Government, business and labor leaders say yesterday's groundbreaking for Washington's first convention center as the beginning of a downtown renaissance, but for Ida M. Picking, 83, it was the end of a neighborhood she loved.

"My heat will always be here," said the white-haired woman, dressed in a green floral dress and carrying a plastic shopping bag after the ceremonies for the $98.7 million facility at the corner of 10th and H Streets NW.

She and her husband had once lived on one of the several blocks that the city has leveled between Ninth and 11th Streets and H Street and New York Avenue to make way for the massive, two-story center that will accommodate up to 26,000 conventioneers.

While Picking looked over the empty 9.7 acres and remembered a conveniently located neighborhood that once was hers, most of the 250 people who gathered under sunny skies and warm temperatures presumably were envisioning the centerpiece in the redevelopment of the neglected portions of Washington's downtown.

Mayor Marion Barry and business and labor leaders have said that the long-awaited and much-debated center would generate 5,000 to 6,000 new hotle rooms, 4,000 new jobs and at least $45 million in new revenues for the city's depleted coffers.

"We need a convention center," Barry told the crowd against a backdrop of steel I-beams and construction equipment. "We ought to be able to capture the economic benefits" of the thousands of tourists who visit Washington annually, he said.

"This center will provide additional jobs for our people," he continued. "With unemployment running 40 to 50 percent in some of our neighborhoods and young people feeling hopelessness," he urged convention center builders to hire large numbers of minority group members.

"A healthier downtown and District of Columbia that's what we're launching here today," said Edwin K.Hoffman, chairman of the board of Woodward & Lothrop department stores.

Hoffman said construction of the convention center represented the fourth and final essential ingredient for the revitalization of downtown. The other three were Metro, the city's subway system, downtown urban renewal and the redevelopment of Pennsylvania Avenue, which is under way a few blocks south.

Yesterday's groundbreaking ceremony culminated more than 10 years of false starts, wrangling with Conress for funds and legal battles with citizens to get the center under way.

City officials and business leaders have said they hope the convention center will draw office and hotel development back to the city's traditional downtown east of 15th Street, which has languished since the late 1960s.

For the last 15 years developers have preferred to build west of 15th Street, and as a result a phalanx of high-rise office buildings now line K Street NW and the surrounding blocks west to 23rd Street, representing almost $1 billion in new building.

Government, business and labor leaders predicted success for the center, which some citizens groups and congressional leaders have doubted, although its construction begins at the start of a recession.

Hotel occupancy in the city has also declined by 9.5 percent for the first three months of this year, compared to the same period last year.

James O. Gibson, the city's planning director, said the recession might have a mixed impact on the convention center.

With more national professional associatons locating their headquarters in Washington, Gibson said to save money these organizatons might might bring their conventions here instead of moving an office staff to another city for a few weeks.

In addition, more lobbyists will come to the District to ask for governmental aid or protection, Gibson said.

The city forecasts that the center will bring 320,000 more conventioneers to Washington in addition to the 750,000 that already come here annually. City leaders said they believe more conventions want to come to the District but are prevented by the lack of large convention facilities, which the center would provide.

On the other hand, Gibson said the recession might slow down construction of several new hotels and office building that the city expects the center to foster while developers watch interest rates.

City business and labor leaders are more optimistic and predict that the recession will end well before the center's scheduled opening in mid-1982.

Leonard Hickman, head of the Hotel Association, is one of these, but he pointed out that the airline industry predicts a decline in passengers that will last for the next 12 to 18 months.

That probably means a fall off in Washington visitors, Hickman said

Citizens who oppose the convention center claim it will cost city taxpayers millions to operate.

While Barry and others painted bright pictures of the future, Ida Picking recalled a neighborhood of nearby stores, churches and activity.

"I loved it because it was downtown," she said yesterday. But she and her husband moved away soon after the 1968 riots "because the burning scared us." They now live in an apartment near North Capitol Street.