dennis pittenger - uc agriculture & natural resourcessimple irrigation with eto dennis pittenger...

SIMPLE IRRIGATION WITH ETo

Dennis Pittenger Area Environmental Horticulturist

University of California Cooperative Extension

Los Angeles County/UC Riverside

Presentation © 2013 Dennis Pittenger

Dennis Pittenger Area Environmental Horticulturist dennis.pittenger@ucr.edu Phone: 951.827.3320 CENTER FOR LANDSCAPE & URBAN HORTICULTURE <www.ucanr.edu/cluh>

• B.S. & M.S. Horticulture, Ohio State University

• 32 years experience

– Landscape & urban horticulture

– Education and applied research programs

– Landscape irrigation mgt., plant water needs, weather-based irrigation control

– Presentations, workshops, publications, Web

. • Los Angeles County/UC Riverside

Quiz Answers

1. Evapotranspiration

2. True

3. True

4. True

5. True

6. False

7. False

8. True

9. True

10. 80%; 50% 10/16/13

.

• Los Angeles County/UC Riverside

Goals • Understand ETo – what it is, how it works.

• Review research-based insights on landscape water needs.

• Understand plant water demand estimation principles and variables.

• Learn simple, accurate ETo-based method to estimate accurate plant factors, water budgets, irrigation and schedules.

• Los Angeles County/UC Riverside

Useful Reference Materials • U.C.C.E. Center for Landscape and Urban Horticulture

– www.ucanr.edu/cluh (Landscape Water Management tab on left)

• Irrigation Association’s Landscape Irrigation Auditor Book, 2nd Ed. 2011. Chapter 7 and Appendix D.

• U.C. Cooperative Extension Handbook: Landscape Irrigation System Evaluation and Management. (D. Shaw and D. Pittenger, 2009)

– www.ucanr.edu/cluh (Landscape Water Management tab on left)

• California Dept. of Water Resources – CIMIS

– CIMIS (California Irrigation Management Information System)

– http://www.cimis.water.ca.gov/cimis

• Los Angeles County/UC Riverside

Useful Equations

Inches = Gallons ÷ (Sq. Ft. × 0.62)

Gallons = Inches × Sq. Ft. × 0.62

• Los Angeles County/UC Riverside

Landscapes require irrigation when…..

…..performance expectations exceed plant adaptation to precipitation

Expectations and Design Intent

determine landscape water need

Demand for Climate-based Landscape Water Need Estimates

Water budgets & tiered pricing

State & local conservation ordinances

‘Green’ building development programs, standards, codes

Smart irrigation controllers

Sustainable landscapes

U.S. EPA WaterSense

Save water and money

Landscape Water Conservation Programs

Visual courtesy of B. Mecham, Irrigation Assoc.

Standards Organizations

Common Provisions

Unique arbitrary procedures to set landscape water budget or need

Reduced turfgrass

Native plants

Limited or no potable water for landscape

Use of alternative water sources

reclaimed, stored precipitation, graywater

Demand for Climate-based Landscape Water Need Estimates

Water budgets

State & local conservation ordinances

“Green” development standards & codes

Smart irrigation controllers

Sustainable landscapes

U.S. EPA ‘Water Sense’

Save water

Save money

Why & How Plants Use Water

• Water loss is essential!!

• Maintain structure

• Photosynthesis & physiological processes

• Cooling (transpiration)

• Transports minerals & nutrients

Why & How Plants Use Water

• SPAC:

Soil-Plant-Air-Continuum

• Creates pull

Transpiration

H+

H+

O

-

H+

H+

O

-

H+

H+

O

-

H+

H+

O

-

H+

H+

O

-

H+

H+

O

-

H+

H+

O

-

H+

H+

O

-

Stomata

Evapotranspiration (ET)

Climate-based reference

Inches/day

ETo = estimated water use of well-watered cool-season turf

Calculated from weather data

Sunlight, temperature, RH, wind

ASCE Penman-Monteith equation

Based on field research with agricultural crops

ETo = Reference Evapotranspiration An estimate of environmental water demand

over a planted area

Reference Evapotranspiration

Real-time = ETo or ETo

Historical Average = ET or ETH

Data sources

www.cimis.water.ca.gov

On-sight local weather station

Climate-Based Water Budgets Adjustment of ETo

Basic Water Budget or Water Requirement

Gallons = ETo × AF × LA × 0.62

gallons = inches × % × sq. ft. × conversion

ETo = reference evapotranspiration; climate impact

AF = ETo adjustment factor

LA = sq. ft. landscape area

0.62 converts inches per sq. ft. to gallons [gal. ÷ (in. x sq. ft.)]

Mandated “conservation” water budget

Plant types & sites respond differently to climate

Water Use ≠ Water Requirement Plants may use more water than they need to meet

expectations

Why Adjust ETo?

Climate-Based Water Budgets

Maximum Applied Water Allowance or Budget

MAWA = ETo × ETAF × LA × 0.62 Gallons = inches × adjustm’t. factor × sq. ft. × conversion

ETAF set by water purveyor, ordinance, design prog. 0.7 Calif. Model Water Efficient Landscape Ordinance 0.4, 0.6, 0.8, 1.0 common

ETo = reference ET ETAF = ET adjustment factor LA = landscape area 0.62 converts inches per sq. ft. to gallons [gal. ÷ (in. x sq. ft.)]

Climate-Based Water Budgets Need reliable plant factor estimates

Basic Water Budget or Water Requirement

Gallons = ETo × PF, KL , or Kc × LA × 0.62

gallons = inches × % × sq. ft. × conversion

ETo = reference evapotranspiration; climate impact

PF, KL, Kc = plant material adjustment factor LA = sq. ft. landscape area

0.62 converts inches per sq. ft. to gallons [gal. ÷ (in. x sq. ft.)]

KL = KPLANTS × KVEG. DENSITY × KMICROCLIMATE

KPLANTS from WUCOLS or list

KVEG. DENSITY and KMICROCLIMATE assigned by user

Landscape Coefficient (KL)

Typical ETo Adjustment Calculation

PROS

Source of numbers

Categories by climate zone and water use

Includes numerous spp.

Hardcopy and on-line

CONS

Not science based

Data not reliable

False sense of precision

Complex and perplexing to use

Not readily revised

WUCOLS Water Use Classification of Landscape Species

Simplified Landscape Irrigation Demand Estimation

S L I D E …..a new paradigm

for selecting Plant Factors..…

Principles:

Plant factors accurately estimated by broad plant type categories based on science and research

Landscape water need estimated by weighting sq. ft. of each plant type present

SLIDE Paradigm

SLIDE Features

Simple to understand & use

Replaces need for huge data base

Reduces number of factors or variables

Accommodates new plants

Scientifically & conceptually sound

Assimilation and application of ≈20 yrs. of data

Scientifically traceable

Provides reliable numbers for calculations

Wide geographic & climatic application

Current Development Status of SLIDE

Presenting to key stakeholders and decision makers

Electronic discussion system among researchers

Preparing technical manuscript to establish scientific merit

SLIDE Leaders

Roger Kjelgren – Utah State University

Richard Beeson – University of Florida

David Shaw – University of California

Dennis Pittenger – University of California

S623: Standardized Procedure for Determining Landscape Plant Water Requirements

Am. Society of Agricultural &

Biological Engineers (ASABE)

SLIDE concepts integrated

National Standard Being Developed

KL = KPLANTS × KVEG. DENSITY × KMICROCLIMATE

Landscape Coefficient (KL)

SLIDE Rules

Estimating Plant Water Needs Through Science

Define a reference for plant water use that is a function of climate (ETo)

Compare water needed to maintain given plant with reference amount

Express plant water need as % of reference

Plant Factor (PF) – acceptable appearance, function

Crop Coefficient (Kc) – optimum growth or yield

Estimating Plant Water Needs Through Science

Estimating Landscape Water Needs Using ETo

Assumptions:

Landscapes need/use water like ag. crops

Plant water needs change in lockstep with changes in ETo

Plant canopy is uniform

Same or similar plants across landscape

Ability to irrigate the landscape plants uniformly

ETo Approach OK With Turf

Visual courtesy of R. Kjelgren, Utah St. Univ.

Turfgrass Irrigation Needs

Cool-season Kc:

80% ETo annual avg.

(60% ETo minimum)

Warm-season Kc:

60% ETo annual avg.

(40% ETo minimum)

Field Studies on Landscape Plants’ Water Needs in California

79 plant species to date

33 trees, 12 groundcovers, 34 shrubs

Locations – no summer rainfall

Inland valley – 28 trees

South Coastal – 28 shrubs, 9 groundcovers, 5 trees

Low Desert – 6 shrubs, 3 groundcovers

Standard Research Approach

Minimum water needed for acceptable performance/appearance (%ETo = PF)

Apply multiple % ETo treatments

Irrigate when:

Σ(daily ETo × trtmt. %) = depletion target

Evaluate plant performance Aesthetics

Growth

Assumption

Visual courtesy of R. Kjelgren, Utah St. Univ.

Center for Landscape & Urban Horticulture University of California Cooperative Extension

Phormium tenax Aesthetic Quality Ratings

0.0

2.0

4.0

6.0

8.0

LSD 0.05

0.36 ETo

0.18 ETo

0 ETo

Phormium tenax

Center for Landscape & Urban Horticulture University of California Cooperative Extension

Center for Landscape & Urban Horticulture University of California Cooperative Extension

Arbutus unedo Aesthetic Quality Ratings

0.0

2.0

4.0

6.0

8.0

LSD 0.05

0.36 ETo

0.18 ETo

0 ETo

Center for Landscape & Urban Horticulture University of California Cooperative Extension

Salvia leucantha Aesthetic Quality Ratings

0.0

2.0

4.0

6.0

8.0

0.36 ETo

0.18 ETo

0 ETo

Center for Landscape & Urban Horticulture University of California Cooperative Extension .

Pyracantha ‘Santa Cruz’ Aesthetic Quality Ratings

0.0

2.0

4.0

6.0

8.0

0.36 ETo

0.18 ETo

0 ETo

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

Jan-Feb Mar-Apr May-Jun Jul-Aug Sep-Oct Nov-Dec

Cassia (Senna) 2007

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

Jan-Feb Mar-Apr May-Jun Jul-Aug Sep-Oct Nov-Dec

Star Jasmine 2007

20% and 40% are the same

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

Jan-Feb Mar-Apr May-Jun Jul-Aug Sep-Oct Nov-Dec

Juniper 'Sea Green' 200720%

40%

60%

80%

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

Jan-Feb Mar-Apr May-Jun Jul-Aug Sep-Oct Nov-Dec

Lantana 2007

Groundcovers, Trees, Shrubs

Woody plant performance & water need uncoupled with ETo

ETo × PF model cannot precisely estimate non-turf water need

Landscapes interactions too complex

Use more water than they need

Traditional landscape plants perform acceptably in with low to mod. water

Typically acceptable 30-60% of ETo

Less water may limit growth, not quality

Discrepancies with WUCOLS

Center for Landscape & Urban Horticulture University of California Cooperative Extension

Using & Adjusting PF & Kc Values

0.00

0.20

0.40

0.60

0.80

1.00

W

C

More Leaves & Growth High Expectations

Less Leaves & Growth Low Expectations

Turf Gc-Sh-Tr-Fl

Center for Landscape & Urban Horticulture University of California Cooperative Extension

Copyright © 2010-2013 D. Shaw and D. Pittenger

SLIDE Rules

Landscape plant water USE ≠ NEED

Plants often use more than they need

Meet minimum expectations in a range of % ETo

ETo concept has limited accuracy in landscapes

Landscape plants tolerate managed drought

Most non-turf plants need near 50% ETo

Plant factors accurately estimated by categorizing plant

SLIDE Rules (DRAFT)

Categories of Water Need

Turfgrass = 60% ETo (w-s) / 80% ETo (c-s)

Tree/Shrub/Groundcover/Vine = 50% ETo

Herbaceous Perennial Flowers & Foliage = 70% ETo

Annual-Perennial Flowers/Foliage = 80% ETo

Low Expectations/Desert Adapted = 30-40% ETo

WUCOLS Analysis

WUCOLS ZONE 1 2 3 4 5 6 AVG.

# of species appropriate to

zone 1602 1088 1969 1185 529 820 1199

% High Water Needs

0.7 – 0.9 ETo 5 6 5 9 7 8 7 (84)

% Medium Water Needs

0.4 - 0.6 ETo 51 52 57 57 66 68 59 (707)

% Low Water Needs

0.1 – 0.3 ETo 38 36 31 32 25 24 31 (372)

% Very Low Water Needs

< 0.1 ETo 7 5 7 3 2 0.5 4 (48)

Control Total 101 99 100 101 100 100.5

(WUCOLS III, 2000)

Estimating Landscape Water Requirement

Accurate and Simple Equation

Gallons = ETo × PF × LA × 0.62

gallons = inches × % × sq. ft. × conversion

ETo = reference evapotranspiration; climate impact

PF = plant material adjustment factor

LA = sq. ft. landscape area

0.62 = converts depth to volume [gal. ÷ (in. x sq. ft.)]

Leaf area influences landscape water demand

Incomplete Canopy Effects & Consideration

Crown projection area × ETo × PF

Guidelines for new or sparsely planted landscapes

SLIDE Rules

PF low:

fewer leaves

PF high: more leaves

Visual courtesy of R. Kjelgren, Utah St. Univ.

Applying SLIDE Rules in Design

• Design sq. ft. of turf desired

– PF = 0.6 or 0.8 for good appearance

• Assign PF’s for primary plant type in other hydrozones

– Reduce <20% with persistent shade

• ETo × PF × sq. ft. per zone

• Sum all zones’ water needs

• Set water requirement or compare to budget or allocation

• Los Angeles County/UC Riverside

(D. Shaw, 2010)

Applying SLIDE Rules Established Landscapes

Landscape Water Budget or Water Need

Gallons = ETo × ∑(PF × LA)1-x × 0.62

∑ = (PF1 × LA1)+ (PF2 × LA2) + (PF3 × LA3)…..

Divide each zone by DU

• ETo = reference evapotranspiration, CIMIS, etc.; climate impact

• PF = plant material factor (turf, shrub-tree-vine-gc, flowers, etc.)

• LA = sq. ft. landscape area

• 0.62 = converts depth to volume [gal. ÷ (in. x sq. ft.)]

Applying SLIDE Rules New Plantings, or Wide-Spaced Plants,

<80% Canopy Cover

Landscape Water Budget or Water Need

Gallons = ETo × ∑(PF × CA)1-x × 0.62

∑ = (PF1 × CA1) + (PF2 × CA2) + (PF3 × CA3)…..

Divide each zone by DU

• ETo = reference evapotranspiration, CIMIS, etc.; climate impact

• PF = plant material factor (turf, shrub-tree-vine-gc, flowers, etc.)

• CA = sq. ft. of canopy projection (π × r2)

• 0.62 = converts depth to volume [gal. ÷ (in. x sq. ft.)]

Useful Equations

Inches = Gallons ÷ (Sq. Ft. × 0.62)

Gallons = Inches × Sq. Ft. × 0.62

• Los Angeles County/UC Riverside

Applying SLIDE Rules #1 10,000 sq. ft. landscape with 500 sq. ft. patio + 250 sq. ft. walkway

• Allocation or Budget (MAWA) = ETo × AF × Sq. Ft. × 0.62 • Gal. = 44 in. × 0.7 × 9,250 sq. ft. × 0.62 = 176,638 gallons = 31 in.

• Required = ETo × ∑[(PF × LA ÷ DU)1 + (PF × LA ÷ DU)2 …]× 0.62 (= tall fescue + mixed trees, shrubs, groundcovers + color beds) (= 25% + 70% + 5%) = 44 in. × ∑[(0.8 × 2,300 ) + (0.5 × 6,450) + (0.8 × 500)] × 0.62 = 44 in. × ∑[(1,840 ÷ 0.7) + (3,225 ÷ 0.85) + (400 ÷ 0.75)] × 0.62 = 44 in. × [2,629 + 3,794 + 533] × 0.62 = 189,760 gallons = 33 inches

• About 13,000 gallons or 2 inches Over Budget!!!

Applying SLIDE Rules #2 7,500 sq. ft. landscape, 20 trees with 24 diameter canopies, drip irr.

• Allocation or Budget (MAWA) = ETo × AF × Sq. Ft. × 0.62 • Gal. = 44 in. × 0.7 × 7,500 sq. ft. × 0.62 = 143,220 gallons = 31 in.

• Required = ETo × ∑[(PF × LA ÷ DU)1 + (PF × LA ÷ DU)2 …]× 0.62 (= tree #1 + tree #2 + tree #3 + etc.) = ETo × ∑(𝐴𝑟𝑒𝑎 = 𝜋𝑟2 trees #1 to #20), then multiply by PF OR, = ETo × Avg. tree canopy area × 20, then multiply by PF = 44 in. × 3.14 × 144 s.f. × 0.5 × 0.62 = 6167 gal. per tree = 6167 gal. per tree × 20 trees = 123,340 gallons = 123,340 gallons ÷ 0.85 = 145,106 gallons = 31 inches

• About 1,886 gallons or 0.4 inches Over Budget!!!

Options to Reduce Water Needs

• Improve DU

• Adjust plant spp. mix

– Turf = 31 gal./sq. ft.

– G-S-T = 16 gal./sq. ft.

– Color = 25 gal./sq. ft.

• Reduce planted area

• Lower expectations

Expectations Met & Water Conserved

Take Home

ETo model not highly accurate for landscapes

Exact Plant Factors not needed for non-turf plants

Non-turf plants perform acceptably over broad % of ETo

SLIDE provides simple, accurate PFs Assign Plant Factors by plant type

Determine sq. ft. of turf first

Adjust non-turf PF to meet performance expectations

Principles:

Based on science - plant factors accurately estimated by broad plant type categories

Landscape water need estimated by weighting sq. ft. of each plant type

SLIDE Paradigm

Dennis Pittenger Area Environmental Horticulturist

dennis.pittenger@ucr.edu Phone: 951.827.3320 Center for Landscape & Urban Horticulture <www.ucanr.edu/cluh>

• Los Angeles County/UC Riverside