Colman McCarthy's article [oped Aug. 29] on the filthy, undrinkable water furnished to the black citizens of Gifford, Fla., and his passing mention of water crises worldwide make one reflect that a couple of thousand years ago such matters were handled rather better.

It was the Roman who first got their priorities right. Well, almost right: They depended on slaves to build and maintain the waterworks. But, as the hundreds of ruined aqueducts that meet the eye from Mesopotamia to France and Spain demonstrate, the Romans' summum bonum was pure water. It took, in addition to slaves, much money, enormous pains and some highly sophisticated engineering to get it.

Rome itself had an underground channel for its water supply as early as the third century B.C. Six hundred years later no less than 11 major aqueducts, stretching over great distances, were supplying the city. The enormous Pont du Gard, in Provence, rising on three tiers of arches more than 150 feet, carried 100 gallons of water a day for every inhabitant of Nimes from a source more than 30 miles away.

Wherever Romans lived, whether in the capital or the far-flung provinces, their first thought was to get unpolluted water. The remains of dozens of great aqueducts can be found along the 300-mile south Turkish coast, drawing a never-failing supply of ice-cold water from the melting snow in the Taurus Mountains behind the littoral. They run not only to the large cities but to small towns of only a few hundred inhabitants.

One, at Aspendus, marches up and down hills and valleys on huge arches and is, necessarily, a syphon system. The water runs through stone pipes, interspersed with settling tanks to take out any gravel that may have intruded and also air bubbles, which the builders believed would have increased friction at points where the flow was made to turn corners.

The ruins of the nearby city of Side show a chain of events. In its early period when it was a Greek colony, it relied on cisterns filled by winter rains and a spring-fed pool, rediscovered a few years ago with cyprus pilings - part of a waterworks structure - still preserved in the mud. When the Romans took over they were obviously dissatisfied with such a potentially impure supply and built an aqueduct running 18 miles back into the mountains.

Its source was a beautifully constructed sluice of limestone slabs where the ancient Melas River exploded through a rocky gorge. Beyond that point the mountains are so rugged that there could have been no human habitation upstream on the river and its tributaries for 50 miles or so and, hence, little possibility of contamination. The water was carried down to the city over arches - 40 of them across one valley and in other places two or three tiers high - or in stone troughs four feet wide and five feet deep following the contours or in man-high tunnels through the mountains. It was a gravity system, with a vertical drop of one foot for every 1,000 feet in horizontal distance, bespeaking pretty fancy engineering. It dates from the second century A.D.

At Side, as in most Greco-Roman cities in the Mideast, the inhabitants made a big thing of the completion of their water-supply system, erecting ceremonial and celebratory buildings, nymphaseums, at the terminal. That is Side is an elaborate structure, three stories high and 75 yards wide, with three big semi-circular niches in its facade, with three large spouts in each, tumbling water into an almost Olympic-size pool in front. The building was faced with marble and richly decorated with columns, statues and friezes. In the neigboring city of Perge there are three nympheums, replete with heroic-size statues of the local water god and convocations of others of the Greco-Roman pantheon.

The Romans also knew how to put their water to use once they got it. In Side, for example, there are three gigantic baths, a long section of the main street lined with fountains and pools below them, one surface and one sub-surface channel running the whole length of the street and a cut-stone ditch in which water coursed merrily and hygenically under the score or so of marble seats in the city latrine, built, conveniently, next to the theater.

An inscribed statue pedestal in the town reveals that the aqueduct fell into disrepair in the third century A.D. and that a rich Sidetan paid for putting it back in order. His statue is gone, but a glowing poem of praise to him can still be read.

Perhaps, if the commissioners of Indian River County piped decent warer to the citizens of Gifford, they might erect a similar memorial. The prospect might move the officials to action when, as McCarthy reports, nothing else has.