A Novel Approach to Increase Accuracy in Remotely Sensed Evapotranspiration Through Basin Water Balance and Flux Tower Constraints

Authors

Kul Khand, ASRC Federal Data Solutions
Gabriel B. Senay, U.S. Geological Survey Earth Resources Observation and Science Center
MacKenzie Friedrichs, KBR Inc.
Koong Yi, Lawrence Berkeley National Laboratory
Joshua B. Fisher, Chapman UniversityFollow
Lixin Wang, Indiana University Indianapolis
Kosana Suvočarev, University of California, Davis
Arman Ahmadi, University of California - Berkeley
Housen Chu, Lawrence Berkeley National Laboratory
Stephen Good, Oregon State University
Kanishka Mallick, Luxembourg Institute of Science and Technology
Justine Missik, Ohio State University
Jacob A. Nelson, Max Planck Institute for Biogeochemistry
David E. Reed, Yale University
Tianxin Wang, University of California - Berkeley
Xiangming Xiao, University of Oklahoma Norman Campus

Document Type

Article

Publication Date

7-5-2025

Abstract

Remote sensing-derived evapotranspiration (RSET) products capture the spatiotemporal variations of evapotranspiration (ET) from field to basin scales with unprecedented details. However, their accuracy varies across RSET estimation methods and diverse hydroclimate regions. While ET modeling efforts to account for biophysical processes and controlling parameters have made good progress in recent years, a parallel approach of integrating in-situ ET with RSET could reduce biases in RSET products. Basin water balance ET (WBET) and flux tower ET are widely applied to evaluate RSET accuracy, yet such ET measurements are rarely used for RSET bias corrections, especially for large area applications. To address this issue, we propose a novel approach: the water balance equivalence (WABE) method, which generates spatially continuous WBET for correcting biases in RSET products. The WABE method computes synthetic WBET by integrating observed WBET and flux tower-derived FLUXCOM ET, which fills the spatial gaps of observed WBET and generates a spatially continuous WBET dataset. Synthetic WBET (2002–2015 annual average) of eight-digit hydrologic unit code (HUC8) basins across the conterminous United States (CONUS), constituting 44 % (887 out of 2035 basins) of CONUS basins, was determined within 2.0 % (RMSE = 12 %) of observed WBET at CONUS and between 1–12 % (RMSE = 3–33 %) across 18 regions in CONUS. With WABE-based bias corrections, the overall annual bias of RSET decreased from 10 % (RMSE = 34 %) to 6 % (RMSE = 26 %) across 37 flux tower sites. The WABE method offers a new approach for RSET accuracy improvement and shows great promise for large area implementations with a potential to yield substantial benefits for building accurate basin water budgets and water management decisions.

Comments

This article was originally published in Journal of Hydrology, volume 662 part A, in 2025. https://doi.org/10.1016/j.jhydrol.2025.133824

Recommended Citation

Khand, K., Senay, G.B., Friedrichs, M., Yi, K., Fisher, J.B., Wang, L., Suvočarev, K., Ahmadi, A., Chu, H., Good, S., Mallick, K., Missik, J., Nelson, J.A., Reed, D.E., Wang, T., Xiao, X., 2025. A novel approach to increase accuracy in remotely sensed evapotranspiration through basin water balance and flux tower constraints. J. Hydrol. 662 (A), 133824. https://doi.org/10.1016/j.jhydrol.2025.133824

Copyright

The authors

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.