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Show basin are certain to expand beyond those supplied by present construction as the growth of the region progresses. For instance, eventual water demands for irrigation purposes in one area may extend far beyond present local supplies, and influence devel- opments in a neighboring tributary. An example is shown in the Lucky Peak Project in southern Idaho. Lucky Peak Dam, on the Boise River about 9 miles above Boise, is largely a flood control project. Fu- ture expansion of irrigation, however, in the north- ern part of the Mountain Home Project (on the Snake River outside of the Boise River drainage area) can make Lucky Peak useful as a diversion dam for water brought from the Payette River. Provision therefore has been made in project design for that possibility. More engineering projects are involved in river development than those directly associated with the river. Other facilities compete for the use of land needed for reservoir sites. For example, inun- dation of extensive trackage of the present Great Northern and Northern Pacific railways from Spo- kane, Wash., to Columbia Falls, Mont., and Spo- kane to Missoula, Mont., would follow the develop- ment of dams and reservoirs on the Pend Oreille- Glark Fork, and Kootenai Rivers. The presently recommended plans contemplate construction of dams at the Katka, Libby, Paradise, Cabinet Gorge, Trout Creek, Noxon Rapids, and Albeni Falls sites. The cost of railroad relocation adjacent to the res- ervoir (see figure 3) constitutes a substantial portion of the total cost at several important sites studied on both rivers. On some projects this amounts to as much as half of the total amount. The eventual expense of relocating a large amount of trackage for all projects would seem to require considera- tion of the possibilities of consolidating the railroad trackage affected in one double track trunk line in such a way as to leave the valleys available for water resources development. Such a major engi- neering development, as shown in figure 3, would have additional merit in the positive benefits to communication provided by shortening and im- proving of right-of-way provided between Spokane and all points eastward. These benefits would amount to a time saving of as much as 3 to 4 hours over the distance from Missoula to Spokane, made possible by elimination of curvature and reduction in grade. At the same time areas now served locally to some extent by these lines through the valleys of the Clark Fork and Kootenai Rivers might not be materially affected by relocation of the railroads elsewhere, since it is probable that those localities might be served adequately by trucking. A full study of the economics involved, includ- ing the positive benefits of railroad relocation, might increase the demonstrable benefit-cost ratio of these water resources developments. The timing of such railroad relocation, however, at the appropriate stage of the development of reservoir sites for water storage, would have a bear- ing on the cost of the total development program. The longer relocation can be delayed, the less will be the interest charged against the investment re- quired for relocation. The possibility of total relocation of the rail lines affected by the several projects indicates the prob- able inadvisability of considering railroad relocation costs on a project-by-project or piecemeal basis. Consideration on a program basis can logically be given before relocation of railways for the first im- portant reservoir site to be placed in use. Other examples of the recognized need for con- sidering all future water needs in the design of major works are the recommendations which have been made for initial and ultimate installations of power at major dam and reservoir projects. For the long-range future it is proposed that only mini- mum provisions be made for ultimate power, but these should be sufficient to insure that such instal- lations will not be foreclosed. The possible needs for additional industrial water supplies and municipal supply for growing interior populations also should be taken into account in planning. Conclusions The design of major works in the plan for the development of the water resources of a river should have regard for all present and probable future water needs. The extent to which provision for relocation of conflicting facilities on reservoir sites should be made as well as the extent to which provision should be made in initial construction of a project for water uses not now needed, but shown by investi- gation probably to be needed later, depend upon the economics of providing for future uses. Obviously, neither the planning nor design ele- ments of a project or program should hinder future developments. The decision as to how far to go in planning for future use depends upon careful 61 |