The Arizona sentinel., 1908-08-12
Irrigation of
 Yuma Valley
Day Allen Wiley iu Scientific American.

interesting projects connected
 with the reclamation of arid ter
 ritOry in the Southwest is tech
 nically known as the Yuma pro-
 iect, as it is intended to irrigate
 an extensive territory located in
 the Yuma valley and bottom
 lands adjacent to the Colorado
 and Gila rivers in the States of
 California and Arizona. As is
 we'll known, the Colorado forms
 the western boundary of Arizona
 and a portion of the southern
 boundary of California. The
 Gila river enters it from the east
 a short distance from the town
 of Yuma in the extreme south
 western corner of Arizona. These
 two water courses provide an
 abundant supply for the area to
 be irrigated, which for the pres ent will comprise about 100000 acres. The topography of the country and it's form ration make the work of constructing dams, canals, and suitable storage res ervoirs unusually difficult. There is no natural formation of which engineers can take advantage, as in many other portions of the West, where nature has thrown up rock walls which can be util- ized in storing the water supply. As readers of the Scientific American are well aware, the Colorado has been forming a bed for itself, annually carrying down an immense amount of silt in So- lution, which is deposited along it's course. The channel of the Gila is somewhat similar to the Colorado, and this stream also is subject to very sudden and eX treme changes in the volnme of water, so that especial care must be taken to protect irrigation works against floods.
 When the question of irrigat- ing these bottom lands of Cali fornia and Arizona was consid- cred in 1904, the engineers of the bureau of reclamation decid- ed that the best way to construct permanent works would be to erect diversion dam across the Colorado river at a point below where the Gila flows into it. It would be necessary, however, in the opinion of the engineers, to have elaborate protection for the dam and entertainments large enough and of sufficient strength to cOntine the waters of the riv- CTS when Tn flood. The problem to be solved was how to secure a foundation for the levees and l other works, and form of pro- tection against the flood waters which would prevent the barri- iers from being damaged if not entirely washed away by the flood currents. The plan adopt ed was decidedly unique from an engineering standpoint, as 1t was decided to depend upon earth works guarded by wooden dams or abatiseS to check the flow of water against them. When it is stated that the levees considered necessary will when completed extend @ distance of nearly ,75 miles on the Colorado and Gila rivers, an idea of the magnitude of this work alone can be gained.
 The diversion dam or Laguna dam, as it is called, will extend for distance of 1, 78O feet across the Colorado at a point 12 miles from the town of Yuma. Owing to the friable foundation of. the river channel, the dam is of enormous width ln proportion to its other dimensions, being 267 feet wide on the bottom, though but 19 feet in height. It will re- quire 356, GOO cubic yards of con- crete to complete and have dis placement in the water equal to the weight of 6O0,O0O tons. This may be called the main work and it is about twO-thirds completed at the time of writing. Before