Sixty-eight-year-old Catherine Wray does not appear in the city of Alexandria's new annual report. There are no pictures of her ample frame, her dog, Duke, or the weathered row houses of the block she has lived on for nearly half a century.

Nonetheless, according to the report, Catherine Wray, a retired custodial worker living sparingly on the fringes of Old Town, figures prominently in the city's future. She is a reflection of the new Alexandria.

The annual report by Alexandria City Manager Douglas Harmon shows that soaring land values and unprecedented rates of condominium conversion are squeezing out more and more of the city's middle- and lower-income families, making Alexandria increasingly a home for the affluent, the elderly and the poorest of the poor.

The transition is seen in the city's tax base, which jumped from $952 million to $3.2 billion in only 10 years. Old Town, the historic waterfront area of the city where an elegant row house can sell for $175,000, was responsible for at least a third of that increase.

No one knows that the character of Alexandria is changing better than Wray, who moved to Prince Street from the Shenandoah Valley town of Waynesboro in 1933.

"Oh, everything's changed, I guess," she says, seated on the sofa in the cramped two-bedroom house she shares with two roomers. "Most of my friends have moved away. I'd like to stay, but rent keeps going up, my Medicare card just got taken away, and my son has to help me with my gas bills. I love this old house. My son says I love it so much I'll be here when it falls down around me. But I don't know how long I'll be able to stay."

There are reasons to think it won't be long. One by one, the houses on her block of Prince Street are being renovated. Rents on the small houses are soaring, some increasing by as much as $300 a month. Wray used to spend summer evenings sitting on her blue lawn furniture talking with neighbors and friends. Sometimes they would share a box of doughnuts bought at the doughnut shop across the street. No more.

The doughnut shop is gone now. So are the neighbors, replaced by young singles and childless couples that, for the first time, the city report says, make up the majority of the city's households.

"Its an historic change," says Alexandria Mayor Charles Beatley. "There is lots of new construction, and a big change in the market."

The trend is not unique to Alexandria. In the District, soaring housing and rental costs during the past decade have resulted in an increasingly affluent city population and an exodus of middle-income families to Prince George's County. In Arlington, too, low- and middle-income dwellers are being squeezed out. But what is different about Arlington and Alexandria is that there is little sense of where the families are going.

"One of the whole puzzlements of the whole picture right now is where those people move and where they can move," explains George Grier of the Greater Washington Research Center. "We don't know what is going to happen to them down the pike . . . . There are some real human tragedies behind these signs that say you can buy your own condo for only $70,000."

Other signs of the times in Alexandria, according to the report:

Alexandria's black population, which rose from about 14 percent to 22 percent in the first half of the 1970s, has stabilized at that level. The white population fell from about 84 percent to 72 percent during the same period, and the city's ethnic population, largely Asian, increased from about 1 percent to6 percent.

In the last decade, at least 1,300 blacks were pushed from the historic Old Town district as property values there skyrocketed.

In 1979, about 6,000 low-income persons -- most of them black --were displaced when the Shirley-Duke Regina apartment complex in western Alexandria was closed. About half of those people left the city, with the other half probably moving to Del Ray and Arlandria, says city planner George Colyer. Although all of those renovated 2,100 units have been returned to the market, only 20 percent of them are subsidized, low-income housing.

Despite the displacement of low-income blacks, the black population in the western sections of the city has increased, particularly in the solid middle-class neighborhoods of Rosemont and Del Ray.

Enrollment in the city's schools is the lowest it has been in 10 years, a sign that families with children are leaving the city faster than they are being replaced. Smaller families and single residents mean that school enrollments will continue to decline.

For the last four years, the majority of students in the city school system have been black.

Since 1978, the number of people getting food stamps, for which only families below the poverty line qualify, has almost doubled, although per capita income in the city increased 14 percent from 1978 to 1979, compared to 10 percent for the entire Washington area.

The number of Alexandrians over 65 enrolled in Medicare has jumped from 10 percent to 14 percent in seven years, indicating that more elderly live in the city today.

The most striking change in Alexandria in the last decade, however, has been the dramatic but now familiar boom in condominium conversions, which continues to ravage the city's supply of low-income and moderate-rental housing. So far this year 1,900 of the 2,224 condominiums added to the market were conversions of some of the most inexpensive housing in the city. Though condominium sales fell from 1,500 in 1979 to 99 in 1980, no one expects the conversion rate to slow.

Condominiums aren't the only booming real estate market in Alexandria. In 1980 the city approved a million square feet of new office space, an amount unprecedented in Alexandria's history.

But the boom times have been a bust for many of the city's families.

"For a lower-income family to live in Alexandria, they have to have two to three people working," says Councilman James Moran. "And even then, they've almost got to be playing the system to make it. Without cheating to get food stamps or something like that, it's almost impossible."

Jessie Cowans, a stout, 60-year-old woman who has lived in Del Ray since 1966, says her street is fairly stable, but that homes there change hands more frequently than they used to. And these days, the homes usually are bought by young singles like Lou Delorme, a landscape architect with the National Park Service, who lives a few blocks away.

He is renovating the five-bedroom house he bought for about $70,000 two years ago. He says he likes the neighborhood, but that he would not have moved to Alexandria if he had children.

"There's a basic disappointment with the school system here," he says. "The kids are more rowdy than in other places, and they tend to be from lower-income families."

This is precisely the attitude that distresses Moran. Singles and childless couples, he says, are more interested in day-to-day needs, such as trash collection and police protection, than in schools.

"These changes," Moran says sadly, "make Alexandria a much more sterile place."