Florida boasts at least 1,000 freshwater springs, more than any other U.S. state. They are all under threats from agricultural pollution, stress from untrammeled development and from climate change that is altering rainfall patterns.

Covering an estimated 100,000 square miles (250,000 square kilometers), the underground Floridan Aquifer is the source of 90% of Florida's drinking water. Because of the porous nature of the state's bedrock, millions of gallons of water find their way to the surface in the form of clear, clean springs that, in turn, feed into rivers.

The highest concentration of springs are in central and western Florida, including most of the 30 “first magnitude” springs _ those that discharge at least 65 million gallons (246 million liters) of water every day. All but four of them are considered polluted.

“We just have too much pollution going into the ground and too much water coming out of the ground,” said Ryan Smart, executive director of the non-profit Florida Springs Council. “And when you get that combination, you end up with springs that are no longer blue and vibrant and full of life.”

In the more rural parts of Florida, runoff from fertilizers and pesticides used in farm fields is a major part of the problem. Fertilizers containing phosphates and nitrogen tend to promote algae blooms that can slowly suffocate a spring, and livestock waste contributes.

Elsewhere in Florida, it's the rampant development that threatens springs. With over 1,000 people moving to Florida every day, more and more housing subdivisions are getting built along with the roads, strip malls, restaurants, golf courses and everything else that comes with it.

This means more impervious surfaces that prevent rainwater from percolating down into the aquifer and more pollutant-laden runoff from lawn fertilizers, parking lots, ever-widening roads and sometimes septic tanks. It also means more and more people, many of whom enjoy tubing, paddleboarding, kayaking and swimming in the springs.

It gets so busy in summer at some springs located in state and local parks that entry is halted by late morning.. At Ichetucknee Springs State Park north of Gainesville, the daily limit of 750 tubers on the upper river is often reached within an hour after the park opens.

“You cannot keep taking water out of the aquifer because it’s not an endless supply,” said Dennis Jones, a Republican former Florida legislator deeply involved in springs issues. “Permits for houses and condos and mobile home parks and golf courses _ it’s not sustainable.”

Florida spends billions of dollars every year on water quality projects, including about $800 million this year for Everglades restoration work. State funding for springs runs about $50 million a year, according to state documents.

Two state efforts at improving springs' quality, both around a decade old, remain bottled up in court and administrative challenges. One would strengthen rules for permits to draw water from the major springs. The other would enhance rules to reduce the amount of nutrients such as nitrogen and phosphates that goes into springs that are considered impaired.

Jones, the former legislator, said lobbying by powerful agricultural interests and related political pressures have blocked progress on the nitrogen reduction plan expected to take about 20 years.