CHEMICAL COMPOSITION OP 1 THE WATER OF SALTON SEA. 



43 



VARIATION IN CONCENTRATION OF THE LAKE AT DIFFERENT POINTS IN 1911. 



From observations on the rate at which the volume of the lake is decreasing, and from 

 calculations on the amount of salt in the lake at the end of each year period, Mr. Free has 

 shown (pp. 30-33) that the increase in salt-content of the lake is greater than can be ascribed 

 to evaporation alone, and that the total amount of salt in solution is increasing instead 

 of remaining constant or decreasing, as might be expected from the deposition of salt on 

 the shores as the water recedes. This increase results, partly at least, from inflowing waters. 

 In order to determine whether or not leaching of salt from the bottom of the lake likewise 

 serves as a factor in this connection a number of samples were collected in 1911 from the 

 surface and from the bottom of the lake at different points, and on the same day as the 

 regular sample was taken. 



The source of the samples, the total solids (dried at 110° C), and the chlorine which 

 they contained are given in table 12. 



Table 12. — Showing varialioti in concentration of the lake at different points in 1911. 



No. of 

 sample. 



Source. 



Extreme northwest end of lake at point nearest Mecca 



Bottom of lake, depth 40 feet, in locality from which regular sample was 



taken 



Surface in middle of lake, opposite Salt Creek 



Bottom of lake at depth of 50 feet; in same locality as No. 3 



Surface in middle of lake, about 10 miles from Pelican Island 



Bottom of lake at depth of 56 feet; in same locality as No. 5 



Surface near Pelican Island; depth of water, 15 feet 



Close to Bhore at mouth of Salt Creek 



From this table it is seen that the lake is remarkably uniform in composition. Sample 

 No. 1, which has a higher salt-content than any of the others, was collected in a very 

 shallow place near the shore. The sand on the shore at this point is covered with an 

 incrustation of salt for a considerable distance back. Some of this salt must be washed 

 back into the lake again by occasional rains, which would account for the high result found 

 for the salt-content of the water at this place. 



The shore at the mouth of Salt Creek is very rocky and steep, and no deposit of salt 

 could be seen at this point. Sample No. 8, collected near the shore at this place, shows 

 the same concentration as the main body of the lake. Sample No. 4 was taken from the 

 bottom of the lake at a point as near to the old salt beds as could be determined. The 

 agreement between the salt-content of this sample and the other samples from the main 

 body of the lake makes it improbable that any appreciable leaching is now taking place; 

 consequently, any increase in the total salt-content which may be taking place must now 

 be due principally to inflowing waters. 



COMPOSITION OF THE SALTS LEACHED OUT FROM THE BOTTOM OF SALTON SEA. 



In 1900 R. H. Forbes and W. W. Skinner made, at intervals of two months, seven 

 analyses 1 of composites of samples collected almost daily from the Colorado River at 

 Yuma, between January 10, 1900, and January 24, 1901. The mean of these analyses 

 represents the average composition of the Colorado River for an entire year, but not the 

 average composition of the total water discharged by the river, since its volume varies 

 greatly at different seasons. 



Bull. Ariz. Agri. Expt. Sta., No. 44. 



