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. CHAPTER II COMPREHENSIVE PLAN Diversion Requirements at Heads of Main Canals Seepage and operational losses from various reaches of the main canals were estimated and added to the monthly irrigation delivery requirements at turnouts from main canals as a means of determining the required monthly irrigation diversion demands at the various sources of supplyo Separate estimates were made for the Savannah Butte, Wonsits, Artesia, and Deadman Bench Canals. Canal seepage losses were estimated with use of a coeffi- cient for sandy loam soil as the canal~which are presently planned almost entirely as unlined structures, would pass through outwash materials throughout most of their lengths with seepage losses being relatively high. Allowances were included in the estimates for losses during the initial priming of the canals at the beginning of the irrigation seasono Canal losses would be greatly reduced if the canals were lined, and the desir- ability of lining will be considered in any future project studieso . The peak monthly irrigation water requirement would occur in Julyo The peak canal capacity requirements were estimated by successive increases in the average July requirement' at the head of the canals of about 6 per- cent to allow for dry periods with no effective precipitation during the month, about 10 percent for ab~ve-average consump~ve use during periods of above-average temperatures, 'and 10 to 20 perc~nt for operational flexi- bility and peaking within the month depending on the t4tal acreage served by a particular canalo Thus the estimated peak capacity requirements are about 30 percent higher than the average requirements for the month of July. Estimates of average monthly irrigation requirements at the head of the various canal areas and of peak canal capacity requirements are sum- marized in the following paragraphs. Savannah Butte Canal area.--The estimated irrigation diversion require- ments at the head of the Savannah Butte Canal on White River for the 2,200 acres that would be served by the canal are summarized in the following table. Average monthly irrigation diversion requirements at head of Savannah Butte Canal (Unit--acre-feet) Month M~ June July August September Totals Per acre 0031 093 1007 .93 045 3.69 Requirement at turnouts from canal Total for 2,200 acres 700 2,100 2,400 2,100 1,000 8,300 Canal seepage and operational losses 600 500 400 400 400 2.300 Average diversion requirement at head of canal 1,300 2,600 2,800 2,500 1,400 10,600 . 34