4175, 34 p.

Lohman, S.W., 1972, Ground-water hydraulics: U.S. 

Geological Survey Professional Paper 708, 70 p.

Lohman, S.W., and others, 1972, Definitions of selected 

ground-water terms—revisions and conceptual refinements: U.S. Geological Survey Water-Supply Paper 

1988, 21 p.

Luckey, R.R., Gutentag, E.D., Heimes, F.J., and Weeks, J.B., 

1988, Effects of future ground-water pumpage on the 

High Plains aquifer in parts of Colorado, Kansas, 

Nebraska, New Mexico, Oklahoma, South Dakota, 

Texas, and Wyoming: U.S. Geological Survey 

Professional Paper 1400-E, 44 p.

Miller, R.H., and Rahn, P.H., 1974, Recharge to the Dakota 

Sandstone from outcrops in the Black Hills, South 

Dakota: Bulletin of the Association of Engineering 

Geologists, v. 11, no. 3, p. 221-234.

Newport, T.G., 1959, Ground-water resources of the Lower 

Niobrara River and Ponca Creek Basins, Nebraska and 

South Dakota: U.S. Geological Survey Water-Supply 

Paper 1460-G, p. 272-323.

Peter, K.D., 1985, Availability and quality of water from the 

bedrock aquifers in the Rapid City area, South Dakota: 

U.S. Geological Survey Water-Resources Investigations Report 85-4022, 34 p.

Piper, A.M., 1944, A graphical procedure in the geochemical 

interpretation of water analyses: American Geophysical Union Transactions, v. 25 p. 914-923.

Schoon, R.A., 1971, Geology and hydrology of the Dakota 

Formation in South Dakota: South Dakota Geological 

Survey Report of Investigations 104, 55 p.

U.S. Department of Commerce, 1957-94, Climatological 

data, annual summary, Nebraska: Asheville, North 

Carolina, 1957 to 1994 (published annually).

———1994, Climatological data, annual summary, South 

Dakota, 1994: Asheville, North Carolina, v. 99, no. 13.

U.S. Environmental Protection Agency, 1986, Quality criteria for water (updated May 1986), Update No. 2: 

Washington, D.C., Office of Water Regulations and 

Standards, EPA 440/5-86-001, 398 p.

———1991, Lead and copper role fact sheet: U.S. 

Environmental Protection Agency, Office of Water, 

EPA 570/9-91-400, 2 p.

———1994a, Summary of EPA finalized National primary 

drinking water regulations: U.S. Environmental 

Protection Agency Region VIII, 7 p.

———1994b, National primary drinking water standards: 

U.S. Environmental Protection Agency, Office of 

Water, EPA 810-F-94-001A, 4 p.

U.S. Soil Conservation Service, 1974, Soil Survey of Todd 

County, South Dakota: U.S. Department of 

Agriculture.

———1975, Soil Survey of Mellette County, South Dakota: 

U.S. Department of Agriculture.