A Comparative Analysis of OpenET for Evaluating Evapotranspiration in California Almond Orchards

Authors

Kyle Knipper, USDA ARS Sustainable Agricultural Water Systems
Martha Anderson, USDA ARS Hydrology and Remote Sensing Lab
Nicholas Bambach, University of California, Davis
Forrest Melton, NASA Ames Research Center
Zac Ellis, Olam Food Ingredients
Yun Yang, Mississippi State University
John Volk, Desert Research Institute
Andrew J. McElrone, University of California, Davis
William Kustas, USDA ARS Hydrology and Remote Sensing Lab
Matthew Roby, USDA ARS Sustainable Agricultural Water Systems
Will Carrara, NASA Ames Research Center
Sebastian Castro, University of California, Davis
Ayse Kilic, University of Nebraska-Lincoln
Joshua B. Fisher, Chapman UniversityFollow
Anderson Ruhoff, Universidade Federal do Rio Grande de Sul
Gabriel B. Senay, U.S. Geological Survey Earth Resources Observation and Science Center
Charles Morton, Desert Research Institute
Sebastian Saa, Almond Board of California
Richard G. Allen, University of Idaho

Document Type

Article

Publication Date

7-3-2024

Abstract

The almond industry in California faces water management challenges that are being exacerbated by droughts, climate change, and groundwater sustainability legislation. The Tree-crop Remote sensing of Evapotranspiration eXperiment (T-REX) aims to explore opportunities to improve precision irrigation management for woody perennial cropping systems. Almond orchards in the California Central Valley were equipped with eddy covariance flux measurements to evaluate satellite remote sensing-based evapotranspiration (RSET) models. OpenET provides high-resolution (30-m spatial and daily temporal) RSET data, synthesizing decades of research for practical water management. This study provides an evaluation of OpenET performance at six almond sites covering a large range in soils, age, and variety. It also compares OpenET ensemble evapotranspiration (ET) data with applied irrigation and precipitation records over an additional 148 almond orchards located in the Central Valley of California. Results show OpenET models, including the ensemble ET value, produced reasonable and actionable ET values, with overall coefficient of determination (R²) and mean absolute error values of 0.73- and 0.95-mm d⁻¹ at the daily time step, respectively. However, given the temporal sampling of Landsat (8-day revisit) and the interpolation methods used, the assessed ET models had difficulty in capturing short-term variability in almond ET; for example, the rapid decline in measured ET observed as a response to lack of irrigation preceding and during almond harvest. The study also drew attention to the spatial complexity in scenarios where irrigated orchards are surrounded by hot/dry areas, causing discrepancies between measured and modeled ET values. In comparison with irrigation records, OpenET ensemble ET was capable of quantifying water input (applied irrigation + precipitation) in almond orchards to within 13 % when evaluating monthly data. Initial results presented here reinforce the idea that RSET models, such as in OpenET, are powerful tools, yet their application requires nuanced understanding and careful consideration of local conditions.

Comments

This article was originally published in Agricultural and Forest Meteorology, volume 355, in 2024. https://doi.org/10.1016/j.agrformet.2024.110146

Recommended Citation

Knipper, K., Anderson, M., Bambach, N., Melton, F., Ellis, Z., Yang, Y., Volk, J., McElrone, A.J., Kustas, W., Roby, M., Carrara, W., Castro, S., Kilic, A., Fisher, J.B., Ruhoff, A., Senay, G.B., Morton, C., Saa, S., Allen, R.G. 2024. A comparative analysis of OpenET for evaluating evapotranspiration in California almond orchards. Agr. For. Meteorol. 355, 110146. https://doi.org/10.1016/j.agrformet.2024.110146

Copyright

The authors

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.