BOYDTON, VA. -- Virginia Power officials, preparing to return Lake Gaston water levels to normal, say it will be months before they can determine whether the experimental drawdown cleared the reservoir of choking weeds.

"It's still premature, but based on what we know and have seen so far, it's dying back," Glenn Bishop, a Virginia Power environmental specialist, said this week.

An exotic weed, the Brazilian elodea, has hampered recreation on the 20,000-acre lake on the Virginia-North Carolina line. Since it was detected in 1982, the elodea has infested 300 to 500 acres in shallow depths of the reservoir.

Under the drawdown, the utility reduced the water level by nine feet in December and maintained it at the low level through January and February so the elodea would be exposed to freezing temperatures.

The weed has dried up and turned brown in many coves and along stretches of shoreline, Bishop said.

About 25 acres of hydrilla, another aquatic weed, have been found in shoreline areas of the lake. The hydrilla-infested acreage was treated with herbicide last week to head off growth of this weed where the elodea died.

"I think we're going to be really happy with what happened," Bishop said.

But he said the success of the drawdown cannot be measured until the weed begins growing again in May or June, and it will be September before officials know how much weed survived.

The drawdown was expected to control the weed, but not eliminate it. Depending on the drawdown's results, Virginia Power officials have said the reduction may be repeated every three to five years.

"I'm extremely hopeful," said Elton Brown, president of the Lake Gaston Weed Control Council. "This is at least a beginning. Now we'll have to see how it worked."

Virginia Power began slowly increasing the water level on Tuesday, and the elevation should be back to normal by April 1, officials said.

Randy Shillingburg, a Virginia Power spokesman, said the utility lost power generation while the lake level was below normal in January and February. But he said some losses were offset by generation gained as the level was reduced during December. The loss, he said, was "small and we're treating it like any cost of doing business."