1-improvingirrigation3

8/6/2019 1-ImprovingIrrigation3

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A Sure Way To Improve

Water Use Efficiency!

Roger D. Havlak

Extension Program Specialist-Turfgrass and Water Mgmt.

During the summer, it is estimated that 25

to 60 % of the water used by residential

customers is applied to the landscape.

Since evapotranspiration exceeds

rainfall in almost all areas of Texas

during the growing season,

irrigation is required to sustain

growth at a level to provide the

form and function desired in many

landscapes and turfgrass systems.

Water Deficit Comparison:

0

2

4

6

8

10

12

0 1 2 3 4 5 6 7 8 9 10 1 1 1 2

Rainfall

PET

Months

PET/Rainfall(Inches)

Annual Rainfall vs. PET forHouston, Texas

Water Deficit


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Water Deficit Comparison:

0

2

4

6

8

10

12

0 1 2 3 4 5 6 7 8 9 10 1 1 1 2

Rainfall

PET

Months

PET/Rainfall(Inches)

Annual Rainfall vs. PET forEl Paso, Texas

Water Deficit

PROGRAM GOALS

ToReplace water-thirsty turf with trees and shrubs

To save time by installing low maintenance shrubs and mulch To choose the right plant for the right place

To reduce future demand on the water utility and create

beautiful, drought tolerant landscapes.

Austin, Texas

WaterWise Landscape Rebate Program

The focus appears

to be on plant

species and

landscape design

type rather than

Does changing the

plant species in

your landscape

guarantee water

savings?


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Research

Materials and Methods

1. TexasELITEProgram

Efficient Landscape Irrigation Through Education

Tracked Water Use on Twelve (12) Landscapes

-6 xeric landscapes

-6 mesic landscapes

Comparison of Actual Water Use by Home Consumers for

Xeriscape and Typical Landscapes (June - October 2003)

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

mesic/ru

-SH1

mesic/ru

-CA1

xeric/ru

-HU1

xeric/sp-CR

2

mesic/sp-DA

2

mesic/ru

-CH2

xeric/ru

-PA3

mesic/sp-LI3

Sites

InchesofWaterperSquareFoot

Actual Inches/SqFt

Excess Inches/SqFt

a a

aa ab

ab

bcc

aa

ababab

abc

bcc

Comparison of Actual Water Use by Home Consumers for

Xeriscape and Typical Landscapes (May - September 2004)

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

mesic/ru-

SH1

xeric/ru-

HU1

xeric/sp-

HA1

xeric/sp-

CR2

mesic/sp-

DA2

mesic/ru-

CH2

xeric/ru-

PA3

mesic/sp-

LI3

xeric/drip-

HE4

Sites

InchesofWaterperSquareFoot

ActualInches/SqFt

Excess Inches/SqFt

aa

ab

bb

ab

aa

a aa

a a

aaa

a

a


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Developing an irrigation program-you

need to address these six questions!

What factors need to be considered?

How often should irrigation water be applied?

How much irrigation should be applied?

When should irrigation be applied?

How long does my system need to operate to

apply the right amount of water?

What is the distribution uniformity of my

irrigation system?

What soil type and soil depth do you have?

Clay, Silt, Sand, Loam, Clay loam, Sandy loam, etc..

Do you have a deep soil or a very shallow soil

(i.e. Hill Country)

Soils vary in TexasIs your soil suitable to grow plants?

Plant Available Soil Moisture

Water Holding Capacity

Sand = 0.8 to 1.2 inches per foot

Loam = 1.8 to 2.4 inches per foot

Clay = 2.2 to 3.2 inches per foot


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Approximate Infiltration Capacities For

Various Soil Textures and Slopes

Infiltration rate, inches per hour

Soil Texture Level Sloping Steep

Sand 1.0 0.5 0.3

Sandy loam 0.5 0.3 0.2

Loam 0.25 0.18 0.12

Clay loam 0.15 0.1 0.07

Clay 0.10 0.08 0.06

**A decrease in infiltration rates means that runoff ofwater may occur. The higher the clay content orcompaction in the soil, the lower the infiltration rate.(greater potential for runoff of water and erosion)

Salt-affected Sites

Look for Signs of Water Stress

Visual Assessment for Stressed Turf & Other Plants:

Leaf rolling

Lack of turgor pressure in the plant causes wilting

Leaving footprints in the turf

Blue/purple areas in the turf

Turfgrass, as well as most landscape species, can

withstand short periods of water stress without

permanent damage to the plant.


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Total Soil Water Loss vs. Potential

Evapotranspiration (PET)

0

0.05

0.1

0.15

0.2

89 90 91 92 93 94 95 96 97

Time (Days)

SoilWaterLoss(Inches) TR-10

TR-20

TR-30

SA

Landscape

PET

WaterWhen and how much should I water?

The best time to water is in the early morning (4:00

- 6:00 am) when wind is low, water pressure is

highest, demand is low, evaporation rates are low.

Watering in the evening places water droplets on

the leaves for extended periods of time, which

enhances disease.

Water deep and infrequent!!!! If possible, water to

a depth of 6 to 8 inches into the soil. You may have

to use additional cycles on the irrigation system to

achieve this so as to avoid runoff. Use a soil probeor screwdriver to check your watering depth.

Out of adjustment

GeysersCovered Heads

Can you say Oops!?

Poor Water

Management

Practices


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Wrong Head

Low PressureNot

Enough

Water!!

Too Much Water!!

So how do we evaluate an irrigation

system? Answer: Irrigation Audit!

A method for evaluating the performance of airrigation system.

Used to assess the uniformity of distributionby the sprinkler heads.

Used to determine an irrigation systemsapplication rate.

Vital for proper irrigation management.

Need to Consider:Landscape Design and Irrigation Zones

(Its an effective way to apply water only to thoseareas in need of supplemental irrigation)


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What equipment is required to do an

irrigation Audit?

What equipment is required to do an

irrigation Audit?

Irrigation Audit:Basic Steps

Place the Collection Cups

H

H

H H

H

HC

C

C

C

C C

C

C

C

C

C

C

C

C

C

Arrangement of Catch Cans


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Irrigation Audit:Basic Steps

Check for Problems

**allow system to run for 15 minutes**

Irrigation Audit:Data Analysis

You can obtain an average application rate andaverage zone rate by performing an irrigation audit.

.25+.30+.40+.50+.25+.30= 2.0

2.0/ 6 = .33 average application rate

in 15 minutes in zone 1

(Application rate per hour = 0.33 x 4 = 1.3 per hour)

Gross Precipitation Rate

Overhead Spray and Rotor Zones

PRgross = (96.25 x Q) / A

PRgross = Gross precipitation rate (in./hr)

Q = Average station/zone flow rate (gpm)

A = Station/zone area (square feet)

Gross Precipitation Rate

Drip/Micro-Irrigation Zones

PRgross = (231.1 x Qavg) / (LS x ES)

PRgross = Gross precipitation rate (in./hr)

Qavg = Average emitter flow rate (gph)

LS = Lateral (row) spacing (inches)

ES = Emitter spacing (inches)


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How do you calculate

Distribution Uniformity?

Spray or Rotor Based Zones

**Compare the average of the lower quarter of

the samples with the overall average of the

samples.

Step 1: Order the catch can volumes in a list

from smallest to largest

Step 2: Calculate the average volume of the

cans containing the least amount of

water [lower 25% values (VLQ)]



Spray or Rotor Based Zones

Step 3: Calculate the average volumes for all

the cans (Vavg)

Step 4: Calculate the lower quarter

distribution uniformity (DULQ) as a

percentage

Formula: DULQ = 100 x (VLQ/Vavg)

If using DU for landscape

irrigation scheduling:

**When the lower quarter distribution

uniformity value is less than 50%, you may

want to use the lower half distribution

uniformity formula:

Formula: DULH = 38.6 + (0.614 x DULQ)

(example: DULQ of 60% = DULH of 75%)

**The DULH limits the distribution uniformity so

that a poor uniformity will not cause an

extreme waste of water when scheduling.



Drip/Micro-Irrigation Based Zones

**Emission uniformity (EU) is determined by

measuring the total discharge volumes from

emitters and comparing the variation in these

total volumes.

**The recommended minimum EU for line-

source drip/micro-irrigation on moderate

terrain is 80%.


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Drip/Micro-Irrigation Based Zones

EU = 100 x [1-(1.27 x Cv)/n] [Qmin/Qavg]

EU = Emission uniformity

N = Number of emitters per plant

Cv = Manufacturers coefficient of variation

Qmin = Minimum emitter flow (gph) for theminimum pressure in the system

Qavg = Average emitter flow rate (gph) forthe average or design pressure in the

system

Type of Zone Excellent Very Good Good Fair Poor

% % % % %

Fixed Spray 75 65 55 50 40

Rotor 80 70 65 60 50

Impact 80 70 65 60 50

Micro Spray 80 70 60 50 40

Drip-Standard 80 70 65 55 50

Drip-Pressure 95 90 85 80 70

Ratings of Distribution Uniformity

Source of Information

The Irrigation Association

Document: Landscape Irrigation Scheduling

and Water Management

http://www.irrigation.org


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What does it mean?

Average application rate for the fields

were:

In/Hr Uniformity

University of Houston 3.11 34%

TAMU Kyle Field 0.54 52%

TAMU Soccer Field 0.54 43%

80% ideal!

Must repeat for all zones

Can be done for landscape beds

Can not be done for drip systems

(use calculation for emission uniformity)

Environmental conditions may affect theresults of the audit (i.e. wind)

Time of day may affect the audit

Irrigation Audit: Things to Consider?


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