APPENDIX J. GILA RIVER BETWEEN IMPOUNDING DAM AND DIVERSION DAM AS AN 1. The following quotation is taken from Water Supply Paper No. 33, pages 66-68: San Carlos Reservoir site is located on Gila River, on the White Mountain Indian Reservation, at the San Carlos Agency, in Gila County, Ariz., at a point where San * * * The Gila River at this point traverses some Carlos River joins the Gila. spurs of the Pinal range of mountains, and for a distance of 31.5 miles below the dam site the river flows in a narrow box canyon. This canyon extends to Dudleyville, which point is the upper end of the Riverside Reservoir site. The river then passes through the Riverside Reservoir site for a distance of 15.5 miles, after which it again enters a canyon, which is the upper end of The Buttes Reservoir site. This latter canyon extends to the dikes, which is 4 miles above The Buttes Dam site. The total length of river from San Carlos Dam site to The Buttes Dam site is approximately 60 miles; about 40 miles of this distance being box canyon, and the remaining portion being valley land, of from 1 to 3 miles in width. (The San Pedro River enters the Gila at Dudleyville.) The water which is released from the San Carlos Reservoir site will pass through approximately 40 miles of box canyon on its way to the irrigable lands where it is to be used. Comparative measurements made at The Buttes and San Carlos during the dry season of the year, when less than 10 second-feet of water was flowing in the river at San Carlos, indicates practically an equal amount of water at San Carlos and The Buttes. There undoubtedly is a substantial loss from evaporation between In the case of these points, but this loss is compensated for by the seepage water which returns from the Riverside Valley and from the valley above The Buttes Dam site. the Riverside Valley a few second-feet of water is used for irrigation, and the return In both valleys, however, the high stages from this irrigation augments the stream. of the river undoubtedly charge the sand bars and gravel beds with water, and these are gradually drained off during the lower stages of the stream and, as has been stated, give practically an equal amount of water at San Carlos and The Buttes (at low stages). The San Pedro and the other drainage lines entering the Gila above The Buttes and below San Carlos will contribute their portion to this stream unregulated by a reservoir built at San Carlos. This water can be used for irrigation around Florence if diverted below. (That is, below The Buttes. The diversion sites are about 12 miles above Florence.) If this volume of water and the return water from seepage is added to the water which is discharged for irrigation from the San Carlos Reservoir site, it is probable that there will be available for irrigation at the point of diversion as much water as would be discharged from the San Carlos Reservoir site. If the Gila River from the San Carlos Dam site to The Buttes Dam site is 60 miles in length and 200 feet in width it will expose to evaporation a water area of 1,454 acres. The depth of evaporation per annum has been previously determined as 91 inches, or 7.58 feet. With an area of 1,454 acres and a depth of evaporation of 7.58 feet, there will be lost from this body of water 11,021 acre-feet. This would be 4.6 per cent of the total capacity of the San Carlos Reservoir site (Lippincott was considering a dam 130 feet high, giving a reservoir capacity of 241,393 acre-feet) and, in order to make per cent of the water discharged from San Carlos an allowance for all possible loss, is assumed as being lost for irrigation below The Buttes. The Riverside Valley and the valley above The Buttes are both largely public domain, and there is no reason why the water from the San Carlos Reservoir should not be used for irrigation purposes at these points, as well as below Florence. This being the case, there will be but a slight disadvantage in storing water at San Carlos. (Water-Supply Paper No. 33, pp. 66-68.) 2. Following the above is a table showing the behavior of the San Carlos Reservoir during an "average" year. In that table a loss in 155 transmission of 5 per cent is allowed for. It would appear to be unnecessary to make this allowance, if as claimed above, the loss from evaporation is "compensated for by the seepage water which returns from the Riverside Valley and from the valley above The Buttes Dam site." 3. Under the head of "Gila River as an Irrigation Conduit," Mr. J. D. Schuyler (S. Doc. 152, 56th Cong., 1st sess.) comments as follows: The possible losses by evaporation and infiltration in the 60 miles of river channel below San Carlos have not been overlooked in this investigation, and the canyon was carefully examined at low water between San Carlos and The Buttes. It was found that the flow of the stream was practically undiminished all the way down, and that while loss from evaporation was considerable it was about balanced by the underflow or seepage coming in from the tributary drainage area between these points. The subject is intelligently discussed in Mr. Lippincott's report and the conclusion is reached that for all practical purposes there are no disadvantages in storing the water supply at San Carlos, 60 miles above The Buttes, and no more loss of water to be anticipated than if the reservoir were located at The Buttes. Also that the flood discharge of the stream below San Carlos will be available for diversion below The Buttes during a portion of the year, and when such diversion is thus made the storage at San Carlos need not be drawn upon, which will increase the duty of the San Carlos Reservoir. These conclusions are fully concurred in by the writer as sound and well based. 4. This board is of the opinion that there is little or no loss in the canyon portions of the stream, except from evaporation. This latter loss may be wholly compensated for by inflow from springs, of which many are reported to exist, and from side drainage. The elevation of the canyon bed from Dudleyville to San Carlos increases from about 1,700 feet to 2,300 feet. Within short distances of the canyons the mountains rise to heights of more than 4,000 feet, and receive an annual rainfall that averages more than 15 inches. 5. Loss from filtration can occur only in the "valley lands," described by Lippincott as about 20 miles in length and from 1 to 2 miles in width. 6. It was pointed out in Water-Supply Paper No. 33 that on the average in the present unregulated condition of the river any losses. sustained from filtration or evaporation between San Carlos and the mouth of the San Pedro are more than made up by the supply contributed by the San Pedro, and that in fact the run-off of the Gila just below the mouth of the San Pedro averages 11 per cent greater than the run-off at San Carlos. Observations taken since Paper No. 33 was published confirm this figure. (See Appendix F.) 7. It was also stated (p. 67) that "Comparative measurements made at The Buttes and San Carlos during the dry season of the year, when less than 10 second-feet of water was flowing in the river at San Carlos, indicate practically an equal amount of water at San Carlos and The Buttes." There are no subsequent observations on record that either confirm or throw doubt on this statement, but it is felt that only by a long series of observations could its truth be established beyond peradventure. But whether or not during the dry season there is a net loss between San Carlos and The Buttes, the fact is that for the average year the quantity of water passing The Buttes is greater than that passing San Carlos. 8. The question is, Will this condition obtain in the case of a regulated flow of the Gila through the impounding dam? Can it be assumed that there may be diverted into the canal 11 per cent more water than is passed through the impounding dam? On the basis of a yearly draft from the reservoir of 200,000 acre-feet, the flow through the dam would vary between 200 and 367 second-feet, depending upon the season of the year. 9. During the period of high water and for some time thereafter, when, even though no water had been wasted over the spillway of the impounding dam, the flow of the San Pedro and of the small tributaries above Dudleyville would probably have filled up the gravels below Dudleyville, it is easy to believe that a given small flow released from the reservoir would reach the diversion dam unreduced or even augmented in quantity. The diversion dam also may bring to the surface a small quantity of underflow. But at the end of a long dry season, when the gravels may be drained and the San Pedro dry, it might be necessary to release from the reservoir a greater quantity of water than is needed at the intake for irrigation. It should not be overlooked also that possibly the flood discharge of the San Pedro may exceed for brief periods the capacity of the main canal and that accordingly a certain quantity of water may go to waste over the diversion dam. But even with these losses, Schuyler's opinion seems sound that with the regulated stream, the gain between the two dams will on the average exceed the loss, and that "the flood discharge of the streams below San Carlos will be available for diversion below The Buttes during a portion of the year, and when such diversion is thus made, storage at San Carlos need not be drawn upon, which will increase the duty of the San Carlos reservoir." 10. Assuming, then, a system of communications between observers on the San Pedro and the dam authorities, the flow through the dam may be reduced or even shut off entirely, depending upon the quantity flowing in the San Pedro. The four available hydrographs of the San Pedro (two of them partial) indicate that floods may be expected in July, August, and September, and this inference is borne out by rainfall records extending over a long period of years. This is also the season of greatest rainfall on the irrigable area near Florence. The practical way to profit by the San Pedro floods would be to shut the gates in the dam during the flood season except when the flood flow of the San Pedro is ехсерtionally low. 11. While, therefore, one would probably be justified in counting upon the San Pedro for some water, it would be impossible from the data at present available to estimate its amount. It will therefore merely be assumed that the water released from the impounding dam sustains no loss. This conservatism seems all the more wise when it is realized that not all of the drainage area of the San Pedro is in the United States and that possibly the flow in Mexico may some day be diverted. C. H. McKINSTRY. APPENDIX K. Lieut. Col. C. H. MCKINSTRY, Board of Army Engineers, Los Angeles, Cal. Being somewhat DEAR SIR: I have yours of July 18 relative to a report upon soils of the Casa Grande Valley and their irrigation with well water and with river water. familiar with this region and having a quantity of material on hand relating to the points you mention, I submit it herewith, in order, if possible, to save time both to you and to me in this connection. In general, the soils of the Casa Grande Valley are exceedingly well graded naturally, entailing minimum expense in leveling for irrigation. They range in physical character from gravelly loams, at higher elevations, to somewhat heavy clays, usually in the valley bottoms. In a general way it may be stated that in physical disposition and character the soils of Casa Grande Valley resemble those of the Salt River Valley. With reference to alkali content, I am inclosing a sheet of analyses, together with accompanying map,2 showing location of a number of the samples tabulated. As is shown on the sheet, nearly all of the soils examined are more or less black alkaline in character, most of the samples representing 1 foot of soil. In a few cases only the salts are shown to contain an excess of calcium sulphate. 1 Accepting a common statement to the effect that 0.1 per cent of black alkali in a soil is likely, in the course of time, to prove injurious to most farm crops, it will be seen that this limit is occasionally exceeded, but that in the majority of cases the amount of black alkali contained is much less than 0.1 of a per cent. Under the influence of irrigation and without precautionary measures, such as thorough cultivation, etc., black alkali and other soluble salts may be concentrated from several feet in depth at or near the surface, thus increasing percentages of black alkali which may originally exist in virgin soils within reach of plant roots. On the other hand, valuable lands threatened with injury by black alkali may be treated with gypsum, which is an antidote for sodium carbonate, or black alkali, in the soil. We have treated such lands at Tucson with gypsum obtained in carload lots at Douglas, Ariz., at an expense of $2.50 a ton laid down at Tucson. The treatment has proven practicable and economic with us under those conditions. Of course the amount of gypsum required varies with the quantity of black alkali in a stated soil. Therefore it may be stated that while small but noteworthy amounts of black alkali generally prevail in the district, they are manageable or can be remedied. If further evidence is needed the crops grown in the valley, some of them on farms of long standing, should complete the proof. With reference to the water supply for the district. This may be classified under three heads: 1. Well waters. 2. Flood waters. 3. (Prospective) Reservoir waters. With reference to well waters, we are submitting two sheets 3 containing analytical figures for samples taken throughout the district. As may be seen, those waters obtained at a distance from the Gila River are usually more or less black alkaline in character. Quite a number will be seen to exceed the limit of 10 parts in 100,000, which we assume to be a noteworthy and sometimes harmful amount of black alkali in an irrigation water. For instance, No. 5130 contains a prohibitive amount of black alkali and No. 3903 is seriously black alkaline. On the other hand, the waters near the Gila River, shown mainly on sheet 2, are for the most part white alkaline in character, containing an excess of calcium sulphate. The waters containing white alkaline salts may be seen to average a larger quantity of total solids than the black alkali waters, although this statement does not hold true in all cases. Assuming that 100 parts of total solids, white alkaline in character, may prove injurious, quite a number of the white alkaline waters may be seen to contain noteworthy quantities of soluble salts considered from an irrigator's point of view; 1 Sheet marked "Inclosure No. 1," following this letter. Map marked "Inclosure No. 2," following this letter. Sheets marked "Inclosure No. 3" and "Inclosure No. 4" follow this letter. 159 |