Which term describes a well that is under pressure?

The term that describes a well that is under pressure is the artesian well. An artesian well taps into a confined aquifer where the water is under pressure due to the weight of the overlying water and rock layers. This pressure allows the water to rise to the surface naturally without the need for pumping, sometimes resulting in the water flowing freely above ground.

In contrast, a shallow well draws from a water table that is relatively close to the surface and does not have the same pressure as an artesian well. An injection well is specifically designed for the purpose of injecting fluids underground, typically for disposal or for enhancing resource recovery, and does not refer to the natural pressure condition of the water. An observation well is used primarily to monitor groundwater levels and quality, rather than to access water under pressure.

Understanding the characteristics of artesian wells helps in appreciating groundwater dynamics and their importance in water distribution systems.