Prepared in cooperation with the Navajo Nation and Peabody Western Coal Company
Groundwater, Surface-Water, and Water-Chemistry Data,
Black Mesa Area, Northeastern Arizona—2019–2021
Open-File Report 2024–1019
U.S. Department of the Interior
U.S. Geological Survey
Cover. Aerial photograph showing a northwest view at Triassic and Jurassic age rocks on the
southwest side of the Chuska Mountains, 30 miles east of Black Mesa. Prominent red cliff forming
unit is the Jurassic Wingate Sandstone. When present, the Wingate Sandstone is considered a
hydrologic unit of the N aquifer. It is unclear if it is present under Black Mesa. If it is present, it would
likely be buried under more than 2,000 feet of overlying rock units, making it difficult to identify. U.S.
Geological Survey photograph, August 2017.
Groundwater, Surface-Water, and Water-Chemistry Data,
Black Mesa Area, Northeastern Arizona—2019–2021
By Jon P. Mason
Prepared in cooperation with the Navajo Nation and Peabody Western
Coal Company
Open-File Report 2024–1019
U.S. Department of the Interior
U.S. Geological Survey
U.S. Geological Survey, Reston, Virginia: 2024
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Suggested citation:
Mason, J.P., 2024, Groundwater, surface-water, and water-chemistry data, Black Mesa area, northeastern
Arizona—2019–2021: U.S. Geological Survey Open-File Report 2024–1019, 47 p., https://doi.org/ 10.3133/
ofr20241019.
ISSN 2331-1258 (online)
iii
Contents
Abstract ...........................................................................................................................................................1
Introduction.....................................................................................................................................................1
Purpose and Scope ..............................................................................................................................4
Previous Investigations........................................................................................................................4
Description of Study Area ............................................................................................................................8
Physiography .........................................................................................................................................8
Climate ....................................................................................................................................................8
Geology .................................................................................................................................................10
Geologic Units Below the N Aquifer .......................................................................................10
Geologic Units of the N Aquifer ...............................................................................................10
Moenave Formation .........................................................................................................10
Wingate Sandstone ..........................................................................................................10
Kayenta Formation ............................................................................................................11
Navajo Sandstone ............................................................................................................11
Carmel Formation ..............................................................................................................12
Geologic Units of the D Aquifer ...............................................................................................12
Entrada Sandstone ...........................................................................................................12
Morrison Formation ..........................................................................................................12
Dakota Sandstone ............................................................................................................13
Mancos Shale ...................................................................................................................13
Geologic Units of the T Aquifer ...............................................................................................13
Mesaverde Group .............................................................................................................13
Bidahochi Formation ........................................................................................................13
Hydrologic Data............................................................................................................................................13
Withdrawals from the N Aquifer ......................................................................................................14
Withdrawals in Calendar Years 2020 and 2021 Compared to Previous Years ..................14
Groundwater Levels in the N Aquifer ..............................................................................................19
Spring Discharge from the N Aquifer ..............................................................................................29
Surface-Water Discharge, Calendar Years 2020–2021 .................................................................32
Moenkopi Wash .........................................................................................................................34
Dinnebito Wash ..........................................................................................................................34
Polacca Wash ............................................................................................................................34
Pasture Canyon Spring .............................................................................................................34
Surface-Water Base Flow ........................................................................................................35
Water Chemistry .................................................................................................................................36
Water-Chemistry Data for Springs that Discharge from the N Aquifer ............................36
Summary........................................................................................................................................................42
References Cited..........................................................................................................................................42
iv
Figures
1. Map showing location of the Black Mesa study area, northeastern Arizona ....................2
2. Stratigraphic section showing rock formations and hydrogeologic units of the
Black Mesa area, northeastern Arizona ...................................................................................3
3. Aerial photograph showing the Organ Rock Monocline and folding strata of
Skeleton Mesa near Kayenta, Arizona ......................................................................................8
4. Map showing mean annual precipitation, Black Mesa area, Ariz., 1981–2010 ..................9
5. Aerial photograph showing the Moenave Formation outcropping on Garces
Mesas, northeastern Arizona ...................................................................................................11
6. Plot of annual withdrawals from the N aquifer, Black Mesa area, northeastern
Arizona, 1965–2021 .....................................................................................................................17
7. Map showing well systems monitored for annual withdrawals from the N
aquifer, Black Mesa area, northeastern Arizona ..................................................................18
8. Map showing water-level changes in wells completed in the N aquifer, Black
Mesa area, northeastern Arizona, from the prestress period prior to 1965 to 2021 ........21
9. Plots of observed water levels in annual observation wells in unconfined areas
of the N aquifer, Black Mesa area, northeastern Arizona, 1950–2021 ...............................24
10. Plots of observed water levels in annual observation wells in confined areas of
the N aquifer, Black Mesa area, northeastern Arizona, 1953–2021 ...................................26
11. Plots of observed groundwater levels in continuous-record observation wells
BM1–BM6 in the N aquifer, Black Mesa area, northeastern Arizona, 1963–2021 ...........28
12. Map of surface-water and water-chemistry data-collection sites in the N
aquifer, Black Mesa area, northeastern Arizona, 2019–2021 ..............................................29
13. Plots of discharge from Moenkopi School Spring; Burro Spring; Pasture
Canyon Spring; and Unnamed Spring near Dennehotso, N Aquifer, Black Mesa
area, northeastern Arizona, 1987–2021 ...................................................................................30
14. Plots of daily mean discharge for Moenkopi Wash at Moenkopi, Ariz.; Dinnebito
Wash near Sand Springs, Ariz.; Polacca Wash near Second Mesa, Ariz.; and
Pasture Canyon Springs near Tuba City, Ariz., Black Mesa area, northeastern
Arizona, calendar years 2020–2021 .........................................................................................33
15. Plots of median winter discharge for November through February for
streamflow gages Moenkopi Wash at Moenkopi, Ariz.; Dinnebito Wash near
Sand Springs, Ariz.; Polacca Wash near Second Mesa, Ariz.; and Pasture
Canyon Springs near Tuba City, Ariz., Black Mesa area, northeastern Arizona,
winter 1977–2020 .........................................................................................................................35
16. Map showing water chemistry and distribution of dissolved solids at springs in
the N aquifer, Black Mesa area, northeastern Arizona, 2020–2021 ...................................37
17. Plots of concentrations of dissolved solids, chloride, and sulfate for water
samples from Moenkopi School Spring, Burro Spring, Pasture Canyon Spring,
and Unnamed Spring near Dennehotso, which discharge from the N aquifer,
Black Mesa area, northeastern Arizona, 1982–2021 ............................................................41
v
Tables
1. Withdrawals from the N aquifer, Black Mesa area, northeastern Arizona,
1965–2021 .......................................................................................................................................5
2. Tabulated list of progress reports for the Black Mesa monitoring program,
1978–2022 .......................................................................................................................................6
3. Identification numbers and names of monitoring program study wells used for
water-level measurements, 2020–21, Black Mesa area, northeastern Arizona ..............15
4. Withdrawals from the N aquifer by well system, Black Mesa area, northeastern
Arizona, calendar years 2020 and 2021 ...................................................................................16
5. Total, industrial, and municipal withdrawals from the N aquifer for discrete time
periods from 1965 to 2021, Black Mesa area, northeastern Arizona .................................17
6. Water-level changes in monitoring program wells completed in the N aquifer,
Black Mesa area, northeastern Arizona, from the prestress period (prior to
1965) to calendar year 2021 .......................................................................................................20
7. Well-construction characteristics, depth to top of N aquifer, and 2021
static water level for wells used in annual water-level measurements and
for continuous-record observation wells, 2019–2021, Black Mesa area,
northeastern Arizona .................................................................................................................22
8. Median changes in water levels in monitoring-program wells from the
prestress period (prior to 1965) to 2021, N aquifer, Black Mesa area,
northeastern Arizona .................................................................................................................23
9. Discharge from Moenkopi School Spring, N aquifer, Black Mesa area,
northeastern Arizona, 1989–2021 .............................................................................................31
10. Discharge from Burro Spring, N aquifer, Black Mesa area, northeastern
Arizona, 1989–2021 .....................................................................................................................31
11. Discharge from Pasture Canyon Spring, N aquifer, Black Mesa area,
northeastern Arizona, 1988–2021 .............................................................................................32
12. Discharge from Unnamed Spring near Dennehotso, N aquifer, Black Mesa
area, northeastern Arizona, 1954–2021 ...................................................................................32
13. Streamflow-gaging stations used in the Black Mesa monitoring program, their
periods of record, and drainage areas ...................................................................................34
14. Chemical analyses of a field blank water sample processed at Pasture Canyon
Spring, Black Mesa area, northeastern Arizona, 2020 .........................................................36
15. Physical properties and chemical analyses of water samples from four springs
in the Black Mesa area, northeastern Arizona, 2020–2021 .................................................38
16. Specific conductance and concentrations of selected chemical constituents
in N-aquifer water samples from four springs in the Black Mesa area,
northeastern Arizona, 1948–2021 .............................................................................................39
vi
Conversion Factors
U.S. customary units to International System of Units
Multiply By To obtain
Length
foot (ft) 0.3048 meter (m)
mile (mi) 1.609 kilometer (km)
Area
square mile (mi
2
) 259.0 hectare (ha)
square mile (mi
2
) 2.590 square kilometer (km
2
)
Volume
acre-foot (acre-ft) 1,233 cubic meter (m
3
)
acre-foot (acre-ft) 0.001233 cubic hectometer (hm
3
)
Flow rate
acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m
3
/yr)
acre-foot per year (acre-ft/yr) 0.001233 cubic hectometer per year (hm
3
/yr)
cubic foot per second (ft
3
/s) 0.02832 cubic meter per second (m
3
/s)
gallon per minute (gal/min) 0.06309 liter per second (L/s)
International System of Units to U.S. customary units
Multiply By To obtain
Length
meter (m) 3.281 foot (ft)
kilometer (km) 0.6214 mile (mi)
meter (m) 1.094 yard (yd)
Area
hectare (ha) 0.003861 square mile (mi
2
)
square kilometer (km
2
) 0.3861 square mile (mi
2
)
Volume
cubic meter (m
3
) 0.0008107 acre-foot (acre-ft)
cubic hectometer (hm
3
) 810.7 acre-foot (acre-ft)
Flow rate
cubic meter per year (m
3
/yr) 0.000811 acre-foot per year (acre-ft/yr)
cubic hectometer per year (hm
3
/yr) 811.03 acre-foot per year (acre-ft/yr)
cubic meter per second (m
3
/s) 35.31 cubic foot per second (ft
3
/s)
liter per second (L/s) 15.85 gallon per minute (gal/min)
Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as °F = (1.8 × °C) + 32.
Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: °C = (°F – 32) / 1.8.
vii
Datum
Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929
(NGVD 29).
Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).
Supplemental Information
Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (µS/cm
at 25 °C).
Concentrations of chemical constituents in water are given in either milligrams per liter (mg/L)
or micrograms per liter (µg/L).
Abbreviations
BIA Bureau of Indian Affairs
C aquifer Coconino aquifer
D aquifer Dakota aquifer
EPA U.S. Environmental Protection Agency
MCL Maximum Contaminate Level
N aquifer Navajo aquifer
NTUA Navajo Tribal Utility Authority
NWIS National Water Information System
NWQL National Water Quality Laboratory
PWCC Peabody Western Coal Company
QC quality control
SMCL secondary maximum contaminate level
T aquifer Toreva aquifer
USGS U.S. Geological Survey
Groundwater, Surface-Water, and Water-Chemistry Data,
Black Mesa Area, Northeastern Arizona—2019–2021
By Jon P. Mason
Abstract
The Navajo (N) aquifer is an extensive aquifer and the
primary source of groundwater in the 5,400-square-mile Black
Mesa area in northeastern Arizona. Water availability is an
important issue in the Black Mesa area because of the arid climate,
past industrial water use, and continued water requirements for
municipal use by a growing population. Precipitation in the area
typically ranges from less than 6 to more than 16 inches per year,
depending on location.
The U.S. Geological Survey water-monitoring program in
the Black Mesa area began in 1971 and provides information
about the long-term effects of groundwater withdrawals from the
N aquifer for industrial and municipal uses. This report presents
the results of data collected as part of the monitoring program
in the Black Mesa area from calendar years 2020–2021 and,
additionally, uses streamow statistics from November and
December 2019. The monitoring program includes measurements
of (1) groundwater withdrawals (pumping), (2) groundwater
levels, (3) spring discharge, (4) surface-water discharge, and (5)
groundwater chemistry.
In calendar year 2020, total groundwater withdrawals
were estimated to be 2,680 acre-feet (acre-ft), and, in 2021, total
withdrawals were estimated to be 2,570 acre-ft. Total withdrawals
during 2021 were about 65 percent less than total withdrawals in
2005 because the Peabody Western Coal Company discontinued
its use of water to transport coal in a coal slurry pipeline after 2005
and ceased mining operations in 2019.
Owing to Navajo Nation and Hopi Reservation access
restrictions during the Coronavirus pandemic, water levels were
not collected from municipal wells in 2020 or 2021. Water levels
measured in 2021 from wells completed in the unconned areas
of the N aquifer within the Black Mesa area showed a decline in
7 of 13 wells when compared with water levels from the prestress
period (prior to 1965). The changes in water levels across all 13
wells ranged from +8.4 feet (ft) to −42.4 ft, and the median change
was −0.4 ft. Water levels also showed decline in 11 of 12 wells
measured in the conned area of the aquifer when compared to
the prestress period. The median change for the conned area of
the aquifer was −25.9 ft, with changes across all 12 wells ranging
from +17.3 ft to −133.7 ft.
Spring ow was measured at four springs between 2020 and
2021. Flow uctuated during the period of record for Burro Spring
and Pasture Canyon Spring, but a decreasing trend was statistically
signicant (p<0.05) at Moenkopi School Spring and Unnamed
Spring near Dennehotso, Arizona. Discharge at Burro Spring has
remained relatively constant since it was rst measured in the
1980s, and discharge at Pasture Canyon Spring has uctuated for
the period of record.
Continuous records of surface-water discharge in the
Black Mesa area were collected from streamow-gaging
stations at the following sites: Moenkopi Wash at Moenkopi
09401260 (1976–2021), Dinnebito Wash near Sand Springs
09401110 (1993–2020), Polacca Wash near Second Mesa
09400568 (1994–2020), and Pasture Canyon Springs 09401265
(2004–2021). Median winter ows (November through February)
of each winter were used as an estimate of the amount of
groundwater discharge at the above-named sites. For the period
of record, the median winter ows have generally remained
constant at Polacca Wash and Pasture Canyon Springs, whereas
a decreasing trend was observed at Moenkopi Wash and
Dinnebito Wash.
In 2020 and 2021, water samples were collected from a
total of four springs in the Black Mesa area and analyzed for
selected chemical constituents. Results from the four springs
were compared with previous analyses from the same springs.
Dissolved solids, chloride, and sulfate concentrations increased
at Moenkopi School Spring during the more than 30 years of
record at that site. Concentrations of dissolved solids and sulfate
at Pasture Canyon Spring have not varied signicantly (p>0.05)
since the early 1980s, and there is no increasing or decreasing
trend in those data. However, concentrations of chloride from
Pasture Canyon Spring show a diminishing trend. Concentrations
of dissolved solids, chloride, and sulfate at Unnamed Spring near
Dennehotso have varied for the period of record, but there is no
statistical trend in the data. Concentrations of dissolved solids at
Burro Spring have varied for the period of record, but there is no
statistical trend in the data. However, concentrations of chloride
and sulfate from Burro Spring show a trend towards lower
concentrations.
Introduction
The 5,400-square-mile (mi
2
) Black Mesa study area is
enclosed fully within the Navajo Nation and partially within the
Hopi Reservation in northeastern Arizona (g. 1). It contains
diverse topography that includes at plains, elevated mesas,
and incised drainages (g. 1). Black Mesa, a topographic high
at the center of the study area, encompasses about 2,000 mi
2
.
2 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
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Keams Canyon
Wash
Comb Ridge
Long House Valley
Organ Rock Monocline
Skeleton Mesa
Shonto
Plateau
Kaibito Plateau
Moenkopi
Plateau
Hopi Buttes
Chinle Valley
First Mesa
Second Mesa
Third Mesa
Coal Mine
Canyon
Blue Canyon
Ward Terrace
Balakai Mesa
Garces Mesas
NAVAJO COUNTY
APACHE COUNTY
COCONINO COUNTY
NAVAJO COUNTY
98
160
89
264
77
87
191
191
163
264
Dennehotso
Tsegi
Betatakin
Shonto
Shonto Junction
Red Lake
Rare Metals
Moenkopi
Chilchinbito
Kitsillie
Chapter
House
Forest Lake
Rocky Ridge
Hard Rock
Pinon
Low
Mountain
Bacavi
Hotevilla
Kykotsmovi
Shipaulovi
Mishongnovi
Shungopavi
Second Mesa
Polacca
Keams
Canyon
Rough Rock
Cameron
Page
Tuba City
Ganado
Chinle
Kayenta
COAL-LEASE
AREA
W
a
s
h
Boundary of Black Mesa
Area of Hopi Tribal Lands within
Navajo Nation
Boundary of study area—Based
on the mathematical boundary of
groundwater model from Brown
and Eychaner (1988)
EXPLANATION
!
!
!
!
Yuma
Tucson
Phoenix
Flagstaff
G
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Navajo Nation
Hopi
Tribal
Lands
Black Mesa
Map area
ARIZONA
109°30'110°00’110°30'111°00’111°30'
36°30'
36°00’
35°30'
37°00’
Base from U.S. Geological Survey digital data, 2010
Lambert Conformal Conic projection
Standard parallels 29°30’ N. and 45°30’ N.,
central meridian 111°30’ W.
Modified from Brown and Eychaner, 1988
25 MILES
25 KILOMETERS0
0 5 10 15 20
5 10 15 20
Figure 1. Map showing location of the Black Mesa study area, northeastern Arizona. Boundary of study area is based on boundary of groundwater model from Brown and
Eychaner (1988).
Introduction 3
It has cliffs that reach 2,000 feet (ft) in height on its north and
northeast sides, and it slopes gradually down to the south and
southwest. Availability of water is an important issue in the study
area because of continued groundwater withdrawals, the growing
population, and an arid to semiarid climate.
Aquifers that are used in the Black Mesa area include the
Toreva (T), Dakota (D), and Navajo (N) aquifers (g. 2). Shallow
aquifers composed of surcial sediments or volcanic rock are
also used locally to supply small quantities of water. Water from
the T and D aquifers is not used in signicant quantities in the
Black Mesa area. Water from the T aquifer is used locally for
livestock watering and to irrigate small plots of land, but it likely
cannot produce enough water for municipal or industrial use.
Water from the D aquifer is used locally for livestock watering
and has contributed to some wells at the Peabody Western Coal
Company (PWCC) industrial well eld, but water from this
aquifer has elevated dissolved solids concentrations that make it
unsuitable for municipal use. The deeper Coconino (C) aquifer
is present throughout the Black Mesa area, but it is deeply buried
and likely has dissolved solids concentrations above what can be
Bidahochi
Formation
Volcanic rock
►
Volcanic rock
►
Mesa
Verde
Group
Mancos Shale
Dakota Sandstone
Morrison
Formation
Navajo Sandstone
Kayenta Formation
Entrada Sandstone
Carmel Formation
Moenave
Formation
Wingate
Sandstone?
Chinle Formation
Moenkopi Formation
Kaibab Limestone
Coconino Sandstone
Supai Formation or Group
Water bearing in places
C Aquifer
QUATERNARY
and
TERTIARY
TERTIARY
T aquifer
CRETACEOUS
JURASSIC
TRIASSICPERMIAN
Modified from Harshbarger and others, 1966
N aquifer
D aquifer
Yale Point Sandstone
Wepo Formation
Toreva Sandstone
?
???
Shinarump Member
San Rafael
Group
Glen
Canyon
Group
Water bearing
EXPLANATION
Figure 2. Stratigraphic section showing rock formations and hydrogeologic units of the Black Mesa area, northeastern
Arizona (not to scale). Queries mark the stratigraphic extent of the Wingate Sandstone, because some outcrops formerly
mapped as Wingate are now considered part of the Moenave Formation (Billingsley and others, 2012; 2013). The Navajo
(N) aquifer is approximately 1,000 feet thick. T, Toreva; D, Dakota; C, Coconino.
4 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
used without treatment. The N aquifer, lying between the D and C
aquifers, is the major source of water for industrial and municipal
uses in the Black Mesa area. For this reason, groundwater data
collected for this report were exclusively from the N aquifer.
According to Eychaner (1983), the N aquifer comprises three
hydraulically connected formations—the Navajo Sandstone, the
Kayenta Formation, and the Wingate Sandstone—that function as
a single aquifer (g. 2). However, more recent geologic mapping
indicates the Wingate Sandstone is absent from much of the Black
Mesa area. Outcrops of sandstone previously mapped as Wingate
Sandstone in the Black Mesa area are now considered to be part
of the Moenave Formation (Billingsley and others, 2012, 2013).
Based on this recent geologic mapping, it is unclear if the Wingate
Sandstone is present at all in the Black Mesa area. If present, it
would be deeply buried in the northeastern part of the study area.
The N aquifer is conned under most of Black Mesa, and the
overlying stratigraphy limits recharge to this part of the aquifer.
The N aquifer is unconned in most areas surrounding Black
Mesa, and most recharge occurs where the Navajo Sandstone
is exposed in the area near Shonto, Ariz. (g. 1) (Lopes and
Hoffmann, 1997). Groundwater moves radially from the recharge
areas near Shonto to the southwest toward Tuba City, Ariz., to the
south toward the Hopi Reservation, and to the east toward Rough
Rock and Dennehotso, Ariz. (Eychaner, 1983).
Within the Black Mesa study area, the Navajo Nation and
the Hopi Tribe are the principal municipal water users, and the
PWCC is the principal industrial water user. Withdrawals from
the N aquifer in the Black Mesa area increased fairly consistently
from 1965 to 2005 and then decreased markedly in 2006 (table 1).
The PWCC began operating a strip mine in the northern part of
the study area in 1968 (g. 1). The PWCC’s mining operation
consisted of two mines on Black Mesa: the Kayenta mine, which
transported coal to the Navajo Generating Station by train, and the
Black Mesa mine, which transported coal 275 miles (mi) to the
Mohave Generating Station by a water-based coal slurry pipeline.
The PWCC operated both mines on Black Mesa from the
1970s until about 2005, when the Mohave Generating Station
ceased operations. On December 31, 2005, the PWCC reduced
pumping of the N aquifer by approximately 70 percent as a result
of discontinued use of the coal slurry pipeline that delivered water,
in addition to coal, to the Mohave Generating Station. The two
mines at the PWCC were then combined into the Black Mesa
Complex and continued to deliver coal to the Navajo Generating
Station by electric train until 2019. In August 2019, coal-mining
operations at the Black Mesa Complex ceased, due to the planned
closure of the Navajo Generating Station, which permanently
closed in November 2019. The PWCC continued to pump about
1,100–1,600 acre-feet (acre-ft) per year between 2006 and 2018,
primarily for dust control. Since cessation of mining in 2019, the
PWCC reduced its annual pumping to 200 acre-ft in 2020 and 160
acre-ft in 2021 (table 1).
Four major stream systems provide surface drainage for the
Black Mesa area. They are Moenkopi Wash, Dinnebito Wash,
Oraibi Wash, and Polacca Wash. All four stream systems have
headwaters high on Black Mesa and eventually drain into the
Little Colorado River to the south and southwest of the study area
(g. 1). Most reaches of these streams are ephemeral, owing only
in response to runoff from precipitation events, but a few short
reaches ow at least part of each year as a result of groundwater
discharge.
The members of the Navajo Nation and the Hopi Tribe have
been concerned about the long-term effects of withdrawals from
the N aquifer on available groundwater supplies, on stream and
spring discharge, and on groundwater chemistry. In 1971, these
water-supply concerns led to the establishment of a monitoring
program for the water resources in the Black Mesa area by the
U.S. Geological Survey (USGS) in cooperation with the Arizona
Water Commission, which was the predecessor to the present
Arizona Department of Water Resources. In 1983, the Bureau of
Indian Affairs (BIA) joined the cooperative effort. Since 1983, the
Navajo Tribal Utility Authority (NTUA); the PWCC; the Hopi
Tribe; and the Western Navajo, Chinle, and Hopi Agencies of the
BIA have assisted in the collection of hydrologic data.
Purpose and Scope
This report presents results of groundwater, surface-water,
and water-chemistry monitoring in the Black Mesa area from
January 2020 to December 2021. Additionally, the report uses
surface-water statistics from November and December 2019.
Continuous and periodic groundwater and surface-water data are
collected to monitor the possible effects of industrial and municipal
withdrawals from the N aquifer on groundwater levels, stream
and spring discharge, and groundwater chemistry. Groundwater
data include groundwater withdrawals (pumping), water levels,
spring-discharge rates, and water chemistry. Surface-water
data include discharge rates at four continuous-record
streamow-gaging stations. Recent groundwater and surface-water
data are compared with groundwater and surface-water data
from 1965 to 2021 to describe the overall status—and change
over time—of groundwater conditions in the N aquifer, as
well as to provide information on how the aquifer responds to
groundwater-development stresses. Some statistical analyses of the
data are included in this report to examine trends in the data that
characterize groundwater conditions in the N aquifer.
Previous Investigations
The USGS has prepared progress reports on the Black Mesa
monitoring program since 1978, and these progress reports are
summarized in table 2. The groundwater-level, surface-water
discharge, and water-chemistry data from the Black Mesa
monitoring program are contained in these progress reports and in
the USGS National Water Information System (NWIS) database
(https:/ /waterdata .usgs.gov/ az/ nwis/ ). Water-withdrawal data are
presented in tables in the progress reports.
Stream-discharge and periodic water-quality data
collected from Moenkopi Wash before the 1982 water year
were published by the USGS (1963–64a, b; 1965–74a, b;
1976–83). Stream-discharge data from water years 1983 to
2005 for Moenkopi Wash at Moenkopi (station 09401260),
Dinnebito Wash near Sand Springs (station 09401110), Polacca
Wash near Second Mesa (station 09400568), Laguna Creek at
Introduction 5
[Values are rounded to nearest 10 acre-feet (acre-ft). Data for 1965–79 from Eychaner (1983). Total withdrawals in Littin and Monroe (1996) were for the conned area of
the aquifer]
Dennehotso (station 09379180), and Pasture Canyon Springs
(station 09401265) in the Black Mesa area were published in
White and Garrett (1984, 1986, 1987, 1988), Wilson and Garrett
(1988, 1989), Boner and others (1989, 1990, 1991, 1992),
Smith and others (1993, 1994, 1995, 1996, 1997), Tadayon
and others (1998, 1999, 2000, 2001), McCormack and others
(2002, 2003), and Fisk and others (2004, 2005, 2006), and
were published online for water years 2006 to present (http:
//wdr.wate r.usgs.gov). Before the monitoring program, a large
data-collection effort in the 1950s resulted in a compilation
of well and spring data for the Navajo Nation and Hopi
Reservation (Davis and others, 1963).
Many interpretive studies have investigated the hydrology
of the Black Mesa area. Cooley and others (1969) made the rst
comprehensive evaluation of the regional hydrogeology of the Black
Mesa area. Eychaner (1983) developed a two-dimensional numerical
model of groundwater ow in the N aquifer. Brown and Eychaner
(1988) recalibrated Eychaner’s earlier model by using a ner grid
and by using revised estimates of selected aquifer characteristics.
GeoTrans, Inc. (1987) also developed a two-dimensional numerical
model of the N aquifer in the 1980s. In the late 1990s, HSIGeoTrans,
Inc., and Waterstone Environmental Hydrology and Engineering,
Inc. (1999) developed a three-dimensional numerical model of the N
aquifer and the overlying D aquifer.
Calendar
Year
Industrial
a
Municipal
b,c
Total
withdrawals
Confined Unconfined
1965 0 50 20 70
1966 0 110 30 140
1967 0 120 50 170
1968 100 150 100 350
1969 40 200 100 340
1970 740 280 150 1,170
1971 1,900 340 150 2,390
1972 3,680 370 250 4,300
1973 3,520 530 300 4,350
1974 3,830 580 360 4,770
1975 3,500 600 510 4,610
1976 4,180 690 640 5,510
1977 4,090 750 730 5,570
1978 3,000 830 930 4,760
1979 3,500 860 930 5,290
1980 3,540 910 880 5,330
1981 4,010 960 1,000 5,970
1982 4,740 870 960 6,570
1983 4,460 1,360 1,280 7,100
1984 4,170 1,070 1,400 6,640
1985 2,520 1,040 1,160 4,720
1986 4,480 970 1,260 6,710
1987 3,830 1,130 1,280 6,240
1988 4,090 1,250 1,310 6,650
1989 3,450 1,070 1,400 5,920
1990 3,430 1,170 1,210 5,810
1991 4,020 1,140 1,300 6,460
1992 3,820 1,180 1,410 6,410
1993 3,700 1,250 1,570 6,520
1994 4,080 1,210 1,600 6,890
1995 4,340 1,220 1,510 7,070
1996 4,010 1,380 1,650 7,040
1997 4,130 1,380 1,580 7,090
1998 4,030 1,440 1,590 7,060
1999 4,210 1,420 1,480 7,110
2000 4,490 1,610 1,640 7,740
Calendar
Year
Industrial
a
Municipal
b,c
Total
withdrawals
Confined Unconfined
2001 4,530 1,490 1,660 7,680
2002 4,640 1,500 1,860 8,000
2003 4,450 1,350 1,440 7,240
2004 4,370 1,240 1,600 7,210
2005 4,480 1,280 1,570 7,330
2006 1,200 1,300
d
1,600
d
4,100
d
2007 1,170 1,460 1,640 4,270
2008 1,210 1,430
e,f
1,560
e
4,200
f
2009 1,390 1,440 1,400 4,230
2010 1,170 1,450
d
1,420 4,040
d
2011 1,390 1,460
d
1,630 4,480
d
2012 1,370 1,380
d
1,260 4,010
d
2013 1,460 1,410
d
1,110
d
3,980
d
2014 1,580 1,280
d
1,310
d
4,170
d
2015 1,340 1,370
d
1,260
d
3,970
d
2016 1,090 1,380
d
1,070
d
3,540
d
2017 1,110 1,330 1,270
d
3,710
d
2018 1,170 1,370
d
1,130 3,670
d
2019 670 1,340
d
1,060
d
3,070
d
2020 200 1,370
d
1,110
d
2,680
d
2021 160 1,320
d
1,090
d
2,570
d
a
Metered pumpage from the conned part of the aquifer by Peabody
Western Coal Company
b
Does not include withdrawals from the wells equipped with windmills
c
Includes estimated pumpage 1965–73 and metered pumpage 1974–79 at
Tuba City; metered pumpage at Kayenta and estimated pumpage at Chilchinbito,
Rough Rock, Piñon, Keams Canyon, and Kykotsmovi before 1980; metered
and estimated pumpage furnished by the Navajo Tribal Utility Authority and the
Bureau of Indian Affairs and collected by the U.S. Geological Survey, 1980–85;
and metered pumpage furnished by the Navajo Tribal Utility Authority, the
Bureau of Indian Affairs, various Hopi Village Administrations, and the U.S.
Geological Survey, 1986–2021
d
Meter data were incomplete; therefore, municipal withdrawals are
estmated, and total withdrawal uses an estimation in the calculation
e
Conned and unconned totals were reversed in previous reports
f
Conned withdrawals are about 90 acre-feet greater than previously reported
Table 1. Withdrawals from the N aquifer, Black Mesa area, northeastern Arizona, 1965–2021.
6 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
Table 2. Tabulated list of progress reports for the Black Mesa monitoring program, 1978–2022.
[USGS, U.S. Geological Survey]
Year
published
Author(s) Title USGS report type and number
1978 U.S. Geological Survey Progress report on Black Mesa monitoring program—1977 Open-File Report 78–459
1985 Hill, G.W. Progress report on Black Mesa monitoring program—1984 Open-File Report 85–483
1986 Hill, G.W., and Whetten, M.I. Progress report on Black Mesa monitoring program—1985–86 Open-File Report 86–414
1987 Hill, G.W., and Sottilare, J.P. Progress report on the ground-water, surface-water, and quality-of-water
monitoring program, Black Mesa area, northeastern Arizona—1987
Open-File Report 87–458
1988 Hart, R.J., and Sottilare, J.P. Progress report on the ground-water, surface-water, and quality-of-water
monitoring program, Black Mesa area, northeastern Arizona—1987–88
Open-File Report 88–467
1989 Hart, R.J., and Sottilare, J.P. Progress report on the ground-water, surface-water, and quality-of-water
monitoring program, Black Mesa area, northeastern Arizona—1988–89
Open-File Report 89–383
1992 Sottilare, J.P. Results of ground-water, surface-water, and water-quality monitoring, Black
Mesa area, northeastern Arizona—1989–90
Water-Resources Investigations Report
92–4008
1992 Littin, G.R. Results of ground-water, surface-water, and water-quality monitoring, Black
Mesa area, northeastern Arizona—1990–91
Water-Resources Investigations Report
92–4045
1993 Littin, G.R. Results of ground-water, surface-water, and water-quality monitoring, Black
Mesa area, northeastern Arizona—1991–92
Water-Resources Investigations Report
93–4111
1995a Littin, G.R., and Monroe, S.A. Results of ground-water, surface-water, and water-quality monitoring, Black
Mesa area, northeastern Arizona—1992–93
Water-Resources Investigations Report
95–4156
1995b Littin, G.R., and Monroe, S.A. Results of ground-water, surface-water, and water-chemistry monitoring,
Black Mesa area, northeastern Arizona—1994
Water-Resources Investigations Report
95–4238
1996 Littin, G.R., and Monroe, S.A. Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—1995
Open-File Report 96–616
1997 Littin, G.R., and Monroe, S.A. Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—1996
Open-File Report 97–566
1999 Littin, G.R., Baum, B.M., and Truini,
Margot
Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—1997
Open-File Report 98–653
2000 Truini, Margot, Baum, B.M., Littin, G.R.,
and Shingoitewa-Honanie, Gayl
Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—1998
Open-File Report 00–66
2000 Thomas, B.E., and Truini, Margot Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona–1999
Open-File Report 00–453
2002a Thomas, B.E. Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2000–2001, and performance and sensitivity of the
1988 USGS numerical model of the N aquifer
Water-Resources Investigations Report
02–4211
2002b Thomas, B.E. Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2001–02
Open-File Report 02–485
2004 Truini, Margot, and Thomas, B.E. Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2002–03
Open-File Report 03–503
Introduction 7
Table 2. Tabulated list of progress reports for the Black Mesa monitoring program, 1978–2022.—Continued
[USGS, U.S. Geological Survey]
Year
published
Author(s) Title USGS report type and number
2005 Truini, Margot, Macy, J.P., and Porter, T.J. Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2003–04
Open-File Report 2005–1080
2006 Truini, Margot, and Macy, J.P. Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2004–05
Open-File Report 2006–1058
2007 Truini, Margot, and Macy, J.P. Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2005–06
Open-File Report 2007–1041
2008 Truini, Margot, and Macy, J.P. Ground-water, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2006–07
Open-File Report 2008–1324
2009 Macy, J.P. Groundwater, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2007–2008
Open-File Report 2009–1148
2010 Macy, J.P. Groundwater, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2008–2009
Open-File Report 2010–1038
2011 Macy, J.P., and Brown, C.R. Groundwater, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2009–2010
Open-File Report 2011–1198
2012 Macy, J.P., Brown, C.R., and Anderson, J.R. Groundwater, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2010–2011
Open-File Report 2012–1102
2014 Macy, J.P., and Unema, J.A. Groundwater, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2011–2012
Open-File Report 2013–1304
2016 Macy, J.P. and Truini, Margot Groundwater, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2012–2013
Open-File Report 2015–1221
2017 Macy, J.P., and Mason, J.P. Groundwater, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2013–2015
Open-File Report 2017–1127
2018 Mason, J.P., and Macy, J.P. Groundwater, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2015–2016
Open-File Report 2018–1193
2021 Mason, J.P. Groundwater, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2016–2018
Open-File Report 2021–1124
2022 Mason, J.P. Groundwater, surface-water, and water-chemistry data, Black Mesa area,
northeastern Arizona—2018–2019
Open-File Report 2022–1086
8 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
Kister and Hatchett (1963) made the rst comprehensive
evaluation of the chemistry of water collected from wells and
springs in the Black Mesa area. HSIGeoTrans, Inc. (1993) evaluated
the major-ion and isotopic chemistry of the D and N aquifers.
Lopes and Hoffmann (1997) analyzed groundwater ages, recharge,
and hydraulic conductivity of the N aquifer by using geochemical
techniques. Zhu and others (1998) estimated groundwater recharge
in the Black Mesa area by using isotopic data and ow estimates
from the N-aquifer model developed by GeoTrans, Inc. (1987).
Zhu (2000) estimated recharge using advective transport modeling
and the same isotopic data from the GeoTrans model. Truini and
Longsworth (2003) described the hydrogeology of the D aquifer
and the movement and ages of groundwater in the Black Mesa area
by using data from geochemical and isotopic analyses. Truini and
Macy (2005) looked at possible leakage through the conning unit
between the D aquifer and the N aquifer as part of an investigation
of the Carmel Formation.
Description of Study Area
The availability and chemistry of water resources within the
Black Mesa area are directly related to physiography, climate,
and geology. Physiography affects the movement of both surface
water and groundwater in the area, and climate affects the water
budget. The complex geologic history of the area has resulted in
the accumulation of abundant coal resources and inuences the
movement and chemistry of surface water and groundwater.
Mesa. In these areas, the aquifer is generally unconned. West
of Kayenta, Ariz., exposed N aquifer units form Skeleton Mesa
and the Shonto Plateau. At the southeast edges of these features,
the aquifer units are folded in the Organ Rock Monocline (g. 3)
and plunge steeply to the southeast below the younger Cretaceous
rocks of Black Mesa to form Long House Valley. The N-aquifer
units continue to the southeast under Black Mesa and eventually
reappear south of the Hopi mesas. The aquifer units pinch out
within a few miles from where they reappear. In general, the
conned portion of the N aquifer occurs where the aquifer units
are deeply buried beneath Black Mesa.
The paths of stream channels are also inuenced by
physiography. Geologic structural folds, joint patterns, rock types,
and topography all affect the ow of surface water in the study
area. Major streams of the study area are shown in gure 1. The
surface topography of Black Mesa slopes downhill from northeast
to southwest. Likewise, the major streams that drain Black Mesa
ow from northeast to southwest toward the Little Colorado River.
Climate
The climate in most of the Black Mesa area is broadly
classied by Hendricks (1985) as steppe, which is characterized
by limited amounts of precipitation. Much of the precipitation in
steppe regions evaporates before it can inltrate to groundwater.
As a result, the vegetation cover consists mostly of mesquite,
pinyon-juniper, and various grasses (Hendricks, 1985). A small
area around Tuba City, Ariz., is classied by Hendricks (1985) as
desert. This classication signies even less annual rainfall and
indicates a vegetative cover consisting mostly of creosote bush,
cacti, and sagebrush.
Physiography
The Black Mesa area is located in the
Colorado Plateaus physiographic province
of the Intermontane Plateaus Region (Raisz,
1972). The dominant physiographic feature
in the study area is Black Mesa itself, but
several smaller features play important
roles in the movement of surface water and
groundwater (g. 1). Black Mesa is the
remnant of a large sedimentary basin that has
undergone signicant tectonic uplift during
the past 70 million years. Parts of Black
Mesa, which were once below sea level,
now rise more than 6,000 ft above sea level.
As a result of this uplift, the region has gone
from a depositional cycle to an erosional
cycle. Much of the erosion responsible for
present-day topography likely occurred in
the past 10 million years (Lazear and others,
2013). Since uplift occurred, Black Mesa
has been dissected by streams, resulting
in the formation of several smaller mesas
such as the First, Second, and Third Mesas
(informally called the Hopi mesas).
The geologic units that compose the N
aquifer occur at or near the land surface in a
large extent around the periphery of Black
Figure 3. Aerial photograph showing the Organ Rock Monocline and folding strata of Skeleton
Mesa near Kayenta, Arizona. Photograph by Jodi Norris, used with permission.
Figure 3. Aerial photograph showing the Organ Rock Monocline and folding strata
of Skeleton Mesa near Kayenta, Ariz. The Navajo Sandstone is truncated in this part of
the monocline, forming the atirons along the lower part of the monocline. Photograph
by Jodi Norris, used with permission.
Description of Study Area 9
Mean annual precipitation for the Black Mesa area was
estimated using spatial-regression methods that incorporated
precipitation data from traditional weather stations and
high-altitude meteorological sites (Daly and others, 1994). Annual
precipitation in the Black Mesa area, which is based on 30-year
averages from 1981 to 2010, ranges from less than 6 inches (in)
in the lower elevation regions around the mesa to more than 16
in at the highest elevations on the mesa (g. 4; PRISM Climate
Group, 2018).
According to Sellers and Hill (1974), about 60 percent
of average annual precipitation in northeastern Arizona falls
between the months of May and October (primarily in July and
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Keams Canyon
Wash
APACHE COUNTY
NAVAJO COUNTY
COCONINO COUNTY
NAVAJO COUNTY
98
160
89
264
77
87
191
191
163
264
Dennehotso
Tsegi
Betatakin
Shonto
Shonto
Junction
Red Lake
Rare
Metals
Moenkopi
Chilchinbito
Kitsillie
Chapter
House
Forest Lake
Rocky
Ridge
Coal Mine
Canyon
Blue Canyon
Hard Rock
Pinon
Low
Mountain
Bacavi
Hotevilla
Kykotsmovi
Shipaulovi
Mishongnovi
Shungopavi
Second Mesa
Polacca
Keams
Canyon
Rough
Rock
Cameron
Page
Tuba City
Ganado
Chinle
Kayenta
COAL-LEASE
AREA
Boundary of Black Mesa
EXPLANATION
Annual precipitation, in inches
4.1 to 6.0
6.1 to 8.0
8.1 to 10.0
10.1 to 12.0
12.1 to 14.0
14.1 to 16.0
16.1 to 18.0
Black Mesa
Map area
ARIZONA
109°30'110°00’110°30'111°00’111°30'
36°30'
36°00’
37°00’
25 MILES
25 KILOMETERS0
0
Base from U.S. Geological Survey digital data, 2010
Lambert Conformal Conic projection
Standard parallels 29°30’ N. and 45°30’ N.
central meridian 111°30’ W.
Climate data from PRISM Climate Group, 2018;
30-year normal annual data, 1981-2010,
4 km resolution; July 2012
Figure 4. Map showing mean annual precipitation, Black Mesa area, Ariz., 1981–2010.
10 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
August). The authors report that, on average, the plateaus and
mesas of northeastern Arizona are the driest part of the state
during the colder half of the year and rarely receive heavy winter
precipitation. However, much of the groundwater contained in
the N aquifer was recharged during the late Pleistocene when the
temperature was cooler and precipitation amounts were higher
(Zhu and Kipfer, 2010).
Geology
Rocks of Triassic age and older are not discussed in detail in
this report because they are not signicant sources of groundwater
in the Black Mesa area. Instead, this section focusses on Jurassic
and younger rocks that are part of hydrologic systems used in
this area.
The stratigraphic section (g. 2) used in the current and
previous Black Mesa monitoring reports was modied from
Harshbarger and others (1966). The original stratigraphic section
showed the Wingate Sandstone between the Chinle Formation
and the Kayenta Formation, and it did not show the Moenave
Formation. More recently, Billingsley and others (2012, 2013)
concluded that sandstones in the Black Mesa area formerly mapped
in outcrop as Wingate Sandstone are, in fact, part of the Moenave
Formation. It is unclear if the Wingate Sandstone could be present
in the subsurface under parts of the Black Mesa area. Since the
two geologic units are considered coeval, the Moenave Formation
is shown as present and possibly intertongued with the Wingate
Sandstone in gure 2. Harshbarger and others (1966) considered
the eolian facies of the Wingate Sandstone to be a water-bearing
unit of the N aquifer. It is unclear if any of the sandstones now
mapped as Moenave Formation could be water bearing.
The Black Mesa area is the remnant of a large sedimentary
basin that has been uplifted and dissected by streams since its
original formation. When the sediments of the sedimentary rock
units (g. 2) in the Black Mesa area were deposited, the region had
a much lower surface elevation nearer to, and sometimes below, sea
level. As the thick sequence of sediment was being deposited, the
basin was slowly subsided and allowed more sediments from nearby
highlands to be deposited. The entire Colorado Plateau, including
Black Mesa, was then tectonically uplifted a mile above sea level
during the Tertiary by processes that are still not fully understood.
According to Flowers (2010, p. 671), Colorado Plateau “elevation
gain could have occurred in the early Tertiary associated with
Sevier-Laramide contraction, the middle Tertiary synchronous with
the proposed demise of the Laramide at slab, [or] the late Tertiary
coeval with regional extensional tectonism in adjacent provinces.”
Geologic Units Below the N Aquifer
The geologic units below the N-aquifer system are Triassic
and older in age (g. 2) and generally are not suitable as a water
supply in the Black Mesa area and will not be discussed in detail.
The Permian Coconino Sandstone and Kaibab Formation (g. 2)
probably could produce adequate quantities of water in the Black
Mesa area, but they are deeply buried and likely have total-dissolved
solids concentrations above what can be used without treatment.
Geologic Units of the N Aquifer
The geologic units associated with the N aquifer are
members of the Glen Canyon Group and include the Moenave
Formation, Wingate Sandstone, Kayenta Formation, and Navajo
Sandstone (g. 2). The group is named after Glen Canyon of
the Colorado River in southeastern Utah, where these units are
typically exposed (Harshbarger and others, 1957). The Glen
Canyon Group was originally thought to be Late Triassic to
Early Jurassic in age (Harshbarger and others, 1957), but more
recent paleontological and stratigraphic discoveries indicate the
group is largely Early Jurassic in age (Peterson and Pipiringos,
1979). According to Blakey and Ranney (2008), the Black Mesa
basin was slightly above sea level, and the climate was windy
and dry when the Glen Canyon Group was deposited. This led
to widespread deposition of eolian and uvial deposits (Blakey
and Ranney, 2008) that now compose the sandstone units of the
N aquifer.
Where the N aquifer is conned it is capped by the Carmel
Formation (g. 2), which is considered part of the San Rafael
Group; the Carmel Formation is discussed in this section because
it both connes the aquifer in places and hydraulically separates
the N aquifer from the overlying D aquifer in locations where the
D aquifer is present.
Moenave Formation
The Moenave Formation (g. 2) contains several members;
the most prominent one in the Black Mesa area is the Dinosaur
Canyon Member. According to Tanner and Lucas (2007), the
Moenave Formation was deposited in a mosaic of uvial,
lacustrine, and eolian subenvironments. They described trough
cross-bedded sands deposited on oodplains by ephemeral streams
owing north-northwest (relative to modern geographic position)
and silt deposited by sheet ow across broad interchannel ats.
Tanner and Lucas (2007) further described deposits from perennial
lakes that formed on terminal oodplains and experienced episodic
desiccation, along with dune and sand sheet deposits that were
emplaced by dominant east to south-southeast winds. Billingsley
and others (2012) described the lithology of the formation as
reddish-brown, thin-bedded, at-bedded, and crossbedded ne- to
coarse-grained uvial siltstone and silty sandstone.
The Moenave Formation forms distinctive orange-red
cliffs along the southwest edge of the Moenkopi Plateau and
west of Oraibi Wash on Garces Mesas (gs. 1, 5). The Moenave
Formation is not known to yield economic quantities of water in
the Black Mesa area.
Wingate Sandstone
It is uncertain if the Wingate Sandstone is present in the
Black Mesa area. Billingsley and others (2012, 2013) considered
the Wingate Sandstone to be absent from the Moenkopi Plateau
and the Hopi Buttes area and concluded that sandstones in
these areas formerly mapped as Wingate are, in fact, part of
the Moenave Formation. The Wingate Sandstone is considered
coeval to the Moenave Formation, and the two units intertongue
where both are present (Clemmensen and others, 1989). The
Description of Study Area 11
Figure 5. Aerial photograph showing the Moenave Formation outcropping on Garces Mesas,
northeastern Arizona. White caprock on top of the Moenave Formation is silicified sandstone of the
Kayenta Formation. Photograph by Jon Mason, U.S. Geological Survey.
Wingate Sandstone may be present deep in the subsurface of the
northeastern part of the Black Mesa area, but there is insufcient
corroborating information to verify this. Historically, the Wingate
Sandstone was divided into two members. The upper unit was the
Lukachukai Member, which consisted mostly of eolian, large-scale
crossbedded sandstone, whereas the lower Rock Point Member
mainly consisted of at-bedded uvial and lacustrine sediments
(McKee and MacLachlan, 1959). More recently, the Rock Point
Member has been assigned to the underlying Chinle Formation
and the Lukachukai Member has been dropped, leaving the name
Wingate Sandstone (Dubiel, 1989). At its type locality near Fort
Wingate, New Mexico, Harshbarger and others (1957, p. 10)
described the Wingate Sandstone as “pale-reddish-brown ne-
to very ne-grained quartz sandstone.” Harshbarger and others
(1966) considered the eolian facies of the Wingate Sandstone to be
a water-bearing unit of the N aquifer where present.
Kayenta Formation
According to Luttrell (1993), the Kayenta Formation was
mainly deposited by low- to moderately sinuous streams owing
into a back-arc basin from adjacent highlands. Luttrell reported
that sedimentary deposits in the north half of the formation’s
extent were likely deposited by perennial to intermittent streams
and contain courser material than deposits in the south half, which
were interpreted as being deposited by intermittent to ephemeral
streams. Sand dune and sand sheet deposits are present to a lesser
extent, mainly in the southern and western extents of the formation
(Luttrell, 1993). Imlay (1980) reported that the Kayenta Formation
consists of light gray to reddish-orange sandstone and siltstone.
The sandstone layers in the Kayenta Formation often form ledges,
whereas the siltstone layers form slopes. Wilson (1965) described
the thickness of the Kayenta Formation in south-central Utah
as increasing progressively from east to west in part owing to
intertonguing with the overlying Navajo Sandstone. Intertonguing
of the Kayenta Formation and Navajo Sandstone can be seen
clearly in outcrops of the two units along Moenkopi Wash near
Tuba City, Ariz. The Kayenta Formation is not known to yield
economic quantities of water in the Black Mesa area, although
sandstone layers within the formation may contribute some water
to the N aquifer.
Navajo Sandstone
The Navajo Sandstone is the principal water-bearing unit
of the N aquifer (g. 2). According to Harshbarger and others
(1957), it is an eolian deposit composed of sediments derived in
part from uvial deposits of the underlying Kayenta Formation.
Beitler and others (2005, p. 551) described the Navajo Sandstone
as a “subrounded, ne- to medium grained, well-sorted, quartz
arenite to subarkose sandstone.” The type and amount of cement
in the sandstone varies considerably and includes quartz, calcite,
dolomite, kaolinite, goethite, and hematite. It is characterized
by high-angle, large-scale cross-stratication and striking red
12 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
to white color variations. The red pigment in Navajo Sandstone
comes from thin hematite grain coatings. When these coatings
are chemically reduced by hydrocarbons migrating through pore
spaces, the sandstone is bleached to a lighter color (Beitler and
others, 2003). Bedding features in the Navajo Sandstone are
identical to those in modern dunes of the transverse and barchan
types. In the Black Mesa area, the Navajo Sandstone contains
many lenticular beds of cherty limestone deposited in interdune
lakes that can be seen between Tuba City, Ariz., and the Hopi
Buttes (Harshbarger and others, 1957).
The thickness of the Navajo Sandstone was reported by
Harshbarger and others (1957) as 950 ft near Shonto, Ariz., 478 ft
near Dennehotso, Ariz., 335 ft at Rock Point, Ariz., and 15 ft
northwest of Chinle, Ariz. Well-log data indicate that the top of
the Navajo Sandstone is about 2,500 ft below the Black Mesa
Complex and has a thickness in the mine area of around 700 ft.
In the Tuba City area, where the Navajo Sandstone and Kayenta
Formation are intertongued, well-log data indicate the combined
thickness of the intertongued portion to be greater than 500 ft.
Interpretation of the well log from Black Mesa observation well
3 (BM 3) located in Kayenta, Ariz., indicates that the top of the
Navajo Sandstone is about 155 ft below land surface and that the
unit is about 700 ft thick. In the Keams Canyon area, well logs
indicate the top of the Navajo Sandstone is about 900 ft below
land surface and has a thickness of about 150 ft. Well logs from
Kykotsmovi Village indicate the top of the Navajo Sandstone
is about 850 ft below land surface with a thickness of more
than 200 ft.
Carmel Formation
The Carmel Formation (g. 2) is part of the San Rafael
Group. Harshbarger and others (1957) reported the formation
in northeastern Arizona as Middle and Late Jurassic in age and
consisting of resistant ledge-forming sandstone beds 1–3 ft thick
separated by slope-forming siltstone strata 5–20 ft thick. They
further described the siltstone beds as weakly cemented grayish
red, weathering to pale reddish brown in color, and described the
sandstone beds as light greenish gray, weathering to pale yellow
(Harshbarger and others, 1957). In most places in northeastern
Arizona, the Carmel Formation is 100–200 ft thick, but the
Formation is thinner at the limits of its deposition (Harshbarger
and others, 1957).
According to Blakey and others (1983), the Carmel
Formation was deposited in two major transgressive-regressive
cycles of the Jurassic Western Interior Seaway, resulting in varied
depositional facies including uvial, eolian, coastal sabkha,
and marine. Where present in the Black Mesa area, the Carmel
Formation overlies the Navajo Sandstone, forming a conning
layer when the Navajo is fully saturated. The Carmel Formation is
absent in most of the study area where the N aquifer is unconned.
The Carmel Formation also hydraulically separates the
N aquifer from the overlying D aquifer in areas where both
aquifers are present. In the southern part of Black Mesa, there may
be some leakage from the D aquifer through the Carmel Formation
into the N aquifer (Truini and Macy, 2005). Because the D aquifer
has higher total-dissolved solids concentrations than the N aquifer,
leakage between the two could increase the total-dissolved solids
concentrations of the N aquifer thereby degrading its water quality.
Geologic Units of the D Aquifer
Entrada Sandstone
The Entrada Sandstone (g. 2) is part of the San Rafael
Group and was deposited during the Middle Jurassic in
widespread eolian sand seas that were adjacent to and inland
from a restricted marine seaway (Peterson, 1988; Blakey, 2008).
Harshbarger and others (1957) described two general facies of
the Entrada Sandstone in the Black Mesa area. The rst is a red,
silty, spheroidally weathered sandstone that often weathers into
hoodoos. The second is a clean, sandy facies that weathers into
rounded, massive cliffs. Where resistant cap rocks are present, the
Entrada Sandstone weathers into prominent cliffs. Billingsley and
others (2012) described the sediments in the Entrada Sandstone as
crossbedded, white, and interbedded white and red in color.
Harshbarger and others (1951) named a unit that overlies the
Entrada Sandstone near the Navajo community of Cow Springs
the Cow Springs Sandstone. Peterson (1988) reported that the
Cow Springs Sandstone is closely related to the Entrada Sandstone
and is often difcult to differentiate from it but claried that the
Cow Springs Sandstone can serve as a useful stratigraphic marker.
For this reason, Peterson (1988) reduced the rank of the Cow
Springs Sandstone to a member of the Entrada Sandstone. The
Entrada Sandstone is a water-bearing unit of the D aquifer in the
Black Mesa area.
Morrison Formation
The Morrison Formation (g. 2) was deposited in the Late
Jurassic by streams draining a magmatic arc developed along
the western edge of the North American continent (Turner
and Peterson, 2004). Harshbarger and others (1957) described
the Morrison Formation as primarily uvial, consisting of
alternating ood-plain and channel deposits. There are several
recognized members within the Morrison Formation, but only
a general description of the formation will be presented here.
The Morrison Formation is colorful. Cooley and others (1969)
reported formation colors of white, gray, green, red, orange,
purple, tan, yellow, and brown. They also reported mudstone,
siltstone, sandstone, conglomerate, and limestone lithologies
(Cooley and others, 1969). The extent of the Morrison
Formation is not fully known in the Black Mesa area. On the
west side of Black Mesa, there are areas such as Coal Mine
Canyon and Blue Canyon where the stratigraphically adjacent
units of Entrada Sandstone and Dakota Sandstone (g. 2) crop
out, but the Morrison Formation is missing. Cooley and others
(1969) show the Morrison Formation present in a band along
and to the north and northeast of Black Mesa. Where present,
sandstone beds in the Morrison Formation can compose a
water-bearing part of the D aquifer in the Black Mesa area
(Cooley and others, 1969).
Hydrologic Data 13
Dakota Sandstone
According to Aubrey (1992), the Dakota Sandstone (g. 2)
represents a complex variety of continental, marginal-marine,
and marine environments, and was deposited during the Late
Cretaceous in response to the westward transgression of
the Cretaceous Interior Seaway. Blakey and Ranney (2008)
described the Dakota Sandstone as comprising beach and
coastal plain deposits. Billingsley and others (2012) described
three previously identied informal units within the Dakota
Sandstone. In ascending order, they are the lower sandstone
member, the middle carbonaceous member, and the upper
sandstone member. O’Sullivan and others (1972) described the
lower sandstone member, along with some lenticular sandstone
beds in the middle carbonaceous member, as having relatively
high permeability, but they concluded that the upper sandstone
member has low permeability in most areas because of a high
silt content.
The general lithology of the Dakota Sandstone is described
by Billingsley and others (2012, p. 16) as “medium-to light-gray,
slope-forming, laminated to thin-bedded mudstone, siltstone, and
sandstone.” Cooley and others (1969) reported that the Dakota
Sandstone was the chief unit of the D aquifer system.
Mancos Shale
Kirkland (1991) reported that exposures of Mancos Shale
(g. 2) around Black Mesa represent an open marine environment
of the Cretaceous Interior Seaway. According to Blakey and
Ranney (2008), the Mancos Shale is drab gray and can form odd,
moonlike badlands. A good example of badlands weathering of
the Mancos Shale can be seen in Blue Canyon along Moenkopi
Wash on the Hopi Reservation. Presumably, the canyon takes
its name from the blueish-gray hue of the Mancos Shale in this
location. The Mancos Shale is a thick aquiclude that separates
groundwater in the underlying Dakota Sandstone from that in the
overlying sandstone aquifers of the Mesaverde Group (Cooley and
others, 1969).
Geologic Units of the T Aquifer
Mesaverde Group
According to Franczyk (1988), units of the Mesaverde
Group (g. 2) in the Black Mesa area (Toreva Formation, Wepo
Formation, and Yale Point Sandstone) were deposited during the
Late Cretaceous by further transgressions and regressions of the
Cretaceous Interior Seaway. Sandstone units in the Mesaverde
Group can be water-bearing units of the T aquifer. Many small
contact springs issue from Mesaverde sandstones around the
perimeter of Black Mesa and in canyons where the sandstones
have been truncated.
The Toreva Formation is likely a uvial and deltaic deposit
laid down as the Cretaceous Interior Seaway regressed after
depositing the Mancos Shale (Franczyk, 1988). The formation
has multiple members that represent the different depositional
environments associated with coastal deposition. The lithology of
the Toreva Formation is varied. Franczyk (1988) reported that the
formation includes sandstone, siltstone, mudstone, and shale, with
some carbonaceous beds.
Page and Repenning (1958) reported the Wepo Formation
is of mostly continental origin and consists of a thick series of
intercalated siltstone, mudstone, sandstone, and coal. According
to Franczyk (1988), the Wepo Formation was deposited while the
Cretaceous Interior Seaway was located to the northeast of Black
Mesa. Coal beds mined at the Black Mesa Complex occur in the
Wepo Formation.
Molenaar (1983) described the Yale Point Sandstone as
a coastal-barrier sandstone deposited during one of the last
transgressions of the Cretaceous Interior Seaway. According to
O’Sullivan and others (1972, p. 40), the Yale Point Sandstone is
“yellowish gray, weathers grayish orange, and is composed of
coarse- to ne-grained subrounded to subangular clear quartz.”
Bedding in the formation is lenticular, and individual units are
crossbedded (O’Sullivan and others, 1972).
Bidahochi Formation
According to a distribution map of the Bidahochi Formation
by Repenning and Irwin (1954), the only place the formation is
present in the Black Mesa area is around, and east of, the Hopi
Buttes. The Hopi Buttes themselves are part of the Bidahochi
Formation. Repenning and Irwin (1954) described the formation
as consisting of uvial and lacustrine deposits and basaltic
volcanic rock. Williams (1936) concluded that the lacustrine
sediments were deposited in a historical “lake of great extent”
which he called Hopi Lake. The proposed Hopi Lake (also called
Lake Bidahochi) and other proposed lakes of similar age have
been used to support a theory that basin spillover may have helped
create the Grand Canyon (Ranney, 2012). However, the extent
of this ancient lake is unknown, and the basin spillover theory
requires it to have been large. The Bidahochi Formation comprises
several units with an overall extent of about 10,000 mi
2
(Love,
1989), but the actual known extent of the lacustrine deposits is
much smaller. It is possible some of the lacustrine deposits have
either eroded away or are hidden below younger deposits, but this
remains unresolved. Harshbarger and others (1966) reported that
the lower part of the Bidahochi Formation, along with the volcanic
deposits, can be water bearing.
Hydrologic Data
Groundwater data collected for this report were exclusively
from the N aquifer. Water from the T and D aquifers is not used
in signicant quantities in the Black Mesa area. Water from the
T aquifer is used locally for livestock watering and to irrigate
small plots of land, but it probably cannot produce enough water
for municipal or industrial use. Water from the D aquifer is used
locally for livestock watering and in the past contributed to some
wells at the PWCC industrial well eld, but water from the aquifer
generally has total-dissolved solids concentrations that make it
unsuitable for municipal use.
14 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
From 2019 to 2021, activities of the Black Mesa
monitoring program included metered groundwater withdrawals,
measurements of groundwater levels, spring-discharge
measurements, streamow gaging, and the collection of
water-chemistry samples from springs. All data were collected
by the USGS except withdrawal data from NTUA wells, which
were compiled by NTUA personnel. Discharge measurements
were made at 4 springs, and groundwater-level measurements
were made at 25 of the 34 wells in the Black Mesa monitoring
network. The nine municipal wells in the network were not
measured in 2020 or 2021 because of access restrictions during
the Coronavirus pandemic. Of the 25 wells measured, 6 are
continuous-recording observation wells that have been outtted
for real-time data telemetry (denoted to as “BM observation well”
in table 3 and “BM” in text). The water-level data from these 6
continuous-recording observation wells are available on the NWIS
website (https:/ /waterdata .usgs.gov/ az/ nwis/ gw).
Groundwater-withdrawal data were compiled in
February 2022. Annual groundwater levels were typically
measured during the spring. Water-chemistry samples and
discharge measurements were collected from four springs
either in the fall of 2020 or in December 2021 (1 spring was
sampled in both fall 2020 and in December 2021). Annual
groundwater-withdrawal data are usually collected from 36
well systems within the BIA, NTUA, and Hopi Reservation
municipal systems, as well as from the PWCC industrial well
eld. Water meters from the BIA and Hopi Reservation wells
were not read at the end of 2020 because of the Coronavirus
pandemic. Therefore, the 2021 meters readings from these wells
represented 2 years of groundwater withdrawal. To estimate the
annual withdrawals from these wells, the reading was divided
by 2; half of the withdrawal was assigned to 2020 and half was
assigned to 2021. Well-identication information for wells
normally used in the Black Mesa monitoring network is shown
in table 3 (only 19 of these wells were used in 2020 and 25
were used in 2021). Streamow data are collected at four USGS
gaging stations and are available online (https:/ /waterdata
.usgs.gov/ az/ nwis/ rt). All annual data reported in this document
are for calendar years beginning January 1 and ending
December 31. Median winter streamow is reported as the
year in which the winter season began, which, for this report,
is 2019 and 2020. The period before appreciable groundwater
withdrawals began for mining or municipal purposes (about
1965) is referred to in this report as the “prestress period.”
Kendall’s tau trend analyses were applied to streamow data,
spring-discharge measurements, and water-chemistry samples
by using R Project for Statistical Computing (R Development
Core Team, 2022). The Kendall’s tau correlation coefcient
was computed between the measured data and time. The null
hypothesis was that no correlation existed between time and the
measured data; the alternate hypothesis was that time and the
measured data were correlated. A signicance level of 0.05 was
chosen to determine whether the result of the test for importance
of Kendall’s tau correlation coefcient was statistically signicant.
A two-sided p-value that was less than or equal to 0.05 indicated
that there was a statistically signicant correlation in the data, and
the null hypothesis would be rejected. If a signicant correlation
existed, the sign of the slope would indicate whether there was an
increasing or decreasing trend. P-values greater than 0.05 indicated
that there was no statistically signicant correlation between time
and concentration, and the null hypothesis would be accepted.
In addition, the Theil-Sen slope estimator was
calculated and plotted for streamow data, spring-discharge
measurements, and water-chemistry data using the NADA
R package (Lee, 2020). Closely related to Kendall’s tau, the
Theil-Sen slope estimator provides a slope for trends similar to
ordinary least-squares regression, but is less affected by outliers
(Helsel and others, 2020).
Withdrawals from the N Aquifer
Total annual withdrawals from the N aquifer are monitored
on a continuing basis to help determine the effects from
industrial and municipal pumping. Withdrawals from the
N aquifer are separated into three categories: (1) industrial
withdrawals from the conned area, (2) municipal withdrawals
from the conned area, and (3) municipal withdrawals from the
unconned areas. There are no industrial withdrawals from the
unconned areas within the study area. The industrial category
includes eight wells in the PWCC industrial well eld in the
northern Black Mesa area. The BIA, NTUA, and Hopi Tribe
operate about 70 municipal wells that are combined into 36 well
systems. Information about withdrawals from the N aquifer is
compiled primarily based on metered data from individual wells
operated by the BIA, NTUA, and Hopi Tribe (table 4). Meter
readings from BIA and Hopi Tribe facilities were not collected
for 2020 because of the Coronavirus pandemic. For this reason,
the readings collected for 2021 represented a 2-year period
(2020 and 2021). The withdrawal amounts for this period were
divided in two and half of the withdrawal was assigned to 2020
and half to 2021.
Withdrawals from wells equipped with windmills are not
measured in this monitoring program and are not included in
total withdrawal values reported here. About 270 windmills
in the Black Mesa area withdraw water from the N, D, T,
and alluvial aquifers, primarily for livestock. The estimated
total withdrawal by the windmills from the N aquifer is
about 65 acre-ft per year (HSIGeoTrans, Inc. and Waterstone
Environmental Hydrology and Engineering, Inc., 1999). The
total withdrawal by the windmills is less than 3 percent of the
total annual withdrawal from the N aquifer.
Withdrawals in Calendar Years 2020 and 2021
Compared to Previous Years
In 2020 and 2021, total groundwater withdrawal from the
N aquifer was estimated to be about 2,680 and 2,570 acre-feet
(acre-ft), respectively (table 1). Total withdrawals for municipal
use in 2020 were estimated to be about 2,480 acre-ft, and about
2,410 acre-ft were estimated in 2021. Municipal withdrawals
from the conned area averaged about 1,340 acre-ft per year,
Hydrologic Data 15
Table 3. Identification numbers and names of monitoring program study wells used for water-level measurements, 2020–21, Black
Mesa area, northeastern Arizona.
[Water levels from several wells in this table were unable to be measured in 2020 and 2021. “BM observation well” denotes continuous-recording observation
wells that have been outtted for real-time data telemetry. —, no data; NTUA, Navajo Tribal Utility Authority]
U.S Geological Survey
identification number
Name or location
Bureau of Indian Affairs
site number
355023110182701 Keams Canyon PM2 —
355230110365801 Kykotsmovi PM1 —
355236110364501 Kykotsmovi PM3 —
355428111084601 Goldtooth 3A-28
355924110485001 Howell Mesa 3K-311
360055110304001 BM observation well 5
a
4T-519
360217111122601 Tuba City 3K-325
360614110130801 Piñon PM6 —
360734111144801 Tuba City 3T-333
360904111140501 Tuba City NTUA 1R
b
—
360918111080701 Tuba City Rare Metals 2 —
360927111142401 Tuba City NTUA 3R
c
—
360953111142401 Tuba City NTUA 4 3T-546
361225110240701 BM observation well 6
a
—
361737110180301 Forest Lake NTUA 1 4T-523
361832109462701 Rough Rock 10T-258
362043110030501 Kits'iili NTUA 2 —
362149109463301 Rough Rock 10R-111
362406110563201 White Mesa Arch 1K-214
362823109463101 Rough Rock 10R-119
362936109564101 BM observation well 1
a
8T-537
363013109584901 Sweetwater Mesa 8K-443
363103109445201 Rough Rock 9Y-95
363143110355001 BM observation well 4
a
2T-514
363213110342001 Shonto Southeast 2K-301
363232109465601 Rough Rock 9Y-92
363309110420501 Shonto 2K-300
363423110305501 Shonto Southeast 2T-502
363727110274501 Long House Valley 8T-510
363850110100801 BM observation well 2
a
8T-538
364034110240001 Marsh Pass 8T-522
364226110171701 Kayenta West 8T-541
364248109514601 Northeast Rough Rock 8A-180
364338110154601 BM observation well 3
a
8T-500
a
Well with continuous water-level recorder
b
Well replaced Tuba City NTUA 1 (360904111140201) in 2018
c
Well replaced Tuba City NTUA 3 (360924111142201) in 2018
16 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
Table 4. Withdrawals from the N aquifer by well system, Black Mesa area, northeastern Arizona, calendar years 2020 and 2021.
[Well systems include one or more wells. Withdrawals, in acre-feet, are from owmeter measurements. —, no data; BIA, Bureau of Indian Affairs; USGS, U.S. Geological Survey; NTUA, Navajo Tribal Utility
Authority; PWCC, Peabody Western Coal Company; Hopi, Hopi Village Administrations]
Well system Owner Source of data
2020 withdrawals
a
2021 withdrawals
a
Confined aquifer Unconfined aquifer Confined aquifer Unconfined aquifer
Chilchinbito BIA USGS/BIA 4.1 — 4.1 —
Dennehotso BIA USGS/BIA — 4.8 — 4.8
Hopi High School BIA USGS/BIA 11.3 — 11.3 —
Hotevilla BIA USGS/BIA 22.4 — 22.4 —
Kayenta BIA USGS/BIA 15.1 — 15.1 —
Keams Canyon BIA USGS/BIA 51.4 — 51.4 —
Low Mountain BIA USGS/BIA 0
b
— 0
b
—
Piñon BIA USGS/BIA 0
b
— 0
b
—
Red Lake BIA USGS/BIA — 1.9 — 1.9
Rocky Ridge BIA USGS/BIA 3.2 — 3.2 —
Rough Rock BIA USGS/BIA 9.9 — 9.9 —
Second Mesa BIA USGS/BIA 5.7 — 5.7 —
Shonto BIA USGS/BIA — 93.7 — 93.7
Tuba City BIA USGS/BIA — 65.1 — 65.1
Chilchinbito NTUA USGS/NTUA 74.8 — 71.9 —
Dennehotso NTUA USGS/NTUA — 43.9 — 42.4
Forest Lake NTUA USGS/NTUA 16.7 — 18.0 —
Hard Rock NTUA USGS/NTUA 47.4 — 44.8 —
Kayenta NTUA USGS/NTUA 364.1 — 330.2 —
Kits’iili NTUA USGS/NTUA 19.2 — 19.4 —
Piñon NTUA USGS/NTUA 389.8 — 377.5 —
Red Lake NTUA USGS/NTUA — 45.7 — 48.7
Rough Rock NTUA USGS/NTUA 49.8 — 48.6 —
Shonto NTUA USGS/NTUA — 22.4 — 26.4
Shonto Junction NTUA USGS/NTUA — 71.5 — 69.7
Tuba City NTUA USGS/NTUA — 696.5 — 674.0
Mine Well Field PWCC PWCC 203.8 — 161.6 —
Bacavi Hopi USGS/Hopi 18.1 — 18.1 —
Hopi Civic Center Hopi USGS/Hopi 0.9 — 0.9 —
Hopi Cultural Center Hopi USGS/Hopi 1.5 — 1.5 —
Kykotsmovi Hopi USGS/Hopi 62.6 — 62.6 —
Mishongnovi Hopi USGS/Hopi 4.0 — 4.0 —
Moenkopi Hopi USGS/Hopi — 60.6 — 60.6
Polacca Hopi USGS/Hopi 145.8 — 145.8 —
Shipaulovi Hopi USGS/Hopi 22.4 — 22.4 —
Shungopovi Hopi USGS/Hopi 29.5 — 29.5 —
a
No meter readings were collected from BIA and Hopi wells in 2020, so the 2021 meter readings represented two-year withdrawals. Half of the two-year withdrawal was assigned to 2020 and half to 2021 for these wells
b
Well taken out of service
Hydrologic Data 17
while withdrawals from the unconned areas averaged about
1,100 acre-ft. Withdrawals for industrial use in 2020 and 2021
were about 200 and 160 acre-ft, respectively (tables 1, 5).
Withdrawals from the N aquifer have varied annually from
1965 to the present but amounts generally increased from 1965 to
2005 and decreased from 2006 to 2021. Beginning in 2006, the
PWCC reduced their pumping by about 70 percent. This reduction
in industrial pumping is reected by a decrease in total annual
withdrawals of about 44 percent from 2005 (tables 1, 5; g. 6).
Total withdrawals for the period of record (1965–2021) was
278,990 acre-ft; industrial withdrawals made up 56 percent and
municipal withdrawals composed 44 percent of total withdrawals
(table 5). Total withdrawals in 2021 were 2,570 acre-ft (tables
1, 5; g. 7), with 6 percent from industrial withdrawals and 94
percent from municipal withdrawals (table 5). Industrial pumping
decreased about 86 percent between 2018 and 2021. As discussed
earlier, the PWCC stopped producing coal from the Black Mesa
Complex in August 2019 due to the planned closure of the
Table 5. Total, industrial, and municipal withdrawals from the N aquifer for discrete time periods from 1965 to 2021, Black Mesa area,
northeastern Arizona.
Period
Total withdrawals
(acre-feet)
Industrial withdrawals
(acre-feet)
Municipal withdrawals
(acre-feet)
Percent
industrial
Percent
municipal
1965–2021 278,990 155,780 123,210 56 44
1965–2005 218,300 138,100 80,200 63 37
2006–2021 60,690 17,680 43,010 29 71
2020 2,680 200 2,480 7 93
2021 2,570 160 2,410 6 94
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
Industrial
Municipal
Total withdrawals
EXPLANATION
Withdrawals
Year
Withdrawal, in acre-feet
Figure 6. Plot of annual withdrawals from the N aquifer, Black Mesa area, northeastern Arizona, 1965–2021.
18 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
Na
va
jo
Cre
ek
Li
tt
le
Co
lo
ra
do
Ri
ver
Din
bi
ne
to
ca
Pol
ac
sh
a
W
sh
a
W
sh
a
W
bi
ai
Or
M
o
ko
e
n
pi
sh
a
W
La
C
Wash
h
i
e
n
l
gu
na
Cre
ek
Shonto
Kayenta
Page
37°
111°30'
111°
110° 30'
110°
109°30'
30'
36°
35°30'
Ganado
Keams
Canyon
Hopi High
School
COCONINO CO.
NAVAJO CO.
0
0
25 KILOMETERS
25 MILES
EXPLANATION
Well-system owner
Bureau of Indian Affairs
Navajo Tribal Utility Authority
Hopi Tribe
Peabody Western Coal Company (PWCC)
City of Page, Arizona
Piñon
Modified from Brown and Eychaner, 1988
Tuba City
Withdrawals from the N aquifer—
Piñon, well-system name;
377.5, total withdrawal in
acre-feet for 2021; * indicates
total withdrawal is an estimate.
The total is cumulative at
locations served by multiple
wells
COAL-LEASE
AREA
Red Lake
Kits’iili
Hard
Rock
Shipaulovi
Mishongnovi
Bacavi
Moenkopi
Shonto
Junction
Polacca
(0.9*)
(62.6*)
(3.2*)
(44.8)
(377.5)
Piñon
(377.5)
(11.3*)
(51.4*)
(145.8*)
(22.4*)
(4.0*)
(5.7*)
(1.5*)
(19.4)
Chilchinbito
(76.0*)
(47.2*)
(345.3*)
(120.1*)
(69.7*)
(50.6*)
(739.1*)
(60.6*)
(29.5*)
Second
Mesa
Forest Lake (18.0)
Chinle
NAVAJO CO.
APACHE CO.
Base from U.S. Geological Survey
digital data, 1:100,000, 1980
Lambert Conformal Conic projection
Standard parallels 29°30' and 45°30',
central meridian 96°00'
Hotevilla
PWCC (161.6)
Hopi Cultural Center
Kykotsmovi
Approximate boundary between confined
and unconfined conditions—
From Brown and Eychaner (1988)
Confined
Unconfined
Shungopavi
(18.1*)
(22.4*)
Hopi Civic Center
Rocky Ridge
Rough Rock
(58.4*)
Dennehotso
Confined and unconfined conditions in
the N aquifer within model boundary
(0)
Low Mountain
Boundary of mathematical model—
From Brown and Eychaner (1988)
Map
area
ARIZONA
Figure 7. Map showing well systems monitored for annual withdrawals from the N aquifer, Black Mesa area,
northeastern Arizona, calendar year 2021, and showing confined and unconfined zones of the N aquifer.
Hydrologic Data 19
Navajo Generating Station. Groundwater continues to be used
at the Black Mesa Complex for the reclamation process, but at a
much-diminished rate.
Groundwater Levels in the N Aquifer
Groundwater levels are monitored at wells that are
screened in the N aquifer to help understand the effects of
withdrawals on the potentiometric surface of the aquifer.
Groundwater in the N aquifer is under conned conditions
in the central part of the study area and under unconned or
water-table conditions around the periphery (g. 7). Because
of the different ways groundwater is released from storage,
conned and unconned aquifers respond dissimilarly to
groundwater withdrawal. When the same volume of water is
withdrawn from both conned and unconned aquifers by
pumping, the water-level decline in wells within the conned
aquifer will usually be much greater than the decline seen in
wells within the unconned aquifer. This is one reason water
levels have generally declined more in wells screened in the
conned portion of the N aquifer than in the unconned portion
within the monitoring area. A corollary to this phenomenon is
that water levels in conned aquifer wells also tend to recover
more quickly if pumping is decreased or stopped than they
would in unconned aquifer wells.
Direct comparison between water levels from conned
aquifer wells and unconned aquifer wells is of limited value.
The two sets of data are distinct populations that are best
considered individually. For this reason, a distinction is made
between water level changes from conned aquifer wells and
unconned aquifer wells in this section of the report.
Water levels were measured in 19 wells during spring
2020 and in 25 wells during spring 2021. Normally, 34 wells
are measured annually as part of the Black Mesa monitoring
network, but because of access restrictions during the
Coronavirus pandemic, not all wells could be measured. The
2021 water levels were compared to prestress levels (table 6) to
identify long-term changes. Of the 34 wells in the network, 6
are continuous-recording observation wells. Water levels were
measured quarterly using an electric tape in these six wells
during 2020 and 2021 to verify or update instrument calibration.
Only water levels from municipal and stock wells that were not
considered to have been recently pumped, affected by nearby
pumping, or blocked or obstructed are compared.
The wells used for water-level measurements are distributed
throughout the study area (g. 8). The wells were constructed
between 1934 and 2018, and the well depths range from 107 ft
near Rough Rock, Ariz., (8A-180) to 2,674 ft at Forest Lake, Ariz.
(Forest Lake NTUA 1). Depths to the top of the N aquifer range
from 0 ft near Tuba City, Ariz., to 2,205 ft at Kitsillie Chapter
House on top of Black Mesa (wells Tuba City NTUA 1R and
Kitʻsiili NTUA 2 in table 7, respectively).
Water levels measured in 2020 and 2021, and changes in
water levels from the prestress period to 2021, are shown in
table 6. The 34 wells in table 6 are grouped by location in the
unconned or conned area of the aquifer. From the prestress
period to 2021, water levels in the 13 wells measured in the
unconned part of the aquifer had a median change of −0.4 ft
(table 8), and water-level changes ranged from −42.4 ft at Long
House Valley (8T-510) to +8.4 ft at Tuba City Rare Metals
(g. 8 and table 6). Water levels in the 12 wells measured in the
conned part of the aquifer had a median change of −25.9 ft
(table 8), and water-level changes ranged from −133.7 ft at
BM 6 to +17.3 ft at Howell Mesa (3K-311) (g. 8 and table 6).
The well that usually shows the largest decline in water
level since predevelopment (Keams Canyon PM2) was not
measured in 2021. In 2020, it showed a 181.4 ft decline since
predevelopment.
20 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
a
Continuous recorder. Prestress levels were estimated from a groundwater model, except for well BM observation well 3 (Brown and Eychaner, 1988)
b
Water level is from a previous well drilled to a shallower depth at the same location
c
Water level is the rst water level measured after completion of well
Table 6. Water-level changes in monitoring program wells completed in the N aquifer, Black Mesa area, northeastern Arizona, from the prestress period (prior to 1965) to
calendar year 2021.
[“BM observation well” denotes continuous-recording observation wells that have been outtted for real-time data telemetry. The unit of measure for the “Water level, 2020, Water level, 2021, and Change in
water level” columns is in feet below land surface. —, no data; BIA, Bureau of Indian Affairs; NTUA, Navajo Tribal Utility Authority; R, reported from driller’s log]
Name or location
BIA site
number
Water level, 2020 Water level, 2021
Prestress period water level
Change in water level
Feet below land surface Date
Unconfined areas
BM observation well 1
a
8T-537 374.2 374.4 374.0 (
a
) −0.4
BM observation well 4
a
2T-514 216.8 216.8 216.0 (
a
) −0.8
Goldtooth 3A-28 233.5 233.8 230.0 10–29–53 −3.8
Long House Valley 8T-510 140.4 141.8 99.4 08–22–67 −42.4
Northeast Rough Rock 8A-180 — 44.0 46.9 11–13–53 2.9
Rough Rock 9Y-95 — 112.6 119.5 08–03–49 6.9
Rough Rock 9Y-92 — 165.1 168.8 12–13–52 3.7
Shonto 2K-300 171.7 171.6 176.5 06–13–50 4.9
Shonto Southeast 2K-301 289.3 289.1 283.9 12–10–52 −5.2
Shonto Southeast 2T-502 415.5 415.9 405.8 08–22–67 −10.1
Tuba City 3T-333 28.2 28.7 23.0 12–02–55 −5.7
Tuba City 3K-325 206.1 204.9 208.0 06–30–55 3.1
Tuba City Rare Metals 2 — 48.8 48.6 57.0 09–24–55 8.4
Tuba City NTUA 1R — — — 29.0
b
02–12–69 —
Tuba City NTUA 3R — — — 34.2
b
11–08–71 —
Tuba City NTUA 4 3T-546 — — 33.7 08–06–71 —
Confined areas
BM observation well 2
a
8T-538 205.4 203.9 125.0 (
a
) −78.9
BM observation well 3
a
8T-500 171.5 169.5 55.0 04–29–63 −114.5
BM observation well 5
a
4T-519 419.5 418.7 324.0 (
a
) −94.7
BM observation well 6
a
— 832.5 830.7 697.0 (
a
) −133.7
Forest Lake NTUA 1 4T-523 — — 1,096R 05–21–82 —
Howell Mesa 3K-311 452.5 445.7 463.0 11–03–53 17.3
Kayenta West 8T-541 282.6 269.1 230.0 03–17–76 −39.1
Keams Canyon PM2 — 473.9 — 292.5 06–10–70 —
Kits'iili NTUA 2 — — — 1,297.9
c
01–14–99 —
Kykotsmovi PM1 — — — 220.0 05–20–67 —
Kykotsmovi PM3 — — — 210.0 08–28–68 —
Marsh Pass 8T-522 131.7 133.0 125.5 02–07–72 −7.5
Piñon PM6 — — — 743.6 05–28–70 —
Rough Rock 10R-119 — 262.1 256.6 12–02–53 −5.5
Rough Rock 10T-258 — 310.5 301.0 04–14–60 −9.5
Rough Rock 10R-111 — 191.4 170.0 08–04–54 −21.4
Sweetwater Mesa 8K-443 — 546.4 529.4 09–26–67 −17.0
White Mesa Arch 1K-214 218.9 218.4 188.0 06–04–53 −30.4
Hydrologic Data 21
Shonto
Kayenta
Chilchinbito
Page
37°
111°30'
111°
110°30'
110°
109°30'
36°30'
36°
35°30'
Chinle
Ganado
Kykotsmovi
Keams
Canyon
Rough
Rock
COCONINO CO.
NAVAJO CO.
0
0
25 KILOMETERS
25 MILES
EXPLANATION
Well in which depth to water was
measured annually—First entry,
2K-300, is Bureau of Indian Affairs
site number or common name of
well; second entry, +4.9, is change
in water level, in feet, between
measurement made during the
prestress period and measurement
made during 2021
City of Page, Arizona
Piñon
Modified from Brown and Eychaner, 1988
BM3
8T-500
–114.5
9Y-92
+ 3.7
9Y-95
+6.9
8A-180
+2.9
8K-443
–17.0
10R-119
–5.5
10R-111
–21.4
10T-258
–9.5
Forest Lake
NTUA 1
---
Piñon
PM6
---
Keams
Canyon PM2
---
Tuba City
3T-333
–5.7
3T-546
---
3K-325
+
3.1
3A-28
–3.8
1K-214
–30.4
2K-300
+
4.9
2K-300
+
4.9
2K-301
–5.2
2T-502
–10.1
8T-510
–42.4
8T-522
8T-541
–39.1
Continuous water-level recording site
(observation well) maintained by the U.S.
Geological Survey—First entry, BM2, is
U.S. Geological Survey well number;
second entry, 8T-538, is Bureau of Indian
Affairs site number [---, no BIA number];
third entry, –78.9, is change in water level,
in feet, from simulated prestress period to
2021 [—, no 2021 data available]
BM2
8T-538
–78.9
COAL-LEASE
AREA
Kykotsmovi PM1
---
Kykotsmovi PM3
---
BM2
8T-538
– 78.9
BM5
4T-519
–94.7
BM6
---
–133.7
BM4
2T-514
–0.8
BM1
8T-537
–
0.4
NAVAJO CO.
APACHE CO.
Base from U.S. Geological Survey
digital data, 1:100,000, 1980
Lambert Conformal Conic projection
Standard parallels 29°30' and 45°30',
central meridian 96°00'
3K-311
+17.3
Tuba City Rare Metals 2
+
8.4
Kits’iili
NTUA 2
---
---
Tuba City
NTUA 1R
---
–
7.5
Dennehotso
Na
va
jo
Cre
ek
Li
tt
le
Co
lo
ra
do
Ri
ver
Din
bi
ne
to
ca
Pol
ac
sh
a
W
sh
a
W
sh
a
W
bi
ai
Or
M
o
ko
e
n
pi
sh
a
W
La
C
Wash
h
i
e
n
l
gu
na
Cre
ek
Approximate boundary between confined
and unconfined conditions—
From Brown and Eychaner (1988)
Confined
Unconfined
Confined and unconfined conditions in
the N aquifer within model boundary
Tuba City
NTUA 3R
Boundary of mathematical model—
From Brown and Eychaner (1988)
Map
area
ARIZONA
Figure 8. Map showing water-level changes in wells completed in the N aquifer, Black Mesa area, northeastern Arizona,
from the prestress period (prior to 1965) to 2021. (NTUA, Navajo Tribal Utility Authority).
22 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
Table 7. Well-construction characteristics, depth to top of N aquifer, and 2021 static water level for wells used in annual water-level measurements and for continuous-record
observation wells, 2019–2021, Black Mesa area, northeastern Arizona.
[“BM observation well” denotes continuous-recording observation wells that have been outtted for real-time data telemetry. —, no data; BIA, Bureau of Indian Affairs; ft, feet; ft bls, feet below land surface;
NTUA, Navajo Tribal Utility Authority]
BIA site number and (or) name
Date of well
completion
Land-surface elevation
(ft)
Well depth
(ft bls)
Screened/open
interval(s)
(ft bls)
Depth to top of
N aquifer
(ft bls)
a
2021 static
water level
(ft bls)
8T-537 (BM observation well 1) 02–01–1972 5,864 851 300–360 290 374.4
400–420
500–520
600–620
730–780
8T-538 (BM observation well 2) 01–29–1972 5,656 1,338 470–1,338 452 203.9
8T-500 (BM observation well 3) 07–29–1959 5,724 868 712–868 155 169.5
2T-514 (BM observation well 4) 02–15–1972 6,320 400 250–400 160 216.8
4T-519 (BM observation well 5) 02–25–1972 5,869 1,683 1,521–1,683 1,520 418.7
BM observation well 6 01–31–1977 6,332 2,507 1,954–2,506 1,950 830.7
1K-214 05–26–1950 5,771 356 168–356 250 218.4
2K-300 06–00–1950
b
6,264 300 260–300 0 171.6
2K-301 06–12–1950 6,435 500 318–328 30
c
289.1
378–500
2T-502 08–10–1959 6,670 523 12–523 25 415.9
3A-28 04–19–1935 5,381 358 (
d
) 60 233.8
3K-311 11–00–1934
b
5,855 745 380–395 615 445.7
605–745
3K-325 06–01–1955 5,250 450 75–450 30
c
204.9
3T-333 12–02–1955 4,940 229 63–229 24 28.7
3T-546 (Tuba City NTUA 4) 08–00–1971
b
5,206 612 256–556 0 (
e
)
4T-523 (Forest Lake NTUA 1) 10–01–1980 6,654 2,674 1,870–1,910 (
f
) (
e
)
2,070–2,210
2,250–2,674
8A-180 01–20–1939 5,200 107 60–107 40
c
44.0
8K-443 08–15–1957 6,024 720 619–720 590 546.4
8T-510 02–11–1963 6,262 314 130–314 125
c
141.8
8T-522 07–00–1963
b
6,040 933 180–933 480 133.0
8T-541 03–17–1976 5,885 890 740–890 700 269.1
9Y-92 01–02–1039 5,615 300 154–300 50
c
165.1
9Y-95 11–05–1937 5,633 300 145–300 68
c
112.6
10R-111 04–11–1935 5,757 360 267–360 210 191.4
10R-119 01–09–1935 5,775 360 (
d
) 310 262.1
10T-258 04–12–1960 5,903 670 465–670 460 310.5
Keams Canyon PM2 05–00–1970
b
5,809 1,106 906–1,106 900 (
e
)
Hydrologic Data 23
Table 7. Well-construction characteristics, depth to top of N aquifer, and 2021 static water level for wells used in annual water-level measurements and for continuous-record
observation wells, 2019–2021, Black Mesa area, northeastern Arizona.—Continued
[“BM observation well” denotes continuous-recording observation wells that have been outtted for real-time data telemetry. —, no data; BIA, Bureau of Indian Affairs; ft, feet; ft bls, feet below land surface;
NTUA, Navajo Tribal Utility Authority]
BIA site number and (or) name
Date of well
completion
Land-surface elevation
(ft)
Well depth
(ft bls)
Screened/open
interval(s)
(ft bls)
Depth to top
of N aquifer (ft
bls)
a
2021 static water
level
(ft bls)
Kits'iili NTUA 2 10–30–1993 6,780 2,549 2,217–2,223 2,205 (
e
)
2,240–2,256
2,314–2,324
2,344–2,394
2,472–2,527
Kykotsmovi PM1 02–20–1967 5,657 995 655–675 880 (
e
)
890–990
Kykotsmovi PM3 08–07–1968 5,618 1,220 850–1,220 840 (
e
)
Piñon PM6 02–00–1970
b
6,397 2,248 1,895–2,243 1,870 (
e
)
Tuba City NTUA 1R
g
11–02–2018 5,123 650 95-450 0 (
e
)
Tuba City NTUA 3R
h
11–02–2018 5,184 650 164-520 34 (
e
)
Tuba City Rare Metals 2 09–00–1955
b
5,108 705 100–705 255 48.6
a
Depth to top of N aquifer from Eychaner (1983) and Brown and Eychaner (1988)
b
00, indicates day is unknown
c
All material between land surface and top of the N aquifer is unconsolidated—soil, alluvium, or dune sand
d
Screened or open intervals are unknown
e
No water level collected in 2021 due to Coronavirus pandemic
f
Depth to top of N aquifer was not estimated
g
Well is a replacement for Tuba City NTUA 1
h
Well is a replacement for Tuba City NTUA 3
Table 8. Median changes in water levels in monitoring-program wells from the prestress period (prior to 1965) to 2021, N aquifer, Black
Mesa area, northeastern Arizona.
Years Aquifer conditions Number of wells Median change in water level (feet)
Prestress–2021 Unconned 13 −0.4
Conned 12 −25.9
24 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
Hydrographs of groundwater levels in the network of
wells observed annually show the temporal changes from the
1950s to present (gs. 9, 10). In most of the unconned areas,
water levels have changed only slightly (generally less than
10 ft). Near Shonto, Ariz., however, the water level in well
8T-510 (Longhouse Valley) has declined by 42.4 ft (g. 8;
table 6). Water levels have declined in most of the conned
area, but the magnitudes of declines are varied. Larger
declines have occurred near the municipal pumping centers
(wells Piñon PM6 and Keams Canyon PM2) and near the well
eld for the PWCC (BM6). Smaller declines occurred away
from the pumping centers in or near towns in the study area
(wells 10T-258, 10R-119, 8T-522; gs. 8, 9, 10).
Hydrographs for the Black Mesa continuous-record
observation wells (g. 11) show water levels since the early
1970s. The two wells in the unconned areas (BM1 and BM4)
P
EXPLANATION
Pumping
R
S
90
60
30
0
100
60
80
40
20
90
60
30
0
R
R
R
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015
2025
Recently pumping
Nearby site that taps same aquifer being pumped
P
A
B
C
D
E
F
G
Water level, in feet below land surface
R
R
R
P
P
R
0
30
30
60
90
120
60
90
170
200
230
260
220
250
280
190
2020
S
S
Figure 9. Plots of observed water levels in annual observation wells 3A-28 (A), 3K-325 (B), 3T-333 (C), Tuba City NTUA
1R (D), 3T-546 (NTUA 4) (E), Tuba City NTUA 3R (F), Rare Metals 2 (G), 2K-300 (H), 2K-301 (I), 2T-502 (J), 8T-510 (K), 8A-180
(L), 9Y-92 (M), and 9Y-95 (N) in unconfined areas of the N aquifer, Black Mesa area, northeastern Arizona, 1950–2021.
Replacement wells NTUA 1R and NTUA 3R were drilled in 2018 to replace wells NTUA 1 and NTUA 3. NTUA, Navajo Tribal
Utility Authority.
Hydrologic Data 25
have shown small seasonal or year-to-year variation since
1972 but show no apparent long-term decline. In the conned
area, water levels (not corrected for barometric pressure
effects or seasonal effects) in wells BM2, BM3, BM5, and
BM6 consistently declined from the 1970s to the mid-2000s
(g. 11). After the mid-2000s, water levels in BM2, BM5,
and BM6 began to level off and then to rise. The water-level
recoveries in BM2, BM5, and BM6 since the mid-2000s have
been 15.7 ft, 9.6 ft, and 32.4 ft, respectively. Water levels in
BM3 are more variable because of nearby municipal pumping.
After the mid-2000s, water levels in BM3 continued to vary,
but the overall trend attened out by around 2010 (g. 11).
P
EXPLANATION
Pumping
R
Recently pumping
H
I
J
K
L
M
N
Water level, in feet below land surface
R
R
R
R
R
R
R
R
R
R
P
70
100
130
0
30
60
130
160
190
70
100
130
220
90
160
1950 1955 1960 1965
1970
1975 1980 1985 1990 1995 2000 2005 2010
130
160
190
220
400
430
460
370
270
300
330
240
R
R
R
R
R
R
R
160
2015 2025
P
R P
P
P
P
R
R
2020
Figure 9.—Continued
26 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
P
EXPLANATION
Pumping
R
S
Recently pumping
Nearby site that taps same aquifer being pumped
A
B
C
D
E
F
Water level, in feet below land surface
R
R
P
P
230
260
R
700
750
800
850
900
R
420
450
480
510
250
300
350
400
450
500
200
170
R
220
250
280
190
950
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
1,090
1,110
1,130
1,150
1,170
1,190
1,070
P
R
R
2015
550
P
2025
P
2020
S
Figure 10. Plots of observed water levels in annual observation wells 4T-523 (Forest Lake NTUA 1) (A), 1K-214 (B), Piñon PM6 (C),
3K-311 (D), Keams Canyon PM2 (E), Kykotsmovi PM1 (F), Kykotsmovi PM3 (G), 8T-522 (H), 8T-541 (I), 8K-443 (J), 10R-111 (K), 10R-119
(L), 10T-258 (M), and Kitsʻiili NTUA 2 (N) in confined areas of the N aquifer, Black Mesa area, northeastern Arizona, 1953–2021.
NTUA, Navajo Tribal Utility Authority.
Hydrologic Data 27
P
EXPLANATION
Pumping
R
S
Recently pumping
Nearby site that taps same aquifer being pumped
G
H
I
J
K
L
M
N
Water level, in feet below land surface
R
P
240
220
260
280
300
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
1,300
1,350
1,400
1,250
300
330
360
270
R
490
520
550
580
320
200
R
R
R
S
180
210
240
150
110
140
170
80
250
280
310
220
R
R
P
210
240
270
180
2015
2025
P
R
P
P
R
2020
R
R
S
S
R
R
Figure 10.—Continued
28 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
Water-level change from assumed equilibrium, in feet
NOTE: Well vandalized and missing data from May 1979 to March 1984
NOTE: Measured
intermittently
before 1972
–120
–100
–80
–60
–40
–20
0
–100
–80
–60
–40
–20
0
–100
–80
–60
–40
–20
0
–5
0
5
10
–10
–5
0
5
10
–10
1965 1970 1975 1980 1985 1990 1995 2000 2005 20101960
–120
–100
–80
–60
–40
–20
–140
–160
–180
2015
2025
2020
A
B
C
D
E
F
Figure 11. Plots of observed groundwater levels in continuous-record observation wells BM1–BM6 (A–F) in the N aquifer,
Black Mesa area, northeastern Arizona, 1963–2021.
Hydrologic Data 29
Spring Discharge from the N Aquifer
Groundwater in the N aquifer discharges from many springs
around the margins of Black Mesa, and changes to the discharge
from those springs could indicate effects of withdrawals from
the N aquifer. Moenkopi School Spring (360632111131101),
Burro Spring (354156110413701), Pasture Canyon Spring
(361021111115901), and Unnamed Spring near Dennehotso
(364656109425400) have been measured intermittently since the
late 1980s. Three of the springs were measured for discharge in
2020 and the fourth was measured in 2021. Additionally, trend
analyses were performed on the ow data from the four springs.
Moenkopi School Spring, also called Susunova Spring
by the Hopi Tribe, is in the western part of the Black Mesa
area (g. 12). Discharge from Moenkopi School Spring was
measured in December 2021 using the volumetric method
EXPLANATION
W
a
s
h
D
i
n
n
e
b
i
t
o
le
Co
lo
ra
do
Ri
ver
Li
tt
Na
va
jo
Cre
ek
sh
a
W
sh
a
W
M
o
ko
e
n
pi
ca
Pol
ac
bi
ai
Or
sh
a
W
La
gu
na
Cre
ek
C
Wash
h
i
e
n
l
Shonto
Chinle
Ganado
Tuba City
Kayenta
Dennehotso
Betatakin
Keams
Canyon
Red Lake
Kykotsmovi
Page
COAL-LEASE
AREA
Pasture Canyon
Spring
3A-5
09400568
09401110
Moenkopi
School
Spring
3GS-77-6
09401265
09401260
Moenkopi
School
Spring
3GS-77-6
09401260
Streamflow-gaging station operated
by the U.S. Geological survey—
Number is station identification
City of Page, Arizona
Spring at which discharge was
measured and water-chemistry
sample was collected—Number
is spring identification
Burro
Spring
6M-31
Unnamed
Spring
near
Dennehotso
COCONINO CO.
NAVAJO CO.
NAVAJO CO.
APACHE CO.
37°
111°30'
111°
110°30'
110°
109°30'
30'
36°
35°30'
0
0
25 KILOMETERS
25 MILES
Modified from Brown and Eychaner, 1988
Base from U.S. Geological Survey
digital data, 1:100,000, 1980
Lambert Conformal Conic projection
Standard parallels 29°30' and 45°30',
central meridian 96°00'
Pasture Canyon
Spring
Moenkopi School
Spring
Burro
Spring
Unnamed Spring near Dennehotso
Pasture Canyon
Spring
Moenkopi School
Spring
Burro
Spring
Unnamed Spring near Dennehotso
Approximate boundary between confined
and unconfined conditions—
From Brown and Eychaner (1988)
Confined
Unconfined
Confined and unconfined conditions in
the N aquifer within model boundary
Boundary of mathematical model—
From Brown and Eychaner (1988)
Map
area
ARIZONA
Figure 12. Map of surface-water
and water-chemistry data-collection
sites in the N aquifer, Black Mesa
area, northeastern Arizona,
2019–2021. Photographs by the U.S.
Geological Survey.
30 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
and was compared to discharge data from previous years to
determine changes over time (g. 13A). The trend for discharge
measurements at this spring is not corrected for seasonal
variability. In 2021, the measured discharge from Moenkopi
School Spring was 9.1 gallons per minute (gal/min) (table 9).
A Kendall’s tau analysis, using the Theil-Sen slope estimator,
indicated a decreasing trend (p<0.05) of about 0.3 gal/min per
year during the period of record (g. 13A).
Burro Spring is in the southwestern part of the study
area and discharges from the Navajo Sandstone and alluvium
(g. 12). Burro Spring discharges from the aquifer through
a metal pipe and into a cement trough for livestock. As in
previous years, the 2020 discharge measurement point was
from the end of the metal pipe before the livestock trough.
Discharge at Burro Spring has uctuated since 1989 between
0.2 and 0.4 gal/min, but there is no signicant (p>0.05) trend
A
Note:
Kendall’s tau = –0.67
-
Slope of Theil-Sen line is significantly different from zero (p<0.05)
Note:
Kendall’s tau = –0.10
-
Slope of Theil-Sen line is not significantly different from zero (p>0.05)
17.0
15.0
13.0
11.0
45.0
43.0
41.0
39.0
37.0
35.0
33.0
31.0
27.0
25.0
23.0
30.0
25.0
20.0
15.0
10.0
5.0
1985 1990 1995 2000 2005 2010 2015 2020
2025
0.0
9.0
7.0
5.0
B
C
D
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
Discharge, in gallons per minute
0.05
EXPLANATION
Theil-Sen line (p-value < 0.001)
Spring discharge
EXPLANATION
Theil-Sen line (p-value = 0.54)
Spring discharge
EXPLANATION
Theil-Sen line (p-value = 0.46)
Spring discharge
EXPLANATION
Theil-Sen line (p-value = 0.01)
Spring discharge
Note:
Kendall’s tau = –0.41
-
Slope of Theil-Sen line is significantly different from zero (p<0.05)
Note:
Kendall’s tau = 0.11
-
Slope of Theil-Sen line is not significantly different from zero (p>0.05)
Canyon Spring (361021111115901) (C); and Unnamed Spring near Dennehotso (364656109425400) (D), N Aquifer, Black Mesa area,
northeastern Arizona, 1987–2021. Moenkopi School Spring data from 1952 and Pasture Canyon Spring data from 1988 to 1993 are
not shown because they were taken from different measuring locations.
Figure 13. Plots of discharge from Moenkopi School Spring (360632111131101) (A); Burro Spring (354156110413701) (B); Pasture
Hydrologic Data 31
from a Kendall’s tau analysis (g. 13B). In 2020, the measured
discharge was 0.3 gal/min (table 10). The spring was visited in
2021 as well, but the discharge pipe was plugged, so a discharge
measurement could not be collected.
Pasture Canyon Spring is in the western part of the study area
and discharges from the Navajo Sandstone and alluvium (g. 12).
This report refers to Pasture Canyon Spring when referencing the
spring where water chemistry samples are collected and where
spring discharge is measured, whereas the name Pasture Canyon
Springs refers to the streamow gaging station. Discharge is
measured at two locations: where the spring issues from the
Navajo Sandstone (also the water-quality sampling point) and
farther down the canyon at the USGS gaging station (Pasture
Canyon Springs 09401265). The USGS gaging station at Pasture
Canyon measures the discharge from Pasture Canyon Spring as
well as additional discharge from seeps in Pasture Canyon. As in
previous years, discharge was measured at Pasture Canyon Spring
at its emergence point in October 2020 using the volumetric
method. The measured discharge was 40.3 gal/min (table 11),
which indicated a decrease in discharge of about 2.7 gal/min from
the 2019 measurement. Since 1995, discharge at Pasture Canyon
Spring has uctuated between 26.5 and 43.0 gal/min, but there
Table 9. Discharge from Moenkopi School Spring, N aquifer,
Black Mesa area, northeastern Arizona, 1952–2021.
[Discharges are measured volumetrically and do not represent the total
discharge from the springs. Geologic unit and Bureau of Indian Affairs site
number (in parentheses) listed above dates and measured discharge]
Date of
measurement
Discharge, in gallons per minute
Navajo Sandstone (3GS-77-6)
a
05–16–52 40.0
04–22–87 16.0
b
11–29–88 12.5
b
02–21–91 13.5
b
04–07–93 14.6
b
12–07–94 12.9
b
12–04–95 10.0
b
12–16-96 13.1
b
12–17–97 12.0
b
12–08–98 13.3
b
12–13–99 13.7
b
03–12–01 10.2
b
06–19–02 11.2
b
05–01–03 11.2
b
03–29–04 12.2
b
04–04–05 11.5
b
03–13–06 11.1
b
05–31–07 9.0
b
06–03–08 8.3
b
06–03–09 8.0
b
06–14–10 7.4
b
06–10–11 9.0
b
06–07–12 6.3
b
07–29–13 6.4
b
08–27–14 6.3
b
06–21–16 6.0
b
07–11–17 6.8
b
06–06–18 6.4
b
04–22–19 7.5
b
12–22–21 9.1
b
a
Interngering with the Kayenta Formation at this site
b
Discharge measured at water-quality sampling site and at a different point
than the measurement in 1952
Table 10. Discharge from Burro Spring, N aquifer, Black Mesa
area, northeastern Arizona, 1989–2021.
[Discharges are measured volumetrically and do not represent the total
discharge from the springs. Geologic unit and Bureau of Indian Affairs site
number (in parentheses) listed above dates and measured discharge]
Date of
measurement
Discharge, in gallons per minute
Navajo Sandstone (6M-31)
12–15–89 0.4
12–13–90 0.4
03–18–93 0.3
12–08–94 0.2
12–17–96 0.4
12–30–97 0.2
12–08–98 0.3
12–07–99 0.3
04–02–01 0.2
04–04–02 0.4
04–30–03 0.4
04–06–04 0.2
a
03–28–05 0.2
03–28–06 0.2
06–04–09 0.3
06–07–10 0.3
06–08–11 0.4
06–14–12 0.3
07–30–13 0.3
09–02–14 0.3
06–23–16 0.2
07–18–17 0.3
06–06–18 0.3
04–22–19 0.3
11–02–20 0.3
a
Discharge is approximate because the container used for the volumetric
measurement was not calibrated
32 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
is no signicant (p>0.05) trend from a Kendall’s tau analysis
(g. 13C). The discharge data measured at this spring are not
corrected for seasonal variability.
Unnamed Spring near Dennehotso, also called Black
Water spring by local residents, is the only spring located in the
northeastern part of the study area (g. 12), and it discharges
from the Navajo Sandstone. As in previous years, measurements
at Unnamed Spring near Dennehotso are made using a ume.
Discharge has decreased markedly at Unnamed Spring near
Dennehotso since 2005. That year, the discharge at the spring was
21.5 gal/min. The discharge was not measured again until 2010,
when it was 9.0 gal/min. In 2020, discharge was 11.6 gal/min
(table 12). For the period of record, which includes a gap in data
from 2005 to 2010, a decreasing trend (p<0.05) is evident from a
Kendall’s tau analysis (g. 13D). The discharge data measured at
this spring are not corrected for seasonal variability.
Surface-Water Discharge, Calendar Years
2020–2021
Continuous surface-water discharge data have been
collected for various time periods at selected streams since the
monitoring program began in 1971. Surface-water discharge
in the study area generally originates as groundwater that
discharges to streams or as surface runoff from rainfall or
snowmelt. Groundwater discharges to some stream reaches at a
fairly constant rate throughout the year; however, the amount of
groundwater discharge that results in surface ow is affected by
seasonal uctuations in evapotranspiration (Thomas, 2002a). In
contrast, the amount of rainfall or snowmelt runoff varies widely
throughout the year. In winter and spring, the amount and
timing of snowmelt runoff are a result of the temporal variation
in factors such as snow accumulation, air temperatures, and rate
Table 11. Discharge from Pasture Canyon Spring, N aquifer,
Black Mesa area, northeastern Arizona, 1988–2021.
[Discharges are measured volumetrically and do not represent the total dis-
charge from the springs. Geologic unit, lithology, and Bureau of Indian Affairs
site number (in parentheses) listed above dates and measured discharge]
Date of
measurement
Discharge, in gallons per minute
Navajo Sandstone, alluvium (3A-5)
11–18–88 211
a
03–24–92 233
a
10–12–93 211
a
12–04–95 38.0
b
12–16–96 38.0
b
12–17–97 40.0
b
12–10–98 39.0
b
12–21–99 39.0
b
06–12–01 37.0
b
04–04–02 37.0
b
05–01–03 30.9
b
04–26–04 30.6
b
04–27–05 33.3
b
06–03–08 29.4
b
06–03–09 31.1
b
06–14–10 34.3
b
06–09–11 31.4
b
06–07–12 26.5
b
07–29–13 35.7
b
08–27–14 39.3
b
06–21–16 37.5
b
07–11–17 43.0
b
06–06–18 42.0
b
04–22–19 43.0
b
10–06–20 40.3
b
a
Discharge measured in channel below water-quality sampling point
b
Discharge measured at water-quality sampling point about 20 feet below
upper spring on west side of canyon
Table 12. Discharge from Unnamed Spring near Dennehotso,
N aquifer, Black Mesa area, northeastern Arizona, 1954–2021.
[Discharges are measured volumetrically and do not represent the total
discharge from the springs. Geologic unit and Bureau of Indian Affairs site
number (in parentheses) listed above dates and measured discharge]
Date of
measurement
Discharge, in gallons per minute
Navajo Sandstone (8A-224)
a
10–06–54 1
b
06–27–84 2
b
11–17–87 5
b
03–26–92 16.0
10–22–93 14.4
12–05–95 17.0
12–19–96 15.7
12–30–97 25.6
12–14–98 21.0
12–15–99 14.8
03–14–01 26.8
04–03–02 5.8
07–15–02 9.0
05–01–03 17.1
04–01–04 12.6
04–06–05 21.5
06–17–10 9.0
06–04–12 4.5
08–06–13 6.7
09–03–14 8.1
10–26–16 9.0
07–03–18 3.0
04–23–19 12.0
10–13–20 11.6
a
Discharge measured in channel below water-quality sampling point
b
Discharge measured at a different point than later measurements
Hydrologic Data 33
of snowmelt. However, snowmelt usually does not lead to large
runoff events on any of the main four washes in the Black Mesa
area. Rainfall can occur throughout the year but occurs more
typically during the summer months than during other times
of the year. The amount and timing of rainfall depends on the
intensity and duration of thunderstorms during the summer and
on mid-latitude, low-pressure systems during the fall, winter,
and spring.
In 2020, discharge data were collected at four
continuous-recording streamow-gaging stations. However, in
2021, discharge data were only collected at Moenkopi Wash
at Moenkopi, Ariz., (09401260) and Pasture Canyon Springs
near Tuba City, Ariz., (09401265) owing to a reduction in
funding (g. 14). Data collection at these stations began in
July 1976 (Moenkopi Wash at Moenkopi, Ariz., 09401260),
June 1993 (Dinnebito Wash near Sand Springs, Ariz.,
09401110), April 1994 (Polacca Wash near Second Mesa,
Ariz., 09400568), and August 2004 (Pasture Canyon Springs
near Tuba City, Ariz., 09401265) (table 13). Most of the daily
mean discharge values highlighted as estimated (red lines) in
gure 14 were either estimated because the streamow record
was affected by ice during the winter months or because the
stage recorder was damaged during high-ow conditions.
Estimated daily values are based on adjacent good records,
records from comparable stations, and discrete discharge
measurements. Areas of hydrographs in gure 14 where no
line is present represent periods when mean daily discharge
was zero or near zero. The hydrographs present mean daily
discharge using a logarithmic axis, which cannot have a
zero value. The geologic and hydrologic settings, along with
trend analyses of base ow at the four streamow sites, are
described briey below.
1
0.1
0.01
C
1,000
100
10
1
0.1
0.01
10,000
A
B
J F M A M JJ A S O N D J F M A M JJ A S O N D
20212020
J F M A M JJ A S O N D J F M A M JJ A S O N D
20212020
1
0.1
1
0.1
0.2
0.4
0.6
0.8
D
Discharge, in cubic feet per second
Estimated daily mean discharge
Daily mean discharge
EXPLANATION
0.2
0.4
0.6
0.8
0.4
0.4
Gage discontinued on 10/1/2020
Gage discontinued on 10/1/2020
Figure 14. Plots of daily mean discharge for Moenkopi Wash at Moenkopi, Ariz. (09401260) (A); Dinnebito Wash near Sand
Springs, Ariz. (09401110) (B); Polacca Wash near Second Mesa, Ariz. (09400568) (C); and Pasture Canyon Springs near Tuba
City, Ariz. (09401265) (D), Black Mesa area, northeastern Arizona, calendar years 2020–2021. Most daily mean discharge
values highlighted as estimated were either estimated because the streamflow record was affected by ice during the
winter months or because the stage recorder was damaged during high-flow conditions.
34 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
Moenkopi Wash
Moenkopi Wash has a drainage area of 1,629 mi
2
and
drains a large portion of the western part of Black Mesa.
The streamow gage is located near the village of Moenkopi
in a portion of the wash that cuts down into interbedded
Navajo Sandstone and Kayenta Formation. During the period
of streamow gage operation, there has generally been
continuous ow at the gage except for the summer months,
when the stream is often dry at the gage (g. 14). Monsoon
rain events occurring between July and September can result
in large, sediment-laden ows in Moenkopi Wash. The
maximum instantaneous discharge recorded at the gage was
10,100 cubic feet per second (ft
3
/s) on September 30, 1983.
There are no observed N-aquifer springs issuing directly
from the Navajo Sandstone near the streamow gage. During
base-ow conditions, ow seems to initiate from Moenkopi
Wash alluvium, but it is assumed this ow is supplied by the N
aquifer from below and through the alluvium.
Dinnebito Wash
Dinnebito Wash has a drainage area of 473 mi
2
and
drains some of the middle part of Black Mesa. The streamow
gage is located in a part of the wash that is cut down into
the Navajo Sandstone. Dinnebito Wash is an intermittent
stream with small sections that ow year-round, though
most of the stream is dry much of the year. The streamow
gaging station is in a perennial reach (g. 14). From July
through September, monsoon rain events can result in
large, sediment-laden ows in Dinnebito Wash, although no
high ows were recorded during the summer of 2020. The
maximum instantaneous discharge recorded at the gage was
3,970 ft
3
/s on September 20, 2004. The minimum daily mean
discharge recorded at the gage was 0.05 ft
3
/s on August 16, 23,
and October 1–6, 2002.
There are no observed N-aquifer springs issuing directly
from the Navajo Sandstone near the streamow gage. During
base-ow conditions, ow seems to initiate from Dinnebito
Wash alluvium, but it is assumed this ow is supplied by the N
aquifer from below and through the alluvium.
Polacca Wash
Polacca Wash has a drainage area of 905 mi
2
and
drains a large section of the eastern part of Black Mesa. The
streamow gage is in a part of the wash that is cut down into
the Kayenta Formation. Much of Polacca Wash is ephemeral,
remaining dry except during and after precipitation runoff
events. However, the streamow gage is in a stream reach
that often has ow. During the period of streamow-gage
operation, there has been continuous ow at the gage for most
months of the year with the exception of the summer months,
when the stream is often dry at the gage (g. 14). From
July through September, monsoon rain events can result in
large, sediment-laden ows in Polacca Wash. The maximum
instantaneous discharge recorded at the gage was 2,140 ft
3
/s
on July 30, 2017. Most of the base ow at the Polacca Wash
streamow gage is likely provided by a spring issuing from
the base of the Navajo Sandstone located about 1 mi upstream
from the gage.
Pasture Canyon Spring
Pasture Canyon Spring discharges to a small perennial
stream that begins near the head of Pasture Canyon, a narrow
box canyon carved into the Navajo Sandstone. Base ow
begins near the head of the canyon from a piped spring.
Discharge from that spring accounts for around 20 percent
of the total ow measured at the streamow gage, located
approximately 0.25 mi downstream from the spring. The
remaining base ow measured at the streamow gage comes
from additional springs issuing through the alluvium between
the head of the canyon and the gage. Because the drainage
area is small, very little surface runoff from rainstorms
or snowmelt occurs above the Pasture Canyon Springs
streamow gage (g. 14). In addition, most of the alluvium in
the wash is composed of reworked dune sand, so precipitation
tends to inltrate rather than run off. During the operational
period of record for the gage, the minimum daily mean
discharge recorded was 0.14 ft
3
/s on September 5–8, 2017,
and the maximum instantaneous discharge was 4.96 ft
3
/s on
October 3, 2018.
Table 13. Streamflow-gaging stations used in the Black Mesa monitoring program, their periods of record, and drainage areas.
[—, not determined]
Station name Station number
Date data
collection began
Drainage area
(square miles)
Moenkopi Wash at Moenkopi, Ariz. 09401260 July 1976 1,629
Dinnebito Wash near Sand Springs, Ariz. 09401110 June 1993 473
Polacca Wash near Second Mesa, Ariz. 09400568 April 1994 905
Pasture Canyon Springs near Tuba City, Ariz. 09401265 August 2004 —
Hydrologic Data 35
summer months, some or all groundwater discharge can be taken
up by plants or can evaporate directly to the atmosphere. Rather
than the average ow, the median ow for November, December,
January, and February is used to estimate groundwater discharge
because the median is less affected by occasional winter runoff.
Nonetheless, the median ow for November, December, January,
and February is an estimate of groundwater discharge rather than a
calculation of base-ow groundwater discharge. A more rigorous
and accurate calculation of base-ow would involve detailed
evaluations of streamow hydrographs, ows into and out of bank
storage, gain and loss of streamow as it moves down the stream
channel, and interaction of groundwater in the N aquifer with
groundwater in the shallow alluvial aquifers in the stream valleys.
The median winter ow, however, is useful as a consistent, easily
measurable index for evaluating possible temporal trends in
groundwater discharge.
Surface-Water Base Flow
Trends in the groundwater-discharge component of total ow
at the four streamow-gaging stations were evaluated on the basis
of the median of 120 consecutive daily mean ows for four winter
months (November through February) and used as a surrogate
measure for base ow (g. 15). Median winter streamow is
reported for the year in which the winter season began. For
example, the period from November 2019–February 2020 is
reported as winter 2019. Groundwater discharge was assumed
to be constant throughout the year, and the median winter
ow was assumed to represent constant annual groundwater
discharge. Most ow that occurs during the winter is groundwater
discharge; rainfall and snowmelt runoff are infrequent, and
evapotranspiration is at a minimum during the winter. Not all
groundwater discharge ends up as surface-water ow; during
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
C
1994 1996 1998 2000 2002 2004 2006
2008
1980 1985 1990 1995 2000 2005 20101975
5
4
3
2
1
6
0
1994 1996 1998 2000 2002 2004 2006 2008 2010
2010
20102003 2004 2005 2006 2007 2008 2009
0.50
0.45
0.40
0.35
0.30
0.25
0.20
D
2012
2012
2015
2011
2012
2014
2014
2013
2015
2016
2018
2020
2014 2016
B
2016 2020
2010
20202018
2017 2018 2019 2020
A
NOTE: Kendall’s tau = –0.45 - Slope of Theil-Sen line is significantly different from zero (p<0.05)
NOTE: Kendall’s tau = –0.34 - Slope of Theil-Sen line is significantly different from zero (p<0.05)
NOTE: Kendall’s tau = –0.24 - Slope of Theil-Sen line is not significantly different from zero (p>0.05)
NOTE: Kendall’s tau = –0.32 - Slope of Theil-Sen line is not significantly different from zero (p>0.05)
Discharge, in cubic feet per second
0.0
0.1
0.2
0.3
0.4
0.5
0.6
EXPLANATION
Theil-Sen line (p-value < 0.001)
Median winter discharge
EXPLANATION
Theil-Sen line (p-value = 0.02)
Median winter discharge
EXPLANATION
Theil-Sen line (p-value = 0.11)
Median winter discharge
EXPLANATION
Theil-Sen line (p-value = 0.10)
Median winter discharge
Figure 15. Plots of median winter discharge for November through February for Moenkopi Wash at Moenkopi, Ariz. (09401260)
(A); Dinnebito Wash near Sand Springs, Ariz. (09401110) (B); Polacca Wash near Second Mesa, Ariz. (09400568) (C); and Pasture
Canyon Springs near Tuba City, Ariz. (09401265) (D), Black Mesa area, northeastern Arizona, winter 1977–2020. Median winter
flow is calculated by computing the median flow for 120 consecutive daily mean flows for the winter months of November,
December, January, and February.
36 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
Median winter ows calculated for winter 2019 were 1.72 ft
3
/s for Moenkopi Wash at Moenkopi,
0.26 ft
3
/s for Dinnebito Wash near Sand Springs, 0.13 ft
3
/s for Polacca Wash near Second Mesa,
and 0.25 ft
3
/s for Pasture Canyon Springs near Tuba City (g. 15A–D). The median winter ows
calculated for winter 2020 for Moenkopi Wash at Moenkopi and Pasture Canyon Springs near Tuba
City were 0.82 and 0.34 ft
3
/s, respectively. Median winter ows were not calculated for winter 2020 for
Dinnebito Wash and Polacca Wash because the streamow gages were discontinued in October 2020.
A signicant decreasing trend in median winter ows, calculated using Kendall’s tau (p<0.05), is
indicated at the Moenkopi Wash and Dinnebito Wash streamow-gaging stations, but no signicant
trends are indicated at the Polacca Wash and Pasture Canyon Springs streamow-gaging stations
(g. 15A–D).
Water Chemistry
Between 2020 and 2021, water samples for water-chemistry analyses were collected from four
springs as part of the Black Mesa monitoring program. Field measurements were made, and water
samples were analyzed for major ions; nutrients; and the trace elements arsenic, boron, and iron.
Field measurements were made in accordance with standard USGS protocols as documented in the
USGS National Field Manual for the Collection of Water-Quality Data (U.S. Geological Survey,
variously dated). Field measurements include pH, specic conductance, temperature, dissolved
oxygen, alkalinity, and discharge rates at springs. Field alkalinities were determined using incremental
equivalence. Dissolved constituent samples were ltered through a 0.45-micron pore size lter and
preserved according to sampling and analytical protocols. Laboratory analyses for samples were
done at the USGS National Water Quality Laboratory (NWQL) according to techniques described
in Fishman and Friedman (1989), Fishman (1993), Struzeski and others (1996), and Garbarino and
others (2006).
Quality assurance for this study was maintained using standard USGS training of eld personnel,
use of standard USGS eld protocols (U.S. Geological Survey, variously dated), collection of quality
control (QC) samples, and thorough review of the analytical results. All USGS scientists involved with
this study have participated in the USGS National Field Quality Assurance Program.
A QC sample was collected as part of the water-quality sampling of the Black Mesa monitoring
program in 2020. A eld blank sample was gathered during collection of eld water-quality samples.
The eld blank was processed at Pasture Canyon Spring during the collection of an environmental
sample. Concentrations of analytes in the eld blank were below the NWQL detection limit (table 14).
In past years, water-chemistry samples were systematically collected from as many as 12 different
wells as part of the Black Mesa monitoring program. No wells were sampled in 2020 or 2021 owing to
budgetary constraints. Since 1989, samples have been collected from the same four springs: Moenkopi
School Spring, Burro Spring, Pasture Canyon Spring, and Unnamed Spring near Dennehotso, and
between 2020 and 2021, all four springs were sampled. Long-term data for specic conductance,
dissolved solids, chloride, and sulfate for the wells and springs sampled each year are shown in the
annual reports (table 2). These constituents are monitored on an annual basis because an increase in the
concentration of these constituents in the N aquifer could indicate leakage from the overlying D aquifer.
On average, the concentration of dissolved solids in water from the D aquifer is about 7 times greater
than that of water from the N aquifer, the concentration of chloride ions is about 11 times greater,
and concentration of sulfate ions is about 30 times greater (Eychaner, 1983). Historical data for other
constituents for all the wells and springs in the Black Mesa study area are available from the USGS
National Water Information System Web Interface for water-quality data (https:/ /waterdata .usgs.gov/
nwis/ qw), and they can also be found in monitoring reports cited in the “Previous Investigations”
section of this report and listed in table 2.
Water-Chemistry Data for Springs that Discharge from the N Aquifer
Between 2020 and 2021, water samples were collected from Moenkopi School Spring,
Burro Spring, Pasture Canyon Spring, and Unnamed Spring near Dennehotso (gs. 12, 16).
Geologic maps and eld observations indicate that these four springs discharge water from the
Table 14. Chemical analyses of a field blank water sample processed at Pasture Canyon Spring, Black Mesa area, northeastern Arizona, 2020.
[mg/L, milligrams per liter; <, less than; μg/L, micrograms per liter; °C, degrees Celsius]
Nitrogen,
NO
2
+ NO
3
,
dissolved
(mg/L as N)
Ortho-
phosphate,
dissolved
(mg/L as P)
Calcium,
dissolved
(mg/L as
Ca)
Magnesium,
dissolved
(mg/L as
Mg)
Potassium,
dissolved
(mg/L as K)
Sodium,
dissolved
(mg/L as
Na)
Chloride,
dissolved
(mg/L as
Cl)
Fluoride,
dissolved
(mg/L as
F)
Silica,
dissolved
(mg/L as
SiO
2
)
Sulfate,
dissolved
(mg/L as
SO
4
)
Arsenic,
dissolved
(µg/L as
As)
Boron,
dissolved
(µg/L as
B)
Iron,
dissolved
(µg/L as
Fe)
Dissolved
solids,
residue
at 180°C
(mg/L)
<0.040 <0.004 <0.020 <0.010 <0.30 <0.40 <0.02 <0.01 <0.06 <0.02 <0.10 <2.0 <5.0 <20
Hydrologic Data 37
EXPLANATION
10 5 0 5 10
Chloride
Bicarbonate
Sulfate
Sodium
CATIONS
Milliequivalents per liter
ANIONS
Calcium
Magnesium
Water-chemistry diagram–Shows major chemical
constituents in milliequivalents per liter. The diagram
can be used to compare and characterize types of
water. Number 315 is dissolved-solids concentration,
in milligrams per liter.
315
Spring at which discharge was
measured and water-chemistry
sample was collected
City of Page, Arizona
Pasture Canyon
Spring
W
a
s
h
D
i
n
n
e
b
i
t
o
le
Co
lo
ra
do
Ri
ver
Li
tt
Na
va
jo
Cre
ek
sh
a
W
sh
a
W
Moen
ca
Pol
ac
bi
ai
Or
sh
a
W
La
gu
na
Cre
ek
C
Wash
h
i
e
n
l
kopi
Shonto
Chinle
Ganado
Tuba City
Kayenta
Dennehotso
Betatakin
Keams
Canyon
Red Lake
Kykotsmovi
Page
COAL-LEASE
AREA
Pasture Canyon
Spring
Burro
Spring
Unnamed
Spring
near
Dennehotso
Moenkopi
School
Spring
COCONINO CO.
NAVAJO CO.
NAVAJO CO.
APACHE CO.
37°
111°30'
111°
110°30'
110°
109°30'
36°30'
36°
35°30'
0
0
25 KILOMETERS
25 MILES
Modified from Brown and Eychaner, 1988
Base from U.S. Geological Survey
digital data, 1:100,000, 1980
Lambert Conformal Conic projection
Standard parallels 29°30' and 45°30',
central meridian 96°00'
115
302
152
315
Approximate boundary between confined
and unconfined conditions—
From Brown and Eychaner (1988)
Confined
Unconfined
Confined and unconfined conditions in
the N aquifer within model boundary
Boundary of mathematical model—
From Brown and Eychaner (1988)
Map
area
ARIZONA
Figure 16. Map showing water chemistry and distribution of dissolved solids at springs in the N aquifer, Black Mesa area,
northeastern Arizona, 2020–2021.
Table 14. Chemical analyses of a field blank water sample processed at Pasture Canyon Spring, Black Mesa area, northeastern Arizona, 2020.
[mg/L, milligrams per liter; <, less than; μg/L, micrograms per liter; °C, degrees Celsius]
Nitrogen,
NO
2
+ NO
3
,
dissolved
(mg/L as N)
Ortho-
phosphate,
dissolved
(mg/L as P)
Calcium,
dissolved
(mg/L as
Ca)
Magnesium,
dissolved
(mg/L as
Mg)
Potassium,
dissolved
(mg/L as K)
Sodium,
dissolved
(mg/L as
Na)
Chloride,
dissolved
(mg/L as
Cl)
Fluoride,
dissolved
(mg/L as
F)
Silica,
dissolved
(mg/L as
SiO
2
)
Sulfate,
dissolved
(mg/L as
SO
4
)
Arsenic,
dissolved
(µg/L as
As)
Boron,
dissolved
(µg/L as
B)
Iron,
dissolved
(µg/L as
Fe)
Dissolved
solids,
residue
at 180°C
(mg/L)
<0.040 <0.004 <0.020 <0.010 <0.30 <0.40 <0.02 <0.01 <0.06 <0.02 <0.10 <2.0 <5.0 <20
38 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
unconned part of the N aquifer. At Moenkopi School Spring,
samples were collected from a horizontal metal pipe built
into the hillside to collect water from the spring. At Burro
Spring, samples are usually collected from the end of a pipe
that lls a trough for cattle, but in 2020 and 2021, the samples
were collected directly from the stone spring box. At Pasture
Canyon Spring, samples were collected from a pipe at the end
of a channel that is approximately 50 ft away from the spring.
At Unnamed Spring near Dennehotso, samples were collected
from a pool along the bedrock wall from which the spring
discharges.
Samples from all springs yielded a calcium
bicarbonate-type water, except Burro Spring, which had a
sodium-calcium bicarbonate-type water (g. 16, table 15).
Dissolved solid concentrations measured 302 milligrams per
liter (mg/L) at Moenkopi School Spring, 313 and 315 mg/L
at Burro Spring in 2020 and 2021, respectively, 152 mg/L at
Pasture Canyon Spring, and 115 mg/L at Unnamed Spring
near Dennehotso (tables 15 and 16). Chloride concentration
was highest at Moenkopi School Spring (45.1 mg/L;
tables 15 and 16). Concentration of sulfate also was highest at
Moenkopi School Spring (63.6 mg/L; tables 15 and 16).
Table 15. Physical properties and chemical analyses of water samples from four springs in the Black Mesa area, northeastern
Arizona, 2020–2021.
[Specic cond., specic conductance; μS/cm, microsiemens per centimeter at 25 °C; temp., temperature; °C, degree Celsius; TDS, total dissolved solids; mg/L,
milligrams per liter; Ca, calcium; diss., dissolved; Mg, magnesium; K, potassium; Na, sodium; Cl, chloride; F, uoride; SiO
2
, silica; SO
4
, sulfate; N, nitrate +
nitrite; Fe, iron; μg/L, micrograms per liter; As, arsenic; B, boron; <, less than]
Date of
samples
pH, field
(units)
Specific
cond., field
(µS/cm)
Temp.,
field (°C)
TDS,
residue
at 180 °C
(mg/L)
Ca, diss.
(mg/L)
Mg, diss.
(mg/L)
K, diss.
(mg/L)
Na, diss.
(mg/L)
Alkalinity,
field, diss.
(mg/L as
CaCO
3
)
354156110413701 Burro Spring (6M-31)
11/02/20 7.3 496 14.2 313
a
53.8 3.68 0.35 56.0 175
12/21/21 7.4 489 5.4 315 52.7 3.73 <0.30 55.2 173
360632111131101 Moenkopi School Spring (3GS-7-6)
12/22/21 7.3 480 18.6 302 47.0 10.5 1.61 36.9 102
361021111115901 Pasture Canyon Spring (3A-5)
10/06/20 7.7 243 16.8 152 30.9 4.50 1.58 12.7 78.3
364656109425400 Unnamed Spring near Dennehotso (8A-224)
10/13/20 8.1 197 11.8 115 30.4 4.43 1.11 4.84 76.7
a
Dissolved solids from sum of constituents
Table 15. Physical properties and chemical analyses of water samples from four springs in the Black Mesa area, northeastern
Arizona, 2020–2021.—Continued
[Specic cond., specic conductance; μS/cm, microsiemens per centimeter at 25 °C; temp., temperature; °C, degree Celsius; TDS, total dissolved solids; mg/L,
milligrams per liter; Ca, calcium; diss., dissolved; Mg, magnesium; K, potassium; Na, sodium; Cl, chloride; F, uoride; SiO
2
, silica; SO
4
, sulfate; N, nitrate +
nitrite; Fe, iron; μg/L, micrograms per liter; As, arsenic; B, boron; <, less than]
Bicarbonate,
field, diss.
(mg/L)
Carbonate,
field, diss.
(mg/L)
Cl, diss.
(mg/L)
F, diss.
(mg/L)
SiO
2
,
diss.
(mg/L)
SO
4
,
diss.
(mg/L)
N, diss.
(mg/L)
Ortho-
phosphate,
diss. (mg/L
as P)
Fe, diss.
(µg/L)
As, diss.
(µg/L)
B, diss.
(µg/L)
354156110413701 Burro Spring (6M-31)
213 0.2 20.7 0.36 16.2 56.4 <0.040 <0.004 59.3 0.94 76
210 0.9 21.7 0.35 14.6 58.0 <0.040 <0.004 10.3 0.58 73
360632111131101 Moenkopi School Spring (3GS-7-6)
124 0.1 45.1 0.17 14.4 63.6 3.31 0.005 <5.0 2.3 59
361021111115901 Pasture Canyon Spring (3A-5)
95.2 0.2 4.88 0.16 9.88 16.5 4.44 0.020 <5.0 1.9 36
364656109425400 Unnamed Spring near Dennehotso (8A-224)
92.8 0.4 2.90 0.12 12.8 8.53 2.00 0.023 <5.0 2.5 18
Hydrologic Data 39
Year
Specific
conductance,
field (µS/cm)
Dissolved
solids,
residue at
180 °C (mg/L)
Chloride,
dissolved
(mg/L as Cl)
Sulfate,
dissolved
(mg/L as SO
4
)
Burro Spring
1989 485 308 22.0 59
1990 545
a
347 23.0 65.0
1993 595 368 30.0 85.0
1994 597
a
368 26.0 80.0
1996 525 324 23.0 62.0
1997 511
a
332 26.0 75.0
1998 504 346 24.6 70.4
1999 545 346 24.8 69.2
2001 480 348 23.6 67.8
2002 591 374 30.6 77.0
2003 612 374 30.5 81.1
2004 558 337 24.9 63.6
2005 558 357 25.8 68.9
2006 576 359 25.0 68.2
2009 577 372 25.7 72.5
2010 583 355 25.9 71.5
2011 560 353 25.7 69.5
2012 553 330 23.1 64.7
2013 560 350 24.4 67.7
2014 549 360 22.8 64.6
2016 544 318 22.2 61.7
2017 536 329 22.0 59.5
2018 532 330 21.6 58.7
2019 522 332 23.7 63.0
2020 496 313
b
20.7 56.4
2021 489 315 21.7 58.0
Pasture Canyon Spring
1948 227
a
(
c
) 6.0 13
1982 240 — 5.1 18.0
1986 257 — 5.4 19.0
1988 232 146 5.3 18.0
1992 235 168 7.10 17.0
1993 242 134 5.3 17.0
1995 235 152 4.80 14.0
1996 238 130 4.70 15.0
1997 232 143 5.27 16.9
1998 232 147 5.12 16.2
1999 235 142 5.06 14.2
2001 236 140 5.06 17.0
2002 243
d
143 5.14 16.5
2003 236 151 5.09 16.1
2004 248 150 5.50 16.4
2005 250 149 5.07 16.3
2008 240 149 5.01 18.3
2009 241 160 5.10 18.6
2010 314 157 5.25 17.9
Year
Specific
conductance,
field (µS/cm)
Dissolved
solids,
residue at
180 °C (mg/L)
Chloride,
dissolved
(mg/L as Cl)
Sulfate,
dissolved
(mg/L as SO
4
)
Pasture Canyon Spring—Continued
2011 236 146 5.47 18.5
2012 248 142 5.20 17.5
2013 245 145 5.16 17.7
2014 249 149 5.03 17.2
2016 252 155 5.09 17.2
2017 236 151 5.07 17.1
2018 238 145 5.04 16.9
2019 224 148 5.02 16.8
2020 243 152 4.88 16.5
Moenkopi School Spring
1952 222 — 6 —
1987 270 161 12.0 19.0
1988 270 155 12.0 19.0
1991 297 157 14.0 20.0
1993 313 204 17.0 27.0
1994 305 182 17.0 23.0
1995 314 206 18.0 22.0
1996 332 196 19.0 26.0
1997 305
a
185 17.8 23.8
1998 296 188 17.6 23.7
1999 305 192 18.7 25.6
2001 313 194 18.3 25.5
2002 316 191 18.3 23.1
2003 344 197 18.6 23.4
2004 349 196 19.1 21.3
2005 349 212 23.3 29.6
2006 387 232 27.2 34.2
2007 405 253
e
30.6 39.9
2008 390 230 28.3 37.6
2009 381 240 27.0 35.6
2010 480 217 26.2 33.4
2011 374 216 28.5 36.2
2012 382 218 27.5 33.3
2013 370 220 27.2 33.3
2014 382 226 28.5 34.6
2016 427 244 34.6 43.8
2017 424 266 35.5 44.7
2018 434 260 36.9 45.9
2019 428 255 39.3 49.1
2021 480 302 45.1 63.6
Unnamed Spring near Dennehotso
1984 195 112 2.8 7.1
1987 178 109
c
3.4 7.5
1992 178 108 3.60 7.30
1993 184 100 3.2 8.00
1995 184 124 2.60 5.70
Table 16. Specific conductance and concentrations of selected chemical constituents in N-aquifer water samples from four springs in
the Black Mesa area, northeastern Arizona, 1948–2021.
[μS/cm, microsiemens per centimeter at 25°C; °C, degrees Celsius; mg/L, milligrams per liter; —, no data]
40 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
Chemical constituents analyzed from the four springs
were compared to the U.S. Environmental Protection Agency
(EPA) primary and secondary drinking water standards (EPA,
2023a, b). Maximum contaminant levels (MCLs), which are
the primary regulations, are legally enforceable standards that
apply to public water systems. They protect drinking-water
quality by limiting the levels of specic contaminants that
can adversely affect public health. Secondary maximum
contaminant levels (SMCLs) provide guidelines for the control
of contaminants that may cause cosmetic effects (such as skin
or tooth discoloration) or aesthetic effects (such as taste, odor,
or color) in drinking water. The EPA recommends compliance
with SMCLs for public water systems; however, compliance
is not enforced. Concentrations of all the analyzed constituents
in samples from all four springs were less than current EPA
MCLs and SMCLs.
Concentrations of dissolved solids, chloride, and sulfate
in water from Moenkopi School Spring show signicant
increasing trends (p<0.05) (table 16, g. 17). Concentrations
of the same constituents from Burro Spring, Pasture Canyon
Spring, and Unnamed Spring near Dennehotso either showed
no signicant trends or showed decreasing trends (table 16,
g. 17). At Burro Spring, no signicant trend was present
in dissolved solids, while both chloride and sulfate had a
decreasing trend. At Pasture Canyon Spring, both dissolved
solids and sulfate showed no signicant trend while chloride
showed a decreasing trend. The magnitude of the change
in chloride concentrations at Pasture Canyon Spring is
small, and, because of the scaling used on the y axis in
gure 17B to allow plotting results from other springs with
higher concentrations of chloride, the trend is difcult to
see. Signicant trends were not detected in any of the three
constituents at Unnamed Spring near Dennehotso. However,
in 2010, 2011, and 2012, Unnamed Spring near Dennehotso
showed an increase in dissolved solids concentrations; this
trend may be a result of sampling from an alternate sample
location. Since then, Unnamed Spring near Dennehotso has
been sampled from the same location that was used prior to
2010, and the results for dissolved-solids analysis returned to
levels observed prior to 2010 (g. 17).
Year
Specific
conductance,
field (µS/cm)
Dissolved
solids,
residue at
180 °C (mg/L)
Chloride,
dissolved
(mg/L as Cl)
Sulfate,
dissolved
(mg/L as SO
4
)
Unnamed Spring near Dennehotso—Continued
1996 189 112 2.80 8.20
1997 170
a
98 2.40 6.10
1998 179 116 2.43 5.36
1999 184 110 2.76 6.30
2001 176 116 2.61 5.96
2002 183 104 2.67 7.38
2003 180 118 2.95 7.16
2004 170 117 2.72 5.05
2005 194 114 2.65 8.67
2010 259 155 9.38 15.5
2011 292 172 14.5 24.1
2012 298 179 13.5 21.9
2013 196 127 3.06 8.24
2014 160 122 2.68 7.40
2016 197 116 3.21 9.46
2018 157 108 2.33 5.39
2019 156 105 2.39 6.02
2020 197 115 2.90 8.53
a
Value is different in Black Mesa monitoring reports before 2000. Earlier
reports showed values determined by laboratory analysis
b
Value determined by the sum of constituents
c
Value is different in Black Mesa monitoring reports before 2000. Earlier
reports showed values determined by the sum of constituents
d
Value was measured in the laboratory, not in the eld
e
Value is different in Black Mesa monitoring reports prior to this report.
Earlier reports showed values determined by the sum of constituents
Table 16.—Continued
Hydrologic Data 41
Moenkopi School Spring Kendall’s tau = 0.73 - Slope of Theil-Sen line is significantly different from zero (p<0.05)
Pasture Canyon Spring Kendall’s tau = 0.18 - Slope of Theil-Sen line is not significantly different from zero (p>0.05)
Burro Spring Kendall’s tau = -0.20 - Slope of Theil-Sen line is not significantly different from zero (p>0.05)
Unnamed Spring near Dennehotso Kendall’s tau = 0.22 - Slope of Theil-Sen line is not significantly different from zero (p>0.05)
Dissolved solids, in milligrams per liter
Moenkopi School Spring
Kendall’s tau = 0.85
- Slope of
Theil-Sen
line is significantly different from zero (p<0.05)
Pasture Canyon Spring
Kendall’s tau = –0.28
- Slope of
Theil-Sen
line is significantly different from zero (p<0.05)
Burro Spring
Kendall’s tau = –0.35
- Slope of
Theil-Sen
line is significantly different from zero (p<0.05)
Unnamed Spring near Dennehotso
Kendall’s tau = –0.03
- Slope of
Theil-Sen
line is not significantly different from zero (p>0.05)
Moenkopi School Spring
Kendall’s tau = 0.70
- Slope of
Theil-Sen
line is significantly different from zero (p<0.05)
Pasture Canyon Spring
Kendall’s tau = 0.01
- Slope of
Theil-Sen
line is not significantly different from zero (p>0.05)
Burro Spring
Kendall’s tau = –0.44
- Slope of
Theil-Sen
line is significantly different from zero (p<0.05)
Unnamed Spring near Dennehotso
Kendall’s tau = 0.18
- Slope of
Theil-Sen
line is not significantly different from zero (p>0.05)
0
50
100
150
200
250
300
350
400
0
5
10
15
20
25
30
35
Chloride concentrations,
in milligrams per liter
0
10
20
30
40
50
60
70
80
90
Sulfate concentrations,
in milligrams per liter
1985 1990 1995 2000 2005 20101980
2015 2025
50
A
B
2020
C
45
40
EXPLANATION
Burro Spring
Moenkopi School Spring
Pasture Canyon Spring
Unnamed Spring near Dennehotso
Theil-Sen line
Analyte concentration
Theil-Sen line
Analyte concentration
Theil-Sen line
Analyte concentration
Theil-Sen line
Analyte concentration
Figure 17. Plots of concentrations of dissolved solids (A), chloride (B), and sulfate
(C) for water samples from Moenkopi School Spring, Burro Spring, Pasture Canyon
Spring, and Unnamed Spring near Dennehotso, which discharge from the N aquifer,
Black Mesa area, northeastern Arizona, 1982–2021.
42 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021
Summary
The Navajo (N) aquifer is extensive and serves as the
primary source of groundwater for industrial and municipal
users in the Black Mesa area of northeastern Arizona.
Availability of quality water is an important issue in the
Black Mesa area because of past industrial use and continued
municipal use, a growing population, and limited precipitation.
This report presents results of groundwater, surface-water,
and water-chemistry monitoring in the Black Mesa area from
January 2020 to December 2021, and, additionally, uses
streamow statistics from November and December 2019.
These monitoring data are compared to historical data from
the 1950s through December 2021.
In 2021, total groundwater withdrawals were about
2,570 acre-feet (acre-ft), industrial withdrawals were about
160 acre-ft, and municipal withdrawals were about 2,410
acre-ft. From the prestress period (before 1965) to 2021,
water levels in the unconned areas of the N aquifer had a
median change of −0.4 feet (ft), and the changes ranged from
−42.4 ft to +8.4 ft. Water levels in the conned area of the
N aquifer had a median change of −25.9 ft, and the changes
ranged from −133.7 ft to +17.3 ft. However, the well in the
conned area that has shown the largest declines in water
level since predevelopment (Keams Canyon PM2) was not
measured in 2021. In 2020, it showed a 181.4 ft decline since
predevelopment.
Discharge has been measured intermittently at Moenkopi
School Spring, Pasture Canyon Spring, Burro Spring, and
Unnamed Spring near Dennehotso. For the period of record,
discharge at Moenkopi School Spring and Unnamed Spring
near Dennehotso has uctuated, and the data indicate a
decreasing trend in discharge for both springs; however,
no trend is apparent for either Burro Spring or Pasture
Canyon Spring.
Streamow was measured continuously during calendar
years 2020 and 2021 at the Moenkopi Wash at Moenkopi and
Pasture Canyon Springs near Tuba City streamow-gaging
stations and was measured continuously through September
30, 2020, at the Dinnebito Wash near sand springs and Polacca
Wash near Second Mesa streamow-gaging stations. Median
ows for November through February of each winter are used
as an indicator of groundwater discharge to those streams. For
the period of record at Moenkopi Wash and Dinnebito Wash,
winter ows indicate a decreasing trend in discharge. Winter
ows at Polacca Wash and Pasture Canyon Springs have
uctuated but show neither a signicant increase nor decrease.
Between 2020 and 2021, water samples were collected
at four springs and were analyzed for selected chemical
constituents. A eld blank was collected at Pasture Canyon
Spring during the collection of an environmental sample.
Concentrations of analytes in the eld blank were below
the National Water Quality Laboratory method detection
limit. Dissolved-solids concentrations in water samples
from Moenkopi School Spring, Burro Spring, Pasture
Canyon Spring, and Unnamed Spring near Dennehotso
were 302 milligrams per liter (mg/L), 315 mg/L, 152 mg/L,
and 115 mg/L, respectively. From the mid-1980s to 2021,
long-term data from Moenkopi School Spring indicate
increasing concentrations of dissolved solids, chloride, and
sulfate. Concentrations of the same constituents from Burro
Spring, Pasture Canyon Spring, and Unnamed Spring near
Dennehotso either showed no signicant trends or showed
decreasing trends.
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Publishing support provided by the Moffett Field Publishing
Service Center
Manuscript approved for publication March 15, 2024
Edited by Phil Frederick
Illustration support by Cory Hurd and Kimber Petersen
Layout by Cory Hurd
