General Description
The Colorado River Front Work and
Levee System extends from Lees Ferry, Arizona, the division point
between the Upper and Lower Colorado River Basins, to the Southerly
International Boundary between the United States and Mexico, a
distance of about 700 river miles. Its purpose is to control floods,
improve navigation, and regulate the flows of the Colorado River.
The work consists of constructing, operating, and maintaining the
Colorado River Front Work and Levee System in Arizona, California,
and Nevada; it includes controlling the river, improving, modifying,
straightening, and rectifying the river channel, and conducting
investigations.
The lower Colorado River extends about 280 river miles from Davis
Dam to the boundary, and traverses three wildlife refuges, five
Indian Reservations, and six irrigation districts. For administrative
purposes, this reach of the river has been divided into 10 operational
divisions. These divisions, starting at Davis Dam and proceeding
in order downstream, are: Mohave Valley, Topock Gorge, Havasu,
Parker, Palo Verde, Cibola, Imperial, Laguna, Yuma, and Limitrophe.
Major project facilities include the off stream Senator Wash Dam
and Reservoir, a pumping plant, access roads, water crossing facilities,
and flood control levees. Regulation of river channel meandering
by use of bankline structures with riprap protection, or a riprap-protected
dredge channel, has been provided for the Mohave Valley, Upper
Parker, Palo Verde, Cibola, and Yuma Divisions. Settling basins
for trapping sediment have been built upstream from Topock Bridge
and Laguna Dam. Salinity control features include the Main Outlet
Drain (MOD) and the Main Outlet Drain Extension (MODE). These features
convey the drainage flows from the Wellton-Mohawk Main Conveyance
Channel (Drain) to the Bypass Drain below Morelos Dam. The Gila
River Pilot Channel was constructed to convey return flows from
the irrigated lands in the Lower Gila River Valley to the Colorado
River.
Water salvage activities along the Lower Colorado River include
controlling the size of open water areas, selective clearing of
phreatophytes, draining the river valley, and establishing deeper
backwater areas. Major ground-water recovery programs have been
undertaken by development of well fields and conveyance systems
in the South Gila and Yuma Valleys, and on the Yuma Mesa.
Fish and wildlife features have been enhanced and wildlife losses
have been mitigated by the development of Topock Marsh, Deer Island
and other backwater improvements, Cibola Lake, and Mittry
Lake. Park Moabi, McIntyre Park, Welters Camp, Laguna South
recreation area, and several marinas have been developed for recreation
purposes.
Plan
This multiple-purpose program includes
control of sediment movement, protection of communities and transportation
facilities, maintenance of agricultural land by controlling the
bed and banks of the river, and preservation and enhancement of
the fish, wildlife, and recreation resources of the area. Channel
alinement rectification, control structures, levees, revetment,
and flood control levees are used to confine the river to the designed
channel during variations of discharge.
Unit descriptions and facilities
Mohave Valley Division
The Mohave Valley Division is located on the reach of the
Colorado River from Davis Dam to Topock, Arizona. The area through
which the river flows is an alluvial valley from 2 to 5 miles wide.
It traverses the Fort Mohave Indian Reservation and that portion
of the Havasu National Wildlife Refuge that lies upstream from
Topock. Prior to the channelization program, there was a wide meandering
of the river accompanied by general aggradation of the valley floor.
The definable channel in the lower part of the valley was almost
lost and the river flowed through a series of swamps and sloughs.
Stabilization was initiated in 1949 by dredging to improve a channel
between Needles and Topock. This work was completed January 5,
1953, and, along with associated levee construction, minimized
the immediate flooding threat to Needles, California.
In January 1953, channel dredging, levee construction, and associated
work were initiated on the reach of the river from Needles upstream
to the Big Bend, 10 miles below Davis Dam.
Riverflows in the Mohave Division average 15,000 cubic feet per
second in the summer and 7,000 cubic feet per second in the winter.
The average depth of the channel during dredging was about 18 feet
below the water surface at a flow of 15,000 cubic feet per second.
Maximum depth dredged was about 25 feet. The average design width
is about 450 feet.
The total dredge excavation in the Mohave Valley Division was
52,531,728 cubic yards. The total borrow for riverbanks, structures,
and levees was 26,602,055 cubic yards. The design floods for levee
construction in this reach of the river are: 50,000 cubic feet
per second downstream of Davis Dam to Piute Wash, and 70,000 cubic
feet per second downstream of Piute Wash.
Topock Marsh Water Control Facilities--Mohave Division
Topock Marsh is located on the Arizona side of the Colorado
River midway between Davis Dam and Parker Dam. The northern portion
of the marsh lies opposite Needles, while the southern extremity
connects with the Colorado River at Topock. The marsh is almost
entirely in the Havasu National Wildlife Refuge, which was established
in 1941. Topock Marsh was created by backwaters resulting from
the construction of Parker Dam.
Features constructed by the Bureau of Reclamation in Topock Marsh
consist of inlet and outlet structures, a canal, and dikes. These
structures make possible the maintenance of optimum water surface
elevations in the marsh and permit diversion of water to the marsh
from the Colorado River.
The Topock Marsh Dike was constructed with a crown elevation of
460.0 feet. It impounds a water surface area of 4,000 acres. The
materials to construct the dike were excavated by dredge from the
bottom of the marsh. The highest portion of the fill rises 14 feet
above the bottom of the marsh. A section of the fill northwest
of the outlet structure was constructed to elevation 459.0. The
purpose of this special section is to localize and control damage
which would result from floods on the local drainage area or on
the river itself.
Topock Gorge Division
The Topock Gorge Division starts at Topock, Arizona, and
extends downstream to Lake Havasu, a distance of about 12 miles.
After the closure of Parker Dam in 1938, the rise in water surface
elevation (adjusted to a standard flow of 15,000 cubic feet per
second) was accelerated and increased from 443 feet to nearly 452
feet by 1948. During correction of the high water conditions which
existed at Needles prior to 1951, it was recognized that sediment
deposits in the Topock Gorge were an important factor leading to
the high water levels that existed from Topock north beyond Needles.
Havasu Division
The Havasu Division covers all of Lake Havasu and the
river between Parker and Headgate Rock Dams.
A navigational hazard of submerged trees existed in Lake Havasu
because the reservoir area was not cleared prior to closure of
Parker Dam in 1938. In recent years, developments along the Colorado
River have attracted thousands of visitors to Lake Havasu, with
boating and water skiing replacing fishing as the dominant recreational
activity. A number of accidental deaths have occurred on the lake.
In several instances, the snags were a factor in the accident.
Snag removal operation, begun in 1965 with underwater cutting,
clearing, and disposition of tree snags from boating areas on Lake
Havasu, was accomplished under three separate contracts. The final
contract was completed in 1971.
The design flood downstream of Parker Dam for this division is
50,000 cubic feet per second.
Parker Division
The Parker Division begins at Headgate Rock Dam and extends
downriver about 33 miles to the Palo Verde Diversion Dam.
The channel throughout this reach has been subjected to scouring
action by clear water releases from Parker Dam. Headgate Rock Dam,
constructed for the Bureau of Indian Affairs by the Bureau of Reclamation
in 1942, stabilized the channel below the dam. The area is protected
from floods by the levee system built in conjunction with the construction
of the Palo Verde Diversion Dam.
The plan of development divided Parker Division into two sections.
Section I lies within the Colorado River Indian Reservation and
extends about 16 miles downstream from Headgate Rock Dam to Alligator
Bend. Section II embraces the river from Alligator Bend to Palo
Verde Diversion Dam, a distance of 28.3 miles. The Arizona side
and the northern part of this section that is in California lie
within the Colorado River Indian Reservation.
Stabilization of the river in section I was accomplished by confining
reaches of the river between training structures or stabilized
bank lines. The basic channel improvement work was completed in
1967.
In 1969, a comprehensive plan for channel stabilization in section
II was approved by the Department of the Interior. However, the
work was deferred pending the location of the western boundary
of the Colorado River Indian Reservation. In 1971, a task force
appointed to review the River Management Program recommended that
additional plans for the Parker Division below Alligator Bend be
considered to reduce the environmental impact of the work. Several
alternative plans involving a reduced program were evaluated but
none have been adopted . In the early 1990´s a plan
was developed again and implemented. It included bankline
armoring as well as the placement of training structures and jetties. In
addition to the river work a backwater was created at Aha Quinn
with two new channels created by dredging and a third channel in
an existing drain was cleaned out. The completion of this
work contributed significantly to the reduction of sediment originating
from the Parker II Division.
The design flood for this area is 50,000 cubic feet per second
.
Palo Verde Division
The Palo Verde Division includes about 28 miles of river
channel between Palo Verde Diversion Dam and Taylor's Ferry. Channelization
by land-based equipment began in May 1962 and, except for routine
maintenance and repair of constructed features, the channel stabilization
was completed in September 1968. The work consisted primarily of
earthfill training structures and bank protective riprap designed
to prevent future meandering of the river. Many of the backwater
areas created by the training structures were improved to benefit
fish and wildlife.
The Bureau of Reclamation also participated in the development
of the Blythe Marina and McIntyre Park. Both are administered by
Riverside County, California. Dredging of the Blythe Marina began
in June 1966 and was completed in February 1966. A 10-inch dredge
was moved to McIntyre Park in July 1972 where it was used to deepen
the backwater for recreation purposes. This work was completed
in December 1972.
In addition to providing channel stability and 10,000 acre-feet
of annual water salvage, the completed river stabilization work
resulted in a reduction of the sediment load originating in the
Palo Verde Division, thereby reducing the amount of material carried
downstream.
The design flood for this section of the river is 75,000 cubic
feet per second.
Cibola Division
The Cibola Division adjoins the Palo Verde Division at
Taylor's Ferry and extends downstream about 24 miles to the Adobe
Ruin gage at the lower end of Cibola Valley,
Prior to any Reclamation activities in the area, the channel through
this division was characterized by a transition from degradation
at the upper end to aggradation at the lower end, resulting from
the adjustments that had taken place since construction of the
storage dams upstream. The river had acquired a sizable sediment
load in passing through the Parker and Palo Verde Divisions and
the erosive force of the flow was reduced greatly by the time it
arrived at the upstream end of this division. Immediately
following the closure of Parker Dam, a balance point formed near
the mouth of the Palo Verde Drain, with degradation above and aggradation
below. The aggradation conditions caused a rise in the water
surface in the Palo Verde Drain, thus raising the groundwater table
through the lower third of the Palo Verde Valley.
The Bureau of Reclamation provided some relief to this situation
in 1947 by moving the confluence of the river and the drain downstream
about 2 miles. This was accomplished by constructing a pilot
cut across a bend in the river and letting the drain use the old
channel down to the new channel. This cutoff was successful
in dropping the water surface at the drain gage by about 1.5 feet. However,
the pilot cut could not lower the water surface elevations in the
drain enough to completely solve the problem.
Through much of the Cibola Division, the natural channel was shallow
due to sediment deposition. A program to correct channel
deficiencies by dredging and constructing levees was initiated
in 1964 and completed in 1970. The dredged channel begins 2.2 miles
downstream from Taylor's Ferry and ends at the lower end of Cibola
Lake near Adobe Ruins. Major features constructed to preserve
fish and wildlife in the area include the backwater improvement
of the Palo Verde Oxbow Lake south of Palo Verde. Another
area improved for fish and wildlife is Cibola Lake, in the Cibola
National Wildlife Refuge that was established in August 1964.
The work in the Cibola Division provides an estimated 36,000 acre-feet
of water salvage yearly, and has substantially reduced the sediment
passing into the Imperial Division.
The design flood for this division is 80,000 cubic feet per second.
Imperial Division
The Imperial Division extends from the Adobe Ruin gaging
station at the lower end of Cibola Valley to Imperial Dam, The
channel length, including Imperial Reservoir, is about 36 miles.
This division consists of the diversion pool and associated backwater
areas above Imperial Dam. It is the recipient of the sediment
generated in the Parker, Palo Verde, and Cibola Divisions. The
sediment load arriving in Imperial Division is deposited in areas
outside the main channel. About 50 percent is deposited on
sandbars or in backwater lakes. The remainder is diverted
at Imperial Dam. Most of the diverted sediment is removed
from the water by the desilting works in the All-American Canal,
returned to the river below Imperial Dam, and dredged to permanent
dry land storage areas near the Laguna Settling Basin just above
Laguna Dam.
Since closure of Imperial Dam, sedimentation has filled a number
of the backwater areas, particularly in the upper end of the division. Others
have been isolated from the river by natural, river-formed dikes. This
condition is causing serious deterioration of the water quality
and fish and wildlife values in these isolated backwater areas. Generally,
the remaining deeper backwater areas are located in the lower one-third
of the division where the water was initially deeper and sediment
deposition is less advanced. However, a short reach of the
diversion pool immediately upstream from the dam is full of sediment
and it occasionally has been difficult to divert water into the
headworks of the Gila Gravity Main Canal. Some maintenance
dredging has been accomplished immediately upstream from Imperial
Dam to improve these diversions temporarily.
The design flood for this reach of the river is 80,000 cubic feet
per second.
Senator
Wash Dam, Reservoir, and Pumping Plant -- Imperial
Division
Senator Wash Dam and Reservoir, an offstream pumping facility,
is located about 18 miles northeast of Yuma, Arizona, on the California
side of the Colorado River 2 miles upstream from Imperial Dam and
at the river-end of Senator Wash. The purpose of this strategic
off stream retention reservoir is to improve water scheduling of
the Colorado River, with resulting salvage. This is accomplished
by storing part of the riverflow upstream of Imperial Dam when
it is not needed and releasing it to the river for downstream use
when needed since 3 days are required for water released at Parker
Dam to reach Imperial Dam.
The principal features are an earth dam, three dikes, a spillway,
an outlet works, a pumping plant, a switchyard, and access and
service roads. A 69-kilovolt transmission line, about 18
miles long, constructed separately by the Parker-Davis Project,
is now operated and maintained by the Western Area Power Administration
of the Department of Energy.
Senator Wash Dam is a three-zone rolled earth embankment structure
2,342 feet long, with a maximum structural height of 93.6 feet. Squaw
Lake Dike is a three-zone rolled earth embankment structure 3,795
feet long, with a maximum structural height of 95.3 feet. North
Dike is a two-zone rolled earth embankment structure 613 feet long,
with a maximum structural height of 67.2 feet. A small single-zone
rolled earth embankment structure was constructed in a small saddle
on the right abutment of Senator Wash Dam and is included in the
dimensions for the dam. A 3-foot layer of riprap was placed
on the upstream slope of all the earth embankments. A 24-inch-thick
impervious blanket, extending from the upstream toe of the dam,
was constructed on the floor and slopes of the reservoir to elevation
210.0, the top of inactive storage.
An equalization channel uses the storage capacity of a small isolated
basin behind North Dike.
The outlet works consist of an intake structure, a 10-foot-inside-diameter
concrete conduit, a 6.5- by 10-foot-high pressure gate in a gate
chamber, a 10-foot-inside-diameter steel pipe installed inside
a 15-foot-inside-diameter concrete conduit, an access house, a
concrete-encased steel manifold, and six 54-inch steel branchlines
leading to the pump turbines.
The Senator Wash Pumping Plant is of the indoor type with a reinforced
concrete substructure and steel framed superstructure. Six (including
one spare) vertical-shaft, single-suction, centrifugal, Francis-type
pump-turbines with fixed-vane diffuser-type casings are installed
in the plant. Each pump-turbine is directly connected to a vertical
shaft, 360-revolution-per-minute, synchronous motor-generator designed
to operate either as a motor or as a generator. A 20-ton, fiber-operated
overhead traveling crane is provided for installing and maintaining
the unit. Although originally conceived as a pumping-generating
plant, it was designated as a pumping plant in 1977.
When operating as a pumping plant, each 1,750-horsepower pump
is designed to operate from 31 feet of head to shut-off head and
will deliver not less than 100 cubic feet per second at a total
head of 74 feet while operating at 360 revolutions per minute.
Under normal operations, each unit pumps about 200 cubic feet per
second. Normal starting and stopping of the unit is controlled
from the remote control panel at Imperial Dam, which includes all
the electrical control equipment (switching, alarm, and indicating)
required for remote operation of the pumping plant.
A 17.7-mile, 69-kV transmission line between Gila Substation and
Senator Wash Substation brings power for pumping to Senator Wash,
about 10,000 kVA when all six pumps and all station loads are in
operation.
Laguna Division
The Laguna Division was designated to facilitate the construction
and operation of the Laguna Settling Basin and the appurtenant
channels leading to and from the basin. It includes the 4.7-mile
reach of river between Imperial and Laguna Dams.
The settling basin operation in the Laguna Division was originally
adopted as a result of a general complaint lodged by Mexico that
the United States was reintroducing sediment into the river in
amounts that represented higher concentrations than were present
in the river as it entered the Imperial Dam Reservoir area. At
the same time, it was apparent that water was not available for
sluicing operations of the size and type conducted in the past.
Mechanical removal of the sediment by dredging rectified this situation.
Dredging of Laguna Settling Basin began in 1963 and was completed
in 1965. About 1.2 million cubic yards of material were excavated.
The settling basin operation has been satisfactory and its two
primary objectives, removing the sediment and not wasting deliveries
of water to Mexico during sluicing flows, have been achieved. Dredging
operation in the settling basin will be required on a continuing
basis and new areas eventually will be needed to store sediment
taken from the basin.
Operation of the dredge in Mittry Lake for the development of
a fish and wildlife management area in the Laguna Division was
hindered by extremely heavy tule (bulrush) growth in the area.
Herbicide sprays and burning were used in an effort to prevent
the accumulation of extensive floating mats of the growth; however,
mechanical removal was required.
Dredging of the Gila Sluiceway began in 1970 and was completed
in 1973. The purpose of this sluiceway is to carry sediment flushed
from the Gila Main Canal Desilting Basin to the Laguna Settling
Basin.
Yuma Division
The Yuma Division of the Colorado River Front Work and
Levee System includes 21 miles of river channel between Laguna
and Morelos Darns. The
city of Yuma is on the south bank of the river, approximately in
the center of the division. The channel in the Yuma Division reflects
changes resulting from construction of storage dams and diversion
of water for irrigation purposes upstream. It consists of a small
active channel situated within a larger, older riverbed which is
entrenched below the historic level of the unregulated river.
The flow into the upper end of the Yuma Division is regulated
primarily by Laguna Dam. It normally consists of water used to
flush sediment from the desilting works into the Laguna Settling
Basin and from sluice-gate leakage and intermittent sluicing flows
below Imperial Dam. Laguna Dam is used to reregulate the flows
originating at Imperial Dam.
About 9 miles downstream from Laguna Dam, the Gila River enters
the Colorado River from the east. The flow from the Gila River
is the result of returns from canal wasteways, drainage from irrigation
areas, and occasional floodflows, Since 1977, flows from the Wellton-Mohawk
drainage wells, which were frequently discharged into the Colorado
River downstream of Morelos Dam, are now carried to the Santa Clara
Slough in Mexico by the bypass drain.
The California Wasteway of the Yuma Main Canal is about 4 miles
downstream from the mouth of the Gila River, across the river from
Yuma. This wasteway returns to the river the water which is used
to fulfill the United States Water Treaty obligation to Mexico.
Under normal operating procedures, the return through this wasteway
varies from about 20 cubic feet per second gate leakage to about
1,000 cubic feet per second. If flows greater than 1,000 cubic
feet per second are required for release into the river, the water
is transferred for discharge at the Imperial Irrigation District's
Pilot Knob Powerplant.
Rockwood Heading, an old intake structure on the Alamo Canal,
is about 2 miles upstream from Morelos Dam. It is no longer used
for an intake structure but is used as a point of return for the
Pilot Knob Powerplant and Wasteway from the All-American Canal.
The powerplant is operated on a minimum flow of 1,000 cubic feet
per second; the maximum capacity is 8,000 cubic feet per second.
The return to the river at Rockwood Heading may vary between these
minimum and maximum values. About 5 months of the year, there is
no release made at this point because the 1,000-cubic-foot-per-
second minimum flow required by the Mexican Treaty is in excess
of Mexico's water order.
Prior to the completion of the Laguna Settling Basin in 1965,
a comparatively heavy load of sediment was carried by the river
into the upper end of the Yuma Division. The load was caused by
the operation of the All-American Canal Desilting Works and periodic
sluicing of Imperial Reservoir. The Laguna Settling Basin now intercepts
the sediment below Imperial Dam and the trapped sediment is dredged
out of the basin and pumped onto adjacent land. As a result, the
water entering the Yuma Division is relatively sediment-free,
The early history of the Yuma Division shows that lateral movement
of the river occurred infrequently. A major channel change occurred
in 1920 and created what is commonly known as Yuma Island. Located
about 3 miles northeast of Yuma, the island is a flood plain partially
encircled by the pre-1920 river channel. This channel is filled
with sediment except for the two small depressions which constitute
Haughtelin and Bard Lakes.
The completion of Imperial Dam had an immediate effect upon the
river in the Yuma Division. The reservoir behind the dam was comparatively
small; however, it retained much of the sediment picked up downstream
from Parker Dam and relatively clear water flowed through Laguna
Dam into the upper reach of the Yuma Division.
This caused severe scouring action and degradation downstream
from Laguna Dam. The degradation was most severe immediately following
the closure of Imperial Dam but diminished as the reservoir silted
up and the sediment concentration in the water passing Imperial
Dam increased. By 1945, the sediment concentration in the flow
diverted at Imperial Dam for irrigation purposes had increased
to an objectionable level, and the desilting works for the All-American
Canal were placed in operation. The sediment returning to the river
from the desilting works increased the sediment concentration in
the water below Imperial Dam to such proportions that degradation
ceased, except for occasional scour. By 1947, the channel below
Laguna Dam had degraded from 3 to 6 feet down to Yuma, and 5 to
8 feet downstream from Yuma. From 1947 to 1953, the channel remained
relatively stable; with the generally lower flows since 1953, the
channel has been slowly aggrading.
Sediment samples have been taken by the International Boundary
and Water Commission at the Northerly International Boundary since
1956. Since the completion of the Laguna Settling Basin in 1965,
the average sediment load arriving at this station has been 143,000
tons annually for normal flows.
Protection from flooding in the low-lying valley lands has been
provided throughout most of this division by an arrangement of
levees which were constructed during the early activities of the
Colorado River Front Work and Levee System and rehabilitated in
1951 and 1952 under international agreement subsequent to the Mexican
Water Treaty of 1944.
During the rehabilitation of the Yuma levee system, the Upper
Reservation Levee was relocated parallel to the river channel as
it existed. This change reestablished the levee closer to the active
channel of the river and left a fairly large area of land between
the 1905 alinement of the levee and the relocated levee.
Studies conducted in 1948 by the International Boundary and Water
Commission, the Corps of Engineers, and the Bureau of Reclamation
established a design flood for use in the lower river. The flows
accepted were 103,500 cubic feet per second from Imperial Dam to
the mouth of the Gila River and 140,000 cubic feet per second below
the mouth of the Gila River. Additional studies were made by the
International Boundary and Water Commission concerning the effect
of Morelos Dam on upstream water stages as related to levee design
in the Yuma Division. The existing levee system in the Yuma Division
was designed using the data from these studies.
The effectiveness of the present levee system is influenced by
sediment disposal below Morelos Dam. The dredged spoil excavated
from the Alamo Canal and deposited in the flood plain below Morelos
Dam has constricted the channel to the extent that it, rather than
the dam, has often controlled upstream water stages. Normal channel
flows have been affected only temporarily, as there have been either
occasional periods when normal flow below Morelos Dam was adequate
to reopen the channel or the channel was reopened by a special
flushing flow. However, these flows have removed sediment principally
from the active channel and, except for the use of bulldozers to
move sediment deposits into the river during the special flushing
in 1960, they have not removed an appreciable amount of spoil from
overbank areas. As a result, the spoil has continued to accumulate
in the overbank areas between the flood levees.
Flood protection is provided for the division by the Reservation
and Yuma Valley Levees. The Reservation Levee protects the lands
to the west of the river from Laguna to the high lands below Yuma.
The Yuma Valley south of Yuma is protected by a levee on the south
and east side of the river from Prison Hill to the Southerly International
Boundary.
The South Gila Levee provides protection to the lands to the south
of the river from the mouth of the Gila River to Prison Hill, and
an extension east along the south side of the Gila to the siphon
of the Gila Gravity Main Canal, where it joins the Gila Levee System
of the Corps of Engineers, gives full flood protection to lands
in the South Gila Valley. The design floods used to establish the
required levee heights are for a discharge of 103,500 cubic feet
per second from Imperial Dam to the mouth of the Gila River and
140,000 cubic feet per second downstream of the mouth of the Gila
River,
The need for an improvement of the drainage of both Indian and
non-Indian lands in the Reservation Division has long been recognized.
Representatives of both the Quechan Tribal Council and the Bureau
of Indian Affairs have indicated that such improvement work would
be practicable as the result of the channel improvements currently
proposed. The water table in much of the Bard and Reservation areas
is too high for maximum productivity and efficient utilization
of the agricultural lands.
There are many washes in the area which contribute large quantities
of runoff after rains during certain periods of the year.
The primary outlet for the subsurface drainage water and storm
runoff water from lands in the Bard and Reservation areas is the
Reservation Main Drain. This drain crosses under the Southern Pacific
Railroad, the old highway, and the Yuma Main Canal through culvert
structures which control the drain outlet flows. The outlet flows
have been limited by the invert grades and size of the culverts.
Consequently, under normal conditions the Main Drain has operated
marginally. Significant storm runoff water from the washes in the
area has formed a large lake above the outlet culverts, and some
local flood damage has occurred. The backwater effect has further
aggravated the drainage problems in the upper portions of the area
served by the Main Drain.
Yuma Area Ground-Water Recovery and River Regulation Program-Yuma
Division
In 1962, the Congress appropriated funds for initial investigation
of a plan for ground-water recovery and drainage relief in the
Yuma Valley that would also assist, to a small degree, in regulating
flows in the Colorado River.
The ground-water recovery plan was enlarged in scope to include
the entire Yuma area groundwater basin and to increase the river
regulation aspects. A study was completed and a plan developed
in July 1964. Construction of the first phase, Valley Division,
Conduit No. 1, was initiated in 1965. Mexico objected to the ground-water
program in Yuma Valley on the grounds that it would increase the
salinity of waters delivered to Mexico and replace Colorado River
water entitlement to Mexico with pumped ground water.
As a result of a conference with Mexico on October 12, 1965, the
Bureau of Reclamation revised its groundwater recovery plan in
Yuma Valley. The wells were relocated along the east side of the
valley near the toe of the Yuma Mesa, thereby minimizing interference
by ground-water pumping with the underflow to Mexico. The plan,
as revised, provided for the conveyance of part of the water north
to the Colorado River, and the remainder by Yuma Valley drains
to Mexico at the Southerly International Boundary. Under all conditions,
the plan provided for drainage improvement and substantial ground-water
recovery and river regulation benefits.
To conduct the recovery program with minimum impact upon Mexico,
alternative well locations were studied to determine the feasibility
of relocating the well field on the Yuma Mesa near its western
edge. Because additional drainage in Yuma Valley was badly needed,
six drainage wells were constructed by the Bureau of Reclamation
in addition to the seven wells developed by the Yuma County Water
Users' Association along the eastern toe of the Mesa. The discharge
from these wells is conveyed through a conduit system to the Yuma
Valley Division of the Yuma Project drainage system at the Southerly
International Boundary as part of Mexico's entitlement to Colorado
River water.
South Gila Valley Well Field and Conduit System--Yuma Division
Another segment of the Yuma area ground-water and river
regulating program is the Drain Pump Outlet Channel (DPOC) drainage
system in the South Gila Valley. It consists of 24 drainage wells.
The production of the wells ranges from 3 to 9 cubic feet per second.
The eastern three conveyance conduits, DPOC Nos. 1, 2, and 3, discharge
into the Gila River Pilot Channel, constructed by the Colorado
River Front Work and Levee System in 1961. The western conduit,
DPOC No. 4, discharges the pumped drainage water into the Colorado
River.
The purpose of the DPOC drainage well field is to provide adequate
drainage for the agricultural lands of the South Gila Valley and
return it to the Colorado River to become a part of Treaty water
delivered to Mexico above Morelos Dam. The drainage requirement
has been 55,000 to 65,000 acre-feet per year.
Yuma Mesa Well Field and Conduit Yuma Mesa Division
The Yuma Mesa Well Field is located along the western
edge of Yuma Mesa. It is a segment of the overall ground-water
recovery and river regulation program for the Yuma area.
The ground water recovered from the Yuma Mesa Well Field is collected
in a conduit system and conveyed to a point in the Colorado River
near Yuma.
Integrated into the Yuma Mesa Well Field system are six wells
which were installed in Yuma Valley in 1965. Currently there a
total of seven wells with the last one being installed in 1997. These
wells are located along the western toe of Yuma Mesa and their
discharge is conveyed through concrete pressure pipelines to the
Valley Division drainage system.
The principal functions of the ground-water recovery program are
to recover from the ground-water basin return flows from irrigation
developments in the United States to assist in meeting requirements
for delivery of water to Mexico, to provide some drainage relief
for the Valley Division of the Yuma Project, and to assist in Colorado
River operations by reducing over deliveries to Mexico.
The Yuma Mesa Well Field consists of 12 wells, spaced about 0.5
to 1 mile apart, which have a total capacity of about 100 cubic
feet per second. Each well is gravel packed and contains a 16-inch
stainless steel screen. The depth of the wells ranges from 189
to 286 feet. The conduit consists of 14.7 miles of reinforced concrete
pressure pipe, the diameter of which ranges from 18 inches for
the collector conduits to 66 inches for the main conduit. The average
velocity in the conduit is about 4 feet per second. A baffled outlet
structure was installed at the Colorado River end of the conduit.
Transmission facilities consist of one substation, 2 miles of 34.5-kV
line, and 12.3 miles of 12.47-kV line.
The Yuma Mesa Well Field is operated by remote control from Imperial
Dam by the use of radio signals to actuate the individual pumping
units and monitor the operation through electronic interrogation.
The well field is operated on a 24-hour basis throughout the year.
It is capable of pumping about 40,000 acre-feet of ground water
annually and, in addition, about 9,000 acre-feet of water are pumped
annually from the six Bureau of Reclamation drainage wells developed
in Yuma Valley.
Limitrophe Division
The Colorado River at and downstream of Morelos Dam forms
the boundary between the United States and Mexico. Proceeding downstream
for a distance of 20 miles, the left bank of the river is in the
United States and the right bank is in Mexico. The river has levees
on both sides; the levee on the Mexican side is about 4 feet higher
than the levee on the United States side.
The river conditions prevailing from Morelos Dam to the Southerly
International Boundary are not typical of ordinary river conditions
in that no degradation exists downstream from the dam. In fact,
the gated portion of the structure does not always form the water
surface control that would normally be the case. A downstream plug
of sediment introduced in the channel below the dam sometimes controls
the water surface elevation through the gated structure.
This sediment plug is a result of the operation of the Mexican
dredge in the settlement basin at the head of the Alamo Canal and
the method of disposal of sediment employed by Mexico at Morelos
Dam. The Alamo Canal desilting basin is an overwidth and overdepth
section of the canal that runs generally parallel to the river.
For several years following the completion of Morelos Dam, the
method used to dispose of the sediment was simply to pump it out
of the desilting basin onto the ground between the basin and the
river. Over a period of years, the disposal ground was built up
by the deposition of dredge spoil until finally the sediment could
be pumped no higher and some other means of disposal had to be
found.
At this point, Mexico began pumping the sediment into the river
and along the bank between the Mexican levee and the river. On
occasion, the sediment deposit has deflected the current of the
river against and has severely eroded the United States bank. After
these periods of bank erosion, Mexico has brought its disposal
line across the river on pontoons to deposit spoil on the United
States side and thus return the river to the center of the channel.
This type of operation has held the river away from the United
States levee, but has built up the bed of the river with a sediment
plug consisting of several million cubic yards of material.
The remainder of the river channel from Morelos Dam to the Southerly
International Boundary is choked by sediment carried downstream
from the sediment plug and is in generally poor condition. Because
Mexico customarily diverts as much of the flow of the Colorado
River as is feasible to put into the Alamo Canal, the flow below
Morelos is greatly depleted and the channel has become overgrown
with vegetation. In effect, this has seriously reduced the flood
capacity of the channel and presents a direct threat to the safety
of the Valley Division of the Yuma Project.
The river in the Limitrophe Division is no longer important as
a channel for irrigation water. The inadequacies that have developed
in its capacity to convey floodflows are being corrected by work
presently underway. Because this division of the river is an International
Boundary, all work activity, planning, or construction is coordinated
with the International Boundary and Water Commission.
Operating agency
The Colorado River Front Work and
Levee System is maintained and operated by the Bureau of Reclamation.
Development
History
In its natural state before the
upriver dams were built, the Colorado River experienced serious
seasonal floods during part of the year, intense shortage of water
the remainder of the year, a heavy silt load, and a flow too erratic
to support year-round navigation. Full control of the river required
regulation of the annual discharge by reservoir storage, plus supplemental
downstream works at critical locations to solve localized problems.
Subsequent to the construction of the various dams on the river,
the channel between dams was subjected to severe degradation downstream
and aggradation upstream from a dam. In the wide river bottoms
of Mohave and Cibola Valleys, the river surface was raised by continued
aggradation until the banks were overtopped and swamps of considerable
magnitude were created.
Because of the immediate hazard to the city of Needles, emergency
work was undertaken in 1944 to enlarge the existing inadequate
levees along the Colorado River. The initial channelization work,
Needles to Topock, was aimed at alleviating the flood and high-water
hazard to the city of Needles and the facilities of the Atchison,
Topeka, and Santa Fe Railway Company in Mohave Valley .
At Pale Verde Irrigation District's intake, 65 miles downstream
from Parker Dam, degradation had lowered the riverbed to the point
that diversions could not be made satisfactorily. Rock placement
as the initial step in constructing the Pale Verde temporary weir
commenced on January 12, 1945. On June 24, 1945, the first water
was delivered through the district's new headworks upstream from
the weir. Completion of the weir permitted full gravity diversion
to be resumed through the canal system. However, continuing difficulty
made construction of a new diversion facility necessary.
Investigations
Investigations by the Bureau of Reclamation revealed
the need for a concerted, continuing project for an indefinite
period to control the operation of the river efficiently.
Authorization
The Colorado River Front Work and Levee System was authorized
by the acts of March 3, 1925 (43 Stat. 1186, 1198), January 21,
1927 (44 Stat. 1010, 1021), July 1, 1940 (54 Stat. 708), and the
act of June 28, 1946 (60 Stat. 338), Public Law 79-469, as amended
by the act of May 1, 1958 (72 Stat. 101).
Construction and Dredging
Yuma
Area Dredge
Mohave Division - Enlarging the existing levees
along the Colorado River commenced in 1944. The initial channel
stabilization, levee construction, and associated work, Needles
to Topock, commenced in 1949 and was completed in 1953. Channelization
and levee construction by dredging, Needles to Topock, started
in 1953 and was completed in 1960. The Topock Settling Basin was
constructed by dredging between December 1955 and November 1956.
Dredging of Park Moabi started in 1964 and was competed in 1965.
Work on the main dike of Topock Marsh was initiated in 1965 and
completed in 1966 with the installation of the marsh's inlet and
outlet facilities. Improvement of the Needles Marina was started
in 1967 and completed in 1968. The Big Bend training structure
was constructed between January and June 1969. Improvement of Park
Moabi by dredging was accomplished during December 1971 and January
1972. Fish and wildlife habitat improvement of Topock Marsh started
in January 1974 and was completed in 1980.
Topock Gorge Division - Dredging of the Upper
Topock Gorge began in 1967. However, the dredging was suspended
in 1968 because of the Fish and Wildlife Services' objections.
Havasu Division - Snag removal in Lake Havasu
was accomplished intermittently between December 1965 and June
1971.
Parker Division - Construction of bankline
structures for the Parker Division, Section I, with land-based
equipment, began in January 1966 and was completed in June 1968.
Improvement of Deer Island by dredging began November 1968 and
was completed in May 1969. In the early 1990´s several
training structures were completed as well as eroding banklines
armored with riprap.
Cibola Division - Dredging of the channel and
levee construction of the river between Taylor Ferry to Adobe Ruin
started in June 1964 and was completed in December 1969. Construction
of the lower Cibola Bridge was initiated in June 1969 and was completed
February 1970. The Cibola dry cut was opened March 10, 1970. The
Pale Verde Oxbow was dredged in 1970 and supplemental bankline
work was completed by contract during May 20, 1971, to November
17, 1971. In 1974, dredging the mouth of the old river channel
near Walter's Camp in the lower Cibola Valley was accomplished
and the river bankline structure was extended to narrow the old
river channel and provide boating access to the improved Walter's
Camp recreation area. The Cibola Lake inlet and outlet structures
were built in 1974.
Imperial Division - Starting in 1969, silt
removal activities have been carried on intermittently above Imperial
Dam to relieve the flow into the Gila Canal. Construction of Senator
Wash Dam, Reservoir, and Pumping Plant was accomplished during
1964-1966.
Laguna Division - Construction of the Laguna
Settling Basin, by dredge, commenced in July 1963. The dredging
of the settling basin was accomplished in April 1965. Construction
of a freshwater inlet channel to Mittry Lake, dredging Mittry Lake,
and the Gila Sluiceway started in 1970 and was completed in 1973.
Yuma Division - Raising of Yuma Levees and
construction of the Reservation Levee began in May 1951 and were
completed in September 1952; dredging of the channel relocation
was completed in 1954. Construction was started on the Main Outlet
Drain and the Gila and South Gila Levees in 1960 and completed
in 1962. Construction of the Valley Division Conduit No. 1 and
drainage well field was started in 1965. This drainage well field
was limited to six wells and a collector conduit and was installed
in 1965. The Yuma Mesa Well Field and conduit were constructed
during 1968-1971, and the South Gila Valley drainage wells and
drainage pump outlet channels were constructed in 1964. The Main
Outlet Drain Extension was constructed in 1965. Dredging the river
channel below Laguna Dam was accomplished in 1969.
Benefits
The project has increased irrigation
water supplies through reduction of water loss from evaporation;
improved transportation; enhanced the fish and wildlife and recreation
values of the area; improved navigation and control of diversions;
reduced the silt load in the river; assisted in the control of
floods and salinity; and has provided needed technical information
for future efficient river operation.
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