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2000 E. Allen Rd. Tucson, Arizona 85719 PHONE 520 - 670 - 6381 FAX 520 - 670 - 5550 |
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Field Sites
The SWRC currently operates instrumented field sites at the Walnut Gulch Experimental Watershed near Tombstone, AZ and the Santa Rita Research Range south of Tucson, AZ.
Walnut Gulch Experimental Watershed
| Location
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Walnut Gulch enters the San Pedro
river at Fairbank, Arizona. The study area comprises the upper 150 sq. km
of the drainage basin. |
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| Research History |
Studies on the Walnut Gulch
Experimental Watershed at Tombstone, Arizona are part of the comprehensive
research initiated in 1951 by the Research Division of the Soil Conservation
Service. After considerable screening of prospective areas in Arizona, New
Mexico, and Colorado, active research was begun in 1953 on the Walnut Gulch
Experimental Watershed.
In 1954, the research and personnel were transferred to the Agricultural Research Service; and in 1961, the Southwest Watershed Research Station was established with headquarters in Tucson. Research is being conducted in cooperation with the Natural Resource Conservation Service, the local Soil Conservation Districts, and the ranchers who own the land of the watersheds.
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| Climate |
The climate at Tombstone can be classified as semiarid or steppe, hot, with a dry winter, but is quite close to being an arid or desert climate. Mean annual temperature at Tombstone is 17.6 degrees C and mean annual precipitation is approximately 330 mm.
Annual water balance for the Walnut Gulch Experimental Watershed.
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| Geology |
The Walnut Gulch Experimental
Watershed is located primarily in a high foothill alluvial fan portion of
the San Pedro River watershed. Cenozoic alluvium is very deep and is
composed of coarse-grained fragmentary material, the origin of which is
readily traceable to present-day mountain flanks on the watershed. The
alluvium consists of clastic materials ranging from clays and silts to
well-cemented boulder conglomerates with little continuity of bedding.
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| Land Use |
The primary land use on the
watershed is grazing by cattle. Historically, mining was important.
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| Vegetation |
There is evidence that much of the area around Tombstone was grassland less than 100 years ago; but now shrubs dominate about 2/3 of the watershed. Creosote, tarbush, mortonia, and whitethorn are the most common shrubs. The remaining 1/3 is still grassland, dominated mainly by black grama, curly mesquite grass, and tobosa grass | |
Santa Rita Experimental Watersheds
| Research History |
The SWRC currently maintains eight subwatersheds within the Santa Rita Experimental Range (SRER), the oldest continuously maintained experimental range in the western United States (est. 1903). Established in 1975, these eight small watersheds are set up as paired watersheds. | |
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