The District government's 1980 fiscal year will pass into history today unmourned but not unremembered. The city has survived it, but only -- with apologies to Tennessee Ernie Ford -- another year older and deeper in debt.

Much deeper, in fact. Estimates of the amount by which the city overspent its revenue begin at $100 million and go up to twice that, although the true figure will not be known for months. Despite the tone of austerity emanating from the District Building, the city's total indebtedness is now estimated to be $409 million, not counting at least $2 billion in pension liabilities for which there is no source of funds.

It was a year in which Mayor Marion Barry laid off workers, trimmed services to his constituents, raised taxes and still came out deeper in the hole than anyone since the profligacy of Alexander (Boss) Shepherd forced Congress to revoke home rule in the 1870s.

The city is not broke in the sense that it was under Shepherd, when there was no money to pay employes. Aides to Barry say there is enough cash in the till not only to meet all payrolls but even to repay $60 million borrowed from the U.S. Treasury when bank balances were low earlier in the year. That money may have to be borrowed right back, perhaps as early as November, but at least the 1981 fiscal year will start with that part of the ledger clean.

The end of a fiscal year is a bookkeeping exercise that does not affect the city's gloomy overall fiscal outlook. But by slipping smoothly into 1981 with all payrolls met and no crisis imminent, Barry may be able to shoo away the specter of impending collapse that has hovered over the District Building since he announced last spring that the 1980 deficit might exceed $170 million.

The city remains solvent, at least temporarily, because while its bills exceed its revenue, they do not all fall due at once, and when they do come in, they can be paid with next year's tax revenues.

But such fiscal sleight-of-hand cannot go on much longer, city officials say. Some time in 1981, according to city administrator Elijah Rogers, the city will need the $215 million Barry has proposed to borrow from the Federal Financing Bank to stay afloat, but approval for that funding is far from certain.

Barry has been the first to admit that he does not have solutions to the city's myriad fiscal troubles not the power to implement all the proposals he has made. But he and his administration argue that the year was actually one of difficult and important achievements: recognition of a politically sensitive problem that had long been ignored or disguised, an accurate assessment of it scope, development of a long-range plan to deal with it, and the beginning of the political and psychological adjustment to austerity, both among city officials and among the District's residents.

Accountants have estimated the city's total cumulative deficit at the end of 1980 as $409 million. That is $284 million from past years, and an estimated $125 million this year, though the actual 1980 figure won't be known until an independent audit is submitted in February. Barry's strategy, evolved under heavy financial and media pressure during the year, is to accept that burden as the consequence of past mistakes it is too late to correct and to prevent it from growing by keeping all future budgets balanced in fact as well as in theory.

He can only do that, in a time of inexorably rising costs, by service and staff cuts that strike at the very kinds of people he claimed to represent when he was a street activist and youth organizer in the 1960s. Firing school teachers, laying off security guards at public housing projects, limiting increases in welfare benefits and shortening the season at public swimming pools -- actions he describes as "painful" and "agonizing" -- have become inevitable.

The end of the 1980 fiscal year leaves several key issues unresolved that could interfere with the mayor's complex plans to balance future budgets and begin to pay off the deficit while maintaining basic services and holding the line on taxes.

Congress has not yet approved the city's proposed budget for the year beginning tomorrow, and is not expected to act on it until after the November elections. That leaves unclear exactly how much the city is authorized to spend in 1981 and for what; it is still possible that Congress will instruct the city to hire more than 200 additional police officers to bring the force back up to the 3,880 officers demanded by the House Appropriations Committee.

Unions representing city workers have demanded the same 9.1 percent salary increases that their federal counterparts are to receive beginning this week. Barry is offering only 5 percent.

City officials expect the unions to go to court and if the unions win, Barry would have to find another $28 million somewhere or lay off enough workers to save that amount and give it to the workers who remain on the payroll.

The biggest problem may turn out to be the proposed $215 million loan. According to Barry and Rogers, the city can continue to cover its paychecks and send money to suppliers for work done in 1980 by using tax revenues that come in during 1981, but some time during the year that $215 million will be needed. Approval by Congress and the City Council would be needed, however, and neither is by any means assured.