Drug indictments have more than tripled in D.C. Superior Court this year as police and prosecutors battle an upsurge in illegal drug activity, local officials told a Senate subcommittee yesterday.

During the first seven months of 1984, indictments involving illegal drugs reached 2,121 compared to 681 in the same period last year, said Judge Fred Ugast, head of the court's criminal division. Drug charges account for 41.5 percent of all felony cases prosecuted in the court this year, Ugast said, compared to 19.2 percent a year ago.

"Drug abuse has reached epidemic proportions within the District of Columbia," said Inspector Wilfred K. Coligan, head of the police department's morals division. "All nine active drug treatment clinics in our city are filled to their maximum level.. . . Street marketplaces for drugs are cropping up at more and more locations."

Sen. Arlen Specter (R-Pa.), chairman of the Senate D.C. appropriations subcommittee who convened yesterday's hearing, said the proliferation of drugs in the city is "part of a larger drug problem that this country has not coped with very well."

Specter called for an increase in law enforcement efforts, drug treatment and antidrug education programs, although he said it is unlikely that more funds can be added to the District's budget for the coming fiscal year.

The current drug upsurge follows almost a decade of steady or declining drug use, officials said, after the last sharp rise that occurred around 1970.

U.S. Attorney Joseph diGenova said this year's tripling in felony drug prosecutions stems partly from stepped-up activity by D.C. police and the federal Drug Enforcement Administration along with a policy of "vigorous enforcement" by his office. But he declared: "I think the main reason is that there are just more drugs out on the street."

DiGenova said the conviction rate in drug cases has remained steady and high.

Felony indictments involving PCP, a hallucinogen readily manufactured in illegal laboratories, have increased from 18 in 1982, diGenova said, to 187 last year and 370 in the first half of 1984.

He said the felony cases are brought for sale or manufacture of a drug or for possession of substantial quantities with intent to distribute.

Coligan said cocaine arrests have more than doubled over the past year. He said even though arrests on heroin charges have decreased slightly, the street price of the drug has dropped sharply while its average purity has reached unprecedented levels, indicating "a readily available supply."

By the end of August, heroin overdose deaths in the city had reached 78 for the year, Coligan said, exceeding the 69 such deaths in 1983.