Landscape Irrigation

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Landscape Irrigation

  1. 1. Landscape Irrigation Agricultural Extension Service The University of Tennessee
  2. 2. *Design and Management Factors 1. Water Supply Requirements and Limitations 2. Scale Drawing of the Site 3. Sprinkler/Drip products that Match the Landscape 4. Spacing of Sprinklers 5. Sprinkler Zones 6. Pipe Sizing 7. Irrigation System Equipment 8. Programming an Irrigation Controller
  3. 3. How Much Water is Required?  0.7 inches per week 2.0 gpm/ac in 24hr/da  1.0 inch per week 3.0 gpm/ac in 24hr/da  1.5 inches per week 4.5 gpm/ac in 24hr/da  Irrigate all at one time 80 gpm/ac in 2 hr/day  Allows some flexibility 15 gpm/ac in 7 hr/da
  4. 4. *Surface and Ground Water Sources  Rivers and Lakes may provide a Non Limiting Supply  Creeks and Ponds; however, may Constrain the Landscape Irrigation System to Supply Limitations
  5. 5. *Municipal Water Sources  Utility Water and Well Water usually constrain the flow available to a Landscape Irrigation System
  6. 6. Measuring Flow and Pressure  Example - Measuring the flow and pressure from a residential hydrant  connection to hydrant  tee fitting  pressure gauge  ball valve  5 gallon bucket & stop watch or municipal flow meter
  7. 7. Pressure and Flow Rate 0 20 40 60 80 100 120 0 2 4 6 8 10 12 14 Flowrate (gpm) Pressure(psi) Pressure and Flow Rate are Related (pressure vs. flow rate is different for every system)
  8. 8. *Proper Equipment: Rotating Sprinklers  A single sprinkler can cover a large area, 20 to 60 foot radius  Needs a higher flow rate, 0.5 to 20 gpm  Needs higher pressure, 35 to 75 psi  Sprinklers are “constant discharge” and do not automatically provide “matched precipitation” when part-circles are used
  9. 9. *Sprayer Sprinklers  Wets a smaller area, 8 to 16 foot radius  Smaller water flow, 0.25 to 4 gpm  Less pressure required, 20 to 40 psi  Can wet rectangular areas  Automatic “matched precipitation when part- circles sprinklers are used
  10. 10. *Bubblers  good applications in plant beds  wets a small area  low pressure requirement, 15 to 30 psi  low flow rate, 8 gph to 2.5 gpm
  11. 11. *Drip Emitters and Dripline  Good applications in plant beds and vegetable and fruit gardens  very low flow rate, 0.5 to 2.0 gph  very low pressure, 10 to 25 psi (pressure compensating emitters are designed for a greater pressure range)  direct application of water to root zone of individual plants  water must be very clean to prevent clogging of emitters
  12. 12. Ideal Pressure and No Wind How Much Water in the Cans? Even in all cans More in cans closer to the sprinkler More in cans further from the sprinkler *Uniformity of Water Caught in Cans around a Single Sprinkler
  13. 13. *Sprinkler Overlap For Uniformity Distance between Sprinklers = Radius of Throw Head-to-Head Spacing: 1. Good Uniformity 2. Good Economics
  14. 14. *Rules for Spacing Sprinklers. 1. Pick a sprinkler with a wetted radius that is as large as possible and does not greatly exceed the shortest distance across the area. 2. Place part-circle sprinklers at all corners 3. Place part-circle sprinklers at an even spacing on the edges between corners using head-to-head spacing as a guide. 4. Place full-circle sprinklers in the interior area using the same head-to- head spacing used on the edge sprinklers. 5. Perfect head-to-head spacing is impossible in most cases. It is O.K. to stretch and/or crowd the spacing by 10%. 6. Adjust the sprinklers to even out the spacing over the entire area and don’t leave a big gap in one area to make the rest of the area even. Are most landscape areas simple squares and rectangles?
  15. 15. Example Landscape Sprinkler Layout
  16. 16. *Zones Avoid Excess Flow Demand A Zone is a group of sprinklers that operate together on the same lateral pipe network downstream from a common valve. Limited Flow Rate of 12 gpm at 45 psi and sprinklers that require 3 gpm 8 sprinklers x 3 gpm/spr = 24 gpm > 12 gpm, a severe pressure drop will occur. 20 psi 20 psi
  17. 17. *Zones Allow Equal Application of Water from Different Equipment Rotating Sprinkler, Full Circle – 0.25 in/hr Sprayers: Full, ½, & ¼ Circle – 1.5 in/hr Rotating Sprinkler, Half Circle – 0.5 in/hr Rotating Sprinkler, Quarter Circle – 1.0 in/hr Drip – 0.1 in/hr
  18. 18. Sizing Pipe with a Velocity Method Flow is Q = 20 gpm 1.5” pipe 1” pipe Proper pipe sizing will reduce friction loss, improve uniformity, save material costs, lower pumping costs and control waterhammer. Velocity Method • Locate pipe network for irrigation system. • Determine the flow in each section of pipe. • Determine the smallest size pipe that keeps flow velocity below 5 feet per sec (fps) Pipe charts are available in most Irrigation Supply Catalogs V = 2.65 ft/sec FL = 0.71 psi/100’ V = 5.71 ft/sec FL = 4.59 psi/100’
  19. 19. Simplified Pipe Chart based on 5 ft/sec Rule Class 160 PVC Pipe Size in Inches Flow (gpm) 1 1 – 15 1 ¼ 16 – 28 1 ½ 29 – 37 2 38 – 59 2 ½ 60 – 85 3 86 – 130 4 131 – 200 5 201 – 325 6 326 – 450
  20. 20. S M Source 1. Corp. Valve 2. Gate Valve 3. Water Meter 4. Backflow Preventor 5. 2” PVC Mainline 200’ 6. 1.5’ Diaphragm Valve 7. 1.25” 20 gpm 8. 1” 9. 1” 10. 1” 40 gpm 15 gpm 10 gpm 5 gpm 11. ¾” or ½” Swing Joint POC Pipe Size in a Zone & Mainline Based on 5 gpm per Sprinkler
  21. 21. Backflow Prevention  If you use utility water  you must have backflow prevention installed  prevents water from flowing backwards into the supply line in case of pressure-loss from within the system industrial-sized backflow prevention
  22. 22. *Swing Joints for Sprayers and Sprinklers  Use a flexible connector-piping from lateral to sprinkler  allows the sprinkler to be set at the correct depth and to be moved deeper if the soil settles  allows sprinkler to move it run-over by tractor tire  reduces damage to lateral
  23. 23. *Valves for Irrigation Zones (sets)  Valves off of the mainline control individual sets  can be manual valves or electric valves  electric valves are needed when using timers
  24. 24. 24 V-AC Solenoid Valves  Magnetic coil is used to open a spring-loaded valve  very common application  easy to rebuild or replace  allows for manual operation
  25. 25. *Controller (timer)  Normal Program  Days of the week to water – MTWThFSaSu  Start time during the day to initiate the valve sequence  Valve run time of each zone (set)  Special Features Available:  Rain Delays  Raingauge shutdown  Soil sensor shutdown
  26. 26. Ar = 96.3 Q = Application rate in inches per hour A Q = Flow or discharge in gallons per minute A = Area into which flow is applied in feet^2 Example: A full-circle sprinkler discharges 2.4 gpm and the sprinkler spacing is 30 by 30 feet. Ar = (96.3 x 2.4) / (30 x 30) = 0.25 inches per hour Application Rate – Flow into an Area
  27. 27. Z 1 1.0 in/hr Z 2 0.5 in/hr Z 3 1.0 in/hr Precipitation Rate Precipitation Rate 2.0 in/hr Z 4 Set Controller to apply 0.5 inches 2 days per week = 1 inch per week Time for zone 1 = 0.5in / 1.0 in/hr = 0.5 hours or 30 min. M Th Valve Tz On Off 1 30 min 10:00 10:30 2 60 min 10:30 11:30 3 30 min 11:30 12:00 4 15 min 12:00 12:15 *Controller Settings and Irrigation Scheduling
  28. 28. Uniformity Impact on Operating Cost Six inches of water required on a half acre lot Municipal Water Cost of $0.61/100gal Driest 10% receives 66% of requirement Uniformity Water Applied Irrigation Cost inches 85% 6.0 $ 510.00 80% 6.2 $ 525.30 75% 7.2 $ 612.00 65% 10.8 $ 918.00
  29. 29. Resources  Landscape Irrigation Design by Eugene W. Rochester, ASAE Publication #8, 0-929355-61-X  Simplified Irrigation Design by Pete Melby, John Wiley & Sons, Inc., ISBN 0-471-28622-22  Ortho’s All About Sprinklers and Drip Systems, Meredith Books Inc, ISBN 0-89721- 413-7  Drip Irrigation for Every Landscape and All Climates by Robert Kourik, Metamorphic Press, ISBN 0-9615848-2-3

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