1 IRRIGATION EFFICIENCY MODIFICATIONS MERLIN N. NELSON NRCS

2 Introduction n Basic system efficiencies n Effects on Sprinklers by Pressure, Terrain, and Wind n Planning considerations n Documentation tools and resources

3 System Types

4 LEPA - Bubbler mode 8”-18” above soil, or drag socks

5 Efficiency Overview n NATIONAL IRRIGATION GUIDE n (Table 6-4) –Periodic move lateral 60-75% –Traveling sprinkler (big guns) 55-65% –Center pivot - standard 75-85% –Linear (lateral) move 80-87% –LEPA Center pivot or linear 90-95

6 Elevation changes in the field

7 Topic One --- Pressure At Sprinkler Heads n Elevation changes within a field –2.3 feet of elev. change = 1 psi n System operation pressures –STD. 442 allows a max. 20% pressure change for sprinklers in a lateral. (i.e. 23 feet or 10 psi friction loss max. for a 50 psi system)

8 Pressure effects pattern breakup

9 Typical Application Rates

10 Sprinkler pressure measurement

11 Topic Two --- Wind n Evaluations

12 NEH Section 15, Chapter 11 Table ,10,11,12 n 40ft. x 60 ft. spacing psi pressure n 0.25 iph 0.30 iph 0.35 iph n 11/64 nozzle 3/16 nozzle 13/64 nozzle n Wind uniformity coefficient (CU) n n n n

13 3 Dimensional Patterns

14 Pattern graphic

15 Summary n Table 11-7 shows CU effects on 1.0 inch gross application. n Example: A CU of 74 % requires 1.0 inch divided by 0.66 or 1.52 inch gross to irrigate 85% of the area adequately. n A 75% efficient sprinkler that applies a gross of 4 in. to get a net of 3 in., would need to apply a gross of 6.04 in. for a 3 in. net w/ 20 mph winds. Efficiency = 49.7%

16 Where to get more information n Other training sessions - IWM II, III n National and Montana Irrigation Guides n National Engineering Handbook, Section 15, Chapter 11 n ASAE, other sources n Request feedback of training session