20 



DRY FARMING IN THE GREAT BASIN. 



In this case, again, the unusual rainfall of 1906 is shown. It becomes 

 apparent from a comparison of this (fig. 7) and the preceding dia- 

 grams that the rainfall of 1906 was much above the average in the 

 Great Basin. The relatively large rainfall of 1906 has stimulated 

 local interest in dry farming in a way that nothing else could do. 



The wonderfully large crops obtained during the last season with- 

 out irrigation, together with the recent unusual interest in dry farm- 

 ing, have combined to convince the local public that irrigation is 

 rapidly becoming unnecessary in that region. In fact it is not gen- 

 erall}^ realized how much more rain there was during the last year 



than usually falls. It is true that 

 the present agitation in favor of 

 dry farming in Utah was actively 

 l)egun in 1902 and 1903, when the 

 rainfall was rather below the aver- 

 age, so that while the greater rain- 

 fall of last year has probably en- 

 couraged unAvarranted hopes as to 

 what can be done without irriga- 

 tion, yet the actual extension of 

 farming has doubtless been much 

 greater than it would have been 

 without the increased rainfall. 

 There can be no doubt that there 

 for the records of rainfall show no 



Fig. 5.— Diagram showing the total annu- 

 al precipitation at Tooele, Utah, 1S97-1906. 



wdll soon be drier years again, 



reason for believing that the climate is changing. 



INFLUENCE OF LOCAL TOPOGRAPHY ON RAINFALL. 



The air currents that bring rain into the Great Basin come mainly 

 from the west, saturated with moisture from the Pacific Ocean. 

 A large part of this water in the lower atmosphere is precipitated as 

 this air passes over the high Sierra Nevada range, but enough mois- 

 ture is soon recovered either from the upper air or from the earth for 

 each of the successive mountain ranges in the Great Basin to receive 

 its share of rain, the amount in each case increasing with the height 

 of the ranges and their distance apart. Thus, just as the western 

 part of the Great Basin is more arid than the eastern part, so the 

 western side of each valley in the Great Basin is drier than the 

 eastern side; or. conversely, the western slope and foothills of a 

 mountain range receive more rainfall than the eastern slope, the 

 difference depending somewhat upon the height of the range. (See 



fig. 8.) 



The following table illustrates this phenomenon. The town of 

 Deseret lies well out in a broad valley which is much too dry for any 



103 



