1. Refine and Adjust the Design Parameters

2. © Irrigation Association Performance of Sprinkler Devices Depends on Soil type and slope Climatic conditions System capacity Cropping and tillage system Irrigation frequency and management

3. © Irrigation Association Calculate an Intelligent Estimate of System Efficiency Decouple efficiency into: – Uniformity and adequacy impacts – Evaporation and leakage losses Predict each component separately Recombine components

4. © Irrigation Association 10 0 2030405060708090100 PERCENT OF FIELD AREA APPLICATION DEPTH STRESS ACTUAL DEPTH APPLIED DESIRED APPLICATION DEEP PERCOLATION RELATIONSHIP OF UNIFORMITY AND EFFICIENCY

5. © Irrigation Association Calculate an Intelligent Estimate of System Efficiency Evaporation losses Wind drift Drop size and nozzle height considerations

6. © Irrigation Association WATER "LOSSES" FROM CENTER PIVOTS DROPLET EVAPORATION CANOPY EVAPORATION RUNOFF DEEP PERCOLATION CROP ROOT ZONE SOIL EVAPORATION DRIFT

7. © Irrigation Association Component Performance EFFICIENCY -- Where does the water go? Evaporation Transpiration Wind Drift Uniformity Runoff

8. © Irrigation Association Let’s Look at Some Overheads of Efficiency Tables

9. © Irrigation Association Controlling Evaporation Losses Many devices are available You can fine tune performance to local conditions

10. © Irrigation Association DROP SIZE DISTRIBUTION - IMPACT SPRINKLER.00.04.08.12.16.20.24 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 5/32'' NOZZLE 43 PSI DROP DIAMETER (inches) RELATIVE FREQUENCY

11. © Irrigation Association.00.04.08.12.16.20.24 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 5/32'' NOZZLE 43 PSI DROP DIAMETER (inches) RELATIVE FREQUENCY 35 30 25 20 15 10 5 0 EVAPORATION RATE (%) DROP SIZE DISTRIBUTION vs. EVAPORATION RATE

12. © Irrigation Association GROOVED PLATES PRODUCE BIGGER DROPS 1.0 0.8 0.6 0.4 0.2 0.0 SMOOTH PLATE MEDIUM GROOVE COARSE GROOVE DROP SIZE (inches) FREQUENCY 0.0.08.16.24.04.12.20

13. © Irrigation Association EFFECT OF PRESSURE ON DROP SIZE.00.04.08.12.16.20.24 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 5/32'' NOZZLE 43 PSI 58 PSI 72 PSI DROP DIAMETER (inches) RELATIVE FREQUENCY

14. © Irrigation Association STARTEDFINISHED IRRIGATION TRANSPIRATION WITH IRRIGATION TRANSPIRATION RATE TIME TRANSPIRATION DECREASES DURING IRRIGATION BUT CANOPY EVAPORATION INCREASES EVAPORATION FROM CROP CANOPY

15. © Irrigation Association EVAPORATIVE LOSSES FOR IMPACT AND SPRAY DEVICES 0.0 0.1 0.2 0.3 0.4 0.5 0.6 SERRATED SPRAY - 1 ft above crop IMPACT SPRINKLER - 14 ft above ground NOT IRRIGATED WATER QUANTITY (in/day)TRANSPIRATIONDROPLETCANOPYSOIL Thompson, et al. (1997) Bushland, TX: 1992, 90F, 15 mph, dry

16. © Irrigation Association Calculate Peak ET for Your System Local irrigation guides (NRCS, State, University) Internet sources Reference ET Crop coefficients

17. © Irrigation Association Calculate Peak ET for Your System, cont. Length of peak period Calculate the average ET over the peak period Peak ET risk assessment (eight of ten years)

18. © Irrigation Association TIME (days) 0 0.1 0.2 0.3 0.4 0.5 DAILY ET (in/day) DAILY ET NET SYSTEM CAPACITY 0.25 in/day 51015200 COMPARING ET RATE TO SUPPLY CAPACITY

19. © Irrigation Association VARIABILITY CAUSES SHORTAGES AND SURPLUSSES 0 0.1 0.2 0.3 0.4 0.5 TIME (days) DAILY ET (in/day) SHORTAGE PERIODS SURPLUS PERIODS AVERAGE ET = 0.275 inches/day NET SYSTEM CAPACITY 0.25 in/day 5101520 0

20. © Irrigation Association -5 -4 -3 -2 0 1 2 3 4 WATER AMOUNT (inches) ET FOR CORN RAIN MAYJUNE JULY AUG SEPT RAIN AND ET FOR 10-DAY PERIODS SOUTH CENTRAL NEBRASKA - 1983 OCT

21. © Irrigation Association -5 -4 -3 -2 0 1 2 3 4 WATER AMOUNT (inches) ET FOR CORN RAIN MAYJUNE JULY AUG SEPT DEFICIT OCCURS WHEN ET > RAIN SOUTH CENTRAL NEBRASKA - 1983 OCT DEFICIT NEEDED FROM SOIL TO MAINTAIN ET

22. © Irrigation Association -5 -4 -3 -2 0 1 2 3 4 WATER AMOUNT (inches) ET FOR CORN RAIN MAYJUNE JULY AUG SEPT 10-DAY SUPPLY DEFICIT FOR A 5OO GPM SUPPLY ON 130 ACRES SOUTH CENTRAL NEBRASKA - 1983 OCT NET SUPPLY CAPACITY: 500 GPM @ 85% EFFICIENCY DEFICIT

23. © Irrigation Association -5 -4 -3 -2 0 1 2 3 4 WATER AMOUNT (inches) ET FOR CORN RAIN MAYJUNE JULY AUG SEPT 10-DAY SUPPLY DEFICIT FOR A 5OO GPM SUPPLY ON 130 ACRES SOUTH CENTRAL NEBRASKA - 1983 OCT DEFICIT NET CAPACITY PERIOD WHEN SUPPLY < DEFICIT

24. © Irrigation Association -5 -4 -3 -2 0 1 2 3 4 WATER AMOUNT (inches) ET FOR CORN RAIN MAYJUNE JULY AUG SEPT SOIL WATER DEPLETION (5OO GPM ON 130 ACRES) SOUTH CENTRAL NEBRASKA - 1983 OCT DEFICIT NET CAPACITY CUMULATIVE DEPLETION

25. © Irrigation Association -5 -4 -3 -2 0 1 2 3 4 WATER AMOUNT (inches) ET FOR CORN RAIN MAYJUNE JULY AUG SEPT CUMULATIVE DEPLETION EXCEEDS ALLOWABLE DEPLETION FOR 500 GPM SOUTH CENTRAL NEBRASKA - 1983 OCT DEFICIT NET CAPACITY CUMULATIVE DEPLETION ALLOWABLE DEPLETION (1.5 inch/ft * 4 feet * 50%)

26. © Irrigation Association CAPACITY REQUIREMENTS FOR NEBRASKA 0123456 3 4 5 6 7 8 9 ALLOWABLE DEPLETION (inches) GROSS SYSTEM CAPACITY (gpm/acre) 85 % APPLIC. EFF. SOUTHWEST NE EAST CENTRAL NE

27. © Irrigation Association DAILY ET RATE (inches/day) 0.2 0.3 0.4 0.5 0.6 0.115102040608090959999.9 PROBABILITY OF SMALLER ET MAXIMUM DAILY DATA 5-DAY AVERAGE DATA PROBABILITY OF DAILY ET vs LENGTH OF PERIOD

28. © Irrigation Association Specify Management Strategy for Undersized Systems Below canopy sprays LEPA irrigation Deeper, less frequent irrigations to reduce evaporation losses

29. © Irrigation Association Calculate the Leaching Requirement Off-season vs. Peak season leaching

30. © Irrigation Association What to do?

31. © Irrigation Association Adjust the ET Estimate to Account for High Frequency Irrigation

32. © Irrigation Association Recap and Review Are there any questions?

33. © Irrigation Association Thank You for Attending!