Sprinkler Irrigation. Definition Pressurized irrigation through devices called sprinklers...
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Transcript of Sprinkler Irrigation. Definition Pressurized irrigation through devices called sprinklers...
Sprinkler IrrigationSprinkler Irrigation
DefinitionDefinition
• Pressurized irrigation through Pressurized irrigation through devices called sprinklersdevices called sprinklers
• Sprinklers are usually located Sprinklers are usually located on pipes called lateralson pipes called laterals
• Water is discharged into the Water is discharged into the air and hopefully infiltrates air and hopefully infiltrates near where it landsnear where it lands
Types of SystemsTypes of Systems • Single sprinklerSingle sprinkler
– Only one sprinkler that is moved or Only one sprinkler that is moved or automatically movesautomatically moves
• Examples:Examples:– Single lawn sprinklerSingle lawn sprinkler– Large gun on a trailer that is moved Large gun on a trailer that is moved
or automatically moves (“traveler”)or automatically moves (“traveler”)• Often used for irregularly shaped Often used for irregularly shaped
areasareas• Pressure and energy Pressure and energy
requirements can be highrequirements can be high
Traveling Volume Gun Sprinkler Irrigating from LagoonTraveling Volume Gun Sprinkler Irrigating from Lagoon
Solid SetSolid Set
• Laterals are permanently placed Laterals are permanently placed (enough to irrigate the entire (enough to irrigate the entire area)area)
• Laterals are usually buried, with Laterals are usually buried, with risers or pop-up sprinklersrisers or pop-up sprinklers
• Easily automated and popular for Easily automated and popular for turf and some ag/hort turf and some ag/hort applicationsapplications
• Capital investment can be highCapital investment can be high
Portable Solid-Set Sprinkler SystemPortable Solid-Set Sprinkler System
Fairway Runoff Research PlotsFairway Runoff Research Plotsat OSU Turf Research Farmat OSU Turf Research Farm
Periodically Moved Periodically Moved LateralLateral
• Single lateral is moved and used Single lateral is moved and used in multiple locationsin multiple locations
• Examples:Examples:– Hand-moveHand-move– Tow-line/skid-tow (lateral is pulled Tow-line/skid-tow (lateral is pulled
across the field)across the field)– Side-roll (lateral mounted on Side-roll (lateral mounted on
wheels that roll to move the wheels that roll to move the lateral)lateral)
• Fairly high labor requirementFairly high labor requirement
Side-Roll Sprinkler Lateral in PeanutsSide-Roll Sprinkler Lateral in Peanuts
Moving LateralMoving Lateral
• Single lateral moves Single lateral moves automatically (mounted on automatically (mounted on wheeled towers)wheeled towers)
• Examples:Examples:– Center pivots (lateral pivots in a Center pivots (lateral pivots in a
circle)circle)– Linear or lateral move systems Linear or lateral move systems
(lateral moves in a straight line)(lateral 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 Devices (usually brass or plastic) with one
or more small diameter nozzlesor more small diameter nozzles
• Impact sprinklersImpact sprinklers– Drive or range nozzle (hits sprinkler arm Drive or range nozzle (hits sprinkler arm
and throws water out farther)and throws water out farther)– Spreader nozzle (optional; Applies more Spreader nozzle (optional; Applies more
water close to the sprinkler)water close to the sprinkler)– Trajectory anglesTrajectory angles– Part-circle sprinklersPart-circle sprinklers– Used in all types of irrigation, but Used in all types of irrigation, but
especially agricultural cropsespecially agricultural crops
Impact SprinklersImpact Sprinklers
Impact ArmImpact Arm
Spreader NozzleSpreader Nozzle
Range (Drive) NozzleRange (Drive) Nozzle
BearingBearing
Two-nozzle, bronze impact sprinklerTwo-nozzle, bronze impact sprinkler
Trajectory Angle
Impact SprinklersImpact Sprinklers
RainBird 30 RainBird 14 RainBird 70RainBird 30 RainBird 14 RainBird 70
Pop-up, part-circle impact sprinkler headPop-up, part-circle 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 Pad spreads the water and may be
smooth or serratedsmooth or serrated– Popular on center pivot and linear Popular on center pivot and linear
move systemsmove systems
System Components Cont’d.System Components Cont’d.
Spray Pad SprinklersSpray Pad Sprinklers
NozzleNozzle
Smooth Deflector PadSmooth Deflector Pad Serrated Deflector PadSerrated Deflector Pad
System Components Cont’d.System Components Cont’d.
• Gear-driven rotors (rotary Gear-driven rotors (rotary heads)heads)– Energy in the water turns a Energy in the water turns a
turbine that rotates the nozzle turbine that rotates the nozzle through a gear trainthrough a gear train
– Typically used in large, open Typically used in large, open turf/landscape areasturf/landscape areas
Pop-up, turbine rotor with riser extendedPop-up, turbine rotor with riser extended
Turbine-driven rotor w/ adjustable spray angleTurbine-driven rotor w/ adjustable spray angle
Pop-up, turbine rotor complete Pop-up, turbine rotor complete with swing arm and teewith swing arm and tee
• Spray headsSpray heads– Heads do not rotate Heads do not rotate – Nozzle is shaped to irrigate a Nozzle is shaped to irrigate a
certain angle of coveragecertain angle of coverage– Typically used for small or Typically used for small or
irregularly shaped areasirregularly shaped areas– Pop-up heads are installed flush Pop-up heads are installed flush
with ground and rise when with ground and rise when pressurizedpressurized
System Components Cont’d.System Components Cont’d.
Pop-Up Turbine Rotor Sprinklers in OperationPop-Up Turbine Rotor Sprinklers in Operation
Pop-up spray head with adjustable coverage Pop-up spray head with adjustable coverage angle from 1º - 360ºangle from 1º - 360º
Pop-Up Spray HeadPop-Up Spray Head
““Funny Pipe” RiserFunny Pipe” Riser
Pipe Thread-Barb AdaptersPipe Thread-Barb Adapters
Full-circle, 4-inch, Pop-up spray head w/ Funny Pipe RiserFull-circle, 4-inch, Pop-up spray head w/ Funny Pipe Riser
System Components Cont’d.System Components Cont’d.• LateralsLaterals
– Pipelines that provide water to the Pipelines that provide water to the sprinklerssprinklers
– May be below, on, or above the groundMay be below, on, or above the ground
• RisersRisers– Smaller diameter pipes used to bring water Smaller diameter pipes used to bring water
from the lateral to the sprinklerfrom the lateral to the sprinkler– PurposesPurposes– Raises the sprinkler so that the plants Raises the sprinkler so that the plants
won't interfere with the water jetwon't interfere with the water jet– Reduces turbulence of the water stream as Reduces turbulence of the water stream as
it reaches the sprinklerit 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 Depends on type of sprinkler, nozzle size, and operating pressuresize, and operating pressure
– qqss = discharge (gpm) = discharge (gpm)
– CCdd = discharge coefficient for the nozzle = discharge coefficient for the nozzle and and sprinkler sprinkler 0.96 0.96
– D = inside diameter of the nozzle D = inside diameter of the nozzle (inches)(inches)
– P = water pressure at the nozzle (psi)P = water pressure at the nozzle (psi)
q C D Ps d29 82 2.
• Diameter of CoverageDiameter of Coverage– Maximum diameter wetted by the Maximum diameter wetted by the
sprinkler at a rate that is significant sprinkler at a rate that is significant for the intended usefor the intended use
– Depends on operating pressure and Depends on operating pressure and sprinkler and nozzle design sprinkler and nozzle design (including(including trajectory angle)trajectory angle)
Sprinkler Performance Cont’d.Sprinkler Performance Cont’d.
Single Sprinkler
Overlapped SprinklersUniform Application: Uniform Application: Overlap Overlap 50% of 50% of sprinkler wetted diametersprinkler wetted diameter
Non-uniform Application: Non-uniform Application: Overlap << 50% of Overlap << 50% of sprinkler wetted diametersprinkler wetted diameter
No wind
Elongated parallel pattern
Overlapped Sprinklers Overlapped Sprinklers Contd…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 Srs
l m
96 3.
Ad
t
q
ar
• 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
Srs
11122
.
Application Rate & Soil Infiltration Application Rate & Soil Infiltration RateRate
Sprinkler Example Sprinkler Example CalculationsCalculations
A sprinkler system irrigates turf grass on a clay loam soil on 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 laterals running East-West.
a. Is the sprinkler system design satisfactory for these conditions?
b. How many hours should the system operate in one zone?
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 Srs
l m
96 3.
Sprinkler ExampleSprinkler Example
From Table 2.3: AWC for clay loam= 0.15 in/in
From Table 6.3: Rd for turf grass= 0.5-2.0 ft. Assume Rd= 12 in.
TAW=AWC x Rd = 0.15 x 12 = 1.8 in
For lawn turf assume fd max= 0.50
AD= TAW x fd max = 1.8 x 0.50 = 0.90
To prevent deep percolation loss dnAD
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
entire lateral length– Or use the RainBird Slide Rule to
calculate
Pressure Variation Along Pressure Variation Along a Laterala Lateral
• General trendsGeneral trends– Maximum at the inlet and minimum Maximum at the inlet and minimum
at distal end (assuming level at distal end (assuming level lateral)lateral)
– Linear variation in between? NO! Linear variation in between? NO! – Equations for a level lateral Equations for a level lateral
P P Pi a l 3
4
P P Pd a l 1
4
Where:Where:
PPi i =inlet pressure=inlet pressure
PPa a =average pressure=average pressure
PPd d =distal pressure=distal pressure
PPl l =pressure loss=pressure loss
Pressure DistributionPressure Distribution
Equations for a Sloping Equations for a Sloping LateralLateral
– E's are elevations of the ends of the lateral (in E's are elevations of the ends of the lateral (in feet)feet)
– Above equations assume half the elevation change Above equations assume half the elevation change occurs upstream of the average pressure point, occurs upstream of the average pressure point, and half occurs downstream of that point (even if and half occurs downstream of that point (even if that assumption is not quite true, equations still that assumption is not quite true, equations still work pretty well)work pretty well)
P P PE E
i a li d
3
4
1
2 2 31.
P P PE E
d a li d
1
4
1
2 2 31.
Allowable Pressure Allowable Pressure VariationVariation
• Based on uniformity considerations, Based on uniformity considerations, recommendation is that (qrecommendation is that (qmaxmax - q - qminmin) )
not exceed 10% of qnot exceed 10% of qavg avg
• Because of square root relationship Because of square root relationship between pressure and discharge, this between pressure and discharge, this is the same as saying (Pis the same as saying (Pmaxmax - P - Pminmin) )
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 Management Other 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 interval (days) = irrigation interval (days)
– TTdd = system = system down time during the irrigation interval (days)
qQ S S N
N
T
T
I
I Tsc l m s
l
s
o
i
i d
43560
Sprinkler Selection, Sprinkler Selection, Cont’d.Cont’d.
• NNss = number of sets required to irrigate the entire = number of sets required to irrigate the entire areaarea
• Wf = width of the field or area (feet)
• SSmm = spacing between laterals along the mainline = spacing between laterals along the mainline (feet)(feet)
• Note: Choose a combination of nozzle size and operating pressure to provide the desired qs
NW
Ss
f
m
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 on must 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 Generally best to run the mainline up and down
the slope and run the laterals on the contourthe slope and run the laterals on the contour– If laterals must be sloping, best to run them If laterals must be sloping, best to run them
downslopedownslope– Wind is also a factor (prefer laterals running Wind is also a factor (prefer laterals running
perpendicular to wind direction; because normally, perpendicular to wind direction; because normally, SSmm > S > Sll))
Qq L
Sls
l
Center Pivot LateralsCenter Pivot Laterals
• ““Multiple outlet Multiple outlet factor" is 0.543 factor" is 0.543 (higher than in (higher than in conventional conventional laterals laterals because more because more water must be water must be conveyed to conveyed to the distal end)the distal end)
Area Inside: 118.2 acArea Inside: 118.2 ac
95.7 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 ac 10.6 ac10.6 ac
Radius: 128Radius: 128256256384384512512640640
768768
896896
10241024
11521152
12801280
Center Pivot Laterals Center Pivot Laterals Cont’d.Cont’d.
• Use the distal sprinkler as the "benchmark" Use the distal sprinkler as the "benchmark" and then calculate the inlet pressure and and then calculate the inlet pressure and the pressure distribution along the lateral the pressure distribution along the lateral
(as opposed to stationary laterals, (as opposed to stationary laterals, where the average pressure was used where the average pressure was used determine acceptable friction loss and determine acceptable friction loss and pressure variation)pressure variation)
• But linear move lateral is analyzed like a But linear move lateral is analyzed like a stationary lateral (area irrigated does not stationary lateral (area irrigated does not change as you move down the lateral)change as you move down the lateral)
Application DepthApplication Depth
The application depth of a The 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 acreage irrigated, A; and the time required to cover the area, time required to cover the area, TTaa..
The time to cover the irrigated The time to cover the irrigated area is adjusted by the area is adjusted by the “Percent “Percent Setting”Setting” of the system. On a of the system. On a center pivot, this sets what center pivot, this sets what percent of the time the tower percent of the time the tower motor on the outermost tower is motor on the outermost tower is running- from 0% to 100%. At running- from 0% to 100%. At 100% a ¼-section pivot takes 22 100% a ¼-section pivot takes 22 hrs to cover its 125 acre circle.hrs to cover its 125 acre circle.
Percent Setting Percent Setting KnobKnob
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, Ta a (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% - 100%) where P = percent speed setting, (0% - 100%)
Center Pivot Application DepthCenter Pivot Application DepthThe 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 1300-ft long center pivot has a minimum travel time of 21 hrs at A 1300-ft 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
Lateral Move Application RateLateral Move 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% - 100%) where P = percent speed setting, (0% - 100%)
Lateral Move Application DepthLateral Move Application DepthThe 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 1320-ft long lateral move system has a minimum travel time of A 1320-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 is 14 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