The D.C. City Council, which had hoped to cut $26 million from Mayor Walter E. Washington's proposed 1979 budget, settled for cutting only about half that amount yesterday, and gave preliminary approval to a $1.3 billion city operating budget for the fiscal year beginning next October.

Climaxing more than five weeks of budget deliberations, the Council approved a spending level that was $14.8 million (or 1.1 per cent) less than the amount proposed by the mayor on Sept. 12.

Despite frequent Council criticism of the Washington administration's delivery of city services, yesterday's preliminary Council action was devoid of any far-reaching program or personnel changes that would significantly affect the way the city is run.

The Council tentatively raised by less than 100 the number of civil servants the city can employ, did not increased the number of employees or operating funds in allegedly understaffed and backlogged city agencies, and refused - without debate - to approve the full $255.8 million in operating funds requested by the school board.

In addition, in an action that will have to be resolved later, the Council did not include in the budget some $34 million in projected costs for pay raises to be granted to the city's 35,000 regular employees in 1978 and 1979.

Half that money is expected to come from an increased federal payment that the White House has recommended but some congressional leaders oppose. The city is not yet sure how it will get the remainder.

The absence of the pay raise funds plus the questionable nature of some of the reductions made by the Council made it uncertain yesterday how real the proposed $14 million reduction was.

The city's budget is required by law to be balanced, and a financial plan approved by the Council yesterday to support the budget provided that balance. But that financial plan is nearly identical to the one submitted by the mayor, and the Council's own finance and revenue committee thinks the mayor's plan contains between $31.7 million and $66 million in "questionable revenues."

A spokesman for Council Chairman Sterling Tucker said after yesterday's Council session that those differences cannot be reconciled until the 1973 budget is given final approval by Congress. Resolving the differences could necessitate further cuts in programs or increase in taxes or user fees.

The 1978 budget is still languishing before a House-Senate conference committee, which is deadlocked in part over whether to appropriate $27 million included in the budget that is intended to finance start-up costs for a proposed $110 million convention center in downtown Washington.

The Council will take one more vote on the 1979 budget - in two weeks - before sending it to Mayor Wahington, who is expected to veto some portions of it. After anticipated Council attempts to override those vetoes, the spending package will be sent to the White House early next year and later forward to Congress.

Tucker and other Council members hope to use the $14.8 million they cut from the mayor's prposed 1979 budget for some form of property tax relief, but for the time being the proposed savings have merely been set aside as a "reserve" with specified use.

The 1979 budget proposed by the mayor was [WORD ILLEGIBLE] per cent greater than the city's proposed budget for 1978 - with few increases in programs and services - indeed, with some reductions.

The mayor proposed no increase in the city's tax rates or user fees, but his 1979 budget did assume an average 23 per cent increase in the assessed value of homes and businesses in the city over the next two years - increases that are likely to boost the amount of property taxes paid to the city.

At the same time, the mayor advocated as a means of balancing the 1979 budget an aggressive program of parking law enforcement that would add $20 million to the city's general fund by imposing higher fees for parking law violations and increasing the likelihood that violators would be caught.

Many of the program increases recommended by the mayor were in areas where the city has been ordered by various courts to improve services.

Despite the relatively small overall increase in the major's budget, the Council targeted $26.3 million in reductions and urged its respective committees to make cuts reflecting such a reduction. The document approved yesterday was largely a compilation of those individual committee actions.

The biggest reductions came in four city agencies - the departments of human resources (the city's largest agency), transportation, environmental services) and corrections.

DHR's proposed $299.5 million budget was reduced by $4.6 million. Among other items, the Council cut $600,000 that DHR officials had predicted would be necessary to handle anticipated caseload increases for the city's welfare programs.

The Council also trimmed nearly $1 million that was to be used to improve educational opportunities for mentally handicapped children, improvements ordered by a federal court. Some Council members believe the court order may not require these particular programs, and if so, they believe the programs could be put in effect for less money than that requested by DHR.

In the Department of Corrections, much of the $3 million reduction in the proposed $53.4 million budget came as a result of a $2 million cut in the projected payments to the federal government for keping D.C. prisoners in federal facilities. More than $300,000 that had been scheduled for pay raises was eliminated on grounds that the department could make further budget reductions and pay the increases without additional funds.

More than $1 million was taken from the planned $6 million operating costs projected for the parking crackdown, and an additional $300,000 was saved by rejecting plans to buy all but a few of the 57 cars, ambulances and school minibuses requested by the city's transportation department.

The Council also decided to reduce by one-third the staff of the mayor's Office of Municipal Audit and Inspection, and urged a similar staff reduction in the city office that oversees efficiency in government operations. The eight-member staff of the city's public affairs department was cut in half and transferred to the mayor's office.

The Council approved $1 million to finance a program that will help low- and moderate-income persons to purchase homes, and $650,000 to continue a program to place voting machines in all city precincts by 1980. It also approved $238.9 million in operating funds for the city school board.

The Council also approved a $130.2 million capital improvements budget, $386,000 more than the amount recommended by the mayor. The increase was due entirely to inclusion of money to support Metrorail construction costs.

Major items in the program are $28 million to build a new water treatment facility at the McMillan Reservoir, $49 million for the planned convention center and $15 million for renovation of Eastern High School and the Duke Ellington School for Performing Arts.