The annual lifeguard shortage is beginning to surface at Washington area swimming pools.

One Montgomery County pool has been closed and more may be shut down in the next few weeks, officials said last week, as many of the students and teachers who work as pool managers and lifeguards return to school. Traditionally, most area pools have stayed open through Labor Day.

In Prince George's County, four of the six outdoor public pools operated by the county close Aug. 28 to 30, when public schools begin, and reopen during the Labor Day weekend, officials said. Fairfax County officials said they have experienced some staffing problems but will be able to maintain regular operations this month. The District of Columbia was the only one of the local jurisdictions surveyed last week that reported an ample supply of lifeguards.

"The shortage of lifeguards is the same every year; we rely on students for a large part of our staff, and when they go back to school, we don't have the staff to stay open," said John Knepley, aquatic supervisor for the Maryland- National Capital Park and Planning Commission for Prince George's County.

At the same time, Knepley said, pool business drops because students who have been coming to swim are back in school.

In Montgomery County, officials have closed the Fenwick Pool, at 1400 Fenwick La., Silver Spring, because of a lack of adequate staff, said Barbara Modine, aquatic coordinator for Montgomery County. Another consideration, she said, was that the Fenwick pool is a small pool used by only about a dozen people a day during August, when many local residents are away on vacation.

Modine said that Montgomery County's two indoor pools are closed for cleaning but will be reopened in a few weeks. Staff members not involved in the cleanup have been reassigned to outdoor pools where they are needed to replace workers who have gone back to school, she said.

"We won't open any pool without adequate staff, even if there are 1,000 people waiting to get in," Modine said, "because our main concern is a safe operation."

Wayne Cottrill, superintendent of park facilities for Fairfax County, said his area has been affected by the lifeguard shortage, but not as severely as in Montgomery County. "We have fewer outdoor pools, and therefore fewer problems," Cottrill said. Fairfax County has two public outdoor pools and four indoor pools, compared with Montgomery's nine outdoor pools and two indoor pools.

"Every year we experience problems with kids going back to school . . . but never enough that we have to shorten our hours or close," Cottrill said.

In the District, the Department of Recreation plans to maintain the usual hours at its 33 outdoor pools and eight indoor pools, said Carolyn Mills, public affairs specialist for the department.

"We advertise for lifeguards," Mills said, "and we get them."

When pool operators have to "play musical lifeguard" to ensure adequate staffing during August, those who continue to work can benefit.

"A lot of the older people lifeguards leave and the rest of us work a lot of overtime as a result," said Bryan Emmerson, 17, a lifeguard at the Upton Hill Regional Park Pool in Arlington.

Emmerson said he expects to work 24 hours of overtime during the next two weeks as a result of the lifeguard shortage. "I'm glad to get the money . . . . I will need it for when I go away to school," he said.