“Operational Evapotranspiration Data for Water Management in the Western U.S.” by Matt Bromley at the 2023 Water for Food Global Conference. A recording of the presentation can be found on the conference playlist: https://youtube.com/playlist?list=PLSBeKOIXsg3JNyPowwJj6NDSpx4vlnCYj.

1. Operational Evapotranspiration Data for Water Management in the Western U.S.

2. Environmental Defense Fund Robyn Grimm, Maurice Hall, Rachel O’Connor, Garshaw Amidi-Abraham
NASA Ames, DRI, Habitat Seven (Multi-model Development, Integration, API, UI) Forrest Melton, Justin Huntington, Jamie
Herring, Charles Morton, Britta Daudert, Alberto Guzman, Jody Hansen, Jordan Harding, Matt Bromley, Blake Minor, Thomas Ott, Christian
Dunkerley
USDA, NASA Marshall Space Flight Center, U. Maryland (ALEXI/DisALEXI) Martha Anderson, Yun Yang, Christopher Hain,
Yanghui Kang
Federal University of Rio Grande do Sul (geeSEBAL) Anderson Ruhoff, Leonardo Laipelt, Rafael Kayser
U. of Nebraska, U. of Idaho, DRI (EE METRIC) Ayse Kilic, Rick Allen, Peter Revelle, Samuel Ortega
NASA JPL, UCLA (PT JPL) Josh Fisher, Gregory Halverson
NASA Ames, CSUMB, Stanford University (SIMS) Forrest Melton, Lee Johnson, Will Carrara, Alberto Guzman, Conor Doherty
USGS (SSEBop) Gabriel Senay, MacKenzie Friedrichs, Gabe Parrish
Google Earth Engine Tyler Erickson
The Team

3. Evapotranspiration and Consumptive Use
Water applied to a field ultimately:
Evaporates
Transpires (after being used by plants to grow)
Recharges underlying groundwater
Runs off and returns to a local canal or river

4. Credit: John Locher, AP
Measuring ET enables:
Development of realistic water budgets
Incentives for conservation and innovation
Proper credit for reduced use
Reduced transaction costs for water trading programs
Increased on-farm efficiencies

13. OpenET Uses Well-Established Methods
geeSEBAL
UFRGS

14. Model Ensemble: Median Absolute Deviation (MAD)
Outlier Detection

15. OpenET Uses Data from a Constellation of Satellites
USGS-NASA Landsat 5/7/8/9
(TM / ETM+ / OLI)
30m/0.22 acres | overpass every 8-16 days
ESA Sentinel-2A, 2B
20m/0.1 acres | overpass every 5-10 days
NASA Terra / Aqua
1 km | daily overpass
NASA-NOAA Suomi NPP
~300-375m | daily overpass
NOAA GOES-15/16/17
0.5-4 km | < hourly
Image credit: NASA/Goddard Space Flight Center Conceptual Image Lab

16. OpenET Architecture Overview

17. OpenET API for Integration with Other Software

18. Intercomparison and Accuracy Assessment
Phase I comparison complete (70 flux tower sites)
Phase II complete with 72 additional flux tower sites
Melton et al., JAWRA, (2021)
https://openetdata.org/accuracy

19. OpenET Accuracy Assessment: Croplands
Accuracy Summary for Croplands for the OpenET Ensemble ET Value
Time Period Slope Mean Bias
Error
Mean Absolute
Error
Root Mean
Squared Error
r-squared Mean flux
tower ET
Water Year:
14 sites with 48 total
water years)
0.93 -71.6 mm
(-7.0%)
91.3 mm
(8.9%)
100.5 mm
(9.8%)
0.90 1024 mm
Growing Season: 38
sites with 151 growing
seasons
1.0 -10.1 mm (-
1.7%)
80.3 mm
(13.2%)
92.7 mm
(15.2%)
0.88 609.5 mm
Monthly:
45 sites with 1,682 total
months
0.95 -3.6 mm
(-3.9%)
15.6 mm
(16.6%)
20.0 mm
(21.3%)
0.91 93.7 mm
Daily:
49 sites with 4,804 total
days
0.88 -0.3 mm
(-7.4%)
0.8 mm
(22.8%)
1. 1 mm
(29.7%)
0.81 3.6 mm
Also see Volk et al. (H53D-03); Reitz et al. (H53D-04);
Melton et al. (2021)
https://openetdata.org/accuracy

20. +/- 6%
Phase I Results for Cropland Sites
Fig. 1: Model agreement with flux towers
for croplands (growing season; n = 15 sites)
Fig. 2: Model agreement with flux towers for
croplands (full year; n = 10 sites)
+/- 9%
n = 24 sites
(827 months)
Monthly ET,
Ensemble Mean
Monthly ET,
Ensemble range
Slope 0.97 0.91 – 1.03
MAE (mm/month) 15.4 15.4 – 22.4
RMSE (mm/month) 19.6 19.6 - 28.3
R-squared 0.94 0.84 - 0.94
n = 24 sites
(3,043 days)
Daily ET,
Ensemble Mean
Daily ET,
Ensemble range
Slope 0.93 0.84 – 0.98
MAE (mm/day) 0.77 0.77 – 1.04
RMSE (mm/day) 1.01 1.01 – 1.36
R-squared 0.89 0.75 - 0.89

21. Coming Down the Pipeline
● Public launch of API
● Custom reporting
● Geographic expansion
● Daily data
● Forecasting
● Furthering the science

22. Fusion of ECOSTRESS LST with Landsat
● ECOSTRESS LST
○ 70 x 70 m resolution
○ Multiple overpasses per day
● Short-wave reflectance data from close-in-time Landsat images
○ 30 m spatial resolution
○ 8-day overpass imagery
● Challenges
○ Correct for time of day and geolocation
● Improved Temporal resolution of eeMETRIC

23. Irrigation Management Software Enabled by OpenET
https://cropmanage.ucanr.edu/
Dr. Michael Cahn
UCANR CropManage

24. User Review and Control of Satellite Inputs

25. Thank You!
Please visit https://openetdata.org for more information.
OpenET gratefully acknowledges support from the
Walton Family Foundation; the Gordon and Betty
Moore Foundation; Lyda Hill Philanthropies; the S.D.
Bechtel, Jr. Foundation; the Windward Fund; the Keith
Campbell Foundation for the Environment; the North,
Central, and South Delta Water Agencies; the NASA
Applied Science Program and the NASA Western Water
Applications Office; the USGS Landsat Science Team;
and the California State University Agricultural
Research Institute