The shallow subsurface is an extremely important zone that yields much of our water resources and also serves as the repository for municipal, industrial and government waste. The near-surface environment also acts as a buffer and filter for contaminants introduced by agricultural activities. As safe and effective use of the subsurface environment is a major challenge facing our society, there is a great need to improve our understanding of the shallow subsurface. With an increasing demand for investigation methods that have both high accuracy and resolution across a variety of spatial scales, a new discipline of hydrogeophysics has evolved, which aims at combining knowledge from various disciplines like hydrology, hydrogeology, soil physics and geophysics thereby striving to improve subsurface characterization and monitoring. Geophysical methods offer the advantage of being able to measure subsurface structures and to estimate transport properties in a non-invasive and dynamic manner. In spite of numerous successful examples of the combined use of geophysical methods and hydrological investigations in subsurface environments, several obstacles exist for systematically implementing successful hydrogeophysical investigations, and these obstacles form the basis for much of the research within this discipline. The purpose of this section is to discuss recent research advances within the emerging discipline of hydrogeophysics, including those associated with basic theory, geophysical instrumentation improvement, development of emerging technologies, geophysical data inversion approaches and joint inversion, methods for fusing hydrological, hydrogeological and geophysical data, and development of petrophysical models relating geophysical, hydrological and geological parameters. In addition to these research fronts, we also solicit hydrogeophysical case studies that illustrate the potential, benefits, or limitations of hydrogeophysical investigations over a wide range of spatial and temporal scales in both the vadose zone and groundwater. This session should be of interest to researchers across a variety of disciplines, including those investigators who are interested in using geophysical methods and data for improved subsurface characterization and monitoring as well as those who are active in hydrogeophysical research.