Columbus, Indiana, obtains its water supply from six municipally owned wells southwest of the city. The wells are screened in an outwash sand and gravel aquifer that was deposited by glacial melt water in a preglacial bedrock valley. The well field is midway between the East Fork White River and the western edge of the valley.
A digital model was used to determine the effects of two pumping plans on the outwash sand and gravel aquifer. In pumping plan 1, a continuous pumping rate of 1,400 gallons per minute (88 litres per second) for 10 years in each of the city's six existing wells was simulated with the model. Model results of plan 1 indicate that the water levels in the area of the well field would be lowered more than 20 feet (6 metres) and that drawdowns in the wells would approach 35 feet (11 metres) after 10 years' pumping.
Pumping plan 2 had two stages of pumping. In the first, a continuous pumping rate of 1,400 gallons per minute (88 litres per second) for 5 years in each of the city's six existing wells was simulated with the model; the second stage of pumping plan 2 differed from stage 1 only in that five planned wells were added to the six existing wells. Model results of plan 2 indicate that water levels in the area of the well field would be lowered as much as 40 feet (12 metres). Drawdown at two of the well sites would approach 60 feet (18 metres), leaving less than 15 feet (5 metres) of the initial 70 feet (21 metres) of saturated thickness at the two wells after 10 years' pumping.
