Understanding Irrigation Crop ET Estimates: Workshop Insights

Explore the calibration process for historical crop ET estimates discussed by Ivan A. Walter, P.E. The workshop delves into the accuracy of Kc vs. SCS BC, reasons for not using Kc ETstzd, desirable results for accurate ET calculations, ASCE Task Committee criteria, and real-world examples like Rocky Ford and Fort Morgan. Dive into the methods for processing raw data to calculate ETrs, ETos, and ETHrgv. Discover the importance of measurement accuracy, data selection, and calibration in this detailed workshop.

• Irrigation
• Workshop
• Crop ET
• Calibration
• Accuracy

area290 Follow

Uploaded on Oct 07, 2024 | 0 Views

Download Presentation

Please find below an Image/Link to download the presentation.

The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author. Download presentation by click this link. If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.

Presentation Transcript

1. EVAPOTRANSPIRATION WORKSHOP Calibration for Historical Crop ET Estimates A Process Ivan A. Walter, P.E. Ivan s Engineering, Inc. 3/12/2010 Ivan A. Walter, P.E. 1

2. Kc 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. 2

3. Why Isnt 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. 3

4. What 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. 4

5. 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. 5

6. Rocky Ford ETrs 12 10 ETrs ETrs Est 8 6 4 2 0 Apr May Jun Jul Aug Sep 3/12/2010 Ivan A. Walter, P.E. 6

7. Rocky Ford: Est as % of Actual 110% ETrs Est /: ETrs ETos Est / ETos 105% 100% 95% 90% 85% 80% May Jun Jul Aug Sep 3/12/2010 Ivan A. Walter, P.E. 7

8. Fort Morgan -- 2005 Daily Data 0.6 ETrs 0.5 ETrs Est 0.4 inches 0.3 0.2 0.1 0 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep 1-Oct 3/12/2010 Ivan A. Walter, P.E. 8

9. Raw 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. 9

10. Begin Here Standardized Reference ET Equation: C + + n . 0 408 ( ) ( ) R G u e e 2 n s a 273 u T = ET ref + + 1 ( ) C 2 d 3/12/2010 Ivan A. Walter, P.E. 10

11. Begin Here w/ Data from Web 3/12/2010 Ivan A. Walter, P.E. 11

12. Calculate & Analyze & Compare Standardized Reference ET Equation: C + + n . 0 408 ( ) ( ) R G u e e 2 n s a 273 u T = ET ref + + 1 ( ) C 2 d 1985 Hargreaves Equation: = + 5 . 0 0023 . 0 ( ) mean T ( 17 ) 8 . ET T T R max min o a 3/12/2010 Ivan A. Walter, P.E. 12

13. Final Product Standardized Reference ET values Short Crop: ETos Tall Crop: ETrs Daily values 3/12/2010 Ivan A. Walter, P.E. 13

14. Step 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. 14

15. Step 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. 15

16. Step 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. 16

17. Step 3 Results: Ratio ETrs : ETHrgv MAY JUN JUL AUG SEP Fort Morgan(Tdpt Adjusted) 1995 - 2006 Fort Collins 03 1999 - 2006 1.40 1.36 1.27 1.25 1.37 1.48 1.41 1.38 1.38 1.56 1.54 1.38 1.15 1.18 1.47 1.30 1.33 1.22 1.16 1.22 1.32 1.36 1.22 1.17 1.17 1.58 1.54 1.34 1.28 1.47 1.34 1.28 1.15 1.13 1.21 1.31 1.29 1.22 1.24 1.36 Center 1996 - 2006 Avondale 1994 - 2008 Rocky Ford 1994 -2008 Yuma 1996 - 2006 Fruita 1999 2006 Yellow Jacket 1992 - 2008 3/12/2010 Ivan A. Walter, P.E. 17

18. Results @ Center: Ratio ETrs : ETHrgv MAY 1.54 1.68 1.31 1.62 1.56 1.43 1.45 1.56 1.50 1.61 1.54 1.57 JUN 1.38 1.25 1.32 1.56 1.43 1.30 1.35 1.36 1.38 1.38 1.44 1.43 JUL 1.15 1.06 1.16 1.08 1.09 1.11 1.07 1.15 1.21 1.23 1.24 1.17 AUG 1.18 1.14 1.06 1.15 1.12 1.17 1.15 1.23 1.17 1.37 1.26 1.15 SEP 1.47 1.47 1.25 1.48 1.38 1.57 1.52 1.34 1.48 1.56 1.57 1.47 All 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 3/12/2010 Ivan A. Walter, P.E. 18

19. Step 3 Results: Ratio ETos : ETHrgv MAY JUN JUL AUG SEP Fort Morgan(Tdpt Adjusted) 1995 - 2006 Fort Collins 03 1999 - 2006 1.02 1.01 0.96 0.96 1.00 1.07 1.03 1.03 1.03 1.10 1.15 1.06 0.93 0.94 1.09 1.03 1.01 0.94 0.93 0.99 1.04 1.04 0.94 0.94 0.95 1.14 1.13 1.03 0.99 1.07 1.00 0.97 0.90 0.88 0.91 1.01 1.01 0.98 0.99 1.05 Center 1996 - 2006 Avondale 1994 - 2008 Rocky Ford 1994 -2008 Yuma 1996 - 2006 Fruita 1999 2006 Yellow Jacket 1992 - 2008 3/12/2010 Ivan A. Walter, P.E. 19

20. Step 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. 20

21. Step 4: COEFHGRV.dat 3/12/2010 Ivan A. Walter, P.E. 21

22. Step 4: ETRETOH 2.exe Calculation of ETrs & ETos using 1985 Hargreaves ETrs = COEF x ETHgrv (Daily) ETos = COEF1 x ETHgrv (Daily) = + 5 . 0 . 0 0023 ( ) mean T ( 17 ) 8 . ET T T R max min o a 3/12/2010 Ivan A. Walter, P.E. 22

23. Step 4: Final Results Year, DOY, Month, Day, ETrs,ETos, Precip. 3/12/2010 Ivan A. Walter, P.E. 23

24. Ft Morgan ETrs 9 ETrs ETrs Est 8 7 6 5 4 3 2 1 0 Apr May Jun Jul Aug Sep 3/12/2010 Ivan A. Walter, P.E. 24

25. Center ETrs 8 ETrs ETrs Est 7 6 5 4 3 2 1 0 Apr May Jun Jul Aug Sep 3/12/2010 Ivan A. Walter, P.E. 25

26. Yuma2 ETrs 12 ETrs ETrs Est 10 8 6 4 2 0 Apr May Jun Jul Aug Sep 3/12/2010 Ivan A. Walter, P.E. 26

27. Rocky Ford ETrs 12 ETrs ETrs Est 10 8 6 4 2 0 Apr May Jun Jul Aug Sep 3/12/2010 Ivan A. Walter, P.E. 27

28. Avondale ETrs 12 ETrs ETrs Est 10 8 6 4 2 0 Apr May Jun Jul Aug Sep 3/12/2010 Ivan A. Walter, P.E. 28

29. Fruita ETrs 12 ETrs ETrs Est 10 8 6 4 2 0 Apr May Jun Jul Aug Sep 3/12/2010 Ivan A. Walter, P.E. 29

30. Yellow Jacket ETrs 10 9 ETrs ETrs Est 8 7 6 5 4 3 2 1 0 Apr May Jun Jul Aug Sep 3/12/2010 Ivan A. Walter, P.E. 30

31. CoAgMet Stations Years 8 - 11 12 - 14 15 - 18 0 - 4 COW01 0.4 ILF01 1.9 HXT01 12.7 WLT01 4.4 ALT01 17.8 5 - 7 FTC03 17.6 BRG01 7.4 HYK02 18 HEB01 0.3 LCN01 17.8 PAI01 8.2 GLY04 1.5 FTC01 17.9 WGG01 7.6 FTM01 14.7 KSY01 17.6 WGG02 8.3 STG01 3.7 YUM02 13.6 AKR02 17.5 WRY01 13.6 PTV01 0 WFD01 5.1 YUM01 8 FTL01 17.8 HRT01 2.7 EAC01 9.4 IDL01 18 KRK01 13.6 BRL01 17.6 BRL03 1.7 BRL02 17.4 STN01 3.7 FRT02 17.5 FRT01 ORM01 4 GJC01 15.6 CDG01 3.8 PAN01 0 HOT01 11.6 DLT01 14.7 OTH01 17.4 SCM01 1.4 VLD01 16.4 PBL01 1.8 LAM02 2.9 LAM04 4.6 LMS01 4.8 FWL01 4.8 RFD02 6.5 AVN01 17.5 HLY02 4.6 HLY01 8.2 LJT01 4.8 LAM03 7.4 LAM01 13.4 RFD01 17.5 CTR02 6.2 CTR01 16.2 DVC01 17.1 YJK01 18 BLA01 11.6 YUC01 7.3 TWC01 11.5 HNE01 9.8 CTZ01 18 LJR01 4.1 STT01 1.8 SAN01 9.4 3/12/2010 Ivan A. Walter, P.E. 31

32. Process -- 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. 32

33. Meadow Grass ET Review of Methods Recommendation for Calculation ETc 3/12/2010 Ivan A. Walter, P.E. 33

34. Reported 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. 34

35. Reported 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. 35

36. 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. 36

37. Hargreaves Kcs for Meadow Grass Multiple Sites -- 5 years of data May = June = July = August = September = 1.16 1.28 1.04 0.86 0.88 3/12/2010 Ivan A. Walter, P.E. 37

38. Meadow Grass Kc -- Derived using Calibrated Hargreaves 3/12/2010 Ivan A. Walter, P.E. 38

39. Software & 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. 39

40. CoAgMet Stations Years 8 - 11 12 - 14 15 - 18 0 - 4 COW01 0.4 ILF01 1.9 5 - 7 HXT01 12.7 WLT01 4.4 ALT01 17.8 FTC03 17.6 BRG01 7.4 HYK02 18 HEB01 0.3 LCN01 17.8 PAI01 8.2 GLY04 1.5 FTC01 17.9 WGG01 7.6 FTM01 14.7 KSY01 17.6 WGG02 8.3 STG01 3.7 YUM02 13.6 AKR02 17.5 WRY01 13.6 PTV01 0 WFD01 5.1 YUM01 8 FTL01 17.8 HRT01 2.7 EAC01 9.4 IDL01 18 KRK01 13.6 BRL01 17.6 BRL03 1.7 BRL02 17.4 STN01 3.7 FRT02 17.5 FRT01 ORM01 4 GJC01 15.6 CDG01 3.8 PAN01 0 HOT01 11.6 DLT01 14.7 OTH01 17.4 SCM01 1.4 VLD01 16.4 PBL01 1.8 LAM02 2.9 LAM04 4.6 LMS01 4.8 FWL01 4.8 RFD02 6.5 AVN01 17.5 HLY02 4.6 HLY01 8.2 LJT01 4.8 LAM03 7.4 LAM01 13.4 RFD01 17.5 CTR02 6.2 CTR01 16.2 DVC01 17.1 YJK01 18 BLA01 11.6 YUC01 7.3 TWC01 11.5 HNE01 9.8 CTZ01 18 LJR01 4.1 STT01 1.8 SAN01 9.4 3/12/2010 Ivan A. Walter, P.E. 40