Report on the lands of the arid region of the United States, with a more detailed account of the lands of Utah

by John Wesley Powell; Willis Drummond; Clarence E. Dutton; Grove Karl Gilbert; A. H. Thompson

IRRIGABLE LANDS.

Within the Arid Region only a small portion of the country is irrigable. These irrigable tracts are lowlands lying along the streams. On the mountains and high plateaus forests are found at elevations so great that frequent summer frosts forbid the cultivation of the soil. Here are the natural timber lands of the Arid Region—an upper region set apart by nature for the growth of timber necessary to the mining, manufacturing, and agricultural industries of the country. Between the low irrigable lands and the elevated forest lands there are valleys, mesas, hills, and mountain slopes bearing grasses of greater or less value for pasturage purposes.

Then, in discussing the lands of the Arid Region, three great classes are recognized—the irrigable lands below, the forest lands above, and the pasturage lands between. In order to set forth the characteristics of these lands and the conditions under which they can be most profitably utilized, it is deemed best to discuss first a somewhat limited region in detail as a fair type of the whole. The survey under the direction of the writer has been extended over the greater part of Utah, a small part of Wyoming and Colorado, the northern portion of Arizona, and a small part of Nevada, but it is proposed to take up for this discussion only the area embraced in Utah Territory.

In Utah Territory agriculture is dependent upon irrigation. To this statement there are some small exceptions. In the more elevated regions there are tracts of meadow land from which small crops of hay can be taken: such lands being at higher altitudes need less moisture, and at the same time receive a greater amount of rainfall because of the altitude; but these meadows have been, often are, and in future will be, still more improved by irrigation. Again, on the belt of country lying between Great Salt Lake and the Wasatch Mountains the local rainfall is much greater than the general rainfall of the region. The water evaporated from the lake is carried by the westerly winds to the adjacent mountains on the east and again condensed, and the rainfall thus produced extends somewhat beyond the area occupied by the mountains, so that the foot hills and contiguous bench lands receive a modicum of this special supply. In some seasons this additional supply is enough to water the lands for remunerative agriculture, but the crops grown will usually be very small, and they will be subject to seasons of extreme drought, when all agriculture will result in failure. Most of these lands can be irrigated, and doubtless will be, from a consideration of the facts already stated, namely, that crops will thereby be greatly increased and immunity from drought secured. Perhaps other small tracts, on account of their subsoils, can be profitably cultivated in favorable seasons, but all of these exceptions are small, and the fact remains that agriculture is there dependent upon irrigation. Only a small part of the territory, however, can be redeemed, as high, rugged mountains and elevated plateaus occupy much of its area, and these regions are so elevated that summer frosts forbid their occupation by the farmer. Thus thermic conditions limit agriculture to the lowlands, and here another limit is found in the supply of water. Some of the large streams run in deep gorges so far below the general surface of the country that they cannot be used; for example, the Colorado River runs through the southeastern portion of the Territory and carries a great volume of water, but no portion of it can be utilized within the Territory from the fact that its channel is so much below the adjacent lands. The Bear River, in the northern part of the Territory, runs in a somewhat narrow valley, so that only a portion of its waters can be utilized. Generally the smaller streams can be wholly employed in agriculture, but the lands which might thus be reclaimed are of greater extent than the amount which the streams can serve; hence in all such regions the extent of irrigable land is dependent upon the volume of water carried by the streams.

In order to determine the amount of irrigable land in Utah it was necessary to determine the areas to which the larger streams can be taken by proper engineering skill, and the amount which the smaller streams can serve. In the latter case it was necessary to determine first the amount of land which a given amount or unit of water would supply, and then the volume of water running in the streams; the product of these factors giving the extent of the irrigable lands. A continuous flow of one cubic foot of water per second was taken as the unit, and after careful consideration it was assumed that this unit of water will serve from 80 to 100 acres of land. Usually the computations have been made on the basis of 100 acres. This unit was determined in the most practical way—from the experience of the farmers of Utah who have been practicing agriculture for the past thirty years. Many of the farmers will not admit that so great a tract can be cultivated by this unit. In the early history of irrigation in this country the lands were oversupplied with water, but experience has shown that irrigation is most successful when the least amount of water is used necessary to a vigorous growth of the crops; that is, a greater yield is obtained by avoiding both scanty and excessive watering; but the tendency to overwater the lands is corrected only by extended experience. A great many of the waterways are so rudely constructed that much waste ensues. As irrigating methods are improved this wastage will be avoided; so in assuming that a cubic foot of water will irrigate from 80 to 100 acres of land it is at the same time assumed that only the necessary amount of water will be used, and that the waterways will eventually be so constructed that the waste now almost universal will be prevented.

In determining the volume of water flowing in the streams great accuracy has not been attained. For this purpose it would be necessary to make continuous daily, or even hourly, observations for a series of years on each stream, but by the methods described in the following chapters it will be seen that a fair approximation to a correct amount has been made. For the degree of accuracy reached much is due to the fact that many of the smaller streams are already used to their fullest capacity, and thus experience has solved the problem.

Having determined from the operations of irrigation that one cubic foot per second of water will irrigate from 80 to 100 acres of land when the greatest economy is used, and having determined the volume of water or number of cubic feet per second flowing in the several streams of Utah by the most thorough methods available under the circumstances, it appears that within the territory, excluding a small portion in the southeastern corner where the survey has not yet been completed, the amount of land which it is possible to redeem by this method is about 2,262 square miles, or 1,447,920 acres. Of course this amount does not lie in a continuous body, but is scattered in small tracts along the water courses. For the purpose of exhibiting their situations a map of the territory has been prepared, and will be found accompanying this report, on which the several tracts of irrigable lands have been colored. A glance at this map will show how they are distributed. Excluding that small portion of the territory in the southeast corner not embraced in the map, Utah has an area of 80,000 square miles, of which 2,262 square miles are irrigable. That is, 2.8 per cent. of the lands under consideration can be cultivated by utilizing all the available streams during the irrigating season.

In addition to the streams considered in this statement there are numerous small springs on the mountain sides scattered throughout the territory—springs which do not feed permanent streams; and if their waters were used for irrigation the extent of irrigable land would be slightly increased; to what exact amount cannot be stated, but the difference would be so small as not to materially affect the general statement, and doubtless these springs can be used in another way and to a better purpose, as will hereafter appear.

This statement of the facts relating to the irrigable lands of Utah will serve to give a clearer conception of the extent and condition of the irrigable lands throughout the Arid Region. Such as can be redeemed are scattered along the water courses, and are in general the lowest lands of the several districts to which they belong. In some of the states and territories the percentage of irrigable land is less than in Utah, in others greater, and it is probable that the percentage in the entire region is somewhat greater than in the territory which we have considered.

The Arid Region is somewhat more than four-tenths of the total area of the United States, and as the agricultural interests of so great an area are dependent upon irrigation it will be interesting to consider certain questions relating to the economy and practicability of distributing the waters over the lands to be redeemed.