Landing Strip for Shuttle Sinking From Use of Wells : Water: Officials say growth in Antelope Valley has increased pumping, which has caused the lake bed at Edwards to subside as much as three feet.

The dry lake runways at Edwards Air Force Base, famous as the landing ground of the space shuttles, are cracking and sinking, apparently because the Antelope Valley’s growing population is sucking ground water from beneath them, federal officials reported Thursday.

During a hearing by the California Water Commission in Lancaster, officials of the Air Force and the U.S. Geological Survey said they believe development there and in nearby Palmdale had led to lower ground water levels, causing the soil under the air base to settle.

“It’s very obvious ground water pumpage throughout the Antelope Valley is having an impact on the subsidence at Edwards Air Force Base,” said John Klein, district chief of the survey’s water resources division. The agency is conducting a five-year, $6-million study of the problem and other water-use issues for the Air Force.

Portions of the base’s 44-square-mile Rogers Dry Lake bed, used by space shuttles and “The Right Stuff” test pilots, are believed to have subsided as much as three feet. Air Force officials said the lake bed is broken by fissures up to 3 feet wide, 2 feet deep and hundreds of feet long.

Klein and Air Force officials told the commission that the subsidence problem at the base, as well as a related drinking water shortage there, could worsen unless, in Klein’s words, “major steps are taken to limit further withdrawals” of ground water in the region.

The problem is so serious that the Air Force has been able to continue using the clay runways only by using up to 10 people full time to fill in the cracks. “We’re seeing severe cracks throughout the whole lake bed,” but the Air Force will be able to continue using the lake bed as a runway as long as repairs are kept up, said Col. Peter Walsh, the base’s civil engineer.

Located about 35 miles northeast of Lancaster, Edwards is home of the Air Force’s famed Flight Test Center and is the second-largest Air Force base in the continental United States, covering about 300,000 acres, officials said. The entire region gets its water from the same underground source.

During the past decade, the population of the Antelope Valley has nearly doubled from 100,000 to almost 200,000 and water use has climbed.

Air Force officials stressed that they were not calling for a slowdown of residential development in the region. Instead, they asked that the area’s water agencies shift away from ground water and instead use more supplies from the California Aqueduct, which carries water from Northern California.

The region already gets about 40% to 50% of its water from the State Water Project’s aqueduct, said Wallace Spinarski, general manager of the Antelope Valley/East Kern Water Agency. But that supply has not been secure, particularly during droughts, and officials have also relied on local ground water.

Klein said the ground water level at Edwards has dropped from about 10 feet below the surface in 1948 to a recent level of about 100 feet below. But Klein said it is difficult to tell how much of the decline is attributable to the rapid growth of recent years.

Air Force officials first noticed the problem several years ago, Walsh said, and “the rate of subsidence is increasing . . . as the rate of withdrawal from the aquifer increases.”

In addition to ground water pumping, Klein said, massive development in the Lancaster-Palmdale area also appears to have contributed to Edwards’ water problem by blocking rainfall from reaching formerly open areas, shifting the underground water flow away from Edwards, he said.

Calling the base “a national asset,” Walsh said the Antelope Valley region needs to develop a comprehensive water management plan that would address the need to preserve the area’s ground water. That presumably would halt further damage to the base’s dry lake bed, he said.

But that is not the base’s only problem. During the past summer, the facility was plagued by a drinking water shortage and had to adopt strict conservation measures because many of its ground water wells, the base’s only water supply for now, had to be shut down, Walsh said.

Nine wells have been closed, three because of natural arsenic contamination and the others because of aging equipment and declining water flow, Walsh said. Twelve remaining wells should carry the base through low water use months until this summer.