8/13/2019 Micro Irrigation Design Method
1/63
Microirrigation design
Oregon NRCS Engineering MeetingJanuary 11-14, 2005
NaturalResourcesConservationServiceNRCS
United States Department of Agriculture
8/13/2019 Micro Irrigation Design Method
2/63
Over viewWater requirement System Flow ratePressure requirement Component design
8/13/2019 Micro Irrigation Design Method
3/63
Wind breaks/trees
8/13/2019 Micro Irrigation Design Method
4/63
Orchards
8/13/2019 Micro Irrigation Design Method
5/63
Vine crops
8/13/2019 Micro Irrigation Design Method
6/63
Nursery crops
8/13/2019 Micro Irrigation Design Method
7/63
High Dollar crops
8/13/2019 Micro Irrigation Design Method
8/63
Low Dollar crops
8/13/2019 Micro Irrigation Design Method
9/63
Water Quality
Water quality factors can be divided into threemajor categories:
physical clogging caused mostly by suspended solids,
chemical clogging resulting from pH of the water,dissolved solids, sodium, calcium, magnesium and
total iron and
biological clogging resulting from algae and bacterialpopulations.
8/13/2019 Micro Irrigation Design Method
10/63
8/13/2019 Micro Irrigation Design Method
11/63
System Flow rate
8/13/2019 Micro Irrigation Design Method
12/63
Depth of application .Net depth of application shall be sufficient to
replace the water used by the plant during theplant peak use period.
Applications shall include adequate water forleaching to maintain a steady state saltbalance.
NRCS Standards
8/13/2019 Micro Irrigation Design Method
13/63
.Fn = 1.604 QNTE
AFWhere:
Fn = net application depth, in/day/design areaQ = discharge rate, gal/hr/emitterN = number of orifices or emittersT= hours of operation per day, 22 hours maximumE = field application efficiency, expressed as a decimal, not
greater than 0.90 for design purposes.A = ft 2 of field area served by N (number of emitters)F = the design area as a percentage of the field area, expressed as
a decimal1.604 = units conversion constant
Depth of application
8/13/2019 Micro Irrigation Design Method
14/63
shall be adequate to meet the intended waterdemands during the peak use period
shall include an allowance for reasonablewater losses (evaporation, runoff, and deeppercolation) during application periods.
shall have the capacity to apply a specifiedamount of water to the design area within thenet operation period.
System capacity .
8/13/2019 Micro Irrigation Design Method
15/63
should have a minimum design capacitysufficient to deliver the peak daily irrigationwater requirements in 90% of the timeavailable, but not to exceed 22 hours ofoperation per day.
Field application efficiency (E) for designpurposes shall not exceed 90 percent.
System capacity Continued
8/13/2019 Micro Irrigation Design Method
16/63
shall be adequate to provide water distributionto the plant root zone and percent plant
wetted area (P w).
Number and spacing of emitters .
8/13/2019 Micro Irrigation Design Method
17/63
Wetted Area
8/13/2019 Micro Irrigation Design Method
18/63
Percent Wetted Area
For widely spaced crops such as vines, bushes,and trees, a reasonable design objective is to
wet at least one-third and up to one-half of thehorizontal cross-sectional area of the rootsystem.smaller Pw is favored for economic reasons.rows spaced less than 6 ft. (1.83 m) apart, thePw may approach 100 %.
8/13/2019 Micro Irrigation Design Method
19/63
Wetted area single row
8/13/2019 Micro Irrigation Design Method
20/63
f
8/13/2019 Micro Irrigation Design Method
21/63
Components of a Drip system
8/13/2019 Micro Irrigation Design Method
22/63
Subunit Design
Plant and emitter spacing Average emitter flow rate and allowablepressure head variationsDesired number of operating stationsOverall length of plant rows in field orsubsetNumber of plant rows in field or subsetField topography
8/13/2019 Micro Irrigation Design Method
23/63
Emitter types
Long path emitters,Short orifice emitters,
Vortex emitters,Pressure compensating emitters,Porous pipe or tube emitters.
8/13/2019 Micro Irrigation Design Method
24/63
8/13/2019 Micro Irrigation Design Method
25/63
Emitters
Flow is characterized bythe following equation
q=kPx
K and x obtained frommanufacture
8/13/2019 Micro Irrigation Design Method
26/63
Lateral Design
Types of lateralsHeavy wall drip line
Thin wall drip lineDrip tapePolypipe with punchemitters
Polypipe with sprays
8/13/2019 Micro Irrigation Design Method
27/63
8/13/2019 Micro Irrigation Design Method
28/63
Slope and topography
1 0 7
9 8
8 2 0 0
8 2 0 0
8 1 0 0
8 1 0 0
8 0 0 0
8 0 0 0
7 9 0 0
7 9 0 0
7 8 0 0
7 8 0 0
7 7 0 0
7 7 0 0
7 6 0 0
7 6 0 0
7 5 0 0
7 5 0 0
7 4 0 0
7 4 0 0
7 3 0 0
7 3 0 0
7 2 0 0
7 2 0 0
7 1 0 0
7 1 0 0
7 0 0 0
7 0 0 0
6 9 0 0
6 9 0 0
6 8 0 0
6 8 0 0
6 7 0 0
6 7 0 0
62 00
6 20 0
6 100
6 10 0
6000
6 000
59 00
590 0
5 80 0
58 00
57 00
5 70 0
5 600
560 0
550 0
5 500
54 00
5400
5 30 0
530 0
52 00
52 00
1 0 6
1 0 5
1 0 4 1
0 3
1 0 2
1 0 1
1 0 0
9 9
9 9
8/13/2019 Micro Irrigation Design Method
29/63
Hydraulics
60
133.'
100
'
75.4
75.1
a
e
e
ee
f
qS L
Q
S f S
DQ J
FL J h
F= multiple outlet factor
L= length of lateral (ft)
Q= lateral flow rate (gpm)
Se= emitter spacing (ft)
Fe= equivalent length ofemitter connection loss
qa= average emitter flow
rate
8/13/2019 Micro Irrigation Design Method
30/63
Emission Uniformity
Emission Uniformity Rating90 - 100% Excellent
80 - 90% Good70 - 80% FairLess than 70% Poor
ave
v
nC EU m in27.11
8/13/2019 Micro Irrigation Design Method
31/63
Lateral Flow flat slope
8/13/2019 Micro Irrigation Design Method
32/63
Lateral Flow 2% downhill slope
8/13/2019 Micro Irrigation Design Method
33/63
Lateral flow 2% uphill slope
8/13/2019 Micro Irrigation Design Method
34/63
Lateral flow varied slope
8/13/2019 Micro Irrigation Design Method
35/63
Eurodrip program print out
8/13/2019 Micro Irrigation Design Method
36/63
Lateral flow Plot
8/13/2019 Micro Irrigation Design Method
37/63
System flushing .
Appropriate fittings shall be installed aboveground at the ends of all mains, submains,
and laterals to facilitate flushing. A minimumflow velocity of 1 ft/sec is consideredadequate for flushing.
8/13/2019 Micro Irrigation Design Method
38/63
8/13/2019 Micro Irrigation Design Method
39/63
Manifold Design
Needed informationFlow rateInlet location
Pipe sizesInlet pressureFlow variation
Emissions uniformity
8/13/2019 Micro Irrigation Design Method
40/63
8/13/2019 Micro Irrigation Design Method
41/63
Above ground
8/13/2019 Micro Irrigation Design Method
42/63
Manifold and lateral lines.
shall be designed to provide discharge to anyapplicator in an irrigation subunit operatedsimultaneously such that they will not exceeda total variation of 20 percent of the designdischarge rate.
Allowable pressure variations.
8/13/2019 Micro Irrigation Design Method
43/63
Greatest Emitter Discharge - Smallest Emitter Discharge x 100 Average Emitter Discharge
This is reported in Percent and must be less than orequal to 20%
Allowable Pressure Variations
8/13/2019 Micro Irrigation Design Method
44/63
F
F
F
F
F
SECTION VALVE
VACUUM/RELIEF
FLUSH VALVE
AIR RELIEF
WATER SOURCE
FILTER STATION
BOOSTER PUMP
MAIN LINE
ZONE DIVISION LINE
HEADER LINE 3" PVC
FLUSH LINE 2" PVC
SYSTEM CAPABILITIESEURODRIP 0.875 - 15 MILLATERAL SPACING: 80"DESIGN ET: 0.29" / ACRE / 10 HOURSFIELD SCHEDULING: 10 HOURS / ZONE
H
H
John ProgressACRES: 10.0GPM: 80ZONES: 1
NScale
1" = 200'
44 Tapes10 Acres132 gpm
99.5100
99.5 100
44 Tapes5.0 Acres66 gpm
99.5
99.5
100
100
44 Tapes5.0 Acres66 gpm
H
.29-.23 x 100 = 25% .24
.29-.27 x 100 = 7.1% .28
.29-.27 x 100 = 7.1% .28
1485'
742.5' 742.5'
294'
294'
Emitter Discharge Variation
Emitter Discharge Variation Emitter Discharge Variation
Emitter Discharge VariationThe greatest emitter discharge minus the smallest emitterdischarge divided by the average emitter discharge,multiplied by 100, within the block.
Must be less than 20 %
F
F
8/13/2019 Micro Irrigation Design Method
45/63
Flushing
MethodManual
ManifoldSizefriction loss through manifold and valves
Frequency
8/13/2019 Micro Irrigation Design Method
46/63
8/13/2019 Micro Irrigation Design Method
47/63
Main line design
Sizesystem flow ratepressure loss
Fil
8/13/2019 Micro Irrigation Design Method
48/63
Filters
shall be provided at the system inlet. Under cleanconditions, filters shall be designed for a head loss of5 psi or less.
shall be sized to prevent the passage of solids in
sizes or quantities that might obstruct the emitteropenings.
shall be designed to remove solids equal to or largerthan one-fourth the emitter opening diameter, or the
emitter manufacturer's recommendations, whicheveris more stringent
8/13/2019 Micro Irrigation Design Method
49/63
shall provide sufficient filtering capacity so thatbackwash time does not exceed 10% of the systemoperation time. Within this 10% time period, thepressure loss across the filter shall remain within themanufacturer's specification and not causeunacceptable EU.
Filter/strainer systems designed for continuous
flushing shall not have backwash rates exceeding1.0% of the system flow rate or exceeding themanufacturer's specified operational head loss acrossthe filter.
8/13/2019 Micro Irrigation Design Method
50/63
8/13/2019 Micro Irrigation Design Method
51/63
8/13/2019 Micro Irrigation Design Method
52/63
Sand Media filter
8/13/2019 Micro Irrigation Design Method
53/63
Screen filters
8/13/2019 Micro Irrigation Design Method
54/63
Filter
summary
Chemigation
8/13/2019 Micro Irrigation Design Method
55/63
Chemigation.System EU shall not be less than 85 percent.
Injectors and other automatic operatingequipment shall be located adjacent to thepump and power unit, and include integratedback flow prevention protection.
Shall be accomplished in the minimum lengthof time needed to deliver the chemicals andflush the pipelines.
8/13/2019 Micro Irrigation Design Method
56/63
Select an Injection System
Fertilizer Acid ( change ph, help against rootintrusion and clogging)Chlorine ( prevent biological clogging)Other water amendmentsPesticidesNeed safety devices ( State regulations)
Injectors
8/13/2019 Micro Irrigation Design Method
57/63
Injectors
8/13/2019 Micro Irrigation Design Method
58/63
Storage tanks
8/13/2019 Micro Irrigation Design Method
59/63
Pump Design
Calculate TDHSize Pump
8/13/2019 Micro Irrigation Design Method
60/63
Miscellaneous
Automatic controlsPressure regulators
Air vents/valves
Summary
8/13/2019 Micro Irrigation Design Method
61/63
SummaryDetermine Plant information
Spacing row/plantWater requirementIrrigation frequency
Test water quality
Select emitter/sprayerTypeSpacingDischarge
Emitter factors C v, K, xDesign Lateral normal/flushingsizeFlow ratePressure requirement
f
8/13/2019 Micro Irrigation Design Method
62/63
Design Manifold Header-Flushing/SubunitssizeFlow ratePressure requirementEmissions uniformity
Air valvesDesign Mainline
sizeFlow ratePressure requirement
Select Filter systemNumber/sizeFlushing - disposalPressure requirement
8/13/2019 Micro Irrigation Design Method
63/63
Select injection systemType
SizeSafety considerations/featuresControls
Pump stationFlow ratepressure