Water supply vs. city expansion - how Florida communities plan ahead

City workers in this central Florida city are going door to door offering to install water-saving devices on showers, sinks, and toilets. ''We're very conscious of water here,'' says Robert Haven, Orlando's public works director. ''We started the program near the end of a drought in June 1982 .''

All across Florida, officials are looking for ways to save water. Although the state was mostly swamp until the turn of the century, and rains can be torrential during the summer, Florida has been so well drained that water will be a limiting factor to the state's growth, some planners say.

Water-rich rural areas are wary of water-poor coastal cities. Water managers say that if well fields in some rural areas are pumped much more, the loss of ground water will cause environmental damage.

But water management officials say plenty of water will be available into the next century if municipalities, industry, and farmers don't waste it.

''Water is not a limiting factor for the growth of southwest Florida,'' says Gary Kuhl, director of the 16-county Southwest Florida Water Management District. ''But growth has got to be managed to mesh with the water supply. There's plenty of water available. We just have to be smarter in how we manage it.''

Mr. Kuhl points to the Orlando plan as one example of how water resources can be stretched, and Mr. Haven says a sampling of 500 of the 33,000 homes here that have had the conservation devices installed show a savings of about 18 percent in water consumption.

That not only helps Orlando save water, he says, but it also allows more homes to be hooked up to the city's sewage treatment plants without expensive new construction. He figures that the $750,000 spent to install the water-saving equipment will save about $10 million worth of sewage treatment expansion.

Among other water conservation and management plans under way in the southwest Florida are:

* A study to pump millions of gallons of highly treated waste water from Tampa's sewage treatment plant to the Hillsborough River where it would flow downstream to the city's reservoir. That waste water now is so highly treated that it is nearly pure enough to drink, but it is being released unused into Tampa Bay.

* Through a process called reverse osmosis, salt and brackish water can be made pure. New developments in reverse osmosis have allowed the coastal city of Venice to produce about 2 million gallons of pure water a day at a cost of 44 cents for each 1,000 gallons. That's not much more than other coastal residents are paying to get water pumped to them from inland well fields.

* By the end of the year, a new state law will require developers of tracts larger than 100 acres to get permits from water management districts. The law will encourage developers to retain storm water on their property. That would allow water to percolate into the ground-water supply, rather than be drained quickly off the land.

* Manatee County, directly south of Tampa, has just installed a system that takes water from the Manatee River, treats it, and then pumps it underground. The treated water will force out the present ground water, which is high in impurities. Then, during dry spells when the Manatee River is low, the pure water will be available for use.

* Farmers are being encouraged to look at irrigation systems that use less water or that lose less water through evaporation. Systems such as drip irrigation have been used by the Israelis to grow crops in the Negev desert where water is at a far higher premium than in Florida.

''Our permitting program is where we have the most teeth to get these programs initiated,'' Kuhl says. ''But we would like to do it without confrontation. We're here to provide assistance and encouragement.''

Big water users who come to the Southwest Florida Water Management District for pumping permits will be asked to look at alternative ways of providing water rather than pumping it from well fields in central Florida, he says.