The Inter-American Development Bank made more loans to Latin American development projects last year than in any other year since its creation in 1959, according to its 1981 annual report.

The bank approved loans totaling $2.49 billion, which was 8 percent more than the amount loaned in 1980. At the end of the year, the institution's cumulative lending had risen to $20 billion, which is helping finance social and economic projects worth about $80 billion.

Lending for energy projects almost doubled in comparison with 1980, as the bank's Latin American member countries continued to develop renewable sources of energy, particularly hydroelectricity. Loans for agricultural projects increased moderately.

The member countries in South America received about two-thirds of the total monies loaned, with Brazil, Argentina and Chile receiving the largest share.

The report said that 76 projects for which the bank had lent a total of $1.35 billion were completed during 1981.

The report also showed that bank's borrowings, disbursements, repayments and earnings reached new highs in 1981.

Recent agreements by international lending and financial institutions:

Inter-American Development Bank

* The bank announced that it has concluded a syndicated loan in Japan for 15 billion yen, which is equivalent to approximately $63.3 million. The funds are being provided by a syndicate of long-term credit banks, trust banks and life insurance companies led by the Industrial Bank of Japan, the Long Term Credit Bank, the Bank of Tokyo, the Nippon Credit Bank, the Sumitomo Trust and Banking Co. and the Nippon Life Insurance Co. The proceeds of the placement will be incorporated into the bank's interregional capital resources and will be used to make loans for economic development projects in Latin America. With this loan, the bank's cumulative borrowings in Japan, at the current exchange rate, will amount to the equivalent of about $667.5 million.

* Approval of a $316,000 grant for studies on salt deposits in Bolivia and methods to use in transporting and marketing them. The program of study will consist of four projects: A study to determine the possibility of mining the potassium resources of Bolivia's salt deposits on an industrial scale, to meet the needs of the Andean countries for potassium-based fertilizer; a study of how to increase the use of fertilizers in the Andean countries; a study of highway transportation problems at border crossings, and a study to assess the market outside the region.

* A technical cooperation grant of $640,000 to Colombia to finance a study to examine ways to improve the ecological condition of the waterways in and around the city of Cartagena. Rapid growth and industrial development since 1950 have increased pollution of the Cartagena waterways, producing a steady deterioration of sanitary conditions. Waste water and trash are dumped into the channels, reducing and, in some cases, liquidating the fish and shellfish population. This deterioration is most acutely felt by low-income groups living on the waterways.

International Monetary Fund

* A purchase equivalent of 106.9 million special drawing rights by the government of Zaire under the compensatory financing facility because of an estimated 20 percent decrease in exports experienced by that country in 1981. The bulk of the decrease can be attributed to weak demand for the country's mineral exports, diamonds and coffee and to depressed world market conditions.

Export-Import Bank

* Austrian Airlines will purchase three DC-9-80 jet aircraft and related spare parts from the McDonnell Douglas Corp. for $71.6 million. The company estimates that the sale will create more than 2,600 man-years of employment at its facilities in Long Beach, Calif., and at its other plants throughout the United States. The purchaser will make a cash payment of $43 million and will obtain a $28.6 million loan from the Export-Import Bank, at an 8 percent interest rate.

* The bank has approved a $7.8 million credit to support a $12 million contract for Ebasco Services Inc. of New York to provide engineering services for two nuclear units of the Korea Electric Power Corp. Ebasco will advise the utility in matters relating to project and construction management, schedule and cost control, quality assurance, reviews of mechanical, electrical and control design, licensing and operation. Nuclear equipment will be supplied by a French firm. Additional financing for the project will consist of $2.4 million from private sources and a $1.8 million cash payment.