March 2009

U.S. Water News Online

BEND, Ore. — A mysterious drop in groundwater levels in the triangle between Redmond, Prineville and Powell Butte is under investigation by state and federal scientists.

One mile south of Redmond, groundwater levels have declined nearly 20 feet in the last 15 years.

If that trend continues, it would be “troubling,” said Doug Woodcock, a Salem-based groundwater manager with the Oregon Water Resources Department.

A July 2008 U.S. Geological Survey document said some of the area's groundwater declines are because the basin started receiving less rain in the 1950s.

But it added that many wells “in the more developed parts of the basin appear to show declines larger than what would be expected due to climate alone.”

If that is true, then it could have “important implications” for the Deschutes groundwater mitigation program, the document said.

Depending on what the new study finds, it could reignite debate over a touchy subject — how water is managed in the Deschutes River basin.

“Basically, what we're trying to get a read on is, how solid (is) our management in this basin?” Woodcock said.

The state's Deschutes groundwater mitigation program requires farmers and developers to purchase water rights to offset the effect their activities might have on the Deschutes River and its tributaries.

But if the new study suggests the program is not protecting groundwater supplies, then it could lead to tighter rules, according to Kimberley Priestley of the group Water Watch of Oregon.

“I would think it would be of interest not only to the state but to developers,” she said of the study. “If we're seeing declines, then that could bring a whole new layer of management.”

For months, state officials have been working with USGS hydrologists on the new study to update a computer groundwater model they haven't changed in years.

The three-dimensional model will show the number and location of new wells, add more recent data on rain and snowfall, and show that some irrigation canals have been replaced by pipes affecting recharge of the aquifer.

Once that work is complete, hydrologists will run tests to determine how much of the groundwater reduction is due to pumping, how much to irrigation changes, and how much is attributable to reduced rain and snowfall.

Kevin Limbeck, board president of the Powell Butte View Estates Water District, says he is keeping an open mind, but suspects the rapid pace of development in recent years is largely to blame.

His district serves 88 homes perched on the butte's western slope. He says the district drilled its well more than a decade ago, and has seen its water level drop 15-20 feet.

“There've been quite a few large wells put down in the Powell Butte area.”

Marshall Gannett, the USGS hydrologist who is spearheading the study, said he doesn't think the declines pose an “imminent risk” to the basin's groundwater resource.

The study is expected to be completed by year's end.

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