United States 

 Department of 

 Agriculture 



Forest Service 



Intermountain 

 Forest and Range 

 Experiment Station 



Research Paper 

 INT-274 



May 1981 



Precipitation 

 Characteristics of 

 Summer Storms at 

 Straight Canyon 

 Barometer 

 Watershed, Utah 



Joel E. Fletcher, A. Leon Huber, Eugene E. 

 Farmer, Keith R. McLaughlin, John Rector, and 

 Larry J. Schmidt 



INTRODUCTION 



Precipitation records in high mountain areas are 

 scanty. In Utah and the balance of Western United 

 States nearly all of the rainfall intensity gages are 

 located at elevations below 6,000 ft (1 829 m) m.s.l. Even 

 in the valleys most of the recording rain gage records 

 have not been reduced except by hours. 



The papers of Farmer and Fletcher (1971, 1972a, 

 1972b), Chang (1969), and Croft and Marston (1950) 

 have been given considerable insight into the charac- 

 teristics of high mountain, short-burst rainfall events. 

 Millerand others(1 973) improved the isohyetal maps of 

 the Western United Statesand included regressionsfor 

 determining short duration expectancies from those for 

 6 hours for returns between 2 years and 100 years. 



Personnel of the Utah Water Research Laboratory 

 and Intermountain Forest and Range Experiment Sta- 

 tion (1976) developed annual isoerodent maps of the 

 United States including the Mountain States, in orderto 

 extend the universal soil loss equation to all areas of the 

 country. As a consequence of the availability of these 

 maps, the use of isoerodent values for runoff peak 

 forecasting was tested and the annual isoerodent 

 values were found to be the most pertinent precipitation 

 parameter for forecasting runoff peaks from ungaged 

 watersheds (Fletcher and others 1 976). 



This paper presents an extension of Farmer and 

 Fletcher (1 971 ) to include 1 precipitation gages of the 

 Straight Canyon barometer watershed area and the iso- 

 erodent values for the Straight Canyon area, the Davis 

 County area, and the Great Basin experimental 

 area. 



All precipitation gages were operated during June 

 through September and four were operated from April 

 through October. Gages were at elevations ranging 

 from 7,235 ft (2 205 m) m.s.l. for the Orange Olsen site to 

 1 0,400 ft (3 1 70 m) m.s.l. for the Skyline site. The gages 

 were sufficiently close to one another that single storms 

 were frequently recorded on more than one precipita- 

 tion gage. 



The Straight Canyon barometer watershed is located 

 12 miles W.N.W. of Orangeville, Utah, immediately 

 adjacent to the Great Basin experimental watershed. It 

 lies up the left fork of Cottonwood Creek and occupies 

 an area of about 145 square miles. Elevation ranges 

 between 6,852 ft (2 088 m) and 1 1 ,300 ft (3 444 m) m.s.l. 

 The description given by Farmer and Fletcher (1 971) of 

 the Great Basin experimental area is also applicable to 

 the Straight Canyon barometer watershed. 



Total annual rainfall rangesfrom 1 6.1 inches (40.89 

 cm) at Lower Joes Valley to slightly over 40 inches (1 02 

 cm) on the three peaks (U.S. Weather Bureau 1967). 

 Approximately 44 percent of the precipitation falls 

 during the period May to September. 



Summer precipitation contributes little water to the 

 annual stream flow volume, but it is important to the 

 production of mountain vegetation that is vital to soil 

 stability (Packer 1951; Orr 1957; Packer 1963; and 

 Croft and Bailey 1964). however, vegetal cover is only 

 one factor that affects the hydrologic performance of a 

 watershed. Storm characteristics also have a major 

 effect on the processes of soil erosion and flood pro- 

 duction, especially when the land becomes barren of 

 vegetal cover due to fire, road construction, over- 

 grazing, or urban development. 



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