Laserfiche WebLink
<br />o <br />C\l <br />Q <br />~ On-Farm System: The princioal physical improvements needed are ("I) land <br />o forming or irriqation method change on 56,000 acres, (2) pipillq or lining of <br />field ditches, (3) installation of water control structures to del"iver and <br />measure water, and (4) control of tailwater and reduction of high water <br />tables by application of proper drains on 36,000 acres. ~anagement n8eds <br />in~lude timing and scheduling, :nd efficient water application of preper <br />rates on 68,000 acres. Deep percolation from on-farm aPPlication of irri- <br />gation water is estimated to be 110,000 acre-feet per year and surface return <br />. flow 210,000 acre-feet. This is further estimated to cunent1y account for <br />280,000 tons of salt loading per year. <br /> <br />In order to secure hi gh on~farm i rri gatiOIl effi ci ency and reducti all of deep <br />percolation and surface runoff, the following measures should be carried <br />out: (1) proper irrigation layout and land forming on 42,000 acres of the <br />steeper and rougher land, (2) change to sprinkler, drip or border methods <br />on 14,000 acres, (3) proper layout, consolidation and realignment and lining <br />.01' piping 1,100 miles of permanent field ditches, (4) installation of 8,000 <br />structures for water control and measurement, (5) installation of open drains <br />on 12,000 acres and tile drains on 22,000 acres, (6) use of automation on <br />12,000 acres, and (7) management improvement (irrigation water scheduling) <br />on 68,000 acres. <br /> <br />Return System: The return system which handlps some 500,000 acre-feet pel' <br />year in 88 miles of natural washes has excessive erosion and salt pick up. <br />The 14 washes (15 to 30 feet deep and up to 150 feet wide) which traverse <br />the irrigation area need grade control and bank stabilization as the major <br />treatment, Fifty miles of main drains are needed and as many as possible <br />should beoutletted directly into the Colorado River to reduce salt pick up <br />-from deep washes.. <br /> <br />Impacts and Cost: Major on-farm costs are estimated to be $10 million for <br />lining field ditches, $5.3 million for land forming, $5.7 million for tile <br />drainage, and $2.8 ~illion for changing method of irrigation. On-farm deep <br />percolation would be reduced about 0.8 acre-feet per acre irriga.ted or <br />61,000 acre-feet. On-farm salt loading would be reduced 153,000 tons due <br />to the combined effects of improved on-farm systems and better water manage- <br />ment by the operator. Reduced return flows consistent with overall system <br />and management improvements would reduce the salt loading in the off-farm <br />return system by an estimated 20,000 tons. Improving the lateral system <br />would result in reducing salt loading by 105,000 tons when seepage is reduced <br />42,000 acre-feet. On-farm unit installation costs would be $340 per acre for <br />80,000 acres. Averaqe annual cost based on life expectancY and 6 7/8 percent <br />interest is $30 per acre. Table 6 presents the treatment opportunities, <br />costs and salt reduction impacts in tabular form. <br /> <br />There would also be a favorable impact on maintenance of a stable irrigated <br />agriculture economy involving an increase in crop production and farm income. <br />However, no evaluation has been made of these impacts. <br /> <br />USDA Programs: There are a number of USDA programs which are appl icabl e to <br />lateral, on-farm and return system measures as I.tell as to measures ')n nrivate <br /> <br />- 10 - <br />