Like most neighborhood and community pools, Lake Allatoona will be brimming and welcoming to the thousands who like to start the Memorial Day kickoff to summer with a splash.

Lake Lanier, still down 13 feet, will be more challenging to those who head to its shores to sun, swim and boat during the holiday.

Phil Skinner/AJC (ENLARGE)

Workers spread sand along the lake bottom that is exposed because of the drought on South Beach at Lake Lanier Islands Water Park in preparation for the Memorial Day holiday.

Phil Skinner/AJC (ENLARGE)

Oscar Orellana (left) and his brother Salvador help build a new tiki hut at Lake Lanier Islands Water Park while preparing to open up for Memorial Day, when the park expects a big crowd.

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But at both lakes, officials with the U.S. Army Corps of Engineers are expecting huge crowds. Just how big, they say, could depend, at least in part, on gas prices.

The roughly $4-a-gallon prices could have fun-lovers opting to head for the lakes, rather than more distant vacation spots. Or lake regulars could decide because of gas prices to build their holiday parties around their backyard grills.

About 350,000 people packed Lake Lanier last Memorial Day weekend, the corps' Mark Williams said. It was the unofficial start of a busy 2007 for Lanier, with a whopping 7,817,150 visitors.

But with lake levels down, Memorial Day boaters may find Lanier is "a different lake than they're used to," said E. Patrick Robbins, chief of legislative and public affairs for the corps' Mobile District.

Night boating will not be allowed, and boaters will be urged to take it slower to avoid being snagged by stumps or other low-water obstructions, Robbins said. They're also being encouraged to use GPS mapping systems or other detection devices, if possible, he said.

The corps is being even more emphatic that swimmers use life jackets or other flotation devices because of changes in the lake's topography, Robbins said.

"We don't want people hitting big drop-offs," Robbins said. "You just don't know."

The corps will have its full staff on patrols, with no tolerance for those who don't follow the edict against mixing alcohol and water, Robbins said.

All but one boat ramp is open at Allatoona, which is about one-third the size of Lanier and has been much faster to refill after the year's extreme drought conditions.

At Lanier, only about a dozen of the lake's 50 boat ramps are open this weekend, said Michael Lapino, the corps' chief park ranger at Lanier.

"There will be lots and lots of people at those ramps," he said.

The corps could be forced to close some of Lanier's boat ramps if their parking lots get so crowded that safety and access for emergency vehicles become concerns, Lapino said.

To help try to avoid that, the corps advises groups coming in multiple cars to use parking at some of the closed ramps, Robbins said.

Atlantan Claire Archer Croak had weekend plans that involved lounging in a small cove at Lake Allatoona.

"We have no boaters to avoid" and a long list of plans that include canoeing, grilling out and tubing near the dam, she said.

Canton resident Robert Forrester had plans to make it a weekend of swimming, picnicking and sailing at Lake Allatoona with members of his sailing club and his 8-year-old son, Zachary.

"I am planning on entering the sailboat race on Sunday with my son as my crew," he said last week. "We are considering camping out on the boat as well, if we can find a quiet place away from crowds."

After a record 595,476 visitors in April 2007, Lanier last month reported 494,493, or about 100,000 fewer, according to the corps' data.