Water Table Plummets in Nevada River Basin

Ground-water levels have dropped significantly in parts of Nevada due to decades of irrigation and, more recently, the pumping of billions of gallons of water out of gold mines, a new study shows.

As a result, the water table has fallen as much as 1,000 feet around some of the largest open-pit gold mines in northern Nevada’s Humboldt River Basin, the U.S. Geological Survey says.

For now, the water loss is hard to see from above ground, since the water being pumped from the bedrock is being poured onto the surface, substantially increasing the flow of the Humboldt River.

But environmentalists fear that once the pumping ends, what water hasn’t flowed down the river will drain deep inside the Earth. That could cause water shortages for farmers and municipal water supplies, especially if drought returns after five consecutive years of wet weather.

The federal hydrologists who did the study and the mining officials who supported it say there’s no immediate reason for alarm.

The USGS determined in the five-year study of the middle Humboldt River basin that ground-water levels had declined as much as 70 feet over the last 30 to 40 years in areas with irrigated farms.

The more serious declines, from 200 feet to 1,000 feet, were recorded near gold mines in the last 10 years, primarily at the largest mines in Boulder Flat.

“The long-term concern is that because the ground water has been removed from storage, it is not available for any future uses,” said Russell Plume, a USGS hydrologist and project chief. “In some cases where there are large water-level declines, it can interfere with other uses. So far, that hasn’t happened.”

The study is the first of its kind in the nation, pulling together data on “dewatering” in 14 separate valleys with 14 gold-mining operations. The basin is home to some of the largest gold deposits in the world.

Mining companies pumped 113,000 acre-feet of ground water from the mines in 1996 alone to get at the precious metal, the USGS said.

That’s equal to about 38 billion gallons, more than twice as much water as is used in a typical year in the Reno-Sparks area.

“This isn’t a news flash. It is more a case of putting information together,” said Paul Pettit, manager of hydrology for Newmont Gold in Carlin, Nev., one of the financial backers of the study.

Newmont Gold and Barrick Goldstrike Mines, Nevada’s two largest operations, have been conducting their own research on the subject for years.

“There has been a lot of concern about the potential for short-term and long-term effects,” Pettit said. “I think the message from the study is things aren’t as bad as you might think they are.”

Tom Myers, a trained hydrologist and environmental activist in Reno, disagrees. Myers, the conservation director for Friends of Nevada Wilderness and the Great Basin Mine Watch, says water has been drained from as far as 20 miles from the pits.

The USGS is preparing another study to determine how the pumping of water from the bedrock will affect surface water, streams and the wildlife that depends on them.

“If you take one wet sponge and put another wet sponge on top of it, then you take the bottom sponge and figure out a way to suck it dry without touching the top one, how much will it cause the top one to dry out?” Myers said.

“The top layer is what feeds the Humboldt River. It’s where water comes from for the ranchers downstream.”

Barrick Goldstrike’s spokesman, Vince Borg, said his company helped finance the report and is looking forward to learning more in the second study in the works.

“We’re not looking to pump at the current rates for very much longer,” Borg said. “It’s not as though the current pumping rates are going to continue toward infinity.”

The mining officials maintain that not enough water is being pumped to cause any long-term damage. Nevertheless, state regulators are keeping a close eye on the situation.

“We monitor these people to death,” said Hugh Ricci, deputy state engineer at the Nevada Division of Water Resources.

“We realize that when you pump this water out it is coming from someplace and it will have to be put back,” he said. “How that is all going to play out is something we hope to know more about as we continue to study it.”

The biggest dewatering impacts have been recorded at the Betze-Post, Genesis and Carlin Mines. In many cases, the USGS found that water pumped from mines is returned to the aquifer nearby.

“But in a couple of cases they cannot do that. It is not feasible. The water is released to the Humboldt River and heads downstream,” Plume said. “For practical purposes, that water has left the basin.”

Barrick Goldstrike Mines started dewatering the Betze-Post in 1990 and pumped up to 70,000 gallons per minute from the mine for most of the decade. Pumping levels are slowing this year.

Pettit said there have been no objections from farmers or ranchers about the mine dewatering. He said farmers downstream along the Humboldt River use the extra water to raise alfalfa.

Myers agrees that ranchers downstream “have more water than they know what to do with.”

“But what happens when they quit dewatering and not pumping water into the river?” he asked. “Where will the water come from to fill the pits that are 800 to 1,000 feet deep?”