Montazar et al. (2026) Persistent daily OpenET bias drives seasonal water-use divergence in California avocado orchards

Identification

• Journal: Agricultural Water Management
• Year: 2026
• Date: 2026-07-20
• Authors: Aliasghar Montazar, Ben Faber, André Daccache
• DOI: 10.1016/j.agwat.2026.110651

Research Groups

• University of California Division of Agriculture and Natural Resources, UCCE Imperial County, Holtville, CA, USA
• University of California Division of Agriculture and Natural Resources, UCCE Ventura County, Ventura, CA, USA
• University of California Davis, Dept. of Biological and Agricultural Engineering, Davis, CA, USA

Short Summary

This study evaluates the performance of OpenET, a satellite-based evapotranspiration product, in estimating actual evapotranspiration (ET) in commercial avocado orchards across Southern California. The results show that while OpenET reproduces broad temporal ET variability, it consistently generates higher ET estimates than eddy covariance measurements, leading to substantial cumulative seasonal water-use divergence.

Objective

• Evaluate the accuracy of OpenET in estimating actual evapotranspiration (ET) in commercial avocado orchards.
• Characterize the magnitude and temporal structure of daily ET differences between OpenET and eddy covariance measurements.
• Determine whether recurring daily ET differences accumulate into substantial cumulative seasonal water-use divergence.

Study Configuration

• Spatial Scale: Orchard-scale, with a spatial resolution of 30 m.
• Temporal Scale: Daily to seasonal timescales.

Methodology and Data

• Models used: OpenET ensemble, which integrates multiple remote sensing models (eeMETRIC, SIMS, PT-JPL, SSEBop, DisALEXI, and geeSEBAL).
• Data sources: Landsat observations with temporal interpolation between satellite overpasses.

Main Results

• Daily ET comparisons show moderate to strong agreement between OpenET and eddy covariance measurements, but with consistently higher OpenET estimates.
• Regression slopes generally exceed unity (1.08–1.38), indicating systematic ET amplification under elevated evaporative-demand conditions.
• Cumulative seasonal divergence ranges from 23 to 282 mm across site-year combinations.

Contributions

• This study highlights the importance of evaluating satellite-based ET products across operational seasonal timescales rather than relying solely on daily performance metrics.
• The results suggest that orchard structural characteristics and surface heterogeneity may influence the magnitude of OpenET divergence in commercial avocado production environments.

Funding

• This research was funded by [project name], [program name], and [reference code].

Citation

@article{Montazar2026Persistent,
  author = {Montazar, Aliasghar and Faber, Ben and Daccache, André},
  title = {Persistent daily OpenET bias drives seasonal water-use divergence in California avocado orchards},
  journal = {Agricultural Water Management},
  year = {2026},
  doi = {10.1016/j.agwat.2026.110651},
  url = {https://doi.org/10.1016/j.agwat.2026.110651}
}