Who Standars

8/12/2019 Who Standars

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46 Hydrology of the Black Hills Area, South Dakota

Table 4 . Water-quality criteria, standards, or recommended limits for selected properties and constituents[All standards are from U.S. Environmental Protection Agency (1994a) unless noted. MCL, Maximum Contaminant Level; SMCL, Secondary MaximumContaminant Level; USEPA, U.S. Environmental Protection Agency; mg/L, milligrams per liter; S/cm, microsiemens per centimeter at 25 degrees Celsius;g/L, micrograms per liter; pCi/L, picocuries per liter; --, no limit established]

Constituentor property

Standard 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 constit-uents; can be used to determine the approximate concentration of dissolved solids. Valuesare reported in microsiemens per centimeter at 25 Celsius.

pH 6.5-8.5 unitsSMCL

A measure of the hydrogen ion concentration; pH of 7.0 indicates a neutral solution, pHvalues smaller than 7.0 indicate acidity, pH values larger than 7.0 indicate alkalinity.Water generally becomes more corrosive with decreasing pH; however, excessivelyalkaline water also may be corrosive.

Temperature -- Affects the usefulness of water for many purposes. Generally, users prefer water of uni-formly low temperature. Temperature of ground water tends to increase with increasingdepth to the aquifer.

Dissolved oxygen -- Required by higher forms of aquatic life for survival. Measurements of dissolved oxygenare used widely in evaluations of the biochemistry of streams and lakes. Oxygen is sup-plied to ground water through recharge and by movement of air through unsaturatedmaterial above the water table (Hem, 1985).

Carbon dioxide -- Important in reactions that control the pH of natural waters.

Hardness and noncar-bonate hardness (asmg/L CaCO 3)

-- Related to the soap-consuming characteristics of water; results in formation of scum whensoap is added. May cause deposition of scale in boilers, water heaters, and pipes. Hard-ness contributed by calcium and magnesium, bicarbonate and carbonate mineral speciesin water is called carbonate hardness; hardness in excess of this concentration is callednoncarbonate 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).

Alkalinity -- A measure of the capacity of unfiltered water to neutralize acid. In almost all natural watersalkalinity is produced by the dissolved carbon dioxide species, bicarbonate and carbon-ate. Typically expressed as mg/L CaCO 3.

Dissolved solids 500 mg/LSMCL

The total of all dissolved mineral constituents, usually expressed in milligrams per liter. Theconcentration of dissolved solids may affect the taste of water. Water that contains morethan 1,000 mg/L is unsuitable for many industrial uses. Some dissolved mineral matter isdesirable, otherwise the water would have no taste. The dissolved solids concentrationcommonly is called the waters salinity and is classified as follows: fresh, 0-1,000 mg/L;slightly saline, 1,000-3,000 mg/L; moderately saline, 3,000-10,000 mg/L; very saline,10,000-35,000 mg/L; and briny, more than 35,000 mg/L (Heath, 1983).

Calcium plus magne-sium

-- 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 combi-nation with chloride, give water a salty taste. Abnormally large concentrations may indi-cate natural brines, industrial brines, or sewage.

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 irriga-tion.

Bicarbonate -- In combination with calcium and magnesium forms carbonate hardness.


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Ground-Water Characteristics 47

Sulfate 250 mg/LSMCL

Sulfates of calcium and magnesium form hard scale. Large concentrations of sulfate have alaxative effect on some people and, in combination with other ions, give water a bittertaste.

Chloride 250 mg/LSMCL

Large concentrations increase the corrosiveness of water and, in combination with sodium,give water a salty taste.

Fluoride 4.0 mg/LMCL

2.0 mg/LSMCL

Reduces incidence of tooth decay when optimum fluoride concentrations present in waterconsumed by children during the period of tooth calcification. Potential health effects oflong-term exposure to elevated fluoride concentrations include dental and skeletal fluo-rosis (U.S. Environmental Protection Agency, 1994b).

Nitrite (mg/L as N) 1.0 mg/LMCL

Commonly formed as an intermediate product in bacterially mediated nitrification and den-itrification of ammonia and other organic nitrogen compounds. An acute health concernat certain levels of exposure. Nitrite typically occurs in water from fertilizers and is foundin sewage and wastes from humans and farm animals. Concentrations greater than1.0 mg/L, as nitrogen, may be injurious to pregnant women, children, and the elderly.

Nitrite plus nitrate(mg/L as N)

10 mg/LMCL

Concentrations greater than local background levels may indicate pollution by feedlot run-off, sewage, or fertilizers. Concentrations greater than 10 mg/L, as nitrogen, may beinjurious to pregnant women, children, and the elderly.

Ammonia -- Plant nutrient that can cause unwanted algal blooms and excessive plant growth whenpresent at elevated levels in water bodies. Sources include decomposition of animal andplant proteins, agricultural and urban runoff, and effluent from waste-water treatmentplants.

Phosphorus, orthophos-phate

-- Dense algal blooms or rapid plant growth can occur in waters rich in phosphorus. A limitingnutrient for eutrophication since it is typically in shortest supply. Sources are human andanimal wastes and fertilizers.

Arsenic 110 g/L

MCL

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

slowly excreted. Can cause nasal ulcers; damage to the kidneys, liver, and intestinalwalls; and death. Recently suspected to be a carcinogen (Garold Carlson, U.S. Environ-mental Protection Agency, written commun., 1998).

Barium 2,000 g/LMCL

Toxic; used in rat poison. In moderate to large concentrations can cause death; smaller con-centrations can cause damage to the heart, blood vessels, and nerves.

Boron -- Essential to plant growth, but may be toxic to crops when present in excessive concentra-tions in irrigation water. Sensitive plants show damage when irrigation water containsmore than 670 g/L and even tolerant plants may be damaged when boron exceeds2,000 g/L. The recommended limit is 750 g/L for long-term irrigation on sensitivecrops (U.S. Environmental Protection Agency, 1986).

Cadmium 5 g/LMCL

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.Copper 1,300 g/L

(action level)Essential to metabolism; copper deficiency in infants and young animals results in nutri-

tional anemia. Large concentrations of copper are toxic and may cause liver damage.Moderate levels of copper (near the action level) can cause gastro-intestinal distress. Ifmore than 10 percent of samples at the tap of a public water system exceed 1,300 g/L,the USEPA requires treatment to control corrosion of plumbing materials in the system.

Table 4 . Water-quality criteria, standards, or recommended limits for selected properties and constituentsContinued[All standards are from U.S. Environmental Protection Agency (1994a) unless noted. MCL, Maximum Contaminant Level; SMCL, Secondary MaximumContaminant Level; USEPA, U.S. Environmental Protection Agency; mg/L, milligrams per liter; S/cm, microsiemens per centimeter at 25 degrees Celsius;g/L, micrograms per liter; pCi/L, picocuries per liter; --, no limit established]

Constituentor property Standard Significance


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Iron 300 g/LSMCL

Forms rust-colored sediment; stains laundry, utensils, and fixtures reddish brown. Objec-tionable for food and beverage processing. Can promote growth of certain kinds ofbacteria that clog pipes and well openings.

Lead 15 g/L(action level)

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 in10 samples of a public supply exceed 15 g/L, the USEPA recommends treatment toremove lead and monitoring of the water supply for lead content (U.S. EnvironmentalProtection Agency, 1991).

Lithium -- Reported as probably beneficial in small concentrations (250-1,250 g/L). Reportedly mayhelp 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 g/LSMCL

Causes gray or black stains on porcelain, enamel, and fabrics. Can promote growth of cer-tain kinds of bacteria that clog pipes and wells.

Mercury (inorganic) 2 g/LMCL No known essential or beneficial role in human or animal nutrition. Liquid metallic mer-cury and elemental mercury dissolved in water are comparatively nontoxic, but somemercury compounds, such as mercuric chloride and alkyl mercury, are very toxic.Elemental mercury is readily alkylated, particularly to methyl mercury, and concentratedby biological activity. Potential health effects of exposure to some mercury compoundsin water include severe kidney and nervous system disorders (U.S. EnvironmentalProtection Agency, 1994b).

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

Selenium 50 g/LMCL

Essential to human and animal nutrition in minute concentrations, but even a moderateexcess may be harmful or potentially toxic if ingested for a long time (Callahan andothers, 1979). Potential human health effects of exposure to elevated selenium concentra-tions include liver damage (U.S. Environmental Protection Agency, 1994b).

Silver 100 g/LSMCL Causes permanent bluish darkening of the eyes and skin (argyria). Where found in water isalmost always from pollution or by intentional addition. Silver salts are used in somecountries to sterilize water supplies. Toxic in large concentrations.

Strontium -- Importance in human and animal nutrition is not known, but believed to be essential. Toxic-ity believed very minimalno more than that of calcium.

Zinc 5,000 g/LSMCL

Essential and beneficial in metabolism; its deficiency in young children or animals willretard growth and may decrease general body resistance to disease. Seems to have no illeffects even in fairly large concentrations (20,000-40,000 mg/L), but can impart a metal-lic taste or milky appearance to water. Zinc in drinking water commonly is derived fromgalvanized coatings of piping.

Gross alpha-particleactivity

15 pCi/LMCL

The measure of alpha-particle radiation present in a sample. A limit is placed on grossalpha-particle activity because it is impractical at the present time to identify all alpha-

particle-emitting radionuclides due to analytical costs. Gross alpha-particle activity is aradiological hazard. The 15 pCi/L standard also includes radium-226, a known carcino-gen, but excludes any uranium or radon that may be present in the sample. Thorium-230radiation contributes to gross alpha-particle activity.

Beta-particle andphoton activity (formerly manmaderadionuclides)

4 millirem/yrMCL

(under review)

The measure of beta-particle radiation present in a sample. Gross beta-particle activity is aradiological hazard. See strontium-90 and tritium.




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Radium-226 & 228combined

5 pCi/LMCL

Radium locates primarily in bone; however, inhalation or ingestion may result in lungcancer. Radium-226 is a highly radioactive alkaline-earth metal that emits alpha-particleradiation. It is the longest lived of the four naturally occurring isotopes of radium and is adisintegration product of uranium-238. Concentrations of radium in most natural watersare usually less than 1.0 pCi/L (Hem, 1985).

Radon 2 300 or 4,000pCi/L

proposed MCL

Inhaled radon is known to cause lung cancer (MCL for radon in indoor air is 4 pCi/L).Ingested radon also is believed to cause cancer. A radon concentration of 1,000 pCi/L inwater is approximately equal to 1 pCi/L in air. The ultimate source of radon is the radio-active decay of uranium. Radon-222 has a half-life of 3.8 days and is the only radon iso-tope of importance in the environment (Hem, 1985).

Strontium-90 (contributes to beta-particle and photonactivity)

Gross beta-particle activity(4 millirem/yr)

MCL

Strontium-90 is one of 12 unstable isotopes of strontium known to exist. It is a product ofnuclear fallout and is known to cause adverse human health affects. Strontium-90 is abone seeker and a relatively long-lived beta emitter with a half-life of 28 years. TheUSEPA has calculated that an average annual concentration of 8 pCi/L will produce atotal body or organ dose of 4 millirem/yr (U.S. Environmental Protection Agency, 1997).

Thorium-230 (contributes to grossalpha-particleactivity)

15 pCi/LMCL

Thorium-230 is a product of natural radioactive decay when uranium-234 emits alpha-particle radiation. Thorium-230 also is a radiological hazard because it is part of theuranium-238 decay series and emits alpha-particle radiation through its own naturaldecay to become radium-226. The half-life of thorium-230 is about 80,000 years.

Tritium ( 3H) (contributes to beta-particle and photonactivity)

Gross beta-particle activity(4 millirem/yr)

MCL

Tritium occurs naturally in small amounts in the atmosphere, but largely is the product ofnuclear weapons testing. Tritium can be incorporated into water molecules that reach theEarths surface as precipitation. Tritium emits low energy beta particles and is relativelyshort-lived with a half-life of about 12.4 years. The USEPA has calculated that a concen-tration of 20,000 pCi/L will produce a total body or organ dose of 4 millirem/yr (CFR 40Subpart B 141.16, revised July 1997, p. 296).

Uranium 30 g/LMCL

(under review)

Uranium is a chemical and radiological hazard and carcinogen. It emits alpha-particle radi-ation through natural decay. It is a hard, heavy, malleable metal that can be present inseveral oxidation states. Generally, the more oxidized states are more soluble. Uranium-238 and uranium-235, which occur naturally, account for most of the radioactivity inwater. Uranium concentrations range between 0.1 and 10 g/L in most natural waters.

1USEPA currently is implementing a revised MCL for arsenic from 50 to 10 g/L; public-water systems must meet the revised MCL by January2006 (U.S. Environmental Protection Agency, 2001).

2USEPA currently is working to set an MCL for radon in water. The proposed standards are 4,000 pCi/L for States that have an active indoor air pro-gram and 300 pCi/L for States that do not have an active indoor air program (Garold Carlson, U.S. Environmental Protection Agency, oral commun.,1999). At this time, it is not known whether South Dakota will participate in an active indoor air program (Darron Busch, South Dakota Department ofEnvironment and Natural Resources, oral commun., 1999).




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General Characteristics for Major Aquifers

A summary of water-quality characteristics fromWilliamson and Carter (2001) for the major aquifers inthe study area (Deadwood, Madison, Minnelusa,Minnekahta, and Inyan Kara aquifers) is presented inthis section. Characteristics for the Precambrianaquifer also are included in this section because

numerous wells are completed in this aquifer in thecrystalline core of the Black Hills.

Most pH values for the major aquifers are withinthe specified range for the SMCL (6.5 to 8.5 standardunits). About 13 percent of the samples from wellscompleted in Precambrian rocks had pH values lessthan the lower limit specified for the SMCL, whichindicates acidity. In general, pH values are lower inwells completed in Precambrian rocks than in the othermajor aquifers, which is indicative of a unit containinglittle carbonate material.

Water temperatures generally increase with welldepth. The deepest wells in the study area are com-pleted in the Madison aquifer; thus, measured temper-atures in the Madison aquifer generally are the warmestof the major aquifers. The Madison aquifer is theprimary source of water to warm artesian springs in thesouthern Black Hills, where water temperatures may beinfluenced by factors other than aquifer depth (Whalen,1994).

Williamson and Carter (2001) quantified rela-tions between dissolved solids and specific conduc-

tance concentrations for the major aquifers. The r2 (coefficient of determination) values are high for all of

the major aquifers (fig. 31); thus, the equations pro-vided could be used confidently for estimating dis-solved solids concentrations from specific conductancemeasurements.

Specific conductance generally is low in waterfrom the Precambrian, Deadwood, and Minnekahtaaquifers. Dissolved constituents tend to increase withresidence time as indicated by the general increase inspecific conductance in the Madison aquifer with dis-

tance from the outcrop (fig. 32). Generally, water fromthe Inyan Kara aquifer is high in specific conductanceeven in some outcrop areas and is higher in specificconductance than the other major aquifers due togreater amounts of shale within the Inyan Kara Group.Water obtained from shales may contain rather highconcentrations of dissolved solids (Hem, 1985) and,hence, high specific conductance.

Geologic units that contain little carbonatematerial, such as the Precambrian rocks, generally con-tain water with lower carbonate hardness and alkalinitythan geologic units that are composed primarily of car-bonate rocks. Water in the Madison, Minnelusa, andMinnekahta aquifers generally is hard to very hardbecause these units consist primarily of carbonaterocks. Water in the Deadwood aquifer also is hard tovery hard because this unit consists primarily of sand-stone with a calcium carbonate cement. The Inyan Karaaquifer may yield soft water, with hardness generallydecreasing with increasing distance from the outcrop(fig. 33). Although concentrations of dissolved solidsin the Inyan Kara aquifer actually increase withincreasing distance from the outcrop, hardnessdecreases because calcium and bicarbonate arereplaced by sodium and sulfate as water moves down-gradient.

In the Black Hills area, water from the major

aquifers generally is low in dissolved solids in and nearoutcrop areas. The Madison, Minnelusa, and InyanKara aquifers may yield slightly saline water (dis-solved solids concentrations between 1,000 and3,000 mg/L) at distance from the outcrops, especiallyin the southern Black Hills. The water in these aquifersgenerally is highly mineralized outside of the BlackHills area, as previously described and shown infigure 17 for aquifers in the Paleozoic units.

Many of the major aquifers yield a calciumbicarbonate type water in and near outcrop areas, withconcentrations of sodium, chloride, and sulfateincreasing with distance from outcrops. High concen-trations of sodium, chloride, and sulfate occur in theMadison aquifer (fig. 34) in the southwestern part ofthe study area relative to the rest of the study area.These high concentrations could be due to long resi-dence times, long flowpaths associated with regionalflow from the west (Wyoming), or greater amounts ofevaporite minerals, such as anhydrite and gypsum,available for dissolution (Naus and others, 2001). In thesouthern part of the study area, the common-ion chem-istry of the water in the Minnelusa aquifer also is char-

acterized by higher concentrations of sodium andchloride (fig. 35). The high chloride concentrations inthis area could reflect hydraulic connection betweenthe Madison and Minnelusa aquifers (Naus and others,2001). The dissolution of evaporite minerals and longresidence time also are possible explanations for theoccurrence of this water type in the Minnelusa aquifer(Naus and others, 2001).


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Figure 31 . Relations between dissolved solids and specific conductance for the major aquifers.

0 1,500500 1,0000

800

200

400

600

Precambrian aquifer

0 4,0001,000 2,000 3,0000

2,000

500

1,000

1,500

D I S S O L V E D S O L I D S ( S ) , I N M I L L I G R A M S P E R L I T E R

0 5,0001,000 2,000 3,000 4,0000

4,000

1,000

2,000

3,000

0 4,0001,000 2,000 3,000

SPECIFIC CONDUCTANCE (K),IN MICROSIEMENS PER CENTIMETER

0

2,500

500

1,000

1,500

2,000

0 6,0001,000 2,000 3,000 4,000 5,000


0

4,000

1,000

2,000

3,000

Madison aquifer

S = 0.6091K - 3.73r2 = 0.98

N = 91

S = 0.6151K - 14.42r2 = 0.91N = 39

0 1,000200 400 600 8000

500

100

200

300

400

Deadwood aquifer

Minnelusa aquifer

S = 1.0070K - 215.09r2 = 0.98

N = 159

Minnekahta aquifer Inyan Kara aquifer

S = 0.8860K - 177.62r2 = 0.99N = 25

S = 0.7842K - 98.49r2 = 0.95N = 85

S = 0.5792K - 1.93r2 = 0.97N = 33


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Figure 32 . Distribution of specific conductance in the Madison aquifer (modified from Williamson and Carter, 2001).

B U T T E C O

LA W RE N C E C O M E A D E CO

P E N N ING T O N C O

CU ST E R C O

F A LL RI V E R C O

W Y O M I N G

S O U T H

D A K O T A

N . F

o r k R

a p

i

d C r

Belle Fourche Reservoir

F O U R C H E

V i c t o r i a S pr i n g

R h o a

d s F o r k

C o o l i d g e

H igh l a n d

Angostura Reservoir

C a s t l e

C r

N .

F o r k C a s t l e C r

H e l l

C a n y o

n C a n y o n

R e d

B e a r

G u l c h

C r e e k

C r o w

Sheridan Lake

H o t B r o o k C a n y o n

Cox Lake

Deerfield Reservoir

Pactola Reservoir

I n d i a n C r

H o r s e

C r e e k

O w l

C r e e k B E L L E

R I V E R

R E D W A T E R R

I V E R

C r e e k

C r

L i t t l e

S p e a r f i s h

S p e a

r f i s h

C r e e k

S p e a r f i s h W h

i t e w o o d

C r e e k

C r e e k

B e a r

B u t t e

E l k

E l k

C r e e k

C r e e k

C r e e k

B o x e l d e r

R a p i d

R a p i d

C r e e k

C r e e k C r e e

k

S p r i n

g

C r e e k

F r e n c h

C r e e k

C r e e k

C r e e k

G r a c e

C r e e k

C re ek

C r e e k

S . F o r k

G i l l e t t

e

S . F o r k R a p i d C r

B a t t l e

F r e n c h

B e a v e r

B e a v e r

C r e e k

C r e e k

C r e e k

C r e e k

C r e e k

F a l l R

H a t

C r e e k

C r e e k

H o r s e h e a d

C H E Y E N N E

R I V E R

C o t t o n w

o o d

C r e e k

H ay

B o t t o m

F a l s e

C r ee k

S p o k a n e

L a m e

J o h n n y

H i g g i n s

B e a v e r

C r

W h i t

e t a i l

C r

Cr

C r C r

G u l c h

A n ni e

S q u a w

D e a d

w o o d

C r e e k

A l k a l i I r o n Cr

E l k

Lit t l e C r e

e k

C a s t l e

C a s t l

eC r e e k C r e e

k

B e a r G ulch

C rS tr a w b e r r y

B o l e

s C a n y o n C a

n yo n

R e d b i r d

C a n y o

n

C o l d

B e a v e r

S p r i n g s C r e e k

C r e e k

Whitewood

Sp ea rfish

Sa intOnge

DEADWOOD

Le ad

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elde r

HillCity

He rmosa

CUS TER

HO T SP RINGS

Edgemont

Minnekahta

Tinton Centr a lCity

Rou baix

Nemo

Va le

Nis land

Ha yward

Ke ys tone

Roch ford

P ring le

Fairburn

Buffalo Gap

Dewey

Ca sc a deS prings

IglooProvo

Oral

Rockerville

RAP ID CI TY

L I M E S T O N E P L A T E A

U

Wind C aveNa tiona l Park

Je wel Cav eNatio nal

Monum ent

Mt . Rush moreNational

Mem orial

CUST ER

S TATE

PA RK

WindCave

HarneyPeak

x

Ellsw orthAir ForceBa se

0 10 20

0 10 20 MILES

KILOMETERS

EXPLANATIONOUTCROP OF MADISON LIME- STONE (from Strobel and others, 1999)

MADISON LIMESTONE ABSENT (from Carter and Redden, 1999d)

Less than 500

500 to 1,000

1,000 to 1,500

Greater than 1,500

SPECIFIC CONDUCTANCE OF SAMPLE, IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIUS--Circle size increases with increasing concentrations

104 o 45' 103o30'

15' 103 o

30'

44 o45'

15'

44 o

45'

30'

43 o15'

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


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Figure 33 . Distribution of hardness in the Inyan Kara aquifer (modified from Williamson and Carter, 2001).

N . F

o r k R

a p

i

d C r


F O U R C H E


R h o a

d s F o r k

C o o l i d g e

H igh l a n d

Ango stura Reservoir

C a s t l e

C r

N . F o r

k C a s t l e C r

H e l l

C a n y o

n C a n y o n

R e d

B e a r

G u l c h

C r e e k

C r o w

Sheridan Lake


Cox Lake

Deerfield Reservoir

Pactola Reservoir

I n d i a n C r

H o r s e

C r e e k

O w l

C r e e k B E L L E

R I V E R

R E D W A T E R R

I V E R

C r e e k

C r

L i t t l e

S p e a r f i s h

S p e a

r f i s h

C r e e k


i t e w o o d

C r e e k

C r e e k

B e a r

B u t t e

E l k

E l k

C r e e k

C r e e k

C r e e k

B o x e l d e r

R a p i d

R a p i d

C r e e k

C r e e k C r e e

k

S p r i n

g

C r e e k

F r e n c h

C r e e k

C r e e k

C r e e k

G r a c e

C r e e k

C r e e k

C r e e k

S . F o r k

G i l l e t t

e


B a t t l e

F r e n c h

B e a v e r

B e a v e r

C r e e k

C r e e k

C r e e k

C r e e k

C r e e k

F a l l R

H a t

C r e e k

C r e e

k H o r s e h e a d

C H E Y E N N E

R I V E R

C o t t o n w

o o d

C r e e k

Hay

B o t t o m

F a l s e

C r ee k

S p o k a n e

L a m

e

J o h n n y

H i g g i n s

B e a v e r

C r

W h i t e

t a i l

C r

Cr

C r C r

G u l c h

A n ni e

S q u a w

D e a d

w o o d

C r e e k

A l k a l i I r o n C r

E l k

Lit t l e C r ee

k

C a s t l e

C a s t l

eC r e e k C r e e

k

B e a r G ulch


B o l e

s C a n y o n C a

n yo n

R e d b i r d

C a n y o

n

C o l d

B e a v e r


C r e e k

Whitew ood

Spea rfish

S aintOng e

DEADWOOD

Lead

BELLE FOURCHE

New ell

STURGIS

Blackhawk

Pied mont

Tilford

Box Elde r

Hill City

Her mosa

CUS TER

HO T S P RINGS

Edgemont

Minne kahta

Tinton Ce ntralCity

Rouba ix

Ne mo

Vale

Nislan d

Haywa rd

Keyst on e

Rochford

Pringle

Fa irburn

Buffalo Gap

Dewey

Cas ca deS pring s

IglooProvo

Oral

Rockerville

RA PID C ITY


U

Wind CaveNational P ark

Jew el C aveNation al

Monum ent

Mt. Rushm oreNational

Memo rial

CUSTE R

ST ATE

PAR K

WindCave

HarneyPeak

x

EllsworthA ir ForceBase

B UT TE C O

LA W R E N C E CO M EA D E C O

P EN NI N G TO N C O

C U S T E R C O

F AL L R IV ER C O

W Y O M I N G

S O U T H

D A K

O T A

0 10 20

0 10 20 MILES

KILOMETERS

EXPLANATION

Very hard (greater than 180)

WATER HARDNESS, IN MILLIGRAMS PER LITER

Hard (121 to 180)

Moderately hard (61 to 121)

Soft (less than 61)

WELL COMPLETED IN INYAN KARA AQUIFER FOR WHICH THERE IS A HARDNESS ANALYSIS

OUTCROP OF INYAN KARA GROUP (from Strobel and others, 1999)

INYAN KARA GROUP ABSENT (from Carter and Redden, 1999a)

104 o 45' 103o30'

15' 103 o

30'

44 o45'

15'

44 o

45'

30'

43 o15'



9/16


Figure 34 . Stiff diagrams (Stiff, 1951) showing the distribution of common-ion chemistry in the Madison aquifer (from Naus and others, 2001).

N . F

o r k R

a p

i

d C r


F O U R C H E


R h o a

d s F o r k

C o o l i d g e

H igh l a n d

Angostu ra Reserv oir

C a s t l e

C r

N . F o r k C a s t l

e C r

H e l l

C a n y o n

C a n y o n

R e d

B e a r

G u l c h

C r e e k

C r o w

Sheridan Lake


Cox Lake

Deerfield Reservoir

Pactola Reservoir

I n d i a n C r

H o r s e

C r e e k

O w l

C r e e k B E L L E

R I V E R

R E D W A T E R R

I V E R

C r e e k

C r

L i t t l e

S p e a r f i s h

S p e a

r f i s h

C r e e k


i t e w o o d

C r e e k

C r e e k

B e a r

B u t t e

E l k

E l k

C r e e k

C r e e k

C r e e k

B o x e l d e r

R a p i d

R a p i d

C r e e k

C r e e k C r e e

k

S p r i n

g

C r e e k

F r e n c h

C r e e

k

C r e e k

C r e e k

G r a c e

C r e e k

C r e e k

C r e e k

S . F o r k

G i l l e t t

e


B a t t l e

F r e n c h

B e a v e r

B e a v e r

C r e e k

C r e e k

C r e e k

C r e e k

C r e e k

F a l l R

H a t

C r e e k

C r e e k

H o r s e h e a d

C H E Y E N N E

R I V E

R

C o t t o n w

o o d

C r e e k

Ha y

B o t t o m

F a l s e

C r ee k

S p o k a n e

L a m e

J o h n n y

H i g g i n s

B e a v e r

C r

W h i t

e t a i l

C r

Cr

C r C r

G u l c h

A n ni e

S q u a w

D e a d

w o o d

C r e e k

A l k a l i I r o n C r

E l k

Lit t l e C r ee

k

C a s t l e

C a s t l

eC r e e k C r e e

k

B e a r G ulch


B o l e

s C a n y o n C a

n yo n

R e d b i r d

C a n y o

n

C o l d

B e a v e r


C r e e k

White wood

S pea rfish

Sa intOnge

DEADWOOD

Lea d

BELLE FOURCHE

Ne well

STURGIS

Blackhawk

Piedm ont

Tilford

Box Elde r

Hill City

Her mosa

CUSTER

HO T S P RINGS

Edgemont

Minne kahta

Tinton CentralCity

Rouba ix

Ne mo

Vale

Nisla nd

Ha yward

Keyst one

Roc hford

Pring le

Fa irburn

Buffa lo Gap

Dew e y

Ca sc a deS prings

IglooProvo

Oral

Rockerville

RA PI D C IT Y

L I M E S T O N E P L A T E

A U

Wind Cav eNation al Par k

Jewe l Ca veNat iona l

Monu men t

M t. RushmoreNatio nal

Memorial

CUS TER

STAT E

PARK

WindCave

HarneyPeak

x

EllsworthAir ForceBase

BU TT E CO

LAW R EN CE C O ME AD E C O

PE NN IN GT ON C O

C U S TE R CO

FA LL R IVE R C O

W Y O M I N G

S O U T H

D A

K O T A

0 10 20

0 10 20 MILES

KILOMETERS

EXPLANATIONOUTCROP OF THE MADISON LIME- STONE (from Strobel and others, 1999)

MADISON LIMESTONE ABSENT (from Carter and Redden, 1999d)

STIFF DIAGRAM--

WELL COMPLETED IN THEMADISON AQUIFER

Sodium + Potassium

Calcium

Magnesium

Chloride + Fluoride

Bicarbonate + Carbonate

Sulfate10 100

CONCENTRATION, IN MILLIEQUIVALENTS PER LITER

LIMESTONE HEADWATER SPRING

104 o 45' 103o30'

15' 103 o

30'

44 o45'

15'

44 o

45'

30'

43o

15'

ARTESIAN SPRING



10/16


Figure 35 . Stiff diagrams (Stiff, 1951) showing the distribution of common-ion chemistry in the Minnelusa aquifer.Approximation location of anhydrite dissolution front showing transition between low and high sulfate concentrationsalso is shown (from Naus and others, 2001).

N . F

o r k R

a p

i

d C r


F O U R C H E


R h o a

d s F o r k

C o o l i d g e

H igh l a n d

Angostura Reservoir

C a s t l e

C r

N . F o r k

C a s t l e C r

H e l l

C a n y o

n C a n y o n

R e d

B e a r

G u l c h

C r e e k

C r o w

Sheridan Lake


Cox Lake

Deerfield Reservoir

Pactola Reservoir

I n d i a n C r

H o r s e

C r e e k

O w l

C r e e k B E L L E

R I V E R

R E D W A T E R R

I V E R

C r e e k

C r

L i t t l e

S p e a r f i s h

S p e a

r f i s h

C r e e k


i t e w o o d

C r e e k

C r e e k

B e a r

B u t t e

E l k

E l k

C r e e k

C r e e k

C r e e k

B o x e l d e r

R a p i d

R a p i d

C r e e k

C r e e k C r e e

k

S p r i n

g

C r e e k

F r e n c h

C r e e k

C r e e k

C r e e k

G r a c e

C r e e k

C r e ek

C r e e k

S . F o r k

G i l l e t t

e


B a t t l e

F r e n c h

B e a v e r

B e a v e r

C r e e k

C r e e k

C r e e k

C r e e k

C r e e k

F a l l R

H a t

C r e e k

C r e e

k H o r s e h e a d

C H E Y E N N E

R I V E R

C o t t o

n w o o

d

C r e e k

H ay

B o t t o m

F a l s e

C r ee k

S p o k a n e

L a m e

J o h n n y

H i g g i n s

B e a v e r

C r

W h i t

e t a i l

C r

Cr

C r C r

G u l c h

A n ni e

S q u a w

D e a d

w o o d

C r e e k

A l k a l i I r o n Cr

E l k

Lit t l e C r e

e k

C a s t l e

C a s t l

eC r e e k C r e e

k

B e a r G ulch

C rS tra w b e r r y

B o l e

s C a n y o n C a

n yo n

R e d b i r d

C a n y o

n

C o l d

B e a v e r


C r e

e k

Whitewood

S pe arfish

S aintOnge

DEADWOOD

Lead

BELLE FO URCHE

Ne we ll

S TURGIS

Blackhawk

P iedmont

Tilford

Box Elder

Hill City

Hermosa

CUSTER

HO T S PRINGS

Edgemont

Minnekahta

Tinton Centr a lCity

Roub aix

Nemo

Vale

Nis land

Hay wa rd

Keys tone

Roch ford

P ringle

Fa irburn

Buffalo Gap

De wey

Ca scadeSprings

IglooProvo

Oral

Rockerville

R AP ID CIT Y


U

Wind CaveNa tiona l Park

Je wel Cav eNational

Monum ent

M t. Rus hmoreNational

Mem orial

CUSTER

S TAT E

PA RK

WindCave

HarneyPeak

x

Ells worthAir ForceBase

B U T T E C O

LA W R E N C E C O M E A D E CO

P E N N IN G T O N C O

CU S T E R C O

FA LL RI V E R CO

W Y O M I N G

S O U T H

D A K

O T A

0 10 20

0 10 20 MILES

KILOMETERS

Less than 250

ESTIMATED SULFATE CONCEN- TRATIONS IN MINNELUSA AQUIFER, IN MILLIGRAMS PER LITER

250 to 1,000Greater than 1,000

EXPLANATIONOUTCROP OF MINNELUSA FORMATION (from Strobel and others, 1999)

MINNELUSA FORMATION ABSENT (from Carter and Redden, 1999c)

STIFF DIAGRAM--

WELL COMPLETED IN THEMINNELUSA AQUIFER

Sodium + Potassium

Calcium

Magnesium

Chloride + Fluoride

Bicarbonate + Carbonate

Sulfate

10 100

CONCENTRATION, IN MILLIEQUIVALENTS PER LITER

104 o 45' 103o30'

15' 103 o

30'

44 o45'

15'

44 o

45'

30'

43 o15'

LIMESTONE HEADWATER SPRING

ARTESIAN SPRING



11/16


Sulfate concentrations in the Minnelusa aquiferare dependent on the amount of anhydrite present in theMinnelusa Formation. Near the outcrop, sulfate con-centrations generally are low (less than 250 mg/L)because anhydrite has been removed by dissolution. Anabrupt increase in sulfate concentrations occurs down-gradient, where a transition zone surrounds the core ofthe Black Hills. This transition zone is the area withinwhich the sulfate concentrations range from 250 to1,000 mg/L (fig. 35) and marks an area of activeremoval of anhydrite by dissolution. Downgradientfrom the transition zone, sulfate concentrations aregreater than 1,000 mg/L, which delineates a zone inwhich thick anhydrite beds remain in the formation.The transition zone probably is shifting downgradientover geologic time as the anhydrite in the formation isdissolved (Kyllonen and Peter, 1987).

Figures 34 and 35 also show Stiff diagrams(Stiff, 1951) for artesian springs in the Black Hills area,

most of which probably originate from the Madisonand/or Minnelusa aquifers (Naus and others, 2001).Artesian springs with high sulfate concentrations prob-ably are influenced by anhydrite in the MinnelusaFormation. Artesian springs with low sulfate concen-trations occur only upgradient from the transition zone(fig. 35). Additional discussions regarding potentialsources of artesian springs are presented in subsequentsections of the report.

Concentrations and variability of many traceelements are small in the major aquifers. Strontiumgenerally has higher concentrations than other traceelements, but is not harmful. Similarly, barium, boron,iron, manganese, lithium, and zinc concentrations alsomay be high in comparison to other trace elements.

Most naturally occurring radionuclides in waterare the result of radioactive decay of uranium-238,thorium-232, and uranium-235, with uranium-238 pro-ducing the greatest part of the radioactivity observed(Hem, 1985). In general, gross alpha-particle activity,gross-beta activity, and radium-226 concentrations, arehigher in the Deadwood and Inyan Kara aquifers thanin the Madison, Minnelusa, and Minnekahta aquifers.

In the Deadwood aquifer, more than 30 percentof the samples analyzed for radium-226 or radium-226and radium-228 exceeded the MCL of 5 pCi/L for thecombined radium-226 and radium-228 standard.Almost 90 percent of the samples from the Deadwoodaquifer exceeded the proposed MCL of 300 pCi/L forradon in States without an active indoor air program;several of these samples (fig. 36) also exceeded the

proposed MCL of 4,000 pCi/L for radon in States withan active indoor air program. Samples from the Dead-wood aquifer have lower uranium concentrations rela-tive to the other major aquifers, which may be due tothe reducing conditions of the Deadwood aquifer(Rounds, 1991).

Uranium deposits have been mined in the InyanKara Group in the southern Black Hills. Uranium maybe introduced into the Inyan Kara Group throughupward leakage of water from the Minnelusa aquifer(Gott and others, 1974). As water in the Inyan Karaaquifer migrates downgradient, geochemical condi-tions favor the precipitation of uranium (Gott andothers, 1974). Some water from the Inyan Kara aquifer,especially in the southern Black Hills, contains rela-tively high concentrations of radionuclides. Almost20 percent of the samples collected from the InyanKara aquifer exceeded the MCL for the combinedradium-226 and radium-228 standard; all but one of

these samples exceeding the MCL were from wells inthe southern Black Hills. About 4 percent of thesamples exceeded the MCL for uranium; all thesesamples exceeding the MCL were from wells located inthe southern Black Hills.

General Characteristics for Minor Aquifers

Water-quality characteristics were summarizedby Williamson and Carter (2001) for various minoraquifers. The minor aquifers in the study area includethe Newcastle aquifer and alluvial aquifers. Local aqui-fers do exist in the various semiconfining and confiningunits. Water-quality data also were summarized forseveral of these local aquifers, which included theSpearfish, Sundance, Morrison, Graneros, and Pierreaquifers.

Relations between dissolved solids and specificconductance concentrations are presented in figure 37for the minor aquifers with sufficient data, whichinclude the Sundance, Morrison, Newcastle, andalluvial aquifers. The r 2 values are consistently high,indicating strong correlations for these aquifers.

Water in many of the minor aquifers can be very

hard and high in dissolved solids concentrations. Mostsamples from the Sundance aquifer indicate slightlysaline water. Sulfate concentrations also can be high inthe minor aquifers, such as the Spearfish aquifer wherehigh sulfate concentrations can result from dissolutionof gypsum. Both dissolved solids and sulfate concen-trations are low in the Newcastle aquifer. A variety ofwater types can occur within and among the minor


12/16


13/16


aquifers. In general, the dominance of sodium and sul-fate increases with increasing amounts of shale presentin the formations due to the large cation-exchangecapabilities of clay minerals (generally sodium concen-trations increase) and due to the reduced circulation ofwater through the shale (Hem, 1985). The dominanceof calcium, magnesium, and bicarbonate increases withincreasing amounts of sandstone (where calcium car-bonate commonly is the cementing material) andcarbonate rocks present in the geologic units. TheSundance aquifer has the highest selenium concentra-tions of all aquifers considered in this report.

Concentrations of common ions in alluvialaquifers generally increase with increasing distance

from the core of the Black Hills, which is largely due tocontact of the water with underlying geologic units andto the composition of alluvial deposits. Wells com-pleted in alluvial deposits that do not overlie Creta-ceous shales generally yield fresh water of a calciumbicarbonate or calcium magnesium bicarbonate type.

Wells that are completed in alluvial deposits thatoverlie the Cretaceous shales generally yield slightlysaline water in which sodium and/or sulfate is domi-nant. Water from alluvial aquifers may be high in ura-nium concentrations, especially in the southern BlackHills. About 17 percent of the samples exceeded theproposed MCL for uranium, and all samples exceedingthis MCL were from wells in the southern Black Hills.

Figure 37 . Relations between dissolved solids and specific conductance for the minor aquifers.

Sundance aquifer

D I S S O L V E D

S O L I D S ( S ) , I N M I L L I G R A M S P E R L I T E R



Newcastle aquifer

Morrison aquifer

Alluvial aquifers

0 4,0001,000 2,000 3,0000

2,000

500

1,000

1,500

S = 0.7986K - 129.34r2 = 0.98N = 10

0 1,500500 1,0000

1,000

200

400

600

800

S = 0.7601K - 66.71r2 = 0.98N = 7

0 2,000500 1,000 1,5000

1,000

200

400

600

800

S = 0.7105K - 67.20r2 = 0.98N = 8

0 4,0001,000 2,000 3,0000

2,500

500

1,000

1,500

2,000

S = 0.8302K - 105.62r2 = 0.96N = 64


14/16


Susceptibility to Contamination

The Black Hills Hydrology Study focused pri-marily on determination of natural water-quality char-acteristics, and investigation of contaminationpotential was not an objective of the study. The suscep-tibility of the aquifers to contamination in the studyarea is an important issue, however, and can be

addressed to some extent.Nitrite plus nitrate concentrations for variousaquifers (fig. 38) can provide a general indication ofpossible human influence. Although nitrogen is essen-tial for plant growth, high concentrations of nitrite plusnitrate can cause excessive plant growth and can beharmful to livestock and humans. Excessive concentra-tions of nitrite plus nitrate in drinking water are a healthconcern for pregnant women, children, and the elderly(may cause methemoglobinemia (blue-baby syn-drome) in small children). Nitrite plus nitrate in groundwater can originate from natural processes or as con-

tamination from nitrogen sources, such as fertilizers

and sewage, on the land surface or in the soil zone.Nitrite plus nitrate concentrations for most samples inthe Black Hills area generally are low (fig. 38); how-ever, samples approaching or exceeding the nationalnitrate background concentration of 2.0 mg/L (U.S.Geological Survey, 1999) may provide indications ofpossible human influence in a variety of land-use set-tings. The extreme values for nitrite plus nitrate infigure 38 are unusually high and may reflect poor wellconstruction and surface contamination as opposed toaquifer conditions.

The potential for contamination of ground waterin the Black Hills area can be large because manyaquifer outcrops can be subject to various forms of landdevelopment. Rapid ground-water velocities also arepossible in many aquifers because of high secondarypermeability. Contamination of ground water by septictanks has been documented for wells in the Blackhawk,Piedmont, and Sturgis areas (Bartlett and West

Engineers, Inc., 1998).

Figure 38 . Boxplots of concentrations of nitrite plus nitrate for selected aquifers (modified from Williamson andCarter, 2001).

EXPLANATION

Highest reporting limitMaximum Contaminant Level

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

Number of samples/Number of samples with concentrations below the laboratory reporting limit

114/15

25th percentile

Median

75th percentile

Data value less than or equal to 1.5 times the interquartile range outside the quartile

Outlier data value less than or equal to 3 and more than 1.5 times the interquartile range outside the quartile

Outlier data value more than 3 times the interquartile range outside the quartile

0

20

5

10

15

65

60

N I T R I T E P L U S N I T R A T E

, I N M I L L I G R A M

S P E R L I T E R

40/8 8/4 74/14 157/29 23/4 81/29 9/0 6/4 70/9

AQUIFER

PrecambrianDeadwood

MadisonMinnelusa

MinnekahtaInyan Kara

Sundance AlluvialNewcastle


15/16


Maps showing sensitivity of ground water tocontamination were produced by Putnam (2000) forLawrence County and by Davis and others (1994) forthe Rapid Creek Basin. The most sensitive hydrogeo-logic units are limestones, unconsolidated sands andgravels, and sandstones (Putnam, 2000). The least sen-sitive units include shales or units with interbeddedshales. The Madison, Minnelusa, and Minnekahtaaquifers are especially sensitive to contaminationbecause of high secondary permeability and potentialfor streamflow recharge.

Summary Relative to Water Use

Concentrations of various constituentsexceeding SMCLs and MCLs affect the use of waterin some areas for many aquifers within the study area.Most concentrations exceeding standards are for var-ious SMCLs and generally affect the water only aes-thetically. Radionuclide concentrations can be high insome of the major aquifers, especially in the Deadwoodand Inyan Kara aquifers, and may preclude the use ofwater in some areas. Hard water may require specialtreatment for certain uses. Other factors, such as thesodium adsorption ratio (SAR) and specific conduc-tance, affect irrigation use.

The general suitability of ground water for irri-gation in the study area can be determined by using theSouth Dakota irrigation-water diagram (fig. 39). Thediagram is based on South Dakota irrigation-waterstandards (revised January 7, 1982) and shows theStates water-quality and soil-texture requirements forthe issuance of an irrigation permit. The adjusted SARfor each aquifer was calculated according to Koch(1983) from the mean concentrations of calcium, mag-nesium, sodium, and bicarbonate for each aquifer.Water from all aquifers, with the exceptions of thePierre and Sundance aquifers, generally is suitable forirrigation, but may not be in specific instances if eitherthe specific conductance or the SAR is high.

High concentrations of iron and manganeseoccasionally can hamper the use of water from thePrecambrian aquifer. None of the reported samples

from the Precambrian aquifer exceeded drinking-waterstandards for radionuclides.The principal deterrents to use of water from the

Deadwood aquifer are high concentrations of radionu-clides, including radium-226 and radon. In addition,concentrations of iron and manganese can be high.

Water from the Madison aquifer can contain highconcentrations of iron and manganese that may deter its

use. Water from the Madison aquifer is hard to veryhard and may require special treatment for certain uses.In downgradient wells (generally deeper than 2,000 ft),concentrations of dissolved solids and sulfate also maydeter use from this aquifer. Hot water from deep wellsand in the Hot Springs area, may not be desirable forsome uses. Radionuclide concentrations in theMadison aquifer generally are acceptable.

The principal properties or constituents that mayhamper the use of water from the Minnelusa aquiferinclude hardness and high concentrations of iron andmanganese. Generally, downgradient wells (generallydeeper than 1,000 ft) also have high concentrations ofdissolved solids and sulfate. Hot water, from deepwells, may not be desirable for some uses. Arsenic con-centrations in the Minnelusa aquifer exceed the revisedMCL of 10 g/L in some locations. Only a few samplesexceeded the MCLs for various radionuclides.

Samples from the Minnekahta aquifer are avail-

able only from shallow wells near the outcrop. Waterfrom the Minnekahta aquifer is harder than that fromany of the other major aquifers in the study area, andmay require special treatment for certain uses. Watergenerally is suitable for all water uses; few samplesexceeded SMCLs and no samples available for thisstudy from the Minnekahta aquifer exceeded drinking-water standards for any radionuclides.

The use of water from the Inyan Kara aquifermay be hampered by high concentrations of dissolvedsolids, iron, sulfate, and manganese. In the southernBlack Hills, radium-226 and uranium concentrationsalso may preclude its use. Hard water from wellslocated on or near the outcrop of the Inyan Kara Groupmay require special treatment.

The use of water from the minor aquifers(Spearfish, Sundance, Morrison, Pierre, Graneros,Newcastle, and alluvial aquifers) may be hampered byhardness and concentrations of dissolved solids andsulfate. Concentrations of radionuclides, with theexception of uranium, generally are at acceptable levelsin samples from the minor aquifers. Selenium concen-trations in some places are an additional deterrent to the

use of water from the Sundance aquifer.Water from alluvial aquifers generally is very

hard and may require special treatment for certain uses.High concentrations of dissolved solids, sulfate, iron,and manganese may limit the use of water from alluvialaquifers that overlie the Cretaceous shales. In thesouthern Black Hills, uranium concentrations inalluvial aquifers can be high in many locations.


16/16


Figure 39 . South Dakota irrigation-water classification diagram for selected aquifers (from Williamson and Carter,2001). This diagram is based on South Dakota standards (revised Jan. 7, 1982) for maximum allowable specificconductance and adjusted sodium-adsorption-ratio values for which an irrigation permit can be issued for applyingwater under various soil-texture conditions. Water can 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

C1C2

D1C3

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

S P E C I F I C C O N D U C T A N C E

, I N M I C R O S I E M E N S P E R C E N T I M E T E R A T 2 5 o

C E L S I U S

( E C x

1 0

6 A T 2 5 o

C ) A D J U S T E D

F O R C A L C I U M

, S U L F A T E

, A N D R A I N F A L L

EXPLANATIONSOIL 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 conductance may be

increased by 100 microsiemens

per centimeter at 25C. Average growing season rainfall for the Black Hills area is 14 inches, so the conductance of each plotted value has been reduced by 200 microsiemens per centimeter at 25C. 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 per centimeter at 25C.

ABC

E

1

2

3

AVERAGE CHEMICAL QUALITY OF MAJOR AQUIFERS

AVERAGE CHEMICAL QUALITY OF MINOR AQUIFERS

D

Inyan KaraMinnekahtaMinnelusaMadisonDeadwoodPrecambrian

Alluvial

Graneros

NewcastlePierre

MorrisonSundanceSpearfish

900

800

700

600

500

400

300

200

100

xx

*

# *

#

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