Paterson must come to his senses and recognize that the state Department of Environmental Conservation, under Commissioner Pete Grannis, has betrayed its mission by moving to okay as many as 6,000 gas wells in the watershed that provides the lifeblood of the region.

Don't take our word for it. Listen to the concerns raised by fellow environmental authorities.

A report commissioned by the city's Department of Environmental Protection concluded: "Intensive natural gas development in the watershed brings an increased level of risk to the water supply: risk of degrading source water quality, risk to long-term watershed health . . . risk of damaging critical infrastructure and the risk of exposing watershed residents and potentially N.Y.C. residents to chronic low levels of toxic chemicals."

The federal Environmental Protection Agency found Grannis' department had failed to consult necessary experts, such as the Department of Health, and so had failed to consider "potential risks associated with gas drilling activities in the New York City watershed and the reservoirs that collect drinking water for 9 million people."

Oh, that.

Grannis' environmental impact statement was so off the wall, he proposed opening the door to gas drilling anywhere in the watershed more than 300 feet from a reservoir. In five-borough terms, that's roughly equivalent to installing an industrial facility a block from the water's edge.

Why is the DEC playing Russian roulette with the drinking supply? Because a huge deposit of natural gas is trapped in a vast subterranean formation of soft rock called the Marcellus shale. The watershed sits atop one edge of the Marcellus, which extends under 22 New York counties and stretches as far as West Virginia.

The gas can be tapped with a technology called high-volume hydraulic fracturing, or fracking. This involves drilling more than a mile into the shale, then pumping great volumes of water and chemicals down to shatter the rock and release the gas.

Upstate Broome County has estimated that as much as $14 billion in economic activity could be generated by tapping its shale gas, which explains why state officials might be a bit dazzled. They must get over their gas fever when it comes to the city's water - and stop taking at face value industry assurances that drilling poses no risk. The reservoirs are New York's single most critical asset.

Despoiling water that is pristine and naturally filtered would be epochally criminal - as well as costly. The remedy would be to spend billions of dollars building and operating filtration plants.

Chesapeake Energy, which owns rights to drill in the watershed, says it won't exercise them, and that's good. But not good enough. There must be a law to protect the city's water, now and forever.