Figure 6. — Typical 

 contour trench 

 cross-section 

 showing cut and 

 fill grade slopes. 



METHOD OF INVESTIGATION 

 Trench Construction 



During the summer of 1964, contour trenches were constructed on the upper 15 per- 

 cent of the Halfway Creek drainage according to standards outlined in Forest Service 

 Handbook 2569.11 (U.S. Dep. Agr. 1959). These trenches were designed to hold 50 per- 

 cent of precipitation from a 2-inch storm lasting 1 hour, plus allowing an additional 

 1.5 feet freeboard. 



Because of variations in slope gradient, the slope distance between trenches 

 ranges from 40 to 120 feet. The vertical height from trench bottom to fill crest was 

 maintained at 4.5 feet. The profile is shown in figure 6. This gave approximately 

 10 cubic feet of storage capacity per linear foot. 



When the trenches were completed they were seeded with a mixture of yellow clover 

 (^Melilotus officinalis), smooth brome {Bromus inermis) , mountain brome {Brorms 

 carinatus) , intermediate wheatgrass {Agropyvon intermedimi) , and tall oatgrass 

 {Arrhenatherum elatius) . 



Instrumentation 



The locations of most instruments used in this study are shown in figure 1. 



Modified Venturii-trapezoidal flumes were installed on the Halfway Creek and 

 Miller Creek drainages in the 1930 's. The trapezoidal section was built into the 

 bottom of a broad-crested weir (fig. 7). 



Except for a brief period following the 1947 flood when operation of the Halfway 

 Creek gage was disrupted, both structures have been maintained and continuous strip 

 chart records of streamflow gathered since their construction. 



A network of recording precipitation gages has been maintained and operated during 

 the summer months in the Farmington Canyon area since 1942. A comprehensive report on 

 these data has been published by Farmer and Fletcher (1969). In addition, two precipi- 

 tation storage gages are maintained on the Farmington Canyon watershed, the Rice Cli- 

 matic Station gage (since 1940) , and the Farmington Guard Station gage (since 1951) . 

 Summer precipitation intensity data, air temperature data, and snow course data are 

 also available from Rice Climatic Station. Fifteen years of snow measurements can be 

 obtained from the Farmington Guard Station. 



7 



