Presentation on theme: "NRCS Farm Irrigation Rating Index"— Presentation transcript:
1 NRCS Farm Irrigation Rating Index History and UseByClare PrestwichIrrigation EngineerNRCS National Water and Climate Center
2 The NeedA uniform and objective evaluation method for planning irrigation water conservationMethod of documenting present water use as well as the effects of changes made by improving both irrigation system and managementReduce the need for difficult and time consuming complete seasonal field evaluations
3 The ProcessMultidisciplinary team was formed from several western states and a national committeeBasic data and procedures originated as a result of a west wide water conservation emphasis program during the 1980’s
4 The Results Farm Irrigation Rating Index (FIRI) Assist Offices Plan water management improvementsEstimate water conserved by improved managementEstimate the runoff and deep percolationProvide a tool for follow up and document accomplishment in water management
5 What it is not Replacement for on site evaluations A finite farm or field application efficiency, or specific deep percolation and runoff amounts
6 What it is A procedure for comparing improvements or changes Year to yearField, Farm and project levelRelative ratingA season long evaluation not a single eventComposed of three elementsManagementSystemPotential efficiency
7 ManagementWater management is the human element. Decisions scientifically based, knowledge to operate the system, and maintenance performed.The management element is defined by 6 factorsWater measurementSoil moisture monitoring and schedulingIrrigation skillMaintenanceWater delivery constraintSoil Condition
8 System Element Factors selected according to irrigation type System element is defined by nine factorsWater distribution controlConveyance efficiencyLand levelingClimaticSprinkler designWindTail water reuseEmitter cloggingTrickle design
9 Potential Efficiency Element A measure of the optimum application efficiency for the method of irrigation being usedValues based on full canopy cover and systems are well designed and maintained.
22 FIRI useUse extensively during the 1994 Irrigation induced erosion surveyProject ranking and comparison for NRCS programs (e.g. EQIP, CSP)
23 ExamplePasture irrigated by uncontrolled flood with 3000ft of earth ditch on sandy loam soil. Water delivered on a18 day rotation limited rate
24 Present condition Potential Efficiency - 50 Management No water measurement .9Schedules based on Plant indicators .94Irrigation Skill – Lacks full attentionMaintenance – good .98Water Delivery – fix rotation limited rate .85Soil Condition – conservation tillage .98
25 Present Condition System MGT= .9 x .94 x .96 x .98 x .85 x .98 = .663 Control at - Farm delivery .94Conveyance – 3000ft earth ditch .91Unleveled fields - .82No tail water reuse -1.0MGT= .9 x .94 x .96 x .98 x .85 x .98 = .663SYS = .94 x .91 x .82 x 1 =.701FIRI = 50 x x = 23.3
26 FutureOperator wants to change to a graded furrow system with land leveled fields and tail water reuse. Ditch replaced with gated pipe
27 Future ConditionPotential Efficiency – change to graded furrow 50 to 75Management changesAdd measuring device .90 to .96Scheduling - no change .94Irrigation skill - follows plan .96 to 1Maintenance - no change .98Delivery - no change .85Soil tillage - no change .98
28 Future Condition System MGT = .96 x .94 x 1 x .98 x .85 x .98 = .737 Control – change to each set .94 to 1Conveyance – change to gated pipe .91 to .99Land – change to laser level .82 to 1Add tail water reuse – change 1 to 1.08MGT = .96 x .94 x 1 x .98 x .85 x .98 = .737SYS = 1 x .99 x 1 x 1.08 = 1.069FIRI = 75 x x = 59.1
29 Compute the water conserved Water conserved with seasonal net irrigation of 2 ac-feet/acPresentAc-ft / acFutureAc-ft / ac
31 Problems Management Section has greatest weight More subjective to the person doing ratingNRCS required to report water saved or conservedFIRI rating taken as actually efficiencyMore water saved than availableMost states restrict water rights to 4 to 5 ac-ft/acFrom our example= 5.2 ac-ft/ac saved
32 Possible changes Update Potential Efficiencies Add systems like LESA, MESA, SDI, etc.Update Management factors to reflex current TechnologySoil moisture/scheduling Flow measurement, etc.Change computation method from straight multiplication to a statistical method.
33 Original methodPE x f1 x f2….x FnProposed methodPE x (1-sqrt((1-f1)2+(1-f2)2….+(1-fn)2))The multiplication approach essentially assumes a worst case scenario where each influence has full weight regardless of the other factorsThe Statistical approach recognizes that if one condition is poor, that the influence of another variable is not as great as it would be if it were the only problem.
35 Value of FIRI Still an Effective tool Quick, uniform and provides reasonable comparisonsUsers need to be realisticBetter input gives better comparisonNot meant for black box useStill a relative value