2010-01-27_REVISION - C1981008 (2)

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United States Department of Agriculture Sincerely,. ,6.,NRCS Natural Resources Conservation service usda gov Jim Boyd, Resource Conservationist jim.boyd?co. 1 jim.bo 970-327-4245-OFFICE P. 0. 29 Norwood, C CBoxO 81423 N ?C S 1- ? b, vet 97"27-4247-1=AX N March 3, 2008 Mike Morgan \,v < Join n PO Box 346 ??4 Nucla, CO 81424 1 N , Z?? ?-n? ???•'r' n ; S b v? 1AS Dear M ke Morgan: SS V? aS C L?,n ? )s o `{fro Q I reviewed your calculatio ii?rt a amount of alfalfa acreage that can be irrigated with 1.5 cubic feet per second (efs). I made some changes to your numbers to account for a 1 hour per day "down time" to move the sideroll sprinklers. Also, I used a sprinkler efficiency of 70% (losses that occur due to wind drift, evaporation, runo fG deep percolation, etc.) to adjust gallons needed to apply one quarter inch of water per acre. With these changes I get a maximum of 96 acres irrigated; But this is assuming absolutely perfect distribution and full efficient use of the available water across the landscape. Also, it assumes that the sprinklers are running nonstop, with no "days ofd" and return exactly on-time to meet the crop's evapo-transpiration demands, which in the case of Alfalfa, growing mid-July in Nucla, on your soils is a 16-day turn around time. This is hardly practical using sideroll sprinkler systems. Let's assume instead that we irrigate 13 days out of every 15 days to supply the water needed by the crop every 15 days. On the 1 e day we start over again. This allows two days off from irrigation every 15 days, for such things as sprinkler repairs or pump servicing, or to just "go fishing." This means that you will only be irrigating about 86.7% of the time (13 divided by 15 is 86.7%). If we multiply 96 acres by 86.7% we get about 83 acres irrigated. Time off from irrigating is a management factor that must be considered. There are some other practical sideroll sprinkler design considerations that must be applied to this example. First, an impact sprinkler is designed to distribute a certain gallons per minute (gpm) within a circular pattern, under supplied operating pressure. A common sprinkler nozzle combination used on siderolls applies about 7 gpm, within a radius of 45 feet, under 40 pounds per square inch (psi) pressure. Because of the circular pattern of water distribution, and a common radius of 45 feet, sprinkler nozzles are normally spaced 40 feet apart along the sideroll sprinkler so that there is overlap of water distribution between adjacent nozzles. This overlap insures that there are not dry spots in the field. Likewise the spacing between sprinkler "sets" is commonly 60 feet, so that the outside of the circles between adjacent sets also overlap. eta -s C(I The Coeservatlon Service works in partnership with t Fe American Poo* a sustain natural resources lancis. An Eq.) 04nity t end-Employer.