Analysis of Long-Term Streamflow Patterns on Two Davis County Experimental Watersheds in Utah

The influence of aspect on water yield variability over a long period, 1936-1964, was studied at two small, mountainous watersheds within the Davis County Experimental Watershed near Farmington, Utah. North-facing Miller Creek is densely vegetated by a conifer-aspen forest and mountain brush. Miller Creek\u27s yield was more variable for daily, monthly, seasonal, and annual flows than yields from south-west facing Halfway Creek which is covered by mountain brush. Differences between watersheds in annual yield and snowmelt season runoff were nonsignificant. The snowmelt runoff season extended for an average of 65 days on both watersheds, but it began 24 days earlier (March 29) on Halfway. Approximately 57 percent of the mean annual flow of 19.4 inches on Halfway, and 68 percent of Miller\u27s mean annual yield of 17.9 inches occurred during the snowmelt runoff season. One-third of Halfway\u27s annual flow and one-half of Miller\u27s occurred during the May 15 to September 15 growing season when only one-fifth of the annual precipitation of 42 inches usually fell. The difference between the growing season flows from the two watersheds was significant, with Miller\u27s flow greater by 3.4 inches