OCR Text |
Show cropland. Balancing these factors, it appears that the 25.4 million irrigable acres will con- tribute about the same productivity as an equiva- lent acreage of average cropland. The rate of development of these lands will be contingent upon many factors, and the estimates of the Bureau of Reclamation should be con- sidered as approaching the upper ultimate limit rather than being attainable within the foresee- able future. Based on present authorizations, programing, and past experience, it appears pos- sible to bring 6 million acres of new irrigated cropland into full production by 1975. This would be equivalent to 9 million acres of average nonirrigated cropland. In addition to this acreage, supplemental water may be furnished to some land now provided with irrigation facilities, and there may be some further increase in pump irrigation. Likewise, water may be conserved and production increased on existing projects by more efficient use of water through (1) rehabilitation of the facilities, such as lining the canals and thereby saving water, (2) avoiding overuse of water and thereby not only increasing yields on the land concerned but saving water for use elsewhere, and (3) sav- ing or salvaging water that is lost or transpired through noneconomic plants, such as salt cedars and other types of vegetation, and by treatment of sewage. Although firm estimates pertaining to such potential savings are not available, sig- nificant amounts of water can be conserved fre- quently at relatively low cost. As an illustration, it has been estimated that 40,000 acre-feet of water can be conserved in the Mojave River Basin in California by eradication of cottonwood trees. Much more irrigable land exists than can be irrigated with available water supplies. Water will always be the limiting factor in irrigation. Although irrigation constitutes a water use of paramount importance, a balance must be found with the competing uses for domestic and indus- trial consumption, power development, fish and wildlife conservation, recreation, navigation, and related purposes. The importance of irrigation as a claimant for scarce water has grown even larger than it originally was because of its role in multiple-purpose projects and in regional de- velopment. In serving these purposes it also contributes to the national economy and security. Flood protection, drainage, or a combination of the two, with necessary land clearing, offers substantial possibilities for increasing future agri- cultural production. This increase may be brought about by protection of existing farm lands from floods and by rehabilitation and im- provement of existing drainage works; or by reclamation and development of entirely new lands. In each case it is necessary to express this potential in terms of a new cropland equiva- lent so as to compare it with production increases which may be obtained by other methods. In addition, the probable rate of development is important in terms of the growing needs for agri- cultural commodities. The total land suitable for agricultural use which appears feasible and economical for recla- mation by flood protection, drainage, and clear- ing is about 75 million acres. This total is equiv- alent to about 43 million acres of new cropland of average yields. The various ways by which the land can be reclaimed are shown in table 9. Careful study of past and current rates of de- velopment and proposed programs of Federal agencies for the next few years indicates that probably 21 million acres of average cropland equivalent may be brought into production through flood control, drainage, and clearing by 1975. Increased Yield Required This analysis indicates that, with the soil con- servation program of the Department of Agri- culture taking care of the increased requirements resulting from improvement in the American diet, the Nation faces the need for about 100 million new acres or their equivalent in agricul- tural production by 1975 to provide for the in- crease in population. The analysis shows further that reclamation can be counted upon to provide the equivalent of about 30 million of these new acres if present programs go forward at about their presently projected pace. This will be the 161 |