HR: 1330h
AN: H13B-04    [Abstracts]
TI: An Assessment of Analytical Model Predictions of Pumping-Induced Vadose Zone Response in an Unconfined Aquifer Using Neutron-Derived Soil Moisture Profiles
AU: * Endres, A L
EM: alendres@sciborg.uwaterloo.ca
AF: University of Waterloo, Department of Earth Sciences, Waterloo, ON N2L 3G1 Canada
AU: Jones, J P
EM: jpjones@sciborg.uwaterloo.ca
AF: University of Waterloo, Department of Earth Sciences, Waterloo, ON N2L 3G1 Canada
AU: Bertrand, E A
EM: eabertra@scimail.uwaterloo.ca
AF: University of Waterloo, Department of Earth Sciences, Waterloo, ON N2L 3G1 Canada
AB: Analytical models used to analyze hydraulic head data from pumping tests represent drainage from above the water table by means of boundary conditions defined along the water table. While these boundary conditions do not explicitly describe the details of flow in the vadose zone, they do predict the bulk vadose zone response (i.e., cumulative drainage flux and excess storage). This bulk response can be determined directly from soil moisture content profiles measured during a pumping test. A comparison of the predicted and observed bulk vadose zone response was performed using hydraulic head data and soil moisture content profiles obtained during a seven day pumping test at CFB Borden, Ontario. Detailed soil moisture profiles were acquired with a thermal neutron moisture probe in six observation wells at varying radial distances throughout the test. Three different analytical models (one assuming instantaneous drainage and two types of delayed drainage using exponential decay) were used to predict the bulk vadose zone response from the hydraulic head measurements. These predictions significantly overestimated the observed cumulative drainage flux in the vicinity of the pumping well. The exponential decay models predicted a relatively rapid dissipation of the excess storage; the observed excess storage exhibited little, if any, decay throughout the entire pumping test. Our results clearly show that boundary conditions used in these analytical models do not adequately account for the details of flow in the vadose zone.
DE: 0915 Downhole methods
DE: 1829 Groundwater hydrology
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2005 Joint Assembly