In the following figure, AQTESOLV predicts drawdown due to an irrigation well extracting water from a nonleaky confined aquifer with daily on/off cycles extending over a growing season of 245 days. During each pumping cycle, the well withdraws groundwater at 220 gallons-per-minute (gpm) for 12 hours followed by 12 hours of recovery. At the end of the growing season, all pumping stops and sustained recovery begins. Drawdown in the pumping well (blue line) clearly shows the cycles of intermittent pumping; whereas the two observation wells (red lines) located 500 and 2000 ft from the extraction well demonstrate how the cyclic drawdown response dissipates with distance.
|Drawdown due to intermittent (cyclic) pumping in a nonleaky confined aquifer.|
If your primary interest is the average drawdown at relatively distant observation wells over long periods of intermittent pumping, it is often sufficient to assume a constant average pumping rate. The following figure shows the predicted drawdown for a well extracting at 110 gpm over the same 245-day growing season as the previous intermittent pumping scenario.
|Drawdown assuming average pumping rate in a nonleaky confined aquifer.|