Current Submissions (candidates of reference sites)

The total drainage area of the catchment is 114 sq. km and the total length of the perennial channels is 177 km. During the last glacial period (Wurm) the tertiary layers in the catchment were covered by eolic sandy-loam and loam soils. This cover is estimated to be between 0 and 10 m deep. The third soil type, clay, covers less than 5% of the total surface. The maximal elevation difference is 150 m. The average year temperature is 10 deg. C, with January the coldest month (mean temperature 3 deg. C) and July the warmest month (mean temperature 18 deg. C). The average yearly rainfall is 775 mm and is distributed evenly throughout the year. The annual evaporation is approximately 450 mm.

One of three experimental watersheds in the Volta Basin. Part of the integrated GLOWA Volta Project (www.glowa-volta.de). Many special measurements are made for PhD studies.

Additional information about the research station can be found at www.glowa-volta.de

More information can be obtained from our homepage at www.glowa-volta.de

Walnut Gulch Experimental Watershed is operated by the United States Department of Agriculture, Agricultural Research Service, Southwest Watershed Research Center locate in Tucson, Arizona. The Walnut Gulch Experimental Watershed encompasses the 150 square kilometers in southeastern Arizona, U.S.A. (31o 43'N, 110o 41'W) that surrounds the historical western town of Tombstone. The watershed is contained within the upper San Pedro River Basin which encompasses 7600 square kilometers in Sonora, Mexico and Arizona. The watershed is representative of approximately 60 million hectares of brush and grass covered rangeland found throughout the semi-arid southwest and is a transition zone between the Chihuahuan and Sonoran Deserts. Elevation of the watershed ranges from 1250 m to 1585 m MSL. Cattle grazing is the primary land use with mining, limited urbanization, and recreation making up the remaining uses. Annual precipitation is 350 mm, mean annual temperature is 17.7C, potential ET is 2600mm. Walnut Gulch, being dry about 99% of the time, is an ephemeral tributary of the San Pedro River. Hydro-meteorologic and soil erosion/sedimentation data are collected from 125 instrumented installations on WGEW. Precipitation is measured with a network of 88 weighing-type recording raingauges arranged in a grid throughout the watershed. Various runoff measuring structures are used to monitor runoff from eight small watershed (< 40 ha). These structures include broad-crested V-notch weirs, H-flumes, and Santa Rita supercritical flow flumes. Runoff from watersheds greater than 40 ha is measured using either livestock watering ponds or large supercritical flow flumes. The largest flume, at the outlet of the Walnut Gulch Experimental Watershed has a flow capacity of 650 cubic meters/sec. There are 10 stock pond watersheds and 11 large flume watersheds currently being monitored. Sediment from the small watersheds monitored with V-notch weirs or H-flumes is sampled with automatic pump samplers. Sediment from watersheds equipped with the Santa Rita supercritical flow flumes is sampled with a total-load automatic traversing slot sampler. Meteorological, soil moisture and temperature and energy flux measurements are made at two vegetation/soil complexes. Permanent vegetation plots and transects have been established to evaluate the impacts of management practices and global change on vegetation.