Title: Observations of long term air entrapment affecting runoff and water table

Authors: Jing Zhang, Nirjhar Shah, Mark A. Ross

Addresses: The Key Lab of Resource Environment & GIS of Beijing, College of Resource Environment and Tourism, Capital Normal University, #105 West 3rd Ring Road North, Beijing 100048, China. ' BCI Engineers and Scientists, Inc., 2000 E. Edgewood Drive Suite 215, Lakeland, FL 33803l, USA. ' Department of Civil and Environmental Engineering, University of South Florida, 4202 E. Fowler Ave, ENB 118, Tampa, FL 33620, USA

Abstract: 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.

Keywords: air entrapment; air pressurisation; soil moisture observations; shallow water table; water table fluctuation; recharge; runoff; HYDRUS-1D; infiltration; numerical modelling; ideal gas law.

DOI: 10.1504/IJW.2009.028723

International Journal of Water, 2009 Vol.5 No.2, pp.140 - 162

Published online: 25 Sep 2009 *

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