Thirteen years ago, the humble little North Anna River was dammed to provide cooling water for Vepco's nuclear power plant here. The dam created a 10,000-acre public lake two hours from Washington and opened up winter bass fishing in a Brave New World.

From late fall through early spring, warm water discharged by the plant helps keep Lake Anna productive after other waters in the region go dormant. Starting about this time of year, diehard bass anglers have Lake Anna and not much else to amuse themselves with. And while the fishing here is difficult and demanding, it can be tantalizingly productive.

Lake Anna, in fact, has become Virginia's top producer of citation-sized largemouth bass. Through October this year, 36 bass eight pounds or better were registered here. In a distant tie for second place were Lakes Kerr and Gaston on the North Carolina line, with 15 citation bass apiece.

Interestingly, most of Anna's big bass are caught in the cold. Last March, for example, a month generally unfit for humankind to leave the house, 20 jumbo bass were checked in.

This fall, bass guide Gene Hord, with whom I had a chance to fish for two days last week, already has boated a 9-pound 10-ounce lunker. Earlier in the year, the biggest bass ever caught in the lake, a 13-pounder, was checked in by L.R. Owens Jr. of Ringgold.

When you toss in the fact that Anna has a burgeoning supply of crappie and striped bass, both notoriously active cold-weather species, you might begin thinking this lake is a winter pushover and head off down the road with a cane pole and a can of worms. That would be a mistake.

Anna, according to just about everyone, never is a pushover.

"I don't think I've ever had an easy day on this lake," said Hord.

For starters, in their quest to keep the cooling water free of trash, Vepco employes clean up every fallen tree almost the instant it hits the lake shore, according to Hord, leaving nothing along the banks to throw lures at. Anna's shoreline is so clean it's nearly sterile, and anglers are left with little to fish but the middle, which is unfamiliar water to most.

"Fishing this lake is like fishing the unknown," said Jack Randolph, state fish and game director. "You're in water 18 or 20 feet deep over terrain features you can't see. There's no current, so you can't say, 'This is good holding water.' It's a very hard place to fish."

"I'd rather be on moving water," agreed Dan Shuber, a state fisheries biologist. "Basically, I go to Anna for the big-fish potential. The people I know that fish there say, 'It may not be you, but someone fishing the day you're there is likely to catch a five-pounder.' You can't get that everywhere you go."

Even Hord, one of two full-time guides working the lake, along with veteran Bill Mathias, said Anna is tough. "It's a challenge," he said. "You have to expect hard days."

And after fishing with him in perfect weather for a day and a half, with two keeper bass of about two pounds apiece to show for it, I can attest that Lake Anna is no angler's picnic grounds.

"There's a creek channel here that joins a creek channel over there, and at the tip of the point there's rock bed that makes down to the channel edge. The bass will be holding over that point in 18 feet of water," said Hord as we pulled into a place that looked like plain, flat water.

He was reading bottom configurations off a complicated, gray-line depth recorder, the sort of gadget that would seem more appropriate in the emergency room at Sibley Memorial Hospital. This kind of fishing, I began to discern, might be a bit technical for a flounder-pounder from Long Island.

After three hours, my head ached with accumulated wisdom about stumps that lay 22 feet down in slack water. After five hours, my arm ached from heaving plastic worms and inching them along the bottom, praying for the bump that signified a sunken tree lying where the electronic machinery said it should.

And by the waning hours of Day 2, I was baffled, defeated and lost in a maze of 10,000 acres of invisible dropoffs, submerged rock ledges and drowned roadbeds.

That's how it seemed, anyway, until I stopped at the Sportsman's One Stop on the road home and bumped into Jack Christensen of Alexandria, who had taken a day off from the Treasury Department to go fishing in his little boat.

He had a whole box full of bass up to 4 1/2 pounds and some monster crappies, as well.

How did he do it?

Sat on a little point, he said, and banged away at the shoreline with a crankbait, the way bass fishermen have done for half a century.

Some things don't change.