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Show STATE ENGINEER, COLORADO 46 For the United States-'Stephen B. Davis, Washington, D. C. For Nebraska-R. H. Willis, Bridgeport, Nebraska. For Wyoming-S. G. Hopkins, Cheyenne, Wyoming. For Colorado-Delph E. Carpenter, Greeley, Colorado. •Chairman. During 1924, hearings on the North Platte River were held in the three states, and active negotiations are now under way. For over fifteen years irrigation development above Pathfinder Reservoir in Colorado and Wyoming has been embargoed by the Department of the Interior because of the fear that some day there might be insufficient water for the extensive North Platte Project in Eastern Wyoming and Western Nebraska. This fear has been proven fallacious by careful engineering studies of the past six years. The early behavior of the North Platte River (when water demands of large areas were suddenly imposed upon the river in Western Nebraska shocking it), is largely responsible for this belief, and is similar to irrigation history on the South Platte, Rio Grande, and other western rivers where irrigation is extensively practiced. "Hecuigate diversion'* per acre per year was the old "yard stick" applied to water supply of the North Platte River during the period of rapid irrigation growth. At that time headgate diversions were practically a total loss to the river, because the canal losses and deep percolation from irrigation in the fields went to fill the underground soil reservoir. The soil reservoir in the North Platte Valley under the Interstate, Tri-State and other large canals has now become filled, and the canal and lateral losses and deep percolation from the irrigated fields (which, amount to 50 per cent or more of the headgate diversions), return to the North Platte River as invisible return-flow and drainage recovery, approximately $750,000 having been expended on drain ditches in this area. The 1924 measured return-flow of the North Platte River between the Wyoming Line and Bridgeport, Nebraska, totaled 550,-000 acre-feet. "Consumptive Use" per acre per year (the difference between headgate diversions and return-flow) is the new basis used to measure and study the water supply of the North Platte River Basin and other river systems. The determination of consumptive use is a progressive science. It is interesting to note that successive studies on consumptive use show decreasing values with improvement in methods of ascertainment. The more accurate the study and the older the irrigated area, the less the consumptive use. During 1918 and 1919 a joint engineering field and office study of the entire North Platte River Basin from North Park, Colorado, to Kearney, Nebraska, was made by the United States Reclamation Service and the State of Wyoming. Harold Conkling and R. I. Meeker were the engineers, respectively, for the U. S. R. S. and the State of Wyoming. A voluminous report was the outcome of this engineering investigation. This report, known as |