With a healthy concoction of ions and trace metals, the Edwards Aquifer naturally produces some remarkably good H2O. The trusty aquifer serves the diverse agricultural, industrial, domestic, and recreational needs of almost two million people in South Texas, namely those in San Antonio, the seventh largest city in the U.S.

Aquifers are important underground reservoirs that store mass amounts of water relatively free from evaporation loss or pollution. Rainfall and seepage from streams and crevices in the sprawling Edwards Plateau continuously replenish the underground water supply, ultimately pushing the water through miles and miles of cavernous limestone beneath the earth's surface.

The aquifer is divided into three main zones: the contributing zone, the recharge zone, and the artesian zone. The contributing zone is about 5,400 square miles of rugged hill country, covered in oak and cedar. It is home to a number of endangered species, with the land itself the subject of environmental concerns. Also called " the drainage area " or " the catchment area " because of the way the land surface " catches " water from rainfall, this zone receives an average of 30 " of precipitation every year. The water then runs off into streams or into the water table aquifer of the plateau, and eventually over the limestone into the recharge zone.

The recharge zone is a 1,250 square mile area where faulted limestone covers the surface, allowing large quantities of water to flow into the aquifer. Seventy-five to eighty percent of recharge occurs when water from streams and rivers enter through faults and fractures, with only a small percentage due to rainfall on the outcrop of limestone. Recharge, of course, varies greatly from year to year, depending on the amount of rainfall.

Once gravity helps the recharge water work its way down into the artesian zone, the water is trapped inside. The artesian zone of the Edwards, therefore, is defined by the water being sandwiched between two relatively impermeable rock formations, the Glen Rose formation on the bottom and the Del Rio Clay on top. The weight of the recharge water entering the aquifer puts tremendous pressure on the water that is already deep down in the formation. The hydraulic pressure forces water up through wells and faults to the surface, resulting in major natural discharge of clean water.

To learn more about this amazing natural resource and future alternatives, contact The Edwards Aquifer Authority at (210) 222-2204 or 1-800-292-1047, or visit www.edwardsaquifer.org.