An unusual western water fight between Hopi Indians and the nation's largest coal producer has forced Interior Secretary Manuel Lujan Jr. to pick sides, and the coal company is not happy with his choice.

Overruling his Office of Surface Mining (OSM), Lujan last week declined to issue a final permit allowing Peabody Coal Co. to pump 1.5 billion gallons a year of drinking-quality groundwater for the operation of its 17,000-acre Black Mesa-Kayenta mine in northeastern Arizona.

The company mixes the water with crushed coal, then pumps it 273 miles across the Arizona desert to a generating station that lights homes in Los Angeles and Las Vegas. But leaders of the Hopi tribe say the pumping operation threatens the reservation's drinking and irrigation supplies, and they asked Lujan to postpone the permit decision, pending further study.

"He made a decision that was wise and courageous," said Vernon Masayesva, chairman of the Hopi tribe. "We have come out very strongly and said it is not our intent to stop mining, but we want to guarantee that our water supply is not endangered."

Peabody can continue to siphon groundwater while the government conducts new studies. But the postponement prompted outrage and legal threats by the St. Louis-based company, which was expecting the permit after five and a half years of environmental study. Company officials say there is plenty of groundwater to serve both the mine and the Hopi tribe, blaming current shortages on drought.

"I think it's an emotional reaction," said E.L. Sullivan, director of legal and public affairs for the company's western division. "The secretary is attempting to politicize this issue in order to be perceived as being responsive to Native Americans and their concerns."

OSM concurs with the company's view that the mine poses no threat to the tribe's water supply, and Lujan's decision to overrule the agency came as something of a surprise. But it also reflects Lujan's continuing emphasis on Indian concerns that aides say grows out of his New Mexico upbringing and Hispanic roots.

"This is his area," said Steven Goldstein, Lujan's press secretary. "Having grown up in a tri-cultural environment, he's more sensitive to the concerns of American Indians."

Nor was Lujan's decision entirely without scientific justification. The Environmental Protection Agency found OSM water studies were "insufficient," warning of "potential significant adverse impacts" stemming from the groundwater pumping.

EPA also echoed Hopi concerns about the wisdom of diverting scarce drinking water to industrial use in a desert climate. "We're talking about pure mineral water," said Masayesva. "We could probably become billionaires if we bottled it."

Straddling the border of the Hopi and Navajo reservations in northeastern Arizona, the Black Mesa-Kayenta Mine produces an annual 4.5 million tons of coal and is the largest surface mine in the United States, according to OSM. Some of the coal is shipped 75 miles by rail to a power plant in Page, Ariz., but the remainder goes by pipeline to the Mohave Generating Station near the Nevada border. The coal fires the generators and the water helps cool them.

The Hopis have tolerated, even encouraged, this arrangement for the past 24 years, and it is easy to see why. For the privilege of mining coal and water from Hopi lands, Peabody pays the tribe royalties to the tune of $10 million per year, enough to cover 80 percent of its annual budget.

But in recent years the tribe has begun to worry that the slurry pipeline is draining the so-called Navajo aquifer, a vast underground lake trapped in porous sandstone 3,000 feet below the desert surface. The aquifer supplies the reservation's municipal drinking-water wells and also feeds springs in Moenkopi Wash, a seasonal stream that irrigates squash, melon and corn fields.

"The washes are bone dry, even in March," said Masayesva, who hired the public relations firm Burson-Marsteller to press the tribe's case in Washington. "No one has been able to prove . . . conclusively that the dewatering is caused by the mine, but the fact that the springs are drying up indicates there is a lowering of the water levels."

But OSM Director Harry M. Snyder said in an interview that "72 pounds of hydrologic studies" have yielded "no evidence of material damage from the water withdrawal." Every year the pipeline slurps up 4,000 acre-feet -- about 1.5 billion gallons -- but that is far below the annual "recharge rate" of about 15,000 acre-feet from rainfall and surface runoff, according to Snyder.

"OSM is satisfied," he said. "I think the tribes are still not satisfied, and I think the secretary wants additional information."

One Interior official suggested that the tribe's alarm over dwindling water supplies is related to a drought that tree-ring studies indicate is the worst to hit the area in 1,600 years. "They don't like the use of what they perceive to be their water to slurry coal," the official said. "They don't like the deal that they made."

Tribal officials acknowledge that drought has exacerbated the water shortage in Moenkopi Wash, but they also suggest that the pipeline is to blame. "This area should not be behaving this way even in a drought, because the ultimate source of the water is thousands of feet down," said Steve Blodgett, the tribe's reclamation specialist.

Lujan found such arguments convincing enough that he wants the company to consider alternatives to moving its coal by pipeline, among them the possibility of a new rail line. But Peabody officials called that proposal far-fetched.

"The elevations alone call into question whether we could even build one," said Sullivan.