Simulation of the effects of seasonally varying pumping on intraborehole flow and the vulnerability of public-supply wells to contamination.
Bottom Line: Simulation results indicate that both wells produce water requiring additional treatment to maintain potable quality in winter when groundwater withdrawals are reduced because less water is derived from parts of the aquifer that contain water requiring less treatment.Simulation results indicate that the water quality at both wells could be improved by increasing average winter-pumping rates to induce more lateral flow from parts of the aquifer that contain better quality water.Higher average winter-pumping rates would also reduce the volume of intraborehole flow within both wells and prevent the exchange of poor quality water between shallow and deep parts of both aquifers.
Affiliation: U.S. Geological Survey, Ridgway, CO, 81432.Show MeSH
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Mentions: The simulation results indicate that the percentage of nitrate- and uranium-bearing water in the well can be lowered by increasing the average winter-pumping rate, thereby producing more water from deeper depths in the aquifer. Model results using three different winter pumping rates indicate that the percentage of nitrate- and uranium-bearing water produced by the well can be reduced from 95% to 70% by substantially increasing the current average winter-pumping rate from 780 to 2270 m3/d (Figure 11). The asymptotic shape of the relationship between the percentage of nitrate- and uranium-bearing water and the average winter-pumping rate indicates that little additional benefit could be gained by any further increase in the pumping rate.