Clean Water: Groundwater [b]

G R O U N D W A T E R

Groundwater reservoirs are stocked with water when rainwater or irrigation filters through the ground, collecting and saturating the spaces between rock and sediment particles. The deepest groundwater is rarely found below x depth because the spaces close at depth. The top of the underground water surface is called the water table.

Fig. Groundwater animation.

As water moves downwards to the water table, some it clings to the surface of particles and never joins groundwater. This is soil moisture rather than groundwater. Most garden plants love soil moisture, but not standing water. Occasionally, the water table is at the ground surface and standing water occurs.

Groundwater is accessible if we suck up the water underneath with a straw - the straw is a well and we use a mechanical pump for suction.

Some groundwater is full of so many dissolved chemicals that it's not fit to drink. Other places have pristine ground water.

Movement through the ground can be remarkably purifying. Many rural residents have septic tanks instead of municipal sewers. In a septic tank, household sewage is allowed to flow into the ground. Many people with septic tanks also have water wells that supply their tap water. Given a safe distance between the two, the same water that came into the ground as sewage becomes clean enough to drink.

Groundwater is an important source of water in semi-arid environments. Where there isn't enough surface water, wells tap into groundwater resources. Unfortunately, groundwater reservoirs are not replenished very fast in dry environments. In many of these areas, groundwater tables are falling because of overdraft - taking out water faster than it's coming in. This downside has also been a downslide - the land surface has actually sunk by as much as x feet in some areas because of overdraft.

Since groundwater is such an important water resource and it takes so long to replenish, the effects of polluting groundwater have long term effects.

PART 1
Water on Earth
• Overview
• Stores of Water
• Infinite cycle:
finite resource
• Sculpting the earth
• What's left to drink?
Quiz
Glossary
Resources
Teacher's guide
Information Sources

• Activity Groundwater.1
Investigate contaminants:
MTBE in drinking water
U.S. EPA Office of water

• Activity Groundwater.2
Septic Tanks
The ground is a natural purifier for water. Septic tanks work on that principle. They are effective enough for absorption fields and drinking water wells to be within 50 feet. See how home septic systems work.
Purdue University and U.S. EPA

• Activity Groundwater.3
Bioremediation: Nature's way to a cleaner environment
How we can enhance the natural ability of microorganisms in soils to break down undesirable organic chemical compounds.
U.S. Geological Survey

• Activity Groundwater.4
Ground water and drinking water
U.S. EPA Office of Water