POTASH SALTS AND OTHER SALINES IN THE GREAT BASIN REGION. \j 
Basin river streams may be divided into three types: 
(1) Streams characteristic of the higher mountains. These are short streams which 
take care of the winter precipitation and carry their waters to the outwash slopes to 
be distributed by the porous detrital fans. 
(2) Streams, such as the Amargosa, Reese, and Quinn Rivers, which reach main 
basins but do not carry sufficient water to make a continuous flow, or which reach basins 
of such magnitude that they can not form permanent lakes. 
(3) Streams which supply permanent lakes. The drainage of the Sierra Nevada 
and Wasatch Mountains supplies practically all of these lakes. Owens, Mono, Carson, 
Walker, Pyramid, Honey, and the lakes of southern Oregon are typical examples of 
such lakes in the west; while Great Salt Lake, Utah Lake, and Sevier Lake are in the 
east and are supplied by the drainage of the Wasatch Mountains. 
A list of these lakes, together with elevations and drainage area of basins, is given in 
Table VIII (Appendix). 
The proportion of the annual precipitation which appears as run-off varies in different 
basins. The length of the stream and the character of the watershed, as well as local 
climatic conditions, determine this factor. The following table summarizes the run-off 
factor for the Carson, Walker, Truckee, and Humboldt Rivers. 
Proportion of rainfall distributed in the run-off. 
River basin. 
Average 
rainfall, 
mean 
annual. 
Run-off. 
Run-off in 
percentage 
of average 
rainfall. 
Carson 
Inches. 
11.5 
11.5 
Inches. 
6.25 
2.63 
54.3 
East Fork Walker .' 
22.8 
Truckee , 
23. 82 9. 18 
38.9 
8.12 
10.31 
0.25 
/ i 0. 71 
\ » 1. 19 
3.07 
16.80 
2 11.50 
i By calculation based upon the total mean annual stream flow, plus an additional amount estimated 
at one-half the known amount for the flow of the streams upon which no data are available. 
1 By calculation based on an assumed rate of evaporation of the water from the lakes into which the 
rivers flow. 
In addition, an attempt has been made to calculate the probable total run-off for 
the whole basin region. The first calculation is based upon the total mean annual 
stream flow plus an arbitrary amount for the flow of the streams upon which no data 
are available. The additional amount has been estimated as one-half of the known 
amount. This gives a run-off equivalent to 0.71 inch, or 6.8 per cent of the total 
precipitation. The second calculation is based on an assumed rate of evaporation 
of the water from the lakes. The total area of lake surface is 4,196 square miles. 
Assuming an annual evaporation of 60 inches gives an annual run-off of 1.19 inches, 
or 11.5 per cent of the average annual precipitation. The latter figure is un- 
doubtedly high, as in the southern half of the Great Basin the run-off is practically 
zero. For instance, the Amargosa River is a typical desert stream and flows only 
at rare intervals and during periods of excessive precipitation. At other times water 
occasionally rises in springs from the dry bed, flows a -short distance, and then 
sinks. The run-off for this whole southern area must be less than 1 per cent. 
As more than 50 per cent of the area of the Great Basin is flat, or characterized by 
slopes of low angles (0 to 5°), it may be assumed that for areas of this nature, 'receiv- 
ing 10 inches or less mean annual rainfall, the run-off is practically zero. For the 
basin ranges themselves the run-off can not be in excess of 50 per cent, and it is prob- 
ably much less. Much of this run-off is absorbed by the outwash slopes. We may 
take the Humboldt River as an example to illustrate this point. This stream rises 
in the Ruby Range, upon which there is considerable precipitation. At Oreana the 
mean annual flow gives a run-off of 0.25 inch (drainage area, 13.800 square miles), or 
3.07 per cent of a mean annual rainfall of 8.12 inches. This means that most of the rain- 
fall in the mountains along the course of the Humboldt is absorbed before it can reach 
the main river. 
_ The basin region may be divided into mountain area, outwash area, and combined 
silt and playa areas. These approximate 50, 20, and 30 per cent, respectively, of the 
total area. An inspection of the precipitation tables given on a preceding page shows 
