Publications [#58012] of Zbigniew J. Kabala

Papers Published

1. Ruud, N.C. and Kabala, Z.J., Numerical evaluation of the flowmeter test in a layered aquifer with a skin zone, Journal of Hydrology, vol. 203 no. 1-4 (1997), pp. 101 - 108 [S0022-1694(97)00091-7]
   (last updated on 2007/04/09)

   Abstract:
   In this study, we used a two-dimensional groundwater flow model to numerically evaluate the single flowmeter test in a series of two-layer confined aquifers for a fully penetrating well with a skin zone (i.e. a disturbed zone, filter-pack envelope, etc.). The skin zone causes errors in estimates of the vertical distribution of horizontal hydraulic conductivity by acting as a channel for cross-flow between layers of contrasting hydraulic conductivity. The bias in measured layer discharge rates, Q_i, is dependent on the ratios of the skin zone hydraulic conductivity to the layer hydraulic conductivities, K_s/K_i, and on the ratios of the skin zone thickness to the thickness of the individual layers, (r_s - r_w)/b_i. For any given K_s/K_i, the cross-flow increased with increases in the skin zone radius relative to the well radius, r_s/r_w. The error in estimated K_i due to a skin zone of reduced hydraulic conductivity (K_s/K_i < 1) is greater than that of a skin zone of a correspondingly enlarged hydraulic conductivity (K_s/K_i > 1). As K_s/K₁ increases, the ratios K over-bar ₁/K₁ and K over-bar ₂/K₂ converge approximately to the ranges 0.9-0.95 and 1.0-1.25, respectively. As K_s/K₁ decreases from value 1, the ratios of K over-bar ₁/K₁ and K over-bar ₂/K₂ diverge from these asymptotic ranges. In all simulated flowmeter tests, where K₁/K₂ = 10, K over-bar ₁ underestimates K₁ and K over-bar ₂ overestimated K₂.

   Keywords:
   Flowmeters;Groundwater flow;Mathematical models;Hydraulic conductivity;