Page 7


Page 7
Colorado River problem
Is Part Of,8
Full text
THE COLORADO RIVER PROBLEM 311 this levee. The levee crosses several old meanders of the river and, consequently, is subject to attack by it at nearly every high water. Bank protection has been necessary to maintain the levee, and the bank is now revetted practically throughout its entire length. The levee has been breached by the Colorado River floods once (in 1913) and was overtopped at its lower end by the Gila flood of January, 1916. Another 54,000 acres lie in Yuma Valley on the Arizona side between the Town of Yuma and the Mexican Boundary. These lands were subject to overflow at high water and have been protected by a levee 25 miles long, extending from Yuma to the Mexican Boundary. A Government railroad has been built on this levee in order to facilitate its maintenance. For 12 miles below Yuma, the river flows in a narrow and relatively straight channel with fairly stable banks and has never given much flood trouble. Below that point, it shows a determination to repeat its meandering into the land now occupied by the Project. Since 1909, the river has made direct attacks on this levee at 12, 16, and 24 miles below Yuma, necessitating heavy expenditure for bank protection. The levee has never been overtopped, but has twice failed from undercutting, once from the Gila flood of January, 1916, and once from the Colorado River flood of 1920. The construction and maintenance of the levees of the Yuma Project cost $3,234,470. The annual maintenance for the past six years has averaged $86,420. The remainder of the lands in the Project, about 45,000 acres, are on the mesa east of Yuma Valley, well above high water. The Yuma levees are nearer the river than has been found to be economically practicable elsewhere. They encroach on a part of the valley that the river has used in the past and will try to use in the future. They can be maintained in their present location only by heavy bank protection, and maintenance expense will be high until the banks are sufficiently protected whether or not flood storage is provided. (See Fig. 2.) Imperial Valley.—The Imperial Valley (see Fig. 3) comprises about 515,000 acres of irrigable land in California and 255,000 acres in Mexico. During 1923, about 400,000 acres of the area in California and about 170,000 acres in Mexico were irrigated. All this highly productive area lies below the low-water level of the river and much of it below sea level. Water is diverted for irrigation at Rockwood Heading about a mile up stream from the International Boundary line. The main canal follows generally an old flood channel called Alamo River. The Valley was first protected from flood waters by the head-works of the canal and by an embankment on the river side of the canal. This embankment now forms a secondary line of defense. It was supplemented by a stronger line of defense consisting of the levees of the California Development Company, Sais Levee, extending from the canal intake south along the river for about 10 1/2 miles, thence bearing west for about 16 miles, and the Volcano Lake Levee north of Volcano Lake from high ground west of the Valley to the Inter-California Railway Company embankment and the Imperial Canal near Bataques Station. In 1905, the Imperial Canal had silted, for about 4 miles below the Heading, to such an extent as to threaten a water famine during the low-water period. In order to get water into the canal, a cut was dredged to turn the river into it

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