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<br />~ ~ >t, r")~ ~ <br />.:' '" <br /> <br />11 <br /> <br />8. The estimated average annual diversion of water by the 17 canals <br />(direct-flow plus reservoir releases) was 302,100 acre-feet. The amount <br />diverted varied greatly from year to year. Most canals experienced a mini- <br />mum diversion from the South Platte River during 1954 and 1961. Maximum <br />diversions generally occurred during 1947 and 1952. <br /> <br />The estimated average annual canal loss was 84,700 acre-feet or 29 per. <br />cent of the water diverted. Thus, an annual average of 217,400 acre-feet o'f <br />surface water was estimated to be available at the farm headgates. <br /> <br />The estimated average annual amount of water pumped from groundwater <br />sources for land under the 17 canals was estimated to be 148,600 acre- <br />feet. Thus, the estimated total average annual supply of water at the <br />farm headgates was 366,000 acre-feet or 2.94 acre-feet per acre. Ground- <br />water provided about 40.6 percent of the total supply at the farm headgate. <br /> <br />Only a very minor amount of water was used for irrigation during the <br />months of November, December, January, February, and March. The estimated <br />average annual total water supply at the canal river headgates plus reser- <br />voir releases and groundwater pumped was estimated to be 450,400 acre-feet. <br />(Some minor discrepancies will be noted in some of the above totals due to <br />rounding of figures to the nearest 100 acre-feet). <br /> <br />9. The full water supply at the farm headgate was computed by the <br />Bureau of'Reclamation using (1) a combination of the Lowry-Johnson and the <br />Thornthwaite methods to determine the consumptive use of water by crops <br />and (2) an assumption of a 60 percent irrigation efficiency in the appli- <br />cation of water to supply the consumptive use requirements for each of the <br />17 canals.. <br /> <br />The estimated full water requirement at the farm headgate varied from <br />1.59 to 3.19 acre-feet per acre with an average annual headgate water <br />requirement of 2.44 acre-feet per acre or a total of 304,200 acre-feet <br />for the 17 canals. Monthly requirements averaged 0.08 acre-foot per acre <br />for April, 0.14 for May, 0.47 for June, 0.66 for July, 0.60 for August, <br />0.36 for September, and 0.13 for October. <br /> <br />An assumed average of 60 percent irrigation efficiency for the combin~d <br />17 canals appears to be reasonable; however, because of different soil con- <br />ditions, kinds of crops produced and methods of irrigation for each canal, <br />it is not: reasonable to expect the irrigation efficiency would be identical <br />for each canal. <br /> <br />10. The canal headgate requirement includes the full requirement at <br />the farm headgate plus canal losses. The estimated average annual require- <br />ment at the canal headgates was estimated by the Bureau of Reclamation to <br />be 388,900 acre-feet. <br /> <br />11. An estimated annual average surplus of 61,500 acre-feet for the 17 <br />canals was found as the difference between the total headgate supply and the <br />total headgate requirement. However, 4 of the 17 canals experienced an aver- <br />age shortage during the 17 years and also had a shortage SO percent of the <br />IS-year time period. Also, many ditches experienced shortages during critical <br />months, b~t showed an annual surplus because of excessive water use during <br />other months. <br /> <br />i <br /> <br />0_ -JL~~_-. .b ik;;,jd <br />