Why Great Salt Lake Has Fallen 



75 



ping in all foreign waters by obtaining 

 and disseminating necessar3 r information 

 on all nautical subjects, a knowledge of 

 which tends to reduce the dangers of 

 navigation to a minimum. This also 

 means that its work is a practical prepar- 

 ation for war, inasmuch as the results 

 form a safeguard for our Navy the im- 



portance of which cannot be over- 

 estimated. 



There can be no question as to the 

 necessity for this work when we con- 

 sider that even now, with our far-reach- 

 ing distribution of aids to navigation, 

 no less than 5,000 lives, on an average, 

 are lost at sea each year. 



WHY GREAT SALT LAKE HAS FALLEN 



By L. H. Murdoch 

 Section Director, U. S. Weather Bureau 



THE rapid decline in the water 

 level of Great Salt Lake during 

 the past few years has caused 

 the people of northern Utah, and more 

 especially those of Salt Lake City, to 

 feel considerable apprehension lest this 

 remarkable body of water will soon be 

 a thing of the past. The reading of the 

 gage at Garfield Beach on December 1, 

 1902, was 3 feet 5 inches below the zero 

 of the scale, showing a fall of t i feet 

 7 inches since the close of 1886, the 

 year in which the last rise terminated, 

 and a level between three and four feet 

 below that of 1847. 



The water level of a closed lake may 

 be affected by a change in the general 

 inclination of its basin, and will fall as 

 the result of increased temperature, de- 

 creased relative humidity, shortage in 

 precipitation, or increased evaporation 

 as a result of spreading the water from 

 inflowing streams over the soil for irri- 

 gation or any other purpose. 



The present fall in the lake is evi- 

 dently due to a combination of shortage 

 in precipitation and the loss of water 

 through irrigation, but the shortage in 

 precipitation is undoubtedly the pre- 

 dominating factor. 



The present area of the lake is about 

 1,750 square miles, and its drainage 



basin is about twenty times that area. 

 The normal annual precipitation for the 

 entire drainage basin is about 14 inches, 

 and the annual evaporation from the 

 surface of the lake is about 5 feet. The 

 report of the Twelfth Census shows that 

 in 1899 the amount of land irrigated in 

 the basin of the lake was 609 square 

 miles, which is a trifle more than double 

 that under irrigation in 1889. 



Flynn's table giving the duty of 

 water in irrigating shows that for Utah 

 the duty is 2.38 acre inches for 10 days, 

 which is 23.80 acre inches for 100 days, 

 or the irrigation season. The writer is 

 not aware that any experiments have 

 been made in northern Utah to deter- 

 mine the loss of irrigation water by 

 evaporation and percolation. The soil 

 in the drainage basin of the Great Salt 

 Lake is generally a sandy loam, which 

 would favor quite rapid percolation, but 

 not very rapid evaporation. Judging 

 from the results obtained in other 

 states, and making due allowance for 

 the low relative humidity of this region, 

 it is believed that 12 inches for evapora- 

 tion and the growing plant is an ample 

 allowance. This would leave 11.80 

 inches to be returned to the lake or its 

 tributaries by subterranean courses. 



The present area of the lake is nearly 



