10 



FIELD OPERATIONS OF THE BUREAU OF SOILS, 1903. 



A considerable part of the water supply comes from melting snow, 

 springs, and mountain streams near the source of the Gila River, and 

 an important part from the tributary Gila Bonita, Prieto, and Blue 

 creeks, and the San Francisco River, all emptying into the river above 

 Solomonsville. 



San Simon River, which enters the Gila near Solomonsville, is ordi- 

 narily an insignificant and poorly defined water course. It drains a 

 large extent of country known as the San Simon Vallej 7 , lying in the 

 southeastern part of the Territory, and is subject to sudden and 

 heavy floods. At such times vast quantities of a very fine, heavy silt 

 are brought down and deposited in the lower vallej 7 , and in that part 

 of the Gila Valley tying between Solomonsville and Safford. 



SOILS. 



The extent and position of the different soil types of this area are 

 shown in colors upon the map, each color representing a distinct type 

 described in the following pages. Sojl profiles indicating the char- 

 acter of the soil to a depth of 6 feet are given on the margin of the 

 map. The presence of gravel in the soil in such quantities as to 

 influence its texture and agricultural value is shown b} 7 symbol. 



The soils of this area fall naturally into two more or less widely 

 separated divisions, viz, colluvial soils and alluvial soils. In the extreme 

 and pronounced types the distinction is evident; with the less pro- 

 nounced types the soils of the two divisions grade together by imper- 

 ceptible degrees, and the classification is of a somewhat arbitrary 

 character. 



The colluvial soils make up the original foot slopes of the mountains, 

 and consist of mountain waste deposited in gently sloping plains by 

 intermittent floods from cloud-bursts falling upon the mountain sides. 

 The soils of the system of secondary fans previous^ described are 

 also included in this class. Under, the soils classed as alluvial fall 

 those formed by river sediment brought for considerable distances in 

 suspension and deposited by floods along the river flood plain. 



The colluvial soils are the Maricopa gravelly loam, Maricopa sand, 

 and Maricopa sandy loam. The alluvial types are Riverwash, Pecos 

 sand, Gila fine sandy loam, and Maricopa silt loam. The following 

 table gives the extent of each of these types: 



A reas of different soils. 



