THERE are those who won't drink it at all - they prefer Perrier or Evian. But as urban tap water goes, the New York City variety - largely from the streams of the Catskills - has traditionally drawn high marks for taste and quality. Yet keeping that reputation, as New York City officials now know, requires vigilance. Increased economic development in watershed areas and tougher federal and state regulations have at last prompted the city's Department of Environmental Protection to take a wide range of steps to protect the quality of city drinking water against further slippage.
To counter increased pollution from sewage discharge and street runoff in the Croton System just north of the city, officials plan to build a new $600 million water filtration plant in the Bronx by 1996. The city also proposes a new set of rules governing development further north in the more rural Catskill-Delaware watershed that supplies 90 percent of the city's drinking water. The city may buy up some of the more environmentally sensitive land there.
The city also plans to upgrade its own sewage plants in that area and has threatened legal action against other owners who don't follow suit. Most have. ``I don't think they thought we were serious until we threatened to pull them into court,'' comments Ian Michaels, a spokesman for the city's Department of Environmental Protection (DEP).
The city has filed suit against developers who violate existing rules and against a few towns that deny the city a voice in watershed issues.
Under state law, the city has had the authority for 86 years to oversee and protect watershed lands. Yet the city has not revamped its drinking-water regulations since 1953. City environmental commissioner Albert Appleton concedes that the city was ``asleep'' and is now playing ``catch-up.''
Environmentalists, though critical of the city's failure to act more quickly, generally applaud the results.
``Until 1990 when Appleton came in, there had never been a prosecution of a polluter in the New York City watershed system,'' says Robert F. Kennedy Jr., a lawyer with the Natural Resources Defense Council. ``Now the city has brought a series of cases - it's finally starting to enforce the law.''
City environment officials are ``100 percent pleased,'' says Mr. Michaels, with the key decision this week of state health authorities not to require the city to construct a filtration plant for water from the rural Catskill-Delaware watershed.
US Environmental Protection Agency (EPA) regulations of 1986 require all surface water systems to have filtration plants unless officials convince regulators that their watershed protection programs are adequate. New York state health authorities, holding to their own stronger requirement, had proposed more than a year ago that a new plant be in place by 2005 for the Catskill-Delaware water.
City officials stressed the enormous cost of a second plant ($4 billion to $5 billion to build and $500 million a year to operate) and argued that preventing water pollution rather than trying to repair it afterwards made better environmental sense.
``This is a big victory for the environment,'' observes Robert Kennedy. He says upstate development interests backed the idea of a filtration plant and the high cost would have diverted funds for watershed protection.
Nationally, most of the nation's surface water used for drinking is put through only the most primitive kind of filter system, says Erik Olson, a lawyer specializing in environmental quality issues with the National Wildlife Federation. He says contamination from bacteria and chemicals remains a serious problem for drinking water: ``Filtration really is necessary for most surface water systems that don't have complete watershed protection.''
Recent tougher federal regulations are good, says Mr. Olson, but have not been enforced.
Developers and farmers in the Catskill region have made it clear in public hearings and written comments that they view the city's proposed watershed protection regulations as excessively strict. Farmers in particular want some adjustments.