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. 2011 Jun;47(3):588-596.
doi: 10.1111/j.1752-1688.2011.00526.x.

Modeling the Potential Impact of Seasonal and Inactive Multi-Aquifer Wells on Contaminant Movement to Public Water-Supply Wells

Rl Johnson, Br Clark, Mk Landon, Lj Kauffman, Sm Eberts
Free PMC article

Modeling the Potential Impact of Seasonal and Inactive Multi-Aquifer Wells on Contaminant Movement to Public Water-Supply Wells

Rl Johnson et al. J Am Water Resour Assoc. 2011 Jun.
Free PMC article

Abstract

Wells screened across multiple aquifers can provide pathways for the movement of surprisingly large volumes of groundwater to confined aquifers used for public water supply (PWS). Using a simple numerical model, we examine the impact of several pumping scenarios on leakage from an unconfined aquifer to a confined aquifer and conclude that a single inactive multi-aquifer well can contribute nearly 10% of total PWS well flow over a wide range of pumping rates. This leakage can occur even when the multi-aquifer well is more than a kilometer from the PWS well. The contribution from multi-aquifer wells may be greater under conditions where seasonal pumping (e.g., irrigation) creates large, widespread downward hydraulic gradients between aquifers. Under those conditions, water can continue to leak down a multi-aquifer well from an unconfined aquifer to a confined aquifer even when those multi-aquifer wells are actively pumped. An important implication is that, if an unconfined aquifer is contaminated, multi-aquifer wells can increase the vulnerability of a confined-aquifer PWS well.

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Figures

FIGURE 1
FIGURE 1
Conceptual Drawing Showing the Impact of an Inactive Multi-aquifer Well on Contaminant Movement to a Public Water-Supply Well.
FIGURE 2
FIGURE 2
Map Showing Simplified Numerical Model Domain and Simulated Effects of Multi-aquifer Wells on Flow to a Confined-Aquifer Public Water-Supply (PWS) Well. The extent of the simulated 1-, 5-, 10-, and 40-year zones of transport (ZOT) in the confined aquifer for the PWS well are shown for the (a) PWS-well-only scenario, (b) seasonal scenario, and (c) inactive scenario. The pumping rate at the PWS well for these model results was 1,200 m3/day.
FIGURE 3
FIGURE 3
Graph Showing 40-Year Zones of Transport for Various Public Water-Supply (PWS) Well Pumping Rates in the Simplified Numerical Model.
FIGURE 4
FIGURE 4
Contours of Hydraulic Head Difference Between the Confined and Unconfined Aquifers (in meters) During Irrigation and Nonirrigation Conditions. Scenarios are (a) PWS-well-only, (b) seasonal, and (c) inactive.
See this image and copyright information in PMC

References

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