22 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1903. 



causes trouble by rapidly silting up the canals, making frequent clean- 

 ing necessary. This may be partly prevented by giving the canals 

 considerable fall. 



During recent years, owing to the development of extensive mining 

 interests in the Clifton copper district, tailings from the leachers have 

 been carried into the waters of the Gila through the San Francisco 

 River. This is causing great alarm among the residents of the Gila 

 Valley. It is claimed that pumpkins, chili, tomatoes, and nearly all 

 vines and many vegetables once yielding heavily can no longer be 

 grown. That there is some truth in this seems evident from the fact 

 that such plants thrive until brought in contact with the sediments of 

 the irrigating water, especially if such irrigation be excessive. The 

 quantity of this material, consisting mostly of finely pulverized rock, 

 is sufficient to impart a light gray ish or milky color to the water. These 

 conditions are most evident in the upper part of the valley, in the vicin- 

 ity of Solomonsville and Safford. In order to determine the cause of 

 the trouble samples of the water were collected from the Montezuma 

 and the San Jose canals, above Solomonsville, on March 23, 1903. 



At the laboratories in Washington, where these samples were sent 

 for analysis, the most delicate chemical tests failed to reveal the pres- 

 ence of any injurious substances in the waters. Upon the examina- 

 tion of the sediment collected from these waters, small but unmis- 

 takable traces of copper were detected. Analyses of samples of sedi- 

 ment thrown out from the bottom of an irrigation lateral had also 

 proved the presence of small amounts of copper in the river sedi- 

 ments. The amount of the substance occurring in the sediment was 

 in all cases very small, and not sufficient for a quantitative determina- 

 tion. Copper in a soluble form is, however, very poisonous to plant 

 life, even in very small quantities. That relatively large amounts of 

 the sediment, when deposited about the roots of growing plants, 

 should contain enough copper to prove injurious to crops would not 

 be impossible. 



The question of storage reservoirs is important and interesting. It 

 is possible that sites available for this purpose may exist in the valley 

 narrows above the head of irrigation. Could such a system be 

 installed, large areas of the mesa land would be brought under 

 cultivation. 



UNDERGROUND AND SEEPAGE WATER. 



In a few wells of the area, h T ing along the lower valley levels and 

 adjacent to the main stream channels, water is encountered at a depth 

 of less than 10 feet. Such cases are, however, comparatively rare. 

 Along the higher levels and outer valley margins the water table is 

 found at a depth of from 50 to 75 feet or more. The average depth 

 of wells extending only to the first water-bearing stratum is probably 

 from 20 to 30 feet. 



