If anyone despairs when reading the weather report first thing in the morning, it’s assistant chief Peter Velasquez, Jr. the head of the hydraulics department of the New York City Transit Authority.

On a dry and sunny day his department’s 700 or so pumps, at about 280 locations, push 13 million gallons of water out of the subway system and into New York City’s sewers. That’s the equivalent of all the wastewater produced by the city of Boca Raton, Fla., every day.

And on a wet day?

“It’s more water than I can measure,” Mr.Velaszquez said.

This year, 9.63 inches of rain have fallen in Central Park, about five inches more than the average rainfall for the city. For the 170 workers in the hydraulics department — one of the smallest in the authority’s force of 34,000 workers — this spells hours of scrambling to floods and overflows.

When water rises near the electrically charged third rail, it creates dangerous conditions for trains. There are no sensors in the subway tunnels to notify transit officials that there is flooding, so the hydraulics department relies entirely on reports called in by conductors, platform personnel, and customers. This was the case on the morning of July 5, when an inch of water fell on the city, resulting in suspensions on three subway lines for more than an hour.

The first problem for a responding hydraulics gang is just getting to the location of the “water condition,” a supervisor, Gliden Arroyo, said.

“You have to remember, we are using the same system that delays customers,” he said. Workers may move to a flood by taking trains, trucks, buses, or by walking. “We have to get there by any means necessary,” he said.

With water touching the third rail, a puddle can become a 600-volt landmine. Transit workers follow strict procedures to avoid getting hurt.

Most “conditions” like last week’s are caused by a backed-up drainage pipe or water coming in at a rate faster than the pumps can get rid of it. Lately the influx of free newspapers at subway stations has compounded the problem by clogging drains throughout the system.

A condition like last week’s is meager in comparison with some floods in the city’s history. The worst condition Mr. Velasquez has seen was in Harlem in the early 1990s, where a broken water main flooded a station at 125th Street and St. Nicholas Avenue up to the stairwell. Scuba divers had to be called in to shut down the main, and the Transit Authority had to bring in its most powerful weapon: one of two diesel-powered train cars outfitted with pumps that can get rid of 2,700 gallons of water a minute. It took an entire weekend to pump out the water, Mr.Velasquez said.

The department has an arsenal of smaller pumps as well, from special lightweight aluminum 100-gallon pumps, to the 600-gallon pumps that take an entire gang to pull onto a subway platform.

Thunderstorms they can handle, Mr. Velasquez said. It’s the unexpected and the expansive disaster that he fears most. A hurricane could cause massive flooding throughout the subway system.

“At some point, it would be too much to handle,” he said. “You’ve got rain plus wind. It basically would shut down the system.You hope not. You pray that it doesn’t.”

A terrorist threat like the plot against the PATH train tunnels reported last week are yet another concern. Mr. Velasquez said the Transit Authority has detailed plans for dealing with all types of emergencies.

“All we can do is prepare,” he said. In the meantime, his workers are continuing their 24-hour a day maintenance of the pumps, some of which are more than 100 years old.