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Beaver Creek Experimental Watershed: Research on forest management, streamflow, and forage production

Status: 
Complete
Dates: 
January, 1955 to December, 1982

Map of Beaver Creek experimental watersheds on the Coconino National Forest, Arizona.
Map of Beaver Creek experimental watersheds on the Coconino National Forest, Arizona. Map of Beaver Creek experimental watersheds on the Coconino National Forest, Arizona.
The Southwest Watershed Science Team is engaged in research on the Beaver Creek Experimental Watershed (BCEW) outside of Flagstaff, Arizona. There is over 20 years of hydrologic, climatic, vegetation, fuels, soils, and wildlife data from the 1950s through the 1980s which provide background for the study. 

In the mid-2000's researchers reinstated the project to collect data on climate, stream flow, vegetation, forest floor, and soil conditions. The main goal of ongoing research at BCEW is to provide land managers with information about the ecological effects of fuel treatments in the ponderosa pine forests and pinyon-juniper woodlands at a watershed scale.

History of BCEW

Research at BCEW began in 1955 after ranchers and other water users expressed concern to the U.S. Forest Service that growing numbers of plants and shrubs on Forest Service lands were threatening grazing lands and water resources. Forest Service researchers began testing methods to increase streamflow by about 1960. The BCEW study was originally designed to explore influences of vegetation manipulations in pinyon-juniper and ponderosa pine on water yield and to evaluate changes in livestock forage, timber production, wildlife habitats, recreational values, and soil conditions.

The BCEW was designated a biosphere reserve, a component of a worldwide network in Unesco's Man and the Biosphere Program, in 1976, and the original research at BCEW ended in 1982.

Researchers with Northern Arizona University and the RMRS Southwest Watershed Science Team reinstated research at BCEW in 2006. The new effort focuses on five watersheds (76 to 722 ha in size), which were re-instrumented to measure stream flow and weather conditions. Data is also being collected on vegetation, forest floor, and soil conditions before and after various fuel treatments.

Approach

The Beaver Creek Watershed

Vegetation types found within the Beaver Creek Experimental Watershed.
Vegetation types found within the Beaver Creek Experimental Watershed.
The BCEW encompasses 111,375 ha on the Coconino National Forest (click here for a virtual tour of the BCEW). The BCEW is upstream from the junction of Beaver Creek and the Verde River, and its part of the Salt-Verde River Basins. These Basins are major river drainages in central Arizona and provide much of the municipal and agricultural water for Phoenix and other communities in the heavily populated Salt River Valley. The center of the BCEW is about 80 km south of Flagstaff, Arizona, in Coconino and Yavapai Counties.

The Beaver Creek watershed lies along the Mogollon Rim within the largest continuous stands of ponderosa pine in the United States--a belt of trees extending for nearly 321 km across Arizona. In ascending order of elevation, the three vegetation types found on the Beaver Creek watershed are semi-desert shrubs (<1,500 m elevation), pinyon-juniper (1,500-1,800 m), and ponderosa pine (>2,000 m).

The BCEW is characteristic of much of the Coconino National Forest, and the watershed includes plateaus, sloping mesas and breaks, and steep canyons. Specific conditions include:

  • Elevation ranging from 900 to 2,400 m above sea level.
  • Bedrock consisting of igneous rocks of volcanic origin, below which are sedimentary rocks of Kaibab, Coconino, and Supai formations.
  • Highly variable precipitation and streamflow, with streamflow primarily derived from snow melt in the late spring / early summer.

Additional information on the BCEW is available online through the Beaver Creek Environmental Atlas maintained by Northern Arizona University.

Experimental Design (1956-1982)

In 1956, the Beaver Creek watershed was divided into 20 watershed subunits that were treated with various vegetation management practices (Table 1). Eighteen of the watershed subunits ranged from about 25 to 825 ha, while the two remaining were about 4,900 and 6,675 ha, respectively. These two latter subunits were intended to represent areas the size of which forest managers typically work with.

The research focused on three treatments applied to trees and shrubs prior to seeding with various grass types: uprooting, herbicide spraying, and cutting. Many watershed subunits received uprooting since the use of herbicides is limited by federal standards.

Researchers paired watershed subunits with similar characteristics, both physical and biological, to measure streamflow, sediment production, water quality, vegetation, and animal use prior to treatment. Management treatments were then applied to one of the paired subunits and measurements continued on both the treated and control subunits. Changes caused by management practices applied to the treated subunits were evaluated by comparing post-treatment values with pre-treatment data, as well as with data from the control subunits.

Vegetation, fuels, and wildlife data were originally collected in the mid-1960s and re-measured in the mid-1970s. Some of the watersheds were re-measured in the early 1990s.

Watershed Measurement years Treatment Treatment year
Table 1. Description of research and treatments in the 20 watershed subunits at BCEW.
1 1958-1973 Cabled 1963
2 1958-1983 None  
3 1958-1983 Herbicide application 1968
4 1958-1973 None  
5 1958-1973 None  
6 1958-1973 Felling overstory trees 1965
7 1957-1973 Thinning 1958
8 1957-1983 Silvicultural thinning 1974
9 1957-1976 Regular one-third strip-cut 1967
10 1958-1982 Patch-cut 1974
11 1958-1982 Clearcut and grazing 1958
12 1958-1982 Clearcut 1967
13 1959-1983 None  
14 1959-1982 Irregular strip-cut and thin 1970
15 1963-1982 None  
16 1963-1982 Irregular strip-cut and thin 1972
17 1963-1983 Heavy thinning 1969
18 1963-1983 None  
19 1962-1983 Silvicultural thinning 1973
20 1962-1983 None  

Experimental Design (2006-today)

In 2006, scientists with RMRS and Northern Arizona University re-instated research in five watershed subunits at BCEW (watersheds 9, 11, 12, 13, and 14). The new research is focused on fuel treatment effects, specifically the impacts of burning and/or thinning on stream flow and water quality, vegetation, forest floor, and soil conditions. For detailed methodology, see the project page Beaver Creek Experimental Watershed: Research on fuel treatment effects.

Key Findings

  • Vegetation treatments in pinyon-juniper woodlands only resulted in minor water yield increases.
  • Erosion rates and sediment loads in the pinyon-juniper watersheds varied sharply with the intensity of storms. A heavy storm soon after tree removal from one watershed washed away much of the soil.
  • In the long run, average sediment loads from the treated watersheds did not significantly exceed those from the control watersheds.
  • Small amounts of herbicide residues were identified in streamflows from one subunit the year after application, but the residues soon disappeared. In three subunits, changes in water quality were minor.
  • Increased grass was 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.
  • Pinyon-juniper removal impacted small mammals and birds. For example, birds that feed in trees were replaced by ground feeders.
  • Pinyon-juniper removal did not seem to affect the mule deer, but this was attributed to the availability of additional forage in early spring, when mule deer are often in need of it.

Publications

Deliverables

An annotated bibliography of BCEW research was published by the Rocky Mountain Research Station in 1998.

Other

 

Go to the Southwest Watershed Science Team home page.



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