EVERYONE has long agreed that Venice must be saved. The question now is, saved from what: damage from surging tides, an ebbing local population, a stagnant economy, or simply an uncontrolled flood of tourists? In October two costly plans to save the 1,200-year-old city that is laced with the world's most wondrous waterways got a liftoff in the Venetian lagoon.
But the projects have completely different thrusts, triggering an energetic debate over which is the best way to keep Venice - reverentially referred to as the Serenissima (the most serene) - alive.
One proposal is a $2.6 billion project - reflecting a strictly preservationist approach - that is designed to protect Venice from the plague of acqua alta, or high water, and to restore the fragile ecology of the surrounding lagoon.
There is also a plan to promote the economic revival of Venice through the city's candidacy for the next world exposition in the year 2000.
The first plan, presented in October, centers on the regulation of Venice's treacherous tides with retractable floodgates. It is being launched by a consortium of major Italian companies 23 years after all of Venice was submerged under stormy floodwaters.
Giovanni Mazzacurati, director of Consorzio Venezia Nuovo, warns sharply that time is running out if another catastrophe like the one in 1966 is to be avoided.
``The danger already exists now,'' says Mr. Mazzacurati, adding if another such acqua alta were to strike an undefended Venice today, the magnificent marble palazzi lining the canals would risk collapse.
The idea to host the universal exposition in Venice is being floated by another consortium as an ideal way to build up the city's ancient infrastructure and inject the economy with new investment.
But critics argue the plan might just sink the city altogether under the weight of too many tourists.
Stefano Boato, an urban specialist and member of the Venice City Council, contends that Venice simply could not withstand the onslaught of daily visitors that he says would instantly double to more than 80,000 with a universal exposition.
``Venice's candidacy is not even thinkable,'' inveighs Mr. Boato. ``It would mean the total collapse of the city,'' he insists, predicting the exposition would paralyze Venice with perpetual gridlock in the city's canals and narrow streets.
Boato notes that Venice already suffers from too many tourists: authorities today are forced to close off access to the city around 10 times a year during Easter and summer vacations because of overcrowding.
Furthermore, Boato argues if the Venetian economy is even weighted more heavily towards tourism ``it will only accelerate the exodus of Venetians from Venice to the mainland.''
With a total population of around 80,000, there are fewer than half the Venetians there were some 38 years ago. No longer able to afford pricey real estate that one-time foreign tourists are now snapping up, Venetians are moving out.
The lagoon's population drain is also being stimulated by a scarcity of jobs in fields other than tourism.
Venice's entire city council is now on record against the exposition.
In October, when a Paris-based commission charged with choosing a suitable site for the fair came to Italy, the council lodged a protest with them and filed petitions by sympathizers and urban specialists. The commission is expected to make its decision next spring.
MEANWHILE, as the debate swirls around the future of Venice, the problem of high tides is steadily getting worse.
The combined effect of the sinking of the ground on which Venice sits and rising sea level has caused the city to drop some nine inches since the beginning of the century, according to experts.
Venetians themselves have contributed to the city's plight by digging deeper channels for ships and draining underground water for industrial use in the past few decades.
Before 1920, notes Mazzacurati, St. Mark's Square was covered with water about seven times a year. Today, the square is transformed into a shallow lake approximately 45 times a year.
Under the proposed plan, by 1994 some 100 highly sophisticated mobile gates would be installed at Venice's three outlets to the Adriatic Sea.
Each port opening could be sealed off during seasonal high waters and would otherwise remain open to navigation and allow water to circulate.
The mobile gates - each measuring 65-feet wide - will be hinged to an underwater foundation and are designed to undulate with the waves. Normally invisible, the gates would rise in unison from the bottom of the lagoon during exceptionally high tides.
The prototype of the gate is called the MOSE Modulo Sperimentale Elettromeccanico (Electromechanical Experimental Module).
The acronym has become a symbol of Venice's salvation: the Biblical Moses saved his people from the perilous waters of the Red Sea and the latter-day MOSE is being built to save Venice from the devastation of high tides.
Recently, the MOSE successfully completed a year-long test in the lagoon. The MOSE's successors will be designed with a 50-year life span and can be periodically replaced for maintenance.
Final government approval for the project is now pending, but Mazzacurati is confident there is now a political consensus supporting the consortium's proposal.
The Italian government will also have the last word in the exposition debate should the Paris commission decide in Venice's favor over Toronto and Hanover, West Germany.
The plan to host the fair has the strong backing of Italy's Foreign Minister Gianni De Michelis, Venice's most prominent native and the exposition's chief champion in the coalition government.
ALSO promoting the expo idea is a powerful consortium of around 40 Italian companies eager to cash in on prospective construction contracts.
Preparation for the exposition, in fact, might include the building of a subway system and a congressional center.
Mr. De Michelis has dismissed criticism of the plan based on fears of overcrowding. ``It's precisely because the flow of tourists is destined to increase that Venice must equip itself to handle it,'' reasons the foreign minister.
Just how prepared Venice is to handle a huge surge in tourism came into question last July, when a free rock concert staged in St. Mark's Square by the British band Pink Floyd turned into a debacle.
The concert drew 200,000 youths from around the country, but not even the most rudimentary preparations, such as the building of outhouses, were made to accommodate the crowd.
The result: vibrations from the amplifiers damaged some nearby marbles, a door to the adjoining Ducal Palace was battered down, and the square itself was afterwards awash in a sea of trash and broken bottles.
Another casualty of the concert was the city council, which resigned the next day in shame. When a new council convened, it solemnly vowed to oppose any such mass activities in the future, in particular the world expo.