Wednesday, November 6, 2013

Distance-Drawdown Analysis

Distance-drawdown analysis is a useful technique for estimating aquifer properties when drawdown measurements are taken during a pumping test at several observation wells located at different radial distances from the control (pumped) well. To perform distance-drawdown analysis, one plots a single drawdown observation per well, each recorded at the same time since the start of pumping, on a graph of drawdown versus radial distance.

Most of us are familiar with estimating an aquifer's transmissivity and storativity from distance-drawdown data using the Cooper and Jacob (1946) method as shown in the following figure.
Distance-drawdown analysis, Cooper and Jacob (1956)
Distance-drawdown analysis for an unconfined aquifer.
Did you know that you may perform distance-drawdown analysis with pumping test methods in AQTESOLV other than Cooper and Jacob? For example, you may match distance-drawdown data with the Hantush and Jacob (1955) method for a leaky confined aquifer (see figure below).
Distance-drawdown plot for a leaky confined aquifer.
To display a distance-drawdown graph in AQTESOLV, choose Distance-Drawdown from the View menu. The Distance-Drawdown option is active when you have more than one observation well in your data set. If your data set includes more than one pumping well, the Distance-Drawdown option is inactive as distance-drawdown analysis assumes radially symmetric flow around a single pumping well; however, you may use AQTESOLV to prepare contour plots of drawdown (plan and cross section) when multiple pumping wells are present.

To learn more about AQTESOLV, take the guided tour or download the demo!

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