250 GUIDEBOOK OF THE WESTERN UNITED STATES 
surveys were made for a canal, and in 1859 the State of California 
petitioned the United States Government to cede 3,000,000 acres of 
the land for development. In 1875-76 surveying parties reported 
favorably on a diversion canal passing through Mexico, on practically 
the present route of the main canal, but no concessions were granted, 
and it was not until 1900 that the canal was begun under private 
auspices. In 1901 water was available, and the excellent results 
obtained encouraged a large influx of settlers. The alluring but well- 
fitting name Imperial Valley was given to the region, and its develop- 
ment has been rapid and extensive. .There were many difficulties to 
overcome, such as rapid silting of the canal near the headgates, but 
the worst setback was the breaking of the Colorado River into the 
intake below Yuma in 1904 and 1905. The great river, swollen 
by a winter flood, abandoned its own bed and flowed into the Salton 
Basin through the old watercourses, the Alamo and New Rivers, 
excavating wide channels. With this influx of the river the Salton 
Sea grew rapidly into a great fresh-water lake, and large areas of 
valuable lands and canals were destroyed. It was seen at once that 
unless the flow could be stopped Imperial Valley was doomed. A 
brush mat and piling dam was started after the summer flood had 
subsided, but a later flood destroyed it, and other floods added to the 
difficulty. Late in 1906 the Southern Pacific Co. took control of 
operations, and after one disheartening failure, the use of vast amounts 
of rock brought from quarries was effective in closing the break in 
February, 1907. The cost of this work was estimated at $3,000,000. 
The flooding of Salton Sea necessitated the removal of 67 miles of 
railroad tracks, in places as much as 2 miles, to their present location. 
This flooding was facilitated by the high gradient of 200 feet or 
more in the valley, which gave the water greater declivity than its 
own low gradient down the old main channel to the Gulf of California. 
Soon the greater part of the river’s flow was entering the basin, and in 
a year or more Salton Sea had increased in length to 45 miles and in 
width to 17 miles, with a depth of 67.5 feet and an area of 443 square 
miles. Its northwestern margin extended nearly to Mecca and its 
eastern margin encroached on Imperial Valley. Had the water risen 
pr higher the great irrigation settlement would have been inun- 
ated. 
When the inflow was stopped, in February, 1907, evaporation began 
at once to reduce the lake, and in the next five years the level fell 25 
feet. This fall of 5 feet a year was less than the average annual 
evaporation (about 9} feet), for some water is received from the over- 
flow and seepage of irrigation ditches and some through drainage from 
the surrounding mountains. In 1915 the depth of the water had 
_ diminished to 38 feet, and in 1919 to 30 feet. In the last decade the 
_ water level has ranged from 250 feet below sea level in 1923 and 1925 
