28 
BULLETIN 61, U. S. DEPAKTMENT OF AGRICULTURE. 
sion of saline material, accounts for the variation in the analytical results often noted 
in the reports of analyses of lake waters of the basin. The fluctuations of lake levels 
would also produce a change in concentration and, consequently, the equilibrium 
conditions would be changed also. The more soluble salts are accumulating in these 
lakes while the more insoluble are precipitating out. The principal data concerning 
the chemical content of river and lake waters of the basin are given in Table XV 
(Appendix). 
Much detailed chemical work has been done upon the California rivers by Van 
Winkle and Eaton, 1 and on account of the close proximity of this State to the basin 
region the results of their analyses are of importance. They are given in the table 
which follows: 
Mean analyses, California rivers. 
[Per cent of anhydrous residue.] 
Constituent. 
Humid (22 
rivers); rain- 
fall, 15+ inches. 
Semiarid (16 
rivers); rain- 
fall, 15— inches. 
CI 
Per cent. 
8.95 
14.91 
31.27 
12.53 
15.52 
5.37 
0.12 
11.33 
Pen 
ent. 
7.89 
S0 4 
37.02 
C0 3 
18.87 
Na+K 
12.34 
Ca 
12.83 
Me 
5.76 
Fe ::: 
0.02 
Si0 2 . . 
5.27« 
100. 00 
16.5 
100. 00 
62.7 
From the study of the results the following conclusions are of importance to the 
present inquiry: The total soluble salts in a river water under normal conditions 
varies with the stream flow. They are a minimum for a maximum flow and a 
maximum for a minimum flow. Normal conditions may be assumed to be those for a 
humid region. The components of the total salts also follow the above rule. If we 
take the Yuba River as an example and apply this rule to the various soluble con- 
stituents, we find that chlorine, the sulphate radical, carbonic acid, sodium, and 
calcium follow this rule. Potassium fluctuates; magnesium shows little fluctuation; 
silica remains practically constant. In an arid or semiarid region soluble salts tend 
to accumulate during periods of low water. When the first floods come the river 
water gains in total solids and sometimes to a very marked extent, due to the washing 
out of these accumulated salts. Certain rivers, such as the Santa Ynez and the Owens 
River, maintain the amount of total salts at practically a constant figure. Concerning 
the comparison of the mineral content of waters in semiarid and humid regions Van 
Winkle and Eaton state: 
First. "The average mineral content of waters in semiarid regions is, roughly, 
four times that of waters in humid regions. 
Second. "Difference in percentage composition of the anhydrous residues shows 
that the waters in semiarid regions contain about two-thirds the proportionate amount 
of silica, less calcium; four-fifths as much carbonates, and twice as much sulphates as 
the waters of the humid regions. Their constituents are similar in amount. In 
regions of abundant rainfall disintegration of rock material can not keep pace with 
solution, erosion, and chemical decomposition. The more soluble constituents of 
the rocks are rapidly removed as they become exposed to the action of water, and 
their total amount in a given quantity of the solvent water is seldom great. In arid 
or semiarid regions, however, chemical action is frequently less marked than physical 
disintegration. The soluble materials of the disintegrated rock masses accumulate 
through periods of drought, allowing the water from subsequent rainfalls to take into 
solution a greater relative amount than is found in waters from more humid regions. 
"In the waters studied the average amount of mineral in streams from the semiarid 
regions was 627 parts per million ; in rivers of the humid regions it was 165 parts per 
million. The greatest average mineral content, 2,412 parts per million, occurred in 
Santa Maria River, which flows through a sandstone country receiving barely 10 
inches of rain a year. The smallest amount of mineral matter was found in Merced 
River, 65 parts per million, or about one-fortieth of the amount for Santa Maria River. 
" As the silica content is apparently unaffected by the amount of the other dissolved 
constituents, it may be expected that the percentage of silica in rivers of high dis- 
Water-Supply Paper 237, TJ. S. Geol. Survey. 
