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<br />C,? <br /> <br />..I'") <br />-1 <br /> <br />,-' <br /> <br />Step 2. Estimate the average volume of seepage. <br /> <br />OnfarDl field ditches -water flows about 4 days in 7 throughout the season. <br /> <br />Average seepage rate <br /> <br />0.09 cis /mlle <br /> <br />Average seepage rate <br /> <br />21 acre-feet/mile/year <br /> <br />Small laterals - water flows the entIre 210 day irrigation season. <br /> <br />Average seepage rate <br /> <br />0.12 cfs/mlle <br /> <br />Average seepage rate <br /> <br />- 49 acre-feet/mile/year <br /> <br />Step 3. Estimate the average salt load reduction with installation of <br /> <br />pipeline and ditch lining. Assume 90 to 100% effectiveness in reduction in <br /> <br />seepage. <br /> <br />OnfarDl field ditches <br /> <br />21 af/mi/yr x 5 tns/af = 100 tns/mi/yr. <br /> <br />Small laterals <br /> <br />49 af/mi/yr x 5 tns/af = 245 tns/mi/yr. <br /> <br />Average seepage and salt load reduction unit values are be,ing recommended and <br /> <br />used in Grand Valley. As more of the nearly 700 miles of onfarm pipeline and <br /> <br />ditch lining and about 200 miles of improved off-far,. late,rals are installed <br /> <br />in Grand Valley, the more accurate will be the estimate of salt load <br /> <br />reduction using average values. <br /> <br />36 <br />