February 12, 1981

ONCE it was taken for granted. Water was plentiful and it came out of our taps in seemingly never-ending amounts. No longer. Today, in short supply and with the real possibility of reservoirs supplying the area drying up, water has come to be regarded as something semiprecious, a resource to be carefully husbanded, the subject of serious restrictions and family rules regarding its consumption and conservation. There is among us, in short, a new water ethic. These days, despite yesterday's rain, there are only 29 days of water left for Greenwich, Conn., and 40 days remaining for most of northern New Jersey, and the word is ''Conserve,'' the dictum, ''You'd better,'' and the ways both basic and creative. But in New York City, which has less than four months of water left, and where Mayor Koch has (via radio) deputized city youngsters to urge their parents to conserve, there does not yet seem to be the sense of urgency that there is in the suburbs.

An obituary of H.I. Feldman in The Times on Jan. 27 incorrectly identified the architect of the Schwab House at 73d Street and Riverside Drive. The architect was the late Sylvan Bien.

In a statement that seemed aimed in part at spurring competition among aircraft manufacturers, Delta Air Lines said yesterday that it planned to spend $7 billion to acquire about 140 new fuel-efficient airliners over a 15-year period, starting in 1986. Some industry analysts said the unusually detailed disclosure of long-range plans served Delta's interests by underscoring a public image of financial strength at a time when less profitable airlines have had to delay equipment-purchasing decisions. Delta's $7 billion in purchases would be in addition to the $3 billion worth of Boeing 757's that the airline decided to order last year, a Delta official said. From Delta headquarters in Atlanta, William Berry, chief spokesman for the airline, said the company hoped that the Boeing Company, the McDonnell Douglas Corporation and Airbus - a European manufacturing consortium - would compete for $5 billion worth of the new orders, which are to be for a total of about 100 short-range, 150-passenger aircraft of a design that is still unselected. He said Delta had already been in touch with all three concerns about the planes. The remaining $2 billion is to go for roughly 40 more Boeing 757's.

IT used to be easy. Artists painted pictures or made sculptures - and their works were there to be looked at but not touched. For a chair to sit in, a bed to lie down on or a lamp to read by, one went to the department store or the designer showroom. The making of functional furniture belonged to the cabinetmaker, the industrial designer, even the architect, but not the artist. ''The barriers between art and furniture keep on dissolving,'' said Marian Goodman of Multiples Gallery, 38 East 57th Street, one of the New York galleries where furniture designed and made by artists is shown. ''The significant thing now is the breaking down of the barrier between art and crafts,'' said Frank Kolbert, a dealer. And although a small group of artists ranging from Lucas Samaras to Robert Wilson, the playwright, have made furniture for decades, a growing number of artists are using functional works to express themselves.

In 1919, a mining engineer named Herbert Everest was caught in a mine cave-in that broke his back and confined him for the rest of his life to a wheelchair. Wheelchairs, in those days, were large, cumbersome contrivances that could not be folded up when not in use. Mr. Everest used to grouse a good deal about how hard his chair was on him. His displeasure often burned the ears of Harry Jennings Sr., a close friend and a mechanical engineer. They talked a lot about a better wheelchair, and finally, in 1933, Mr. Jennings built one in his garage. Fashioned out of steel tubing, it was lightweight, collapsible and could fit in a car. Life for Mr. Everest became much easier.