I Sprinkler Irrigation

8/8/2019 I Sprinkler Irrigation

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Sprinkler IrrigationSprinkler Irrigation



DefinitionDefinition

Pressurized irrigation throughPressurized irrigation through

devices called sprinklersdevices called sprinklers

Sprinklers are usually located onSprinklers are usually located onpipes called lateralspipes called laterals

Water is discharged into the air andWater is discharged into the air and

hopefully infiltrates near where ithopefully infiltrates near where itlandslands



Types of SystemsTypes of Systems

Single sprinkler Single sprinkler ± ± Only one sprinkler that is moved or Only one sprinkler that is moved or

automatically movesautomatically moves

Examples:Examples: ± ± Single lawn sprinkler Single lawn sprinkler

± ± Large gun on a trailer that is moved or Large gun on a trailer that is moved or automatically moves (³traveler´)automatically moves (³traveler´)

Often used for irregularly shaped areasOften used for irregularly shaped areas Pressure and energy requirements canPressure and energy requirements can

be highbe high







Solid SetSolid Set

Laterals are permanently placedLaterals are permanently placed

(enough to irrigate the entire area)(enough to irrigate the entire area)

Laterals are usually buried, withLaterals are usually buried, withrisers or poprisers or pop--up sprinklersup sprinklers

Easily automated and popular for turf Easily automated and popular for turf

and some ag/hort applicationsand some ag/hort applications Capital investment can be highCapital investment can be high



Portable SolidPortable Solid--Set Sprinkler SystemSet Sprinkler System



Fairway Runoff Research PlotsFairway Runoff Research Plots

at OSU Turf Research Farmat OSU Turf Research Farm



Periodically Moved LateralPeriodically Moved Lateral

Single lateral is moved and used inSingle lateral is moved and used inmultiple locationsmultiple locations

Examples:Examples: ± ± HandHand--movemove

± ± TowTow--line/skidline/skid--tow (lateral is pulled acrosstow (lateral is pulled acrossthe field)the field)

± ± SideSide--roll (lateral mounted on wheels thatroll (lateral mounted on wheels thatroll to move the lateral)roll to move the lateral)

Fairly high labor requirementFairly high labor requirement



SideSide--Roll Sprinkler Lateral in PeanutsRoll Sprinkler Lateral in Peanuts



Moving LateralMoving Lateral

Single lateral moves automaticallySingle lateral moves automatically

(mounted on wheeled towers)(mounted on wheeled towers)

Examples:Examples: ± ± Center pivots (lateral pivots in a circle)Center pivots (lateral pivots in a circle)

± ± Linear or lateral move systems (lateralLinear or lateral move systems (lateral

moves in a straight line)moves in a straight line)

Fairly high capital investmentFairly high capital investment



Center Pivot System with Spray Pad SprinklersCenter Pivot System with Spray Pad Sprinklers





System ComponentsSystem Components

SprinklersSprinklers

± ± Devices (usually brass or plastic) with one or moreDevices (usually brass or plastic) with one or more

small diameter nozzlessmall diameter nozzles

Impact sprinklersImpact sprinklers

± ± Drive or range nozzle (hits sprinkler arm and throwsDrive or range nozzle (hits sprinkler arm and throws

water out farther)water out farther)

± ± Spreader nozzle (optional; Applies more water closeSpreader nozzle (optional; Applies more water close

to the sprinkler)to the sprinkler)

± ± Trajectory anglesTrajectory angles

± ± PartPart--circle sprinklerscircle sprinklers

± ± Used in all types of irrigation, but especiallyUsed in all types of irrigation, but especially

agricultural cropsagricultural crops



Impact SprinklersImpact Sprinklers

Impact ArmImpact Arm

Spreader NozzleSpreader Nozzle

Range (Drive) NozzleRange (Drive) Nozzle

BearingBearing

TwoTwo--nozzle, bronze impact sprinklernozzle, bronze impact sprinkler

Trajectory

Angle



Impact SprinklersImpact Sprinklers

RainBird 30 RainBird 14 RainBird 70RainBird 30 RainBird 14 RainBird 70



PopPop--up, partup, part--circle impact sprinkler headcircle impact sprinkler head



Spray Pad devicesSpray Pad devices ± ± Water jet strikes a plate or padWater jet strikes a plate or pad

± ± Pad spreads the water and may be smoothPad spreads the water and may be smooth

or serratedor serrated

± ± Popular on center pivot and linear movePopular on center pivot and linear move

systemssystems

System ComponentsCont¶d.System ComponentsCont¶d.



Spray Pad SprinklersSpray Pad Sprinklers

NozzleNozzle

Smooth DeflectorP

adSmooth DeflectorP

ad Serrated DeflectorP

adSerrated DeflectorP

ad





PopPop--up, turbine rotor with riser extendedup, turbine rotor with riser extended



TurbineTurbine--driven rotor w/ adjustable spray angledriven rotor w/ adjustable spray angle





Spray headsSpray heads ± ± Heads do not rotateHeads do not rotate

± ± Nozzle is shaped to irrigate a certainNozzle is shaped to irrigate a certain

angle of coverageangle of coverage

± ± Typically used for small or irregularlyTypically used for small or irregularly

shaped areasshaped areas

± ± PopPop--up heads are installed flush withup heads are installed flush with

ground and rise when pressurizedground and rise when pressurized

System ComponentsCont¶d.System ComponentsCont¶d.



PopPop--Up Turbine Rotor Sprinklers in OperationUp Turbine Rotor Sprinklers in Operation



PopPop--up spray head with adjustable coverageup spray head with adjustable coverage

angle from 1ºangle from 1º -- 360º360º



PopPop--Up Spray HeadUp Spray Head

³Funny Pipe´ Riser³Funny Pipe´ Riser

Pipe ThreadPipe Thread--Barb AdaptersBarb Adapters

FullFull--circle, 4circle, 4--inch, Popinch, Pop--up spray head w/ Funny Pipe Riserup spray head w/ Funny Pipe Riser



System Components Cont¶d.System Components Cont¶d.

LateralsLaterals

± ± Pipelines that provide water to the sprinklersPipelines that provide water to the sprinklers ± ± May be below, on, or above the groundMay be below, on, or above the ground

RisersRisers ± ± Smaller diameter pipes used to bring water from theSmaller diameter pipes used to bring water from the

lateral to the sprinkler lateral to the sprinkler ± ± PurposesPurposes

± ± Raises the sprinkler so that the plants won'tRaises the sprinkler so that the plants won'tinterfere with the water jetinterfere with the water jet

± ± Reduces turbulence of the water stream as itReduces turbulence of the water stream as itreaches the sprinkler reaches the sprinkler

Mainlines and submainsMainlines and submains ± ± Pipelines that supply water to the lateralsPipelines that supply water to the laterals

± ± May serve several laterals simultaneouslyMay serve several laterals simultaneously



Sprinkler PerformanceSprinkler Performance

DischargeDischarge ± ± Depends on type of sprinkler, nozzle size,Depends on type of sprinkler, nozzle size,

and operating pressureand operating pressure

± ± qqss = discharge (gpm)= discharge (gpm)

± ± CCdd = discharge coefficient for the nozzle and= discharge coefficient for the nozzle and

sprinkler sprinkler }} 0.960.96

± ± D = inside diameter of the nozzle (inches)D = inside diameter of the nozzle (inches)

± ± P = water pressure at the nozzle (psi)P = water pressure at the nozzle (psi)

q C D P s d ! 29 82 2.





Diameter of CoverageDiameter of Coverage ± ± Maximum diameter wetted by the sprinkler Maximum diameter wetted by the sprinkler

at a rate that is significant for the intendedat a rate that is significant for the intended

useuse

± ± Depends on operating pressure andDepends on operating pressure and

sprinkler and nozzle design (includingsprinkler and nozzle design (including

trajectory angle)trajectory angle)

Sprinkler Performance Cont¶d.Sprinkler Performance Cont¶d.





Single Sprinkler



Overlapped SprinklersUniform Application:Uniform Application:

OverlapOverlap uu 50% of 50% of

sprinkler wetted diametersprinkler wetted diameter

NonNon--uniform Application:uniform Application:

Overlap << 50% of Overlap << 50% of

sprinkler wetted diametersprinkler wetted diameter





Overlapped Sprinklers Contd«Overlapped Sprinklers Contd«

Dry zone



Maximum Spacing of SprinklersMaximum Spacing of Sprinklers



Application RateApplication Rate

Rectangular sprinkler layout

± Ar = water application rate (inches/hour)

± qs = sprinkler discharge rate (gpm)

± Sl = sprinkler spacing along the lateral

(feet)

± Sm = lateral spacing along the mainline

(feet)

Aq

S S r

s

l m

!

96 3.

A d t

qar ! !



Equilateral triangular layout

± S = spacing between sprinklers (feet) Depth of water applied

± Ig = Ar To

± Ig = gross depth of water applied per irrigation(inches)

± To = actual time of operation (hours)

Aq

S r

s!

11122

.



Application Rate & Soil Infiltration RateApplication Rate & Soil Infiltration Rate



Sprinkler Example CalculationsSprinkler Example Calculations

A sprinkler system irrigates turf grass on a clay loam soilon a 5% slope in a 10 mph South wind. The sprinklers

are 5/32´, single-nozzle sprinklers with a 23° trajectory

angle operating at 40 psi. The sprinklers are arranged

in a 30 ft x 50 ft rectangular spacing with the lateralsrunning East-West.

a. Is the sprinkler system design satisfactory for these

conditions?

b. How many hours should the system operate in onezone?



Sprinkler ExampleSprinkler Example

From Table 11.1: for 5/32´ @ 40 psi, qs=4.5 gpm.

From Table 11.2: for 5/32´ @ 40 psi, Dw=88 ft.

From Table 11.3: for 8-12 mph wind, Sl max=40% Dw, Sm max=60% Dw

0.4 x 88=35.2 > Sl =30 ft. And 0.6 x 88=52.8 " Sm =50 ft

Sl and Sm are OK . Note: laterals are perpendicular to wind direction

Ar = 96.3 (4.5) = 0.289 in/hr

30 x 50

From Table 11.4: for Turf, Recommended Max. Ar = 0.15-0.35 in/hr

Ar is within the recommended range and is probably OK.

Aq

S S

r

s

l m

!

96 3.



Sprinkler ExampleSprinkler Example

From Table 2.3: AWC for clay loam= 0.15 in/in

From Table 6.3: R d for turf grass= 0.5-2.0 ft. Assume R d= 12 in.

TAW=AWC x R d = 0.15 x 12 = 1.8 in

For lawn turf assume f d max= 0.50

AD= TAW x f d max = 1.8 x 0.50 = 0.90

To prevent deep percolation loss dneAD

Assume Ea = 80%, so dn=0.8 dg , or dg=dn/0.8 = 0.9/0.8=1.125

From Eq. 11.4 dg = Ar To, so

To = dg/Ar = 1.125/0.289= 3.9 hrs.



Hydraulics of LateralsHydraulics of Laterals

Review of friction loss in a lateral:

± Calculate as though it's a mainline

± Then multiply by multiple outlet factor (Table

7.3)

± For a large number of sprinklers, this factor is

approximately equal to 0.35

± This gives total friction loss along the entirelateral length

± Or use the RainBird Slide Rule to calculate

P V i ti AlP V i ti Al



Pressure Variation Along aPressure Variation Along a

LateralLateral General trendsGeneral trends

± ± Maximum at the inlet and minimum atMaximum at the inlet and minimum at

distal end (assuming level lateral)distal end (assuming level lateral)

± ± Linear variation in between? NO!Linear variation in between? NO!

± ± Equations for a level lateralEquations for a level lateral

P P P i a l

!

3

4

P P P d a l

!

1

4

Where:Where:

P P i i =inlet pressure=inlet pressure

P P aa=average pressure=average pressure

P P d d =distal pressure=distal pressure

P P l l =pressure loss=pressure loss





Equations for a Sloping LateralEquations for a Sloping Lateral

± ± E's are elevations of the ends of the lateral (in feet)E's are elevations of the ends of the lateral (in feet)

± ± Above equations assume half the elevation change Above equations assume half the elevation changeoccurs upstream of the average pressure point, andoccurs upstream of the average pressure point, and

half occurs downstream of that point (even if thathalf occurs downstream of that point (even if that

assumption is not quite true, equations still workassumption is not quite true, equations still work

pretty well)pretty well)

P P P E E

i a l

i d ! ¨ª© ¸

º¹3

4

1

2 2 31.

P P P E E

d a l

i d

! ª̈© ¸ º¹1

4

1

2 2 31.



Allowable PressureAllowable Pressure

VariationVariation

Based on uniformity considerations,Based on uniformity considerations,

recommendation is that (qrecommendation is that (qmaxmax -- qqminmin) not) not

exceed 10% of qexceed 10% of qavgavg

Because of square root relationshipBecause of square root relationship

between pressure and discharge, thisbetween pressure and discharge, this

is the same as saying (Pis the same as saying (Pmaxmax -- PPminmin))

should not exceed 20% of Pshould not exceed 20% of Pavgavg::

Maximum PMaximum Pll << 0.20 x P0.20 x Paa











Maximum Lateral InflowMaximum Lateral Inflow

Constrained by:

± Maximum allowable pressure variation

(more Q = more Pl) ± Maximum allowable pipeline velocity (more

Q = higher velocity)

Figure 11.10 -- assumes portable Al

pipe and Vmax of 10 ft/s





Example ProblemExample Problem



Other Design and ManagementOther Design and Management



Other Design and ManagementOther Design and Management

ConsiderationsConsiderations Sprinkler selection

± ± qqss = minimum sprinkler discharge (gpm)= minimum sprinkler discharge (gpm)

± ±QQcc = gross system capacity (gpm/acre)= gross system capacity (gpm/acre)

± ± SSll = spacing between sprinklers along the lateral (feet)= spacing between sprinklers along the lateral (feet)

± ± SSmm = spacing between laterals along the mainline (feet)= spacing between laterals along the mainline (feet)

± ± NNss = number of sets required to irrigate the entire area= number of sets required to irrigate the entire area

± ± NNll = number of laterals used to irrigate the entire area= number of laterals used to irrigate the entire area ± ± TToo = time of actual operation per set (hours)= time of actual operation per set (hours)

± ± TTss = total set time (hours)= total set time (hours)

± ± IIii = irrigation inter val (days)= irrigation inter val (days)

± ± TTdd = system= system down time during the irrigation inter val (days)

qQ S S N

N

T

T

I

I T s

c l m s

l

s

o

i

i d

! ¨

ª©

¸

º¹

¨

ª©

¸

º¹

43560





Example ProblemExample Problem



50

0.55

5.3



Required Lateral InflowRequired Lateral Inflow

± ± QQll = inflow to the lateral (gpm)= inflow to the lateral (gpm)

± ± L = length of the lateral (feet)L = length of the lateral (feet)

± ± QQll must not exceed maximum allowable based onmust not exceed maximum allowable based on

friction loss or velocityfriction loss or velocity

System layoutSystem layout

± ± Generally best to run the mainline up and down theGenerally best to run the mainline up and down the

slope and run the laterals on the contour slope and run the laterals on the contour

± ± If laterals must be sloping, best to run them downslopeIf laterals must be sloping, best to run them downslope

± ± Wind is also a factor (prefer laterals runningWind is also a factor (prefer laterals running

perpendicular to wind direction; because normally, Sperpendicular to wind direction; because normally, Smm >>

SSll))

Qq L

S l

s

l

!

C t Pi t L t lC t Pi t L t l



Center Pivot LateralsCenter Pivot Laterals

³Multiple outlet³Multiple outlet

factor" is 0.543factor" is 0.543

(higher than in(higher than in

conventionalconventionallaterals becauselaterals because

more water mustmore water must

be conveyed tobe conveyed to

the distal end)the distal end)

Area Inside: 118.2 acArea Inside: 118.2 ac95.7 ac95.7 ac

75.6 ac75.6 ac

57.9 ac57.9 ac

42.5 ac42.5 ac

29.5 ac29.5 ac

18.9 ac18.9 ac10.6 ac10.6 ac

Radius: 128Radius: 128

256256

384384

512512

640640

768768

896896

10241024

11521152

12801280



Center Pivot Laterals Cont¶d.Center Pivot Laterals Cont¶d.

Use the distal sprinkler as the "benchmark"Use the distal sprinkler as the "benchmark"

and then calculate the inlet pressure and theand then calculate the inlet pressure and the

pressure distribution along the lateralpressure distribution along the lateral (as(asopposed to stationary laterals, where theopposed to stationary laterals, where the

average pressure was used determineaverage pressure was used determine

acceptable friction loss and pressureacceptable friction loss and pressure

variation)variation) But linear move lateral is analyzed like aBut linear move lateral is analyzed like a

stationary lateral (area irrigated does notstationary lateral (area irrigated does not

change as you move down the lateral)change as you move down the lateral)

Application DepthApplication Depth



Application DepthApplication Depth

The application depth of aThe application depth of a

continuously moving sprinkler continuously moving sprinkler

system depends on the water system depends on the water pumping rate, Q; the total pumping rate, Q; the total

acreage irrigated, A; and the timeacreage irrigated, A; and the time

required to cover the area, Trequired to cover the area, Taa..

The time to cover the irrigatedThe time to cover the irrigatedarea is adjusted by thearea is adjusted by the ³Percent³Percent

Setting´Setting´ of the system. On aof the system. On a

center pivot, this sets whatcenter pivot, this sets what

percent of the time the tower percent of the time the tower

motor on the outermost tower ismotor on the outermost tower isrunningrunning-- from 0% to 100%. Atfrom 0% to 100%. At

100% a ¼100% a ¼--section pivot takes 22section pivot takes 22

hrs to cover its 125 acre circle.hrs to cover its 125 acre circle.

Percent Setting KnobPercent Setting Knob



Center Pivot Application DepthCenter Pivot Application Depth

Center pivot application rate depends on:Center pivot application rate depends on:

the area irrigated, A (acres) = Lthe area irrigated, A (acres) = L22/13866/13866

± ± wherewhere (L= lateral length, ft)(L= lateral length, ft)

the pumping rate, Q (gpm)the pumping rate, Q (gpm)

the actual travel time/revolution, Tthe actual travel time/revolution, Taa (hours)(hours)

± ± TTaa = 100 (T= 100 (Tminmin)/P)/P

where Twhere Tminmin = minimum travel time (normally 22 hr)= minimum travel time (normally 22 hr) where P = percent speed setting, (0%where P = percent speed setting, (0% -- 100%)100%)



Center Pivot Application DepthCenter Pivot Application Depth

The actual application depth is given by:The actual application depth is given by:

d = (Q Td = (Q Taa) / (453 A)) / (453 A)

Example:Example:

A 1300A 1300--ft long center pivot has a minimum travel time of 21 hrs atft long center pivot has a minimum travel time of 21 hrs at

its 100% setting and is supplied with a flow rate of 800 gpm.its 100% setting and is supplied with a flow rate of 800 gpm.

What is the depth of application at a 20% speed setting?What is the depth of application at a 20% speed setting?

A= 1300A= 130022/13866 = 121.9 acres/13866 = 121.9 acres Q = 800 gpmQ = 800 gpm

TTaa = 100 (21)/20 = 105 hrs= 100 (21)/20 = 105 hrs

d = (800 gpm x 105 hrs)/(453 x 121.9 acres) = 1.52 inchesd = (800 gpm x 105 hrs)/(453 x 121.9 acres) = 1.52 inches



LateralMove Application RateLateralMove Application Rate

Lateral system application rate depends on:Lateral system application rate depends on:

The area irrigated, A (acres) = L DThe area irrigated, A (acres) = L Dtt/43560/43560

± ± where L = lateral length, (ft)where L = lateral length, (ft)

± ± where Dwhere Dtt = travel distance of lateral, (ft)= travel distance of lateral, (ft)

The actual system flow rate, (gpm)The actual system flow rate, (gpm)

The actual travel time TThe actual travel time Taa (hr) = 100 T(hr) = 100 Tminmin/P/P

± ± TTaa = 100 (T= 100 (Tminmin)/P)/P where Twhere Tminmin = minimum time to move distance D= minimum time to move distance Dt,t, (hr)(hr)

where P = percent speed setting, (0%where P = percent speed setting, (0% -- 100%)100%)



LateralMove Application DepthLateralMove Application Depth

The actual application depth is given by:The actual application depth is given by:

d = (Q Td = (Q Taa) / (453 A)) / (453 A)

Example:Example:

A 1320A 1320--ft long lateral move system has a minimum travel time of ft long lateral move system has a minimum travel time of

14 hrs at the 100% setting over its travel distance of 2640 ft and is14 hrs at the 100% setting over its travel distance of 2640 ft and is

supplied with a flow rate of 600 gpm. What is the depth of supplied with a flow rate of 600 gpm. What is the depth of

application at a 17% speed setting?application at a 17% speed setting?

A= 1320 x 2640/43560 = 80 acresA= 1320 x 2640/43560 = 80 acres Q = 600 gpmQ = 600 gpm

TTaa = 100 (14)/17 = 82.35 hrs= 100 (14)/17 = 82.35 hrs

d = (600 gpm x 82.35 hrs)/(453 x 80 acres) = 1.35 inchesd = (600 gpm x 82.35 hrs)/(453 x 80 acres) = 1.35 inches

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I Sprinkler Irrigation