Embed Size (px)
Citation preview
T. 15 S.
T. 16 S.
T. 17 S.
T. 18 S.
T. 19 S.
T. 20 S.
T. 21 S.
T. 22 S.
T. 23 S.
R. 10 W.
T. 24 S.
R. 9 W.
R. 8 W.
R. 7 W.
R. 6 W.
R. 5 W.
R. 4 W.
R. 3 W.
38 45 00
113 00 00112 45 00
112 30 00 112 15 00
39 30 00
39 15 00
39 00 00
Lynndyl
Leamington
Oak City
Sugarville
Sutherland
Delta
Hinckley
Oasis
Deseret
McCornick
Holden
Fillmore
Meadow
Flowell
Kanosh
14
12
7
3
5 6 4
10
8
33
11912
13
32
3435
3638
3739
404142
71
130
131
133
132
134135136
137138
141147
143 142
145
146
144139
140175
176
177178
179
180
183
158
163
164
162159
160161
165
166168
167
169
184
170 171 172
185
186
187188189 173
174196204205
206 211
191197 195198
192194193
199210
208
209207
200
214
215212213
223
224226228227225
229
201202
216
222221
217218
219220
231
203
236
245
260261
266262
265
240
264
244
263237
238 239 241242
243
293
230246247
248249
250255
254
251
252
253 256
276277278
258257
271
259
268
291
270267269
288273
292
294
289280
281
279
284 272
274
283282
290285
275
286 287296297
298299
300301
295306
302303
304 305325326
327
330
328
324
331
307
323
308
322321
332
310311312
314
358357
359
329333
335 334
343344
339340
345346347
341
348
354
338337336
349
350
353
351
352 356355
369
367368
360
361
372 373374
375
376377378379
380
371 370
381
382 384383385386
387
388
389
364
390
319
320
365
366
317
318315
235
234
309
232
233
190
157
67
68
69
70
31
16
17
18
24
2526 27
15
43
55
44
64
56
6561
63
5760
62
5358
5954
52
49
5047 51
48
4546
23
22
30
19
2021
29
28
66
79
78
73
76
75
747772
8283
86
8081
8584
87
88109
108
110
112
111
107106
104
91
125
102
115
105114
113
90
89
93
96 92
99 103
101100
118
959894
97
392120391
393 394
395
116117
119121123122
153124
148151
155
154
149
150
152
156
313
316
182181
FoolCreek
Reservoir
DMADReservoir
GunnisonBend
Reservoir
Cle
ar
La
ke
Beav
er
Rive
r
Sevi
er
River
Sevie
r
Rive
r
DR
UM
MO
UN
TAIN
S
LITTLE D
RU
M M
OU
NTA
INS
C
A
N
Y
O
N
M
O
U
N
T
A
I
N
S
C R
I C
K E
T
M O
U N
T A
I N
S
B L A C K
R O C K
D E S E R T
P
A
H
V
A
N
T
R
A
N
G
E
6
132
125
174
6
125
50
50
6
50
257
257
100
50
15
15
15
15
133
15
LOCATION MAP
MAP OF RECHARGE AND DISCHARGE AREASFOR THE PRINCIPAL BASIN-FILL AQUIFER,SEVIER DESERT, MILLARD COUNTY, UTAH
by Noah P. SnyderDigital compilation by Janine L. Jarva
1 6 1 6 1 6 1 6 1 6 1 6 16
3631
16
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 31
1 636 31
1 636 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311
361
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 316
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36 311 6
36
36 311 6
36 311
36 311 6
36 311 6
36 311 6
36 311 6
36 316
36 311 6
36 311 6
36 311 6
36 311 6
6
36 31
1 6
36 36
311
6
ADMINISTRATIVE OWNERSHIP INSET MAPDigital data from the State Geographic Information Database (SGID)
Ownership
Forest Service
Bureau of Land Management
State of Utah
Native American Reservations
Private Land
Military Reservations
National Parks
State Parks
State Wildlife Reserve
National Recreation Area
National Wildlife Refuge
Forest Service and BLM Wilderness
Public Water Reserve
Bureau of Reclamation
This map was partially funded by the U.S. Environmental ProtectionAgency under the Clean Water Act, Section 319, nonpoint sourceprogram, and by the Utah Department of Environmental Quality,Division of Water Quality.
EXPLANATION
PRIMARY RECHARGE AREA Consolidated rock, usually uplands
PRIMARY RECHARGE AREA Unconsolidated basin fill
SECONDARY RECHARGE AREA
DISCHARGE AREA
Boundary between rechargeareas and discharge areas,dashed where approximate
Boundary of valley fill
Boundary of study area
Boundary of county (servingas boundary of study area)
WELLS Number refers to site number in appendix A
PRIMARY RECHARGE WELLConfining layers not present; wells completed inprincipal aquifer; hydraulic gradient is downward.
SECONDARY RECHARGE WELLConfining layers present; wells completed in prin-cipal aquifer; hydraulic gradient is downward.
DISCHARGE WELLConfining layers present; wells completed in prin-cipal aquifer; hydraulic gradient is upward fromprincipal aquifer to shallow unconfined aquifer.
US Highways
State Highways
County & City Roads
Utah Geological Survey Map 175Recharge and Discharge Areas of the Sevier Desert
SCALE 1:175,0001 0 1 2 3 4 5 6 MILES
5,000 0 5,000 10,000 15,000 20,000 25,000 30,000 FEET
1 0 1 2 3 4 5 6 7 8 9 KILOMETERS
N
Snyder
Recharge and discharge areas, S
evier Desert, M
illard County, U
tahU
GS
Map 175
ISBN 1-55791-620-9
���$��!��916204�
MAP OF RECHARGE AND DISCHARGE AREAS FOR THEPRINCIPAL BASIN-FILL AQUIFER SYSTEMSEVIER DESERT, MILLARD COUNTY, UTAH
byNoah P. Snyder
MAP 175 1998UTAH GEOLOGICAL SURVEYa division ofUtah Department of Natural Resourcesin cooperation withUtah Department of Environmental QualityDivision of Water Quality
STATE OF UTAHMichael O. Leavitt, Governor
DEPARTMENT OF NATURAL RESOURCESKathleen Clarke, Executive Director
UTAH GEOLOGICAL SURVEYM. Lee Allison, Director
UGS BoardMember Representing Russell C. Babcock, Jr. (Chairman) ................................................................................................. Mineral Industry D. Cary Smith .................................................................................................................................. Mineral Industry Craig Nelson .................................................................................................................................. Civil EngineeringE.H. Deedee O’Brien ........................................................................................................................ Public-at-LargeC. William Berge ............................................................................................................................. Mineral IndustryJerry Golden .................................................................................................................................... Mineral IndustryRichard R. Kennedy ................................................................................................. Economics-Business/ScientificDavid Terry, Director, Trust Lands Administration ......................................................................Ex officio member
UTAH GEOLOGICAL SURVEY
The UTAH GEOLOGICAL SURVEY is organized into five geologic programs with Administration, Editorial, and ComputerResources providing necessary support to the programs. The ECONOMIC GEOLOGY PROGRAM undertakes studies to identify coal,geothermal, uranium, hydrocarbon, and industrial and metallic resources; initiates detailed studies of these resources including mining dis-trict and field studies; develops computerized resource data bases, to answer state, federal, and industry requests for information; andencourages the prudent development of Utah’s geologic resources. The APPLIED GEOLOGY PROGRAM responds to requests fromlocal and state governmental entities for engineering-geologic investigations; and identifies, documents, and interprets Utah’s geologichazards. The GEOLOGIC MAPPING PROGRAM maps the bedrock and surficial geology of the state at a regional scale by county andat a more detailed scale by quadrangle. The GEOLOGIC EXTENSION SERVICE answers inquiries from the public and providesinformation about Utah’s geology in a non-technical format. The ENVIRONMENTAL SCIENCES PROGRAM maintains and publish-es records of Utah’s fossil resources, provides paleontological and archeological recovery services to state and local governments, con-ducts studies of environmental change to aid resource management, and evaluates the quantity and quality of Utah’s ground-waterresources.
The UGS Library is open to the public and contains many reference works on Utah geology and many unpublished documents onaspects of Utah geology by UGS staff and others. The UGS has several computer data bases with information on mineral and energyresources, geologic hazards, stratigraphic sections, and bibliographic references. Most files may be viewed by using the UGS Library. TheUGS also manages a sample library which contains core, cuttings, and soil samples from mineral and petroleum drill holes and engineer-ing geology investigations. Samples may be viewed at the Sample Library or requested as a loan for outside study.
The UGS publishes the results of its investigations in the form of maps, reports, and compilations of data that are accessible to thepublic. For information on UGS publications, contact the Natural Resources Map/Bookstore, 1594 W. North Temple, Salt Lake City, Utah84116, (801) 537-3320 or 1-888-UTAH MAP. E-mail: [email protected] and visit our web site at http://www.ugs.state.ut.us.
UGS Editorial StaffJ. Stringfellow ....................................................................................................................................................EditorVicky Clarke, Sharon Hamre...............................................................................................................Graphic ArtistsPatricia H. Speranza, James W. Parker, Lori Douglas...........................................................................Cartographers
The Utah Department of Natural Resources receives federal aid and prohibits discrimination on the basis of race, color, sex, age, national origin, or disability. Forinformation or complaints regarding discrimination, contact Executive Director, Utah Department of Natural Resources, 1594 West North Temple #3710, Box
145610, Salt Lake City, UT 84116-5610 or Equal Employment Opportunity Commission, 1801 L Street, NW, Washington DC 20507.
Printed on recycled paper 10/98
MAP OF RECHARGE AND DISCHARGE AREAS FOR THE PRINCIPALBASIN-FILL AQUIFER SYSTEM, SEVIER DESERT, MILLARD COUNTY, UTAH
by Noah P. Snyder
ABSTRACT
Ground water from the principal unconsolidatedbasin-fill aquifer system is the most important source ofagricultural and culinary water in the Sevier Desert.Recharge and discharge areas for the principal aquifersystem were mapped to aid in management of potentialcontaminant sources to help protect ground-waterquality.
The Sevier Desert is on the eastern edge of theGreat Basin in east-central Utah. The basin fill consistsof lacustrine, deltaic, and alluvial deposits that formaquifers and confining layers. Fractured volcanic rocksare important aquifers in the southern part of the studyarea. The mountains that surround the Sevier Desertand coarse-grained alluvial fans along the basin'seastern edge make up the primary recharge area.Secondary recharge and discharge areas are on thebasin floor, where the principal aquifer system is undergenerally artesian conditions. Water levels in theprincipal aquifer system declined from the 1940s to the1960s when discharge, principally for irrigation,exceeded recharge from precipitation. Water levelsrose during wet years in the early to mid-1980s. Along-term decline in water quality is due toconcentration of dissolved solids by evaporation,recycling of irrigation water, and recharge by lowerquality water.
INTRODUCTION
Background
Ground water from wells is vital to the economyof the Sevier Desert. Springs and streams do notprovide sufficient water to meet the agricultural andculinary needs of the area. The principalunconsolidated basin-fill aquifer system, hereafterreferred to as the principal aquifer system, is the mostimportant source of ground water. Recharge to theprincipal aquifer system is from infiltration of surfacewater, precipitation, and irrigation water near mountain The scope of work included a search for well-logfronts. Recharge areas are typically underlain by data, a literature review, and field reconnaissance tofractured rock and/or coarse-grained sediment having define general geologic and hydrologic conditions in
relatively little ability to inhibit infiltration or renovatecontaminated water. Ground-water flow in rechargeareas has a downward component and relatively fastrate of movement. Because contaminants can readilyenter an aquifer system in recharge areas,management of potential contaminant sources in theseareas deserves special attention to protect ground-water quality. Ground-water recharge-area mappingdefines these vulnerable areas.
Ground-water recharge-area maps typicallyshow: (1) primary recharge areas, (2) secondaryrecharge areas, and (3) discharge areas (Andersonand others, 1994). Primary recharge areas, commonlythe uplands and coarse-grained unconsolidateddeposits along basin margins, do not contain thick,continuous, fine-grained layers and have a downwardground-water gradient. Secondary recharge areas,commonly mountain front benches, have fine-grainedlayers thicker than 20 feet (6 m) and downward ground-water gradients. Ground-water discharge areas aregenerally in basin lowlands. Discharge areas forunconfined aquifers are where the water tableintersects the ground surface, forming springs orseeps. Discharge areas for confined aquifers arewhere the ground-water gradient is upward and wateris discharging to a shallow unconfined aquifer abovethe upper confining bed, or to a spring. Water fromwells which penetrate confined aquifers may flow to thesurface naturally. The extent of both recharge anddischarge areas may vary seasonally and from dryyears to wet years.
Purpose and Scope
The purpose of this study is to help state andlocal government officials and local residents protectground-water quality in the Sevier Desert by definingrecharge areas where ground-water aquifers arevulnerable to contamination. The study is acooperative effort among the Utah Geological Survey(UGS), the Utah Division of Water Quality (DWQ), andthe U.S. Environmental Protection Agency (EPA).
2 Utah Geological Survey
Figure 1. Map of the southern Sevier Desert study area.
the Sevier Desert. We collected logs for water wells Sevier River in the western part of the Sevier Desert.drilled in the basin prior to August 1995 from the State The Sevier River in the western part of the study areaEngineer's office. We entered well-log information into is usually dry due to irrigation withdrawals anda database and plotted well locations on 1:24,000-scale evaporation, but in wet years it flows to Sevier Lake, abase maps. Generalized recharge- and discharge- playa west of the study area. Many small ephemeralarea boundaries were then drawn and digitized, along streams flow from the mountains into the Sevier Desertwith well locations, into the State Geographic during spring.Information Database.
Setting
The study area is thesouthern part of the SevierDesert in eastern MillardCounty, including PahvantValley and the northern BlackRock Desert (figure 1). Thestudy area includes about2,700 square miles (7,000km ) of the Sevier River2
drainage basin.
Physiography and Drainage
The Sevier Desert is inthe eastern part of the GreatBasin section of the Basinand Range physiographicprovince. The Pahvant andCanyon Ranges make up theeastern border. To thesouthwest and northwest arethe Cricket and Little DrumMountains, respectively. Hillsand volcanic rocks betweenthe Pahvant Range and theCricket Mountains form thesouthern divide. The studyarea ends at the Juab Countyline to the north. The mainsource of surface water is theSevier River which flows fromthe high plateaus to the eastinto the northeast corner ofthe study area throughLeamington Canyon. TheBeaver River enters the studyarea from the south, flowsthrough the Black RockDesert and, during highprecipitation years, joins the
Valley-fill aquifer map, Sevier Desert 3
Figure 2. Schematic block diagram showing direction of ground-water flow inthe Sevier Desert.
Climate
Annual precipitation on the semiarid basin flooris 8.11 inches (20.6 cm) in Delta, and 8.91 inches (22.6cm) at Clear Lake. Located at the base of the relativelyhumid eastern mountains, Fillmore and Oak Cityreceive an average 16.00 and 11.59 inches (40.6 cmand 29.4 cm) of annual precipitation, respectively(Ashcroft and others, 1992). The Canyon Mountainsand Pahvant Range, on the eastern side of the studyarea, receive over 30 inches (75 cm) of precipitationannually at the highest elevations (Ashcroft and others, The ground-water hydrology of the northern part1992). Temperatures in the Sevier Desert are of the study area has been studied by Mower and Feltisgenerally mild, rarely above 100(F (38(C) or dropping (1968) and Holmes (1984). Mower (1965) and Holmesbelow 0(F (-18(C), and averaging around 50(F (10(C) and Thiros (1990) examined the ground-waterover the year (Ashcroft and others, 1992). hydrology of Pahvant Valley. Other hydrologic studies
Land Use
Approximately 11,000 people live in the studyarea. Delta and Fillmore are the largest cities, having
2,998 and 1,956 people in 1990, respectively (UtahLeague of Cities and Towns, 1993). Few people live inthe Black Rock Desert area. Agriculture is the mainland use and source of income. The IntermountainPower Project began operating in 1986. This coal-burning electric plant, northeast of Delta, employs 600people. Economic deposits of sand and gravel, gold,lime, and salt are mined in the Sevier Desert.
Previous Studies
that involve parts of the Sevier Desert include: Meinzer(1911), Nelson (1952), Handy and others (1969),Bedinger and others (1984a,b), Thompson and Nuter(1984), and Gates (1987).
The bedrock andsurficial geology of theSevier Desert have beenmapped at various scales.In this study I used onlyregional-scale geologicmaps. Oviatt (1989, 1991)mapped the Quaternarygeology for the area west ofDelta and the Black RockDesert. Bedrock geologywas mapped by Steven andMorris (1983) and Morris(1987).
METHODS
The methods used inthis study for identifyingconfining layers, classifyingaquifers, and delineatingrecharge and dischargeareas are modified fromthose of Anderson andothers (1994). This study isconcerned with the principalaquifer system and localover ly ing shal lowunconfined aquifers (figure2). The principal aquifersystem is the most
4 Utah Geological Survey
Figure 3. Relative water levels in wells inrecharge and discharge areas.
important source of ground water, and may be confined and commonly inconsistent among various drillers.or unconfined. The principal aquifer system begins at The use of water-level data from well logs is alsothe mountain fronts surrounding the basin where problematic because levels in the shallow unconfinedcoarse-grained alluvial-fan sediments predominate and aquifer are often not recorded and because waterground water is generally unconfined. In the center of levels were measured during different seasons andthe basin, fine-grained silt and clay strata form years.confining layers above and within the principal aquifersystem. Water in sediments above the top confining Confining layers are any fine-grained (claylayer is in a shallow unconfined aquifer. This is and/or silt) layer thicker than 20 feet (6 m) (Andersongenerally a less important source of drinking water. and others, 1994). Sometimes a driller will note both
I used drillers’ logs of water wells to delineate giving relative percentages; these are not classified asprimary or secondary recharge areas and discharge confining layers (Anderson and others, 1994). If bothareas, based on the presence of confining layers and are checked and the word "sandy" is written in therelative water levels in the principal and shallow remarks column, then the layer is assumed to beunconfined aquifers. I compiled a database of well-log primarily a clay confining layer (Anderson and others,information (appendix). The use of drillers’ logs 1994). Sometimes a driller will mark both clay andrequires interpretation because of the variable quality gravel, cobbles, or boulders; these also are notof the logs. Correlation of geology from well logs is classified as confining layers, although, in some areasdifficult because lithologic descriptions are generalized in the Sevier Desert, layers of clay containing gravel,
clay and sand along the same interval on logs, without
cobbles, or boulders behave as confining layers.
The primary recharge area for the principalaquifer system is the uplands surrounding the basin,and basin fill not containing confining layers, generallyalong mountain fronts (figure 3). Ground-water flow inprimary recharge areas has a downward component.If present, secondary recharge areas are where thereare confining layers, but ground-water flow still has adownward component. Secondary recharge areasgenerally extend toward the center of the basin to thepoint where the ground-water-flow gradient is upward(figure 3). The ground-water-flow gradient, also calledthe hydraulic gradient, is upward when thepotentiometric surface of the principal aquifer system ishigher than the water table in the shallow unconfinedaquifer (Anderson and others, 1994). Water-level datafor the shallow unconfined aquifer are not common butcan be found on some well logs. When the confininglayer extends to the ground surface, secondaryrecharge areas are where the potentiometric surface inthe principal aquifer system is below the groundsurface.
Ground-water-discharge areas, if present, aregenerally at lower elevations than recharge areas. Indischarge areas, the water in confined aquifersdischarges to the land surface or to a shallowunconfined aquifer (figure 3). For this to happen, thehydraulic head in the principal aquifer system must behigher than the water table in the shallow unconfinedaquifer. Otherwise, downward pressure from the
Valley-fill aquifer map, Sevier Desert 5
Figure 4. Numbering system for wells in Utah (see text foradditional explanation).
shallow aquifer will exceed the upward pressure fromthe confined aquifer, creating a net downward gradientindicative of secondary recharge areas. Flowing(artesian) wells, indicative of discharge areas, aremarked on drillers’ logs and sometimes on U.S.Geological Survey 7.5' quadrangle maps. Wells withpotentiometric surfaces above the top of the confininglayer can be identified from well logs. Surface water,springs, or phreatophytic plants (wetlands) can beanother indicator of ground-water discharge. In someinstances, however, this discharge may be from ashallow unconfined aquifer. It is necessary tounderstand the topography, surficial geology, andground-water hydrology before using these wetlands toindicate discharge from the principal aquifer system.
I generally did not map small secondaryrecharge or discharge areas defined by local claylayers in only a few wells where surrounded completelyby primary recharge areas, because contaminantsentering the aquifer system above these clay layers oflocal extent still have a high potential to reach primaryrecharge areas.
The numbering system for wells in thisstudy is based on the Federal Governmentcadastral land-survey system that divides Utahinto four quadrants (A-D) separated by the SaltLake Base Line and Meridian (figure 4). Thestudy area is entirely within the southwesternquadrant (C). The wells are numbered with thisquadrant letter C, followed by township andrange enclosed in parentheses. The next set ofcharacters indicates the section, quarter section,quarter-quarter section, and quarter-quarter-quarter section designated by a through d,indicating the northeastern, northwestern,southwestern, and southeastern quadrants,respectively. A number after the hyphencorresponds to an individual well within aquarter-quarter-quarter section. For example,the well (C-17-6) 9adb-1 would be the first well inthe northwestern quarter of the southeasternquarter of the northeastern quarter of section 9,Township 17 South, Range 6 West(NW¼SE¼NE¼ section 9, T. 17 S, R. 6. W).
GEOLOGY
Bedrock
The Sevier Desert is a complexly faultedstructural basin typical of the Basin and Rangeprovince of Utah and Nevada. It is surrounded bymountain ranges and contains thick unconsolidatedand volcanic basin-fill deposits. Active faulting andvolcanism have occurred during the Quaternary Period.
Bedrock of the mountains surrounding theSevier Desert ranges in age from Precambrian toTertiary. The Cricket Mountains consist primarily ofCambrian limestone and quartzite (Steven and Morris,1983). The Pahvant Range includes this Cambrianlimestone and quartzite, some Devonian dolomite andquartzite, and Cretaceous and Tertiary sedimentaryrocks of the Price River, North Horn, Flagstaff, andGreen River Formations (Steven and Morris, 1983).The Canyon Mountains are the type locality for theCanyon Range Formation, a Cretaceous to Tertiaryconglomerate that crops out extensively in the northernpart of the range. Precambrian and Cambrian quartziteand limestone, and Devonian dolomite, are also foundin the Canyon Range (Morris, 1987). The Little DrumMountains generally consist of Tertiary ash-flow tuff,but contain some Precambrian to Cambrian quartzite,
6 Utah Geological Survey
limestone, and shale (Morris, 1987). Deltaic sediments were deposited where the
Of great importance to the Sevier Desertground-water system are recent Tertiary- andQuaternary-age volcanic rocks in the south andnorthwest (figure 1). Pahvant Valley is bordered to thewest by several large basalt flows and tuff cones. Alocal landmark, Pahvant Butte, formed as lava and tufferupted into Lake Bonneville approximately 15,500 yrB.P. (Oviatt, 1989). The associated ash and basaltflows cover much of the surface of the Sevier Desert.Tabernacle Hill, 5 miles (8 km) west of Meadow,erupted basalt into Lake Bonneville at the Provo levelin late Pleistocene time (14,500 to 14,000 yr B.P.)(Oviatt, 1991). Eruption of the Ice Springs basalt flowwest of Flowell is the most recent volcanic event in thearea, occurring about 660 yr B.P. (Valastro and others,1972). This basalt covers more than 20 square miles(50 km ) and consists of angular (aa) and ropy2
(pahoehoe) flows. Beaver Ridge and the Coyote Hillsin the far southern part of the Black Rock Desertconsist of Pleistocene and Pliocene andesite, rhyolite,and basalt (Oviatt, 1991). Other Pliocene andPleistocene volcanics are in the Smelter Knolls andLittle Drum Mountains in the northwestern corner of thestudy area (Oviatt 1989, 1991).
Unconsolidated Sediments
The basin fill of the Sevier Desert consists oflacustrine and deltaic sediments deposited duringseveral Pleistocene lake cycles, and interlacustrinefluvial and alluvial-fan deposits. Volcanic ash layerswithin lake deposits are continuous marker beds foundin much of the basin. The area stratigraphy providesan excellent record of the Quaternary history of lakesin the area. Eolian sand, mostly reworked deltaicdeposits, is found in the northwestern part of the studyarea (Oviatt, 1989).
Fine-grained lacustrine deposits of Pliocene toPleistocene age are widespread in the Sevier Desert(Oviatt, 1989). Deposits of the most recent lake, LakeBonneville, can be differentiated from those of pre-Bonneville lakes. The older lacustrine sediments arecalcareous clay, silt, and sand, and induratednearshore limestone deposited in a pre-Bonneville lakeor lakes (Oviatt, 1989). Fine- to coarse-graineddeposits associated with Lake Bonneville overlie theseolder sediments. Bonneville deposits include deep-water white marl, nearshore sand and gravel, andlagoonal silt, sand, and clay (Oviatt, 1989).
Sevier and Beaver Rivers flowed into Lake Bonneville.A large silt and fine sand regressive underflow fan-deltastretches from Leamington Canyon to Delta (Oviatt,1989). Coarse-grained fan-delta sand and gravel weredeposited by the Beaver and Sevier Rivers during theBonneville regression (Oviatt, 1989, 1991).
Alluvial-fan and fluvial sediments were depositedin the Sevier Desert during interlacustrine periods, andoverlie and interbed with lacustrine deposits. Most ofthe surface sediments in the study area are post-Bonneville sand, silt, and clay floodplain, channel, oroverbank deposits of the Sevier and Beaver Rivers(Oviatt, 1989, 1991). These deposits are largelyreworked lacustrine deposits, so their hydrologiccharacteristics and appearance are similar.
GROUND WATER
The majority of the wells in the Sevier Desert tapunconsolidated basin-fill aquifers. These aquifers canbe divided into two types: the shallow unconfinedaquifer, and the principal aquifer system. The latter canbe further divided into the upper and lower artesianaquifers in the northeastern part of the study area(figure 2). Some wells in Pahvant Valley tap afractured-volcanic-rock aquifer. Water enters theaquifers from the Sevier River east of Leamington,seepage from ephemeral mountain streams andirrigation, and infiltration of precipitation.
Ground-water quality in the Sevier Desert variesconsiderably due to concentration of salts byevaporation near the surface and arseniccontamination from volcanic rocks (Holmes, 1984).Drinking-water and ground-water protection regulationsin Utah classify ground water, based largely on total-dissolved-solids concentrations, as follows: class IA(pristine), less than 500 mg/L; class II (drinking waterquality), 500 to 3,000 mg/L; class III (limited use), 3,000to 10,000 mg/L; and class IV (saline), more than 10,000mg/L. Class IA and II waters are considered suitablefor drinking, provided concentrations of individualcontaminants do not exceed state and federal ground-water-quality standards. Water having total-dissolved-solids concentrations in the higher part of the class IIrange is generally suitable for drinking water only iftreated, but it can be used for some agricultural orindustrial purposes without treatment. Most groundwater in the Sevier Desert is class IA and II.
Valley-fill aquifer map, Sevier Desert 7
Fractured-Rock Aquifers
Fractured-rock aquifers in the Sevier Desertinclude sedimentary and metasedimentary rocks insurrounding mountains and underlying the basin fill,and Cenozoic volcanic rocks overlying and interbeddedwith the basin fill. Few wells are drilled into fractured-rock aquifers in the Sevier Desert, due to the thicknessand productivity of basin-fill aquifers. Several springsand wells in Pahvant Valley receive water fromfractured basalt, which is an important aquifer that bothrecharges and receives water from the principal aquifersystem. Springs discharge from bedrock in themountains surrounding the Sevier Desert. Little isknown about the quantity of water within or thecharacteristics of fractured-rock aquifers in themountains.
Aquifer Characteristics
Wells and springs in volcanic rocks can yieldlarge amounts of water. Clear Lake Springsdischarges about 9,900 gallons per minute (625 L/s)from the Pahvant Butte basalt (Holmes, 1984). Manyother productive springs are associated with volcanicrocks in the Sevier Desert. Pumped wells in fracturedbasalt near Flowell in Pahvant Valley yield over 3,000gallons per minute (200 L/s), and have transmissivitiesof 3,000,000 square feet per day (280,000 m /day)2
(Mower, 1965). These large values are likely fromwells tapping highly fractured volcanic rock. Hydrauliccharacteristics are unavailable for aquifers in thesedimentary and metamorphic rocks in the surroundingmountains.
Recharge and Discharge
The volcanic-rock aquifers have a directhydraulic connection to the basin-fill aquifers in manyparts of the Sevier Desert. Clear Lake Springsdischarges water that flows west from the PahvantValley unconsolidated basin-fill aquifer through thePahvant Butte basalt aquifer (Mower and Feltis, 1968).Some recharge also comes from direct precipitation onvolcanic rock. Discharge from fractured bedrockaquifers in the mountains surrounding the SevierDesert is probably an important source of recharge tothe basin-fill aquifer, but its relative contribution isunknown (Mower and Feltis, 1968).
Water Quality
Clear Lake Springs and well (C-18-8) 24ada-1
both discharge from volcanic rock in the northern BlackRock Desert. Enright and Holmes (1982) report totaldissolved solids of 1,970 and 2,030 mg/L, respectively.In Pahvant Valley, wells drawing water from basaltrange from 528 to 4,490 mg/L total dissolved solids(Mower, 1965). These values are higher than twosprings with total dissolved solids of 523 and 331 mg/Lthat discharge from sedimentary rocks in the CanyonMountains (Enright and Holmes, 1982). In general,volcanic-rock aquifers have more total dissolved solidsthan unconsolidated basin-fill or other fractured-rockaquifers (Holmes, 1984). Arsenic in water in somewells in or near volcanic rocks is believed to have beenleached from the rocks (Holmes, 1984).
Unconsolidated Basin-Fill Aquifers
The unconsolidated basin-fill aquifers are themost important sources of water in the Sevier Desert.
Aquifer Characteristics
The basin fill consists predominantly oflacustrine, deltaic, and alluvial deposits. In general, thecoarser material is in alluvial fans along the mountainfronts, and the finer material is in lacustrine deposits inthe central portions of the basin. Thick, fine-grainedconfining layers are present throughout much of theSevier Desert, and artesian conditions are widespread.
The northeastern part of the study area has twoaquifers that make up the principal unconsolidatedbasin-fill aquifer system, overlain locally by shallowunconfined aquifers (figure 2). The principal aquifersare predominantly sand and gravel, and the interveningand overlying confining layers are mostly silt and clay,although the boundaries between aquifers andconfining layers are commonly indistinct. The confininglayer that separates the upper artesian aquifer from thelower artesian aquifer near Lynndyl is 400 to 500 feet(120-150 m) thick (Mower and Feltis, 1968). The watertable in the shallow unconfined aquifer is about 50 feet(15 m) below the land surface (Holmes, 1984). Thebasin fill fines toward the center and western part of thestudy area where the aquifers contain more silt andclay. The confining layer between the aquifers thins to100 to 175 feet (30 to 55 m) at Sugarville, and may notbe present in the northwestern part of the study areawhere the upper and lower artesian aquifers arehydraulically connected (Mower and Feltis, 1968).
8 Utah Geological Survey
Transmissivity of the upper artesian aquifer much recharge to the basin-fill aquifers directly. Someranges from 47,000 square feet per day (4,400 m /day) water enters the aquifers at the mouth of Leamington2
near Lynndyl to 3,600 square feet per day (340 m /day) Canyon, but generally the Sevier River gains water2
west of Sugarville (Holmes, 1984). Transmissivities for from subsurface inflow and loses water to irrigationthe lower artesian aquifer range from 27,000 square (Holmes, 1984).feet per day (2,500 m /day) near Lynndyl to 2,0002
square feet per day (190 m /day) south of Delta Infiltration of water from reservoirs, unconsumed2
(Holmes, 1984). These values are consistent with the irrigation, and canal leakage provides recharge to theobservation that the aquifers fine toward the center of shallow unconfined aquifer in the center of the basin,the basin. where thick confining layers and upward ground-water
In Pahvant Valley, there is one principal aquifer, system. These sources, including the Central Utahcomposed primarily of alluvial-fan sand and gravel. Canal, provide significant local recharge to the principalLake Bonneville did not reach the base of the Pahvant aquifer system along its eastern margin fromRange, and the basin fill above the Provo shoreline Leamington to Kanosh (Mower, 1965; Holmes, 1984).(4,830 feet [1,470 m]) is coarse and the principal basin- This is a wide primary recharge area, created byfill aquifer is unconfined. In the confined system, near coarse proximal delta sediments and alluvial fans (plateFlowell, the principal basin-fill aquifer is 140 to 200 feet 1). Some of this area, especially east of Fillmore, is(40-60 m) deep, with 15 to 75 feet (5-23 m) of clay above the Lake Bonneville highstand, so fine-grainedoverlying it (Holmes and Thiros, 1990). West of Flowell lacustrine deposits are not present.and Kanosh, coarse deposits thin and lacustrine claysrestrict vertical ground-water flow, causing the Direct precipitation on the basin floor is anpotentiometric surface of the confined principal aquifer insignificant source of recharge in most of the basinsystem to be greater than 50 feet (15 m) above the land (Mower, 1965; Holmes, 1984). Approximately 5surface (Mower, 1965; Holmes and Thiros, 1990). percent of the precipitation that falls on the coarse-Pump tests on wells in the basin-fill aquifer in Pahvant grained alluvial fans above 4,800 feet (1,440 m) inValley yielded a range of transmissivities from 2,000 to Pahvant Valley recharges the principal aquifer (Holmes40,000 square feet per day (200-4,000 m /day) (Mower, and Thiros, 1990). Subsurface inflow from the volcanic2
1965). The low values in this range indicate sand and rocks within the basin and sedimentary rocks in thegravel aquifers having a high percentage of fines. surrounding mountain ranges is a source of recharge,
Recharge and Discharge
Ground water in the Sevier Desert generallymoves with the Sevier and Beaver Rivers to the westtoward Sevier Lake. Water enters the system asephemeral stream runoff from the mountains (includingthose north of the study area), infiltration from riversand irrigation, direct precipitation on the valley floor,and subsurface inflow from bedrock. Water leavesthrough evapotranspiration, discharge to rivers, andsubsurface outflow to Sevier Lake (Holmes, 1984;Holmes and Thiros, 1990).
The main source of recharge to the principalaquifer system is seepage from intermittent streamsfrom the surrounding mountains during springsnowmelt (Mower, 1965; Holmes, 1984). Most of thesmall mountain streams lose their surface flow whenthey cross onto coarse-grained alluvial-fan deposits atthe basin margins. Ephemeral streams also flow frommountains north of the study area and recharge thebasin-fill aquifers. The Sevier River does not provide
gradients impede recharge to the principal aquifer
but its relative contribution is unknown.
Ground water discharges through evapo-transpiration, springs and seepage to rivers,subsurface outflow, and wells. Evapotranspiration byphreatophytes varies with depth to ground water,salinity, and vegetation, but is a large part of the annualdischarge. Seepage to the Sevier River is also asource of discharge. Water re-enters the river assubsurface inflow near Leamington and in the centralpart of the basin where the water table is shallow(Holmes, 1984). Water exits the study area along thewestern edge through subsurface outflow. Dischargeto wells varies greatly, depending on the amount ofavailable surface water in a given year, which causesgreat fluctuations in water levels as discussed below.
The low-elevation parts of the Sevier Desertaround Delta and Pahvant Valley are discharge areasor secondary recharge areas (plate 1). The generallyfine-grained sediments confine the aquifers, and manywells in the area flow or have historically flowed to thesurface.
Valley-fill aquifer map, Sevier Desert 9
Water-Level Changes
The Sevier Desert has had some declines inwater levels since pumping for irrigation began in the1940s. A long period of below-average precipitationfrom about 1948 to 1966 caused many wells to stopflowing and reduced water levels in wells as much as50 feet (15 m) (Batty and others, 1993). Heavypumping for irrigation during dry years has also causedsome changes in ground-water flow direction inPahvant Valley near Kanosh and Flowell (Holmes andThiros, 1990). Studies done by the U.S. GeologicalSurvey in the 1960s for the Sevier Desert near Delta(Mower and Feltis, 1968) and Pahvant Valley (Mower,1965) documented areas where wells had ceased toflow. I classified these areas as secondary rechargeareas for this study because of the current downwardhydraulic gradient (plate 1). Gates (1987) reportsspeculation in the 1960s that mining of ground water inthe Sevier Desert had begun, and these observeddeclines would be permanent. However, several yearsof above-average and record precipitation in the earlyto mid-1980s raised water levels in most aquifers to Holmes (1984) documents a long-term declinetheir 1940s and 1950s levels (Batty and others, 1993). in water quality in the Sevier Desert. He attributes thisTwo interrelated factors are responsible for this to poor-quality water from the Sevier River, irrigation,recovery (Gates, 1987). First, increased precipitation canals, and reservoirs recharging the system. Theprovided more water to recharge the principal aquifer nitrate contamination in Oak City may be an earlysystem. Second, increased surface-water flow reduced warning of the problems associated with agriculture orthe need to pump ground-water reservoirs for irrigation, rural waste-water disposal in primary recharge areas.allowing water levels to stabilize and rise. Average The principal aquifer system in the populated andannual ground-water withdrawals in the study area cultivated part of the Sevier Desert, particularly aroundfrom 1980 to 1986 were one-third to two-thirds of Delta, is protected from downward leakage ofaverage withdrawals from 1973 to 1979 (Gates, 1987). contaminants by confining layers. However, theFrom 1988 to 1993 precipitation in the area was below contaminants entering the system in the primaryaverage, and in many areas water levels have begun recharge area along the eastern margin of the basinto decline again, and these fluctuations will likely may eventually reach the principal aquifer systemcontinue (Holmes and Thiros, 1990; Batty and others, beneath Delta.1993).
Water Quality
Water quality in the Sevier Desert varies withlocation and depth. Total dissolved solids range from200 to 20,000 mg/L (Mower, 1965; Holmes, 1984). Thehigh values are from the shallow unconfined aquifer atthe western edge of the study area near Sevier Lake.Salts are concentrated by evaporation near thesurface. In general, the worst quality water is in theshallow unconfined aquifer, which is partially rechargedby returned irrigation water (Mower, 1965; Holmes,1984). The best ground water in the study area is inthe lower artesian aquifer between Lynndyl and Delta(Holmes, 1984).
An area of lower quality ground water in PahvantValley was documented by Holmes and Thiros (1990).Wells in the farming area 5 miles (8 km) west ofKanosh have had increases in the concentration ofsodium, chloride, and sulfate, causing an increase intotal dissolved solids from 2,000 mg/L in the 1950s toover 6,000 mg/L at present. This decline in waterquality has been attributed to two factors: (1) rechargeby poor-quality water to the southwest and west duringyears of large withdrawals, and (2) concentration ofsolids in irrigation water through evaporation (Holmesand Thiros, 1990).
Nitrate concentrations are relatively high,ranging from 4 to 22 mg/L, in the Oak City area(Holmes, 1984). This is a primary recharge area, andit may be that septic-tank effluent and irrigation waterare contributing to recharge of the principal aquifersystem (Holmes, 1984).
Potential for Water-Quality Degradation
Another related reason for the decline in waterquality may be the very tight recharge and dischargebudget. During dry years, water levels in wells drop,indicating a lack of recharge. The poor-quality waternear Kanosh is the result of large withdrawals reversingground-water flow, causing recharge from areas oflower quality water. Pumped poor-quality water is usedto irrigate fields, where much of it re-enters the system,after concentration of dissolved solids by evaporationat the surface. The increased flow of the Sevier Riverduring wet years can be used for irrigation, allowing thewells to rebound, and bringing new, higher qualitywater into the system. In a long-term drought,however, this cycle may be broken and water qualitymay decline more rapidly.
10 Utah Geological Survey
SUMMARY AND CONCLUSIONS
The principal aquifer system of the Sevier Desertis made up of unconsolidated basin-fill sediments oflacustrine, deltaic, and alluvial origin. Fine-grainedlayers form confining beds that separate the principalaquifer system near Delta into lower and upper artesianaquifers, and separate them from shallow unconfinedaquifers. Fractured volcanic rocks are an importantaquifer in the western Pahvant Valley. Little is knownabout fractured-bedrock aquifers in the sur-roundingmountains and underlying basin fill.
Primary recharge areas for the principal aquifersystem are generally along the mountain front on theeast side of the study area. Secondary recharge areasand discharge areas are on the basin floor. Waterenters the system from the north, east, and south andexits toward Sevier Lake to the west. Water levels inwells decline during dry periods, but rebound in yearsof above-average precipitation. Water quality is best inthe lower artesian aquifer, and worst in the shallowunconfined aquifer near Sevier Lake and the principalaquifer near Kanosh. Increased salinity and nitratecontamination in the Sevier Desert are probably due toconcentration of salts by evaporation, recycling ofirrigation water, and recharge by poor-quality water.
ACKNOWLEDGMENTS
This study was supported by a grant from theU.S. Environmental Protection Agency, administered bythe Utah Division of Water Quality. Thanks to the UtahDivision of Water Rights for providing well logs and theUtah Automated Geographic Reference Center forallowing Janine Jarva to use their digital compilationfacilities.
REFERENCES
Anderson, P.B., Susong, D.D., Wold, S.R., Heilweil,V.M., and Baskin, R.L., 1994, Hydrogeology ofrecharge areas and water quality of the principalaquifers along the Wasatch Front and adjacentareas, Utah: U.S. Geological Survey Water-Resources Investigations Report 93-4221, 74 p.,scale 1:100,000.
Ashcroft, G.L., Jensen, D.T., and Brown, J.L., 1992,Utah climate: Logan, Utah, Utah Climate Center,Utah State University, 127 p.
Batty, D.M., Allen, D.V., and others, 1993, Ground-
water conditions in Utah, spring of 1993: UtahDivision of Water Resources and Division ofWater Rights Cooperative Investigations ReportNumber 33, 106 p.
Bedinger, M.S., Gates, J.S., and Stark, J.R., 1984a,Maps showing ground-water units andwithdrawal, Basin and Range province, Utah:U.S. Geological Survey Water ResourcesInvestigations Report 83-4122-A, 13 p., scale1:500,000.
Bedinger, M.S., Mason, J.L., Langer, W.H., Gates, J.S.,Stark, J.R., and Mulvihill, D.A., 1984b, Mapsshowing ground-water levels, springs, anddepth to ground water, Basin and Rangeprovince, Utah: U.S. Geological Survey WaterResources Investigations Report 83-4122-B, 12p., scale 1:500,000.
Enright, Michael, and Holmes, W.F., 1982, Selectedground-water data, Sevier Desert, Utah, 1935-82: Utah Division of Water Rights UtahHydrologic-Data Report Number 37, 59 p.
Gates, J.S., 1987, Ground water in the Great Basinpart of the Basin and Range Province, westernUtah, in Kopp, R.S., and Cohenour, R.E.,editors, Cenozoic geology of western Utah: UtahGeological Association Publication 16, p. 75-89.
Handy, A.H., Mower, R.W., and Sandberg, G.W., 1969,Changes in chemical quality of ground water inthree areas in the Great Basin, Utah, inGeological Survey Research, 1969: U.S.Geological Survey Professional Paper 650-D, p.D228-D234.
Holmes, W.F., 1984, Ground-water and projectedeffects of ground-water withdrawals in theSevier Desert, Utah: Utah Division of WaterRights Technical Publication No. 79, 54 p., scale1:250,000.
Holmes, W.F., and Thiros, S.A., 1990, Ground-waterhydrology of Pahvant Valley and adjacent areas,Utah: Utah Division of Water Rights TechnicalPublication No. 98, 64 p., scale 1:250,000.
Meinzer, O.E., 1911, Ground water in Juab, Millard,and Iron Counties, Utah: U.S. Geological SurveyWater-Supply Paper 277, 162 p.
Morris, H.T., 1987, Preliminary geologic map of theDelta 2( quadrangle, Tooele, Juab, Millard, andUtah Counties, Utah: U.S. Geological SurveyOpen-File Report 87-185, 18 p., scale 1:250,000
Mower, R.W., 1965, Ground-water resources of PavantValley, Utah: U.S. Geological Survey Water-Supply Paper 1794, 78 p., scale 1:62,500.
Mower, R.W., and Feltis, R.D., 1968, Ground-waterhydrology of the Sevier Desert, Utah: U.S.Geological Survey Water-Supply Paper 1854,
Valley-fill aquifer map, Sevier Desert 11
75 p., scale 1:250,000. Steven, T.A., and Morris, H.T., 1983, Geology of theNelson, W.B., 1952, Sevier Desert, Millard County, in Richfield quadrangle, west-central Utah: U.S.
Thomas, H.E., Nelson, W.B., Lofgren, B.E., and Geological Survey Open-File Report 83-583, 22Butler, R.G., Status of development of selected p., scale 1:250,000.ground-water basins in Utah: Utah State Thompson, T.H., and Nuter, Janet, 1984, MapsEngineer Technical Publication 7, p. 63-66. showing distribution of dissolved solids and
Oviatt, C.G., 1989, Quaternary geology of part of the dominant chemical type in ground water, BasinSevier Desert, Millard County, Utah: Utah and Range province, Utah: U.S. GeologicalGeological and Mineral Survey Special Study Survey Water Resources Investigations Report70, 41 p., scale 1:100,000. 83-4122-C, 7 p., scale 1:500,000.
------1991, Quaternary geology of the Black Rock Utah League of Cities and Towns, 1993, Directory ofDesert, Millard County, Utah: Utah Geological local government officials: Salt Lake City, Utahand Mineral Survey Special Study 73, 23 p., League of Cities and Towns, 184 p.scale 1:100,000. Valastro, S., Jr., Davis, E.M., and Varela, A.G., 1972,
University of Texas at Austin radiocarbon datesIX: Radiocarbon, v. 14, p. 461-485.
APPENDIX
Records of Wells, Sevier Desert,Millard County, Utah
Site number: See plate 1 for well location. Wells not used to define recharge and discharge areas are not plotted.Local well number: See text for explanation of numbering system.Elevation: In feet above sea level.Well depth: In feet below land surface.Recharge area: Y, primary recharge area; 1, secondary recharge area; N, discharge area; 2, well completed in
shallow unconfined aquifer.Water level: In feet below land surface, or feet above land surface for "+" values; +F, flowing well.Top of confining layer: Depth to first confining layer, in feet below land surface.Bottom of confining layer: Depth to bottom of first confining layer, in feet below land surface.Depth to bedrock: In feet below land surface; N, bedrock not encountered.Top of perforations: Depth to top of perforations, in feet below land surface.Bottom of perforations: Depth to bottom of all perforations, in feet below land surface; MI, multiple perforated intervals,
below bottom of uppermost perforated interval.
--, no data
![Digital Map Archive and Map Database of Eötvös Loránd ...e-Perimetron, Vol. 9, No. 4, 2014 [166-175] | ISSN 1790-3769 [166] Krisztina Irás*, István Elek** Digital Map Archive](https://img.pdfslide.us/doc/110x75/5e5a08daa024cb5c9511ebb6/digital-map-archive-and-map-database-of-etvs-lornd-e-perimetron-vol.jpg)
