Americans look to their public forest and rangelands to fill many of
their basic needs for water, food, energy, shelter, and clothing. Demands
for these goods are more intense and diverse than ever before. At the
same time, more and more people turn to public lands for recreation, relaxation,
and educational experiences.
Public land managers must respond to people's needs while maintaining
the quality and productivity of the environment. Consequently, better
ways are being sought to assess and select management practices that will
yield reasonable combinations of products such as wood, water, or livestock
forage; as well as provide other values such as wildlife habitat, scenic
beauty, and recreation opportunities. For example, practices that emphasize
water and forage production may reduce wood supplies and compromise the
quality of habitat for some animals. Emphasizing timber production might
lower scenic beauty, but improve habitat for big game animals.
The goals of the Beaver Creek Program are to provide land managers with:
(1) essential facts about the biological, physical, social, and economic
effects of multiresource management actions in ponderosa pine forests
and pinyon-juniper woodlands; and (2) better ways to predict, display,
and evaluate differences among the probable results of management alternatives
before actions are initiated.
A Cooperative Effort
Many organizations are involved in this program, including several Forest
Service research and management units, other federal and state agencies,
universities, foundations, and private concerns. Their varied skills and
expertise are vital to its success.
In the summer of 1955, several ranchers met with a Forest Service representative
and an officer for the Salt River Project, an organization of water users
in southern Arizona. The ranchers and the water users' agent were concerned
that increasing numbers of trees and shrubs were reducing the flow of
streams and the supply of livestock forage on watersheds in the State.
As a result, the University of Arizona was commissioned to investigate
the potential for improving water yield from the State's forests and ranges.
University findings, titled Recovering Rainfall, better known as
the Barr Report, suggested that surface water runoff from mountain watersheds
might be increased by replacing high water-using plants, such as trees
and shrubs, with low water users, such as grass.
Based on this report, the Forest Service began to test theories for increasing
the flow of mountain streams. By 1960, studies dealing with ponderosa
pine and pinyonjuniper lands had evolved into the Beaver Creek Watershed
Evaluation Program. Its emphasis was to determine how much water yield
could be increased using various methods for altering the vegetation.
Changes in livestock forage, timber production, wildlife habitats, recreational
values, and soil movement also were to be studied.
Similar projects were undertaken by other Forest Service units in areas
of mixed conifer, chaparral, and streamside vegetation elsewhere in Arizona.
Results of studies conducted to date at Beaver Creek, and other locations,
show that changes in plant cover can produce substantial streamflow increases
from some vegetation types, but not all. The impacts of watershed management
practices on other range and forest resources also have been assessed.
Getting the Project Rolling
Between 1957 and 1962, 20 specific watershed study units within the Beaver
Creek area were designated to test the effects of several vegetation management
practices on water yield and other resources. Of the 20, 18 were watersheds
from 66 to 2,036 acres where specific vegetation modifications could be
tested on a pilot basis. The other twoencompassing 12,100 and 16,500
acreswere watersheds set aside to demonstrate the effects of management
practices on areas of the size forest managers work with daily. Recently,
24 smaller watershed units, each having uniform soil, plant life, and
topography, were defined in areas of diverse ecological characteristics.
Information from these units helps refine and verify findingsfrom
studies on the larger watershedsfor use over a wide range of conditions.
Measuring Results of Treatments
Before any vegetation was changed, runoff from each watershed was measured
for several years to determine streamflow variations under pretreatment
conditions. During this time, the quantity and quality of other natural
resources also were inventoried.
With pretreatment measurements completed, six watershedsBar-M and
Watersheds 2, 5, 13, 15, and 18were designated as untreated "controls".
They were shown to respond to environmental influences in a manner similar
to the watersheds where experimental treatments would be applied.
Measurements continue on both experimental and control watersheds for
several years after treatments are applied. Streamflow, sediment production,
and water quality are monitored regularly, and other resources are reinventoried
periodically. Changes caused by the management practices applied to the
experimental units are evaluated by comparing posttreatment values with
pretreatment data and with data from the untreated "control"
Pinyon-Juniper Treatments and Results
The pinyon-juniper experiments were among the first conducted in the
Beaver Creek area. Prior to these studies, many woodland managers thought
pinyon-juniper removal would improve both streamflow and forage production.
Large areas throughout the Southwest had been cleared expecting these
benefits. However, results at Beaver Creek show that substantial forage
increases are possible, but that changes in water yield are not likely
to be significant.
Three techniques were used to remove pinyon and juniper trees from Watersheds
1, 3, and 6uprooting, herbicide spraying, and cutting, respectively.
Herbicide spraying on Watershed 3 was the only treament to yield a significant
streamflow increase. However, the government carefully controls the use
of herbicides for environmental reasons, limiting the general use of this
technique. Mechanical removal, such as uprooting or cutting, is the primary
means for converting pinyon-juniper woodlands to other types of vegetation.
Increased grass is the most noticeable change triggered by pinyon-juniper
removal. However, the cost of removal usually is more than the value of
the livestock forage gained unless the trees can be sold for fenceposts
Pinyon-juniper removal also causes wildlife changes, particularly among
small mammals and birds. For example, birds that feed in trees are replaced
by ground feeders. The predominant game animalthe mule deeris
affected little by tree removal when woodland cover is left not far from
the openings. However, more forage is made available in early spring when
deer often need additional nourishment.
Records from the pinyon-juniper watersheds show that erosion rates and
sediment loads in the streams have varied sharply with the intensity of
storms. A heavy storm soon after the trees were removed from one watershed
washed away much soil. In the long run, however, average sediment loads
from the treated watersheds do not exceed those from the control watersheds
On watershed 3, herbicide residues found in small amounts in streamflows
the year following application soon disappeared. On all three watersheds,
changes in water quality have been minor.
The work centered at Beaver Creek is one example of the Forest Service
responding to changing public and environmental needs. Basic knowledge
about environmental interactions continues to flow from the watershed
experiments begun years ago. Resource management planning methods being
developed and tested are helping public land managers to better assess
the status and future of the resources under their supervision and to
plan and implement appropriate management programs.
Results from this research and testing program should provide continuing
assistance to natural resource agencies and industries as they respond
to America's changing demands for forest and range products and outdoor
The Beaver Creek Watershed is still a designated biosphere reserve and,
as such, continues to function as an outdoor laboratory, providing study
areas for various research cooperators. Those interested in exploring
these opportunities should contact the Rocky
Mountain Research Station, USDA Forest Service, Flagstaff, Arizona.
For more information about upcoming workshops on the Beaver Creek Watershed,
contact The University of Arizona
Cooperative Extension office in your county.