Valuable Ground Water Needs Protection
December 2, 2001

Drip...Drip...a leaky faucet is not only annoying, but can uselessly dribble away a precious natural resource. Where did the drops come from and where are they going? Surrounded, as we are, by rivers and lakes, an abundance of water is taken for granted, but would you eagerly sip a glassful dipped from Lake Michigan? Unless a community uses treated river or lake water, supplies come from hidden reservoirs of ground water. The idea that ground water is a completely renewable resource is only partly true.

Used and reused, water is mobile and restless. It moves in a circle from ocean to sky as water vapor, to land as precipitation, and back to the ocean via streams and rivers. But, there are many intermediate stops along the way. When it rains, some of the water flows on the surface and becomes concentrated in rivers and streams, some evaporates from the surface waters, a large amount is transpired by plants, the rest of it infiltrates the ground and moves downward into the subsoil, glacial drift and layers of rock. Ground water, then, is water contained in pore spaces beneath the earth's surface. The upper level of the zone of saturation is the water table. Ground water is moved by gravity or other pressure differences to reappear as springs, streams or wells, sometimes long distances from the point where it entered the earth.

Rocks or unconsolidated materials that contain and will yield useable amounts of water are called aquifers. Earth materials vary in their potential for containing ground water, depending on the available pore space. Crystalline rocks, such as granite and quartzite, contain only small amounts of water. Clays and shales may contain much water, but hold it so tightly that they tend to block its movement. Sandstones and deep glacial drift are excellent aquifers, holding a great deal of underground water. Limestone, the bedrock of our county, holds little water, but because of numerous cracks and faults, provides storage for a considerable supply. Water moving through limestone tends to be very hard due to the dissolved minerals which it contains.

About six inches of Wisconsin's average 30 inches of rainfall per year, re- charges the ground water supplies. This recharge occurs during the spring and fall months when evaporating and the needs of plants are at a minimum. No recharge is possible when ground is frozen.

Ground water is our "bank account" of water. When more is used than is returned, the supply becomes depleted. Water tables are lowered; wells must be drilled deeper. It is estimated that Wisconsinites use 600 millions of gallons of underground water daily. It is believed that this amount will be doubled during the next decade. We may be faced with the choice between using water for the current generation or conserving it for the future. Some states, where the water supply is less abundant, have already passed laws that control the use of ground water.

Ground water is a resource we seldom think about as long as it is available. We won't miss the water 'til the well runs dry!