irrigation cost analysis

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Irrigation CostAnalysis Handbook

Agricultural Extension ServiceThe University of Tennessee

PB1721


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Table of Contents

Introduction 3

Scope and Purpose of Handbook 3

Using This Handbook 3

Steps for Completing the General Information Sheet 4

Estimation of Power Requirement 6

Steps for Completing the Initial Investment and Depreciation Form 7

Steps for Completing the Annual Operating Cost Form 9

Steps for Completing the Return on Investment Form 10

Steps for Completing the Annual Cash Flow Analysis 11

Irrigation Cost Analysis Forms 12

Friction Loss Table for Class 160 U. S. PVC Plastic Pipe 21

Friction Loss Table for Class 200 U. S. PVC Plastic Pipe 22

Friction Loss Table for Portable Aluminum Pipe with Couplings 23


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IntroductionIrrigation is a risk management tool.

The risk of yield reduction due to drought isminimized with irrigation, because moisturecan be added to the soil to match the waterrequirements of the crop. Irrigation is also amajor capital investment. The yield producedunder irrigation must be sufcient to producea positive return on the investment.

This handbook is intended to assist usersin determining the economics of investingin irrigation at their location. All irrigationsystems are unique. Many factors are usedto estimate the cost of irrigation, and each of

these factors will vary with location. Issuessuch as the selection of pumps, pipes andpower are dependent upon the characteristicsof the site and cannot be generalized. Thisguide allows the user to approximate pumppower requirements and pipe diameters sothat realistic prices can be obtained fromirrigation suppliers.

Scope and Purpose of HandbookThe anticipated user of this handbook is

someone who is considering the purchase of

an irrigation system. This document is a toolthat can be used to assist in understandinghow irrigation will affect the overall protabil-ity of the farming operation. This documentis not an irrigation design manual the actualsystem design must be completed by a quali-ed irrigation engineer.

The primary focus of this handbook isthe economics of sprinkler irrigation over

agronomic crops grown in Tennessee.Economic analysis of high-value crops (suchas tobacco and sod) with sprinkler irrigationcan also be studied using the methodologyprescribed by this handbook. While otherstyles of irrigation, such as surface irrigationor drip irrigation, can be evaluated throughthe use of this handbook, the user needs to bevery familiar with the unique aspects of theseirrigation methods to do a complete economicanalysis.

This handbook includes assumptionsthat aid in simplifying the economic analysis.The inclusion of all design variables used for

irrigation would require that the system bedesigned before economic analyses could becompleted. These simplifying assumptionsshould not signicantly affect the results ofthe economics.

The secondary purpose of this handbookis to serve as a communications tool betweenthe agricultural producer and an irrigationengineer. This handbook demands thatinformation be collected concerning thelayout and operation of the farm. Havingthis information collected and organized will

speed the design process and increase thelikelihood that the producer will receive thebest design for his/her location.

Using This HandbookThis handbook contains a methodical se-

ries of questions to be answered by the user.The answers to these questions are to be writ-ten on a set of forms that are included in this

John R. BuchananAssistant Professor

Biosystems Engineering & Environmental ScienceTim L. Cross

Professor & Assistant DeanTennessee Agricultural Extension Service

Irrigation Cost Analysis

Handbook


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handbook. An electronic spreadsheet versionof these forms is available for rapid assess-ment of the economics. The text provides as-sistance and guidance for answering each ofthe questions. Your local county AgriculturalExtension agent or a farm management areaspecialist can provide assistance with inter-preting the results of this analysis.

The rst set of questions (lines 1-18)are related to the unique aspects of the eldand crop to be irrigated. Lines 19-21 providea process to estimate the ow rate, pipediameter and pump power requirement. Theinitial expense of purchasing equipmentis approximated by lines 22-38. Annualoperating costs are computed by lines 39-46. Lines 47-52 provide information aboutestimating the return on the irrigation

investment and lines 53-60 analyze the cashow of using irrigation.

Steps for Completing the

General Information Sheet

The general information sheet provides forthe input of information about the farm andeld to be irrigated. Answers are requiredfor each question to complete the economicanalysis.

1. Crop to Be Irrigated.Most elds are put through a rotation ofcrops, so an irrigation system must beable to supply different crop needs. Forthe purpose of doing the preliminarydesign work, select the crop with thehighest water demand. As differentcrops are analyzed for economic return,adjust labor costs, number of irrigationapplications and energy consumption for

each crop, while holding constant the sizeof the equipment, pressure and owrate.

2. Expected Average Increase in Yield PerAcre from Irrigation.Remember that irrigation does notincrease yields it provides the ideal soilmoisture for the crop to grow to its fullpotential. There must also be enough

nutrients in the soil to support the fullcrop potential. Having said that, somecommonly used values for increased yieldin elds with irrigation include:

Cotton 180 to 400 additional poundsper acre of lint

Corn 40 to 50 additional bushelsper acre

Soybeans 15 to 25 additional bushelsper acre

3. Value of Crop Per Unit.Obtain this value from current marketprices and try to anticipate the futureprice.

4. Maximum Soil Water-Intake-Rate.This question is really asking for theinltration capacity of the soil. Surfaceponding and runoff will occur when wateris applied at a rate greater than the abilityof the soil to pull the moisture throughthe surface. The soil survey manual foryour county has information about thepermeability of each soil type. This valueis related to the inltration capacity;however, this value does not considersurface effects such as crusting and crop

litter. Inltration rate can be measured;however, most irrigation-designers willuse approximated inltration rates basedon soil texture.

Light, sandy soils 0.5 to 0.75 inchper hour

Medium-textured 0.25 to 0.5 inchsoils per hour

Heavy-textured 0.1 to 0.25 inchsoils per hour

5. Seasonal Water Consumption by theCrop (inches).Consumptive-use is the total volumeof water that leaves the soil during thegrowing season. Remember that 1 inchof water over one acre of land is 27,156gallons. Some commonly used values forconsumptive use include:


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Cotton 25 to 35 inches

Corn 25 to 30 inches

Soybeans 20 to 25 inches

6. Peak-use Demand Rate of Crop.This number represents the maximumrate that water will leave the soil. It is atthis period of time that the most water isbeing consumed by the crop. This valueis the primary parameter for designingan irrigation system. Water must be putback into the soil at the same rate atwhich it was withdrawn to maintain thesoil-moisture supply. Typical values forTennessee row crops include:

Cotton 0.30 to 0.36 inch per day

Corn 0.30 to 0.35 inch per day

Soybeans 0.20 to 0.30 inch per day

7. Provide a Map with the Dimensions ofthe Field.With the explosion of GPS/GIStechnologies, producing excellent mapsofelds to be irrigated is getting muchless expensive. The acreage and shapeof the eld are needed to design thelayout of the hydraulic network and to

decide which type of system is mostefcient. Documenting the elevationchanges across a eld is very importantif surface irrigation is to be used. If asprinkler system is chosen, then elevationinformation does not have to be as exact;however, it is still needed so the designercan develop a system that will provide auniform application of water.

At minimum, a scaled aerial photographis needed. These maps can be copied

from the local Farm Service Agencyofce. It is important that these mapsbe photocopied at the same scale asthe original aerial photograph. Severalsheets may need to be taped togetherwhen photocopying larger elds. Pleasenote the scale on the aerial photographs.Typical scales are 1000 feet per inchand 660 feet per inch.

8. Number of Acres in the Field.This value should be determined frominformation collected in question 7.

9. Number of Acres to Be Irrigated.Often, the irrigation system does notcover the whole eld. The economics ofirrigation must be based on the acreagethat is actually irrigated.

Traveling guns, solid-set, hand-moveand subsurface drip systems are capableof irrigating irregularly shaped elds.Center pivots irrigate a large circle withina eld. Cornering systems are availableon center pivots and they can ll in thecorners of a square eld. The extent towhich a surface system can cover a eld

is dependent on the topography.

10. Number of Irrigations Expected perSeason.This number depends on the rainfallpattern during the growing season. Sometypical values based on fairly normalyears include:

Cotton 7 irrigation events

Corn 6 irrigation events

Soybeans 5 irrigation events

11. Type of System.This will be answered by evaluating thesketch of the eld and determining whichtype of system will best t this land.

12. Source of Water.Will the water come from surface water orgroundwater? Is there an existing well?Does the area have a good history ofproducing good wells? Is there access to a

nearby river, lake or canal?

13. Length of Mainline.What is the length of pipe that will berequired to transfer water between thesource and the distribution system? Inother words, what is the furthest distancethat water will have to be pumped beforeit reaches the irrigation system?


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14. Total Height That Water Is toBe Lifted (Feet).This is the total elevation difference fromthe water level of the source to the tallestsprinkler in the highest part of the eld.If pulling water from a surface source,the elevation of water surface shouldbe taken when the water body is at thelowest stage. If groundwater is the source,then the elevation needs to be calculatedfrom the elevation of the drawdowncurve. Local drilling contractors may beable to provide assistance in obtainingthis elevation.

The total elevation difference that wateris pumped is called the static head. Thepump must produce at least this much

pressure before any water is produced atthe upper end of the pipeline.

15. Energy Source of Power Unit.This decision is based on the availabilityof the fuel or power, and the total annualcost of using that fuel or power.

16. Current Interest Rate.

17. Stand-by Charges for Electricity orDemand Charge for Electricity.This only applies for producers who willbe drawing electricity from the utilitylines. Often, utilities will charge irrigatorsextra fees to maintain the high-capacitytransmission lines to rural areas. Manyareas will give a discount on this fee ifthe utility can cut-off the power to theirrigation system if the demand on therest of the system becomes too high.

18. Hours of Labor per Acre of Irrigationper Event.For the purpose of estimating cost, Table1 offers some guidance on the laborrequired to operate various types ofirrigation equipment.

Estimation of Power Requirement

The cost of moving water is the mostsignicant component of the annual operat-ing cost. A reasonable estimate of the powerrequirement is necessary in order to approxi-mate the cost of energy. The Estimation of

Table 1. Labor Requirements by Type of Irrigation System1

Type of System Estimates of Labor

Required(hrs per acre

per event)

Type of System Estimates of Labor

Required(hrs per acre

per event)

Sprinkler Irrigation System Surface Irrigation System

Permanent solid set

Hand-move portable set

Side wheel roll

Center pivotLateral move

Hand-move big gun

Traveling gun

(soft or hard hose system)

0.1 to 1

1 to 2

1 to 3

0.1 to 0.50.1 to 0.5

1 to 2

0.5 to 1.5

Border

Flood

Furrow

Subsurface Drip System

Dripperline

0.5 to 1

0.5 to 0.1

0.5 to 1.5

0.06 to 0.08

1Turner, J. H., C. L. Anderson. (1980). Planning for an Irrigation System. Am Assoc. for

Vocational Instructional Materials, Athens, GA.


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Power Requirement Form is a stand-alonedocument that guides the user through aseries of simple calculations estimating thehorsepower needed to move water from thesource through the irrigation distributionsystem. Lines 19 - 21 assist with the determi-nation of the pump ow rate, pipe diameter,system pressure and the required power (seepages 13 - 15).

Steps for Completing

the Initial Investment

and Depreciation Form

Lines 22 - 30 provide an opportunity forthe user to customize and determine thetotal investment by entering the price of thevarious components needed in an irrigationsystem. Additionally, by using straight linedepreciation, the user can estimate the annualcost of wear and tear to the equipment. Lines31 - 38 provide for the computation of annualcash and non-cash expenses.

22. WellIn West Tennessee, drilling a high-production well is expensive anduncertain. The common dollar amount for

drilling is $30,000 for a 12-inch diameter,200-feet deep, 1000-gallon per-minutewell. This includes the casing but doesnot include the pump. Contact a localdriller and they will be able to give you anestimate based on location and owraterequired. Most areas in Middle and EastTennessee do not have high-productionaquifers, thus the use of wells is rare.

23. Reservoir PumpThis is the cost of the pump either from

a groundwater or surface water source. Ingeneral, you can assume that if the pumphead is submerged, the pump is a turbine.If the pump is setting next to the watersource, it is a centrifugal. The owrate andpressure was calculated in the GeneralInformation Sheet. With these two piecesof information, estimates of pump pricescan be obtained from dealers.

24. Power UnitThis represents the cost of providingpower to the pump. Pumps are generallypowered in one of three different ways:1) a stationary engine with the pumpmounted directly on the engine, 2) tractoror station engine with the pump beingdriven through a drive-shaft, or 3) anelectric motor coupled to the pump. Wellpumps are connected to engines via aright-angle drive, while electric motorsare mounted vertically over the well. Forthe purpose of this analysis, the cost ofthe right-angle drive needs to be includedwith the cost of the power unit.

Brake-hp was calculated in the Estimatefor Power Requirement Form and

this value can be used to obtain a costestimate for a motor or engine with thiscapability. If the power unit is also goingto be used to generate electricity forthe drive-towers of a center pivot, thencontact a pivot supplier to get an estimatefor the extra horsepower required.Even if the pump is pto-driven by anexisting tractor, there is a real cost in theaccelerated depreciation of the tractor.

25. Miscellaneous

If an electric motor is selected, there arecosts associated with conducting powerfrom the main transmission line to thelocation of the pump. The electric utilitywill charge the cost of installing the poles,wires and disconnects to the propertyowner. Consult with the local electricutility to get an estimate for these costs.The utility will need the horsepowerrequirement of the pump and how farthe pump is located from existing powerlines.

Fuel tanks and fuel lines may be needed.The prices of these can be found at a localdealer.

If using surface irrigation, equipmentsuch as land planes, ditchers, middle-busters, etc. may be needed to work thesoil surface.


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26. Water PipeAn approximate pipe diameter andpressure requirement have beencalculated in the Estimation of PowerRequirement form. Generally speaking,if the mainline is above ground, it willbe coupled aluminum; if it is buried, itwill be slip-joint PVC. Aluminum hasthe advantage of having resell value.Once PVC is buried, it would be cost-prohibitive to recover and resell. PVC hasthe advantage of being out-of-harms-wayand has less friction loss to overcome. Aper-foot cost from either material can beobtained from a pipe dealer. Include anadditional $2 per foot as an estimation forinstallation cost.

27. Pipe TrailerIf coupled-aluminum is purchased, thena pipe trailer is needed for moving andstoring pipe. Pipe trailers can purchasednew, used or can be shop-made.

28. Sprinkler SystemsIf a sprinkler system is going to beemployed, select the type of system andenter a cost. A dealer can provide anestimate of the cost based on the type ofsystem and the acreage to be covered.

29. Surface SystemA surface-irrigated eld must be veryat to permit the uniform distribution ofwater and to allow for drainage to preventooding. The only way to get a goodapproximation of the cost of land gradingis to have a good topographic survey ofthe eld and let a grading contractorestimate the land leveling required.A district conservationist from theNatural Resources Conservation Service

(NRCS) may be able to provide some costestimates for land shaping.If the land is already leveled, surfaceirrigation generally has the leastexpensive initial cost. Surface irrigationpumps are usually high-ow, low-head.These pumps are capable of rapidlymoving a tremendous volume of water,

but not against any pressure. Dependingon where the water source is locatedrelative to the eld, an inexpensivedistribution pipe (polypipe) can be usedto spread the water across the eld. Vinylpolypipe cannot be used to move wateruphill, so must be placed on level ground.

Flood gates and water controls are usedto maintain a certain depth of water in aeld, and/or control the outfall to reduceerosion. Often these devices are madelocally out of pressure-treated timbers.

30. Subsurface Drip Irrigation (SDI)This technology is not common inTennessee. It is a proven and benecialmethod of applying supplemental water

to a row crop. However, with SDI, manyof the traditional methods of cultivating acrop will need to be modied. Dripperlineis placed 8 to 12 inches below the surfaceand is spaced about every other row.Obviously, deep tillage is no longer anoption for that eld. There are reports ofdripperlines that have been in place formore than 20 years that are still beingused.

The major initial costs for SDI include the

dripperline, lters, mainline and pump.SDI is a low-pressure technology, so thecost of energy is greatly reduced. High-quality ltration is needed to prevent theemitters from being plugged by sedimentand algae. If groundwater is used, theiron in the water can form precipitantsthat can block emitters. The iron can beremoved by oxidation.

The cost of a SDI system can beestimated by a dealer. However, it is

important to remember that this methodmay require different tillage equipmentand that adds to the cost of installing thesystem.

31. Total Investment (initial cost)Sum all the gures in the initial costcolumn. This is an estimate of the


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up-front money required to install anirrigation system.

32. Total Annual Depreciation CostSum all the gures in the annual costcolumn. This will be an estimate of theloss of value due to wear and tear on theequipment.

33. InterestThis is the total investment multipliedby the decimal form of the interestrate. Even if money is not borrowed,this represents the opportunity costs ofconverting liquid assets into equipment.

34. Total Annual Noncash Fixed CostThis is the sum of Line 32 and Line 33.

35. Taxes and InsuranceTaxes and insurance are estimated bymultiplying the total investment by 0.02(2 percent of total investment).

36. Stand-by or Demand Chargesfor ElectricityStand-by or demand charges only applyif electricity is going to be used. Thesevalues will have to be obtained from theelectrical utility.

37. Loss of Income Due to Acreage Out ofProductionAn irrigation system may force someland to be taken out of production (accessroads, drainage areas, equipment storage

areas). This is computed by multiplyingthe dryland yield (typical yield withoutirrigation) by the unit value of the yield(Line 3) and multiplying this product bythe number of acres lost.

38. Total Annual Cash Fixed CostThe total annual cash xed cost is thesum of Line 35 through Line 37.

Steps for Completing the Annual

Operating Cost Form

The previous section computed theannual xed costs of the irrigation system.These expenses occur whether the system isoperating or left idle in the eld. This section

estimates the costs of operating the system.The purchase of energy is the most signicantannual component of irrigating. Otherannual costs for operating the system includemaintenance and labor.

39. FuelFuel or electricity power consumption isa function of horsepower and length ofoperation. It is common to use an indexvalue for each energy source. Table 2 isa collection of these index values. Thesevalues include the efciency by which thefuel is converted to useful work. Multiplythe brake-hp by the number of hours ofoperation and by the cost per unit of fuel.Take this product and divide it by theindex value for the selected fuel type.

Table 2. Annual Fuel Consumption2

Fuel or Power Ef ciency of Motor or Engine Bhp-hours per Unit of Fuel

Electric 80 1.07 per Kw-HourGasoline 20 9.74 per gallon

Diesel 26 14.3 per gallon

Propane/Butane 21 7.77 per gallon

Natural Gas 21 8.2 per 100 cubic feet

2Longenbaugh, R. A. and H. R. Duke. (1981). Farm pumps. In Design and Operation of FarmIrrigation Systems, M. E. Jenson, Editor. ASAE, St. Joseph, MI.


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40. Engine OilThe standard method of estimating thecost of engine lubrication is to multiplythe fuel cost by 0.15 (15 percent of fuelcost).

41. Repair and Maintenance (power unit)Estimation of the cost for repair andmaintenance is based on a percentage ofthe initial cost of the energy source.

42. Repair and Maintenance(irrigation equipment)The annual cost of repair andmaintenance of the irrigation system isapproximated as 5 percent of the totalinitial system cost.

43. Reservoir and Field MaintenanceThe annual cost of maintenance of thewater reservoir and eld is approximatedas one-half percent of the total initial costof the developing the reservoir and/orshaping the eld for the irrigation system.Such cost might include permit fees towithdraw water from a surface source,removing trash from the pump intakeand re-forming drainage ditches after aheavy rain event.

44. Additional Seed, Fertilizer, Chemicalsand Harvesting CostsIrrigation allows the crop to growwithout being limited by soil moisture.To get the maximum productivity,sufcient nutrients, additional pesticidesand increased harvesting capacity maybe needed.

45. LaborLine 18 on the General Information Sheetallows for the estimation of the number of

hours of labor required per acre. Take thisnumber and multiply it by the number ofirrigation events per season (Line 10), thenumber of irrigated acres (Line 9) and thedollar-per-hour cost of labor.

46. Total Annual Operating CostThis is the sum total of lines 39 through45. This value represents the annual cash-

ow expense of operating the irrigationsystem.

Steps for Completing the

Return on Investment Form

This section computes the paybackperiod and the return on investment. Mostof the lines on this form have already beencalculated. Guidance is given as to thelocation of these values. To simplify thecalculation, the user is asked to transfer thepreviously calculated values and use them inthe given equation.

47. Expected Average Increase in Revenuefrom Irrigation

Multiply the per unit increase in yieldfrom Line 2 and by the dollar value perunit (Line 3) and the irrigated acres (Line9). This is the annual increase in revenuedue to increased crop yield.

48. Total Annual Operating Costfor IrrigationThis value is from Line 46 on the AnnualOperating Cost Form.

49. Total Annual Fixed Cost

Sum Lines 34 and 38 on the InitialInvestment and Depreciation Cost Form.

50. Total InvestmentTransfer this value from Line 31 on theInitial Investment and Depreciation CostForm.

51. Payback PeriodThis is a simplied calculation procedure.This calculation ignores interest expense

and is a before-tax analysis. With thedepreciation, there should be additionaltax benets.

The total investment (Line 50) is dividedby the sum of the increase in revenue(Line 47), minus the annual cash xedcost (Line 49), minus annual operatingexpense (Line 48).


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52. Return on InvestmentThe sum of the total annual cash xedcost (Line 49) and the total annualoperating cost (Line 48) is subtractedfrom the increase in revenue (Line47). This value is divided by the totalinvestment (Line 50).

Steps for Completing theAnnual Cash Flow Analysis

53. Percent of Total Investment FinancedIf money is borrowed to purchaseirrigation equipment, this is the percentof the total investment that will benanced.

54. Loan Term, Years

Number of years to pay back loan.

55. Annual Principal and Interest PaymentBased on the number of compounding

periods (12 per year) and the interest rate,the formula for the annual payment is givenon the form.

56. Expected Average Increase in RevenueFrom Line 47 on the Return on InvestmentForm.

57. Total Annual Operation CostFrom Line 46 on the Annual Operating CostForm.

58. Principal and Interest PaymentFrom Line 55 on the Annual Cash FlowAnalysis Form.

59. Total Annual Cash Fixed CostFrom Line 38 from the Initial Investment

and Depreciation Cost.

60. Annual Net Cash FlowAnnual increase in revenue minus theannual cash costs (Line 56 minus Line 57minus Line 58 minus Line 59).


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Irrigation Cost Analysis Forms

General Information Sheet

Name: _________________________________ Farm or Field Name: _______________________

County: _______________________________

1. Crop to be irrigated. _________________

2. Expected average increase in yield per acre from irrigation. _________________

3. Value of crop per unit ($/bu or $/lb). _________________

4. Maximum soil water intake rate. _________________

5. Seasonal water consumption by the crop (inches). _________________

6. Peak-use demand rate of the crop. _________________

7. Provide a map with the dimensions of the eld. _________________

8. Number of acres in the eld. _________________

9. Number of acres to be irrigated. _________________

10. Number of irrigations expected per season. _________________

11. Type of system. _________________

12. Source of water. _________________

13. Length of mainline. _________________

14. Total height that water is to be lifted (feet). _________________

15. Energy source of power unit. _________________

16. Current interest rate. _________________

17. Stand-by charges for electricity or demand-charge for electricity. _________________

18. Hours of labor per acre per irrigation event. _________________


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Estimation of Power Requirement Form

19. Flow rate of pump.

For the purpose of this analysis, a ballpark estimate ofow rate is needed. The procedurelisted below provides a rough estimate. Flow rate is computed by the following formula, which

includes the number of acres irrigated, the hours per day allowed for irrigation, the number ofdays required to cover the eld, the depth of water to be applied and the efciency of the waterapplication.

19-a) Number of hours of operation per irrigation event _______________________

Table 3 can be used to approximate the number of hours required per irrigation. Thistable is only a guide. Actual times will vary with soil moisture conditions and inltrationrates.

Table 3. Estimates of hours of operation per irrigation event.1

Irrigation method Typical number of hours Notes

Center pivots 60 hours assumes that a full circle is being irrigated

Traveling guns 96 hours assumes 16 hours per day and six days

Surface irrigation 48 hours

Subsurface dripirrigation 48 hours

Hand-moved 100 hours

Permanent solid set 48 hours1Center pivots can operate with a minimal amount of supervision, while traveling guns need almost constant

attention. Other considerations include whether disease problems will occur if the crop is irrigated at night. The

maximum number of hours per day should be limited to 23 to allow for maintenance of the system.

19-b) Depth of water applied (inch) _________________________

Unless better information is available, assume 1 inch is going to be applied during eachirrigation event.

19-c) Acres irrigated (Line 9) _________________________

19-d) Application efciency _________________________

Common application efciencies include:0.95 for subsurface drip0.85 for center pivots, linear moves, wheel-roll and solid set0.70 for traveling guns0.40 for surface-ood0.30 for furrow irrigation


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19e Determination ofow Rate Chart

Insert the above numbers into the ow rate equation.

owrate =volume

=depth applied (in) acres irrigated 453

= gpmtime (hours per irrigation) decimal efciency

gpm =( ) in ( ) acres 453

= __________

( ) hrs ( ) efciency

For example: If 1 inch is to be applied, the system runs for 16 hours per day, it takes3 days to cover the 60-acre eld, and the application efciency is 80 percent (0.80), thenthe minimum pumping rate is 708 gallons per minute (gpm). The 453 is a unitconversion constant.

20. Determine the pressure required by the pump

20-a) Determine the pipe diameter _________________________

An estimate of the diameter of the mainline is required. The goal is to size the pipe tokeep the velocity of water inside the pipe at approximately 5 feet per second (fps). Pipetables are included in this handbook. Use the tables to nd the pipe diameter thatwill have a velocity at 5 fps at the ow rate determined in 19e. Tables for coupled-aluminum, Class 125 PVC and Schedule 40 PVC are also included in this handbook. Theselection of Class 125, Class 200 and Schedule 40 PVC depends on the pressurerequirements of the pipe. For the purpose of this economic analysis, assume Class 200PVC for buried pipe and coupled-aluminum for above-ground pipe.

For example: If the owrate is 708 gpm, from the Class 200 PVC table, a 8-inchnominal diameter pipe is required.

20-b) How many feet of mainline will be required? _________________________

From Line 13

20-c) What is the pressure drop across the mainline? _________________________

From the pipe tables, determine the psi loss per 100 feet. Take this value and multiply itby the number of 100-foot sections in the mainline.

For example: 2,200 feet of 8-inch diameter Class 200 PVC is needed to supply twotraveling guns being fed from a creek. Each traveling gun is spraying 350 gpm. Inthe table for Class 200 PVC and 700 gpm, the psi loss is 0.36 psi per 100 feet. Inthis case, the friction loss is 22 times 0.36 psi or 8.0 psi.


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20-d) Convert the static head to psi. _________________________Take the height (in feet) that water is being lifted and divide by 2.31 to get psi.

For example: Assume that there is 40 feet of elevation difference from the creek tothe top of the gun cart when the traveler is in the highest part of the eld.

40 feet divided by 2.31feet/psi equals 17.3 psi

20-e) What is the pressure required at the sprayer system? _________________________Most modern center pivots require 30 to 40 psi at the pivot. Most traveling gun systems(both hard-hose and soft-hose) require 100 to 120 psi at the reel. Wheel rolls, solid set andhand-move generally have impact-sprinklers that require 50 psi.

20-f) From 20 c-d-e, sum the pressure the pump has to work against.

Friction loss (psi) ___________________

Static head (psi) ___________________Sprayer pressure (psi) ___________________

Total head (psi) ___________________

21. Determine the brake-horsepower of the pump motor/engine

21-a) Estimate the water horsepower required to move the water.

Water horsepower is the theoretical power required to move a volume of water per unittime against a given pressure. The ow rate (gpm) is from Line 19e and the total pressure(head) is from Line 20f.

Whp =gpm total head = ( ) gpm ( ) psi = ___________

1,714.3 1,714.3

21-b) Compute the brake-horsepower.Brake-horsepower is the power required to drive the pump. It is calculated by dividing theWhp (Line 21a) by the efciency of the pump. The pump efciency is pump-specic and apump has not be selected. A value of 60 percent has been assumed for the pump efciency.The goal of the irrigation designer will be to nd a higher efciency pump.

Brake hp = (water hp) (decimal pump efciency)

Brake hp = ( ) (0.60) = __________________


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Initial Investment and Depreciation Cost Form

Use straight line depreciation

LineEstimated

Years of Life Initial Cost

Annual Cost(divide initial costby years of service)

22. Well

Casing8 and 10 gage12 gage3/16 inchconcrete

25+1525+25+

$ __________$ __________$ __________$ __________

$ __________$ __________$ __________$ __________

23. Reservoir Pump

Line shaft propeller 10 $ __________ $ __________

Turbine 20 $ __________ $ __________

Centrifugal 20 $ __________ $ __________24. Power Unit

Electrical 25 $ __________ $ __________

Gasoline 9 $ __________ $ __________

Diesel 14 $ __________ $ __________

Natural gas, LP or propane 14 $ __________ $ __________

25. Miscellaneous

Electrical disconnect 20 $ __________ $ __________

Gas lineIronPlastic

2018

$ __________$ __________

$ __________$ __________

Fuel tankPropaneDiesel or gasoline

2018

$ __________$ __________

$ __________$ __________

Land plane 15 $ __________ $ __________

26. Water Pipe

Underground pipe: (include trench cost)Concrete

Steel (waterworks class)Asbestos cementPlastic

40

404040

$ __________

$ __________$ __________$ __________

$ __________

$ __________$ __________$ __________

Above-ground pipe:AluminumGalvanized steel

1515

$ __________$ __________

$ __________$ __________

27. Pipe Trailer 10 $ __________ $ __________


17/24

17

Initial Investment and Depreciation Cost Form (cont.)

LineEstimated

Years of Life Initial Cost

Annual Cost(divide initial costby years of service)

28. Sprinkler Systems

Hand-moved (coupled aluminum pipe) 15 $ __________ $ __________Self-moved (hard-hose reel, wheel roll) 15 $ __________ $ __________

Tractor-moved (cable-tow) 10 $ __________ $ __________

Self-propelled (center pivot, linear move) 20 $ __________ $ __________

Permanent solid set 20 $ __________ $ __________

29. Surface System

Land grading 20 $ __________ $ __________

Distribution equipment

Gated aluminum 15 $ __________ $ __________

Polypipe 1 $ __________ $ __________

Flood gates and controls 5 $ __________ $ __________

30. Subsurface Drip Irrigation System

Stainless steel lters 25+ $ __________ $ __________

Manifold and valves 10 $ __________ $ __________

Dripper lines 20 $ __________ $ __________

31. Total Investment (Initial Cost) sum of left column $ __________

32. Total Annual Depreciation Cost sum of right-column, Lines 22through 30 $ __________

33. Interest total investment decimal interest rate $ __________

34. Total Annual Noncash Fixed Cost Line 32 plus Line 33 $ __________

35. Taxes and insurance total investment x 0.02 $ __________

36. Stand-by or demand charges for electricity $ __________

37. Loss of income due to acreage removedfrom production

__________ dryland yield peracre $ ________ per crop unit ______ number of acres lost $ __________

38. Total Annual Cash Fixed Cost sum Lines 35 through 37 $ __________


18/24

18

Annual Operating Cost Form

Line Total

HorsepowerRequired

Numberof HoursOperated

Cost perUnit of

Fuel

Bhp-Hrsper Unitof Fuel

39. Fuel or power _________ ________ ________ _______ $ __________

40. Lubrication 0.15 dollars spent on fuel $ __________

41. Repair andmaintenance(power unit)

Initial cost of power unit ____ 0.020 for electric0.066 for diesel0.070 for gasoline0.055 for propane0.055 natural gas $ __________

42. Repair and

maintenance(irrigationequipment)

Initial cost of irrigation equipment 0.005

$ __________ initial cost 0.005 $ __________

43. Reservoir and eld maintenance

Initial cost of developing reservoir 0.005

$ __________ initial cost 0.005 $ __________

44. Additional seed,fertilizer, chemicalsand harvesting cost

$ __________ anticipated additional expense per acre the number of acres $ __________

45. Labor __________ hours per acre per irrigation thenumber of irrigations the number of acres the $ _________ per hour. $ __________

46. Total Annual Operating Cost sum Lines 39 through 45 $ __________


19/24

19

Return on Investment Form

Line Total

47. Expected average increase in revenue

_____ increase in yield per acre (Line 2) $ _______ per unit (Line 3) _______ acres (Line 9). $ __________

48. Total Annual Operating Cost

transfer from Line 46 $ __________

49. Total Annual Fixed Cost

sum of Line 34 and Line 38 $ __________

50. Total Investment

transfer from Line 31 $ __________

51. Payback Period (years)

total investment(annual increase in revenue - (annual operating cost) - (annual cash xed cost)

__________ yrs.

52. Return on Investment

(annual increase in revenue - (annual operating cost) - (annual cash xed cost)total investment

____________%


20/24

20

Annual Cash Flow Analysis Form

Item

53. Percent of total investment nanced __________ %

54. Loan term, years __________ years

55. Annual principal and interest payment

P & I Payment =

total investment decimal percent nanced

1 - (1 + i) -n

i

where: i is the decimal interest rate

n is the number of compounding periods

56. Expected average increase in revenue from Line 47 $ ___________

57. Total annual operating cost from Line 46 $ ___________

58. Principal and interest payment from Line 47 $ ___________

59. Total annual cash xed cost from Line 47 $ ___________

60. Annual Net Cash Flow Line 56 minus Line 57 minus Line 58 minus Line 59 $ ___________


21/24

21

Friction Loss: Class 160 U. S. PVC Plastic Pipe - pressure loss in psi per 100 feet of pipe.

NominalPipe IDPipe OD

2"

2.1932.375

2-1/2"

2.6552.875

3"

3.2303.500

4"

4.1544.500

6"

6.1156.625

8"

7.9618.625

10"

9.92410.750

FlowGPM

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

10

2030405060708090

100120140160180200220240260

280300320340360380400450500550600650700750800850900

9501000110012001400160018002000

0.07

0.240.510.861.301.822.433.11

----------

-----------------

--------

0.85

1.702.553.404.255.105.956.80

----------

-----------------

--------

0.03

0.090.200.340.510.720.961.231.521.852.60

-------

-----------------

--------

0.58

1.161.742.322.903.484.064.645.225.806.96

-------

-----------------

--------

-

-0.080.130.200.280.370.470.590.711.001.331.702.12

----

-----------------

--------

-

-1.181.571.962.352.743.133.533.924.705.486.277 05

----

-----------------

--------

-

-----

0.110.140.170.210.290.390.500.620.760.901.061.23

1.411.61

---------------

--------

-

-----

1.661.892.132.372.843.323.794.264.745.215.686.16

6.637.11

---------------

--------

-

---------

0.040.060.080.090.120.140.160.19

0.220.240.280.310.340.380.420.520.630.750.881.021.171.33

---

--------

-

---------

1.311.531.751.972.192.402.622.84

3.063.283.503.723.934.154.374.925.466.016.567.107.658.20

---

--------

-

-----------------

-0.070.080.090.090.100.120.140.170.210.240.280.330.370.420.470.52

0.570.630.750.88

----

-

-----------------

-1.932.062.192.322.452.582.903.223.553.874.194.514.845.165.485.80

6.136.457.097.74

----

-

-----------------

--------

0.060.070.080.100.110.130.140.160.18

0.200.220.260.300.400.510.640.78

-

-----------------

--------

2.072.282.492.702.903.113.323.533.73

3.944.154.564.985.816.647.478.170

Friction losses calculated withthe Hazen-Williams Equation

with C = 150


22/24

22

Friction Loss: Class 200 U. S. PVC Plastic Pipe - pressure loss in psi per 100 feet of pipe.


2"

2.1492.375

2-1/2"

2.6012.875

3"

3.1663.500

4"

4.0724.500

6"

5.9936.625

8"

7.8058.625

10"

9.72810.750

FlowGPM

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

10

2030405060708090

100120140160180200220240260

280300320340360380400450500550600650700750800850900

9501000110012001400160018002000

0.07

0.260.560.951.442.012.683.43

----------

-----------------

--------

0.88

1.772.653.544.425.316.197.08

----------

-----------------

--------

0.03

0.100.220.380.570.801.061.351.692.052.87

-------

-----------------

--------

0.60

1.211.812.423.023.624.234.835.446.047.25

-------

-----------------

--------

-

-0.080.140.220.310.410.520.650.791.101.471.882.34

----

-----------------

--------

-

-1.221.632.042.452.853.263.674.084.895.716.527.34

----

-----------------

--------

-

-----

0.120.150.190.230.320.430.550.690.831.001.171.36

1.561.77

---------------

--------

-

-----

1.731.972.222.462.963.453.944.444.935.425.926.41

6.907.39

---------------

--------

-

---------

0.050.070.080.100.130.150.180.21

0.240.270.300.340.380.420.460.570.690.830.971.131.301.47

---

--------

-

---------

1.371.591.822.052.282.502.732.96

3.193.413.643.874.104.324.555.125.696.266.837.407.978.53

---

--------

-

-----------------

-0.070.080.090.100.120.130.160.190.230.270.310.360.410.460.510.57

0.630.690.830.97

----

-

-----------------

-2.012.152.282.422.552.683.023.353.694.034.364.705.035.375.706.04

6.376.717.388.05

----

-

-----------------

--------

0.070.080.090.110.120.140.160.180.20

0.220.240.280.330.440 570.710.86

-

-----------------

--------

2.162.382.592.813.023.243.463.673.89

4.104.324.755.186.056.917.778.64

Friction losses calculatedwith the Hazen-Williams

Equation with C = 150


23/24

23

Friction Loss: Portable aluminum pipe with couplings - pressure loss in psi per 100 feet of pipe.


2"

1.9142.000

3"

2.9143.000

4"

3.9064.000

5"

4.8965.000

6"

5.8846.000

7"

6.8727.000

8"

7.8568.000

10"

9.81810.000

FlowGPM

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

PSILoss

VelocityFPS

10

2030405060708090

100120140160180200220240260

280300320340360380400450500550600650700750800850900

9501000110012001400160018002000

0.33

1.192.524.306.509.1112.1215.5219.3023.46

--------

-----------------

--------

1.12

2.233.354.465.586.697.818.9310.0411.16

--------

-----------------

--------

-

-0.330.560.841.181.572.012.503.034.255.667.259.01

----

-----------------

--------

-

-1.441.932.412.893.373.854.334.815.786.747.708.66

----

-----------------

--------

-

-----

0.380.480.600.731.021.361.742.172.633.143.694.28

4.915.58

---------------

--------

-

-----

1.882.142.412.683.213.754.294.825.365.896.436.96

7.508.04

---------------

--------

-

-----

0.130.160.200.240.340.450.580.720.881.051.231.43

1.641.862.092.342.612.883.173.944.795.71

-------

--------

-

-----

1.191.361.531.712.052.392.733 073.413.754.094.43

4.775.125.465.806.146.486.827.678.539.38

-------

--------

-

---------

0.140.190.240.300.360.430.500.58

0.670.760.860.961.071.181.291.611.962.332.743.183.654.15

---

--------

-

---------

1.421.651.892.122.362.602.833.07

3.313.543.784.014.254.494.725.315.906.497.087.678.268.85

---

--------

-

------------

0.140.170.200.240.27

0.310.360.400.450.500.550.610.760.921.101.291.491.711.952.202.462.73

--------

-

------------

1.561.731.902.082.25

2.422.602.772.943.123.293.463.894.334.765.195.636.066.496.927.367.79

--------

-

-----------------

-0.190.210.230.260.290.320.390.480.570.670.780.891.021.141.281.42

1.571.732.072.43

----

-

-----------------

-1.992.122.252.382.522.652.983.313.643.974.304.644.975.305.635.96

6.296.627.287.95

----

-

-----------------

--------

0.160.190.230.260.300.340.390.430.48

0.530.580.700.821.091.401.742.11

-

-----------------

--------

2.122.332.542.762.973.183.393.603.82

4.034.244.665.095.946.787.638.48

Friction losses calculatedwith the Hazen-Williams

Equation with C = 90


24/24

The Agricultural Extension Service offers its programs to all eligible persons regardless of race,religion, color, national origin, sex, age, disability or veteran status and is an Equal Opportunity Employer.

COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICSThe University of Tennessee Institute of Agriculture, U.S. Department of Agriculture,

and county governments cooperating in furtherance of Acts of May 8 and June 30, 1914.Agricultural Extension Service

Charles L. Norman, Dean

PB1721-1M-10/02 E12-4315-00-003-03

irrigation cost analysis

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