Groundwater is the water found underground in the cracks and spaces within soil, sand, and rock formations known as aquifers. Extracting this water requires specialized infrastructure to reach the saturated zone and machinery to bring the water to the surface for use in agriculture and drinking. The process involves establishing a stable access point and applying mechanical force to overcome the downward pull of gravity.
Creating the Pathway Well Construction and Design
The initial step in accessing groundwater involves drilling a borehole deep enough to penetrate the water-bearing aquifer. Drilling methods, such as rotary or cable tool techniques, are used to create a vertical shaft that extends far below the static water level. This ensures a reliable supply even when the water table fluctuates. Once the borehole is established, a well casing, which is a large pipe often made of steel or PVC, is inserted to line the borehole and maintain its structural integrity. The casing prevents the surrounding unconsolidated earth materials from collapsing into the open shaft.
The lower section of the casing, which sits within the water-producing zone, is replaced with a specialized component called a well screen. The screen is designed with precise openings or slots that allow groundwater to enter the well while simultaneously filtering out the surrounding sediment particles. Proper sizing of the screen slots is determined by analyzing the grain size of the aquifer material to ensure maximum water flow and minimal sediment entry. A gravel pack may also be placed in the annular space between the screen and the borehole wall to create an additional filter layer and further stabilize the formation.
Lifting the Water Common Pumping Technologies
Once the well structure is complete, a mechanical device is needed to lift the water column to the surface, and the choice of pump depends primarily on the depth of the water source. Submersible pumps are widely used for deep wells because they operate while fully submerged below the water level. These pumps use a sealed motor to drive a series of impellers, which impart kinetic energy to the water. The water is pushed upward through multiple stages of the pump and then forced through the discharge pipe to the surface. Because they push the water rather than pulling it, they are highly efficient and are not limited by the atmospheric pressure constraints that affect suction-based pumps.
Jet pumps, in contrast, are typically installed above ground and are better suited for shallower wells, generally limited to depths of about 25 feet. This type of pump uses an electric motor to spin an impeller, which pressurizes a portion of the water and sends it down a drive pipe into the well. This pressurized water is forced through a narrow nozzle, creating a high-velocity jet that causes a reduction in pressure, known as the Venturi effect. The resulting vacuum draws the standing well water into the system, where it mixes with the drive water and is then carried back up to the surface. Deep well jet pumps use a two-pipe system to extend their effective depth to around 150 feet, though with reduced efficiency compared to submersible models.
For low-volume or domestic use, particularly where electrical power is unavailable, reciprocating hand pumps are an option. These pumps rely on positive displacement, using a piston and cylinder mechanism. When the operator moves the handle, a rod moves the piston up inside the cylinder, creating a low-pressure zone that causes a foot valve to open and draw water into the chamber. On the subsequent downstroke, the water is displaced and forced past the piston or out a delivery spout, allowing water to be lifted from depths up to 80 meters, depending on the pump design.
Extraction Without Pumps Understanding Artesian Wells
In certain geological formations, groundwater extraction is possible without the use of any mechanical lifting device. This occurs in artesian wells, which tap into a confined aquifer. A confined aquifer is a permeable layer of rock or sediment that is sandwiched between two layers of impermeable material. The water enters the confined aquifer at a higher elevation, which creates a natural pressure head throughout the layer.
When a well is drilled into this confined space, the water is under hydrostatic pressure greater than the atmospheric pressure at the surface. This natural force pushes the water up the well bore without external energy input. If the pressure is sufficient to push the water all the way above the ground surface, the well is referred to as a flowing artesian well.