Leo M. Walsh Distinguished Lecture: Jirka Šimunek will present “Modeling vadose zone processes using HYDRUS” – Apr. 28

The Department of Soil Science is pleased to announce the 2021 Leo M. Walsh Distinguished Lecture in Soil Science to be held virtually on Wednesday, April 28 at 3:30 p.m. This year’s lecture will feature Dr. Jirka Šimunek, who will present on “Modeling Vadose Zone Processes Using HYDRUS and Its Specialized Modules.”

To attend the talk, register at Connection information will be emailed one day prior to the lecture. In addition, there will also be a virtual visit with interested graduate students from 1:30 to 2:15 pm at the following link:

Dr. Šimunek received his PhD from the Czech Academy of Sciences in 1993. He joined the University of California-Riverside in 1990 as a postdoctoral Soil Scientist in collaboration with the US Salinity Laboratory, USDA-ARS. He has been a Professor and Hydrologist in the Department of Environmental Sciences at the University of California-Riverside as of 2003.

The lecture is made available by the generosity of Leo M. Walsh and the Leo M. Walsh Distinguished Lecture in Soil Science Fund. Dr. Walsh is emeritus dean of CALS and emeritus professor of Soil Science.

Dr. Šimunek’s abstract is: Modern civilization uses large quantities of water and an unprecedented number of chemicals. Agriculture is one of the most important sources for non-point source pollution due to the use of chemicals in plant and animal production. Many mathematical numerical models evaluating water flow and the fate and transport of these chemicals in the subsurface were developed over the last three or four decades. These models are now readily available and widely used. This presentation will first briefly review recent versions of the HYDRUS models widely used to model water flow, chemical movement, and heat transport through variably saturated soils. He will discuss various specialized HYDRUS modules intended to simulate processes not available in the standard HYDRUS versions, such as the transport of multiple interacting solutes, preferential flow, colloid-facilitated solute transport, cosmic ray fluxes, or transport of fumigants. These new modules include the DualPerm, C-Ride, HP1/2/3, Wetland, UnsatChem, Fumigant, Cosmic, Furrow, Slope3, and many other modules. Finally, he will briefly review many recent applications of the Hydrus models, which include modeling of various irrigation practices, different contaminants, and different cropping systems.

Contact Jingyi Huang at for more information.