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Drip
Irrigation Design Manual |
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This manual includes design steps,
design layout, technical data, and detailed layouts for A1 drip
line, single outlet drippers and TOP drip heads |
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- Calculating
water requirements for an individual plant using single outlet
drippers or TOP 12 zone drip head
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First formula to determine gallons
per day per plant
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Ks =Landscape coefficient:Table A3 |
ETr =Reference evapotranspiration rate (inches per
day): Table A1 provided
worst case |
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Climate efficiency:Table A1 |
Estimated emitter uniformity:
Table A2 |
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If you have all the information
concerning the individual plant site, the following pieces of
this puzzle fall into place. For example: we have a tree with
a 10' diameter of canopy (equivalent to an area of 78.5 sq.ft
) in a cool, humid climate (the canopy area is the plant root
zone area) |
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The formula for sq.ft:
3.14159 x radius x radius = plant area in sq.ft |
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Formula
# 1 |
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We
find out our tree needs 12 gallons of water per day. Now we
need to determine the number of drippers needed to apply 12
gpd to the 10' tree. Use Formula # 2: |
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Note: This formula
needs to apply to every different size of plant on the design |
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Table A1 provides
you with ETr and climate efficiency |
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Climate |
Definition (mid summer) |
ETr (worst case, inches per day) |
Climate Efficiency (%) |
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Cool humid |
<70 degree F > 50 % H |
.10 -.15" |
100 |
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Cool dry |
<70 degree F > 50 % H |
.15 -.20" |
95 |
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Warm humid |
<70-90 degree F >50 % H |
.15 -.20" |
95 |
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Warm dry |
<70-90 degree F >50 % H |
.20 -.25" |
90 |
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Hot humid |
<90 degree F > 50 % H |
.20 -.30" |
90 |
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Hot dry |
<90 degree F > 50 % H |
.30 -.45" |
85 |
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H-Humidity |
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ET varies as a function of the mix of plants, density
of plantings and the effects of microclimate |
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Table A2 provides
you with estimated emitter uniformity |
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Emitter type |
Poor |
Fair |
Good |
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In line dripper |
65% |
80% |
90% |
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PC in line dripper |
85% |
90% |
95% |
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Button dripper |
60% |
75% |
90% |
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PC button dripper |
80% |
85% |
90% |
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Different plant species can vary
considerably in their rates of evapotranspiration. Some plants
transpire large amounts of water, while others use relatively
little. Values for plant factor or crop coefficients are sometime
available through local sources such as Agricultural Extension
Services and local newspapers. Check in your area. When available,
this data tends to be more accurate and can save time. Because
there is such a wide range of water needs among different plants,
the water use is divided into three user groups: High, average
and low ( see table A3, below)
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Table A3 provides
you with Ks, a landscape coefficient |
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Vegetation |
High |
Average |
Low |
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Trees |
0.90 |
0.50 |
0.20 |
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Shrub |
0.70 |
0.50 |
0.20 |
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Ground cover |
0.90 |
0.50 |
0.20 |
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Mixed |
0.90 |
0.50 |
0.20 |
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Turf grass |
0.80 |
0.75 |
0.60 |
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