THE ARS LAB IN TUCSON

In November of 1994, an international symposium was convened in Tucson, Arizona, to honor Dr. Ken G. Renard on the occasion of his retirement. Ken had directed the USDA ARS Lab in Tucson (now the Southwest Watershed Research Center) for more than three decades.

In one of the meetings at that symposium, Ken confided to his audience how the lab hab been originally established in the early 1950's with the purpose of evaluating how upstream conservation programs would affect downstream water yield. USDA had programs with local ranchers to improve conservation practices, but downstream users objected to the programs because prior appropriation water laws entitled them to water produced upstream. Thus, the lab's original mission was to quantify the cause/effect hydrologic phenomena in semiarid regions.

It soon became apparent that factors applicable in more humid areas were not applicable in drier climates. Much effort was spent on quantifying the various components of the hydrologic cycle, and the original mission was altered to include modeling, water quality, remote sensing, and rangeland health.

A clearer picture of the hydrologic cycle has emerged since the ARS Tucson experience. We now know that the behavior is not so much one of cause/effect (characterized by subtraction in one part of the system bringing an addition to another) but, rather, one largely controlled by cybernetic (biofeedback) processes. Anthropogenic reductions in evapotranspiration can trigger local climatic changes which have the net effect of reducing runoff. Likewise, increases in evapotranspiration will bring forth increases in runoff. 1


1 Ponce, V. M., and A. K. Lohani, and P. T. Huston. 1997. Surface albedo and water resources: Hydroclimatological impact of human activities.  ASCE Journal of Hydrologic Engineering, 2(4), October, 197-203.

 

Camp Creek, in eastern Oregon, developed due to overgrazing of the meadow (1989).

Camp Creek, in eastern Oregon, developed due to overgrazing of the meadow (1989).