One hard rainfall won't even come close to solving the unprecedented drought withering much of Florida.

Lake Okeechobee, the heart of the Everglades and a backup drinking water source for millions of South Florida residents, has been hitting a record low almost weekly. Its main artery, the Kissimmee River starting near Orlando, hasn't flowed south in more than 240 days, depriving the lake of 50 per cent of its water.

Water managers say the Kissimmee River basin needs about 5 feet of rain --  just to catch up.

The 18-month dry spell means continued pressure on the region's utilities to find alternative sources of clean water, such as desalinizing sea water.

It also has put renewed pressure on water managers to hasten efforts to engineer nature to work more naturally.

Florida's natural water system has been so manipulated over the last century to make way for man that the only way to restore it is to manipulate it even more, state officials say.

The state and the federal government already have spent millions on restoration of the Everglades, the largest such project in the world.

"You can't just backfill everything and let the water flow like it used to because we'd be drowning out people, highways, farms and homes," said Ernie Barnett, director of policy and legislation for the South Florida Water Management District. "We now have to engineer a solution to mimic nature."

One of the district's most pressing needs is to find storage sites on land north of Lake Okeechobee, the second-largest freshwater lake entirely within the contiguous United States, to capture water during wet times so it can be slowly released during dry periods.

That process once occurred naturally before flood control diversion projects prevented storm overflow from spreading out over surrounding wetlands. Now, when rain falls heavily during normal wet years, overflow polluted with farm and urban runoff flows south into the lake and eventually is pumped east and west through rivers into the ocean.

"If you had a way to capture it and store it and then, when it's dry, put it back into the natural system, mimicking what nature used to do, that's really what Everglades restoration is all about," Barnett said.

"True restoration is going to rely on catching the water earlier and cleaning it up before it gets into Lake Okeechobee," said George Horne, the district's deputy executive director of operations and maintenance.

"The real answer is conservation if we want to continue to have population growth. And that means tough growth control decisions and alternative water supplies," Horne said.

Environmentalists argue that Florida's drought is exacerbated by the district's continued manipulation. They say nature can't be restored with more manipulation alone, such as simply building reservoirs to store water.

"If we want to recreate the Everglades natural drought resistance, which was always there before the government started manipulating the system, then we've got to be able to put water back onto the landscape and that means back into places that people are using right now," said Eric Draper, policy director for Audubon of Florida.

He said the state must recognize that in order for true Everglades restoration to be successful, and for water to return to its historical abundance in South Florida, land in the flood plain has to be reclaimed for natural water storage.

"We're in such a severe drought now because water managers have deliberately lowered the lakes and drained the swamps in the entire Everglades system," Draper said. "We've got to allow the lakes and rivers and streams that make up the Everglades to overflow back into the flood plains naturally."