Water Resources Graduate Program

Physical mechanisms that control water motion in soil, porous media, and fractured porous media.

BIOWATER RESEARCH: Projections for food demand over the next few decades will require significant increases in agricultural productivity for essentially the same soil footprint but reduced water consumption. Sustaining intensified agricultural productivity over the long term will require clear understanding of fundamental soil processes.  We have chosen to contribute to this quest by improving agricultural productivity on sandy-soil in arid and semi-arid agricultural areas. Three questions are being investigated:

Determine how soil biology can be used to increase water retention quantity and duration in sandy-soils.

Determine if subtle changes in irrigation practices can be used to eliminate the common problem of subsurface water repellency, which in sandy soils often causes crop stress and hastens deep drainage losses of agricultural nutrients.

Because seasonal hydrologic cycles in non-irrigated land impacts the establishment and long-term resiliency of plant communities, our goal is to quantify the subsurface vapor-capillary cycle in native grazing lands to improve our understanding of arid land soil hydrology.

EPIKARST EVOLUTION: The epikarst is the transitional region of carbonate parent material between the soil and the underlying karst cavern system. This region slowly evolves into a mature karst via cave enlargement and the erosional opening of micro-fractures. Our investigation focuses on the possible acceleration of micro-fracture erosion by soil water driven by the combined action of chemical and hydrodynamic processes.

WATER REPELLENCY: For many years, even decades, water repellency has been the topic of study in many countries, including Holland, Spain, Australia and the USA. These studies typically focused on the link between water repellency and various soil properties. We are exploring biophysical mechanisms that may lead to remediation and prevention techniques in agricultural settings.

GAS EXCHANGE ACROSS THE EARTH-ATMOSPHERE INTERFACE: When porous media is highly permeable or fractured, gas advection will supersede diffusion as the main mechanism for gas exchange across the soil-atmosphere boundary. In addition to this higher transport rate, diurnal peaks occur at night rather than during the day. In collaboration with colleagues at Ben Gurion University, we are exploring the extent to which this mechanism contributes to vadose zone gas venting and heat exchange with the atmosphere.

SOLARIZATION: Rather than using herbicides and pesticides, soil solarization has been used in many low-latitude agricultural regions to successfully disinfect soil. In collaboration with fellow scientists (Jennifer Parks and Carol Mallory-Smith, Oregon State University), we are exploring the feasibility of using solarization  in the Pacific Northwest.