Columbia has begun what appears to be the first serious attempt to crack down on criminal activity, from drug-running to counterfeiting, that has a direct impact on the United States.

Since his inauguration last August, President Julio Cesar Turbay Ayala has placed the Guajira Peninsula, which juts into the Caribbean and has long served as a major shipment point for marijuana and cocaine, under the jurisdiction of Columbia's armed forces. American officials say the move has, for the first time, begun to disrupt the flow of narcotics to the United States.

The Turbav government also has allowed U.S. Secret Service agents into Colombia for the first time as part of an effort by the F-2, this country's version of the F.B.I., to stop counterfeiting rings that have operated freely here until now.

A raid last week, the third in recent months, netted more than $4 million in bogus dollar and peso notes as well as false passports and travelers checks.

The Treasury Department estimates that about 90 percent of all the counterfeit dollars manufactured abroad that successfully reach the United States come from Columbia, which over the past two years has probably become the world's leading producer of bogus currency, according to American officials here.

It is drugs, however, that remain Colombia's most important illicit export - worth an estimated $500 million to $1 billion a year. It is estimated that 85,000 acres, mostly in the Guajira, produce about 35,000 tons of marijuana a year.

The General Accounting Office has said that Colombia is by far the most important source for both cocaine and marijuana entering the United States.

While Turbay's effort thus far have not even come close to stopping the vast drug trade that has flourished in Colombia since the early 1970s, the military campaign in the Guajira has achieved substantial results, according to U.S. officials.

Approximately 3,500 tons of marijuana, worth an estimated$70 million to Colombian drug runners and about $280 million when finally sold in the United States, have been seized. About 1,000 Colombians and Americans have been arrested in the Guajira, and 65 to 70 airplanes and an equal number of ships engaged in drug smuggling operations have been captured.

The Guajira peninsula is a rugged, mountainous region populated largely by Indians clinging to an ancient pre-Columbian culture. The valleys and villages are home to recent migrants and peasants who left southern Colombia to escape the civil strife of 1949-58. Such services as sewage, health care and running water are rare, and transportation outside the towns is virtually impossible.

Col. Miguel Maza Marquez, commander of the F-2, said last week that his efforts to stop cocaine traffic in Colombia have resulted in the destruction of 119 cocaine laboratories, the seizure of 2,639 kilos of cocaine and the destruction of 19,547 kilos of coca paste headed for laboratories to be turned into granules of cocaine.

In all, Maza said the F-2 has arrested 1,069 Colombians and 151 foreigners in connection with the cocaine raids.

Because Colombian law enforcement officials have been so corrupted by drug money, however, there can be no guarantee that all or even most of the marijuana and cocaine seized has been destroyed. Nor can there be any guarantee that those arrested in the drug raids have been kept in jail and tried - because it is still relatively easy to bribe authorities here to secure freedom from prosecution, according to diplomatic sources.

Nonetheless.American officials say that Turbay, who was stung by charges in the United States that members of his family are engaged in the drug trade, has demonstrated since he assumed office that he is determined to cooperated with the United States in trying to stop the drug trafficking

This a major change in public attitude from Turbay's predecessor, former president Alfonso Lopez Michelson, who took the position that "we are not corrupting the Americans, the Americans are corrupting us." Lopez' attitude was that the United States should stop illegal drugs from entering its own territory and not expect Colombia to use its resources to stop marijuana and cocaine from leaving.

The Carter administration has offered Turbay $2.4 million this fiscal year to aid in the drugs battle. The money is being used to provide rations for 6,500 soldiers now involved in the operation under the command of Gen. Jose Villareal.

In addition, the U.S. money is used for fuel for Colombian helicopters and destroyers that patrol the Guajira Peninsula and radio communications equipment to coordinate raids. The United States is also installing two radar units in the area to monitor airplanes that regularly land at clandestine airstrips, pick up their cargoes of "Santa Marta gold" and then return to remote landing strips in the United States.

The Colombian government has said it reserves the right to shoot down any plane entering its airspace illegally. The government here has also announced a three-month study to determine whether it should begin spraying marijuana fields with paraquat, a poisonous herbicide used successfully in Mexico.

Despite the military takeover of the Guajira, the area is still known as a no-man's-land where local "mafiosos," as those involved in the drug trade are called have great influence - either as a result of bribery or the guns they wield.

During the first three months of this year, there were 240 murders in Sanata Marta alone, the captial of the province which encompasses the Guajira Peninsula. Most of the murders are thought to be drug related.

Desptie his public statements, there are those in the Guajira who believe Turbay's campaign against drug traffickers is aimed principally at the peasants who grow marijuana and at minor drug dealers who buy and sell relatively small quantities.

Few of the really big-time "captains" of the drug-running trade have been arrested, according to several sources here, although their identities are well known.

Throughout the Guajira, the slogan "Turbay es la Mafia" is plainly visible on countless walls. But there are other well-informed Colombians - such as journalist Daniel Samper Pizano, whose column in El Tiempo, Bogota's most influential newspaper, is usually highly critical of Turbay - who believe the new president is in no way connected with the drug trade and believe he is serious when he says he is determined to end it.

Turbay and the "traditional families" that have long dominated Colombian economic and political life seem to have reached agreement that the "mafiosos" and the money they command have not only given Colombia a very bad international image but, more importantly, threaten the hold the traditional oligarchy has long enjoyed here.

Stories abound of rich "mafiosos" buying apartments and real estate in Bogota as well as hotels, banks and soccer teams throughout the country. They apparently also have begun to strongly influence politicians. The traditional families are said to be worried that the drug runners, with their vast resources, may one day control the country. CAPTION: Map, Marijuana and cocaine are shipped to the U.S. from these Colombian ports. By Hal Hoover - The Washington Post