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Section 4 <br />Agricultural Conservation Measures <br />Table 4-1 Estimated Efficiencies and Costs for Irriaation Methods <br /> <br />T e of Irri ation Range of <br />Efficienc Average Capital <br />Cost/Acre Average Annual <br />Cost/Acre <br />Flood 30-50% - - <br />Furrow 40-60% $37 $30 <br />Gated Pipe ~60% $178 $51 <br />Center Pivot Circle ~85% $433 $64 <br />Center Pivot with Corner ~85% $568 $80 <br />Subsurface Dri Irri ation ~90% $1,000 $120 <br />Reducing Consumptive Use <br />Upgrading irrigation systeins in most ulstances increases water use efficiency but <br />does not necessarily reduce consunlptive use. A concept that has been discussed can <br />be termed coriserved CU water. T11is is water that results from the reduction in <br />productive ET, which can occur when one or more of the following occurs: <br /> <br />1. Irrigated acres are decreased. <br />2. Crop selection is changed from a suninler crop <br />to a cool season crop. <br />3. Crop selection is changed to one wifll a shorter <br />growing season. <br />4. Deficit irrigation is practiced, applying sonle <br />amount less than full ET over the growing season. <br />5. Evaporative losses fronl the field surface are <br />reduced as a result of conservation tillage, <br />nlulchulg, and or drip irrigation. <br />If irrigated acres are decreased, it is relatively <br />sinlple to calculate the water conserved from <br />reduced ET. This type of conserved water has been <br />recogilized in water court transfers of ab icultural <br />water rights and is usually acconlplished through <br />the requirenlent of recordulg a dry-up covenant on <br />the land t11at will no longer be irrigated. In this case, <br />the amount of water t11at is available for other uses <br />is the total consunlptive use of the irrigation water <br />that can be shown to be reduced. <br />Most of the difference in consumptive use between crops can be explained by season <br />of active growth and length of growing season. Crops grown durulg the cool season <br />such as winter wheat are subject to lower atnlospheric demand and thus lower ET <br />rates. Reducing t11e lenb h of crop growing days also can reduce irrigation demands. <br />These differences in season-long consumptive use as a result of growulg day length or <br />growing period can be seen in Table 4-2 below. <br />DRAFT 4-2 <br />