WSP04263

• File Number: 8507
• Description: Rio Grande Project
• State: CO
• Basin: Rio Grande
• Date: 1/1/1957
• Title: Symposium on Problems of the Upper Rio Grande
• Water Supply Pro - Doc Type: Report/Study

.~

SALT CEDAR CONTROL AND CHANNELIZATION
IN THE SAN MARCIAL AREA OF THE
MIDDLE RIO GRANDE IN NEW MEXICO

i
~ .,
,,:....i
,,:;s.1

by

E. W. ELLIOTT

Chief, Operations, Maintenance, and Drainage Division
Middle Rio Grande Project, Bureau of Reclamation,
U. S. Department of the InteriOf, Albuquerque, New Mexico

,

,;-.i

:.'<

The San Marcial Swamps area is located immedi-
ately upsheam and partially within the upper limits
of Elephant Butte reservoir. Within this area great
quantities of river water have been lost each year
thfOugh nonbeneficial use by vegetation.
The Middle Rio Gmnde Pwject Office of the Bu-
reau of Reclamation was established in the fall of
1950 to prepare definite plans and to construct
wmks covered by pwject authorization. The first
work undertaken was the San Marcial Channelization
as an emergency measure to help relieve the serious
water shmtage pwblem in the Rio Grande Basin.
The area involved is appwximately 35 miles long
and ranges fwm three quarters to two miles wide and
was covered by a heavy gfOwth of mixed phreato-
phytes consisting of salt cedar, willow, baccharis
and cottonwood. The majority of this vegetation was
estimated as having a density of nearly 100%. Chan-
nels as existed meandered through this swamp with
great difficulty and were partially blocked at inter-
vals by dense growths of native vegetation, causing
most flows to spread over virtually the entire area.
This created a very favorable condition for growth of
phreatophytes and heavy loss of water thfOugh plant
use and evaporation. Water table conditions during
most of the year were at or very near the ground
surface.
The estimated losses of river flows in the reach
between San Antonio and the average water surface
of Elephant Butte under conditions pfior to channel-
ization were approximately 145,000 acre-feet an.;.
nually.
The first emergency corrective work in the San
Marcial Swamps was done in the summer of 1951 and
consisted of construction of four small temporary
drainage channels through the dense growths of
native vegetation to connect existing river channels.
This construction was done by the Middle Rio Grande
Conservancy Distdct with funds advanced by the
State of New Mexico and by the hdgation districts.
below Elephant Butte. ThfOugh this it was possible
to drain the majority of standing water and accom-
plish some limited salvage of ground water.
In December 1951, the first 22 miles of the emer-

;)

;1

,
..,

gency channelization by the Bureau of Reclamation
was started under contract to McGinnis Bros. of
Houston, Texas. The second contract let subse.
quently for the balance of the work was performed by
List and Clark, Kansas City, Missoud. Plans for
the channelization pwvided for a 2,000-c.f.s. low
flow conveyance channel and levee and a 1,000- to
1,40o-foot-wide cleared floodway. The main con-
veyance channel, as constructed, has a 32-foot
bottom width, average depth of about 10 feet, side
slopes ranging from 2:1 to 4:1. A diversion head-
works is located at the upper end of the conveyance
channel for control of flows entedng the channel-
ization. The levee to form the west side of floodway
was constructed east of the channel of material from
excavation and provides a berm and 50-foot main-
tenance access road the entire length of the job.
All vegetation except a 50-footlbrush fringe along the
,
constructed. levee was cleared by dozers and dis-
posed of by blUning.
Excavation of the main conveyance channel was
accomplished pdmadly with 6-cubic-yard draglines.
The first phase of construction between Nogal
Canyon and San Marcial Lake was completed in May
1953. The second and final reach of emergency
channelization between San Marcial and the Fish
and Wildlife Refuge was completed in May 1954.
The total cost of all the San Marcial Channel-
ization construction, including maintenance head-
quarters and equipment fm 0 & M, is appfOximately
$ 3,000,000.

Flow duration curves showed that a channel of
2,000 c.f.s. capacity would cauyall flows 82% 'or-the
time and the flood way necessarily would handle the
flow for the balance of the time. Estimated water
losses under the plan are 103,000 acre-feet annually
which represents a salvage of 42,000 acre-feet by
comparison with previous losses. It is estimated
that total water savings to May 1955 amount to about
138,000 acre-feet. We estimate that at least 40,000
acre-feet will be saved annuaily so long as the
works are maintained.
With the completion of the San Marcial channel-
ization works, we were immediately faced with the

33

." ; r\;' (' "
V'...I~...U.L