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OOQ869 acres, of which 90 per cent is on the East Slope and 5 per cent on the West Slope, as follows: Arable lands in Colorado North Platte Rio Grande West Slope East Slope Per Cent 0,9 3.9 5,4 89,8 N S W E 150,000 Acres 650,000 900,000 15,000,000 State Totals 16,700,000 100.0 In western Colorado the arable land data are based on Reclamation Bureau land classification sur- veys plus information from aerial photographs and field inspections, For their reclamation a large num- ber of relatively small reservoirs are required, Pri- marily such reservoirs are needed to regulate tribu- tary stream flows, and provide irrigation supplies during late summer months. Many of them will also serve new land areas, to be reached by extensions of existing ditches, A number of the major tracts or arable lands will require the construction of long canals, on steep side-hill locations, and SOlJle can be reached only by substantial pump lifts. Because of high costs and the isolated locations, far from rail transportation, of some prospective west slope de- velopments, construction of them may be postponed, Roughly it is estimated that perhaps one-th ird of the surveyed west slope arable lands may come under ir- rigation in the near future, provided, of course, that feasible projects can be devised where wanted, The future picture in eastern Colorado is some- what different. For 20 years or more the irrigated acreage has been declining in eastern Colorado, in part because of low farm prices, but principally be- cause of inadequate water supplies,. Contemplated trans-mountain diversions are intended primarily, to supplement the inadequate local supplies, and hence will be used largely on lands now irrigated under constructed ditches, Some new ditches may be con- structed and some new lands may be irrigated, but in relation to present acreages, the additions will not be large, Contrary to some reports, not more than a few per cent, at most, of the non-irrigated arable lands of eastern Colorado can be reclaimed, and, with that small exception, the great plains of eastern Colorado are destined to remain in part as dry-pas- tures, and to the extent they are cultivated, as dry- farm or non-irrigated lands. A second field of investigation, which our engi- neering department is required to undertake, in addi- tion to water resource determinations, involves the economics of irrigated agriculture, and questions of financial feasibility, Long ago the simple, cheap and easily constructed ditches and reservoirs were built . largely by private initiative and capital. Projects of today and tomorrow are more complicated, more expensive, and more difficult of construction, Ques- tions of feasibility and economic justification are becoming increasingly important. The trans-mountain diversion projects under con- sideration are multiple-purpose projects, Power fea- tures, constructed and operated by the federal gov- ernment, are non-repayable by local water users. Also since flood control has been assumed by the fede~al government as a national problem the costs of such features, if any, are non-repayable. But the water features are 100 per cent repayable, and hence the relations between irrigation costs and benefits require broad and careful consideration, Irrigated agriculture seems to be growing in ex- tent and importance throughout the world. As popu- lations increase it is natural that arid and non- productive lands be developed and occupied, Depart- ment of Commerce data indicate that irrigation has now expanded to a total of 200,000,000 acres, in all the continents of the world. It may surprise some, as it did me, to learn that 70 per cent of the world's irrigated area has been developed on the Asiatic Continent, In continental United States we have about 20,000,000 acres, or 10 per cent of the total in the World, Colorado is one of the arid western States where irrigation is a necessary, and the dominant, form of agricultural operations, Colorado's 3,200,000 acres under irrigation represents about one-sixth of the total in the United States, Except for Galifornia, which is first, Colorado leads all other States in the extent to which irrigation has been developed. Statistics of agriculture in Colorado are difficult to analyze, for the reason that reported totals include both irrigation and dry-farm operations, During the 20-year period 1923-1942, the field crop values aver- aged $15,90 per acre harvested, Our segregations indicate that the field crops harvested from irrigated land averaged $28.74 per acre, and from non-irri- gated land $7.45 per acre. Such returns illustrate the producing power of natural precipitation and the four-fold greater returns when irrigation is em- ployed to aid rainfall, Field crops are harvested from but 75 to 80 per cent of the total irrigated area. Some of the irrigated lands in Colorado are devoted to pasture purposes, from which the crops are not harvested except by grazing livestock, Irrigated acreages as reported are gross figures, including pastures, house, barn and feed lots, road and ditch right of way, etc" whereas harvested acreages as reported are net. Field crops harvested from an average of 2,348,000 acres during 1923-1942 were valued at $67,481,000, This period was characterized by unprecedentedly low farm prices and irrigation supplies. Under nor- mal conditions, perhaps $90,000,000 worth of field crops are harvested from 2,500,000 acres of irri- gated land, or at the rate of $36 per acre. At present, under war-time prices, the irrigated field crops har- vested have values totaling about $125,000,000, or about $50 per acre, Further analyses of the agricultural statistics show that specialty crops occupy 14 per cent of the irrigated acreage harvested, and yield 52 per cent of the total dollar income; and that general farm crops, occupying 86 per cent of the area yield but 48 per cent of the income. Stated another way, the specialty crops, which include sugar beets, potatoes, fruits, and all the vegetable and truck crops yielded at the aver- age rate of $103,78 per acre, while the hay, grain and general farm crops returned $16,01 per acre, These recorded results for the State as a whole require further segregation by stream basins and individual irrigation systems to be directly applicable to each of the development problems under consider- ation, Contemplated supplemental water supplies will irrigate some new lands which now are largely unproductive, but mainly the benefits will consist of: (a) increased yields of general farm crops, the yields of which heretofore have been subnormal in most seasons because of inadequate irrigation supplies: and (b) increased areas devoted to specialty crop production, which areas heretofore have been limited by the inadequacy and uncertainty of available ir- rigation supolies. Crop rotation programs, to better maintain soil fertilitv, can be carried out with more adequate and better controlled irrigation supplies, such as contemplated in connection with the trans- mountain diversion projects under consideration. Total investment in all the irrigation works in use in Colorado as of 1930, was estimated by the