Ryan Stewart


Ph.D. Water Resources Engineering, Oregon State University, Corvallis, OR, 2013

M.S. Water Resources Engineering, Oregon State University, Corvallis, OR, 2010

B.S. Mechanical Engineering, Cal Poly, San Luis Obispo, CA, 2002


2013-Present Assistant Professor, Crop & Soil Environmental Science, Virginia Tech

2013 Post-Doctoral Research Scholar, Oregon State University, Corvallis, OR

2008-2013 Graduate Research Assistant, Oregon State University, Corvallis, OR

2006-2008 Peace Corps Volunteer – Basic Sanitation, Bolivia

2004-2006 Specialist – Oak Lodge Sanitary District, Milwaukee, OR

Link to curriculum vita

Courses Taught

As part of my position at Virginia Tech, I will be teaching several upper-division courses focused on soil-water interactions and soil physical processes.  These courses will include:

Soil physical and mechanical properties and the physical processes controlling soil water retention and flow in agronomic and natural settings. Grain size distribution, weight-volume relationships, specific surface, electrical charge density, consistency, stress, compaction, rainfall runoff, water retention, steady/non-steady water flow in saturated/unsaturated soil, infiltration, bare soil evaporation, and soil water balance. Pre: (3114, 3124) or (GEOS 3614, GEOS 3624). (3H,3C)

Application of the principles of physics and mathematical analysis to the study of soils. Covers the physical nature and properties of soil solids, basic soil mechanics, physical state of water in soils, infiltration and movement of water in soils, mass transport in soil solutions, soil gases and soil aeration, heat and heat transfer in soils. I Pre: CSES 3114, PHYS 2205, MATH 2015. (3H,3L,4C)

Undergraduate Research

Active participation in a research group is one of the most rewarding experiences a student can have during their undergraduate education. Performing undergraduate research allows students the chance to apply their classroom knowledge and to develop new and exciting skills and connections.  Undergraduate students with research experience generally are more competitive applicants for positions in both grad school and in industry.  Therefore, I am always developing research opportunities for undergraduate students that are interesting and worthwhile.   Pleae contact me to discuss undergraduate research opportunities in greater detail.

Program Focus

The Critical Zone Research Lab at Virginia Tech focuses on quantifying and scaling interactions between water, soil, and plant communities. This includes a combination of field work, laboratory analysis, and development of modeling frameworks. We foster active collaboration across disciplines, working on topics which span ecology, engineering, agriculture, and urban systems. 

In the Critical Zone Research Lab we utilize three main approaches: concepts derived from fundamental principles, observations employing novel techniques, and synthesis combining analytical quantification with numerical experiments.  

Current and Future Research

Soil-Water Interactions in Shrink-swell Clay Soils

  • time-dependence of swelling
  • non-linear threshold behaviors in runoff and infiltration
  • changing hydraulic conductivity of soil matrix due to swelling and shrinking
  • scaling of hydrologic processes in shrink-swell clay soils


Preferential Flow through Structural Pathways

  • characterization of structural pathways caused by plants and soil aggregation
  • description of preferential flow using parsimonious models
  • nutrient transport
  • development of new soil parameters to use in infiltration and runoff modeling
  • numerical modeling to better understand processes


Effect of Land Use Change on Hydrology and Soils

  • Large-scale afforestation is occurring in regions across the globe
  • What are the effects on regional water availability and soil quality?


Development of Novel Instruments and Methods

  • new "resonating" raingauge
  • instruments to monitor soil crack swelling dynamics
  • new device to measure plot-scale runoff
  • accelerometers to monitor environmental processes

Role of Graduate Students

Graduate school is a time to develop skills which will enable students to achieve future success.  In addition to the knowledge gained from coursework and research, students will improve their abilities in critical thinking, scientific reasoning, reading comprehension, and effective writing and presenting.  As an advisor, I strive to maintain a positive scholastic environment, and work to promote each individual student’s growth and success. 

Graduate students are vital contributors to the overall direction and vigor of the Critical Zone Research group.  I am always looking for motivated and hard-working graduate students to join the research group and help advance the understanding of critical zone processes. I accept graduate students at both the M.S. and Ph.D. levels, and do my best to work with students in finding the best match between their individual interests and the activities and direction of the overall research group. 

Ryan Stewart