Evaporation in Vineyards

Dennis Baldocchi and Youngryel RyuDept Environmental Science, Policy and Management

University of California, Berkeley

November 30, 2010Fruition Sciences Symposium, St. Helena, CA

How Much Water Does a Vineyard Lose to Evaporation?

First Grand Challenges to Vintners and Viticulturalists- Regarding Water Balance of the Vineyards

• Know How Much Water the Vineyard Uses over the Year and During the Growing Season– Give it too much water costs $$$$$ in

terms of irrigating– Give it too little water may cost $$$$ in

terms of reduced yield and grape quality– Give it Optimal Levels of Water will Earn

you $$$$ in terms of producing top quality Grapes and Wine

• Know how to Evaluate Water Use across the Region as a function of:– Climate– Topography– Soil Type– Viticultural Practice, e.g. Varietal,

Planting Density and Age• Water Use of a Vineyard can be

Measured with Micrometeorological Methods

• Water Use of an Appelation can be Modeled by combining Micrometeorological Theory and Remote Sensing

Second Grand Challenges to Vintners and Viticulturalists Regarding Water Balance of the Vineyards

Third Grand, and Ultimate, Challenge• What are these Optimal Levels of Water Use

and How Do We Find Them?• ‘Know Thy Site’

– Simplest and Cheapest• Regular measurements of soil gravimetric

content– Requires scale, oven, shovel and much

replication and sampling

– Easy with Moderate Cost• Regular Measurements of Pre-Dawn Water

Potential– Measures the moisture the Roots See– Invest in ‘Pressure Bomb’, few $K– Requires much sampling and replication

– Most Expensive and Sophisticated• Regular Measurements or Simulations

with Micrometeorological Techniques– Gives you continuous and direct evaporation

measurements at the field scale

Potential Evaporation

• “the evaporation from an extended surface of a short grass that is supplied with water and the canopy covers the ground completely.”

Potential Evaporation in California Wine Regions is Large:4-5 mm/day (0.15-0.2 inch/day)

Annual Grassland, 2004

Day

0 50 100 150 200 250 300 350

E (

MJ

m-2

d-1

)

0

2

4

6

8

10

12

14

Actual LEPotential LE

Potential and Actual Evaporation are Decoupled in Semi-Arid System

The Margin for Error is Tight for Providing Optimal Water to the VineyardET = f(varietal, topography, planting density, soil type, climate, trellising)

?

?

?

E/

Eeq

Enough or Too Much Water

Too

Little

Wat

er

Volume of Water/Volume SoilFrac

tion

of P

oten

tial E

vapo

Tran

spira

tion,

ETa

ctua

l/ET

ref

Baldocchi et al., 2004 AgForMet

soil water potential (MPa)

-5 -4 -3 -2 -1 0

E/ E

eq

0.0

0.2

0.4

0.6

0.8

1.0

predawn water potentialsoil water potential

soil water potential (MPa)

-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0

E/ E

eq

0.00

0.25

0.50

0.75

1.00

1.25

oak savanna

annual grassland

ET and Soil Water Deficits:Water Potential and Evaporation with Native CA Vegetation, Oaks and Grasslands

Root-Weighted Soil Moisture Matches Pre-Dawn Water Potential

Atmosphericradiativetransfer

Canopy photosynthesis,Evaporation, Radiative transfer

Soil evaporation

Beam PAR NIR

Diffuse PAR NIR

Albdeo->Nitrogen -> Vcmax, Jmax

LAI, Clumping-> canopy radiative transfer

dePury & Farquhar two leaf Photosynthesis model

Rnet

Surface conductance

Penman-Monteithevaporation model

Radiation at understory

Soil evaporation

shade sunlit

BESS, Breathing-Earth Science Simulator

Help from ModisAzure -Azure Service for Remote Sensing Geoscience

Scientific Results Download

Reduction #1 Queue

Source Metadata

AzureMODIS Service Web Role Portal

Request Queue

Analysis Reduction Stage

Data Collection Stage

Source Imagery Download Sites

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Reprojection Queue

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Scientists

Science results

AZURE Cloud with 200 CPUs cuts 1 Year of Processing to <2 days

Napa County Wine Districts

Annual Evapotranspiration, Napa County

Leaf Area Grand Growth Start

Leaf Area Grand Growth, End + Bloom

Pre_Veraison Stage

Post Veraison Summer Water Deficits

Case Study 1, Sonoma County

Compare Carneros, Valley of the Moon, Dry Creek, Russian River,

Alexander and Knights Valleys

ET ~ 20 to 30 inches per year

Seasonal Trends in Sonoma County ET

Carneros Greatest in April; Least during the Summer

Conclusions

•Actual EvapoTranspiration is Very Sensitive to Changes in Soil Moisture and Climate, so a Scientific Approach is Warranted to Manage Water Application Best.

•Mechanistic Theories and Satellite Information are Producing Maps of ET at 1 km scale across the Wine Growing Region of California

•New ET Maps can be used for Planning Vineyard Siting, Varietal Selection, Irrigation Management, Vineyard Design

Effects of Leaf Area and Photosynthetic Capacity on Normalized Evaporation:

Well-Watered Conditions

Vcmax*LAI

0 20 40 60 80 100 120 140 160 180 200

QE/Q

E,e

q

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

Canveg Model, Baldocchi and Meyers, 1998 AgForMet

Priestley-Taylor= 1.26

A (mol m-2 s -1)

0 1 2 3 4 5 6 7 8

gs

(mm

ol

m-2

s-1

)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

oak, varying lightCa: 360 ppmTa: 25 C

Stomatal Conductance Scales with Photosynthesis

Wilson et al. 2001, Tree PhysiologySchulze et al 1994. Annual Rev Ecology

Na (g m-2)

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Vcm

ax ( m

ol m

-2 s

-1)

0

20

40

60

80

Photosynthetic Capacity Scales with Nitrogen

after Schulze et al (1994)

leaf nitrogen (mg g- 1̀)

5 10 15 20 25 30 35 40

ma

xim

um

sto

ma

tal

co

nd

uc

tan

ce

(m

m s

-1)

0

2

4

6

8

10

12

14

Stomatal Conductance scales with Nitrogen

Stomatal Conductance Scales with N, via Photosynthesis

MOD04

MOD05

MOD06

MOD07

aerosol

Precipitable water

cloud

Temperature, ozone

MCD43 albedo

MOD11 Skin temperatureAtm

ospheric radiative transfer

Net radiation

MOD15 LAI

POLDER Foliage clumping

Canopy radiativetransfer

Challenge for a Computationally-Challenged Biometeorology Lab:Extracting Data Drivers from Global Remote Sensing to Run the Model

Youngryel was lonely with 1 PC

Residual Energy Balance

• Net Radiometer, NR-Lite: $1600• Soil Heat flux, Hukseflux: $500• Sonic anemometer: RM Young, 81000VRE:

$3200• Data logger: Campbell CR-1000: $1500

• as far as topicThis 2010 vintage has been really puzzling for all vineyard managers and winemakers in the sense that phenological stages were reached either later than usual or in some cases, never (some varietals had berries that never turned red).Everyone "feels" that it is climate related, without really understanding what parameters of the climate are driving those changes. I think that using ET as a way to characterize climate variations is a first step in that direction. Thus, it would be ideal if a cross vintage comparison could be shown so that people understand to which extend 2010 was different from 2009 and 2008 for instance.

Based on your suggestions, here is what I think would be interesting:1. From simple to fancy evaporation estimates measurement methods (it would be best if you could keep it very simple, without complex equations if possible !)2. Effect of evaporation on soil water balance3. Surface renewal and eddy covariance : I would not spend too much time on those for fear of losing the attention; but I think it is good to mention that this is the newest and most promising method with one "punch slide".4. Relationship between normalized Evaporation and soil moisture : this is the central piece! This would be really useful to illustrate how/why different years have different effects on soil moisture. In that part a multi- year comparison would be really relevant (if available).5. Spatial variations of normalized Evaporation : Great! I would highlight within a small geographical area (like Napa valley and Sonoma valley) what is the magnitude of the differences to be expected within a year.6. I would conclude - if possible- with a comparison of the effect that different years vs. different locations within Napa can have on evaporative demand...I think this should be a really interesting way to compare the effect of vintage vs. terroir on plant.

Actual Evaporation

• Aerodynamic Approach• Energy Balance (Bowen Ratio) Approach• Eddy Covariance• Lysimeter• Evaporation Pan• Soil Water Budget• Combination Method

– Penman Equation– Penman-Monteith Equation– Modified Priestly-Taylor Method

• Climatological Methods– Thornthwaite Equation

H

E

1nR G

E

2 1 2 1

2 12 1

( ) ( )

( )( )

v

a

pM

M

C T T T T

e ee e

P

Bowen Ratio Method, measured with temperature and humidity gradients

ESPM 228 Adv Topic Micromet & Biomet

KR G

Cz P

ez

n

a p

( )

R H E Gn

Energy Balance Method

Rn, net radiation flux density, W m-2

H, sensible heat flux densitylE, latent heat flux densityG, soil heat flux densityCp, specific heat of air

http://pages.unibas.ch/geo/mcr/Projects/EBEX/img_profile/profile02.jpg

~ ' 'a aF ws w s

s c

a

( )

Eddy Covariance, Flux Density: mol m-2 s-1 or J m-2 s-1

Time

Tem

per

atu

re

a

l

s

ESPM 228 Adv Topic Micromet & Biomet

Surface Renewal

H Ca

l szp c

Paw U et al., 1989

y = 1.00x

R2 = 0.92

-200

0

200

400

600

-100 0 100 200 300 400 500

H SR (W m-2)

H

(W m

-2)

ESPM 228 Adv Topic Micromet & Biomet

Validation at Vaira Ranch

D346Vaira Grassland

Time (hours)

600 800 1000 1200 1400 1600 1800

H (

W m

-2)

-50

0

50

100

150

200

250

Eddy Cov

sfc renewal

ESPM 228 Adv Topic Micromet & Biomet

Sfc Renewal

Relatively Cheap and SimpleNeeds Calibration for your Site or Class

soil water potential (MPa)

-5 -4 -3 -2 -1 0

E/ E

eq

0.0

0.2

0.4

0.6

0.8

1.0

predawn water potentialsoil water potential

soil water potential (MPa)

-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0

E/ E

eq

0.00

0.25

0.50

0.75

1.00

1.25

oak savanna

annual grassland

Baldocchi et al., 2004 AgForMet

soil water potential (MPa)

-5 -4 -3 -2 -1 0

E/ E

eq

0.0

0.2

0.4

0.6

0.8

1.0

predawn water potentialsoil water potential

soil water potential (MPa)

-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0

E/ E

eq

0.00

0.25

0.50

0.75

1.00

1.25

oak savanna

annual grassland

ET and Soil Water Deficits:Water Potential and Evaporation with Native CA Vegetation, Oaks and Grasslands

Root-Weighted Soil Moisture Matches Pre-Dawn Water Potential

ET of Annual Grass responds to water deficits differently than Trees

Grassland

weighted by roots (cm3 cm-3)

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

E/ E

eq

0.00

0.25

0.50

0.75

1.00

1.25

summer rain

Oak Savanna

weighted by roots(cm3 cm-3)

0.00 0.05 0.10 0.15 0.20 0.25 0.30

E/ E

eq

0.0

0.2

0.4

0.6

0.8

1.0

ET and Soil Water Deficits:Root-Weighted Soil Moisture

Baldocchi et al., 2004 AgForMet

Grassland

weighted by roots (cm3 cm-3)

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

E/ E

eq

0.00

0.25

0.50

0.75

1.00

1.25

summer rain

Oak Savanna

weighted by roots(cm3 cm-3)

0.00 0.05 0.10 0.15 0.20 0.25 0.30

E/ E

eq

0.0

0.2

0.4

0.6

0.8

1.0

Pellegrino et al 2004, Plant and Soil

Southern France, Syrah

Grapes are Much More Sensitive to Soil Water Deficits than Native Oaks and Grasses

Williams et al. 2003 Irrigation Sci

ET Thompson Seedless, Fresno