Water has been recognized as an important resource in central Arizona
and the arid Southwest that has affected populations occupying the Salt
River Valley for centuries (Baker 1999). Water related activities have
been documented since about 200 BC, when Hohokam Indians settled the Valley
and constructed canals to irrigate their fields. Europeans began to settle
in the Phoenix area in the late 1860s and depended on irrigation water
from the Salt River for agriculture. However, water supplies fluctuated
greatly because the river often flooded in winter and dried up in the
summer. There were no impoundments to store water for the dry seasons.
In 1904, the Salt River Water User's Association signed an agreement
with the United States government under the National Reclamation Act to
build a dam on the Salt River below the confluence with Tonto Creek. The
Roosevelt or Theodore Roosevelt Dam, the first of six dams on the Salt
and Verde Rivers, was completed in 1911 and the Salt River Project was
During the mid-1950s, the amount of water stored in project lakes was
very low and, as a consequence, apprehension arose among some residents
that a serious water shortage impended. Groundwater supplies in the Salt
River valley were also being rapidly depleted, and pumping costs were
In the early 20th century, watershed managers became concerned that erosion
on the adjacent and headwater watersheds of the Salt River would move
sediment into the newly constructed Roosevelt Reservoir and decrease its
capacity. Measurements indicated that 101,000 acre-ft of coarse granitic
sediments had accumulated behind Roosevelt Dam between 1909 and 1925.
The Summit Plots, located between Globe, Arizona and Lake Roosevelt, were
established in 1925 by the USDA Forest Service 15 mi upstream from Roosevelt
Dam to study the effects of vegetation recovery, mechanical stabilization,
and cover changes on stormflow and sediment yields from the lower chaparral
zone (Rich 1961).
Long-term studies at Sierra Ancha Experimental Forest in central Arizona
showed some potential for increasing runoff by converting brushlands to
grass. Based on this, a belief existed that water yield from the Salt
and Verde Watersheds could be significantly increased by treatment of
various vegetation types. Suggestions for water-yield improvement included
widespread burning of chaparral, eradication of pinyon-juniper by burning
and mechanical methods, and prescribed burning in ponderosa pine.
Spring runoff at Sierra Ancha Weir
In the summer of 1955, several ranchers met with a USDA Forest Service
representative and an official with the Salt River Project on the Beaver
Creek watershed near Flagstaff. These people were concerned that increasing
densities of trees and shrubs on upland watersheds on the Salt and Verde
River basins were reducing the flow of streams and the supply of livestock
As a result of this meeting, the University of Arizona was commissioned
to investigate the potential for increasing water yield from the state's
forests and ranges. The somewhat optimistic university findings, titled
Recovering rainfall (Barr 1956) and 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. This 1956 report resulted in demand for an
immediate action program.
Cover of "Barr report"
In responding to this demand, the Arizona Water Program of the USDA Forest
Service was initiated in the late 1950s to evaluate the usefulness of
selected vegetative management programs in increasing water yields and
other multiple resource benefits in the Salt River Basin (Arizona State
Land Department 1962). The Beaver Creek watershed became a significant
component of this program of experimental studies in the pinyon-juniper
and ponderosa pine types.
Twenty pilot watersheds were established between 1957 and 1962 to test
the effects of vegetation management practices on water yield and other
resources (Brown, H.E. et al. 1974). Of the 20 watersheds, 18 were from
66 to 2,036 acres in size; 3 in the Utah juniper type, 3 in the alligator
juniper type, and 12 in the ponderosa pine type. The other 2 catchments,
encompassing 12,100 and 16,500 acres of ponderosa pine forests, were set
aside to demonstrate the effects of management practices on areas that
managers work with operationally.
Stream gauges were built at the outlets of all watersheds, while sediment-measuring
devices, in which suspended sediments and bedloads could be collected,
were constructed on some. A network of precipitation gauges was installed
throughout the study area (Baker 1982). Timber, herbage, and wildlife
resources were inventoried (the latter by the Arizona Game and Fish Department)
on a system of permanently-located primary sampling units established
on each pilot watershed (Brown, H.E. et al. 1974, Clary et al. 1974).
Point sampling techniques were used to monitor stand structures, tree-stem
form, and species composition over time. These sampling points were also
center-points for plots of varying sizes on which regeneration success,
herbaceous vegetation, wildlife populations and habitat preferences, and
hydrologic conditions were sampled.
Suspended sediment intake (A),
Beaver Creek flume (B),
sediment basin for bedload measurements(C)
Yields of water, timber, forage, and other natural resource products
from the pilot watersheds were determined before any treatments were applied
to provide the needed pre-treatment calibration information. One watershed
was then altered through vegetative manipulation and the other was held
in its original condition as a control for evaluations of potential changes
in these yields. If a resource change was detected after treatment, it
was attributed to the treatment implemented.
To refine the findings from the studies on the pilot watersheds for use
over a wide range of conditions, 24 smaller watersheds, 12 to 40 acres
in size, with more uniform soil, plant life, and topography, were established
in the early 1970s to sample the range of diverse ecological characteristics
in the ponderosa pine forests (Brown, H.E. et al. 1974). To compare the
findings from watersheds with soils developed on basalt and cinders (55%
of the Salt-Verde River Basin) to watersheds on soils formed from sedimentary
rocks (45% of the Salt-Verde River Basin), 3 of these smaller watersheds
were established on limestone soils at Rattle Burn (Campbell et al. 1977)
and 4 were established on sandstone and tertiary alluvium soils near Heber
(2 per each soil parent material) (Ffolliott and Baker 1977).
Arizona State Land Department. 1962. The Arizona watershed program.
Phoenix, AZ: Arizona State Land Department.
Baker, M.B., Jr. 1982. Hydrologic regimes of forested areas in the
Beaver Creek watershed. USDA Forest Service, General Technical Report
Barr, G.W. 1956. Recovering rainfall: More water for irrigation, Part
I. Arizona Watershed Program. Cooperating: Arizona State Land Department,
Water Division of the Salt River Users' Association, University of Arizona.
Brown, H.E.; Baker, M.B., Jr.; Rogers, J.J.; Clary, W.P.; Kovner, J.L.;
Larson, F.R.; Avery, C.C.; Campbell, R.E. 1974. Opportunities for increasing
water yields and other multiple use values on ponderosa pine forest
lands. Res. Pap. RM-129. Fort Collins, CO: U.S. Department of Agriculture,
Forest Service, Rocky Mountain Forest and Range Experiment Station.
Campbell, R.E.; Baker, M.B., Jr.; Ffolliott, P.F.; Larson, F.R.; Avery,
C.C. 1977. Wildlife effects on a ponderosa pine ecosystem: An Arizona
case study. Res. Pap. RM-191. Fort Collins, CO: U.S. Department of Agriculture,
Forest Service, Rocky Mountain Forest and Range Experiment Station.
Clary, W.P.; Baker, M.B., Jr.; O'Connell, P.F.; Johnsen, T.N., Jr.;
Campbell, R.E. 1974. Effects of pinyon-juniper removal on natural resource
products and uses in Arizona. Res. Pap. RM-128. Fort Collins, CO: U.S.
Department of Agriculture, Forest Service, Rocky Mountain Forest and
Range Experiment Station.
Ffolliott, P.F.; Baker, M.B., Jr. 1977. Characteristics of Arizona
ponderosa pine stands on sandstone soils. Gen. Tech. Rep. Pap. RM-44.
Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky
Mountain Forest and Range Experiment Station.
Rich, L.R. 1961. Surface runoff and erosion in the lower chaparral
zone - Arizona. USDA Forest Service Station Paper No. 66. 35 p. Rocky
Mountain Forest and Range Experiment Station, Fort Collins, CO.