OCR Text |
Show also given consideration to a multiple-purpose reservoir with power at the Buttes site, which would be utilized by the Bureau of Reclamation's Central Arizona Project. A total of 10 power developments in the Colo- rado River Basin have been recommended or pro- posed in reports by the Bureau of Reclamation or the Corps of Engineers. The usable storage capac- ity that would be provided at these projects amounts to about 3.5 million acre-feet (table 3). Navigation Neither- the Colorado River nor any of its tribu- taries has been improved for navigation. Rec- reation craft are in use on Lake Mead and others of the larger reservoirs in the basin, and certain reaches of the main river are traversed infrequently by rowboats and outboards, but no water-borne freight traffic exists in any part of the basin. How- ever, improvement of navigation was included as one of the main purposes in the authorizations of Hoover, Parker, and Davis Dams. Flood Protection Existing Improvements, Character, and Area Protected Most of the Colorado Basin is so sparsely occu- pied that floods do negligible damage to urban property and only slight damage to agricultural lands. The major exception is in the extreme lower end of the basin, where the Colorado itself has flooded disastrously in the past and where flood danger still exists on some of the tributaries, the most important being the Gila and Bill Williams Rivers. Levees have been built on the lower Colorado River in tlie Colorado River Indian Reservation by the Bureau of Indian Affairs, in the Palo Verde Val- ley by locaJ interests, in Yuma Valley by the Bureau of Reclarmation, and in Mexico principally by United States interests concerned with the protec- tion of th.e Imperial Valley. The inadequacy of these levees in the control of Colorado River floods was a major influence in the demand for the Hoover Dam project. Hoover Dam was completed in 1936 by the Bureau of Reclamation for the multiple purposes of irrigation, municipal water supply, power development, improvement of navigation, and flood control. Dams on the rivers below Hoover Dam that have storage provide some con- trol of local floodwaters. In general, only minor flood control improvements have been constructed elsewhere in the basin. A levee project constructed by the Corps of Engi- neers on the Little Colorado River affords protec- ion from floods to the town of Holbrook, Ariz. The project, completed in December 1948, consists of a levee more than a mile in length on the right bank of the river to protect the town and the main line of the Santa Fe Railway. Facilities in Construction and Authorized No flood control projects are now under con- struction in the basin by the Corps of Engineers. The construction of Hoover Dam substantially relieved the lower Colorado River area and Impe- rial Valley from the menace of all but extreme floods from the upper part of the river. However, the drainage area above Hoover Dam is but 167,800 square miles of the total drainage area of 242,000 square miles at the international boundary. Two principal lower tributaries, the Bill Williams River and the Gila River, at present may discharge large floods into the Colorado River below Hoover Dam and very seriously damage lands and cities along the river in Arizona and Mexico and in the Im- perial Valley. The Corps of Engineers has recom- mended and Congress has authorized two projects to provide protection against floods in that area. Alamo Dam and Reservoir on Bill Williams River, Ariz., is authorized for flood and sediment control. Total storage would amount to 946,000 acre-feet, and the reservoir would control 4,770 square miles of drainage area. The control of sedi- ment would have an important effect in reducing the deposition in Lake Havasu above Parker Dam. The project is designed for inclusion, if found ad- visable, of water conservation storage and hydro- electric power development at a later date. Painted Rock Flood Control Basin on the lower Gila River would provide 2,480,000 acre-feet of storage for the control of sediment and of Gila River floods from a drainage area of 50,800 square miles. It is particularly important as a unit for the protection of Yuma, Ariz., the rich irrigated land in that vicinity, and Imperial Valley, Calif. The project is a part of a coordinated plan involving the Bureau of Reclamation and the International Boundary and Water Commission and is also signifi- 374 |