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

By A. H. Thompson.

That portion of Utah drained by the Colorado River and its tributaries belongs to a great basin limited on the north by the Uinta Mountains and on the west by the high plateaus that separate the drainage of the Colorado from that of the salt lakes of the interior, and extending beyond the limits of the Territory on the east and south. The floor of this basin is extremely rough, being broken by isolated groups of rugged mountains, by plateaus encircled with cliffs of almost vertical rock, by mesas and amphitheaters, and huge monumental and castellated buttes. Everywhere the surface is cut and carved with a network of cañons, hundreds and often thousands of feet in depth.

The main channel through which its drainage passes to the sea is the Colorado, and its proper upper continuation, the Green River.

The principal tributaries to these streams from the east are the White, the Grand, and the San Juan Rivers—all rising in the high mountains east of the Territory and flowing in a general westerly course—the White entering the Green River, the Grand uniting with the Green to form the Colorado, and the San Juan entering the latter about 125 miles below the junction of the Grand and the Green. The Virgin, the Kanab, the Paria, the Escalante, the Fremont, the San Rafael, the Price, the Minnie Maud, the Uinta, and Ashley Fork are the principal tributaries from the west.

This portion of Utah is but sparsely settled by white people, the only permanent locations being in the southwestern part, and in the Uinta Valley at the north. Information concerning its agricultural resources is limited, being confined, except in relation to the localities before mentioned, to data collected by the geographical and geological parties of this survey. Many of the streams have been visited but a single time, and different streams at widely different dates, during a field season. Often the exigencies of the survey prevented as close an examination into the flow of water, and the location and character of the soil of the arable tracts, as was desirable; yet, on the whole, it is thought that the data collected can be relied upon as a very close approximation.

The climate of the basin is one of extreme aridity. The prevailing wind is westerly. The high plateaus and mountains forming the western rim of the basin force these winds up to an altitude above the sea of over 10,000 feet, and thus act as great condensers to deprive them of their moisture. Flowing down from the higher lands into the warmer regions below, their capacity for absorption is increased, and during the greater portion of the year the winds abstract from rather than add to the humidity of the lower altitudes. But little is known concerning the actual amount of precipitation of moisture within the basin. Below an altitude of 7,000 feet it is very small, probably not over an average of 5 inches yearly. At higher altitudes it is much greater, probably reaching 24 inches, but this is mostly during the winter months and in the form of snow.

The elevation of the region under consideration is from 2,500 feet to 11,500 feet above the sea, thus giving great range in temperature. In the valleys of the extreme southwestern portion an almost subtropical warmth is experienced, and the different valleys containing arable lands we pass from these by insensible gradations to those where frosts occur during every month in the year. Generally, the limit of successful cultivation of the soil is below 7,000 feet.

In this portion of Utah irrigation is essential to agriculture. If all the single acres it is possible to cultivate without artificial irrigation were aggregated, I do not believe the sum would reach one-fourth of one square mile, and every foot of this meager amount is irrigated naturally. Springs are of infrequent occurrence. The great source of the water supply is the streams fed by the rains and snows of the high table lands and mountains. All these streams have a rapid fall in their upper courses, and are here often of considerable size; but upon reaching the lower and more level country their waters are rapidly absorbed by the porous soil and evaporated by the higher temperature. So great is the loss from these causes that some streams fail to reach the main drainage channel during the warmer months, and all are greatly shrunken in volume. All the arable lands—or lands where altitude, slope of surface, and quality of soil permit successful cultivation, if a supply of water can be obtained, and from which lands to irrigate, or irrigable lands, may be selected—are in the valleys adjacent to the streams. Usually this area in many valleys is in excess of that which the water in the streams can irrigate, and choice in the location of lands to cultivate is often practicable. In this report I have considered irrigable lands to be such only as possess all the necessary qualifications of altitude, slope of surface, and fertility of soil, and have, in addition, an available supply of one cubic foot of water per second for each hundred acres. The great dissimilarity between the valleys makes it desirable to consider the drainage basin of each separately, in respect to arable lands, irrigable lands, volume of water, and practicability of increasing this supply during the irrigating season.

THE VIRGIN RIVER.

This stream is in the extreme southwest corner of the area under consideration. Its branches rise in the Colob Plateau, at altitudes varying from 8,000 to 10,000 feet above the sea. It flows in a southwesterly course, and joins the Colorado beyond the boundaries of Utah. The smaller creeks draining the eastern portion of the plateau unite, after descending to an altitude of 5,500 feet above the sea, and form what is called the Pa-ru-nu-weap Fork of the Virgin. At and below the junction of these creeks, the cañon valley in which they flow widens into what is known as Long Valley. There a considerable area of available land is found. The soil is excellent, and wherever cultivated yields abundant crops. Below Long Valley the stream enters Pa-ru-nu-weap Cañon, and is simply a series of cascades for 15 miles, descending in this distance from 5,000 to 3,500 feet above the sea level. Emerging, it enters the valley of the Virgin. This valley is 44 miles in length. Its upper portion is only an enlargement of the cañon, in which small areas of available land are found. Its lower portion is a broader valley, much broken by low, basalt covered mesas, and sharp ridges of tilted sedimentary rocks. In the upper portion of the valley the river receives several accessions, the principal ones being Little Zion, North Fork, La Verkin, and Ash Creeks. With the exception of the Ash, but very little cultivable land is found along these creeks. Midway in the valley two streams enter, coming from the Pine Valley Mountains and having small areas of irrigable land along their courses, and near the foot the Santa Clara River adds its water. The united streams leave the valley by a deep cañon cut through the Beaver Dam Mountains. The valley of the Virgin has a lower altitude than any other portion of Utah, and a warmer climate. The soil of the arable lands is usually good, and wherever it is possible to irrigate produces abundant crops. Some little difficulty is occasionally experienced in the first years of cultivation from an excess of alkaline constituents in the soil, but plentiful applications of water soon remove this difficulty, and these lands often become the most productive. No reliable data concerning the amount of arable land in the drainage basin, or the volume of water carried by the Virgin River and its tributaries, have been collected. From the best information attainable, the amount of land actually irrigated in 1875, is placed at eleven square miles. This conclusion is based in the main upon returns made in 1875 to the Deseret Agricultural and Manufacturing Society, the amount under cultivation in Long Valley having been ascertained by Mr. J. H. Renshawe, of this survey. To irrigate this, all the water in most of the tributary streams is used, but a large surplus remains in the main river. The amount of arable land is far in excess of the water supply, but some considerable expense for dams and canals would be necessary to utilize the whole amount.