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18 After the crop consumptive use has been determined it is then neces- sary to determine the allowable or reasonable amount unavoidable farm irri- gation losses or the efficiency wi th which the water can be, appl ied to supply the consumptive use of the crops. The irrigation efficiency is that percent of the water used for irrigation that is held or stored within the root zone and utilized by the crops. There are many factors that influence the irrigation efficiency, some of which are soil type and texture; soil structure or co'ndition; depth of soil over gravel or hardpiln; type of crop; timeliness of irrigation; topography of land surface; method of irrigation; cost, availability, and ability of farm labor; knowledge and ability of the farm operator; and at present a maj'or factor is the amount of surplus water available to use. Where these factors have an adverse influence on irri- gation efficiency, the efficiency may be as low as 30 percent. Wnere these conditions are all favorable, an irrigation efficiency of better than 70 percent might be expected. In the Farm Water ULilization SLudy made by the Bureau of Reclamation an estimated irrigation efficiency of 60 percent was as'sumed. Thus, 40 per- cent of the surface water available at the farm headg<lte ;lnd/or pumped was assumed to be lost for crop production. An assumed average of 60 percent irrigation efficiency for the com- bined 17 canals appears to be reasonable; however, because of different soil conditions, kind of crops produc"d, and methods of irrigation for e-Jch canal, it is not reasonable to expect the irrigation efficiency to be identi- cal for each canal. A rough determination of the percent of four broad types of soil under 14 of the canals was made from soil surveys for the Brighton, Longmont and Greeley areas published by the Bureau of Chemistry and Soils, U. S. Depart- ment of Agriculture. Table 6 shows a summary of this analysis. '. Table 6. Approximate Distribution of Soil Textures under Water District 2 Canal Systems Clay and Fine Sandy Sandy Gravelly Sandy Loam Canal Name Silt Loam ~Qi!m L00!l and Loamy Sand (Percent of Total I<:rea) Ful ton 50 12 25 13 Brantner 80 1 5 10 Brigbton 85 10 5 Lupton Bottom 40 20 5 35 Platteville 25 5 70 Meadow Island No. 1 40 10 10 40 Evans No. 2 5 10 20 65 Meadow Island No. 2 85 10 5 0 Farmers Independent 25 0 5 70 Western Mutual 10 0 5 85 Unio'n 25 25 25 25 Lower Latbam 0 20 20 60 Patterson 50 0 0 50 Highland (Plumb) 0 100 0 0