© Irrigation Association Effect of Irrigation

© Irrigation Association Calculate Hydraulic Requirements Chapter 4:

© Irrigation Association Predicting Friction Losses Calculating friction losses Head (pressure) required at the pivot point Based on what the pivot “thinks” it is irrigating Calculating pressures, sprinkler by sprinkler Mainline layout and sizing Page 59

© Irrigation Association Supply (Main) Line – 1,000 gpm – 8” (approx) pipe

© Irrigation Association 1,000 gpm Total – Identical Outlets at 40’ – 8” (approx.) Pipe

© Irrigation Association 1,000 gpm total – 125 gpm end gun – sprinklers at 20’ 8” (approx) pipe Page 62

© Irrigation Association Practice Session on Friction Loss Hydraulic Length Lateral Size (single size) C = 145 (why?) Lateral friction loss Span Lengths (Obstacles?) Page 66

Friction Loss Hazen-Williams equation © Irrigation Association

Center Pivot Flow Rate Distribution

In a system having an end gun, the flow rate at the end of the pipe is equal to the discharge of the end gun, rather than zero © Irrigation Association

Hyrdualic length where: L h = the equivalent hydraulic length of the center-pivot lateral, ft (or m) L = the physical length of the center-pivot lateral, ft (or m) Qb = the “base” discharge for the basic circle, gpm (or L/s) Qs = the discharge for all of the area irrigated by the center pivot lateral, gpm (or L/s) (generally, Qs = Qb + Qg) Qg = the discharge of the end gun, if one is present, gpm (or L/s). © Irrigation Association

Multiple Sized Laterals Page 66-78

© Irrigation Association Additional Hydraulic Calculations Calculating Velocity & Velocity Head Pressure Required at the Pivot Point Simple Energy Conservation Impact of Pressure Regulators Elevation Considerations Page 80

© Irrigation Association Friction Losses at Tower Joint? H-W “C”? Page 84

Energy Balance Equation Bernoulli Accounts For Total Energy of water between two points Pressure head Elevation head Velocity head Friction head

Energy Balance Equation Bernoulli - Head P 1 + z 1 + V 1 2 / 2g = P 2 + z 2 + V 2 2 / 2g – H f 1-2 EQ Where: P 1 = Pressure head at point 1, feet Z 1 = Elevation head at point 1, feet V 1 2 / 2g= Velocity head at point 1, feet P 2 = Pressure head at point 1, feet z 2 = Elevation head at point 1, feet V 2 2 / 2g= Velocity head at point 1, feet H f 1-2 = Friction loss between points 1 and 2, feet

© Irrigation Association Practice Example Design Project Minimum Sprinkler Pressure Elevation Rise Nozzle Height Above Ground Pivot Pressure at Ground Level Page 88

© Irrigation Association Look at each section of one- diameter pipe separately Compare to a pivot with all that size pipe Add the friction losses together Calculating Pressure Section by Section Page 89

© Irrigation Association Section-by-section

© Irrigation Association Nozzle discharge

© Irrigation Association End Guns & Corner Systems Have Significant Effects on Hydraulics

© Irrigation Association Varying Pivot Flow Rates (Affects Pump Selction)

© Irrigation Association Affect on Pumping Requirements

© Irrigation Association Mainline Layout and Sizing Layout of clusters Economic vs. hydraulically “best” solution More small diameter pipe vs. less larger pipe Page 89

© Irrigation Association Mainline Configuration a. Length of feeder pipe = 6 x lateral length b. Length of feeder pipe = 7.7 x lateral length Page 90

© Irrigation Association Supply (Main) Line Selection Friction Losses in Supply (Main) Line Pressure required at start Pipe diameter (velocity method) Friction losses Sizing using economic criteria Surge Pressures (Water hammer) Appendix D Valve placement, Air-vac, Pressure relief, Sediment traps

© Irrigation Association Screening Requirements

© Irrigation Association Practice Example Pages 94-96