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Upper Gila Watershed Partnership
The Gila Watershed Partnership is located in southeastern Arizona.
It contains the Safford, Duncan Valley and Morenci basins.
The Gila Watershed in Arizona is
in a unique and fragile position. The drought, failing economics of
agricultural industries make it increasingly more difficult for
farmers and ranchers to stay on the land. Pressures on the mining and
timber industries add increased economic instability in an already
stressed economy. The exploding development and clash of urban and
rural values threaten existing water supplies.
Increased public awareness of environmental
issues and possible solutions has spawned interest from a diverse new community.
This new community is no longer limited to environmental organizations, but now
includes ranchers, farmers and miners in the Gila River Valley, and also
includes a growing urban population.
The primary watershed group in the
Gila River Valley has been active for many years and has accomplished numerous
projects to enhance and protect the health of the watershed. Along with partners
in New Mexico, the Arizona watershed group has recently gone through
reorganization and adopted a new name, “The Gila Watershed Partnership.” This
name acknowledges the watershed as a whole, extending into New Mexico, and a
willingness to work cooperatively with the many diverse partners and
personalities who call the watershed home.
The Gila Watershed Partnership works collaboratively with
community members, local, state and federal entities to conserve, restore and
protect our water quality and water quantity. We use a wide range of tools to
accomplish our mission, including research, planning, education, and
on-the-ground projects.
Our mission is to improve watershed health and water quality
of the Upper Gila River through locally led efforts.
The
Character of the Watershed
The Gila Watershed Partnership is comprised
of that part of the Upper Gila River Watershed from Coolidge Dam to the
Arizona-New Mexico border. The watershed covers about 6,000 square miles, of
which 17 percent is privately owned and the remainder is under the stewardship
of state, federal and tribal governments. Mining, ranching, and agriculture are
the principle industries in the Gila Watershed Partnership. These activities
provide important economic resources for the region and are potential sources of
environmental concern.
The
watershed consists of rugged mountain ranges, broad intermountain plains, and
flat, gentle valleys. The elevation of the area ranges from 2,600 feet to 11,000
feet above sea level. The climate above 7,000 feet ranges from cool to sub
humid, and annual precipitation approaches 20 inches. Vegetation is dominated by
Ponderosa pine and pinon/juniper. In contrast, the valleys are arid with annual
precipitation of only 9.5 inches. Dominant vegetation is desert scrub or desert
grassland. Most rain falls during summer thunderstorms resulting in intense,
localized runoff. Winter rains are generally gentle, but can result in heavy
runoff once the soil becomes saturated.
Originating in the Gila National Forest of New Mexico, the
waters of the Gila River flow west through Arizona and eventually reach the Gulf
of California. Although the Upper Gila River and some of its tributaries are
perennial, many tributaries are ephemeral. The ephemeral streams can be fast and
free flowing during the rainy season, yet carry no water during the dry period.
Although the Coolidge Dam marks the separation of the river into the upper
region to the east, and the remaining lower sections to the west, it has no
affect on the flow variability in the watershed.
The majority of the surface water comes from
precipitation, predominantly snow pack from the many mountain ranges. The
volatility of the region is occasionally seen in flash flooding and torrential
rains.
The valleys of the Gila River and its
principle tributary, the San Simon River, are made up of alluvial materials up
to several thousand feet thick. A coarse, 100-foot thick, highly permeable
aquifer lies under and along the river proper. Beneath this recent alluvium is a
finer grained material with locally concentrated salt (evaporite) deposits.
Natural subsurface flow through the aquifer systems transmits salts to the Gila
River, consequently increasing salinity in the water column; salinity levels are
a major concern for water users in the Gila Watershed.
The population in the Gila Watershed
Partnership is above 40,000 persons with about 50% residing in the town of
Safford. Other major towns in the Gila Watershed Partnership are Duncan,
Thatcher, and Pima. Additionally, Bylas and San Carlos are the principle towns
on the San Carlos Apache Reservation.
The Upper Gila River and tributaries support
a myriad of life in a vast area. The meandering river brings the juxtaposition
of the mountains and the desert together. While providing habitat and resources
for numerous animals, the watershed also affords ample opportunity for people.
Although not visible at all times, the sight of riparian areas and agricultural
fields attests to the presence of water.
The Gila
Watershed Partnership Plan & Projects
The goals of the partnership are to conserve
natural resources, enhance the environment for all users, maintain or improve
the local economy, increase recreational opportunities, increase water quantity,
improve water quality and to plan and act to avoid and minimize damage from
large storms, floods, and other natural disasters.
The Gila Watershed Partnership has worked with our partners to
accomplish many critical projects. These projects include:
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The Safford Water Project
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The Bellman Well Sealing
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The Hackberry Ranch Roads Project
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The San Simon Sediment Control Project
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The Fluvial Geomorphology Study
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The Aravaipa Creek Project
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The Lebanon Dam Project
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The Willow Flycatcher Project
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The Thatcher Hot Well Project
Our partners include:
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Graham County
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Greenlee County
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City of Safford
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Town of Thatcher
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Town of Pima
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Town of Duncan
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Town of Clifton
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Bureau of Land Management
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AZ Dept.of Environmental Quality
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Arizona Department of Water Resources
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Arizona State Land Department
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Coronado RC&D
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USDA Natural Resources Conservation
Service
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Arizona Geological Survey
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Gila Valley NRCD
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Gila Resources
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Discovery Park
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Gila Valley Irrigation District
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Farm Bureau
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U.S.Fish and Wildlife Service
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University of Arizona Cooperative
Extension
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U.S. Forest Service
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Phelps Dodge Mining Company
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Arizona Department of Agriculture
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Arizona Department of Transportation
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Arizona Game and Fish
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Arizona Cattlegrowers Association
Safford Basin
The Safford basin is located in southeastern Arizona and
covers approximately 4,854 square miles in both the Basin and Range and Central
Highlands physiographic provinces. The basin is divided into the San Simon
Valley, Gila Valley and San Carlos Valley sub-basins. The basin generally
forms an elongated valley bounded by the Chiricahua, Dos Cabezas, Pinaleno and
Santa Teresa Mountains to the southwest, and the Peloncillo and Gila Mountains
to the northeast. Elevations in the basin vary from 10,713 feet above mean
sea level at Mount Graham, to 3,000-4,000 feet above mean sea level on the inner
mountain valley floors, to about 2,400 feet above mean sea level at San Carlos
Lake. The southern part of the basin slopes gently to the northwest and is
drained by the Gila and San Simon Rivers. The northern portion of the
basin includes much of the San Carlos Indian Reservation which is drained to the
south by the San Carlos River.
The Safford basin is a large trough-like depression formed
by elongated mountain ranges which rim a broad alluvial-filled valley. The
mountains are composed of gneiss, schist, granite, volcanics, and sedimentary
rocks. The valleys are filled with erosional remnants of these mountains.
The major aquifer in each of the three sub-basins is found in the alluvial fill;
however, differing physical and chemical characteristics exist in each.
San Simon Valley Sub-Basin
White (1963) divided the alluvial fill into two major units:
the younger and older alluvium. The younger alluvium consists of the most
recent stream deposits found along the major stream courses. The older
alluvium represents the majority of the basin-fill material and is composed of
interfingering beds and lenses of clay, silt, sand and gravel. The older
alluvium, as described by White, also contains a dense clay deposit (referred to
as the Blue Clay unit) which may reach up to 600 feet thick. This unit
marks the top of the older alluvium and separates the upper and lower aquifers.
Groundwater, in general, is found under water-table conditions in the upper
aquifer and under artesian conditions in the lower aquifer.
Prior to development, groundwater movement generally
followed surface-water patterns. Since the early 1950’s, when pumpage
increased dramatically, groundwater movement has been toward areas of intense
pumpage near farming centers. Declines in water levels are greatest in
these areas. Barnes (1991) found maximum declines in the lower aquifer of
up to 211 feet near Bowie from 1962-1987, and declines of up to 100 feet common
around much of the sub-basin. In the southern part of the sub-basin,
groundwater bevel changes ranged from a rise of 15 feet to a decline of 15 feet
over the same period.
Water levels as reported by Barnes (1991) in the upper
aquifer for 1987 ranged from 30 to 150 feet below land surface, and discharge
from wells varied from 75 to 300 gallons per minute. In the lower aquifer,
water levels range from less than 100 to 500 feet below land surface and large
irrigation wells yield 500 to 2,000 gallons per minute. Water quality is
variable across the sub-basin but generally, the upper aquifer contains high
total dissolved solids and fluoride (Barnes, 1991).
Gila Valley Sub-Basin
Halpenny and Cushman (1947) divided the basin-fill into two
units, consisting of the younger and older alluvium. The younger alluvium
consists of clay and unconsolidated silt, sand, and clay occurring in
discontinuous lenses. The thick blue clay layer generally marks the bottom
of the unit. The older alluvium consists of weakly-consolidated layers of
clay, silt, evaporates and conglomerate. The principal aquifer in the Gila
Valley is the younger alluvium found along the inner and tributary valleys;
however, groundwater occurs in both the younger and older alluvium.
Water levels in the sub-basin mainly are controlled by
recharge from the Gila River. There has been little change in water levels
since groundwater first was developed. Most recharge comes from the Gila
River; smaller amounts are contributed by mountain-front recharge and seepage of
irrigation water. Freethey and Anderson (1986) estimated that, prior to
development, as much as 16,000 acre-feet per year entered the sub-basin as
groundwater underflow from the Bonita Creek and Duncan Valley basins.
Groundwater in the younger alluvium is found under
water-table conditions. Average discharge from wells is 1,000 gallons per
minute, but discharges of 2,500 gallons per minute have been reported (Black,
1991). The older alluvium generally is found under artesian conditions and
well discharges may reach 660 gallons per minute. Groundwater in the
younger alluvium generally is high in total dissolved solids which partially may
be attributed to infiltration of irrigation water. Groundwater in the
older alluvium also is high in dissolved solids because of the existence of
evaporite deposits. The Safford area has significant nitrate contamination
of the groundwater (Arizona Department of Environmental Quality, 1990).
San Carlos Valley Sub-Basin
As reported by Brown (1989), most groundwater development in
the San Carlos sub-basin is along the Gila and San Carlos Rivers where the
younger stream alluvium makes up the main water-bearing unit. Stream
alluvium consists of mainly unconsolidated sand and gravel and may be up to
100-feet thick. Basin-fill consists of sand, silt, limestone, clay, and
volcanics up to 3,200 feet thick. Wells tapping the stream alluvium and
the upper part of the basin-fill may yield
900 gallons per minute or more. In the northern part
of the sub-basin groundwater development is limited to a few stock wells which
yield less than 50 gallons per minute from volcanic rocks.
Several public-supply wells are operated by the City of
Globe in the western portion of the sub-basin about one mile west of the San
Carlos Indian Reservation. The U.S. Geological Survey (1989)
reported a water-level decline of 170 feet between 1974 and 1987 in one well
located in Section 9, Township 1 South, Range 16 East.
Areas of greatest development along the Gila and San Carlos
Rivers have, in some cases, seen a rise in water levels in response to large
surface water flows (Brown, 1989). Water quality generally is good and
suitable for most purposes; however, stream alluvium along the Gila River
contains large concentrations of total dissolved solids and arsenic levels above
the Federal drinking water standards in localized areas (Brown, 1989).
Duncan Valley Basin
The Duncan Valley basin is located along the eastern border
of Arizona with New Mexico and covers about 550 square miles in Arizona.
This area is part of the Basin and Range physiographic province and is made up
of an elongated valley surrounded by the Peloncillo Mountains to the west and
the Big Lue Mountains to the east. The Gila River runs through the basin
from the southeast to the northwest. Elevation varies from 6,571 feet
above mean sea level in the Peloncillo Mountains to 3,336 feet above mean sea
level at the downstream end of the Gila River.
The Duncan Valley basin is made up of an elongated valley
filled with water-bearing sediments and surrounded by generally impermeable
rocks. The water-bearing sediments are broken into three units. In
descending order they include: the younger alluvial deposits, the Gila
Formation, and the older basin-fill (Remick, 1989 after Morrison, 1965).
The younger alluvial deposits, the principal source of groundwater in the basin,
consist of gravel and sand generally underlain by clay. The alluvium is
found along the Gila River and its tributaries where the thickness varies from
one to 170 feet, Many wells also tap the Gila Formation which consists of poorly
consolidated sand, silt, and gravel deposits and a fanglomerate zone. The
older basin-fill consists of alluvium, tuff and volcanic conglomerate.
Only minor amounts of groundwater issue from the basin-fill.
In general, water levels and groundwater movement in the
Duncan Valley basin are controlled by the Gila River. Groundwater and
surface water generally moves from southeast to northwest across the state line
from New Mexico into Arizona. In 1987, depth to water in wells ranged from
less than 10 feet below land surface along the Gila River to 600 feet below land
surface near the mountains (Remick, 1989). No significant changes in water
levels have been observed since 1939 when the first measurements were made in
the basin. Using 1939 data, Halpenny and others (1946) estimated underflow
from New Mexico to be 7,200 acre-feet per year and recharge from washes to be
approximately 7,000 acre-feet per year. Underflow out of the basin was
estimated to be 350 acre-feet per year.
In 1985, just over 5,000 acre-feet of groundwater were
pumped from the basin (Arizona Department of Water Resources, 1988).
Remick (1989) reports well-yields from the younger alluvium ranging from 350 to
2,350 gallons per minute and from the Gila Formation ranging from a few to 200
gallons per minute. Well-yields from the mountains and bedrock are only a
few gallons per minute. Approximately 19.0 million acre-feet of
groundwater are in storage to a depth of 1,200 feet below land surface (Arizona
Department of Water Resources, 1988); groundwater quality generally is good with
dissolved solids concentrations ranging from about 100 to 2,150 milligrams per
liter (Remick, 1989).
Morenci Basin
The Morenci basin covers approximately 1,645 square miles of
the Central Highlands physiographic province in eastern Arizona and is
characterized by steep-walled canyons, mesas, buttes and peaks. The basin
is bordered by the Arizona-New Mexico state line to the east and stretches from
the fringes of the Colorado Plateau in the north to the Gila River in the south.
Elevation ranges from over 10,900 feet above mean sea level on Escudilla
Mountain to about 3,400 feet above mean sea level at the confluence of the San
Francisco and Gila Rivers.
The Morenci basin, unlike most of the rest of the Central
Highlands province, consists mainly of rhyolite and agglomerates capped by
basalt flows. Much of the topography is dissected by streams and washes
which flow mainly in response to rain and melting snow. A small
percentage, possibly ranging from as little as 1 - 7% (Feth and Hem, 1963), of
the precipitation falling on the area infiltrates the fractured basalt landscape
and appears as spring flow. There are many springs in the basin, most of
which discharge less than 100 gallons per minute. One spring, about 10
miles northeast of Clifton, discharges around 200 gallons per minute (Mann,
1980). Most springs issue from the contact between basalt flows or
underlying silt and clay deposits. Insufficient data exists to determine
whether a continuous groundwater system exists or if the area is made-up of
several discontinuous systems. Alluvial and floodplain deposits along the
San Francisco and Blue Rivers are probably hydraulically connected.
Groundwater development in the basin has been slight, with
most wells tapping alluvial deposits along the major stream courses.
Approximately 8,800 acre-feet of groundwater were pumped in 1985 (Arizona
Department of Water Resources, 1988). Mann (1980) reported depth to water
in wells to be generally less than 30 feet below land surface. Most wells
and springs also were reported to contain less than 500 milligrams per liter of
dissolved solids and between zero and 0.9 milligrams per liter of fluoride; both
of which are within drinking water standards. The amount of groundwater in
storage is unknown but is believed to be relatively small because of the
geologic characteristics of the basin.
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