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Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021

Jon P. Mason, W.M. Aubrey, B. Beitler, W.T. Parry, M.A. Chan, B. Beitler · U.S. Geological Survey

USGS Publications · Papers · License: Public Domain

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usgs, geological survey, united states, science, government publication, usgs open-file report, 2024, 1019, groundwater, surface, water, chemistry, data, black, mesa, area, northeastern, arizona, 2019, 2021

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

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit https://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov/. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. 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

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

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

Conversion Factors U.S. customary units to International System of Units

Multiply

To obtain

Length foot (ft)

0.3048

meter (m)

mile (mi)

1.609

kilometer (km)

Area square mile (mi2)

259.0

square mile (mi2)

hectare (ha)

2.590

square kilometer (km2)

Volume acre-foot (acre-ft)

1,233

acre-foot (acre-ft)

cubic meter (m3)

0.001233 cubic hectometer (hm3) Flow rate

acre-foot per year (acre-ft/yr)

1,233

cubic meter per year (m3/yr)

acre-foot per year (acre-ft/yr)

0.001233 cubic hectometer per year (hm3/yr)

cubic foot per second (ft3/s)

0.02832

cubic meter per second (m3/s)

gallon per minute (gal/min)

0.06309

liter per second (L/s)

International System of Units to U.S. customary units

Multiply

To obtain

Length meter (m)

3.281

foot (ft)

kilometer (km)

0.6214

mile (mi)

meter (m)

1.094

yard (yd)

hectare (ha)

0.003861

square mile (mi2)

square kilometer (km2)

0.3861

square mile (mi2)

Area

Volume cubic meter (m3) cubic hectometer (hm3)

0.0008107

acre-foot (acre-ft)

810.7

acre-foot (acre-ft)

Flow rate cubic meter per year (m3/yr)

0.000811

acre-foot per year (acre-ft/yr)

cubic hectometer per year (hm3/yr)

811.03

acre-foot per year (acre-ft/yr)

cubic meter per second (m3/s)

35.31

cubic foot per second (ft3/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

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 streamflow 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 unconfined 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 confined area of the aquifer when compared to the prestress period. The median change for the confined area of the aquifer was −25.9 ft, with changes across all 12 wells ranging from +17.3 ft to −133.7 ft. Spring flow was measured at four springs between 2020 and 2021. Flow fluctuated during the period of record for Burro Spring and Pasture Canyon Spring, but a decreasing trend was statistically significant (p<0.05) at Moenkopi School Spring and Unnamed

Spring near Dennehotso, Arizona. Discharge at Burro Spring has remained relatively constant since it was first measured in the 1980s, and discharge at Pasture Canyon Spring has fluctuated for the period of record. Continuous records of surface-water discharge in the Black Mesa area were collected from streamflow-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 flows (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 flows 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 significantly (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 (mi2) Black Mesa study area is enclosed fully within the Navajo Nation and partially within the Hopi Reservation in northeastern Arizona (fig. 1). It contains diverse topography that includes flat plains, elevated mesas, and incised drainages (fig. 1). Black Mesa, a topographic high at the center of the study area, encompasses about 2,000 mi2.

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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.

Navajo Nation Litt le C ol o rad

264

Hopi Buttes

Flagstaff

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Yuma

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Colorado

35°30'

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Mishongnovi Keams Shungopavi Canyon Second Mesa

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Low Mountain

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Hopi Black Mesa Tribal Lands

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Bacavi

Map area

Rive r

Chinle Valley

Kitsillie Chapter House

Wash

Rocky Ridge

Hotevilla

Boundary of Black Mesa Boundary of study area—Based on the mathematical boundary of groundwater model from Brown and Eychaner (1988)

Chinle

Blue Canyon

Moenkopi 264 Plateau

Rough Rock

Forest Lake

160 £ ¤

36°00’

Area of Hopi Tribal Lands within Navajo Nation

Chilchinbito

pi ko en o M

Coal Mine Canyon

EXPLANATION

COAL-LEASE AREA

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Shonto Junction

Red Lake

Moenkopi

Dennehotso

Wa lk e r

Colorado

191 £ ¤

all eV

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NAVAJO COUNTY APACHE COUNTY

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36°30'

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Shonto Tsegi Plateau Betatakin

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Tuba City

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Page

110°00’

Cr ee k

110°30'

n Me sa Orga n Ro ck M onoc line

111°00’

Modified from Brown and Eychaner, 1988

25 KILOMETERS

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).

2 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021

111°30' 37°00’

Introduction 3

Volcanic rock

Water bearing in places

TERTIARY

Volcanic rock ►

Bidahochi Formation

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 field, 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

►

Yale Point Sandstone

EXPLANATION

Wepo Formation

T aquifer

Water bearing

CRETACEOUS

Mesa Verde Group

QUATERNARY and TERTIARY

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 (fig. 2). Shallow aquifers composed of surficial 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 significant quantities in the

Toreva Sandstone

Mancos Shale Dakota Sandstone Morrison Formation D aquifer

JURASSIC

San Rafael Entrada Sandstone Group Carmel Formation

Navajo Sandstone

Glen Canyon Group

N aquifer Kayenta Formation Moenave Formation

Wingate Sandstone?

???

Moenkopi Formation

TRIASSIC

Chinle Formation

Shinarump Member

Kaibab Limestone

Supai Formation or Group

C Aquifer

PERMIAN

Coconino Sandstone

Modified from Harshbarger and others, 1966

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 (fig. 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 confined under most of Black Mesa, and the overlying stratigraphy limits recharge to this part of the aquifer. The N aquifer is unconfined in most areas surrounding Black Mesa, and most recharge occurs where the Navajo Sandstone is exposed in the area near Shonto, Ariz. (fig. 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 (fig. 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 (fig. 1). Most reaches of these streams are ephemeral, flowing only

in response to runoff from precipitation events, but a few short reaches flow 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 streamflow-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 Table 1. Withdrawals from the N aquifer, Black Mesa area, northeastern Arizona, 1965–2021. [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 confined area of the aquifer]

Calendar Year

Industriala

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

0 0 0 100 40 740 1,900 3,680 3,520 3,830 3,500 4,180 4,090 3,000 3,500 3,540 4,010 4,740 4,460 4,170 2,520 4,480 3,830 4,090 3,450 3,430 4,020 3,820 3,700 4,080 4,340 4,010 4,130 4,030 4,210 4,490

Municipalb,c Total Confined Unconfined withdrawals 50 20 70 110 30 140 120 50 170 150 100 350 200 100 340 280 150 1,170 340 150 2,390 370 250 4,300 530 300 4,350 580 360 4,770 600 510 4,610 690 640 5,510 750 730 5,570 830 930 4,760 860 930 5,290 910 880 5,330 960 1,000 5,970 870 960 6,570 1,360 1,280 7,100 1,070 1,400 6,640 1,040 1,160 4,720 970 1,260 6,710 1,130 1,280 6,240 1,250 1,310 6,650 1,070 1,400 5,920 1,170 1,210 5,810 1,140 1,300 6,460 1,180 1,410 6,410 1,250 1,570 6,520 1,210 1,600 6,890 1,220 1,510 7,070 1,380 1,650 7,040 1,380 1,580 7,090 1,440 1,590 7,060 1,420 1,480 7,110 1,610 1,640 7,740

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.water.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).

Calendar Year 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021

Industriala 4,530 4,640 4,450 4,370 4,480 1,200 1,170 1,210 1,390 1,170 1,390 1,370 1,460 1,580 1,340 1,090 1,110 1,170 670 200 160

Municipalb,c Total Confined Unconfined withdrawals 1,490 1,660 7,680 1,500 1,860 8,000 1,350 1,440 7,240 1,240 1,600 7,210 1,280 1,570 7,330 1,300d 1,600d 4,100d 1,460 1,640 4,270 1,430e,f 1,560e 4,200f 1,440 1,400 4,230 1,450d 1,420 4,040d 1,460d 1,630 4,480d 1,380d 1,260 4,010d d d 1,410 1,110 3,980d d d 1,280 1,310 4,170d d d 1,370 1,260 3,970d d d 1,380 1,070 3,540d d 1,330 1,270 3,710d d 1,370 1,130 3,670d d d 1,340 1,060 3,070d d d 1,370 1,110 2,680d d d 1,320 1,090 2,570d

aMetered pumpage from the confined part of the aquifer by Peabody Western Coal Company bDoes not include withdrawals from the wells equipped with windmills cIncludes 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 dMeter data were incomplete; therefore, municipal withdrawals are estmated, and total withdrawal uses an estimation in the calculation eConfined and unconfined totals were reversed in previous reports fConfined withdrawals are about 90 acre-feet greater than previously reported

Many interpretive studies have investigated the hydrology of the Black Mesa area. Cooley and others (1969) made the first comprehensive evaluation of the regional hydrogeology of the Black Mesa area. Eychaner (1983) developed a two-dimensional numerical model of groundwater flow in the N aquifer. Brown and Eychaner (1988) recalibrated Eychaner’s earlier model by using a finer 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.

[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, Water-Resources Investigations Report northeastern Arizona—2000–2001, and performance and sensitivity of the 02–4211 1988 USGS numerical model of the N aquifer

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

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.

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

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

USGS report type and number

Introduction 7

8 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021 Kister and Hatchett (1963) made the first 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 flow 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 confining 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 influences the movement and chemistry of surface water and groundwater.

Physiography

Mesa. In these areas, the aquifer is generally unconfined. 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 (fig. 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 confined portion of the N aquifer occurs where the aquifer units are deeply buried beneath Black Mesa. The paths of stream channels are also influenced by physiography. Geologic structural folds, joint patterns, rock types, and topography all affect the flow of surface water in the study area. Major streams of the study area are shown in figure 1. The surface topography of Black Mesa slopes downhill from northeast to southwest. Likewise, the major streams that drain Black Mesa flow from northeast to southwest toward the Little Colorado River.

Climate The climate in most of the Black Mesa area is broadly classified by Hendricks (1985) as steppe, which is characterized by limited amounts of precipitation. Much of the precipitation in steppe regions evaporates before it can infiltrate 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 classified by Hendricks (1985) as desert. This classification signifies even less annual rainfall and indicates a vegetative cover consisting mostly of creosote bush, cacti, and sagebrush.

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 (fig. 1). Black Mesa is the remnant of a large sedimentary basin that has undergone significant 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 Figure 3. Aerial photograph showing the Organ Rock Monocline and folding strata of Skeleton large extent around the periphery of Black Mesa near Kayenta, Arizona. Photograph by Jodi Norris, used with permission.

Description of Study Area 9

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Map area

Annual precipitation, in inches 4.1 to 6.0 6.1 to 8.0 8.1 to 10.0 10.1 to 12.0

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Colorado

EXPLANATION

Keams Canyon

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Shungopavi Second Mesa

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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.

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Rocky Ridge

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in the lower elevation regions around the mesa to more than 16 in at the highest elevations on the mesa (fig. 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

Cr ee

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)

Black Mesa A R I Z O N A

12.1 to 14.0 14.1 to 16.0 16.1 to 18.0 Boundary of Black Mesa

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 significant 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 (fig. 2) used in the current and previous Black Mesa monitoring reports was modified 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 figure 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 (fig. 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 flat 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 (fig. 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 (fig. 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 (fig. 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 fluvial deposits (Blakey and Ranney, 2008) that now compose the sandstone units of the N aquifer. Where the N aquifer is confined it is capped by the Carmel Formation (fig. 2), which is considered part of the San Rafael Group; the Carmel Formation is discussed in this section because it both confines 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 (fig. 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 fluvial, lacustrine, and eolian subenvironments. They described trough cross-bedded sands deposited on floodplains by ephemeral streams flowing north-northwest (relative to modern geographic position) and silt deposited by sheet flow across broad interchannel flats. Tanner and Lucas (2007) further described deposits from perennial lakes that formed on terminal floodplains 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, flat-bedded, and crossbedded fine- to coarse-grained fluvial 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 (figs. 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 insufficient 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 flat-bedded fluvial 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 fineto very fine-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 flowing 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 (fig. 2). According to Harshbarger and others (1957), it is an eolian deposit composed of sediments derived in part from fluvial deposits of the underlying Kayenta Formation. Beitler and others (2005, p. 551) described the Navajo Sandstone as a “subrounded, fine- 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-stratification 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 (fig. 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 fluvial, eolian, coastal sabkha, and marine. Where present in the Black Mesa area, the Carmel Formation overlies the Navajo Sandstone, forming a confining layer when the Navajo is fully saturated. The Carmel Formation is absent in most of the study area where the N aquifer is unconfined. 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 (fig. 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 first 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 difficult to differentiate from it but clarified 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 (fig. 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 fluvial, consisting of alternating flood-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 (fig. 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 (fig. 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 identified 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 (fig. 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 (fig. 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 fluvial 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 fine-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 fluvial 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 mi2 (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 significant 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 field, 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, streamflow 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 outfitted 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 field. 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-identification 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). Streamflow 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 streamflow 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 streamflow 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 coefficient 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 significance level of 0.05 was chosen to determine whether the result of the test for importance of Kendall’s tau correlation coefficient was statistically significant. A two-sided p-value that was less than or equal to 0.05 indicated that there was a statistically significant correlation in the data, and

the null hypothesis would be rejected. If a significant 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 significant correlation between time and concentration, and the null hypothesis would be accepted. In addition, the Theil-Sen slope estimator was calculated and plotted for streamflow 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 confined area, (2) municipal withdrawals from the confined area, and (3) municipal withdrawals from the unconfined areas. There are no industrial withdrawals from the unconfined areas within the study area. The industrial category includes eight wells in the PWCC industrial well field 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 confined 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 outfitted 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 5a

4T-519

—

360217111122601

Tuba City

3K-325

360614110130801

Piñon PM6

—

360734111144801

Tuba City

3T-333

360904111140501

Tuba City NTUA 1Rb

—

360918111080701

Tuba City Rare Metals 2

—

360927111142401

Tuba City NTUA 3Rc

—

360953111142401

Tuba City NTUA 4

3T-546

361225110240701

BM observation well 6a

—

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 1a

8T-537

363013109584901

Sweetwater Mesa

8K-443

363103109445201

Rough Rock

9Y-95

363143110355001

BM observation well 4a

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 2a

8T-538

364034110240001

Marsh Pass

8T-522

364226110171701

Kayenta West

8T-541

364248109514601

Northeast Rough Rock

8A-180

364338110154601

BM observation well 3a

8T-500

aWell with continuous water-level recorder bWell replaced Tuba City NTUA 1 (360904111140201) in 2018 cWell replaced Tuba City NTUA 3 (360924111142201) in 2018

[Well systems include one or more wells. Withdrawals, in acre-feet, are from flowmeter 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

Chilchinbito Dennehotso Hopi High School Hotevilla Kayenta Keams Canyon Low Mountain Piñon Red Lake Rocky Ridge Rough Rock Second Mesa Shonto Tuba City Chilchinbito Dennehotso Forest Lake Hard Rock Kayenta Kits’iili Piñon Red Lake Rough Rock Shonto Shonto Junction Tuba City Mine Well Field Bacavi Hopi Civic Center Hopi Cultural Center Kykotsmovi Mishongnovi Moenkopi Polacca Shipaulovi Shungopovi

BIA BIA BIA BIA BIA BIA BIA BIA BIA BIA BIA BIA BIA BIA NTUA NTUA NTUA NTUA NTUA NTUA NTUA NTUA NTUA NTUA NTUA NTUA PWCC Hopi Hopi Hopi Hopi Hopi Hopi Hopi Hopi Hopi

USGS/BIA USGS/BIA USGS/BIA USGS/BIA USGS/BIA USGS/BIA USGS/BIA USGS/BIA USGS/BIA USGS/BIA USGS/BIA USGS/BIA USGS/BIA USGS/BIA USGS/NTUA USGS/NTUA USGS/NTUA USGS/NTUA USGS/NTUA USGS/NTUA USGS/NTUA USGS/NTUA USGS/NTUA USGS/NTUA USGS/NTUA USGS/NTUA PWCC USGS/Hopi USGS/Hopi USGS/Hopi USGS/Hopi USGS/Hopi USGS/Hopi USGS/Hopi USGS/Hopi USGS/Hopi

2020 withdrawalsa Confined aquifer Unconfined aquifer 4.1 — — 4.8 11.3 — 22.4 — 15.1 — 51.4 — 0b — 0b — — 1.9 3.2 — 9.9 — 5.7 — — 93.7 — 65.1 74.8 — — 43.9 16.7 — 47.4 — 364.1 — 19.2 — 389.8 — — 45.7 49.8 — — 22.4 — 71.5 — 696.5 203.8 — 18.1 — 0.9 — 1.5 — 62.6 — 4.0 — — 60.6 145.8 — 22.4 — 29.5 —

2021 withdrawalsa Confined aquifer Unconfined aquifer 4.1 — — 4.8 11.3 — 22.4 — 15.1 — 51.4 — 0b — 0b — — 1.9 3.2 — 9.9 — 5.7 — — 93.7 — 65.1 71.9 — — 42.4 18.0 — 44.8 — 330.2 — 19.4 — 377.5 — — 48.7 48.6 — — 26.4 — 69.7 — 674.0 161.6 — 18.1 — 0.9 — 1.5 — 62.6 — 4.0 — — 60.6 145.8 — 22.4 — 29.5 —

aNo 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 bWell taken out of service

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.

Hydrologic Data 17 while withdrawals from the unconfined 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 reflected by a decrease in total annual withdrawals of about 44 percent from 2005 (tables 1, 5; fig. 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; fig. 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

1965–2005

218,300

138,100

80,200

2006–2021

60,690

17,680

43,010

2020

2,680

200

2,480

2021

2,570

160

2,410

9,000

EXPLANATION 8,000

Withdrawals Industrial Municipal

7,000

Total withdrawals

5,000

4,000

3,000

2,000

1,000

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

Withdrawal, in acre-feet

6,000

Year

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

111°

C re e

Dennehotso (47.2*)

La gu n Kayenta (345.3*)

Shonto (120.1*)

COAL-LEASE AREA

Kits’iili (19.4) Forest Lake (18.0)

n ko pi as

M oe

Rough Rock (58.4*)

Wash

Tuba City (739.1*)

C h in l e

Shonto Junction (69.7*) Red Lake (50.6*)

Chilchinbito (76.0*)

PWCC (161.6)

30'

Cre

NAVAJO CO.

109°30'

110°

NAVAJO CO.

Na va

COCONINO CO.

Page

110° 30'

APACHE CO.

111°30' 37°

Moenkopi (60.6*)

Rocky Ridge (3.2*)

Chinle

Piñon (377.5)

Hard Rock (44.8)

36° Low Mountain (0)

Bacavi (18.1*)

Hotevilla (22.4*)

Li tt l e

Ganado

ai b

Was

C o lo ra o

bi t

r ne

Ri ve

35°30'

s Shipaulovi (22.4*) W Hopi High Kykotsmovi (62.6*) Polacca (145.8*) School (11.3*) Hopi Civic Center (0.9*) Hopi Cultural Center (1.5*) Keams Mishongnovi (4.0*) Shungopavi (29.5*) Canyon (51.4*) Second Mesa (5.7*)

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'

Modified from Brown and Eychaner, 1988

25 MILES

Map area

25 KILOMETERS

ARIZONA

EXPLANATION Confined and unconfined conditions in the N aquifer within model boundary Confined Unconfined Approximate boundary between confined and unconfined conditions— From Brown and Eychaner (1988) Boundary of mathematical model— From Brown and Eychaner (1988)

Well-system owner

Piñon (377.5) Withdrawals from the N aquifer—

Bureau of Indian Affairs Navajo Tribal Utility Authority Hopi Tribe Peabody Western Coal Company (PWCC)

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

City of Page, 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 confined conditions in the central part of the study area and under unconfined or water-table conditions around the periphery (fig. 7). Because of the different ways groundwater is released from storage, confined and unconfined aquifers respond dissimilarly to groundwater withdrawal. When the same volume of water is withdrawn from both confined and unconfined aquifers by pumping, the water-level decline in wells within the confined aquifer will usually be much greater than the decline seen in wells within the unconfined aquifer. This is one reason water levels have generally declined more in wells screened in the confined portion of the N aquifer than in the unconfined portion within the monitoring area. A corollary to this phenomenon is that water levels in confined aquifer wells also tend to recover more quickly if pumping is decreased or stopped than they would in unconfined aquifer wells. Direct comparison between water levels from confined aquifer wells and unconfined 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 confined aquifer wells and unconfined 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 (fig. 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 unconfined or confined area of the aquifer. From the prestress period to 2021, water levels in the 13 wells measured in the unconfined 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 (fig. 8 and table 6). Water levels in the 12 wells measured in the confined 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) (fig. 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.

[“BM observation well” denotes continuous-recording observation wells that have been outfitted 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

BM observation well 1a BM observation well 4a Goldtooth Long House Valley Northeast Rough Rock Rough Rock Rough Rock Shonto Shonto Southeast Shonto Southeast Tuba City Tuba City Tuba City Rare Metals 2 Tuba City NTUA 1R Tuba City NTUA 3R Tuba City NTUA 4

8T-537 2T-514 3A-28 8T-510 8A-180 9Y-95 9Y-92 2K-300 2K-301 2T-502 3T-333 3K-325 — — — 3T-546

374.2 216.8 233.5 140.4 — — — 171.7 289.3 415.5 28.2 206.1 48.8 — — —

BM observation well 2a BM observation well 3a BM observation well 5a BM observation well 6a Forest Lake NTUA 1 Howell Mesa Kayenta West Keams Canyon PM2 Kits'iili NTUA 2 Kykotsmovi PM1 Kykotsmovi PM3 Marsh Pass Piñon PM6 Rough Rock Rough Rock Rough Rock Sweetwater Mesa White Mesa Arch

8T-538 8T-500 4T-519 — 4T-523 3K-311 8T-541 — — — — 8T-522 — 10R-119 10T-258 10R-111 8K-443 1K-214

205.4 171.5 419.5 832.5 — 452.5 282.6 473.9 — — — 131.7 — — — — — 218.9

Water level, 2021 Unconfined areas 374.4 216.8 233.8 141.8 44.0 112.6 165.1 171.6 289.1 415.9 28.7 204.9 48.6 — — — Confined areas 203.9 169.5 418.7 830.7 — 445.7 269.1 — — — — 133.0 — 262.1 310.5 191.4 546.4 218.4

Prestress period water level Feet below land surface Date 374.0 216.0 230.0 99.4 46.9 119.5 168.8 176.5 283.9 405.8 23.0 208.0 57.0 29.0b 34.2b 33.7

(a) (a) 10–29–53 08–22–67 11–13–53 08–03–49 12–13–52 06–13–50 12–10–52 08–22–67 12–02–55 06–30–55 09–24–55 02–12–69 11–08–71 08–06–71

−0.4 −0.8 −3.8 −42.4 2.9 6.9 3.7 4.9 −5.2 −10.1 −5.7 3.1 8.4 — — —

125.0 55.0 324.0 697.0 1,096R 463.0 230.0 292.5 1,297.9c 220.0 210.0 125.5 743.6 256.6 301.0 170.0 529.4 188.0

(a) 04–29–63 (a) (a) 05–21–82 11–03–53 03–17–76 06–10–70 01–14–99 05–20–67 08–28–68 02–07–72 05–28–70 12–02–53 04–14–60 08–04–54 09–26–67 06–04–53

−78.9 −114.5 −94.7 −133.7 — 17.3 −39.1 — — — — −7.5 — −5.5 −9.5 −21.4 −17.0 −30.4

aContinuous recorder. Prestress levels were estimated from a groundwater model, except for well BM observation well 3 (Brown and Eychaner, 1988) bWater level is from a previous well drilled to a shallower depth at the same location cWater level is the first water level measured after completion of well

Change in water level

20 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021

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.

Hydrologic Data 21 111°30' 37°

111°

110°30'

109°30'

110°

Page Dennehotso

8T-510 –42.4

1K-214 –30.4

COAL-LEASE AREA

3T-333

M oe

sh BM6 --–133.7

n ko pi

Tuba City Rare Metals 2 + 8.4

Tuba City

2K-301 –5.2

3K-311

3K-325 + 3.1

+17.3

h Piñon

BM5 4T-519 –94.7 Kykotsmovi PM3 sh --W Kykotsmovi PM1 --Keams Kykotsmovi Canyon PM2 ---

Li t tl e

BM1 8T-537 –0.4

Rough Rock

10R-119 –5.5 10R-111 –21.4 10T-258 –9.5

Chinle

Keams Canyon

Ganado

Or ac

9Y-95 +6.9

bi ne

9Y-92 + 3.7

Piñon PM6 ---

ai b

Was

r C olora do R i v e

35°30'

8K-443 –17.0

3A-28 –3.8

Chilchinbito

Kits’iili NTUA 2 --Forest Lake NTUA 1 ---

–5.7

36°

BM2 8T-538 –78.9

8A-180 +2.9

Wash

Tuba City NTUA 1R ---

3T-546 Tuba City --NTUA 3R ---

8T-541 –39.1

C h in l e

2K-300 + 4.9 BM4 2T-514 –0.8

36°30'

Kayenta

8T-522 – 7.5

2T-502 –10.1 Shonto

Cre

NAVAJO CO.

BM3 8T-500 –114.5 L a g u n a

APACHE CO.

C re e

NAVAJO CO.

COCONINO CO.

Na va

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'

Modified from Brown and Eychaner, 1988

25 MILES

Map area

25 KILOMETERS

ARIZONA

2K-300 + 4.9

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

BM2 8T-538 – 78.9

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]

City of Page, 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).

[“BM observation well” denotes continuous-recording observation wells that have been outfitted 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]

Date of well completion

Land-surface elevation (ft)

Well depth (ft bls)

8T-537 (BM observation well 1)

02–01–1972

5,864

851

8T-538 (BM observation well 2) 8T-500 (BM observation well 3) 2T-514 (BM observation well 4) 4T-519 (BM observation well 5) BM observation well 6 1K-214 2K-300 2K-301

01–29–1972 07–29–1959 02–15–1972 02–25–1972 01–31–1977 05–26–1950 06–00–1950b 06–12–1950

5,656 5,724 6,320 5,869 6,332 5,771 6,264 6,435

1,338 868 400 1,683 2,507 356 300 500

2T-502 3A-28 3K-311

08–10–1959 04–19–1935 11–00–1934b

6,670 5,381 5,855

523 358 745

3K-325 3T-333 3T-546 (Tuba City NTUA 4) 4T-523 (Forest Lake NTUA 1)

06–01–1955 12–02–1955 08–00–1971b 10–01–1980

5,250 4,940 5,206 6,654

450 229 612 2,674

8A-180 8K-443 8T-510 8T-522 8T-541 9Y-92 9Y-95 10R-111 10R-119 10T-258 Keams Canyon PM2

01–20–1939 08–15–1957 02–11–1963 07–00–1963b 03–17–1976 01–02–1039 11–05–1937 04–11–1935 01–09–1935 04–12–1960 05–00–1970b

5,200 6,024 6,262 6,040 5,885 5,615 5,633 5,757 5,775 5,903 5,809

107 720 314 933 890 300 300 360 360 670 1,106

BIA site number and (or) name

Screened/open interval(s) (ft bls) 300–360 400–420 500–520 600–620 730–780 470–1,338 712–868 250–400 1,521–1,683 1,954–2,506 168–356 260–300 318–328 378–500 12–523 (d) 380–395 605–745 75–450 63–229 256–556 1,870–1,910 2,070–2,210 2,250–2,674 60–107 619–720 130–314 180–933 740–890 154–300 145–300 267–360 (d) 465–670 906–1,106

Depth to top of N aquifer (ft bls)a 290

2021 static water level (ft bls) 374.4

452 155 160 1,520 1,950 250 0 30c

203.9 169.5 216.8 418.7 830.7 218.4 171.6 289.1

25 60 615

415.9 233.8 445.7

30c 24 0 ( f)

204.9 28.7 (e) (e)

40c 590 125c 480 700 50c 68c 210 310 460 900

44.0 546.4 141.8 133.0 269.1 165.1 112.6 191.4 262.1 310.5 (e)

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.—Continued [“BM observation well” denotes continuous-recording observation wells that have been outfitted 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]

Date of well completion

Land-surface elevation (ft)

Well depth (ft bls)

Kits'iili NTUA 2

10–30–1993

6,780

2,549

Kykotsmovi PM1

02–20–1967

5,657

995

Kykotsmovi PM3 Piñon PM6 Tuba City NTUA 1Rg Tuba City NTUA 3Rh Tuba City Rare Metals 2

08–07–1968 02–00–1970b 11–02–2018 11–02–2018 09–00–1955b

5,618 6,397 5,123 5,184 5,108

1,220 2,248 650 650 705

BIA site number and (or) name

Screened/open interval(s) (ft bls) 2,217–2,223 2,240–2,256 2,314–2,324 2,344–2,394 2,472–2,527 655–675 890–990 850–1,220 1,895–2,243 95-450 164-520 100–705

Depth to top of N aquifer (ft bls)a 2,205

2021 static water level (ft bls) (e)

880

(e)

840 1,870 0 34 255

(e) (e) (e) (e) 48.6

aDepth to top of N aquifer from Eychaner (1983) and Brown and Eychaner (1988) b00, indicates day is unknown cAll material between land surface and top of the N aquifer is unconsolidated—soil, alluvium, or dune sand dScreened or open intervals are unknown eNo water level collected in 2021 due to Coronavirus pandemic fDepth to top of N aquifer was not estimated gWell is a replacement for Tuba City NTUA 1 hWell 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 Prestress–2021

Number of wells

Median change in water level (feet)

Unconfined

−0.4

Confined

−25.9

Hydrologic Data 23

Aquifer conditions

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 (figs. 9, 10). In most of the unconfined 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 (fig. 8; table 6). Water levels have declined in most of the confined area, but the magnitudes of declines are varied. Larger 190

220

declines have occurred near the municipal pumping centers (wells Piñon PM6 and Keams Canyon PM2) and near the well field 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; figs. 8, 9, 10). Hydrographs for the Black Mesa continuous-record observation wells (fig. 11) show water levels since the early 1970s. The two wells in the unconfined areas (BM1 and BM4)

R R

250

280 170

200

R P

230 260

Water level, in feet below land surface

30 60 90 0

90 20

40 60 80

100 0

60 90 30 60

90 120 1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010

2015

EXPLANATION P Pumping R Recently pumping S Nearby site that taps same aquifer being pumped

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.

2020

2025

Hydrologic Data 25 have shown small seasonal or year-to-year variation since 1972 but show no apparent long-term decline. In the confined 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 (fig. 11). After the mid-2000s, water levels in BM2, BM5,

130

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 flattened out by around 2010 (fig. 11).

160

190 220 240

270

R RR

300

R P

330 370

Water level, in feet below land surface

400

430

R P

460 70

100

130

160 0

60 90 130

160

190

R R

220 70

100

130 160 1950

1955

1960

1965

1970

1975

1980

1985

1990

EXPLANATION P Pumping R Recently pumping

Figure 9.—Continued

1995

2000

2005

2010

2015

2020

2025

26 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021

1,070 1,090 1,110 1,130 1,150 1,170 1,190 170 200

A P

Water level, in feet below land surface

260 700

230

750 800

850 900 950 420 450

D R

480 510 250

300 350 400 450

500 550 190 220

250 280 1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010

2015

2020

2025

EXPLANATION P Pumping R Recently pumping S Nearby site that taps same aquifer being pumped

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

180

210 240 270 80

110

Water level, in feet below land surface

140 170 200 220 240 260 280 300 320

R R PP R

490

520

550 580 150

180

R R

210

240 220

250

280

2010

2015

310 270

300

330 360 1,250

1,300 1,350 1,400 1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

EXPLANATION P Pumping R Recently pumping S Nearby site that taps same aquifer being pumped

Figure 10.—Continued

2005

2020

2025

28 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021 10 5 0 –5 –10 10 5 0 –5 –10 0 –20

A NOTE: Well vandalized and missing data from May 1979 to March 1984

Water-level change from assumed equilibrium, in feet

–40 –60 –80 –100 0 –20

D NOTE: Measured intermittently before 1972

–40 –60 –80 –100 –120 0 –20

–40 –60 –80 –100 –20 –40

–60 –80 –100 –120 –140 –160 –180 1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010

2015

2020

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.

2025

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

Unnamed 110°30' Spring near Dennehotso

Cree

Pasture Canyon Spring

La gu n

Kayenta

Shonto

30'

Betatakin

Dennehotso

Unnamed Spring near Dennehotso

Chinle

h Was

n ko pi

09401260

Tuba City

09401265 M o e

Wash

Pasture Canyon Spring 3A-5

C h in l e

COAL-LEASE AREA

Red Lake

Moenkopi School Spring 3GS-77-6

Din

bit

36°

109°30'

110°

NAVAJO CO.

Na va

NAVAJO CO.

Page

COCONINO CO.

111°

APACHE CO.

111°30' 37°

(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 flow 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 (fig. 12). Discharge from Moenkopi School Spring was measured in December 2021 using the volumetric method

Kykotsmovi

t tl e

i ai b

r C olora do R i v e

Keams Canyon

09401110

35°30'

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'

Confined and unconfined conditions in the N aquifer within model boundary Confined Unconfined Approximate boundary between confined and unconfined conditions— From Brown and Eychaner (1988) Boundary of mathematical model— From Brown and Eychaner (1988)

Ganado 09400568

Burro Spring

Moenkopi School Spring

Burro Spring 6M-31

25 MILES

0 0

25 KILOMETERS

Map area

EXPLANATION

ARIZONA

Spring at which discharge was measured and water-chemistry Moenkopi School sample was collected—Number Spring is spring identification 3GS-77-6

09401260

Modified from Brown and Eychaner, 1988

Streamflow-gaging station operated by the U.S. Geological survey— Number is station identification City of Page, 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 (fig. 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 (fig. 13A).

Burro Spring is in the southwestern part of the study area and discharges from the Navajo Sandstone and alluvium (fig. 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 fluctuated since 1989 between 0.2 and 0.4 gal/min, but there is no significant (p>0.05) trend

17.0

15.0

EXPLANATION

Theil-Sen line (p-value < 0.001) Spring discharge

13.0 11.0 9.0 7.0

Note: Kendall’s tau = –0.67 - Slope of Theil-Sen line is significantly different from zero (p<0.05)

5.0 0.50

0.45

EXPLANATION

Theil-Sen line (p-value = 0.54) Spring discharge

0.40 0.35

Discharge, in gallons per minute

0.30 0.25 0.20 0.15 0.10

Note: Kendall’s tau = –0.10 - Slope of Theil-Sen line is not significantly different from zero (p>0.05)

0.05 45.0 43.0 41.0 39.0 37.0 35.0 33.0 31.0 27.0 25.0 23.0

EXPLANATION

Theil-Sen line (p-value = 0.46) Spring discharge Note: Kendall’s tau = 0.11 - Slope of Theil-Sen line is not significantly different from zero (p>0.05)

30.0

25.0

EXPLANATION

Theil-Sen line (p-value = 0.01) Spring discharge

20.0 15.0 10.0 5.0 0.0 1985

Note: Kendall’s tau = –0.41 - Slope of Theil-Sen line is significantly different from zero (p<0.05)

1990

1995

2000

2005

2010

2015

2020

2025

Figure 13. Plots of discharge from Moenkopi School Spring (360632111131101) (A); Burro Spring (354156110413701) (B); Pasture 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.

Hydrologic Data 31 Table 9. Discharge from Moenkopi School Spring, N aquifer, Black Mesa area, northeastern Arizona, 1952–2021.

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

Date of measurement

Navajo Sandstone (3GS-77-6)a

Discharge, in gallons per minute Navajo Sandstone (6M-31)

05–16–52

40.0

12–15–89

0.4

04–22–87

16.0b

12–13–90

0.4

11–29–88

12.5b

03–18–93

0.3

02–21–91

13.5b

12–08–94

0.2

04–07–93

14.6b

12–17–96

0.4

12–07–94

12.9b

12–30–97

0.2

12–04–95

10.0b

12–08–98

0.3

12–16-96

13.1b

12–07–99

0.3

12–17–97

12.0b

04–02–01

0.2

12–08–98

13.3b

04–04–02

0.4

12–13–99

13.7b

04–30–03

0.4

03–12–01

10.2b

04–06–04

0.2a

06–19–02

11.2b

03–28–05

0.2

05–01–03

11.2b

03–28–06

0.2

03–29–04

12.2b

06–04–09

0.3

04–04–05

11.5b

06–07–10

0.3

03–13–06

11.1b

06–08–11

0.4

05–31–07

9.0b

06–14–12

0.3

06–03–08

8.3b

07–30–13

0.3

06–03–09

8.0b

09–02–14

0.3

06–14–10

7.4b

06–23–16

0.2

06–10–11

9.0b

07–18–17

0.3

06–07–12

6.3b

06–06–18

0.3

07–29–13

6.4b

04–22–19

0.3

08–27–14

6.3b

11–02–20

0.3

06–21–16

6.0b

07–11–17

6.8b

06–06–18

6.4b

04–22–19

7.5b

12–22–21

9.1b

aInterfingering with the Kayenta Formation at this site bDischarge measured at water-quality sampling site and at a different point than the measurement in 1952

from a Kendall’s tau analysis (fig. 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 (fig. 12). This report refers to Pasture Canyon Spring when referencing the spring where water chemistry samples are collected and where

aDischarge is approximate because the container used for the volumetric measurement was not calibrated

spring discharge is measured, whereas the name Pasture Canyon Springs refers to the streamflow 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 fluctuated between 26.5 and 43.0 gal/min, but there

32 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021 Table 11. Discharge from Pasture Canyon Spring, N aquifer, Black Mesa area, northeastern Arizona, 1988–2021.

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, lithology, and Bureau of Indian Affairs site number (in parentheses) listed above dates and measured discharge]

Date of Discharge, in gallons per minute measurement Navajo Sandstone, alluvium (3A-5) 11–18–88 211a 03–24–92 233a 10–12–93 211a 12–04–95 38.0b 12–16–96 38.0b 12–17–97 40.0b 12–10–98 39.0b 12–21–99 39.0b 06–12–01 37.0b 04–04–02 37.0b 05–01–03 04–26–04 04–27–05 06–03–08 06–03–09 06–14–10 06–09–11 06–07–12 07–29–13 08–27–14 06–21–16 07–11–17 06–06–18 04–22–19

30.9b 30.6b 33.3b 29.4b 31.1b 34.3b 31.4b 26.5b 35.7b 39.3b 37.5b 43.0b 42.0b 43.0b

10–06–20

40.3b

aDischarge measured in channel below water-quality sampling point

Date of measurement 10–06–54 06–27–84 11–17–87 03–26–92 10–22–93 12–05–95 12–19–96 12–30–97 12–14–98 12–15–99 03–14–01 04–03–02 07–15–02 05–01–03 04–01–04 04–06–05 06–17–10 06–04–12 08–06–13 09–03–14 10–26–16 07–03–18 04–23–19 10–13–20

Discharge, in gallons per minute Navajo Sandstone (8A-224)a 1b 2b 5b 16.0 14.4 17.0 15.7 25.6 21.0 14.8 26.8 5.8 9.0 17.1 12.6 21.5 9.0 4.5 6.7 8.1 9.0 3.0 12.0 11.6

aDischarge measured in channel below water-quality sampling point bDischarge measured at a different point than later measurements

bDischarge measured at water-quality sampling point about 20 feet below upper spring on west side of canyon

is no significant (p>0.05) trend from a Kendall’s tau analysis (fig. 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 (fig. 12), and it discharges from the Navajo Sandstone. As in previous years, measurements at Unnamed Spring near Dennehotso are made using a flume. 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 (fig. 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 flow is affected by seasonal fluctuations 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

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 streamflow-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 (fig. 14). Data collection at these stations began in July 1976 (Moenkopi Wash at Moenkopi, Ariz., 09401260), June 1993 (Dinnebito Wash near Sand Springs, Ariz.,

10,000 1,000

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 figure 14 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. Estimated daily values are based on adjacent good records, records from comparable stations, and discrete discharge measurements. Areas of hydrographs in figure 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 flow at the four streamflow sites, are described briefly below.

C 0.4

100

Gage discontinued on 10/1/2020

Discharge, in cubic feet per second

0.1

0.4

0.1 0.01

0.01

0.8

0.6

0.4

Gage discontinued on 10/1/2020

0.4

0.2

0.1

0.8

0.2

J F M A M J J A S O N D J F M A M J J A S O N D

2020

0.1

J F M A M J J A S O N D J F M A M J J A S O N D

2021

2020

2021

EXPLANATION Daily mean discharge

Estimated daily mean discharge

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 Table 13. Streamflow-gaging stations used in the Black Mesa monitoring program, their periods of record, and drainage areas. [—, not determined]

Station name Moenkopi Wash at Moenkopi, Ariz.

Station number

Date data collection began

Drainage area (square miles)

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

—

Moenkopi Wash

Polacca Wash

Moenkopi Wash has a drainage area of 1,629 mi2 and drains a large portion of the western part of Black Mesa. The streamflow 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 streamflow gage operation, there has generally been continuous flow at the gage except for the summer months, when the stream is often dry at the gage (fig. 14). Monsoon rain events occurring between July and September can result in large, sediment-laden flows in Moenkopi Wash. The maximum instantaneous discharge recorded at the gage was 10,100 cubic feet per second (ft3/s) on September 30, 1983. There are no observed N-aquifer springs issuing directly from the Navajo Sandstone near the streamflow gage. During base-flow conditions, flow seems to initiate from Moenkopi Wash alluvium, but it is assumed this flow is supplied by the N aquifer from below and through the alluvium.

Polacca Wash has a drainage area of 905 mi2 and drains a large section of the eastern part of Black Mesa. The streamflow 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 streamflow gage is in a stream reach that often has flow. During the period of streamflow-gage operation, there has been continuous flow 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 (fig. 14). From July through September, monsoon rain events can result in large, sediment-laden flows in Polacca Wash. The maximum instantaneous discharge recorded at the gage was 2,140 ft3/s on July 30, 2017. Most of the base flow at the Polacca Wash streamflow gage is likely provided by a spring issuing from the base of the Navajo Sandstone located about 1 mi upstream from the gage.

Dinnebito Wash

Pasture Canyon Spring

Dinnebito Wash has a drainage area of 473 mi2 and drains some of the middle part of Black Mesa. The streamflow 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 flow year-round, though most of the stream is dry much of the year. The streamflow gaging station is in a perennial reach (fig. 14). From July through September, monsoon rain events can result in large, sediment-laden flows in Dinnebito Wash, although no high flows were recorded during the summer of 2020. The maximum instantaneous discharge recorded at the gage was 3,970 ft3/s on September 20, 2004. The minimum daily mean discharge recorded at the gage was 0.05 ft3/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 streamflow gage. During base-flow conditions, flow seems to initiate from Dinnebito Wash alluvium, but it is assumed this flow is supplied by the N aquifer from below and through the alluvium.

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 flow begins near the head of the canyon from a piped spring. Discharge from that spring accounts for around 20 percent of the total flow measured at the streamflow gage, located approximately 0.25 mi downstream from the spring. The remaining base flow measured at the streamflow 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 streamflow gage (fig. 14). In addition, most of the alluvium in the wash is composed of reworked dune sand, so precipitation tends to infiltrate rather than run off. During the operational period of record for the gage, the minimum daily mean discharge recorded was 0.14 ft3/s on September 5–8, 2017, and the maximum instantaneous discharge was 4.96 ft3/s on October 3, 2018.

Hydrologic Data 35

Surface-Water Base Flow Trends in the groundwater-discharge component of total flow at the four streamflow-gaging stations were evaluated on the basis of the median of 120 consecutive daily mean flows for four winter months (November through February) and used as a surrogate measure for base flow (fig. 15). Median winter streamflow 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 flow was assumed to represent constant annual groundwater discharge. Most flow 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 flow; during

summer months, some or all groundwater discharge can be taken up by plants or can evaporate directly to the atmosphere. Rather than the average flow, the median flow 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 flow for November, December, January, and February is an estimate of groundwater discharge rather than a calculation of base-flow groundwater discharge. A more rigorous and accurate calculation of base-flow would involve detailed evaluations of streamflow hydrographs, flows into and out of bank storage, gain and loss of streamflow 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 flow, however, is useful as a consistent, easily measurable index for evaluating possible temporal trends in groundwater discharge.

6 5

EXPLANATION

Theil-Sen line (p-value < 0.001) Median winter discharge

4 3 2 1 NOTE: Kendall’s tau = –0.45 - Slope of Theil-Sen line is significantly different from zero (p<0.05) 0 1975 1980 1985 1990 1995 2000

2005

2010

2015

2020

0.6 0.5 0.4

Discharge, in cubic feet per second

0.3 0.2

B EXPLANATION

Theil-Sen line (p-value = 0.02) Median winter discharge

0.1 NOTE: Kendall’s tau = –0.34 - Slope of Theil-Sen line is significantly different from zero (p<0.05) 0.0 1994 1996 1998 2000 2002 2004 2006 2008

0.45 0.40 0.35 C 0.30 0.25 0.20 0.15 0.10 0.05 NOTE: Kendall’s tau = –0.24 - Slope of Theil-Sen line is not significantly different from zero (p>0.05) 0.00 2008 1994 1996 1998 2000 2002 2004 2006 0.50 0.45 D 0.40 0.35 0.30 0.25 NOTE: Kendall’s tau = –0.32 - Slope of Theil-Sen line is not significantly different from zero (p>0.05) 0.20 2011 2012 2003 2004 2005 2006 2007 2008 2009 2010

2012

2010

2014

2018

2016

2020

EXPLANATION

Theil-Sen line (p-value = 0.11) Median winter discharge

2012

2010

2014

2016

2018

2020

EXPLANATION

Theil-Sen line (p-value = 0.10) Median winter discharge

2013

2014

2015

2016

2017

2018

2019

2020

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.

<5.0 <2.0 <0.10 <0.02 <0.06 <0.01 <0.02 <0.40 <0.30 <0.010 <0.004 <0.040

<0.020

Iron, dissolved (µg/L as Fe) Boron, dissolved (µg/L as B) Arsenic, dissolved (µg/L as As) Sulfate, dissolved (mg/L as SO4) Silica, dissolved (mg/L as SiO2) Fluoride, dissolved (mg/L as F) Chloride, dissolved (mg/L as Cl) Sodium, dissolved (mg/L as Na) Potassium, dissolved (mg/L as K) Magnesium, dissolved (mg/L as Mg) Calcium, dissolved (mg/L as Ca) Orthophosphate, dissolved (mg/L as P)

Between 2020 and 2021, water samples were collected from Moenkopi School Spring, Burro Spring, Pasture Canyon Spring, and Unnamed Spring near Dennehotso (figs. 12, 16). Geologic maps and field observations indicate that these four springs discharge water from the

Nitrogen, NO2 + NO3, dissolved (mg/L as N)

Water-Chemistry Data for Springs that Discharge from the N Aquifer

[mg/L, milligrams per liter; <, less than; μg/L, micrograms per liter; °C, degrees Celsius]

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, specific conductance, temperature, dissolved oxygen, alkalinity, and discharge rates at springs. Field alkalinities were determined using incremental equivalence. Dissolved constituent samples were filtered through a 0.45-micron pore size filter 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 field personnel, use of standard USGS field 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 field blank sample was gathered during collection of field water-quality samples. The field blank was processed at Pasture Canyon Spring during the collection of an environmental sample. Concentrations of analytes in the field 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 specific 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.

Table 14. Chemical analyses of a field blank water sample processed at Pasture Canyon Spring, Black Mesa area, northeastern Arizona, 2020.

Water Chemistry

Dissolved solids, residue at 180°C (mg/L)

Median winter flows calculated for winter 2019 were 1.72 ft3/s for Moenkopi Wash at Moenkopi, 0.26 ft3/s for Dinnebito Wash near Sand Springs, 0.13 ft3/s for Polacca Wash near Second Mesa, and 0.25 ft3/s for Pasture Canyon Springs near Tuba City (fig. 15A–D). The median winter flows calculated for winter 2020 for Moenkopi Wash at Moenkopi and Pasture Canyon Springs near Tuba City were 0.82 and 0.34 ft3/s, respectively. Median winter flows were not calculated for winter 2020 for Dinnebito Wash and Polacca Wash because the streamflow gages were discontinued in October 2020. A significant decreasing trend in median winter flows, calculated using Kendall’s tau (p<0.05), is indicated at the Moenkopi Wash and Dinnebito Wash streamflow-gaging stations, but no significant trends are indicated at the Polacca Wash and Pasture Canyon Springs streamflow-gaging stations (fig. 15A–D).

<20

36 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021

Hydrologic Data 37 111°

Cree

ek C r e Dennehotso

a La gu n

Kayenta

NAVAJO CO.

Na va

109°30'

110°

NAVAJO CO.

Page

COCONINO CO.

110°30'

Betatakin

APACHE CO.

111°30' 37°

Unnamed Spring near Dennehotso 115

Shonto COAL-LEASE AREA

36°30'

Pasture Canyon Spring

Chinle

Wash

Red Lake

Was

C h in l e

152

Mo en k o p i

n Di

bit

36°

Moenkopi School Spring

302

Tuba City

Li olora do

Keams Canyon

eC 315

Burro Spring

tt l

Kykotsmovi

Ganado

Ri ver

35°30'

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'

25 MILES

0 0

Modified from Brown and Eychaner, 1988

25 KILOMETERS

Map area ARIZONA

Pasture Canyon Spring

Spring at which discharge was measured and water-chemistry sample was collected City of Page, Arizona

Milliequivalents per liter

10 Sodium Calcium Magnesium

CATIONS ANIONS 5 0 5 10 Chloride 315

Bicarbonate Sulfate

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.

Figure 16. Map showing water chemistry and distribution of dissolved solids at springs in the N aquifer, Black Mesa area, northeastern Arizona, 2020–2021.

38 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021 unconfined 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 fills 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 (fig. 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. [Specific cond., specific 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, fluoride; SiO2, silica; SO4, 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 CaCO3)

354156110413701 Burro Spring (6M-31) 11/02/20

7.3

496

14.2

313a

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

12/22/21

7.3

480

1.61

36.9

102

1.58

12.7

78.3

1.11

4.84

76.7

360632111131101 Moenkopi School Spring (3GS-7-6) 18.6

302

47.0

10.5

361021111115901 Pasture Canyon Spring (3A-5) 10/06/20

7.7

243

16.8

152

30.9

4.50

364656109425400 Unnamed Spring near Dennehotso (8A-224) 10/13/20

8.1

197

11.8

115

30.4

4.43

aDissolved 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 [Specific cond., specific 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, fluoride; SiO2, silica; SO4, 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)

SiO2, diss. (mg/L)

SO4, diss. (mg/L)

213

0.2

20.7

0.36

16.2

56.4

210

0.9

21.7

0.35

14.6

58.0

Orthophosphate, diss. (mg/L as P)

Fe, diss. (µg/L)

As, diss. (µg/L)

B, diss. (µg/L)

<0.040

<0.004

59.3

0.94

<0.040

<0.004

10.3

0.58

0.005

<5.0

2.3

0.020

<5.0

1.9

<5.0

2.5

N, diss. (mg/L)

354156110413701 Burro Spring (6M-31)

360632111131101 Moenkopi School Spring (3GS-7-6) 124

0.1

45.1

0.17

14.4

63.6

3.31

361021111115901 Pasture Canyon Spring (3A-5) 95.2

0.2

4.88

92.8

0.4

2.90

0.16

9.88

16.5

4.44

364656109425400 Unnamed Spring near Dennehotso (8A-224) 0.12

12.8

8.53

2.00

0.023

Hydrologic Data 39 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]

Year

Specific conductance, field (μS/cm)

1989 1990 1993 1994 1996 1997 1998 1999 2001 2002 2003 2004 2005 2006 2009 2010 2011 2012 2013 2014 2016 2017 2018 2019 2020 2021

485 545a 595 597a 525 511a 504 545 480 591 612 558 558 576 577 583 560 553 560 549 544 536 532 522 496 489

1948 1982 1986 1988 1992 1993 1995 1996 1997 1998 1999 2001 2002 2003 2004 2005 2008 2009 2010

227a 240 257 232 235 242 235 238 232 232 235 236 243d 236 248 250 240 241 314

Dissolved Chloride, solids, dissolved residue at (mg/L as Cl) 180 °C (mg/L) Burro Spring 308 22.0 347 23.0 368 30.0 368 26.0 324 23.0 332 26.0 346 24.6 346 24.8 348 23.6 374 30.6 374 30.5 337 24.9 357 25.8 359 25.0 372 25.7 355 25.9 353 25.7 330 23.1 350 24.4 360 22.8 318 22.2 329 22.0 330 21.6 332 23.7 313b 20.7 315 21.7 Pasture Canyon Spring (c) 6.0 — 5.1 — 5.4 146 5.3 168 7.10 134 5.3 152 4.80 130 4.70 143 5.27 147 5.12 142 5.06 140 5.06 143 5.14 151 5.09 150 5.50 149 5.07 149 5.01 160 5.10 157 5.25

Sulfate, dissolved (mg/L as SO4) 59 65.0 85.0 80.0 62.0 75.0 70.4 69.2 67.8 77.0 81.1 63.6 68.9 68.2 72.5 71.5 69.5 64.7 67.7 64.6 61.7 59.5 58.7 63.0 56.4 58.0 13 18.0 19.0 18.0 17.0 17.0 14.0 15.0 16.9 16.2 14.2 17.0 16.5 16.1 16.4 16.3 18.3 18.6 17.9

Year

2011 2012 2013 2014 2016 2017 2018 2019 2020 1952 1987 1988 1991 1993 1994 1995 1996 1997 1998 1999 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2016 2017 2018 2019 2021 1984 1987 1992 1993 1995

Dissolved Chloride, Sulfate, solids, dissolved dissolved residue at (mg/L as Cl) (mg/L as SO4) 180 °C (mg/L) Pasture Canyon Spring—Continued 236 146 5.47 18.5 248 142 5.20 17.5 245 145 5.16 17.7 249 149 5.03 17.2 252 155 5.09 17.2 236 151 5.07 17.1 238 145 5.04 16.9 224 148 5.02 16.8 243 152 4.88 16.5 Moenkopi School Spring 222 — 6 — 270 161 12.0 19.0 270 155 12.0 19.0 297 157 14.0 20.0 313 204 17.0 27.0 305 182 17.0 23.0 314 206 18.0 22.0 332 196 19.0 26.0 305a 185 17.8 23.8 296 188 17.6 23.7 305 192 18.7 25.6 313 194 18.3 25.5 316 191 18.3 23.1 344 197 18.6 23.4 349 196 19.1 21.3 349 212 23.3 29.6 387 232 27.2 34.2 405 253e 30.6 39.9 390 230 28.3 37.6 381 240 27.0 35.6 480 217 26.2 33.4 374 216 28.5 36.2 382 218 27.5 33.3 370 220 27.2 33.3 382 226 28.5 34.6 427 244 34.6 43.8 424 266 35.5 44.7 434 260 36.9 45.9 428 255 39.3 49.1 480 302 45.1 63.6 Unnamed Spring near Dennehotso 195 112 2.8 7.1 178 109c 3.4 7.5 178 108 3.60 7.30 184 100 3.2 8.00 184 124 2.60 5.70

Specific conductance, field (μS/cm)

40 Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021 Table 16.—Continued

Year

1996 1997 1998 1999 2001 2002 2003 2004 2005 2010 2011 2012 2013 2014 2016 2018 2019 2020

Dissolved Chloride, Sulfate, solids, dissolved dissolved residue at (mg/L as Cl) (mg/L as SO4) 180 °C (mg/L) Unnamed Spring near Dennehotso—Continued 189 112 2.80 8.20 170a 98 2.40 6.10 179 116 2.43 5.36 184 110 2.76 6.30 176 116 2.61 5.96 183 104 2.67 7.38 180 118 2.95 7.16 170 117 2.72 5.05 194 114 2.65 8.67 259 155 9.38 15.5 292 172 14.5 24.1 298 179 13.5 21.9 196 127 3.06 8.24 160 122 2.68 7.40 197 116 3.21 9.46 157 108 2.33 5.39 156 105 2.39 6.02 197 115 2.90 8.53

Specific conductance, field (μS/cm)

aValue is different in Black Mesa monitoring reports before 2000. Earlier reports showed values determined by laboratory analysis bValue determined by the sum of constituents cValue is different in Black Mesa monitoring reports before 2000. Earlier reports showed values determined by the sum of constituents dValue was measured in the laboratory, not in the field eValue is different in Black Mesa monitoring reports prior to this report. Earlier reports showed values determined by the sum of constituents

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 specific 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 significant increasing trends (p<0.05) (table 16, fig. 17). Concentrations of the same constituents from Burro Spring, Pasture Canyon Spring, and Unnamed Spring near Dennehotso either showed no significant trends or showed decreasing trends (table 16, fig. 17). At Burro Spring, no significant 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 significant 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 figure 17B to allow plotting results from other springs with higher concentrations of chloride, the trend is difficult to see. Significant 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 (fig. 17).

Hydrologic Data 41 A 400 Dissolved solids, in milligrams per liter

350 300 250 200 150 100 50

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)

Chloride concentrations, in milligrams per liter

50 45 40 35

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)

30 25 20 15 10 5 0

Sulfate concentrations, in milligrams per liter

90 80 70 60 50 40 30 20 10 0 1980

1985

1990

EXPLANATION Burro Spring

Theil-Sen line Analyte concentration

1995

2000

2005

2010

2015

2020

2025

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)

Moenkopi School Spring Theil-Sen line Analyte concentration

Pasture Canyon Spring Theil-Sen line Analyte concentration

Unnamed Spring near Dennehotso 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 streamflow 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 unconfined 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 confined 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 confined 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 fluctuated, 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. Streamflow was measured continuously during calendar years 2020 and 2021 at the Moenkopi Wash at Moenkopi and Pasture Canyon Springs near Tuba City streamflow-gaging stations and was measured continuously through September 30, 2020, at the Dinnebito Wash near sand springs and Polacca Wash near Second Mesa streamflow-gaging stations. Median flows 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 flows indicate a decreasing trend in discharge. Winter flows at Polacca Wash and Pasture Canyon Springs have fluctuated but show neither a significant increase nor decrease. Between 2020 and 2021, water samples were collected at four springs and were analyzed for selected chemical constituents. A field blank was collected at Pasture Canyon Spring during the collection of an environmental sample. Concentrations of analytes in the field 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 significant 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

Mason—Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021—OFR 2024–1019

ISSN 2331-1258 (online) https://doi.org/10.3133/ofr20241019

Groundwater, Surface-Water, and Water-Chemistry Data, Black Mesa Area, Northeastern Arizona—2019–2021

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