SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 31 



of soluble salts per 100,000. The water from wells in the river bot- 

 tom is usually higher in soluble salts, the proportion ranging from 

 120 to 160 parts per 100,000. In a numl)er of instances there are 

 indications of sodium carbonate. Most of the wells in the desert 

 section tap a strata giving moderate supply of water at depths rang- 

 ing from 125 feet downward, the water rising in the wells to within 

 35 feet of the surface. 



The United States Indian Office has quite thoroughly investigated 

 and developed the water supply for parts of the Indian reservation 

 within the area. Most of the water is obtained from the Gila River 

 and conducted to the land by a system of main ditches and laterals, 

 wells supplementing the gravity water supply during the dry season. 

 A series of nine wells supplying 25 second- feet extends across the 

 Santan District, and furnishes water for a main ditch when the 

 river supply is short. A well at Sacaton supplements the river sup- 

 ply for the experimental farm of the Bureau of Plant Industry and 

 that of the Indian agency. Another series of wells is used to irri- 

 gate the United States Indian seed farm near Sacaton, no gravity 

 water being applied. 



The amount of water necessary to mature crops in this region de- 

 pends largely on the situation of the land, the nature of the soil, and 

 the crop grown. Areas in the river bottoms require less water than 

 those in the desert, and the heavier textured soils produce good yields 

 with less water than the types of more open structure. Many of the 

 bottom lands are naturally subirrigated, but this condition is likely 

 to be accompanied by accumulations of alkali, which is brought to 

 the surface through the capillary rise and evaporation of soil water. 

 Surface irrigation is beneficial on the subirrigated soils, as this tends 

 to wash the salts into the subsoil. 



Alfalfa requires much w ater for maximum yields, one flooding for 

 each cutting being necessary during the dry season. Other crops 

 such as grain and grain hay require less water, as they mature early. 

 Cultivated crops like corn, cotton, truck, and tree fruits require water 

 during the growing season, and this is applied by the furrow method. 



Most of the irrigated land lies in the Gila River bottoms and in- 

 cludes Indian allotments as w^ell as large ranches. Only small 

 patches are cultivated in the desert section, but farming centers are 

 developing in the vicinity of Florence and Casa Grande. The de- 

 velopment of the greater part of the agricultural area outside the 

 stream bottoms will i^robably depend upon effective storage of the 

 Gila River waters. 



DRAINAGE. 



The natural drainage in the Gila River bottoms, where most of the 

 agricultural development has taken place, is poor. These lands lie 



