PONDED INFILTRATION INTO SIMPLE SOIL SYSTEMS

Abstract

We report here the pressures of air ahead of the wetting front and of encapsulated air during ponded infiltration into simple, unbounded soil systems. Air pressures ahead of the wetting front were found to be large enough to cause a decrease in infiltration rate at short times. We show that these air pressures are consistent with Darcy's law applying for the gas phase. It was predicted theoretically and found experimentally that the pressure of encapsulated air increases as pressure potential increases. The large encapsulated air pressures that result have implications for the infiltration process, and we suggest that they may also affect other soil physical processes. It is predicted that if either a shorter column or a coarser material were used, both the encapsulated air pressures and the reduction in infiltration rate caused by the air pressure ahead of the wetting front would be reduced. We report here the pressures of air ahead of the wetting front and of encapsulated air during ponded infiltration into simple, unbounded soil systems. Air pressures ahead of the wetting front were found to be large enough to cause a decrease in infiltration rate at short times. We show that these air pressures are consistent with Darcy's law applying for the gas phase. It was predicted theoretically and found experimentally that the pressure of encapsulated air increases as pressure potential increases. The large encapsulated air pressures that result have implications for the infiltration process, and we suggest that they may also affect other soil physical processes. It is predicted that if either a shorter column or a coarser material were used, both the encapsulated air pressures and the reduction in infiltration rate caused by the air pressure ahead of the wetting front would be reduced. © Williams & Wilkins 1981. All Rights Reserved.