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<br />. <br /> <br />. <br /> <br />8 <br /> <br />'lbe unit values used to determine seeDage amounts were 9.66 ac. ft. per <br /> <br /> <br />mile for group ditches and 0.130 ac. ft. per irri~ted acre for on farm ditches. <br /> <br /> <br />'lbese values appear to be conservative and less than used in the SCS Gunnison <br /> <br />and Grand Valley reports. No actual field tests were made in the MeElmo unit <br /> <br /> <br />to determine the unit values used. <br /> <br />A review of the SCS basic data indicates that the on farm ditch seepage <br /> <br /> <br />only reflects that which is estimated to occur from the head ditches. Present <br /> <br /> <br />surface irrigation systems are often quite primitive and tailwater ditches, as <br /> <br /> <br />such, often do not exist. 'lbe water often just moves on as best it can or <br /> <br /> <br />collects in a low area. However, seepage is bound to occur from this increment <br /> <br />and a value of 50% of the headwater ditch seepage has been included in the <br /> <br /> <br />"KRK water budget". This should be conservative. It is noted that a 2/3 <br /> <br /> <br />figure was used in the Grand Valley report and a 1/2 figure used in the Lower <br /> <br /> <br />Gunnison report. <br /> <br />'lbe seepage rates for the "future without" condition were increased by <br /> <br /> <br />13% by SCS since they assumed this would be the average increase in diversion. <br /> <br /> <br />'lbe USBR report shows an increase in diversion of 9.7% which would increase <br /> <br /> <br />their canal seepage estimates by 5.3%. 'lbe "KRK water budget" uses the USSR <br /> <br /> <br />percentages. <br /> <br />Group and onfarm ditch evaooration is not aekowledged in the SCS water <br /> <br /> <br />budget. This is probably not a large figure, but it should be included to <br /> <br /> <br />help trace what is really taking place. For the "KRK water budget", it is <br /> <br />assumed that the group ditch was 2 feet wide and had an evaporation rate of <br /> <br /> <br />2 ac. ft. per ac. per yr. This equals 0.5 ac. ft./mi./yr. For the onfarm <br /> <br /> <br />head ditch, the same evaporation rate was used and an area of 50 sq. ft. per <br /> <br /> <br />ac. was assumed. This gives a unit value of 0.0023 ac. ft./ac./yr. For the <br /> <br /> <br />tailwater ditch, the same unit value was used even though the surface area <br /> <br />may be much larger at some sites and nonexistent at others. For the "future" <br /> <br /> <br />condition, the unit values was increased 10%. <br /> <br />'lbe SCS report does not appear to account for improvements already in <br /> <br />place in its water budget. During the field trip it was indicated to me that <br /> <br /> <br />600 acres of' sprinklers were in place plUS 20 to 30 miles of improved group <br /> <br /> <br />and head ditches (some in pipel. Therefore, in the "KRK water budget" it is <br /> <br />assumed that roughly 20% of' the acreage has sprinklers and improved ditches <br /> <br />in place f'or the "present condition" and 30% will have for the "future without <br /> <br />condi ticn". <br /> <br />001510 <br />