ASABE Water Use Standard (SLIDE-Simplified Landscape Demand Estimation)-How to Use Roger Kjelgren Dept. Climate-Plants-Soils Utah State University

Why? – Past - Northern Utah drought, ~10-14 year cycles – Present - warmer winters, early snowmelt, less water – California ASABE Standard S623- “Estimating Demand of Landscape Plants” – Tool > estimate landscape water demand ≈ landscape water use based on ETo and replaced by irrigation – Imbedded in SLIDE (Simplified Landscape Irrigation Demand Estimation) How much water should a landscape be using

Past – Drought Cycles Upper Bear River Flow 1200 year flow record from tree rings 20 th century unusually wet; past droughts have been much longer; severe droughts will happen again 20 th century average flow 20 th century average flow

Past 50 years: More rain, less snow, warmer winter temperatures Present – Warmer Winters Alta snowpack April 2012 Warmer winter temperatures= Less snowpack later in season, longer growing season

California Governor Brown April 2015 – 25% reduction in urban use of potable water – Remove 50 million feet 2 (1150 acres) of lawn Train wreck: dead lawns, lawns replaced with gravel-no design; trees will start dying soon

How to Estimate Demand Weather station sited over well-watered turf – Gives values of potential evapotranspiration: ETo – Alone, ETo tells you nothing about actual plant demand Fraction of ET o (Plant Factor) to estimate water use yet maintain acceptable appearance of established landscape plants Recommended Plant Factor Turf-Cool Season0.8 Turf-Warm Season0.6 Woody plants-Humid0.7 Woody plants-Arid0.5 Desert plants0.3 ASABE S623 Standard gives Plant Factors (PF): ETo x PF = estimated water demand of plant type

SLIDE Rule #1: Reference ETo—basis for estimating water demand SLIDE Rule #2: Plant factors (PF)—correct ETo down to estimate water demand of turf, non- turf, desert plant types (ASABE 623 standard) SLIDE Rule #3: Hydrozone —species with highest PF in a zone (irrigation valve) = PF for entire zone SLIDE Rule #4: Density—within a hydrozone, plant density >80% =‘big leaf’ water demand; <80% = individual plant water demand Simplified Landscape Irrigation Demand Estimation & ASABE Standard Fraction of ET o (Plant Factor) to estimate water use yet maintain acceptable appearance of established landscape plants Recommended Plant Factor Turf-Cool Season0.8 Turf-Warm Season0.6 Woody plants-Humid0.7 Woody plants-Arid0.5 Desert plants0.3

Annual Climate, Wasatch Front 100 years of data Spring climate highly variable in rainfall and ETo; June can be very wet July, August reliably hot and dry Seasonal ETo ≈ 40 inches Seasonal demand : ETo (season) x Plant factor

How to use Plant Factors Four ways to use Plant Factors with ETo – Planning: Water target (budget) in gallons Select plants Spatial arrangement to meet target in gallons – Irrigation design: configure drip irrigation (how much) to meet target (budget) – Irrigation scheduling: when to irrigate based on ETo – Tracking water consumer performance: WaterMAPS

1. Planning: Seasonal Water Demand Example, calculation based on planting plan; ET season = 40” Total area=6400 ft 2 ; plant area 1700 ft 2 Rock mulch Tree, 20 feet diam Tree: 20’=310 ft 2 x 20 “ (40” x 0.5 PF) x (“/ft to gallons conversion) =~4,000 gallons Shrubs, 5 ft diam Shrubs: 20 ft 2 each, PF=0.5, =~750 gal total Desert Perennial bed, 10 x 30 feet Desert perennials: 300 ft 2 PF=0.3 =~ 2,200 gal Turf, 25 x 40 feet Turf: 1000 ft 2 =~20,000 gallons

Sample design desert plants -8% plant cover -Seasonal demand = 40” x 0.3 x area =1,100 gal (1”) -8% all turf cover)

Sample design desert plants -33% plant cover -Seasonal demand = 40” x 0.3 x area = 1,700 gal (4”) -12% all turf cover)

Sample design mixed plant types -100% plant cover -Seasonal demand = 40” x 0.3 x area = 7500 gal (17”) -54% all turf cover)

How could they possibly determine how much water?

2. Drip irrigation layout zones <80% plant cover: gallons individual plants=depth water to apply (1” or 2”) x PF

Irrigation Isolated Plants Assume 2 (or 1) inches every irrigation Gallons to apply depends on plant size: 2” (1”) to apply x tree cross section area (radius 2 x 3.14) Determine how long to run system to apply that # gallons Determine number, type of emitters to supply that volume given how long system operated Plant Crown Diameter (feet) Crown Area (square feet) Gallons for a 2" irrigation Example Drip Emitter Combinations for Applying ca. 2" of Water during Irrigation Periods of Different Durations 2 hours4 hours8 hours /2gph--** gph1-1gph1-1/2gph gph2-1gph2-1/2gph gph2-2gph2-1gph gph3-2gph3-1gph gph9-1gph5-1gph gph6-2gph6-1gph gph8-2gph8-1gph gph10-2gph10-1gph gph13-2gph13-1gph gph12-2gph15-1gph gph18-2gph15-1gph *11-4gph18-1gph *12-4gph11-2gph *14-4gph14-2gph *16-4gph16-2gph * 13-4gph * 20-4gph

Drip Irrigation Layout Trees, 4 foot radius, 2” water each irrigation = 62 gallons Shrubs, 1 foot radius, 2” water = 4 gallons

3. Irrigation Scheduling When to irrigate – Depth of water in root zone to replace (1” or 2”) – MINUS daily ETo x PF + effective rainfall (inches) – Irrigated when 1” or 2” is used up

Depletion method, not replacement method Day 2, 0.4 inches cum. water loss Day 1, 0.2 inches cum. water loss Day 4, 0.8 inches cum. water loss Night 5, apply 0.8 inches Day 3, 0.6 inches cum. water loss Depletion method OF CHOICE: apply same amount every irrigation, vary day interval based on ET Depletion method healthier for plants, easier

Assume 1” water in root zone, PF=50% of ET Day 1:ET=0.18”; 0.09”use, 0.91” remains Day 2:ET=0.12”; 0.06”use, 0.85” remains Day 3:ET=0.16; 0.08”use, 0.77” remains Day14:ET=0.10”; 0.05”use, 0.02” remains Assume 10 days passed, ET=0.14”/day, 0.07” remaining Day 15:ET=0.08”; 0.04”use, ” remains Day 16: soil water in root zone depleted: irrigate Tree/shrub schedule: for spring or fall

Irrigation Schedule for Woody Plants Along Wasatch Front using Historical ETo

Irrigation Schedule for DesertPlants Along Wasatch Front using Historical ETo

4. WaterMAPS WaterMAPS is USU Extension software to calculate capacity to conserve Capacity to conserve = Landscape irrigation ratio (LIR): Actual use (gallons) ÷ estimated demand (gallons) – Actual use in gallons from water meters – Estimated demand (gallons) = ETo x PF (plant type) x irrigated landscape area (same calculation as in the design stage)

Parcel-scale Landscape Irrigation Ratios (LIRs) Efficient Acceptable Inefficient Excessive Landscape Water Use ___________________ Landscape Water Need LIR = (estimated from analysis of municipal or water provider meter data) ______________________________________ (estimated from classification of remotely-sensed airborne multispectral imagery, localized reference ETo rates modified by Plant Factor for turf, non turf, desert plant types, and policy assumptions) (per unit of landscaped area) 4. WaterMAPS

ASSESS: identify users with capacity to conserve water DELIVER: water use reports to help people conserve TRACK: water use change; monitor actual water savings

WaterMAPS – DELIVER INFORMATION footnotes

4. WaterMAPS - TRACK Is customer saving water Compare LIR before conservation program to LIR after Data at right from Logan City, Good! OK, but could do better Saved, but still too high Something went wrong!

Conclusion ASABE S523 Standard (SLIDE) – valuable tool for estimating water demand Need reliable and trustworthy ETo data Used in these stages of landscape water conservation – Design landscapes to meet water budget/allocation – Drip irrigation layout design to meet water budget – Irrigation scheduling to actual save water – WaterMAPS to assess, educate, and track capacity to conserve (landscape irrigation ratio