Impact of soil heterogeneity on evapotranspiration and irrigation modeling using POLARIS and SSURGO-based soil hydraulic properties

Authors: Dhungel, Ramesh; Anderson, Raymond; French, Andrew; Skaggs, Todd; WANG, GREGORY - University Of California, Riverside; LI, NAN - University Of California, Riverside; SCUDIERO, ELIA - University Of California, Riverside

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2025
Publication Date: 10/1/2025
Citation: Dhungel, R., Anderson, R.G., French, A.N., Skaggs, T.H., Wang, G., Li, N., Scudiero, E. 2025. Impact of soil heterogeneity on evapotranspiration and irrigation modeling using POLARIS and SSURGO-based soil hydraulic properties. Agricultural Water Management. 319. Article 190806. https://doi.org/10.1016/j.agwat.2025.109806.
DOI: https://doi.org/10.1016/j.agwat.2025.109806

Interpretive Summary: Accurate soil mapping plays a critical role in optimizing water management for agricultural practices. By providing detailed information on soil properties, high-quality soil maps guide precise irrigation strategies, ensuring crops receive the right amount of water. This helps prevent the issues of overwatering, which wastes resources, and underwatering, which harms crop health and yield. Despite the utility of traditional soil maps, such as those in the USDA’s Soil Survey Geographic Database (SSURGO), they often suffer from inaccuracies that hinder their application in precision irrigation. To overcome these shortcomings, the POLARIS map was introduced, utilizing advanced modeling techniques to offer more reliable data. A study comparing POLARIS with SSURGO in the Yuma Valley, a vital agricultural area shared by Arizona and California, revealed substantial differences in irrigation needs when using these maps. The research underscores the significant impact of accurate soil data on water management, emphasizing the need for enhanced mapping methods to better support sustainable agricultural practices. These results will be useful for farmers and irrigation managers seeking to use site-specific irrigation techniques to reduce water and nutrient losses.

Technical Abstract: Accurate maps of soil hydraulic properties are needed to enable precise, site-specific modeling of crop water use. Most available maps (e.g., the USDA-NRCS Soil Survey Geographic Database (SSURGO)) have significant uncertainties that may limit their usefulness for implementing site-specific irrigation (Irri). Recently, a probabilistic, high-resolution (30'm) soil property map of the contiguous United States (POLARIS) was developed. In this study, we compare the use of POLARIS and SSURGO for parameterizing a water and energy-balance model of simulated Irri and simulated evapotranspiration (ETs). The Backwards Averaged Iterative Two Source Energy Balance Solution (BAITSSS) model was applied to a major irrigated agricultural region (Yuma Valley of Arizona and the adjacent Bard region of California, ~ 110'km2). The BAITSSS simulation covered a lettuce growing cycle between September and December 2019 (78 days) utilizing Landsat-based vegetation indices, North American Land Data Assimilation System (NLDAS) weather variables, and Parameter-elevation Relationships on Independent Slopes Model (PRISM) precipitation data. SSURGO-based soil hydraulic properties resulted in approximately a 7'% increase in field-averaged simulated seasonal ETs and a 25'% increase in field-averaged seasonal simulated Irri. The POLARIS-based simulations had higher Irri efficiency and less drawdown of soil moisture prior to harvest. Overall, this study highlights uncertainties introduced by soil parameterization in ETs and Irri modeling and their role in agricultural water management.