Penn State NASA

Cone of Depression

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Cone of Depression

Schematic showing development of a cone of depression as a result of heavy pumping
Schematic showing development of a cone of depression as a result of heavy pumping
Click for a text description of the cone of depression diagram.

a diagram illustrating the impact of pumping wells on the water table, titled "Pumping wells can drawdown the water table." It features a cross-sectional view of a landscape with trees, a stream on the right, and a cloudy sky with precipitation. The diagram shows precipitation falling from clouds, infiltrating into the ground, and contributing to the water table. A pumping well is depicted, extracting groundwater and causing a drawdown or lowering of the water table. Arrows indicate groundwater flow toward the well and a confining unit beneath the surface. The stream on the right is shown as part of the groundwater system.

  • Surface Features
    • Sky: Cloudy with precipitation
      • Visual: Gray clouds with raindrops
    • Land: Green trees and brown soil
    • Stream: Blue water body on the right
  • Water Processes
    • Precipitation
      • Position: Top, falling from clouds
      • Visual: Black arrows pointing downward
    • Infiltration
      • Position: From surface into the ground
      • Visual: Arrows moving downward through soil
    • Water Table
      • Position: Boundary between unsaturated and saturated zones
      • Visual: Dashed line affected by pumping
  • Pumping Well
    • Label: Pumping well
    • Position: Center, extracting groundwater
    • Description: Causes drawdown of the water table
    • Visual: Well structure with arrows showing water extraction
  • Groundwater Flow
    • Position: Below the water table, toward the well
    • Visual: Black arrows indicating flow direction
  • Confining Unit
    • Position: Bottom layer
    • Description: Impermeable layer beneath the aquifer
    • Visual: Brown layer at the base
Credit: USGS

Overuse of groundwater does not have to lead to major land subsidence before it causes problems. On a more local scale, over-pumping can result in lowering of the water table in a process called “cone of depression,” a generally concentric pattern of water table drawdown. Such over-pumping often results from industry or agriculture, but individual landowners often feel the repercussions.

Alternatively, a cone of depression can result when housing developments, particularly those with many small lots, use wells for water supply. A cone of depression can drastically decrease water pressure, or worse, lower the water table below the level of the well, leaving a home or a farm without a water supply. The only solution for this is to drill the well deeper, which can be an expensive proposition for an individual landowner. Left unchecked, a cone of depression can modify the flow of groundwater as well as the distribution of pollutants,