130 THE DATE PALM. 



The position of the larger bodies of easily irrigable land lying along 

 the Colorado River is shown in fig. 10, p. 102. The cross-hatched areas 

 in this figure along the river indicate low-lying lands, and are more 

 extensive than the flood-plain proper, although in very high flood most 

 of the areas marked on the map would be overflowed. All these lands 

 are easily irrigable without expensive diversion works, which would 

 be necessary were the water to be conducted to the mesas overlooking 

 the Colorado. The land comprised in these areas amounts to some 800 

 square miles, 05 distributed as follows: 



Square miles. 



Cottonwood Valley in Nevada and Arizona 14 



Mohave Valley in Nevada, California, and Arizona 160 



The small valleys near the junction of the Bill Williams River 56 



The great Colorado Valley in California and Arizona 382 



The valley in California and Arizona just above the junction of the Gila River 



at Yuma 80 



The valley on the right bank of the river below Yuma in Arizona 108 



There is a large area of similar land in Mexico along the Colorado 

 River, as may be seen from the sketch map, fig. 10, p. 1 02. 



Recent detailed surveys made by the Hydrographic Office of the 

 Geological Survey b show that there are between 400,000 and 500,000 

 acres of irrigable land in the valley of the Colorado River between 

 Fort Mohave and Yuma, and there are in addition large areas of land 

 in Arizona below Yuma already irrigated, while still more can be put 

 under water at slight expense. The flood-plain proper, naturally irri- 

 gated by the annual overflow of the river, does not comprise so exten- 

 sive an area, but nevertheless embraces several hundred square miles 

 of the very richest of these exuberantly fertile alluvial soils. 



Of the 100 square miles (63,469 acres) surveyed in 1902 in the Colo- 

 rado River Valley south of Yuma, Ariz., Holmes says: "About To per 

 cent of the lands of the valley are overflowed and a layer of sediment 

 added to the soil each year. The deposition has been much greater 

 near the present stream bed than farther back, so that the lands 

 immediately bordering the stream are higher and covered by only a 

 few inches of water during the flood season, while those farther back 

 may in places stand under 7 or 8 feet of water." 



The land near the river is usually nearly free from alkali, which 

 occurs ehielly "just above the high- water line of present overflow, 

 where evaporation from the surface has taken place without any sur- 

 face flooding, showing plainly that the alkali is the result of the 



An estimate of 700 square miles is made by Whipple, Pac. Ry. Rept., vol. 3, 

 Pt. I, pp. 40-41, to include the lands from Fort Mohave to Yuma. 



&Lippencott, J. B., and Davis, Arthur P. Colorado River Division in Arid Land 

 Reclamation Service, First Annual Report, 1903, pp. 106-125. 



c Holmes, J. Garnett. Soil Survey of the Yuma Area, Arizona. In Field Oper- 

 ations of the Bureau of Soils, Fourth Report, 1902, p. 781. 



