July 21, 1922] 



SCIENCE 



61 



trol of the mighty floods that are sometimes 

 furnished by its drainage basin and which 

 annually threaten to ovei"whelm and destroy 

 the valleys in its lower reaches. Problems of 

 this kind are presented on every large river 

 flowing through alluvial valleys, but the ease 

 of the Colorado is unique and the flood prob- 

 lem is far more important and imminent than 

 usually is the case. This situation is due to 

 the peculiar topographic conditions of the 

 valleys which the river serves. 



The Gulf of California formerly extended 

 northwestward to a point a few miles above 

 the town of Indio, about 144 miles from the 

 present head of the gulf. The Colorado Eiver, 

 emptying into the gulf a short distance south 

 of the present international boundary, carried 

 its heavy load of silt into the gulf for centu- 

 ries, gradually building up a great delta cone 

 entirely across the gulf and cutting off its 

 northern end, which remains as a great depres- 

 sion from which most of the water has been 

 evaporated, leaving in its bottom the Salton 

 Sea of 300 square miles, with its surface about 

 250 feet below sea level. 



The river flowing over its delta cone stead- 

 ily deposits silt in its channel and by over 

 flow on its immediate banks, so that it gradu- 

 ally builds up its channel and its banks and 

 forms a ridge growing higher and higher until 

 the stream becomes so unstable that it breaks 

 its banks in the highwater period and follows 

 some other course. In this manner the stream 

 has in past centuries swung back and forth 

 over its delta, until this exists as a broad, flat 

 ridge between the gulf and the Salton Sea, 

 about 30 feet above sea level, and on the 

 summit of this the river flows at present, the 

 water flnding its way to the southward into 

 the gulf. 



The direct distance from Andrade on the 

 Colorado River, where it reaches Mexico, to 

 the head of the gulf is about 75 miles, and 

 the distance to the margin of Salton Sea is 

 but little more. As that latter is about 250 

 feet lower than the gulf, the strong tendency 

 to flow in that direction needs no demonstra- 

 tion. This, coupled with the inevitable neces- 

 sity for such an alluvial stream to leave its 

 channel at intervals, constitutes the menace of 



the lands lying about Salton Sea, called the 

 Imperial Valley. As there is no escape of 

 water from Salton Sea except by evaporation, 

 the river flowing into this sea would, unless 

 diverted, gradually fill it to sea level or above 

 and submerge the cultivated land and the 

 towns of Imperial Valley, nearly all of which 

 are below sea level. Any flood waters that 

 overflow the bank to the north must therefore 

 without fail be restrained and not allowed to 

 flow northward into Salton Sea. This is now 

 prevented by a large levee, north of Volcano 

 Lake, extending eastward and connecting with 

 high land near Andrade. This levee is in 

 Mexico and its maintenance is complicated 

 thereby. 



In 1905 the river scoured out the channel 

 of the Imperial Canal and turned its entire 

 volume into the Salton Basin, eroding a deep 

 gorge and raising the level of Salton Sea. It 

 submerged the salt works and forced the re- 

 moval of the main line of the Southern Pacific 

 Railroad. At great diflSculty and expense, 

 after several unsuccessful attempts, the river 

 was returned to its old channel in February, 

 1907. The control of the river would be 

 greatly facilitated if the floods were reduced 

 La volume by storage. Investigations have 

 been made concerning the feasibility of storing 

 the floods and reducing their volume to an 

 amount easily controlled. 



The regulation of the Colorado River has 

 been examined and discussed a great deal. 

 Some engineers have expressed opinions that 

 the storage of the waters of the Colorado 

 should be accomplished entirely in the upper 

 basin and on the tributaries of the river be- 

 cause in those regions good storage sites can 

 be found which will intercept the major por- 

 tion of the water supply and will receive those 

 waters very largely free from sediment and 

 nearly clear, whereas the erosion rapidly in 

 progress throughout the canyon region gradu- 

 ally loads the river with sediment so that the 

 water reaching the reservoir sites below the 

 canyon is heavily laden with sediment. Where 

 the river leaves the canyon region it is esti- 

 mated that it carries on an average about 

 80,000 acre-feet of sediment annually. 



There are, however, many and serious objee- 



