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The National Geographic Magazine 



three times that of the land under irri- 

 gation. With precipitation at normal, 

 the loss of 12 acre inches of water by 

 means of irrigation should therefore 

 produce the first year a fall of four 

 inches in the lake level, and a decreas- 

 ing fall every year thereafter until a 

 balance would be reached between the 

 area of the lake and the amount of 

 water it received, when no further fall 

 would occur as a result of irrigation. 



The problem is necessarily a very in- 

 tricate one, and at best only general 

 results can be obtained from the most 

 careful calculations. The writer, how- 

 ever, feels confident that irrigation can- 

 not be charged with more than three or 

 four feet of the last decline in the lake 

 level. It should be borne in mind that 

 irrigation began in 1848, and was in 

 operation during the years the lake rose 

 rapidly and maintained a high level. 



The precipitation data for Salt Lake 

 City, including that for Ft. Douglas, are 

 complete back to 1863, with the excep- 

 tion of 1866, and that has been approx- 

 imated at 22.25 inches. The average 

 precipitation for this locality, using all 

 the data up to the close of 1901, is 16. 65 

 inches. 



From 1865 to 1886 a wet cycle pre- 

 vailed, and during that time the average 

 annual precipitation was 18.42 inches, 

 or 1.77 inches above the normal. From 

 1887 to 1902 a dry C3^cle has prevailed, 

 the average precipitation during this 

 period, estimating the precipitation for 

 December of 1902 at normal, being 14.80 

 inches, or 1.85 inches below normal. 



During the wet cycle the lake rose 

 rapidly from about 3 feet in 1864 to 

 about 13 feet in 1868. A decline then 

 followed, but the reading was nearly 13 

 feet again -'in 1876. The last rise ter- 

 minated in 1886, when the level of 9 

 feet 2 inches was reached. Since 1887 

 there has been a steady decline in the 

 level, the total fall from the close of 

 1886 to the close of 1902 being nearly 

 12 feet. 



With the annual precipitation reduced 

 to 14.8a inches at Salt Lake City, the 

 lake would not fall without limit, but 

 after a number of years, as in the case 

 of the loss resulting from irrigation, a 

 balance would be reached between the 

 area of the lake and its inflow and the 

 decline would thereupon terminate. 



The fall in lake level has been much 

 more rapid during the past three years- 

 than for any like period during the pre- 

 ceding years of drouth. This is mainly 

 due to the fact that the deficiency in 

 precipitation has been greater during 

 this period than during anj T similar 

 period of the present dry cycle. The 

 precipitation record at Salt Lake City 

 for 1 90 1 does not fairl}- represent con- 

 ditions for the entire basin. From May 

 2 to 4 4.08 inches of rain fell there, but 

 the excessive rainfall covered only Salt 

 Lake, Davis, and small portions of ad- 

 joining counties, about one-twentieth of 

 the basin, while the rainfall for other 

 portions was comparatively light. The 

 rise in the lake during the two weeks 

 ended May 15 was only 1 inch, no more 

 than would be expected though no pre- 

 cipitation had occurred. If the precip- 

 itation at Salt Lake City for 1901 were 

 to be approximated from that of the 

 rest of the basin, it would have to be 

 placed at about 1 3 inches. This would 

 make the deficiency for the last three 

 years alone over 13 inches. 



The lake is not alone in showing the 

 effects of the drouth. Streams, springs, 

 and artesian wells are drying up, and 

 those which continue active are dis- 

 charging much less water than a few 

 years ago. 



While it is difficult to demonstrate 

 mathematically just how much fall in 

 the lake level is due to irrigation and 

 how much to a shortage in precipita- 

 tion, it seems to the writer that the large 

 deficiency of 29.60 inches in precipita- 

 tion during the past sixteen years, as 

 shown by the Salt Lake City records, 

 must be far more of a factor than any 



