A distance-drawdown curve flattening at a distance from the pumped well indicates which boundary condition?

• A. Constant-head boundary
• B. Recharge boundary
• C. Leaky boundary
• D. Impermeable boundary

Answer: (D)

When you pump from a well, the drawdown you measure at various distances shows how far the pumping influence reaches and how surrounding boundaries constrain flow. If there is an impermeable, no-flow boundary, the flow field created by the pumped well cannot cross that boundary. The cone of depression expands until it encounters the boundary, and beyond that boundary the boundary condition prevents any further change in head due to the pumping. As a result, the distance-drawdown curve levels off or flattens at the distance where the boundary lies, indicating the influence of an impermeable limit. Other boundary types involve ongoing exchange or leakage that keep altering the drawdown pattern with distance, so you wouldn’t expect a clean flattening at a finite distance in those cases.