ZIWR Weekly Seminar
Wednesday, January 15th, 2020 at 13:15
Seminar Room, Old Administration Building
Evaporation from porous media
Tamir Kamai (tamirk@agri.gov.il) and Shmuel Assouline
Institute of Soil, Water, and Environmental Sciences, ARO – the Volcani Center, Israel.
Evaporation is a natural process with significant hydrological and environmental implications for agricultural and natural systems. The exchange of water between the soil and the atmosphere at Earth's surface is an important component of the hydrological cycle and the soil energy balance. These are also valuable issues in the context of climate change perspectives and its impact on soil related processes. Recent insights have introduced new concepts and capabilities for depicting the evaporation process. For example, a characteristic length for evaporation from porous media enables quantifying the link between the soil hydraulic properties and evaporation rates, and the development of an evaporative front within the porous media. Different analytical and numerical approaches were developed to provide predictive capabilities for the dynamics of the evaporative fluxes and for the distributions of water and temperature in the profile. In this seminar, I will introduce an analytical approach that we have been developing in the last couple of years, which is based on the fundamental macroscopic equations and characteristics that govern the evaporation process, namely: Atmospheric conditions that drive the process. Bulk hydrological properties that regulate the flow. The characteristic length that determines the location of the evaporative front, which separates between the water liquid and vapor phases, below and above it, respectively. Richards' equation for water liquid flow towards the evaporative front. Fick's law for water vapor flow from the evaporative front towards the surface. I will present our conceptual understanding of the process, introduce the model with its underlying assumptions, and present modeling results and their comparisons to existing data. We will review two evaporation scenarios. The first one considers evaporation in hyper-arid environments, which are characterized with relatively small amounts of precipitation, negligible recharge, and with the significant extent of vadose zone profiles above deep groundwater. In the second scenario, a classical procedure for experimenting evaporation is in hand, in which evaporation is evaluated by continuously monitoring the weight of soil columns (or lysimeters) that are exposed to the atmosphere at their top. For both scenarios, I will also present predictive capabilities for evaporation rates through knowledge of soil hydraulic properties and atmospheric conditions.
