Wow! The figures pile up on the severity of the flood of the Potomac River early last month.

On Thursday, Nov. 7, the river flow resulting from upstream rainstorms was a staggering 72 times as great as it had been just four days earlier.

According to the U.S. Geological Survey in Reston, these are the figures: On Sunday, Nov. 3, the Potomac was at what turned out to be its lowest point in the month (and about average for November), 2.6 billion gallons.

By Thursday, the high one-day figure for the month came when the river crested at 189 billion gallons, 72 times the Sunday level.

The average daily flow of the Potomac for November was 27 billion gallons, about 8.5 times normal.

The fresh water flow of all tributaries -- including the swollen James River past Richmond -- into the Chesapeake Bay set a modern average daily record for November of 106 billion gallons. The previous record, set in 1972, was 85 billion gallons.

A worrisome figure is the amount of sediment, including topsoil, that was washed last month down the Potomac toward Chesapeake Bay.

The federal agency said 1,134,000 tons of sediment was scoured by the river flow.

The previous November record was about one-quarter that amount, 286,000 tons, set in 1932; the normal figure is only 7,540 tons.

Now we know why the river early in November looked like a liquid Hershey bar. Metro Opens Sales Center

Sorry, but we missed the real story -- the unheralded opening last Thursday -- of Metro's new sales and information center on the upper level of the Metro Center subway station. Metro's announcement had chosen instead to emphasize yesterday morning's anticlimactic ceremonial opening, a nonnews event.

So, while we did not report on the ceremony, we consider it a civic duty to report that the center has indeed opened.

Riders can obtain tokens, tickets, flash passes, senior citizen and handicapped Farecards, precoded $10 subway Farecards, bus schedules and maps, and they can redeem tickets, tokens and Farecards.

Applications may also be filed for senior citizen identification cards.

The sales center, replacing facilities in the 1400 block of New York Avenue NW and at 10th Street and Pennsylvania Avenue NW that have been closed, cost $276,000. Customers can get to it from inside or outside the subway fare gates.

To reach the outside windows, however, one must use the Metro entrance on the southwest corner of 12th and F streets NW.

One serious complaint: The facility opens every weekday except holidays at 7:30 a.m., when one doubts many customers are about, and it closes at 3:30 p.m., inconveniently early for homebound commuters. Downs in Charge

Just for the record: With D.C. Mayor Marion Barry attending the National League of Cities convention in Seattle, the acting mayor is City Administrator Thomas Downs, one of three appointed deputy mayors.