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: These results indicate that the percentage of arsenic-bearing water in the well decreases as the average winter pumping rate increases, thereby producing more water from shallow depths in the aquifer. The percentage of arsenic-bearing water produced by the well during the winter can be reduced from 55% to 45% by increasing the current average winter-pumping rate from 1380 to 2160 L/s, which would only reduce the arsenic concentration of pumped water by 1 to 2 µg/L (Figure 7). The asymptotic shape of the relationship between the percentage of arsenic-bearing water and the average winter-pumping rate indicates that little additional benefit could be gained by any further increase in the pumping rate.