THE DOMAIN FOR DRY FARMING 55 



The southeastern and northwestern portions have the 

 highest precipitation, and Bighorn county in the north 

 and Sweetwater in the south the lowest. Only in por- 

 tions of these counties can the country be classed as arid. 



In Montana the average annual precipitation is 15.39 

 inches, the maximum 24.1 and the minimum 11.1. Only 

 in a small portion of the northwest area is the rainfall 

 20 inches and over, and only along the Milk and Bighorn 

 rivers and the country contiguous thereto is it less than 

 15 inches, except in a small area running diagonally 

 across the central portion of the state. In none of the 

 states of the semi-arid west are the conditions so uni- 

 form with reference to precipitation. Montana has prac- 

 tically no arid land except what is made so by the 

 presence of alkali. 



In Idaho the average annual precipitation is 17.52 

 inches, the maximum 37.6 and the minimum 9.3. The 

 precipitation is very unevenly distributed. In the north- 

 erly counties of Bonner, Kootenai, Shoshone, Latah, near- 

 ly all of Nez Perce and part of Idaho, it runs from 20 to 30 

 inches. South of these counties, it is, generally speaking, 

 15 inches and less, save in the counties of Washington 

 and Boise in the central western area. In the south- 

 eastern and southwestern counties, it runs from 9 to 15 

 inches. 



In Utah the average annual precipitation is 12.66 

 inches, the maximum 23.1 and the minimum 4.1. The 

 north central portion has a precipitation of 15 to more 

 than 20 inches ; east and west from this area, also in the 

 south central portion, it is, generally speaking, from 15 

 to 10 inches. The east and west third have each ap- 

 proximately less than 10 inches. A very considerable 

 portion of Utah is arid. 



In Nevada the average annual precipitation is 9.2 

 inches, the maximum 26.1 and the minimum 4.3. Only 

 in a very small area in the extreme western portion of 



