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Arizona Strip
Paria Basin
The Paria basin occupies 390 square miles in
north-central Arizona within the Plateau uplands province. High desert plateaus and incised canyons dominate the landscape. The basin is bounded on the north by the Arizona-Utah state line, on the
south and west by the Vermillion Cliffs, and on the east by the Colorado River. Elevation ranges from a high of 7,100 feet above mean sea level on the
Paria Plateau to 3,200 feet above mean sea level along the Colorado River.
Most of the groundwater issues to small springs around
the perimeter of the basin where it is consumed by evapotranspiration. The Colorado and Paria Rivers constitute the only perennial rivers in the
basin.
Characteristic of the Colorado Plateau, the geologic
make-up of the Paria Basin consists of a gently-sloping sequence of limestone,
sandstone, and shale formations. Groundwater
is present in several aquifers that are made up of one or more of these
formations. In the Paria Plateau,
groundwater generally moves from south to north and is discharged to springs in
the canyon of the Paria River. A
portion however, moves south toward the Vermillion Cliffs which form the
southern boundary of the basin. Discharge
to springs along the Cliffs is estimated to be about 3,500 acre-feet per year (Levings
and Farrar, 1978). The exact
location of the groundwater divide is unknown due to lack of data in the area. Water levels in wells on the Paria Plateau range from 515 feet to 1,500
feet below land surface. In the
Wahweap area, groundwater levels have responded to the filling of Lake Powell. A rise of almost 350 feet was documented by Levings and Farrar (1978) in
the vicinity of the lake.
Groundwater development has been relatively small. There is an estimated 1.5 million acre-feet of groundwater in storage to
1,200 feet below land surface and 50 acre-feet were pumped in 1985 (Arizona
Department of Water Resources, 1988). The
N-aquifer, composed of Navajo Sandstone, Kayenta Formation, and Moenave
Formation, is the primary aquifer in the area. Most wells are from 620 to 1,500 feet deep and yield from 30 to 1,400
gallons per minute for domestic and public supply. The largest yields come from wells which penetrate fracture zones (Levings
and Farrar, 1978).
Water quality varies across the basin. In the Paria Plateau, water samples contain less than 300 milligrams per
liter of dissolved solids. In the
Wahweap area, dissolved solids concentrations generally exceed the recommended
secondary maximum contaminant level of 500 milligrams per liter.
Kanab Plateau Basin
The Kanab Plateau basin covers about 4,470 square miles
of north-central Arizona. Ponderosa
pine-covered plateaus, semi-arid plains and incised canyons dominate the
landscape. The basin is bounded to
the north by the Arizona-Utah border, on the south and east by the Colorado
River, and on the west by the Hurricane Cliffs. Elevation ranges from a high of 9,100 feet above mean sea level on the
Kaibab Plateau to a low of 1,600 feet above mean sea level at the downstream end
of the Colorado River.
Kanab Creek dissects the basin and forms the major
surface-water drainage in the area, however, the majority of the stream course
is ephemeral, flowing only in response to rainfall or snowmelt. Numerous springs in the Grand Canyon sustain baseflow to tributaries of
the Colorado River. The volume of
groundwater which issues from the larger springs totals over 160 acre-feet per
year (After Levings and Farrar, 1978 and Levings and Farrar, 1979).
The Kanab Plateau basin contains a flat-lying to
gently-sloping sequence of alternating sandstones, limestones, and shales. Groundwater is obtained from several aquifers which are made up of one or
more of these formations. Many of
the aquifers overlie each other but are generally not hydraulically connected. Groundwater movement is geologically controlled, moving from recharge
areas downward until a relatively impermeable unit is encountered where it
accumulates. Faults throughout the
area act as avenues for both vertical and lateral migration of groundwater. Springs issue where faults or saturated units are incised by canyons. Tapeats Creek and Bright Angel Creek make up the largest natural
discharges in the basin, with baseflows of 60 and 21 cubic feet per minute,
respectively (Johnson and Sanderson, 1968). These two creeks constitute about 75% of the natural groundwater
discharge from the basin.
Groundwater development in the basin has been small. Approximately 2,010 acre-feet were withdrawn in 1985 (Arizona Department
of Water Resources, 1988). Most
wells have been drilled for domestic and stock purposes, however, most of the
groundwater pumped in the basin is used for irrigation. Many different geologic formations have supplied small quantities of
water to wells but occurrence is variable. Alluvium along the washes in the Short Creek - Cane Beds area has been
the most productive, yielding up to 200 gallons per minute to irrigation wells (Levings
and Farrar, 1979).
Water quality throughout the area is generally acceptable
for domestic and livestock use, however, sulfate and dissolved solids
concentrations can be high locally.
Shivwits Plateau Basin
The Shivwits Plateau basin occupies 1,820 square miles in
northwestern Arizona. Most of the
basin falls in the Plateau uplands province. The Arizona-Utah state line is the basin’s northern boundary, the
Colorado River is the southern boundary, the Hurricane Cliffs are the eastern
boundary, and the Grand Wash Cliffs and east flank of the Virgin Mountains are
the basin’s western boundary.
Most of the Shivwits Plateau basin is a high plateau with
elevations of 4,000 to 6,000 feet above mean sea level. The lowest point in the basin is along the Colorado River at 1,220 feet
above mean sea level.
The basin is composed of an alternating sequence of
limestones, sandstones, and shales. Local
faulting and erosion have carved mesas and canyons into these flat-lying
sedimentary rocks. The Kaibab
Limestone and Moenkopi Formation outcrop widely throughout the basin (Wilson and
Moore, 1959). Alluvial sands and
gravels occupy the larger washes and canyons in the basin.
Most groundwater is drawn from the alluvial sand and
gravels along the larger washes. Wells
that penetrate the consolidated sedimentary rocks provide minor amounts of
water. A number of wells drilled
into these sedimentary rocks have been dry holes, but the wells that do produce
water have higher well yields than the alluvial wells. This indicates that well yields tapping the consolidated sedimentary
formations are controlled by faults and fractures. Well depths range from 15 feet in the alluvium to 3,120 feet deep in the
consolidated sedimentary rocks, and water levels vary from 10 feet to 908 feet
below land surface (Arizona Department of Water Resources, 1991). Well yields generally are low, ranging from less than 10 gallons per
minute to 45 gallons per minute (Levings and Farrar, 1979).
With less than 20 producing wells, groundwater
development in the Shivwits Plateau basin is very slight. The U.S. Geological Survey estimated that groundwater withdrawals were
less than 10 acre-feet per year in 1976 (Levings and Farrar, 1979). Stock and ‘domestic wells account for all water use in the basin. The basin has no flowing rivers, and the washes only flow in response to
rainfall and winter snowmelt. Infiltration
of the rainfall and snowmelt is the sole source of recharge for the basin.
Water quality from wells generally is suitable for most
domestic uses. Water from local
springs and seeps tends to be of slightly better quality than the well water. Total dissolved solids concentrations of 1,100 milligrams per liter and
high sulfate concentrations were reported from one well (Levings and Farrar,
1979).
Virgin River Basin
The Virgin River basin is located in the extreme
northwestern corner of Arizona and contains 433 square miles. The Virgin River basin is bounded on the north and the west by the
Arizona-Utah state line and the Arizona-Nevada state line, respectively. The northeast-southwest trending Virgin and Beaver Dam Mountains form the
basin’s eastern and southern boundary. Elevations
above mean sea level range from 8,000 feet in the Virgin Mountains to 1,550 feet
along the Virgin River.
The Virgin River flows through the basin from the
northeast to the southwest. About
five miles upstream from Littlefield, Arizona, the Virgin River cuts through the
Beaver Dam Mountains at a place called the Narrows”. South of “the Narrows”, the Virgin River flows through a
broad alluvial valley that is bordered on the northwest by an uplands area
composed of sands and gravels, and to the southeast by the Virgin Mountains. Numerous washes drain the upland and mountain areas; springs provide
small perennial reaches in some of the washes (Glandy and Van Denburg, 1969). Beaver Dam Wash is the largest tributary and has about a one mile
perennial stretch above its confluence with the Virgin River. Numerous springs, primarily located upstream of Littlefleld, Arizona,
maintain the Virgin River’s baseflow.
The Virgin River Valley and Beaver Dam Wash to the
northwest are filled with basin-fill sediments composed of silt, sand, and
gravel. Glancy and Van Denburg
(1969) divided the basin-fill sand and gravel deposits into two units; a younger
floodplain unit of silt, sand, and gravel that the Virgin River flows through,
and an older underlying basin-fill unit of semi-consolidated silts, sands,
gravels, and boulders. In the
Beaver Dam Mountains, basaltic lava covers the sedimentary rocks. The Virgin Mountains are composed of igneous and metamorphic rocks.
Groundwater development in the basin is mostly in the
alluvial basin-fill deposits that occupy the Virgin River Valley and Beaver Dam
Wash. In the valley, the younger
and older basin-fill units act as one aquifer. The alluvium in Beaver Dam Wash is largely isolated from other
water-bearing units, although groundwater from the wash discharges into the
alluvial aquifer of the Virgin River Valley (Black and Rascona, 1991). Most of the wells in the alluvium are 200 feet deep or less, and water
levels range from 10 to 300 feet below land surface (Black and Rascona, 1991). Well yields vary from 5 gallons per minute in small domestic and stock
wells, to 2,000 gallons per minute in larger irrigation wells (Levings and
Farrar, 1979).
Groundwater also occurs in two other aquifers in the
basin: the alluvial fan deposits that occur southeast of the Virgin River
between Littlefield, Arizona, and the Virgin Mountains; and the Muddy Creek
Formation. The alluvial fan
deposits overlie a limestone, which is the top of a unit known locally as the
“Littlefield Formation”, and form a shallow water-table aquifer (Black and
Rascona, 1991). Although few wells
are completed in this shallow aquifer, many springs originate from it where
groundwater flows over the limestone. Discharges
from springs range from 10 to 50 gallons per minute and reported well discharges
range from 30 to 1,500 gallons per minute (Black and Rascona, 1991). Depth to water in wells completed in the aquifer is 15 to 52 feet below
land surface (Black and Rascona, 1991).
The Muddy Creek Formation, a series of siltstones,
sandstones, and conglomerates, is known to yield water north of the City of
Mesquite, Nevada which is adjacent to the Virgin River basin. A City of Mesquite well located in Section 3, Township 13 South, Range 17
East, is completed in the Muddy Creek Formation and yields 350 gallons per
minute (Black and Rascona, 1991), The altitude of the water level and water
chemistry in the well suggest that the Muddy Creek Formation is a separate
aquifer from the alluvium in this area (Black and Rascona, 1991).
Only two known wells in the northeastern part of the
basin tap the sedimentary rock units. Measured
water levels in these wells were 262 and 838 feet below land surface (Black and
Rascona, 1991). Many of the springs
that support the flow of the Virgin River and other washes probably originate
from the sedimentary rock units (Glancy and Van Denburg, 1969).
An estimated 6,000 acre-feet of water were pumped from
the Arizona portion of the basin in 1990 (Black and Rascona, 1991). Most of the water is used for irrigating crops grown in the Virgin River
floodplain. The groundwater is used
to supplement surface water diverted from the Virgin River. There are an estimated 1.7 million acre-feet of groundwater in storage
above a depth of 1,200 feet below land surface (Arizona Department of Water
Resources, 1988). Direct recharge
from precipitation is small. Glancy
and Van Denburg (1969) estimated that recharge to the Arizona portion of the
lower Virgin River basin is not more than 5,900 acre-feet per year. Most recharge probably comes from infiltration of water from the Virgin
River (Glancy and Van Denburg, 1969).
Historic data indicate that water levels in the Virgin
River basin generally are not declining, however, long-term water-level
information for the area is inadequate. Increasing
groundwater withdrawals may adversely impact the riparian habitat of the Beaver
Dam Wash. Increasing water demands
in Nevada and Utah may warrant an interstate compact regarding the management of
groundwater resources of the Virgin River basin.
Water quality generally is suitable for most uses, but
wells near the Virgin River tested high in total dissolved solids and high in
sulfate, sodium, and calcium ion concentrations (Glancy and Van Denburg, 1969). Wells in the alluvium of Beaver Dam Wash generally had better quality
water.
Grand Wash Basin
The Grand Wash basin contains approximately 960 square
miles in northwestern Arizona. The
basin is located along the boundary between the Plateau uplands and the Basin
and Range provinces. Most of the
basin is within the Basin and Range province. The Grand Wash basin is drained by Cottonwood Wash and Grand Wash which
both carry runoff south to the Colorado River. The basin is bounded on the north by the Virgin Mountains, on the east by
the Grand Wash Cliffs, on the south by the Colorado River, and on the west by
the Arizona-Nevada state line. Elevation
in the basin varies from 2,100 feet above mean sea level along the Colorado
River to about 8,000 feet above mean sea level in the Virgin Mountains.
The sediments that fill the alluvial valley are, in
descending order: the alluvial sands and gravels in the ephemeral washes; the
Muddy Creek Formation, a series of siltstones, sandstones, and conglomerates
(Lovejoy, 1980); and the basal Cottonwood Wash Formation, composed of sandstones
and siltstones (Moore, 1972). Basaltic
lavas have been deposited in the northern part of the basin and are interbedded
with the Muddy Creek Formation (Moore, 1972).
There are four geologic units that yield water in the
Grand Wash basin: the streambed alluvium, the Muddy Creek Formation, basalts,
and the Cottonwood Wash Formation. Producing
wells are located in the streambed alluvium and in the Muddy Creek and
Cottonwood Wash Formations (Levings and Farrar, 1979). No wells penetrate to the basement rocks in the alluvial valley, and
there are no reported wells in the flat-lying sedimentary rocks northwest and
east of the valley. Several springs that issue from basaltic lava flows provide
small amounts of water.
Groundwater development in the Grand Wash basin is
minimal. There are less than 20
wells in the basin, and their combined pumpage is between 2 and 10 acre-feet per
year (U.S. Geological Survey, 1986). The
wells are all low-yield stock and domestic wells. Well depths vary from 35 feet in the alluvium to 850 feet
below land surface in the Cottonwood Wash Formation. Depth to water is reported to be as shallow as 5 feet in the alluvium and
650 feet below land surface in the Muddy Creek Formation (Levings and Farrar,
1979). Several wells drilled into
the Muddy Creek and Cottonwood Wash Formation sandstones have been dry holes.
Water quality generally is suitable for most domestic
uses. Two springs that issue from
the basaltic lava flows had total dissolved solids concentrations of 287 and 317
milligrams per liter and fluoride concentrations of 0.2 and 0.4 milligrams per
liter (Levings and Farrar, 1979).
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