Multiple Splits of the Plume: telescoping of capture zones

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MULTIPLE SPLITS OF THE PLUME: telescoping of capture zones

By the earthDr!

The first figure describes the initial pumping conditions for three recovery wells oriented along

the long-axis of a ground-water plume of toxic chemicals. Note that each recovery well has an associated capture zone in the situation where the recovery wells are oriented along the long-axis of the ground-water plume. I have simplified the drawing to depict flowpaths, but not equipotential lines. This makes the figure less cluttered, but also much easier to draw.

In this figure, there are three recovery wells and three capture zones. Note that the width of capture for the most upgradient capture zone (left-most) is equal to the width of the capture zone depicted by the blue-curved line. In the two-downgradient recovery wells, the actual width of capture is greater than that depicted by the blue-curved line signifying the capture zone. The most-upgradient recovery well influences those flowpaths, just outside of the upgradient capture zone, to be diverted to flow inwardly toward the long-axis of the plume. These flowpaths are now re-positioned so that they can be captured by the next-downgradient recovery well. Note that there is a difference between actual and apparent capture zones for all but the most-upgradient or first recovery well. With each succeeding downgradient recovery well, the actual capture zone increases in size or in zone of capture. Not only does the capture zone increase in width, but it also increases in depth with successive downgradient recovery wells. This telescoping of recovery wells causes the focusing of ground-water flowpaths from greater and greater distances normal to the non-pumping ground-water flowpath to which these three recovery wells were located.

Given sufficient time to allow the clean, outer ground-water flowpaths to be deflected and flush contaminants from the soil or the cracks, crevices, joints, and fractures of bedrock,

then the plume can be split downgradient of each stagnation point that is associated with a recovery well. This second figure illustrates the development of three separate plumelets from the pumping of ground water from the three recovery wells. In and of itself, this is an interesting phenomenon. But this phenomenon is more than of academic interest. It has practical importance as can be seen on another webpage (use the back button on your browser or click on the Table of Contents to relocate yourself back to this page should you choose to review the other page).

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