28 SNAKE RIVER PLAINS OF IDAHO. [bull. 190: 
The temperature of the water pouring out of the walls of Snake 
River Canyon shows that it is not derived from deep fissure springs, 
and, in fact, has not made a deep descent into the earth. The water 
no doubt comes from the mountains lying north of the Snake River 
Plains, and is supplied mainly by the subterranean flow of "lost 
rivers." 
Besides the springs in the canyons already referred to, there are a 
few fissure springs on the Snake River Plains, usually near the border- 
ing mountains, which have a high temperature, but their combined vol- 
umes make but slight addition to the surface run-off. Possibly hot 
springs rise beneath the lava sheets flooring the plains and influence the 
temperature of the canyon springs, but there is no direct evidence that 
such is the case, although the temperature of the canyon springs shows 
some variation which can not be due to the depth of the sheets of rock 
from which they appear to issue. 
The springs along Snake River and at a few localities near the moun- 
tains bordering the Snake River Plains have been utilized for irrigation. 
WATER POWER. 
The amount of water power available along Snake River in its pass- 
age across southern Idaho is practically unlimited, but as yet is not 
utilized. The most important falls and their height are as follows: 
Idaho Falls, 30 feet; American Falls, 50 feet;" Twin Falls, 180 feet« 
(PL XXII); Shoshone Falls, 210 feet « (PL IV); Salmon Falls, about 
25 feet. Besides these there are many localities where u vertical 
leaps are made in many cases from 20 to 50 feet, all suggesting, in 
addition to the natural grandeur and sublimity of the surroundings, 
the wonderful possibilities through their utilization in the industrial 
development of the State." 6 
Besides Snake River itself, the great volume of water at The Thou- 
sand Springs and at the mouth of Malade River could be easily and 
cheaply utilized as sources of power. The future greatness of the 
State certainly depends largely on the proper development and use 
of this branch of her great resources. 
IRRIGATION AND AGRICULTURE. 
With the small mean annual precipitation on the Snake River Plains, 
practically all of it falling during the winter season, agriculture with- 
out irrigation is seemingly impossible. As previously suggested, how- 
ever, over the higher portion of the plains lying southwest of Big 
Butte the rainfall may be sufficiently above the average, or the soil 
may retain enough moisture, or possibly the slow melting of the winter 
a From biennial report of the State engineer of Idaho, 1899-1900, pp. 8, 9. 
b Op. cit., p. 9. 
