SOIL SUEVEY OF SOLOMONSVILLE AEEA, AEIZONA. 



cultivation within recent years, and the limits of irrigation are at the 

 present time being quite rapidly extended. Progress in the adoption 

 of modern methods of cultivation and of labor-saving devices has also 

 been rapid. 



CLIMATE. 



The climate of this section is essentially arid, the average annual 

 rainfall being less than 10 inches. This condition is accompanied by 

 low relative humidity, marked absence of clouds or fog, high maxi- 

 mum and average annual temperature, and vigorous wind movement 

 at certain seasons of the year — all factors most favorable to evapora- 

 tion and intensifying the aridity resulting from insufficient rainfall. 



The practice of agriculture without the aid of irrigation is not 

 attempted in this section, and the success of agriculture depends to a 

 greater extent upon the rainfall in the region of the headwaters of the 

 Gila River and its tributaries than in the immediate vicinity of the 

 irrigated lands. These streams head in the mountains at a much 

 higher altitude than the valley, and hence receive the rainfall of a 

 much more humid climate, the amount of precipitation increasing rap- 

 idly with the elevation. 



The seasonal floods, caused by the mountain rains and the more or 

 less uncertain showers and rains of the valley, occur during the mid- 

 dle and late summer months, sometimes continuing through the fall. 

 During the winter and spring the precipitation is slight. Thunder 

 storms during the summer and rainy seasons are frequently accom- 

 panied by severe dust storms and sometimes by hail. 



The following table is from records of the Weather Bureau sta- 

 tions at Dudleyville and Fort Grant. The former station lies a few 

 miles west of the area in Pinal County, and the latter in Graham 

 County, just outside of the southern boundary of the survey. 

 Normal monthly and annual temperature and precipitation. 



The winters are clear and mild. Frosts are of frequent but snow 

 of very rare occurrence in the valley. During the summer months 

 the days are extremely hot, but the sensible temperature is greatly 

 reduced by the low relative humidity. The nights are generalh' cool 



9568—04 2 



