Gasoline pump prices, after falling sharply and steadily for more than a year, have hit bottom and are now on their way back up, rising an average of 4.4 cents a gallon at area stations over the past three weeks, according to a Washington Post survey.

More rises are expected as motorists hit the road for summer vacations, pushing up demand for supplies that are expected to be adequate but no longer excessive.

"As long as there was a glut of gasoline and OPEC appeared unable to control production, the price went down," said Vic Rasheed, executive director of the Service Station Dealers of America. But that downward trend now has been reversed, Rasheed said.

He predicted that prices--which averaged $1.30.4 a gallon for all grades of gasoline at 98 area self-service and full-service stations surveyed Friday by The Post--probably will spiral upward from their current levels until they are as high as or higher than the 1981 peak that preceded the gasoline glut.

For Washington-area motorists, that would mean a return to gasoline prices averaging $1.45.4 a gallon--the peak recorded on April 3, 1981, by the American Automobile Association in a survey of Washington-area full- and self-service stations for all grades of gasoline.

In addition to the price increases triggered by supply changes, motorists can look for two other major price changes at the gas pump. The first is the scheduled increase in local gasoline taxes--Maryland's gas tax goes up 2 cents a gallon starting June 1 and Northern Virginia's new 3 percent gas tax will begin July 1, raising pump prices by 3 to 4 cents a gallon.

The second change is the new and expanding practice of charging credit card users more than cash customers. Several major companies are expected to follow Texaco's lead and require credit customers to pay extra this summer.

One Gulf station in Northwest Washington already has begun to charge 17 to 27 cents a gallon more for bank card credit sales. The station's self-service pumps dispense regular unleaded gasoline for $1.15.9 a gallon to customers paying cash or using Gulf cards, but the price is $1.42.9 a gallon for those paying with bank credit cards such as Visa. Regular leaded and premium unleaded gasoline are 17 cents and 19 cents a gallon extra for bank card buyers.

In the past week area stations have been scrambling to adjust their pump prices to reflect the higher wholesale costs they pay to gasoline producers. In the past month, Exxon has raised its wholesale price 5 cents a gallon; Amoco, 4.3 cents a gallon; and Shell, 4 cents a gallon.

Companies raised their prices for "all kinds of reasons," said Jim Fair, an Amoco representative. One reason is the higher price for crude supplies that has been caused by production cutbacks by Saudi Arabia and other oil-producing countries, Fair said. At the same time, he said, demand for gasoline has soared as jobbers and other middlemen rush to replace their stocks and inventories before prices go any higher.

"It's been a little like a run on the bank," Fair said.

Price increases at Washington-area service stations vary widely, depending on the brand and the neighborhood competition. For one Silver Spring BP station, which had the lowest price found in the Post survey, regular leaded gasoline climbed 2 cents a gallon, from $1.02.9 to $1.04.9. But at the same time, a Gulf station in Northwest Washington jumped its gasoline 12 cents a gallon, from $1.07.9 to $1.19.9 a gallon. Increases at most other stations, however, ranged from 3 to 6 cents a gallon.

An examination of price changes at 15 of the 98 stations surveyed showed that the prices hit bottom in late April and remained there for two to three weeks before starting to increase. Since hitting that bottom, the 15 stations have increased their prices an average of 4.5 cents a gallon for self-service leaded regular, which now is $1.10.7 a gallon compared with $1.06.2 before. Unleaded regular self-service gasoline now is $1.15.4, compared with $1.11.2 before--an increase of 4.2 cents a gallon.

The Post survey found significant variations in the average prices for the three jurisdictions comprising the Washington area. Maryland's average self-service prices for regular gasoline were 6 to 7 cents a gallon lower than the District's and 3 to 4 cents a gallon lower than Virginia's.

But Virginia had the lowest average price for full-service regular with Maryland averaging 3 to 4 cents a gallon more than Virginia, and with D.C. averaging about 6 cents more than Virginia.

There is some good news for motorists, however. Industry officials don't believe there will be lines at the gas pumps this summer.