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Evaluation of unconfined-aquifer parameters from pumping test data by nonlinear least squares

Journal of Hydrology
By:  and 
https://doi.org/10.1016/S0022-1694(96)03101-0

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Abstract

Nonlinear least squares (NLS) with automatic differentiation was used to estimate aquifer parameters from drawdown data obtained from published pumping tests conducted in homogeneous, water-table aquifers. The method is based on a technique that seeks to minimize the squares of residuals between observed and calculated drawdown subject to bounds that are placed on the parameter of interest. The analytical model developed by Neuman for flow to a partially penetrating well of infinitesimal diameter situated in an infinite, homogeneous and anisotropic aquifer was used to obtain calculated drawdown. NLS was first applied to synthetic drawdown data from a hypothetical but realistic aquifer to demonstrate that the relevant hydraulic parameters (storativity, specific yield, and horizontal and vertical hydraulic conductivity) can be evaluated accurately. Next the method was used to estimate the parameters at three field sites with widely varying hydraulic properties. NLS produced unbiased estimates of the aquifer parameters that are close to the estimates obtained with the same data using a visual curve-matching approach. Small differences in the estimates are a consequence of subjective interpretation introduced in the visual approach.
Publication type Article
Publication Subtype Journal Article
Title Evaluation of unconfined-aquifer parameters from pumping test data by nonlinear least squares
Series title Journal of Hydrology
DOI 10.1016/S0022-1694(96)03101-0
Volume 192
Issue 1-4
Year Published 1997
Language English
Publisher Elsevier
Contributing office(s) Toxic Substances Hydrology Program
Description 14 p.
First page 300
Last page 313
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