2013 Annual Report
(b) Test a newly develop non-isothermal water and solute transport model to elucidate the accuracy of simulated soil water content and evaporation. Compare simulation to field-scale soil water content and evaporation measurements.
This research will include measurement of various soil physical properties, evapo-transpiration, heat transfer, energy balances and soil-atmospheric exchanges to characterize the moisture status of soils. Models will be tested and improved models will be developed, where necessary, to enable prediction of soil moisture status from saturated to very dry conditions.
The coupled transport of liquid water, vapor, and energy in the surface soil layer influences a variety of hydrological and ecological process. Theoretical models of evaporation processes, based mainly on the work of Philip and de Vries, are often in disagreement with experimental data collected on moderately dry soils. A major limitation to improving theory is inadequate measurement methods and technologies. In these studies, data from the column provided detailed measurements of evaporation, soil moisture, and soil temperature during soil drying.
Laboratory studies continued to test methods of measuring soil water content in soil columns. Several moisture and heat-flux sensors are being evaluated, including: dual needle heat pulse sensors, triple needle heat pulse sensors, TM water & temperature sensor which uses capacitance/frequency domain technology, Campbell Science 229-L (heat dissipation method) water matric potential sensors, and soil relative humidity probes, HC2-C05. To date, obtaining reliable and accurate soil water content measurements from a soil column has been elusive. In general, none of the tested probes were able to give accurate moisture contents over the full spectrum of water content. Further research is needed to find the optimal method for measuring the full range in water contents. Work will continue on this topic, since accurate water content measurements are needed to fully test non-isothermal heat and water transport theory, the primary goal of this research project.