Where surface waters are not readily available, the subterranean water is of first importance. It is generally known that, underlying the earth's surface at various depths, there is a large quantity of free water. Those living in humid climates often overestimate the amount of water so held in the earth's crust, and it is probably true that those living in arid regions underestimate the quantity of water so found. The fact of the matter seems to be that free water is found everywhere under the earth's surface. Those familiar with the arid West have frequently been surprised by the frequency with which water has been found at comparatively shallow depths in the most desert locations. Various estimates have been made as to the quantity of underlying water. The latest calculation and perhaps the most reliable is that made by Fuller, who, after a careful analysis of the factors involved, concludes that the total free water held in the earth's crust is equivalent to a uniform sheet of water over the entire surface of the earth ninety-six feet in depth. A quantity of water thus held would be equivalent to about one hundredth part of the whole volume of the ocean. Even though the thickness of the water sheet under arid soils is only half this figure there is an amount, if it could be reached, that would make possible the establishment of homesteads over the whole dry-farm territory. One of the main efforts of the day is the determination of the occurrence of the subterranean waters in the dry-farm territory.
Ordinary dug wells frequently reach water at comparatively shallow depths. Over the cultivated Utah deserts water is often found at a depth of twenty-five or thirty feet, though many wells dug to a depth of one hundred and seventy-five and two hundred feet have failed to reach water. It may be remarked in this connection that even where the distance to the water is small, the piped well has been found to be superior to the dug well. Usually, water is obtained in the dry-farm territory by driving pipes to comparatively great depths, ranging from one hundred feet to over one thousand feet. At such depths water is nearly always found. Often the geological conditions are such as to force the water up above the surface as artesian wells, though more often the pressure is simply sufficient to bring the water within easy pumping distance of the surface. In connection with this subject it must be said that many of the subterranean waters of the dry-farm territory are of a saline character. The amount of substances held in solution varies largely, but frequently is far above the limits of safety for the use of man or beast or plants. The dry-farmer who secures a well of this type should, therefore, be careful to have a proper examination made of the constituents of the water before ordinary use is made of it.
Now, as has been said, the utilization of the subterranean waters of the land is one of the living problems of dry-farming. The tracing out of this layer of water is very difficult to accomplish and cannot be done by individuals. It is a work that properly belongs to the state and national government. The state of Utah, which was the pioneer in appropriating money for dry-farm experiments, also led the way in appropriating money for the securing of water for the dry-farms from subterranean sources. The world has been progressing in Utah since 1905, and water has been secured in the most unpromising localities. The most remarkable instance is perhaps the finding of water at a depth of about five hundred and fifty feet in the unusually dry Dog Valley located some fifteen miles west of Nephi.
Pumping water
The use of small quantities of water on the dry-farms carries with it, in most cases, the use of small pumping plants to store and to distribute the water properly. Especially, whenever subterranean sources of water are used and the water pressure is not sufficient to throw the water above the ground, pumping must be resorted to. The pumping of water for agricultural purposes is not at all new. According to Fortier, two hundred thousand acres of land are irrigated with water pumped from driven wells in the state of California alone. Seven hundred and fifty thousand acres are irrigated by pumping in the United States, and Mead states that there are thirteen million acres of land in India which are irrigated by water pumped from subterranean sources. The dry-farmer has a choice among several sources of power for the operation of his pumping plant. In localities where winds are frequent and of sufficient strength windmills furnish cheap and effective power, especially where the lift is not very great. The gasoline engine is in a state of considerable perfection and may be used economically where the price of gasoline is reasonable. Engines using crude oil may be most desirable in the localities where oil wells have been found. As the manufacture of alcohol from the waste products of the farms becomes established, the alcohol-burning engine could become a very important one. Over nearly the whole of the dry-farm territory coal is found in large quantities, and the steam engine fed by coal is an important factor in the pumping of water for irrigation purposes. Further, in the mountainous part of the dry-farm territory water Power is very abundant. Only the smallest fraction of it has as yet been harnessed for the generation of the electric current. As electric generation increases, it should be comparatively easy for the farmer to secure sufficient electric power to run the pump. This has already become an established practice in districts where electric power is available.
During the last few years considerable work has been done to determine the feasibility of raising water for irrigation by pumping. Fortier reports that successful results have been obtained in Colorado, Wyoming, and Montana. He declares that a good type of windmill located in a district where the average wind movement is ten miles per hour can lift enough water twenty feet to irrigate five acres of land. Wherever the water is near the surface this should be easy of accomplishment. Vernon, Lovett, and Scott, who worked under New Mexico conditions, have reported that crops can be produced profitably by the use of water raised to the surface for irrigation. Fleming and Stoneking, who conducted very careful experiments on the subject in New Mexico, found that the cost of raising through one foot a quantity of water corresponding to a depth of one foot over one acre of land varied from a cent and an eighth to nearly twenty-nine cents, with an average of a little more than ten cents. This means that the cost of raising enough water to cover one acre to a depth of one foot through a distance of forty feet would average $4.36. This includes not only the cost of the fuel and supervision of the pump but the actual deterioration of the plant. Smith investigated the same problem under Arizona conditions and found that it cost approximately seventeen cents to raise one acre foot of water to a height of one foot. A very elaborate investigation of this nature was conducted in California by Le Conte and Tait. They studied a large number of pumping plants in actual operation under California conditions, and determined that the total cost of raising one acre foot of water one foot was, for gasoline power, four cents and upward; for electric power, seven to sixteen cents, and for steam, four cents and upward. Mead has reported observations on seventy-two windmills near Garden City, Kansas, which irrigated from one fourth to seven acres each at a cost of seventy-five cents to $6 per acre. All in all, these results justify the belief that water may be raised profitably by pumping for the purpose of irrigating crops. When the very great value of a little water on a dry-farm is considered, the figures here given do not seem at all excessive. It must be remarked again that a reservoir of some sort is practically indispensable in connection with a pumping plant if the irrigation water is to be used in the best way.
The use of small quantities of water in irrigation
Now, it is undoubtedly true that the acre cost of water on dry-farms, where pumping plants or similar devices must be used with expensive reservoirs, is much higher than when water is obtained from gravity canals. It is, therefore, important that the costly water so obtained be used in the most economical manner. This is doubly important in view of the fact that the water supply obtained on dry-farms is always small and insufficient for all that the farmer would like to do. Indeed, the profit in storing and pumping water rests largely upon the economical application of water to crops. This necessitates the statement of one of the first principles of scientific irrigation practices, namely, that the yield of a crop under irrigation is not proportional to the amount of water applied in the form of irrigation water. In other words, the water stored in the soil by the natural precipitation and the water that falls during the spring and summer can either mature a small crop or bring a crop near maturity. A small amount of water added in the form of irrigation water at the right time will usually complete the work and produce a well-matured crop of large yield. Irrigation should only be supplemented to the natural precipitation. As more irrigation water is added, the increase in yield becomes smaller in proportion to the amount of water employed. This is clearly shown by the following table, which is taken from some of the irrigation experiments carried on at the Utah Station:—
Effect of Varying Irrigations on Crop Yields Per Acre
Depth of Water Wheat Corn Alfalfa Potatoes Sugar Beets Applied (Inches) (Bushels) (Bushels) (Pounds) (Bushels) (Tons) 5.0 40 194 25 7.5 41 65 10.0 41 80 213 26 15.0 46 78 253 27 25.0 49 77 10,056 258 35.0 55 9,142 291 26 50 60 84 13,061