LETTER FROM THE COMMISSIONER OF AGRICULTURE, TRANSMITTING, In response to Senate resolution of August 4, 1886, a report on irrigation. DECEMBER 17, 1886.-Referred to the Committee on Agriculture and Forestry, and ordered to be printed. LETTER OF TRANSMITTAL. UNITED STATES DEPARTMENT OF AGRICULTURE, COMMISSIONER'S OFFICE, Washington, D. C., December 15, 1886. SIR: I have the honor to transmit herewith, in accordance with a resolution of the Senate of August 4, 1886, certain information on the subject of irrigation which has been gathered and prepared for publication by this Department. Very respectfully, your obedient servant, Hon. JOHN SHERMAN, NORMAN J. COLMAN, President pro tempore of the United States Senate. 3 IRRIGATION IN THE UNITED STATES-ITS EXTENT AND METH- By RICHARD J. HINTON. THE ARID REGION. The inquiry into the progress and present condition of irrigation in this country has necessarily involved a consideration of the extent and character of the area within which the annual rainfall is not sufficient for the industrial uses of the people. Such an inquiry, broadly defined, has involved 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. Incidentally, the questions arising from deforesting, on the one hand, and of extensive arboriculture, on the other, are related to the inquiry, and have been brought out to some extent. The effort has been to obtain, by means of personal letters and by circulars, addressed to irrigators, arboriculturists, engineers, land owners, colonists, and all other persons known to be actively interested, 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 well-considered 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 de. veloped 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 surface, 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 accurately the Coast Range of California would be the line. The northern boundary 5 |