Labo tory No. Gila River below Florence. 3248 3394 3595 3596 3597 3598 3599 3600 3601 3602 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4180 4181 4187 4188 4189 4190 4352 4701 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 Sacaton. W. H. Cody. Sacaton. C. H. Cook, Government well Stotonic Village, 7 miles NW. of Sacaton. Mas akimurl (born the river). Lower Schomick (water village), 13 miles below. Sacaton, Hugh Patten's well. J. D. Stannard, sec. 24, 1 S., 5 E. J. D. Stannard, Sacaton Reservation, No. 9. J. D. Stannard, Gila Indian Reservation, well No. 1. J. D. Stannard, Gila Indian well No. 2. J. D. Stannard, Gila Indian ditch water No. 2. J. D. Stannard, Gila Indian well No. 4. J. D. Stannard, Gila Indian ditch water well No. 4. J. D. Stannard, Gila Indian well No. 5. J. D. Stannard, Gila Indian ditch water No. 5. J. D. Stannard, Gila Indian ditch water No. 6. [Inclosure No. 5, with letter of Prof. R. H. Forbes, July 29, 1913. Extract from pages 698, 699, and 700 Twenty-third Annual Report, University of Arizona, Agricultural Experiment Station.] OBSERVATIONS OF THE CLOSE PROXIMITY OF BLACK ALKALINE AND CALCIUM SULPHATE WATERS. Black alkali is of common occurrence in waters received at this laboratory; and frequently the chemists are obliged to report such waters unfavorably, although otherwise they would serve very well for irrigating purposes. Thus, each acre-foot of an irrigation water carrying 10 parts of black alkali per 100,000 will add 272 pounds of sodium carbonate to the soil on which it is used. It is also known that most crops do not thrive on soil containing more than 0.10 per cent (equivalent to 4,000 pounds in the first acre-foot) of this form of alkali. Since sodium carbonate is difficult to leach out of the soil, and since the conditions under which these waters are used often preclude the application of large amounts for leaching purposes, it may easily happen that most of the black alkali would remain concentrated in the upper stratum of soil. Under these conditions, and assuming that the land was originally neutral, we find that the limit of tolerance would be reached in a very short time, depending chiefly upon the depth of water applied to the land each year. Thus, in average practice serious injury might occur easily before the end of 10 years. If, however, calcium sulphate or gypsum is applied to the land or mixed with the water, a reaction will occur in which the injurious sodium carbonate, by combining with the gypsum, will be changed to the much less injurious sodium sulphate and inert calcium carbonate. The tolerance of crops for sodium sulphate is not only five times as great as for black alkali, but sodium sulphate clings much less tenaciously to the soil, and therefore may be leached out much more easily. Occasionally waters of opposite character capable of reacting in this way are met in successive water-bearing strata in the same well, but during the past year several very interesting instances of calcium sulphate waters occurring in close proximity to black alkaline waters have come to our notice. The composition of several of these is stated in the following table: Composition of closely associated calcium sulphate and black alkaline waters. The first three analyses in this table are of waters encountered by Director Forbes in examining the source of supply for a small irrigation project at Bear Springs, about 6 miles above Fairview in Graham County. A simple calculation shows that water 4793 from the east well in the project carries 231 pounds of sodium carbonate in an acre-foot, and that if 3 acre-feet were used annually, in 10 years 6,941 pounds, or 0.17 per cent of black alkali for the first acre-foot of soil would be added to the land. Similarly, water 4794 from the middle well would add 5,172 pounds, or 0.13 per cent, of black alkali for the first acre-foot. Water 4795 from the west well, however, is rich in calcium sulphate, the natural antidote for black alkali, amounting to 416 pounds in the acre-foot and capable of neutralizing water 4793 when mixed in the ratio 1 to 1.8, and of neutralizing water 4794 in the ratio 1 to 2.4. An interesting feature in this case is that while the water from the west well (4795) is available to correct the alkalinity of the other two, of itself it would prove rather unsatisfactory, due to its large salt content. The two black alkaline waters on the other hand are unusually low in harmful salts other than sodium carbonate. Consequently, the neutral water resulting from mixing 4795 and 4793 in the ratio 1 to 1.8 will contain 59.7 parts per 100,000 of dissolved solids, and that from mixing 4795 with 4794 in the ratio 1 to 2.4 will contain 67.7 parts, in either case producing very satisfactory irrigating waters. Waters 4801 and 4802 are from wells about 600 feet apart in the Santa Cruz Valley near Tucson. The amount of black alkali in the one is not large enough to interfere seriously with its use. These waters illustrate the possibility of finding adjacent sources of entirely different composition. The fairly high percentage of dissolved solids in these two waters, which ordinarily would raise some question as to their effect after long continued use, represent an unusually large amount of harmless calcium bicarbonate, and the remaining dissolved material is mostly sodium sulphate, the least harmful form of white alkali. Waters 4986 and 4987 are from opposite sides of the Santa Cruz underflow at the San Xavier Indian Agency. Both these waters are excellent, in that the solids are mostly calcium bicarbonate, and their salt content very low; but the black alkali in 4986 would eventually prove disastrous if used alone. If, however, the two waters are blended in the ratio 1 of 4986 to 2 of 1987, a neutral water of satisfactory composition will result. The remaining water (5003) is from a bayou of the Colorado River, and is interesting from the fact that it is black alkaline, whereas the Colorado normally contains calcium sulphate. The water is stated to be flowing and probably originates largely in seepage. In reclaiming a large tract of irrigable land it will be necessary to use this water part of the season; but fortunately only during that part when minimum irrigation is required. At other periods the Colorado flows through this channel, and abundance of calcium sulphate water of otherwise suitable character will be available with which not only the black alkali of the previous irrigations can be neutralized but the accumulated white alkali washed out. |