90 CARNEGIE INSTITUTION OF WASHINGTON. 



EREMOGRAPHY: THE SALTON AND MOHAVE DESERT REGIONS. 

 The Recession of the Salton Sea, by D. T. MacDougal. 



A series of gage-readings of the level of the water is taken weekly 

 by officials of the Southern Pacific Railway, and the data have been 

 sent to this Department. It appears from these records that the 

 recession was but 2 inches in July 1914, 19 inches in August and Sep- 

 tember 1914, 5 inches in October 1914, 6.5 inches in all during the 

 following November, December, January, and Februar}-, 7.5 inches in 

 March and April 1915, 4 inches in May 1915, and about the same in 

 June 1915. 



The total for the year ending July 1, 1915, was about 50 inches, which 

 is about the average annual recession for several years previous, but is 

 more than in the previous year. The erratic rate of recession is to be 

 attributed to local rains and to the overflow from irrigation systems. 

 The irregularities noted above make it difficult to follow the occupa- 

 tions and successions of the beaches now being exposed. 



It is to be noted that the calcium deposition indicated by the chem- 

 ical analysis no longer takes the form of deposits on stems and other 

 emersed objects. 



Composition of the Salton Sea Water, June 8, 1915, by A. E. Vinson, 



The annual analysis of the water of Salton Sea has not been com- 

 pleted at this time, but several determinations of considerable interest 

 are available. The total solids have increased 16.8 per cent and now 

 amount to 1,377.4 parts per 100,000. This is somewhat less concentra- 

 tion than has occurred in former years, but a considerable volume of 

 fresh water flowed into the Sea from the Colorado River last winter. 

 The constituents that have been determined are given in the following 

 table : 



Composition of Salton Sea Water, June S, 1915 {in parts per 100,000). 



Total solids 1377.4 



Sodium 441.60 



Potassium 5.12 



Sulphuric (SO4) 174.47 



Bicarbonic (volumetrically)^ 16 . 62 



Carbonic total (gravimetrically)* (11.98 CO2) H 92 



Oxygen consumed^ . 208 



^Determined by Dr. H. A. Spoehr. 



The elements show a fairly uniform concentration from year to year, 

 with the exception of calcium and potassium. Calcium has been 

 deposited in the form of tufas, but the history of potassium is less 

 evident. In 1912 there was no concentration of this element and the 

 following year there was a loss, although sodium had concentrated 

 18.8 and 19.3 per cent, respectively^, for the years under consideration. 

 In 1914 the disappearance of potassium, which had been so evident 

 for several years, ceased, and this element showed ahnost the normal 



