IRRIGATION IN THE UNITED STATES.

[Prepared by order of the United States Senate Special Committee on Irrigation and Reclamation of Arid Lands. ]

PART I.

THE ARID REGION.

An inquiry into the progress and present condition of irrigation in 'this country necessarily involves a consideration of the extent and character of the area within which the annual rain-fall is not sufficient for the industrial uses of the people. Such an inquiry, broadly defined, involves the extent of the fall of rains or snow within the area indicated; also the evidence obtained as to increase or decrease of precipitation resulting from agricultural settlement or of pastoral occupation, the increase of humidity of earth or air, the destruction of the timber mainly by its use for settlement purposes, the effect of the destruction of the native grasses and the substitution of cultivated varieties; also the sources of water supply, their character, uses, conservation, the means, natural and artificial, employed for their distribution, and what has been and is being accomplished in the way of artificial methods of water distribution and economy, and the laws and customs pertaining thereto. More than a of these, however, it relates itself fundamentally to the largest quess of physical geography. The topographical configuration involve indeed it controls, the whole matter of aridity, because it determines all climatic considerations. The probability of reclama. tion by means of irrigation is primarily by the configuration of a given hydrographic area.

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Incidentally, the questions arising from deforesting, on the one hand, and of arboriculture, on the other, are related to the inquiry, and have been brought out to some extent. The aim has been to give the actual facts upon these subjects, so far as they could be supplied from observation, experience, experiments, and realized results. This effort has been measurably successful. It has brought together a mass of facts and observations that shed much light on the questions involved, giving a broader idea of the importance of irrigation, and adding greater value to a very large area of the United States, of whose agricultural capabilities but small account has heretofore been taken. It will be developed by the facts herein presented that the area of the irreclaimable arid lands within the boundaries of the Union is, comparatively speaking, quite moderate in its extent. There is, however, a very large area, embracing at least one third of our total land service, wherein the water supply, whether subterranean and surface-flow or in the form of precipitation, is both inadequate and irregular in character.

The eastern boundary of this great area may at present be assumed to be the one hundredth meridian of west longitude. The western boundary may be in part placed at the Pacific Ocean, though more ac

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curately the Coast Range of California would be the line. The northern boundary is the British territorial line west from the one hundredth degree to the summit of the Sierras, or the one hundred and twentieth meridian. Following the summits of the main range, the north west line would deflect to the central portion of Oregon, following the southwesterly bend of the mountains down to the northern boundary of California. The southern limit of this dry area would be the northern line of Mexico, and thence south by east, along the Valley of the Rio Grande, down to the ulf of Mexico. The area then, east and west, through its central and larger portion, runs from the one hundredth meridian to the one hundred and twenty-fourth degree of west longitude, and in its47 greatest prolongation north and south from the forty-third to the twenty-seventh deg of latitude. In its more northern portion it runs east and west from the ninety-eighth to the one hundred and twentieth degree of west longitude. The larger portion from north to south is embraced between the thirty-second and forty-third degrees of latitude, with the sub-arid or semi-humid area, the eastern line of which, though irregular, may safely be stated as the ninety-seventh meridian, the total area extends east and west for nearly twenty-eight degrees of longitude.

These lines cover nearly one-half of the States of Kansas and Nebraska, both States of Dakota, the whole of the States of Colorado, Montana, and Nevada, with nine-tenths of California, one-third of Texas, and about one-third of Oregon; also the Territories of Wyoming, New Mexico, Utah; Idaho, and Arizona, with at ast one-third (east of the mountains) of Washington. This embraces about one-third of our whole territorial surface, inclusive of Alaska. How much of the latter-named Territory may be wholly or partially arid or desert in character can not yet be estimated. The east and west lines of this dry region, then, are, in the widest section, over 1,300 miles apart, and in its greatest length, the northern and southern limits are about 1,000 miles apart. If the whole region were compactly arranged it would make a babout 1,000 miles square. The area thus indicated may be subdiv three broad divisions, as follows:

again into

(1) The plains region, running north and south from the British American line to the lower portion of the Rio Grande Valley in Texas, and east and west from the one hundredth to the one hundred and fifth degrees of west longitude. This division may be broadly declared to have a general rise and altitude of from 1,500 to 5,000 feet, though it will fall below that at either end of the area. It is but sparcely sup plied with streams, which are mainly fed from mountain sources; the annual precipitation is nearly everywhere below a reliable amount for economic uses. In the central portion this precipitation will not, under favorable conditions, exceed 18 inches per annum in the eastern part, and as we go westward it diminishes to 12 and 15 inches per annum.

In the southern (Texas) portion of this area the rain-fall will somewhat exceed 20 inches on the east, decreasing until, on the northwest, it will reach only 8 to 10 inches in the most favorable seasons. In the northern or Dakota portion the average is more evenly maintained. This division will include the western half of Kansas and Nebraska, one-third (or the eastern foot-hills and plains region) of Colorado, the major portion of Dakota, the eastern half of Wyoming Territory, and one third or more of the Indian Territory and Texas, with about onefourth (or the eastern part) of New Mexico. It is drained by a number of streams, some of them of importance, and is bounded on the east and north by the Missouri River and its afluents, and by the Pecos and

THE CHIEF DIVISIONS OF THE ARID REGIONS.

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Cimarron Rivers on the west and southwest. Its soil is almost uniformly fertile. Natural grasses of most nutritious quality are found throughout its area. It is the most important grazing section of the West.

Large farming settlements are moving steadily and compactly westward from the eastern line. At various points in its western portion there are important farming communities, created mainly by the use of water as applied through irrigation ditches and by other means of storage and distribution. The valley of the Upper Rio Grande, from the San Juan Range in southern Colorado, to where the river debouches from New Mexico into Texas and becomes the boundary-line between the United States and Mexico, has for many generations been the seat of local and unsystematized irrigation works. The Pueblo or town-dwelling Indians have for centuries practiced it. Since the Spanish conquest, in the sixteenth century, the mixed Mexican people who have inhabited this district have always been obliged to irrigate in order to cultivate. In these latter days our own more enterprising people are inaugurating and carrying on larger enterprises and projjects, whose advantages are already perceivable.

(2) The second great division can be more distinctly characterized as the arid section of the United States. It lies between the one hundred and fifth and the one hundred and twentieth meridians, taking in the whole of our intra-mountain region, from the foot-hills of the Rockies to the lower slopes and foot-hills of the Sierras Nevada in California, and extending north and south from British America to Mexico. Within this area, except on the higher and arid heights of the ranges, principal or secondary, there is generally good pasturage for cattle. The natural grasses are sun-cured, and afford ample food and range for many million head of cattle.

The problem of water supply is, however, one for serious consideration. There are desert tracts and areas within this great region which are undoubtedly arid and desolate to the extent of irreclaimability. Their extent is a matter yet unsettled, especially in view of the great enterprises projected and in progress in both Colorado and California. Even the mountain plateaus, which, from altitude as well as aridity would seem to be undoubtedly sterile, may yet be found useful, not only in providing for cattle, but, possibly under systematic plans of forestculture, they may be made the means of protecting the water sources and otherwise favorably modifying climatic and terrene conditions. The defined outlines of this second division embrace the great basin ction, of which Utah and its water reservoir-the great Salt Lakethe dominating physical and geological features; the Colorado teau region, which occupies the larger portion of Southern Nevada and Northern Arizona; the beautiful parks of the Rocky Mountains or the eastern flank and ranges of the North American Cordillera system; the table-lands of southern Arizona, and the great valleys and basin formed on the north by the Columbia River and its important affluents in eastern Oregon, Idaho, and Montana.

Arid and desas this stupendous mountain system may seem to be, it will be for on examination to have large sections capable of agricultural uses d also to hold within its borders such sources and supplies of water s, properly conserved, protected, and distributed, under the wise a conservative direction of the national and State Governments, will be found of ample utility for the purposes (1) of larger pastoral uses; (2) of more limited and localized, but still extensive, agricultural purposes; and (3) as storage and reservoir sources, from

which at no distant day the life-giving waters may be conveyed to and distributed over vast areas, which even our present limited experiences prove to be convertible into fertile farms.

A glance at a good topographical map will indicate to the observant eye the areas under reference. For example, the central section of the Rockies (in Colorado, Wyoming, and a portion of New Mexico) contain the sources of important rivers. This hydrological area is extensive, as there are numerous lakes, some of considerable size, while the snow precipitation is also quite heavy.

Inquiry and examination will satisfy the inquirer that in the extreme west the higher Sierras yield from the snow precipitation alone an amount of water which, under proper engineering conservation and wise plans of distribution, carried out for the common weal rather than for corporate profit, would supply the whole great valley and foot-hills region of central and southern California, now being so largely developed as a wheat and fruit growing region. The eastern slopes of the Sierras belong as drainage area to the huge hydrographic basin of which Nevada is the chief portion. The snows and storage of that region should readily reclaim 3,000,000 acres in western Nevada.

In the northern portion of our intra-mountain area the hydrological system, comprising the Columbia and Snake Rivers and their affluents, will certainly give a sufficient water supply both for pasturage and agriculture.

East of the Cascade Mountains the climate and natural features of the country are very different from those of the great basin lying west of them, so that the popular divisions, eastern and western Oregon and Washington, are fully warranted. In the eastern section the thermometer is much higher in summer and lower in winter than in the western section. The rain-fall is not half as heavy. From June to September there is no rain. The winters are short, but occasionally severe. Snow seldom falls before Christmas, and, though it sometimes lies from four to six weeks, it usually disappears in a few days. The so-called "Chinook," a warm wind, blows periodically, and melts deep snows in the course of a few hours.

In Eastern Oregon and Washington spring begins in February, and lasts until the middle of May. At this season rain falls in sufficient quantity to give life to vegetation and insure good crops. The average temperature is 520. The rain-fall of the year does not average more than 20 inches. South of the Snake River it is not more than 15 inches, increasing gradually to the northward.

In the southern portion of this area, where the Colorado plateau descends to the valleys of the Gila, Colorado, and Rio Grande, formin the table-lands of Southern Arizona and New Mexico, there has alread been utilized a water supply sufficient for cattle, and in several extendeu portions, as in the valleys of the Gila, Rio Verde, Salt, Colorado, Chiquita, San Pedro, and Santa Cruz Rivers, almost enough to meet the present agricultural and horticultural demands has been turned to account.

It may be estimated, then, that, of our whole intra-mountain region below the timber line as herein outlined, at least 60 per cent. affords fair pasturage, with sufficient watering-places, thou often at long intervals apart, and subject to various limitations, when are rapidly being in a degree overcome, and will hereafter largely (isappear as more attention and skill are directed to the subject. The facts gathered from Utah and Nevada will show how large are the possibilities of improvement in this direction. No really accurate estimate can be made as to