94 



GUIDEBOOK OF THE WESTERIST UNITED STATES 



ancient Lake Bonneville, described below by G. K. Gilbert/ in an 

 apron of mountain waste; the main residence section rises eastward 



* At Ogden the traveler is fairly within 

 the Great Basin, and for 590 miles, until 

 he reaches the crest of the Sierra Nevada, 

 his coiu'se traverses a series of closed val- 

 leys — ^valleys which resemble basins In 

 the fact that all parts of their rims stand 

 higher than their middle parts. All 

 streams of this region either lose their 

 water by direct evaporation or discharge 

 it to gome lake that serves as an evap- 

 oration pan. Some of the lakes have 

 outlets, but every such outflowing stream 

 flows into another lake, and the final 

 receptacle has no outlet, all the water it 

 receives escaping upward, into the air. 

 No stream in the Great Basin finds its 

 way to the ocean. 



Great Salt Lake has no outlet. Jordan 

 Kiver, which enters it from the south, 

 is the outlet of Utah Lake, Bear River, 

 coming from the north, carries the out- 

 flow fi'om Bear Lake. The waters of 

 Utah and Bear lakes and of Jordan and 

 Bear rivers are fresh, and so is the water 

 of Weber River, the third great tributary 

 of Great Salt Lake, but the lake into 

 which J:he three rivers flow is saline. It 

 is saline becauee it has no outlet. The 

 fresh waters of the rivers contain some 

 saline matter, but the quantity is too 

 small to be discovered by taste. As 



parts pel 

 minute 



total 



volume of water brought by the streams 

 to the lake in a year their biuden of 

 Kiline matter is found to be really great, 

 amounting annually to more than 500,000 



tons. Year by 

 century tiie wat 



and century 



the lake is evaporated, but the dissolved 

 solid? can not escape in that way and 

 therefore remain. They have accumu- 

 lated until the lake water is approxi- 

 mately saturated, holding nearly as 

 much mineral matter as it can retain 

 in solution. The lake contains over 

 5,000 million tons of common salt and 

 900 million tons of Glauber's salt, or 



sodium sulphate, aa well as other mineral 

 matter. 



[ Another consequence of the lack of 

 outlet is that the lake varies from time to 

 time in size. Whenever the gain from 

 inflow is greater than the loss from 

 evaporation the level of the water surface 

 rises; when the loss is greater it falls. 

 Each year there is a rise, beginning in 

 winter, when the cool air has little power 

 to absorb moistiue, and continuing 

 through spring, when the rivers are 

 swollen by the melting of snows in the 

 mountains. Each year there is a fall, 

 beginning in summer, when the liot air 

 rapidly absorbs the water, and continu- 

 ing in autumn, w^hen the rivers are 

 smallest. This annual oscillation amounts 

 on the average to about 16 inches. 



In some years the rainfall and snowfall 

 are greater than in others, and then the 

 lake usually receives more water than it 

 parts with, so that the surface is left 

 higher than it was before. In a series of 

 wet years the lake level progressively 

 rises; in a series of dry years it progres- 

 sively falls; and as the rainfall is irreg- 

 ular the fluctuations of the lake are con- 

 spicuous. Since definite knowledge of 

 the lake began, in 1850, there have been 

 five periods of increase and four of de- 

 crease. (See fig. 11.) The summer lev- 

 els of 1868 and 1877 were more than 10 

 feet above the summer level of 1850, and 

 those of 1903 and 1905 were 4 feet below 

 that of 1850. The level of 1914 was 6 

 feet above that for 1905. 



The land bordering the lake has in 

 many places a slope so gentle that a 

 small change in the height of the water 

 surface makes a great change in the area 

 of the lake. On a map completed in 

 1850 the area shown is 1,750 square miles; 

 on a map made in 1869 it is 2,170 square 

 miles. In the interval between the two 

 surveys the lake had risen 10 feet, and 

 this rise enlarged the area about 24 per 

 cent. From the greater smiace the 

 evaporation was of coin^e greater, and 

 the dependence of evaporation on area 

 is thus an important factor in regulating 

 the size of the lake. The effect of a long 

 series of wet years is somewhat reduced 



