Chapter 11: Sprinkle Irrigation - NRCS Irrigation ToolBox Home Page

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1, Location field C-22, observer JLM, date 9-30- 75 2. Crop Tomatoes, root zone depth 4.0 ft, MAD 50%, MAD 4.4 in - 3. Soil: texture clay loam, available moisture 2.2 inlft, SMD 4.4 in 4. Sprinkler: makeRain Bird, model 29B, nozzles 5/32 by in - - 5. Sprinkler spacing 30 by 50 ft, irrigation duration 23.5 hr 6. Rated sprinkler discharge 4.4 gpm at 40 psi giving 0.28 inlhr . 7. Lateral: diameter 2 in, slope 1 '/z %, - riser height 18 in 8. Actual sprinkler pressure and discharge rate: Sprinkler location number on test lateral 1 4 5 6 10 15 end Initial pressure (psi) 45 40 40 40 - 39 40 -- Final pressure (psi) 45 40 39 40 Catch volume (gal) 1.0 -- 1.0 * 1.0 1.0 1.0 Catch time (min or sec) -- Discharge (gpm) 4.8 4.6 4.6 4.6 4.6 9. Wind: Direction relative to Part 10: Speed (mph): 10. Container grid test data in units of ml, volumeldepth200 mllin - Container grid spacing 10 by 10 ft -- Test: start 2.55pm, stop 4:30pm, duration 1 hr 35 min = 1.58 hr initial L , dung , final initial 2+ , during 55 , final 5f - rnl - iph 11. Evaporation container: initial 2.15 final 2.10 loss 0.05 in - - 12. Sprinkler pressures: max 45 psi; rnin 39 psi, ave 40 psi - - 13. Comments: Test duration was too short. Depths caught measured in 1000-mlgraduated cylinder. Wind velocities are less than normal. Figure 11-24-Sprinkler-lateral irrigation evaluation.
LATERAL SET A L 50 FEET LATERAL SET J -- 0 10 0.21 0 24 0.28 " wind drift may be excessive and the sprinklers may Figure 11-25.-Combined catch pattern in inch per hour between sprinklers 5 and 6 for a 50-ft lateral spacing. turn erratically. Therefore, for such high pressure operation, pressure control devices should be used of f 1 to 2 percent, In addition, the normal variaat the base of the sprinklers. When flexible orifice nozzles are used, the DU tion of the uniformity values can be approximated and CU test values should be multiplied by approxiby: mately 0.95 to obtain the system uniformities. When they are not used, the pressure variations kC0.2 (100- CU)]%; or +[0.2 (100- DU)]% throughout the system cause the overall uniformity of the system to be lower than the uniformity in the Nozzle discharge varies with the nozzle pressure test area. An estimate of the system DU and CU unless special flexible orifice nozzles are used to can be computed from the maximum, minimum, control the flow. Figure 11-26 shows the relation- and average system pressures by: ship between discharge and pressure for a typical fixed 5132-in nozzle that gives 5 gpm at 48 psi and System DU = DU X (1 -- - pn ) (11-lla) for a flexible orifice nozzle designed to give 5 gpm, 5 pa regardless of pressure. Unfortunately, it is difficult to manufacture the flexible orifice nozzles precisely, and and they are apt to have up to 45 percent variation px - pn ) (11-llb) in flow even with uniform pressures. The same System CU = CU X (1 - variation is also typical for almost all the flow or pressure control devices that can be used at the where base of each sprinkler. Therefore, unless the difference in pressures throughout the system is ex- P, = the maximum sprinkler pressure (psi) pected to exceed 25 percent of the desired average P, = the minimum sprinkler pressure (psi) operating pressure, it is best to use standard fixed Pa = the average sprinkler pressure (psi) nozzles and no flow-control devices. The flexible orifice nozzles maintain constant flow Using the data from figure 11-24, part 12 with without causing a pressure drop of at least 10 to 15 the test DU =: 82%: psi, which is typical of the flow or pressure control devices used at the base of sprinklers. This is an System DU = 82 X (1 - 45 - 39) = 80% 5 X 40 important advantage when operating pressures are lower than 50 psi and maintaining a reasonably and with the test CU = 87%: high nozzle pressure is necessary to have adequate jet breakup and range of throw. However, when System CU = 87 X (1- 45, -, 39 1 = 85% pressures are above 80 psi, the jet breakup and 8 X 40 7 - STANDARD 5/32'" NOZZLE 0.21 0.03 - - - FLEXIBLE * 5 OPM 0.31 0 24 0.24 0 28 (0 03) (0 051 (0 02) (0 02) 10 02) I w rr 0.11 0 21 0 26 0.31' P I - Y1 J 0 31 0.16 001 -- I x - - - - - w 5 i LL vb I 0 31 0 27 0.22 0 26 0.31 1 I 9 (0.05) 10.011 (0 04) (0001 10 05) PRESSURE AT EIASE OF SPRINKLER 0 10 0.16 0.22 0.32 0 15 0.04 - - - - 1 1 0 20 30 40 50 60 70 80 90 100 110 120 130 0.25 o 20 0.22 032 63 s5 Figure Il-26.-Comparison of pressure versus discharge rela- (0.05) (o 01) (o 06) (0.04) 10 06) tionship for a standard fixed nozzle and a special flexible orifice nozzle. ( DEVIATION FROM AVERAGE 8 pa PSI
Page 1 and 2: United States Department of Agricul
Page 3 and 4: Application intensity .............
Page 5 and 6: Advantages Some of the most importa
Page 7 and 8: End-Tow Lateral An end-tow lateral
Page 9 and 10: Figure 11-4.-Solid-set sprinkler la
Page 11 and 12: or for dual cropping, it is practic
Page 13 and 14: Planning Concepts A complete farm s
Page 15 and 16: I. Crop (Type) (a) Root depth (ft)
Page 17 and 18: Sample calculation 11-1,-Computing
Page 19 and 20: 11-rfi Such systems are capable of
Page 21 and 22: Table 11-2. Effective crop root dep
Page 23 and 24: Impact sprinklers produce a circula
Page 25 and 26: n n = mean depth of observations (i
Page 27 and 28: 11-24 I. Increases of 20 to 40 perc
Page 29 and 30: plants is similar for all systems.
Page 31 and 32: 1. At the lower side of the specifi
Page 33: diameter based on average wind spee
Page 37 and 38: such as forage crops, According to
Page 39 and 40: Table 11-10.-A guide to recommended
Page 41 and 42: Table 1 l-12.-A guide to recommende
Page 43 and 44: I. Crop (type) (a) Root depth (ft)
Page 45 and 46: F F I k% TabIe 11-13.-Nozzie discha
Page 47 and 48: 1‘ HOSE-LINE ’ A-Fully portable
Page 49 and 50: A-Layout on moderate, unifbrm Slope
Page 51 and 52: such cases, lines are laid on the c
Page 53 and 54: .I* en factor (F) based on the numb
Page 55 and 56: Figure Il-33.-lateral laid downhill
Page 57 and 58: This is obviously outside the 20 pe
Page 59 and 60: Table 11-17.-Typical as % 3 -. " 3
Page 61 and 62: Table 11-19a.-Friction-loas J value
Page 63: one of selecting mainline pipe size
Page 66 and 67: ft; for D3 and Dz, friction loss in
Page 68 and 69: The standard capital recovery facto
Page 70 and 71: Step 4.-The WHP savings needed to o
Page 72 and 73: 1. Economic method-Selection of the
Page 74 and 75: Table Il-24.-Comparison of total an
Page 76 and 77: ial, and then determine the total a
Page 78: Table 11-28.-Values of resistance c
Page 82 and 83: can be solved very simply from equa
Page 84 and 85:
sure is representative of the entir
Page 86 and 87:
turer at the given pressure. This o
Page 88 and 89:
Table 11-30.-Typical discharges and
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This allows for a 1-hr set time, 20
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ftlmin. The required sprinkler disc
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R *= maximum radius irrigated when
Page 96 and 97:
sprinkler pattern. High instantaneo
Page 98 and 99:
Where soil sealing and infiltration
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Thus, to compute the (Hfk, with two
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And the net depth of application as
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Machine Selection Ultimately the ty
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Span I Container Span Position Weig
Page 108 and 109:
Sample calculation 11-20.-Using fie
Page 110 and 111:
Span Container span No. Position We
Page 112 and 113:
4. Increasing system pressure and r
Page 114 and 115:
Figure 11-60.-A method for adding f
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Table Il-35.-Steps for estimating f
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Frost Control Operation For complet
Page 120 and 121:
Installation and Operation of Sprin
Page 122 and 123:
T actual operating time (hrlday) t
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