Example: Design Criteria & System Specification

 Peak crop requirement

 The irrigation system capacity must exceed
 the peak crop water requirement.
 In South Africa SAPWAT software can be
 of assistance.
 www.sapwat.org.za

 Type of System

 Floppy Overhead Cable System

 Sprinkler

 Black Floppy Sprinkler

 Flow rate per Sprinkler

 730 l/h
 Flow regulated within 5 % from 2 to 6 Bar

 Sprinkler Spacing

 12 x 15 meter Triangular

 Important: Laterals spaced 12 m apart
                 Sprinklers spaced 15 m apart

 Sprinkler Height

 3 to 5 meters (Structure high enough for
 tractor, implement & harvester movement)
 * Clearance between crop canopy and
 sprinkler of 2 meters

  See: pole lengths and implement clearance

 Gross Application Rate @
 this spacing             

 4.0 mm/h

 Average Application Efficiency

 89 %

 Net Application Rate @ this spacing

 3.56 mm/h

 Recommended Irrigation time

 3-6 hours – Irrigate 4-5 irrigation cycles of
 4 hours followed by 1 irrigation cycle of 8
 hours**

 SEE: IRRIGATION SCHEDULING

 Recommended Cycle Time

 < 3 days

 Nr of irrigation blocks

 12

 Nr of irrigation blocks per shift

 1

 Nr of shifts per Cycle

 12

 Pump hours per day

 24 hours per day (in peak)
 7   days per week (in peak)

 System capacity

 8.0mm per day (gross)
 7.12mm per day (nett)

 Minimum Pressure at Sprinkler

 2 Bar

 *** Filtration

Filtration is absolutely necessary
for smooth operation of the system.

 800 micron for systems with sprinklers
       running below 4 Bar pressure

 500 micron for systems with sprinklers
       running above 4 Bar pressure