Pursuit of Florida dreams fouls our waters.(The Orlando Sentinel)

ORLANDO, Fla. _ Spanish explorer Juan Ponce de Leon was looking for the fountain of eternal youth when he waded ashore on the eastern coast of Florida in 1513. He never found it.

During the next five centuries, millions of settlers who followed would bring more attainable visions to Florida: The fertile farm. The thriving industry. The perfect lawn.

Those lesser dreams all came true, but at a cost of contamination to the state's precious water supply that we are paying now.

The human desire to improve upon paradise with machinery, chemicals and commerce has fouled the fresh waters on Florida's surface. It also threatens our unseen sources of drinking water in ways every bit as real as the over-pumping that's predicted to draw the aquifer down to dangerous levels in some places by 2006.

"We've turned the corner on acknowledging the problem, but I'm not sure we have turned the corner on doing anything about it," said Ed Fernald, professor emeritus of the Department of Geography at Florida State University and co-editor of Water Resources Atlas of Florida.

Many of the forests and native scrublands in the watery paradise of 1513 have been cleared for chemically dependent citrus and vegetable farms. The swamps have been drained for homes and high-maintenance, foreign-grass lawns. Oily roadways have bisected the lakes and streams. Open prairies have been scarred by mines, trampled by cattle or swallowed by theme parks.

One thing that has not changed in five centuries: Florida's hydrological cycle. The tropical rains fall onto porous ground that soaks up water like a vast sponge. So as we reshape the state's surface, much of our modern pollution simply goes down, into the ancient darkness of the sponge from which we drink.

The major challenges we face:

_ Florida's unique geology makes it vulnerable to groundwater contamination from activities on the surface. Already, hundreds of private wells in some areas have been contaminated and the future safety of deeper wells where most public drinking water comes from is unclear.

_ Florida is still confronting the legacy of decades of farming practices that polluted private drinking wells with health-threatening chemicals. The state's world-famous citrus industry, for example, has contaminated aquifers near the surface with a host of now-banned pesticides and fertilizers linked to ailments such as cancer or liver disease.

_ Industries ranging from phosphate mining to pulp mills to dry-cleaning businesses have fouled the state's waters. Though three decades of U.S. Clean Water Act reforms have stemmed the tide of industrial pollution nationwide, the byproducts of industry in Florida have proved dangerous, hard to police and difficult to clean up.

_ As Florida grows, it will be at the forefront of the nationwide struggle to control pollution that is even more widespread and problematic_polluted stormwater runoff. Waves of current and new Florida homeowners who use pesticides and fertilizers in their search for lush lawns are major contributors to this toxic soup.

One of the newest, most-worrisome threats to Florida's water may come from an old source _ the nitrates that have long been a common ingredient in farm, lawn and garden fertilizers. Nitrate levels have been regulated in drinking water for a long time. The primary threat was …