Rio Grande was made possible only by a treaty with Mexico, and the St. Mary-Milk River canal was built following the successful negotiation of a treaty with Great Britain on behalf of the Canadian interests.

Reference has already been made, in the preceding chapter, to the attempt made, in the first selection of projects, to give preference to those consisting mainly of public lands and of the reasons for its abandonment.

The conclusion having been reached by the Reclamation Service that a given area offered a possible location for a reclamation project, recommendation was made to the Secretary of the Interior that the public lands in that area be withdrawn from entry under the public land laws.

Up to the time that the lands are actually withdrawn the work must necessarily be somewhat confidential in character in order to prevent enterprising individuals from seizing upon pieces of land which might be needed in the development of the system. Many a desirable irrigation project has been blocked or heavily burdened by speculators obtaining possession of land necessary for the prosecution of work. When, however, the lands have been withdrawn and there is no longer necessity for secrecy, the plans may be disclosed and submitted to searching scrutiny.

Withdrawal of Lands. The withdrawal of the public lands in the irrigable area from entry is effected through the General Land Office. The lands withdrawn are designated as having been withdrawn under either the "first form" or the "second form." Lands withdrawn under the "first form" are withdrawn absolutely, on the ground of their being required for the irrigation works and subsidiary structures. Those withdrawn under the "second form" are so withdrawn because they are, to quote the act, "believed to be susceptible of irrigation from said works." They are withdrawn only from all forms of entry other than that provided by the homestead laws, as modified by the Reclamation Act.

Withdrawal, whether under the first or second form, af

fects only tracts, the ownership or control of which has not already passed out of the hands of the officers of the General Land Office. Claims already initiated are not affected. In the case of relinquishment or abandonment of any of these rights, however, the withdrawal automatically takes effect.

When it is definitely established by the engineers of the Reclamation Service that any of the lands withdrawn will not be required for construction, operation or maintenance, or that they cannot be irrigated under the project, such lands are restored to public entry.

Preliminary survey of the lands withdrawn is next made. In this examination careful attention is given not merely to the topographic and hydrographic features of the area, but to the climatic conditions (especially the temperature and rainfall, frosts, and the character of the soil), to the factors affecting transportation, and to vested rights in and claims to lands and the use of waters.

The detailed data regarding available water supply are obtained almost wholly from the United States Geological Survey, one of the functions of that service being, as already stated, that of investigating the water resources of the United States, including the measurement of stream flow. The facts gathered by it are used by the Reclamation Service in determining whether the water within a drainage area was sufficient for the successful cultivation of the lands to be included within an irrigation project.

Formation of Water Users' Associations. In the initial selection of projects, the examination of the situation existing with respect to the ownership of the irrigable area revealed, in many cases, the necessity of obtaining for the government a mortgage upon the lands in private ownership as security for the repayment of the construction charges. This was accomplished, as explained in the preceding chapter, by the formation of water users' associations.

Although the form of agreement adopted by the twentytwo water users' associations in different parts of the country

varied in accordance with local needs, in virtually every case each person joining such organizations agreed

(1) to turn over to the management of the association all water which he had heretofore appropriated, to be administered in connection with the additional water supply furnished from the government irrigation system;

(2) to make his former water rights, as well as the government water rights, appurtenant to the land irrigated;

(3) to pay the construction charges which might be imposed by the Secretary of the Interior pursuant to the Reclamation Act;

(4) that such charges should be a lien on the land, which the association might enforce;

(5) to dispose of the lands he owned in excess of 160 acres, that being the maximum area under single ownership to which water might be supplied under the Reclamation Act. In some cases 80 acres was set as the maximum.

The form of organization which has hitherto been adopted for water users' organizations is that of a corporation, each member holding stock therein in proportion to the acreage of irrigable land owned by him.

Authorization of Project. Upon the completion of the preliminary survey and, where necessary, of negotiations with the water users' association, recommendation was made, where warranted, to the Secretary of the Interior that the project. be declared practicable. Of the seventy-nine irrigable areas. which were examined by the Service during the years 19021907, only twenty-five were recommended to the Secretary as then practicable for irrigation. The remainder have been designated "secondary projects" and some of them will doubtless form the basis for future operations of the Service, should the initiation of new projects be decided on by Congress.

Upon approval by the Secretary of the recommendation of a project as practicable, authorization was issued to the Director of the Service to proceed with the preparation of the plans. and with the construction of so much of the works as seemed warranted by the condition of the reclamation fund.

Of the twenty-six primary projects constructed by the Service, all but one were authorized during the administration of President Roosevelt, and the Secretary of the Interior in every case conferred with him prior to issuing authorization.

Designing the Project Works. The Service has not, for several years past, been called upon to design any new projects, but it has been necessary from time to time to design new units or extensions of existing projects. The preparation of plans and specifications may, therefore, be regarded as one of the current activities of the Service.

Selection of Reservoir Sites. On the typical project, the selection of a reservoir site is commonly the controlling feature of the design and to it attention must first be given. Within each upland or mountainous area from which water might be had there are commonly a number of possible reservoir sites. The preliminary reconnaissance usually reveals these, but not even the most experienced engineer can readily decide which is preferable. The relative value of the several alternatives presented can be determined only by obtaining data concerning the capacity of the reservoirs and their location with reference to the available supply. For example, the best reservoir site may be so high in the mountains that it cannot receive sufficient water, while a smaller and more expensive site may be found lower down but so limited in capacity as not to hold all of the available supply. A large reservoir may have an expensive dam site or a basin of small capacity may possess an excellent dam site. There are almost innumerable conditions which must be taken into account, and to give proper weight to each of these it is necessary that there be made surveys of sufficient detail to show the capacity of the various sites, the ability to fill them, and the character of the dam sites and other necessary adjuncts.

After a general study of various possibilities has been finished, selection is made of the one or two reservoir sites

which appear to be most favorable. It is then necessary to make more detailed examinations to verify the assumptions made, and to ascertain with great exactness not only the contents of the reservoir for various heights of water but, more than this, the exact size and shape of the site upon which it is proposed to build a dam. There is usually quite a range of practicable locations as, for example, the dam may be placed a few hundred yards higher up stream with possibly greater length or lower down on a better foundation, the larger cubical contents of the dam in one locality balancing certain advantages of depth to foundation or material available at another spot.

The detailed surveys at the various proposed dam sites are usually made on a scale of 100 feet to the inch, more or less, and with contour interval of from two to five feet, dependent upon the steepness of the sides. Explorations of the underground conditions are also made either by open pits or shafts, or by deep holes put down with a diamond drill which recovers the core, or by some of the ordinary forms of well drill. A study of the records of these drillings furnishes facts usually sufficient to reveal the relative advantages and disadvantages of the alternative locations and enables a selection to be made from among them.

Preparation of Detailed Topographic and Land Map. Before laying out the distributing system, it is necessary that there be available a detailed map, not only of the topography but of the boundaries of the several tracts of public and private land within the irrigable area, as well as of township, quarter-section, and meander lines.

A topographic map is prepared of the grounds about the headworks of each important main canal and is continued in a narrow belt along the line of the proposed canal and out to the irrigable lands. This drawing is made in sufficient detail to permit the "paper location" of the works by study in the local office; in other words, instead of the actual survey and location on the ground of each of the several alter