Low Volume Irrigation - Working Copy

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1. Low Volume Irrigation

LHAP 302

2. Design

Design goal is to broadcast water as evenly as possible across an entire area. Water is delivered to the surface of the planted area.

Design goal is to apply water to a uniform depth, either directly to the plant root zone or in a limited area. Water is delivered at or below the surface of the planted area

Installation

Most of system installed in underground trenches.

In residential applications, most of system installed at or near grade and covered with 2-3 inches of mulch. Typically, installation requires less time. In commercial applications, most of system installed in underground trench and exposure of any drip tubing is minimal

Maintenance

Problems with system are easy to spot. Many problems require trenching to repair. Solvents are required to repair pipes.

Problems with system may be less noticeable. Scheduled maintenance requires greater attention. However, most problems with the system can be repaired faster and more easily than conventional systems. Generally, no solvents are used.

TABLE 1-1: CONVENTIONAL VS. LOW-VOLUME IRRIGATION

Conventional Irrigation (Spray Heads and Rotors)
Low- Volume Irrigation (Xerigation) Rainbird.com

3. Benefits

Better Water Management – more efficient Lower Install and Maintenance Costs

Improved Plant Health

4. The Design Process

for watering shrubs and trees Gather accurate site data

Collect information about the site to be irrigated and the plants in the site

Soil type

Coarse – sands, sandy loams, loamy sands Medium – loams, silt loams, silt

Fine – clay loams, sandy clay loams, silty clay loams, clay

Climate -temperature and precipitation, PET water source – dirty water, organics, minerals

Filtration Required
5 GPH 200 mesh 1.0 GPH + 150 mesh dripline 120 mesh

5. General Requirements

Determine Plant Types and Water Requirements

Individual plants – irrigated by point source emitters - individual emission devices

(single/ multi outlet emitters, micro-bubblers) Trees – may need more than one device

space 3-4 bubblers or SQ nozzles evenly around tree

Dense plantings – cover area evenly by using line source emitters or microsprays

(inline emitter tubing , microsprays)

For dense plantings determine base plant ( lowest water needs)

6. Calculating line source

determined by soil type Soil type Rs (inches) Es (inches) qs (gph)

AR (in/hr) Coarse 18 12 1 1.07 Medium 18 18 1 0.71

Fine
24 18 0.5 0.27

Rs = Row spacingEs = emitter spacingQs = flow rateAR= application or precipitation rate

7. Soil Type

Maximum Infiltration Rate
Wetting Pattern
Maximum Wetted Diameter

Available Water (AW) Coarse (sandy loam) .72 - 1.25 inches per hour

Coarse
0 - 3.0 feet
4 inches per foot Medium (loam) .25 - .75 inches per hour
Medium
0 - 4.0 feet 2
0 inches per foot Fine (clay loam) .13 - .25 inches per hour
Fine
0 - 6.0 feet
5 inches per foot

8. Calculating Point Source

FIND PLANT COEFFICIENT
Plant Type
Max appearance

(lush) Acceptable appearance Low maintenance (lean and green)

Trees
9 - 0.95
70 – 0.75
45-0.50
Shrubs
60 - 0.65
45 – 0.50
30 – 0.35
Desert Plants
40 – 0.45
30 – 0.35
20 – 0.25
Ground cover
70 – 0.80
50 – 0.60
30 – 0.40
Mixed Lscp
90 – 1.00
75 – 0.80
50 – 0.55
Plant type

¼ to ½ ground shaded ½ to 2/3 ground shaded Over ¾ ground shaded

Low growing plants <45cm tall 0.35 - 0.45
60 – 0.75
80 – 0.95
Small shrubs
1 – 1.5m tall
35 – 0.50
70 – 0.80
85 – 0.95

Large shrubs, trees > 4m 0.40 – 0.55

75 – 0.95
95 – 1.00

Turfgrass n/a n/a 1.00 Vegetation High Average Low

Turf/Lndscp Plants 1.2 – 1.4
0 0.5 – 0.8

Crop coefficient (KL) = species factor x density factor x microclimate factor

Eg: acceptable trees (high end) with ⅔ ground shaded and average microclimate

KL = 0.75 x 0.75 x 1 = 0.56

9. Slide 9

DETERMINE ETo

Alberta Climate Information Website https://agriculture.alberta.ca/acis/

Potential Evapotranspiration rates - from Rainbird Catalogue use if ETo not available

Course visual for https://www.rainbird.com/sitesdefault/files/media/documents/2018-02/LowVolumeGuide.pdf

10. 3. DETERMINE PLANT CANOPY ( IN FT)

Canopy = .7854 x diameter x diameter x .75 .7854 x 5 feet x 5 feet x .75 = 14.73 sq ft

WATER REQUIREMENTS

For individual plants in GPD (gallons per day) GPD/plant = .623 x Canopy area x KL x ETo application efficiency

GPD/plant = .623 x 14.73 x .56 x .20 = 1.03 gallons per day

.90 https://www.rainbird.com/sites/default/files/media/documents/2018-02/LowVolumeGuide.pdf

11. Choose a base plant (one with lowest water requirements) for each hydrozone...

Choose a base plant (one with lowest water requirements) for each hydrozone then choose an emission device for that plant

Types of Plants

Use – accessibility, traffic, vandalism Size of Planted Area – individual vs tubing or tape

Soil type and Infiltration rate Coarse soil = high flow, bubblers

Very fine soil = low flow, emitters, drip tubing

Watering Window

Emission devices Page 32 Rainbird Low volume guide http://www.rainbird.ca/documents/drip/LowVolumeGuide.pdf

System layout page 55 Choosing Emission Devices

12. 5. CHOOSE EMITTERS

1 Gallon per day = 7 gal per week

2 emitters at 0.5 gal per hour for 1 hour per dayor 2 emitters at 1 gal per hour for 30 minutes per day or 2 emitters at 1 gal per hour for 1 hour every 2nd day

Choose how many emission devices you need per plant based on the plant water needs.

If base plant needs 1 and medium shrubs required twice as much water, they will need 2.