Ground water Explained

Ground water is precipitation that infiltrates the surface to enter and move through the top of the vadose zone. This zone includes all earth material above the water table. This earth material includes soil, alluvium, and rock. Water moves through the vadose zone, which is seldom saturated.

The vadose zone has special significance because it is a source of pollutants as the water goes through on the way to the water table. It is an area of early warning for potential pollution to ground water resources.

Water that goes through the vadose zone may enter the ground water system, or zone of saturation, where saturated flow occurs. The upper surface of this zone is called the water table. The capillary fringe just above the water table is a belt of variable thickness where water is drawn up by capillary action. This is due to the attractive force between water and the surfaces of earth materials, and to surface tension (attraction of water molecules to each other).

Other sources of ground water, besides precipitation include

• lakes and rivers
• artificial recharge (surface water purposely injected into ground water system)
• stormwater retention or recharge ponds
• agricultural irrigation
• wastewater treatment systems such as cesspools septic tank drain fields

Movement of water into the zone of saturation and through earth is an important part of both the hydrologic cycle and the rock cycle. Water may dissolve minerals from materials as it moves through and deposit them elsewhere as cementing material, producing sedimentary rocks. Ground water may transport sediment, heat, gases, and microorganisms.

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