Snowpack-runoff Relationships for Mid-elevation Snowpacks on the Workman Creek Watersheds of Central Arizona

Gerald J. Gottfried

Jan 2002 · U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station

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Snowpacks in the southwestern United States melt intermittently throughout the winter. At some mid-elevation locations, between 7,000 and 7,500 ft, snowpacks appear and disappear, depending on the distribution of storms during relatively dry winters. Some winter precipitation can occur as rain during warm storms and is not reflected in the snow course data. The USDA Natural Resources Conservation Service (NRCS) maintains a system of measuring stations to index snow conditions and predict snowmelt runoff. The three Workman Creek watersheds in the Sierra Ancha Experimental Forest north of Globe were instrumented in late 1938 to study the hydrology of southwestern mixed conifer forests and to determine changes in streamflow and sedimentation resulting from manipulating the forest cover. The watersheds were deactivated in 1983, but they were re-instrumented in June 2000 after the Coon Creek wildfire to measure fire effects on forest hydrology and sediment dynamics. The Rocky Mountain Research Station would like to use NRCS data from the Middle Fork of Workman Creek to reinforce its hydrologic data acquisition and interpretation efforts. Snow water equivalent data can be used to characterize past winter runoff volumes and peak mean daily runoff. Significant regressions were developed between the data sets with coefficients of determination values ranging from 0.40 to 0.77. The relationships defined by these regressions will allow researchers and managers to ascertain the impacts of fire on snowmelt-related hydrologic processes and to estimate winter flows for the years when the installations were closed. They also provide an insight into the snowpackrunoff relationships for intermittent snowpacks that are common at intermediate elevations throughout Arizona.