Winter Irrigation of Deciduous Orchards 



209 



growth is made during the three months that follow. During 

 these three months the weather becomes increasingly warm, the 

 maximum temperatures, by the latter part of June, ranging from 

 ioo° to 115 F. in the shade in most of the cultivated valleys. 

 The relative humidity of the atmosphere decreases as the season 

 advances and the temperatures rise, evaporation consequently be- 

 coming very rapid. During July, August and September the 

 weather is as warm as, or warmer than, during June; but the 

 humidity is temporarily increased from time to time by rains, and 

 the weather is consequently less trying upon vegetation. From 

 September to December the weather grows gradually cooler, and 

 the relative humidity usually gradually increases. 



The following averages of the monthly mean temperature 

 and mean relative humidity at Phoenix for each month of the 

 past five years will indicate the changes in the weather from sea- 

 son to season of the year, in the largest agricultural valley of the 

 territory : 



SUPPLY OF IRRIGATING WATER IN SALT RIVER VALLEY. 



The variation in the supply of irrigating water from month 

 to month of the year, in the Salt River valley, will be indicated by 

 the following monthly averages of the flow of the Salt River dur- 

 ing the past twelve years, based on available records. 



The numbers express the flow in thousands of acre feet 



