Immaculata College, a small two-year Catholic women's college in Northwest Washington will close permanently after its spring term, a victim, its officials said, of declining enrollments and rising costs.

The trustees' decision to close the college follows major changes over the past half decade in which its student body became almost half non-American, half non-Catholic, and half non-white.

However, overall enrollment slipped from a peak of 214 in 1970 to just 100 students this winter. Operating deficits averaged $30.000 annually for the past five years.

"We made every effort we could to keep the college going," said Sister Marie William, an education professor who is in charge of public information for the college. "But sometimes those efforts don't pay off . . . We kept teaching all the courses we said we would. We refused to take just everybody who wanted to come here. We kept our principles, but now we have to close. How long can you keep on absorbing a deficit?"

The trustees said the college facilities now will be turned over to Immaculata Preparatory School, a high school for girls that shares the same 8-acre campus at 4300 Nebraska Avenue NW, near Tenley Circle. The campus also has an elementary school for girls, called Immaculata-Dunblane, which is operated by the same religious order, the Sisters of Providence of Saint Mary-of-the-Woods, Ind.

Immaculata College, which has been accredited since 1937, originally grew out of the high school, which was founded in 1905.

Officials said both the elementary and high schools are thriving with a total enrollment this year of about 600.

According to the National Catholic Education Association, 24 Catholic colleges have closed throughout the country since 1970. Among them were Dunbarton College on Upton Street NW and St. Joseph College in Emmitsburg, Md. Both schools were small four-year colleges for women. Both closed in 1973.

Sister Marie said Immaculata managed to keep its defecit relatively low because its nine nuns receive only about $4,000 a year a piece to cover living expenses in a convent. The college also has 18 lay professors who teach part-time, she said, at relatively low salaries.

To try to bolster the college, Immaculata has added noncredit courses for adults, which attracted 200 students last year and have about 350 now.

In addition, Sister Marie said the college hired a management consultant who developed an extensive recruitment effort, including direct-mail advertisements to more than 20,000 high school seniors.

To attract foreign students, the college added special English language programs.

"We've received hundreds of inquiries," Sister Marie said, "and most of the students who do come here like it - but there is a big step between inquiries and actual enrollment, and that's the problem."

However, total enrollment in Catholic Colleges increased last year to almost 450,000 students after declining for the past half decade.

Since 1970, many private colleges, both Catholic and non-Catholic have encountered serious financial problems as inflation sent their costs and tuitions soaring, while low-tuition public colleges have expanded. Overall, about 100 private colleges have closed since 1970 out of a total of about 1,200.

Tuition at Immaculata this year is $1,950. With room, board, and compulsory fees, the cost for a dormitory student comes to $4,050.

By contrast, tuition at the publicly-supported University of the District of Columbia is $135 a year for D.C. residents. Tuition for state residents at the University of Maryland is $784.