Irrigation System Performance Audit

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Irrigation System Performance Audit
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Class Objectives

• be able to perform field audits on irrigation
  systems
• be able to identify problems that cause poor
  uniformity

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Key Irrigation Auditor Actions

• Identify equipment problems
• Determine actual system performance based on
  uniformity tests
• Adjust run times for seasonal variations

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Water savings achieved by

• Checking and fixing equipment
• Following the weather throughout the season
• Maintaining the system at peak efficiency

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ConceptsandProblems
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Water Application and Uniformity
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System Problem Nozzle too low!
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Sprinkler arc incorrectly set!
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System Problem Missing nozzles!
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Watch out for low-pressure discharge.
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System Problem Pressure too high!
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Runoff caused by excess run time!
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Infiltration Rate in./h

• Rate at which water moves into soil
• Sandy soils accept water rapidly
• Heavy soils accept water slowly
• Decreases during irrigation

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Infiltration vs. Precipitation
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Precipitation Rate (in./h)

• How fast does system apply water?
• Varies from station to station
• Even varies within a station
• Many systems precipitation rates exceed the
  infiltration rate

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Theoretical Precipitation Rate (in./h)

• Q flow rate into area (gpm)
• A area (sq. feet)

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Matched Precipitation Rate(MPR)

• Nozzle flow rate is in proportion to the area
  covered
• Watering time is in proportion to the area
  covered
• You must verify during the site inspection
• Can drastically alter the uniformity

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Matched Precipitation
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To the field!
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Site Inspection

• Step one get the system
• working right

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Equipment used in audit
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Site Inspection Priorities(what to repair)

• Minor, not major repairs
• Low heads
• Plugged heads
• Tilted heads
• No matched precipitation rate
• Mixed unmatched heads

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Information to Collect in the Site Inspection

• Site conditions
• Point of connection data
• Controller data
• Brand of products used
• Pressure at nozzles

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Pitot tube for measuring pressure
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Using Pitot Tube
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Checking pressure at nozzle
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Different nozzles and brands will require
different setups!
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Sill Cock Adaptor
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Catch Devices

• Calculate falling water from sprinklers
• Used to determine precipitation rate uniformity
• All catch devices must be identical
• May measure in millimeters or inches
• Volume measurement with a wide throat area allows
  for shorter test times

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Homemade Catch Can
Homemade Catch Can
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Commercial Catch Can
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Bureau of ReclamationCatch Can
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Laying out catch cans
Head locations
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Using tape to locate heads and catch cans
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Catch Device Placement-Rectangular
Sidewalks
Sprinkler Head Catch Can (in station)
Catch Can between stations
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Catch Device Placement - Triangular
Station 1
Station 2
Station 3
1/2
2/3
Sprinkler Head Catch Can (in station)
Catch Can between stations
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Testing area with irregular boundaries
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Testing grass strip
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Setting up catch cans near hardscape
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Problem!Spray hitting side of catch can.
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Recessed Container
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Catch Device Placement
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Collect other data duringstation runs.

• Spacing of sprinklers
• head to head
• line-to-line
• Test soil type and root zone depth

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Spacing Measurement
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Running the Test
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Run test during typical wind conditions!
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Maintain wind below 5 mph.
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Collecting Data
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Collecting Data
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Analyzing Data
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Calculating Precipitation Rate (Net Precip.)

• PR Precipitation Rate (in./h)
• CV avg Average Catch Can Volume (ml)
• 3.66 conversion constant
• TR Testing Runtime (minutes)
• CDA Catch Can Throat Area (sq in.)

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Precip. Rate Sample Calculation
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Precipitation Rate
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DULQ

• One way of measuring system uniformity
• Average of the lowest 25 of catchments divided
  by the average total catchments

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Distribution Uniformity(D.U.)()
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Lower Quarter Distribution Uniformity (DULQ)
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DistributionUniformity
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CU and SC

• Other Methods of Calculating Uniformity
• Coefficient of uniformity
• Scheduling coefficient

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Scheduling Coefficient
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SchedulingCoefficient
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Run Time
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Key Irrigation Auditor Actions

• Identify equipment problems
• Determine actual system performance based on
  uniformity tests

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Site Report

• Letter format for management review
• Formal document/ report (see example)
• Document hardware changes to consider

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Recap Key Actions

• Identify equipment problems
• Repair problems
• Determine actual system performance based on
  uniformity tests
• Make recommendations for improvement

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The End