National Geographic : 1907 Jan
THE NEW INLAND SEA* BY MR ARTHUR P. DAVIS ASSISTANT CHIEF ENGINEER, U. S. RECLAMATION SERVICE MANY centuries ago the Gulf of California extended to a point about 150 miles northwest ward from its present head. It also ex tended up the present valley of the Colorado River at least to Yuma and probably somewhat above. The Colo rado River, rising in the Wind River Mountains of Wyoming and the Rocky Mountains of Colorado, carved the rocks along its course and brought the result ing sands and mud down in its swift current, discharging them into the arm of the gulf near Yuma. As this process went on, without cessation, century after century, the valley was gradually filled, a delta built up, over which the river flowed far out into the gulf. It en croached progressively upon the shores of the gulf until it built up a delta en tirely across, joining the foothills of the Cocopah Mountains on the western shore. This cut off the head of the gulf, and the arid climate rapidly evaporated the waters thus separated and left an inland depres sion, which at its lowest point was nearly 3oo feet below sea-level. f The river continued to bring down its load of sediment and to build its delta higher and force it farther into the gulf. Like all such deltaic streams, the channel on the top of the delta is constantly shift ing, cutting one bank, building up the other, overflowing both banks, and during high water sometimes entirely abandon ing an old channel for a new one. In this way the river has from time to time flowed into the Salton Sea for some years or centuries, and anon has shifted to the eastward and discharged again into the gulf. This is the general course the river has followed ever since its dis covery by the Spaniards in the i6th century. At high water the river nor mally overflows its banks in the valley regions all the way from the Grand Can yon to the Gulf of California. In un usually high water, such as occurred in 1891. , the overflow running into the Sal ton Sink has been sufficient to materially raise the level of the lake and overflow the tracks of the Southern Pacific Rail way, which are built along its shores. THE IRRIGATING COMPANY RESPONSIBLE FOR THE BREAK The ease of diverting the Colorado River near the international line and con ducting the water through natural chan nels to the Colorado Desert for irrigation has been recognized for many years, and various attempts to promote this project have been made from time to time, usu ally, however, without success, owing to the international complications involved. About 1891 Mr C. R. Rockwood, a civil engineer, made plans for the con struction of a headgate in rock at the foot of Pilot Knob, just north of the Mexican line, and of a canal to carry the water to the so-called Alamo River, an ancient channel of the Colorado which, by lapse of centuries, had been nearly filled with sand and sediment. Efforts to promote this project were for nearly 10 years unsuccessful, but finally a small amount of money was raised, which, however, was insufficient for the con struction of the works as planned. The promoters then concluded simply to cut the dirt banks of the river and lead the water by a small canal into an old chan nel, whence it flowed into the Imperial Valley without additional construction. A cheap wooden headgate was built in the canal near the river and was for a * An address to the National Geographic Society, November 23, 1906. t It is estimated that the amount of silt carried by the Lower Colorado River is sufficient to cover 53 square miles one foot deep with dry alluvial soil each year.