Table 3 . --Expeoted annual seasonal maximum 24-hour 



preo-ipitation depths, in inches, by recurrence 

 intervals and precipitation zones 





Recurrence 



interval 



(years ) 



: 10 ■ 



25 







DAVIS COUNTY EXPERIMENTAL WATERSHED 





1 



2.21 



2.54 



2.74 



2 



2.04 



2.38 



2.45 



3 



1.44 



1.87 



2.11 



4 



1.54 



1 .87 



1.97 





GREAT BASIN EXPERIMENTAL 



AREA 





1 



1.15 



1 .30 



1.34 



2 



1.49 



2.16 



2.47 



3 



1.70 



2.16 



2.33 



4 



1.39 



1 .66 



1.70 



Monthly precipitation fluctuates widely between zones and between years. Any 

 month during the period May-October may be completely dry at one or more stations. 

 Also, any month may exceed the average by 300 to 700 percent. 



On both study areas, the average number of storms per month tends to vary as does 

 the monthly precipitation depth (table 4). The catch of summer precipitation in Zone 2 

 on the Davis County Experimental Watershed was relatively high; this was attributed to 

 its leeward position. Hovind (1965) reported similar results, specifically, that gage 

 catch in the lee of a mountain peak exceeded that on the windward slope by as much as 

 400 percent. 



With respect to the zonal intensity-duration-frequency characteristics, the most 

 intense rainfalls do not occur in the precipitation zones receiving the greatest depths 

 of rainfall. The most intense rainfall is generally expected to occur in Zone 2 on the 

 Great Basin Experimental Area and in Zone 1 of the Davis County Experimental Watershed. 

 The depth of expected rainfall on these zones is less than that on one of the higher 

 elevation zones. 



No pronounced dry summer period occurs in the Great Basin area. Price and Evans 

 (1937) found a bimodal dry season in June and September. On the other hand, our 

 analysis shows that July and September are the driest months. Considering the random 

 nature of summer precipitation our results are not in serious conflict with those 

 reported by Price and Evans. On the Davis County Experimental Watershed, July is the 

 driest month, and September is the second driest month. The difference in July totals 

 between the two study areas appears to be related to a lesser effect from convective- 

 orographic storms in the Davis County area. Whether this difference on the two areas 

 is primarily due to the greater distance of the Davis County area from the Gulf of 

 Mexico, to a lesser frequency of favorable circulation, or to more intervening mountain 

 barriers that impede the moist southerly flow, is not evident. Apparently the semi- 

 monsoon circulation that develops over the southwestern United States and makes July one 

 of the wettest months of the year in that region does not affect the Davis County area. 



15 



