IRRIGATION EFFICIENCY MODIFICATIONS

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IRRIGATION EFFICIENCY MODIFICATIONS

• MERLIN N. NELSON

NRCS
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Introduction

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

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System Types
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LEPA - Bubbler mode 8-18 above soil, or drag
socks
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Efficiency Overview

• NATIONAL IRRIGATION GUIDE
• (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

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Elevation changes in the field
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Topic One --- Pressure At Sprinkler
Heads

• Elevation changes within a field
• 2.3 feet of elev. change 1 psi
• 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)

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Pressure effects pattern breakup
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Typical Application Rates
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Sprinkler pressure measurement
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Topic Two --- Wind

• Evaluations

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NEH Section 15, Chapter 11 Table 11 - 9,10,11,12

• 40ft. x 60 ft. spacing --- 50 psi pressure
• 0.25 iph 0.30 iph
  0.35 iph
• 11/64 nozzle 3/16 nozzle
  13/64 nozzle
• Wind uniformity coefficient (CU)
• 0-4 85 85 84
• 4-10 81 83 84
• 10-15 74 78 81
• 15-20 70 73 74

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3 Dimensional Patterns
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Pattern graphic
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Summary

• Table 11-7 shows CU effects on 1.0 inch gross
  application.
• 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.
• 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

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Where to get more information

• Other training sessions - IWM II, III
• National and Montana Irrigation Guides
• National Engineering Handbook, Section 15,
  Chapter 11
• ASAE, other sources
• Request feedback of training session