CLIMATE. 



Rainfall records previous to the establishment of the Government 

 weather service at Salt Lake City, show an annual variation of from 

 10 to 29.5 inches. At Salt Lake City the mean annual rainfall, 

 according to the record of the past twenty-five years of the U. S. 

 Weather Bureau, is 16 inches, with a minimum of 10.3 and maxi- 

 mum of 23.6 inches. Of this annual rainfall, less than three inches 

 fall during the four warmest months of the year June, July, Aug- 

 ust, and September. These four driest and warmest months, having 

 a total mean rainfall of less than three inches and a mean tempera- 

 ture of 70.4 F., are accompanied by a low, relative humidity con- 

 ditions favoring excessive evaporation. 



It is estimated that the annual evaporation from a free water sur- 

 face in this locality is eight feet. Calculations from data of one of 

 the salt companies show the evaporation from their ponds to be thir- 

 ty-seven inches for the four months of June to September. It must 

 be borne in mind, however, that this is from a saturated brine, and 

 that the vapor tension, and consequently the evaporation, is much 

 lessened by the presence of large quantities of salt. 



Since the greater part of vegetable growth is made during these 

 four months, these data show how important and necessary is irri- 

 gation for the production of crops. Indeed, no farming is carried on 

 without irrigation except in the case of wheat, which makes most of 

 its growth prior to June, and from which small yields is the rule 

 rather than the exception. 



WATER SUPPLY. 



The Jordan River, from which all of the irrigation water used on 

 the above area is taken, is the main channel through which the waters 

 of a large number of streams extending well back into the mountains 

 east and south, as well as the waters of Utah Lake and its inflowing 

 streams, make their way to the Great Salt Lake. The annual pre- 

 cipitation in the mountains exceeds that in the valleys and is largely 

 of snow, which lingers on the highest mountains during the greater 

 part of the summer. The melting snow and the numerous moun- 

 tain springs make the irrigation water supply constant, plentiful, 

 and of good quality. The Utah and Salt Lake and the South Jor- 

 don canals get their water supply from the Jordan River, near the 

 Jordan Narrows, and it is representative of the water of Utah Lake, 

 which was found to contain eighty-nine parts of soluble matter in 

 one hundred thousand parts of water. Of this only about fifty parts 

 are likely to remain in solution and accumulate in the soil to the det- 

 riment of plants. 



