Low-Tech IrrigationLow-Tech Irrigation

Surface IrrigationSurface Irrigation

• Water flows across the soil surface to the point of infiltration

• Oldest irrigation method and most widely used world-wide (90%) and in U.S. (60%)

• Used primarily on agricultural or orchard crops

Types of SystemsTypes of Systems• Water Spreading or Wild FloodingWater Spreading or Wild Flooding

– Relatively flat fields -- allow water to find its own way Relatively flat fields -- allow water to find its own way across the surfaceacross the surface

– Minimal preparation and investmentMinimal preparation and investment– Rather inefficientRather inefficient

• BasinBasin– Dikes used to surround an area and allow for water Dikes used to surround an area and allow for water

ponding (no runoff)ponding (no runoff)– Basins are usually level (rice)Basins are usually level (rice)

Basin Irrigation of Rice in SE AsiaBasin Irrigation of Rice in SE Asia

Types of Systems, Types of Systems, Contd…Contd…

• BorderBorder– Strips of land with dikes on the sidesStrips of land with dikes on the sides– Usually graded but with no cross slopeUsually graded but with no cross slope– Downstream end may be dikedDownstream end may be diked

• FurrowFurrow– Small channels carry the water (entire surface is not wet)Small channels carry the water (entire surface is not wet)– Commonly used on row cropsCommonly used on row crops– Lateral as well as vertical infiltrationLateral as well as vertical infiltration– Furrows are usually gradedFurrows are usually graded

Water SupplyWater Supply

• Methods of water supplyMethods of water supply– Head ditch with siphon tubes or side-opening gatesHead ditch with siphon tubes or side-opening gates– Gated pipe (aluminum or plastic pipe with small Gated pipe (aluminum or plastic pipe with small

gates that can be opened and closed)gates that can be opened and closed)

Curve of Time Vs. DistanceCurve of Time Vs. Distance

Distance from inlet end (ft)

Infiltration ProfileInfiltration Profile

Flow In DitchesFlow In Ditches

SRAn

Q 2/13/21

Manning’s EquationManning’s Equation

Q= Flow rate, cubic feet per secondQ= Flow rate, cubic feet per second

n= Channel roughness, n increases as roughness increasesn= Channel roughness, n increases as roughness increases

A= Channel cross-sectional area, square feetA= Channel cross-sectional area, square feet

R= Channel hydraulic radius (Area / Wetted Perimeter), feetR= Channel hydraulic radius (Area / Wetted Perimeter), feet

S= Channel slope, vertical feet/horizontal feetS= Channel slope, vertical feet/horizontal feet

A

WP

UniformityUniformity• Inherent non-uniformity because recession and Inherent non-uniformity because recession and

advance curves are not parallel advance curves are not parallel • Factors affectingFactors affecting More UniformMore Uniform Less UniformLess Uniform

– Inflow rateInflow rate High High Low Low

– SlopeSlope Steeper Steeper Flatter Flatter

– Soil infiltration rate LowerSoil infiltration rate Lower Higher Higher

– RoughnessRoughness Smoother Smoother Rougher Rougher

– Channel shapeChannel shape Higher R Higher Rhh Lower R Lower Rhh

– Inflow timeInflow time Shorter Shorter Longer Longer

– Length of runLength of run Shorter Shorter Longer Longer

Irrigation EfficiencyIrrigation Efficiency

• Volume balance basisVolume balance basis– EEaa = V = Vzz / V / Vgg = (V = (Vg g -- VVr r -- VVdp dp -- VVe e ) / V) / Vg g

– Ea Ea Irrigation application efficiency (%/100) Irrigation application efficiency (%/100)– V V Water volume Water volume

• g g gross (delivered to field) gross (delivered to field)

• z z net infiltration (stored in root zone) net infiltration (stored in root zone)

• dp dp deep percolation (below root zone) deep percolation (below root zone)

• r r runoff (beyond end of field) runoff (beyond end of field)

• e e evaporation (from furrow and wet soil) evaporation (from furrow and wet soil)

Microirrigation

• Drip, trickle, mist irrigation– Small flows (0.5-4 gallons/hour) per emitter– Low pressures (6-15 psi)

• Good for row crops– Line source emitters

• Good for orchards & vineyards– Point source emitters

Drip Irrigation Design ConsiderationsDrip Irrigation Design ConsiderationsDrip Irrigation Design ConsiderationsDrip Irrigation Design ConsiderationsDetermine the number of emitter lines/bed and emitter spacing Determine the number of emitter lines/bed and emitter spacing

based on soil type and bed width. based on soil type and bed width. Determine the number of emitter lines/bed and emitter spacing Determine the number of emitter lines/bed and emitter spacing

based on soil type and bed width. based on soil type and bed width.

Sand-low capillaritySand-low capillaritySand-low capillaritySand-low capillarity Loam-medium capillarityLoam-medium capillarityLoam-medium capillarityLoam-medium capillarity

Clay-high capillarityClay-high capillarityClay-high capillarityClay-high capillarity

Use 2 dripper lines on Use 2 dripper lines on wide beds with wide beds with sandy soilsandy soil

Use 2 dripper lines on Use 2 dripper lines on wide beds with wide beds with sandy soilsandy soil

Drip Emitter Line CharacteristicsDrip Emitter Line CharacteristicsDrip Emitter Line CharacteristicsDrip Emitter Line Characteristics

Drip tapeDrip tape• Used primarily in row cropsUsed primarily in row crops• Emitters formed into seam during manufactureEmitters formed into seam during manufacture• Operating pressure: 6-15 psiOperating pressure: 6-15 psi• Flow rate: 0.2-1.0 gpm/100 ft (0.5 most common)Flow rate: 0.2-1.0 gpm/100 ft (0.5 most common)• Emitter spacing: 8-18 inches (12 most common)Emitter spacing: 8-18 inches (12 most common)• Wall thickness: 4-25 mil (8-mil most common)Wall thickness: 4-25 mil (8-mil most common)• Length of run: 300-600 ft (5/8-inch tape)Length of run: 300-600 ft (5/8-inch tape)

Drip tapeDrip tape• Used primarily in row cropsUsed primarily in row crops• Emitters formed into seam during manufactureEmitters formed into seam during manufacture• Operating pressure: 6-15 psiOperating pressure: 6-15 psi• Flow rate: 0.2-1.0 gpm/100 ft (0.5 most common)Flow rate: 0.2-1.0 gpm/100 ft (0.5 most common)• Emitter spacing: 8-18 inches (12 most common)Emitter spacing: 8-18 inches (12 most common)• Wall thickness: 4-25 mil (8-mil most common)Wall thickness: 4-25 mil (8-mil most common)• Length of run: 300-600 ft (5/8-inch tape)Length of run: 300-600 ft (5/8-inch tape)

Drip Emitter Line CharacteristicsDrip Emitter Line CharacteristicsDrip Emitter Line CharacteristicsDrip Emitter Line Characteristics

Hard HoseHard Hose• Used primarily in perennial cropsUsed primarily in perennial crops• Emitters glued into hose during manufactureEmitters glued into hose during manufacture• Operating pressure: 10-40 psiOperating pressure: 10-40 psi• Flow rate: 0.4-1.8 gph/emitterFlow rate: 0.4-1.8 gph/emitter• Emitter spacing: 12-60 inchesEmitter spacing: 12-60 inches• Length of run: varies depending on hose Length of run: varies depending on hose

diameter, emitter spacing and emitter flow ratediameter, emitter spacing and emitter flow rate

Hard HoseHard Hose• Used primarily in perennial cropsUsed primarily in perennial crops• Emitters glued into hose during manufactureEmitters glued into hose during manufacture• Operating pressure: 10-40 psiOperating pressure: 10-40 psi• Flow rate: 0.4-1.8 gph/emitterFlow rate: 0.4-1.8 gph/emitter• Emitter spacing: 12-60 inchesEmitter spacing: 12-60 inches• Length of run: varies depending on hose Length of run: varies depending on hose

diameter, emitter spacing and emitter flow ratediameter, emitter spacing and emitter flow rate

Pressure compensatingPressure compensatingIn-LineIn-Line

On-LineOn-Line

Drip Emitter Line CharacteristicsDrip Emitter Line CharacteristicsDrip Emitter Line CharacteristicsDrip Emitter Line Characteristics

Hard HoseHard Hose• Used primarily in perennial cropsUsed primarily in perennial crops• Emitters installed in holes punched in hoseEmitters installed in holes punched in hose• Custom emitter spacing: 12-120 inchesCustom emitter spacing: 12-120 inches• Operating pressure: 10-15 psiOperating pressure: 10-15 psi• Flow rate: 0.5 - 4 gph/emitterFlow rate: 0.5 - 4 gph/emitter• Length of run: varies depending on hose Length of run: varies depending on hose

diameter, emitter spacing and emitter flow ratediameter, emitter spacing and emitter flow rate

Hard HoseHard Hose• Used primarily in perennial cropsUsed primarily in perennial crops• Emitters installed in holes punched in hoseEmitters installed in holes punched in hose• Custom emitter spacing: 12-120 inchesCustom emitter spacing: 12-120 inches• Operating pressure: 10-15 psiOperating pressure: 10-15 psi• Flow rate: 0.5 - 4 gph/emitterFlow rate: 0.5 - 4 gph/emitter• Length of run: varies depending on hose Length of run: varies depending on hose

diameter, emitter spacing and emitter flow ratediameter, emitter spacing and emitter flow rate

Simple On-LineSimple On-Line Pressure Compensating Pressure Compensating On-LineOn-Line

Low-Tech Irrigation PumpsLow-Tech Irrigation PumpsLow-Tech Irrigation PumpsLow-Tech Irrigation Pumps

Gravity assist bucket pumpGravity assist bucket pump

(2.31 ft of elevation = 1psi)(2.31 ft of elevation = 1psi)Human-powered step pumpHuman-powered step pumpHuman-powered step pumpHuman-powered step pump

4.6 ft = 2 psi4.6 ft = 2 psi

Homemade Drip LineHomemade Drip LineOrifice Discharge (gph)Orifice Discharge (gph)

Nominal Operating HeadNominal Operating Head

Hole Hole DiameterDiameter

3 ft3 ft 4 ft4 ft 5 ft5 ft 6 ft6 ft 7 ft7 ft 8 ft8 ft

1/16 in1/16 in 7.37.3 8.58.5 9.59.5 10.410.4 11.211.2 12.012.0

3/32 in 16.5 19.1 21.3 23.2 25.2 27.0

1/8 in 29.3 33.9 37.9 41.5 44.8 47.9

Microirrigation UniformityMicroirrigation Uniformity

• Low emitter flow rates (0.5 – 1 gph)Low emitter flow rates (0.5 – 1 gph)

• Wide emitter spacing (2 - 4 ft)Wide emitter spacing (2 - 4 ft)

• Large lateral line diameter (> ½-inch ID)Large lateral line diameter (> ½-inch ID)

• Short lateral length (<300 ft)Short lateral length (<300 ft)

• Slight lateral downslope (1/2 – 1 %)Slight lateral downslope (1/2 – 1 %)

• High lateral inlet pressure (10+ psi)High lateral inlet pressure (10+ psi)

Microirrigation Filtration

Home Made Sand Filter

- Perforated pipe collection gallery

- Graduated gravel bed

- Washed sand filter media

Resources• Mike Kizer’s Homepage

– http://biosystems.okstate.edu/home/mkizer/index.htm

• OSU Extension Facts– http://pods.dasnr.okstate.edu/docushare/dsweb/Get/

Document-1443/BAE-1511web.pdf