Refine and Adjust the Design Parameters

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

© 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

© Irrigation Association PERCENT OF FIELD AREA APPLICATION DEPTH STRESS ACTUAL DEPTH APPLIED DESIRED APPLICATION DEEP PERCOLATION RELATIONSHIP OF UNIFORMITY AND EFFICIENCY

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

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

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

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

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

© Irrigation Association DROP SIZE DISTRIBUTION - IMPACT SPRINKLER /32'' NOZZLE 43 PSI DROP DIAMETER (inches) RELATIVE FREQUENCY

© Irrigation Association /32'' NOZZLE 43 PSI DROP DIAMETER (inches) RELATIVE FREQUENCY EVAPORATION RATE (%) DROP SIZE DISTRIBUTION vs. EVAPORATION RATE

© Irrigation Association GROOVED PLATES PRODUCE BIGGER DROPS SMOOTH PLATE MEDIUM GROOVE COARSE GROOVE DROP SIZE (inches) FREQUENCY

© Irrigation Association EFFECT OF PRESSURE ON DROP SIZE /32'' NOZZLE 43 PSI 58 PSI 72 PSI DROP DIAMETER (inches) RELATIVE FREQUENCY

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

© Irrigation Association EVAPORATIVE LOSSES FOR IMPACT AND SPRAY DEVICES 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

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

© 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)

© Irrigation Association TIME (days) DAILY ET (in/day) DAILY ET NET SYSTEM CAPACITY 0.25 in/day COMPARING ET RATE TO SUPPLY CAPACITY

© Irrigation Association VARIABILITY CAUSES SHORTAGES AND SURPLUSSES TIME (days) DAILY ET (in/day) SHORTAGE PERIODS SURPLUS PERIODS AVERAGE ET = inches/day NET SYSTEM CAPACITY 0.25 in/day

© Irrigation Association WATER AMOUNT (inches) ET FOR CORN RAIN MAYJUNE JULY AUG SEPT RAIN AND ET FOR 10-DAY PERIODS SOUTH CENTRAL NEBRASKA OCT

© Irrigation Association WATER AMOUNT (inches) ET FOR CORN RAIN MAYJUNE JULY AUG SEPT DEFICIT OCCURS WHEN ET > RAIN SOUTH CENTRAL NEBRASKA OCT DEFICIT NEEDED FROM SOIL TO MAINTAIN ET

© Irrigation Association 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 OCT NET SUPPLY CAPACITY: % EFFICIENCY DEFICIT

© Irrigation Association 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 OCT DEFICIT NET CAPACITY PERIOD WHEN SUPPLY < DEFICIT

© Irrigation Association WATER AMOUNT (inches) ET FOR CORN RAIN MAYJUNE JULY AUG SEPT SOIL WATER DEPLETION (5OO GPM ON 130 ACRES) SOUTH CENTRAL NEBRASKA OCT DEFICIT NET CAPACITY CUMULATIVE DEPLETION

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

© Irrigation Association CAPACITY REQUIREMENTS FOR NEBRASKA ALLOWABLE DEPLETION (inches) GROSS SYSTEM CAPACITY (gpm/acre) 85 % APPLIC. EFF. SOUTHWEST NE EAST CENTRAL NE

© Irrigation Association DAILY ET RATE (inches/day) PROBABILITY OF SMALLER ET MAXIMUM DAILY DATA 5-DAY AVERAGE DATA PROBABILITY OF DAILY ET vs LENGTH OF PERIOD

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

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

© Irrigation Association What to do?

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

© Irrigation Association Recap and Review Are there any questions?

© Irrigation Association Thank You for Attending!