Surging with runoff and millions of gallons of water from a swollen Kissimmee River Basin, Lake Okeechobee inched toward 18 feet above sea level on Tuesday, prompting water managers to open the floodgates even wider.

Officials with the South Florida Water Management District and the U.S. Army Corps of Engineers announced that they would begin "sustained" releases to sensitive estuaries along the Caloosahatchee and St. Lucie Rivers at levels that haven't been seen since the rainy El Nino year of 1998.

Water will surge to the Caloosahatchee at a rate of 9,000 cubic feet a second and the St. Lucie at 10,000 cubic feet a second. The level of the 730-square-mile lake stood at 17.82 feet above sea level, almost a foot above the 16.83 feet it measured a week ago. The highest level recorded in recent history was 18.77 feet in 1947. Officials refused to predict whether the lake would break that record this year.

"We still have more inflow than we have outflow," said Susan Sylvester, a water management technical specialist with the Army Corps in Jacksonville. "I've given up making predictions."

Water managers begin releases from the lake, and periodic inspections of the earthen Herbert Hoover Dike that surrounds it, when the lake level reaches 17 feet.

"One of the primary concerns is the integrity of the dikes when the water level reaches that high, but we also worry about what the water levels do to the health of the plant communities in the lake," said Ernie Barnett, director of ecosystem projects for the Florida Department of Environmental Protection.

Water managers stressed that the greater volumes of releases will not result in additional flooding.

Water managers will meet once a week to determine how long the increased releases will be necessary, but Sylvester predicted they will occur for at least several weeks.