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item Kidwell, Mary

Submitted to: Santa Rita Experimental Range: 100 Years (1903-2003) of Accomplishments and Contributions Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/20/2003
Publication Date: 9/15/2003
Citation: Lane, L., Kidwell, M.R. 2003. Hydrology and soil erosion. Santa Rita Experimental Range: 100 Years (1903-2003) of Accomplishments and Contributions Conference Proceedings. Oct. 30-Nov. 1, 2003, Tucson, AZ., pp. 92-100.

Interpretive Summary: The Santa Rita Experimental Range (SRER) has been operated from 1903 until the present by the U.S. Forest Service and more recently by the University of Arizona. In 1974 the Agricultural Research Service and the U.S. Forest Service began cooperative grazing and brush control experiments on eight small experimental watersheds. We reviewed the 100 year history of hydrologic and soil erosion research on the SRER and found that almost all of the research was associated with these eight small experimental watersheds. Major research findings from experiments on these experimental watersheds include quantification of the reduction in runoff and soil erosion caused by brush/tree removal and the significance of the spatial variability of soil properties controlling runoff and soil erosion on paired watersheds. Twenty eight years of hydrologic monitoring on the eight experimental watersheds provides scientists with a unique opportunity to conduct long-term adaptive management experiments for alternative watershed management alternatives.

Technical Abstract: We review research on surface water hydrology and soil erosion at the Santa Rita Experimental Range (SRER). Conceptual models for annual water balance and annual sediment yield at the SRER were developed and supported by data from four very small experimental watersheds operated by the ARS. The impacts of rotation and year-long grazing activities and of mesquite removal were analyzed using data from four small experimental watersheds. The analyses suggested that mesquite removal reduced runoff and sediment yield, but differences in hydrologic response from paired watersheds due to soils differences dominated grazing and vegetation management impacts. The 28 years of monitoring under the same experimental design on the four pairs of watersheds provides us with a long period of 'pre-treatment' data on the paired watersheds. New treatments could now be adapted and designed based on lessons learned from monitoring over nearly three decades. There is a unique opportunity to institute long-term adaptive management experiments on these experimental watersheds.