A lack of water has hampered crews’ efforts to beat back the fires.

Firefighters’ work in Pacific Palisades pushed the local water supply system to its limits early on Wednesday morning, leaving some fire hydrants dry as crews battled the Palisades fire.

At a news conference on Wednesday, officials said firefighters drew water faster than local tanks could be refilled, causing the shortage.

The water shortage has heightened tensions on the ground. At the crest of Sunset Boulevard on Wednesday morning, a desperate man dropped to his knees in front of a firefighter who was battling a fire consuming the home next door, begging him to turn the water on the flames threatening his own home. Another firefighter warned, “We’re down to 25 percent. Hold off.”

The firefighters attached their hose to a new hydrant, only to discover that it was empty. They sprinted toward another, hoping for enough water to fight the fast-moving flames.

Janisse Quiñones, the chief executive officer of the Los Angeles Department of Water and Power, said at the news conference that the system relies on three large water tanks, each holding about a million gallons, to maintain pressure for fire hydrants and uphill areas.

She said two tanks were depleted on Tuesday, and the third ran dry around 3 a.m. Wednesday as water demand surged to four times the normal rate for 15 consecutive hours.

“We pushed the system to the extreme,” she said.

Mark Pestrella, the director of Los Angeles County Public Works, said wind and poor visibility had hindered air support for supplying water, but county and city water reservoirs are available and on standby. Once air support is possible, he said, both fixed-wing aircraft and helicopters will draw water from the system.

“A firefight with multiple fire hydrants drawing water from the system for several hours is unsustainable,” he said. “This is a known fact.”

Both Ms. Quiñones and Mr. Pestrella urged residents to conserve water for firefighters’ use.

Mr. Pestrella recommended that residents turn off their water and gas before evacuating “so that we can continue to have that water supply for the hydrant system.”

Officials did not specify how many hydrants ran dry or detail how the lack of water affected firefighting efforts.

The Palisades fire started Tuesday morning in the affluent Pacific Palisades neighborhood west of downtown Los Angeles. It has consumed more than 5,000 acres, destroyed many structures and prompted evacuation orders for about 37,000 residents.