Emerging issues and research opportunities in vadose zone processes

Authors: STEWART, RYAN - Virginia Polytechnic Institution & State University; FLURY, MARKUS - Washington State University Extension Service; AJAMI, HOORI - University Of California, Riverside; Anderson, Raymond; Green, Timothy; JIN, YAN - University Of Delaware; PATRIGNANI, ANDRES - Kansas State University; SHILLITO, ROSE - Us Army Engineer Research And Dvelopment Center; ZHANG, WEI - Michigan State University; ABOU NAJM, MADJI - University Of California, Davis; BABAEIAN, EBRAHIM - University Of Florida; BERLI, MARKUS - Desert Research Institute In Las Vegas; BROOKSHIRE, E. N. JACK - Montana State University; DAIGH, AARON L. - University Of Nebraska; GIOVANDO, JEREMY - Us Army Engineer Research And Dvelopment Center; HEINSE, ROBERT - University Of Idaho; HEITMAN, JOSH - North Carolina State University; HUANG, JINGYI - University Of Wisconsin; KELLENERS, THIJS - University Of Wyoming; NASERI, MAHYER - Technical University Of Braunschweig; OCHSNER, TYSON - Oklahoma State University; RADOLINSKI, JESSE - University Of Maryland; SADEGHI, MORTEZA - California Department Of Water Resources; SASIDHARAN, SALINI - Oregon State University; SHUKLA, MANOJ - New Mexico State University; TULLER, MARKUS - University Of Arizona; WENDROTH, OLE - University Of Kentucky; WU, JOAN - Washington State University; WYATT, BRIANA - Texas A&M University; YANG, YANG - Beijing Normal University; YU, YINGXUE - Washington State University; ZHANG, FRED - Intera, Inc

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2025
Publication Date: 8/4/2025
Citation: Stewart, R.D., Flury, M., Ajami, H., Anderson, R.G., Green, T.R., Jin, Y., Patrignani, A., Shillito, R., Zhang, W., Abou Najm, M.R., Babaeian, E., Berli, M., Brookshire, E., Daigh, A.M., Giovando, J., Heinse, R., Heitman, J., Huang, J., Kelleners, T., Naseri, M., Ochsner, T.E., Radolinski, J.B., Sadeghi, M., Sasidharan, S., Shukla, M.K., Tuller, M., Wendroth, O., Wu, J., Wyatt, B.M., Yang, Y., Yu, Y., Zhang, F. 2025. Emerging issues and research opportunities in vadose zone processes. Vadose Zone Journal. 24(4). Article e70030. https://doi.org/10.1002/vzj2.70030.
DOI: https://doi.org/10.1002/vzj2.70030

Interpretive Summary: The subsurface environment above fully saturated groundwater, called the vadose zone, is an important regulator of many natural processes. Many interactions and effects in the vadose zone remain poorly understood or quantified. This article was developed to highlight the most relevant challenges, knowledge gaps, and opportunities associated with the vadose zone. It is organized into eight sections describing different emerging issues and opportunities. The topics include scaling of soil properties and processes, surface and energy balance, wildfires, preferential water flow paths and biogeochemical processes, large-scale soil moisture monitoring networks, emerging contaminants, and modeling of flow and transport. This compendium can inform and guide program managers, researchers, and others about the needs for research and outreach activities related to vadose zone science in the coming years.

Technical Abstract: The unsaturated near-surface environment, commonly referred to as the vadose zone, provides important ecosystem services such as food and water provisioning, climate regulation, and support for infrastructure. Anthropogenic and natural pressures, including changing climatic conditions, are threatening related freshwater and soil resources. Addressing these challenges requires a better understanding of the processes and interactions that occur in the vadose zone. This review was developed to highlight the most relevant issues, knowledge gaps, and research opportunities associated with the vadose zone. It is organized into eight sections, each including a problem statement, a summary of recent innovations, and a preview of emerging challenges and study opportunities. Topics include scaling of soil properties and processes, the surface energy balance, interplay between preferential water flow paths and biogeochemical processes, interactions between fires and vadose zone processes, the role of large-scale soil moisture monitoring efforts, emerging contaminants and their fate in the vadose zone, and modeling flow and transport processes in the vadose zone. This overview is intended to serve as a primary compendium for informing research and outreach activities related to vadose zone science over the next decade and longer.