Woodward and Lothrop this week is reopening the basement of its downtown store after a $150,000 remodeling.

The bottom level budget store, which is being eliminated from all Woodies units, has been replaced by a new collection of shops and restaurants aimed at younger customers.

The changes are an effect to capitalize on the thousands of Metro riders who flood through the lower level of the store daily en route from the subway station, said William D. McDonald, Jr., vice president for marketing.

It is also the first step in a planned $6 million, 5-year complete renovation of the store.

McDonald said the subway is bringing new business to the store. "The Metro system is proving itself as far as downtown Washington business is concerned," he said.

He said traffic through the lower level of the Woodward and Lothrop store is now heavier than during last year's Christmas season.

Woodies basement store was closed Aug. 1 for three-month makeover that will be completed next week. Although some potted plants and trimmings are missing, the 44,000 square-foot main basement level reopened Monday.

By the end of the week, the lower subway level will be back in business as a 4,000 square-foot, "swing merchandising" shop. Devoted to Christmas goods for the next two months, the subway level then will be redone at frequent intervals to catch the eye of regular subway users.

With the closing of the budget shop, the big store has integrated Wrangler jeans, Health-Pex children's clothes and other basement brands into regular departments.

"We feel the budget customer, attitudinally and in demographics is becoming more of a moderate customer," McDonald said during tour of the new departments.

This sort of "trading up" by budget customers plus rising prices from traditional budget shop suppliers has led many department stores away from "bargain basements." Higher volume, higher profit departments are going into the underutilized lower levels in stores like Macy's in New York, which has converted its basement into an "Underground" of bo* utiques.

The new Woodies bsement shops are Junior World, for young women; The Body Shop, the young men's equivalent of a junior shop; Shoe Bag for teens and young women; and Genesis, a young teens' shop.

Aimed at "12 and 13-year-olds who want to dress like they were 16 or 17" Genesis is "an extremely successful, building business," McDonald said. It is being promoted through so-called bubble-gum rock radio stations, like WPGC, KYS and WWDC.

All the new shops are substantial expansions from their old locations on upper floors, McDonald said. He predicted the new departments would generate three times the business from about 50 per cent more selling space.

New display techniques have been used, directed by Pierre Lalire, a newly-hired vice president in charge of visual merchandising.

Not yet completed is a fast food complex called EatCetera, which includes SubSide, a pizza and hero sandwich operation; RollCall, featuring sandwiches, and SweetThings for drinks and deserts. The basement cafeteria will become CounterCulture, a health-food oriented line with salads, juices, and the like.

A fancier restaurant - reportedly a branch of a big name in the food business - is planned for the second floor of the store, which is next in line to be remodeled.

McDonald said the second level will be transformed into a men's floor, substantially enlarging the present male apparel departments.

The remodeling is scheduled to continue in phases through 1980, the 100th anniversary on Woodward and Lothrop.

Additions to the 450,000 square-foot store are being considered, if the downtown business growth spurred by Metro continues. The proposed convention center is a crucial element in that equation, the company spokesman said.