You probably recall hearing water facts in elementary school. Perhaps you even learned them. For instance, do you remember how much of the earth’s surface is covered by water? It’s 70%. In our day-to-day lives, we use large quantities of water without thinking much about how it reached us (and that’s especially true for those of us near the Great Lakes). It’s time for some reconsideration. Let us refresh your memory by sharing these facts about groundwater, aquifers, and the water table.

Of all the water on earth, only 1% is readily available for use because we cannot drink the salt water of oceans. Ocean water constitutes the majority of the 70% of the earth’s water. Furthermore, of the 1% of usable water, 99% of it lies under the ground. It is located beneath the earth’s surface, filling the spaces between soil particles and fractured rock.

Groundwater is used for drinking water by more than 50% of the people in the United States, many of whom live in rural areas. Another important use of groundwater is for the irrigation of crops. Its supply is replenished by any form of precipitation that seeps into the cracks on the earth’s surface. In areas that depend greatly on groundwater, water shortages occur when the groundwater supply is depleted before it can be replenished. Groundwater is used in many industrial processes and also feeds streams, lakes, and rivers. (If you’ve ever wondered why rivers keep flowing even when there’s been no rain, there’s your answer. Groundwater continues to feed the river, even in times of little precipitation.)

An aquifer is a body of saturated rock that water can easily move through. An aquifer usually consists of sand, gravel, sandstone, fractured rock, or some other type of stone. Holes are often drilled into the ground to penetrate an aquifer and create a well. Aquifers are natural filters because they trap sediment and bacteria, providing natural purification of the groundwater that flows through it.

The water table can also be called the groundwater table. It is the upper layer of the saturation zone underneath the surface of the earth. It fluctuates from season to season and year to year depending on weather conditions. Water tables are diminished when wells are drilled to draw water from the table through aquifers. In Wisconsin, about two thirds of our drinking water comes from groundwater. As you can imagine, it is vital that our groundwater remains uncontaminated since we depend on it so heavily.