STUDIES ON THE RATE OF EVAPORATION 



AT RENO, NEVADA, AND IN 



THE SALTON SINK 



By Professor Frank H. Bigelow 



U. S. Weather Bureau 



THE southwestern United States, 

 from southern Utah and Colo- 

 rado, including Arizona and 

 New Mexico, to southern California, is 

 the wonderland of North America. Here 

 are found several hundred square miles 

 of petrified forests, the surface of the 

 ground being covered with agate tree 

 trunks and chips ; the largest natural 

 bridge in the world, 500 feet span, 200 

 feet high/and 600 feet wide; the greatest 

 examples of volcanic action, with 50 

 miles of lava in sheets 1,500 feet thick; 

 the most impressive villages of cave- 

 dwellings in the world ; the many-storied 

 cliff -houses of aboriginal architecture ; 

 the communes or town republics and the 

 pueblos of the Acoma and Moki Indians ; 

 the most notable tribes of nomad Indians, 

 the Navajos and Apaches, who are the 

 best fighters of the savage world ; and the 

 remarkable ruins of the great stone and 

 adobe churches of the Franciscan mis- 

 sionaries. 



The greatest wonder of all is the work 

 of erosion performed by the Colorado 

 River in its course from Utah to the 

 Gulf of California, a distance of 2,000 

 miles. At present it flows through the 

 Grand Canyon in a narrow gorge about 

 1,300 feet deep below the first level of 

 the valley ; but this valley itself is sur- 

 rounded by cliffs and pinnacles rising 

 5,000 to 6,000 feet above the water of 

 the river; also, passing from the rim 

 of the canyon along the open prairie to 

 the mesas, or tables, still marking the 

 ancient levels of the plateau, yet another 

 thousand feet must be added. The geo- 

 logical evidence shows that more than 

 30,000 feet of rock have been carried 

 away in some places, and that over a 



region covering 200,000 square miles at 

 least 6,000 feet have been transferred to 

 the ocean. 



The cutting of the gorge through 800 

 feet of black gneiss, 800 feet of quartz, 

 500 feet of sandstone, 3,600 feet of lime- 

 stones of various kinds, and 1,000 feet 

 of gypsum mixed with limestone is a 

 manifestation of water power hard to 

 appreciate. 



The Colorado River drains the snow 

 water of the Rocky Mountains and the 

 plateau southwestward, and has gradually 

 transported this immense mass of material 

 into the Gulf of California. In ancient 

 days this gulf extended about 150 miles 

 farther north, between the San Jacinto 

 and the San Bernardino Mountain ranges, 

 and the beach lines of this old sea can be 

 readily traced upon the sides of the 

 mountains 15 feet above sea-level. The 

 river entered the old Gulf of California 

 at Yuma, Arizona, and it has gradually 

 built a delta of silt and. debris directly 

 across the gulf, so that the northern end 

 of the ancient depression has been en- 

 tirely cut off from the Pacific Ocean and 

 its waters. This sink is now about 285 

 feet below sea-level in the Salton Sea, 

 while the delta floor is 20 to 40 feet above 

 sea-level. 



The waters of the Colorado River pass 

 through a narrow channel at the heads 

 above Yuma and flow along the top of 

 the delta in channels which are readily 

 shifted to the north or the south, this 

 being the natural way to spread more soil 

 over an ever-widening delta back. The 

 gradient of flow is steeper northward to' 

 the Salton Sink than it is southward to 

 the Gulf of California, and hence any 

 flowing of the river to the deep sink is 



