The University of Arizona

College of Agriculture and Life Sciences

Walnut Gulch Experimental Watershed

The Walnut Gulch Experimental Watershed surrounds the historic city of Tombstone in southern Arizona. The USDA - Agricultural Research Service established the watershed in the 1950s to study floods and the impact of soil and water conservation projects on runoff.

History: The watershed is instrumented with rain gages and runoff measuring flumes, and to date, 50 years of data have been collected. These data have been analyzed to characterize precipitation in convective thunderstorms and to study and model subsequent flood wave movement, transmission losses, and water yield from rangeland watersheds.

Ecosystems: Although historical records indicate that most of the Walnut Gulch Experimental Watershed was grassland approximately 100 years ago, shrubs now dominate the lower two-thirds of the watershed. Major watershed vegetation includes the grass species of black grama, blue grama, sideoats grama, bush muhly and Lehmann lovegrass; and shrub species of creosote bush, white-thorn, tarbush, snakeweed, and burroweed.

Size: 150 square kilometers (37,000 acres)