Keywords: air entrapment, air pressurisation, soil moisture observations, shallow water table, water table fluctuation, recharge, runoff, HYDRUS-1D, infiltration, numerical modelling, ideal gas law
Observations of long term air entrapment affecting runoff and water table
Air entrapment plays a significant role in controlling infiltration and observed depth to water table in shallow water table environments. The current study incorporates multi-event field measurements with varying antecedent conditions and numerical modelling, using HYDRUS-1D to quantify the variation of air pressurisation values. The observations of water table in the field data depart significantly on occasions from the theoretical values using a calibrated Richards' equation solution. Antecedent conditions were also found to be very important in controlling air pressurisation. A simple analysis based on ideal gas law was also done to help understand air pressurisation effects.