Ivan A. Walter, P.E. 1

Calibration for Historical Crop ET Estimates – A Process

Ivan A. Walter, P.E.

Ivan’s Engineering, Inc.

EVAPOTRANSPIRATION WORKSHOP

3/12/2010

Ivan A. Walter, P.E. 2

Kc ETstzd vs SCS BCKc ETstzd vs SCS BC

Kc ETstzd is more accurate than SCS BC– Kc -- Generate from measurement at known sites– Kc -- Transferrable– ETstzd – ET professional & researchers have

accepted– SCS BC – Crop Coefficients derived where???– SCS BC – Requires local calibration

3/12/2010

Ivan A. Walter, P.E. 3

Why Isn’t Kc ETstzd UsedWhy Isn’t Kc ETstzd Used Answers to “Why not?”

– SCS BC is well accepted in Colo. Water Court.

– Do not have the data for ETstzd – Do not have the Kc’s

3/12/2010

Ivan A. Walter, P.E. 4

What is Desirable ResultWhat is Desirable Result Just some number for ETc Accurate daily Temp, Rs, U, & Rh Accurate daily ETrs & ETos

Accurate monthly ETrs & ETos

Excel files & Programs for analysis

3/12/2010

Ivan A. Walter, P.E. 5

Criteria (ASCE Task Committee)Criteria (ASCE Task Committee)

Understandable Defensible Simplification without loss of accuracy Based on & Traceable to Experimental

Data

3/12/2010

Ivan A. Walter, P.E. 6

3/12/2010

Apr May Jun Jul Aug Sep0

2

4

6

8

10

12

Rocky Ford ETrs

ETrs ETrs Est

Ivan A. Walter, P.E. 73/12/2010

May Jun Jul Aug Sep80%

85%

90%

95%

100%

105%

110%

Rocky Ford: Est as % of Actual

ETrs Est /: ETrs ETos Est / ETos

Ivan A. Walter, P.E. 83/12/2010

1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep 1-Oct0

0.1

0.2

0.3

0.4

0.5

0.6

Fort Morgan -- 2005 Daily Data

ETrs

ETrs Est

inch

es

Ivan A. Walter, P.E. 9

Raw Data >>>>>> ETcRaw Data >>>>>> ETc

Download data from Web site QC the data – Select good data Calc ETrs, ETos, and ETHrgv

Calibration Calc’s with good data COEFHgrv x ETHrgv = ETrs COEF1Hgrv x ETHrgv = ETos

3/12/2010

Ivan A. Walter, P.E. 10

)1(

)(273

)(408.0

2

2

uC

eeuT

CGR

ETd

asn

n

ref

Begin Here

Standardized Reference ET Equation:

3/12/2010

Ivan A. Walter, P.E. 11

Begin Here w/ Data from Web

3/12/2010

Ivan A. Walter, P.E. 12

)1(

)(273

)(408.0

2

2

uC

eeuT

CGR

ETd

asn

n

ref

Calculate & Analyze & Compare

Standardized Reference ET Equation:

3/12/2010

ameano RTTTET )8.17()(0023.0 5.0minmax

1985 Hargreaves Equation:

Ivan A. Walter, P.E. 13

Final ProductFinal Product

Standardized Reference ET values– Short Crop: ETos– Tall Crop: ETrs– Daily values

3/12/2010

Ivan A. Walter, P.E. 14

Step 1: XXX COAG.xlsStep 1: XXX COAG.xls

Download data from COAGMet site QC the data

– Identify the Good Data– Fix small gaps & errors– Throw out everything else

3/12/2010

Ivan A. Walter, P.E. 15

Step 2: ColCrbt2.exe -- ApplicationStep 2: ColCrbt2.exe -- Application

Input data from XXX COAG.xls– Text file XXXEtrData.prn

Calculates Reference ET (daily)– ETrs– ASCE PM Etr, 1982 Kimberly Penman ETr– ETos– ASCE PM ETo, Hargreaves ETo

3/12/2010

Ivan A. Walter, P.E. 16

Step 3: Colcrbt2.exe -- ResultsStep 3: Colcrbt2.exe -- Results

Linear Regression Analysis (daily) Zero intercept Monthly Ratio: ETrs to ETHgrv

Monthly Ratio: ETos to ETHgrv

Monthly Ratio: ETrs to ETos Regression Coef & SEE

3/12/2010

Ivan A. Walter, P.E. 17

Step 3 Results: Ratio ETrs : ETHrgvStep 3 Results: Ratio ETrs : ETHrgv

3/12/2010

MAY JUN JUL AUG SEPFort Morgan(Tdpt Adjusted) 1995 - 2006 1.40 1.36 1.27 1.25 1.37Fort Collins 03 1999 - 2006 1.48 1.41 1.38 1.38 1.56Center 1996 - 2006 1.54 1.38 1.15 1.18 1.47Avondale 1994 - 2008 1.30 1.33 1.22 1.16 1.22Rocky Ford 1994 -2008 1.32 1.36 1.22 1.17 1.17Yuma 1996 - 2006 1.58 1.54 1.34 1.28 1.47Fruita 1999 2006 1.34 1.28 1.15 1.13 1.21Yellow Jacket 1992 - 2008 1.31 1.29 1.22 1.24 1.36

Ivan A. Walter, P.E. 18

Results @ Center: Ratio ETrs : ETHrgvResults @ Center: Ratio ETrs : ETHrgv

3/12/2010

MAY JUN JUL AUG SEPAll 1.54 1.38 1.15 1.18 1.47

1996 1.68 1.25 1.06 1.14 1.471997 1.31 1.32 1.16 1.06 1.251998 1.62 1.56 1.08 1.15 1.481999 1.56 1.43 1.09 1.12 1.382000 1.43 1.30 1.11 1.17 1.572001 1.45 1.35 1.07 1.15 1.522002 1.56 1.36 1.15 1.23 1.342003 1.50 1.38 1.21 1.17 1.482004 1.61 1.38 1.23 1.37 1.562005 1.54 1.44 1.24 1.26 1.572006 1.57 1.43 1.17 1.15 1.47

Ivan A. Walter, P.E. 19

Step 3 Results: Ratio ETos : ETHrgvStep 3 Results: Ratio ETos : ETHrgv

3/12/2010

MAY JUN JUL AUG SEPFort Morgan(Tdpt Adjusted) 1995 - 2006 1.02 1.01 0.96 0.96 1.00Fort Collins 03 1999 - 2006 1.07 1.03 1.03 1.03 1.10Center 1996 - 2006 1.15 1.06 0.93 0.94 1.09Avondale 1994 - 2008 1.03 1.01 0.94 0.93 0.99Rocky Ford 1994 -2008 1.04 1.04 0.94 0.94 0.95Yuma 1996 - 2006 1.14 1.13 1.03 0.99 1.07Fruita 1999 2006 1.00 0.97 0.90 0.88 0.91Yellow Jacket 1992 - 2008 1.01 1.01 0.98 0.99 1.05

Ivan A. Walter, P.E. 20

Step 4: ETRETOH 2.exeStep 4: ETRETOH 2.exe

Calculate ETrs & ETos using ETHgrv

Input File– DataT&P.prn from XXX COAG.xls

Latitude, Tmax, Tmin, Tavg– COEFHRGV.dat

Monthly Coefficient all Station (15 max.)

3/12/2010

Ivan A. Walter, P.E. 21

Step 4: COEFHGRV.datStep 4: COEFHGRV.dat

3/12/2010

Ivan A. Walter, P.E. 22

Step 4: ETRETOH 2.exeStep 4: ETRETOH 2.exe

Calculation of ETrs & ETos using 1985 Hargreaves

ETrs = COEF x ETHgrv (Daily) ETos = COEF1 x ETHgrv (Daily)

3/12/2010

ameano RTTTET )8.17()(0023.0 5.0minmax

Ivan A. Walter, P.E. 23

Step 4: Final ResultsStep 4: Final Results

Year, DOY, Month, Day, ETrs,ETos, Precip.

3/12/2010

Ivan A. Walter, P.E. 243/12/2010

Apr May Jun Jul Aug Sep0

1

2

3

4

5

6

7

8

9 Ft Morgan ETrs

ETrs ETrs Est

Ivan A. Walter, P.E. 253/12/2010

Apr May Jun Jul Aug Sep0

1

2

3

4

5

6

7

8 Center ETrs

ETrs ETrs Est

Ivan A. Walter, P.E. 263/12/2010

Apr May Jun Jul Aug Sep0

2

4

6

8

10

12 Yuma2 ETrs

ETrs ETrs Est

Ivan A. Walter, P.E. 273/12/2010

Apr May Jun Jul Aug Sep0

2

4

6

8

10

12

Rocky Ford ETrs

ETrs ETrs Est

Ivan A. Walter, P.E. 283/12/2010

Apr May Jun Jul Aug Sep0

2

4

6

8

10

12Avondale ETrs

ETrs ETrs Est

Ivan A. Walter, P.E. 293/12/2010

Apr May Jun Jul Aug Sep0

2

4

6

8

10

12 Fruita ETrs

ETrs ETrs Est

Ivan A. Walter, P.E. 303/12/2010

Apr May Jun Jul Aug Sep0

1

2

3

4

5

6

7

8

9

10Yellow Jacket ETrs

ETrs ETrs Est

Ivan A. Walter, P.E. 313/12/2010

FRT01

PTV01 0

PAN01 0

ORM01 4

YUM01 8

YJK01 18

IDL01 18

HYK02 18

CTZ01 18

HEB01 0.3

COW01 0.4

SCM01 1.4

GLY04 1.5

BRL03 1.7

STT01 1.8

PBL01 1.8

ILF01 1.9

HRT01 2.7

LAM02 2.9

STN01 3.7

STG01 3.7

CDG01 3.8

LJR01 4.1

WLT01 4.4

LAM04 4.6HLY02 4.6LMS01 4.8LJT01 4.8

FWL01 4.8

WFD01 5.1

CTR02 6.2

RFD02 6.5

YUC01 7.3

LAM03 7.4

BRG01 7.4

WGG01 7.6

PAI01 8.2

HLY01 8.2

WGG02 8.3

SAN01 9.4

EAC01 9.4

HNE01 9.8TWC01 11.5

HOT01 11.6

BLA01 11.6

HXT01 12.7

LAM01 13.4

YUM02 13.6WRY01 13.6

KRK01 13.6

FTM01 14.7

DLT01 14.7

GJC01 15.6

CTR01 16.2

VLD01 16.4

DVC01 17.1

OTH01 17.4

BRL02 17.4FRT02 17.5

RFD01 17.5AVN01 17.5

AKR02 17.5

KSY01 17.6

FTC03 17.6

BRL01 17.6

LCN01 17.8

FTL01 17.8

ALT01 17.8

FTC01 17.9

CoAgMet Stations

Years

0 - 4

5 - 7

8 - 11

12 - 14

15 - 18

Ivan A. Walter, P.E. 32

Process -- Historical ETref EstimatesProcess -- Historical ETref Estimates

CoAgMet Data XXX COAG.xls -- QC for Good data Colcrbt2.exe -- Cal’c Monthly Hgrv

Factors ETRETOH 2.exe - Calculate ETrs & ETos

3/12/2010

Ivan A. Walter, P.E. 33

Meadow Grass ET

Review of Methods Recommendation for Calculation ETc

3/12/2010

Ivan A. Walter, P.E. 34

Reported ProceduresReported Procedures

SCS –BC Pasture Grass– 10% / 1,000 m. change in elevation– ASCE Manual 70 does not recommend

Pochop Method -- ASAE 1984– Limited to Alfalfa (9%) & Turf (6%)– Adjusted kt --- thus not true SCS BC– Adjust from elevation Coefficient derived– Wyoming

3/12/2010

Ivan A. Walter, P.E. 35

Reported ProceduresReported Procedures

Denver Water Board, BC “k” coef.– South Park, Elev. 8,900 ft msl– Standard BC not modified BC– Local calibration– ET calculated as:

Lysimeter water use + Precipitation (100%)

– ETirr wtr = ETc - Precipitation

3/12/2010

Ivan A. Walter, P.E. 36

Recommend Transferrable Kc Recommend Transferrable Kc

Smith’s Gunnison basin – Hargreaves Monthly Coefficients– Letter Describing included in Materials

Maly & Walter – Kc’s Meadow Grass– Memo Describing process included in Materials

3/12/2010

Ivan A. Walter, P.E. 37

Hargreaves Kc’s for Meadow GrassHargreaves Kc’s for Meadow Grass

Multiple Sites -- 5 years of data May = 1.16 June = 1.28 July = 1.04 August = 0.86 September = 0.88

3/12/2010

Ivan A. Walter, P.E. 383/12/2010

Meadow Grass Kc -- Derived using Calibrated Hargreaves

Ivan A. Walter, P.E. 39

Software & Documents ProvidedSoftware & Documents Provided

XXX COAG.xls -- QC data Colcrbt2.exe -- Calc’ Monthly Coef. ETRETOH 2.exe -- Calc’ ETrs & ETos Example Input and Output files Memo: Coefficients for Meadow Grass Smith Letter: Hargreaves Kc M.Grass Daily Ra calculation Application

3/12/2010

Ivan A. Walter, P.E. 403/12/2010

FRT01

PTV01 0

PAN01 0

ORM01 4

YUM01 8

YJK01 18

IDL01 18

HYK02 18

CTZ01 18

HEB01 0.3

COW01 0.4

SCM01 1.4

GLY04 1.5

BRL03 1.7

STT01 1.8

PBL01 1.8

ILF01 1.9

HRT01 2.7

LAM02 2.9

STN01 3.7

STG01 3.7

CDG01 3.8

LJR01 4.1

WLT01 4.4

LAM04 4.6HLY02 4.6LMS01 4.8LJT01 4.8

FWL01 4.8

WFD01 5.1

CTR02 6.2

RFD02 6.5

YUC01 7.3

LAM03 7.4

BRG01 7.4

WGG01 7.6

PAI01 8.2

HLY01 8.2

WGG02 8.3

SAN01 9.4

EAC01 9.4

HNE01 9.8TWC01 11.5

HOT01 11.6

BLA01 11.6

HXT01 12.7

LAM01 13.4

YUM02 13.6WRY01 13.6

KRK01 13.6

FTM01 14.7

DLT01 14.7

GJC01 15.6

CTR01 16.2

VLD01 16.4

DVC01 17.1

OTH01 17.4

BRL02 17.4FRT02 17.5

RFD01 17.5AVN01 17.5

AKR02 17.5

KSY01 17.6

FTC03 17.6

BRL01 17.6

LCN01 17.8

FTL01 17.8

ALT01 17.8

FTC01 17.9

CoAgMet Stations

Years

0 - 4

5 - 7

8 - 11

12 - 14

15 - 18