The secret's out: Tons of water in Oregon's Cascades

by Michael Milstein, The Oregonian
Sunday October 19, 2008, 10:05 PM

Steelhead Falls on the Deschutes River, one of the rivers fed by the hidden reservoir under the Cascades, runs full even in the fall.

The most valuable resource in the national forests atop the Oregon Cascades may not be the timber and recreation spots they're known for, but something else that's largely invisible: water.

Scientists from the U.S. Forest Service and Oregon State University have in recent years quietly realized that the high Cascades in Oregon and far Northern California contain an immense subterranean reservoir about as large as the biggest man-made reservoirs in the country.

The secret stockpile stores close to seven years' worth of Oregon rain and snow and is likely to become increasingly precious, even priceless, as population and climate add pressure to water supplies.

The reservoir hides within young volcanic rock -- less than 1 million years old -- in the highest reaches of the Cascades. The rock is so full of cracks and fissures it forms a kind of vast geological sponge. Heavy rain and snow falling on the rock percolate into the sponge, like a river filling a reservoir.

"It's not just the fact we get a lot of rain in Oregon that gives us copious amounts of water," says Gordon Grant, a research hydrologist at the U.S. Forest Service's Pacific Northwest Research Station leading the research. "It's the unique geology -- the plumbing system -- that allows us to retain much of it."

It's easily one of the biggest groundwater systems known in a mountainous region anywhere on the planet, he said.

Some water leaks steadily from the hidden reservoir, gushing from springs into rivers such as the McKenzie, Deschutes and Clackamas. Many of the rivers flow into the Willamette, keeping the river through Portland full of water even now, when mountain snow that feeds many other Western rivers is long gone and the rivers are just trickles.

"The geology is kind of like your genetic code in terms of the water we can get out of the Willamette basin," said Julia Jones, a geosciences professor at Oregon State University and vice chair of a National Research Council panel examining the connection between forests and water.

That all-year reliability of water from the underground store puts Oregon in a much stronger position than the rest of the West as global warming dries out nearby states, some already suffering through record drought.

At the same time, it may also make the Northwest a sought-after source of future water for the rest of the West. Southwest states have already floated the far-out idea of piping in water from the Columbia River. Businesses such as technology companies that require reliable water supplies for manufacturing may see the consistency of Oregon's enormous reservoir as a strategic advantage.

Looking into the future, "the value of water coming out of this system absolutely exceeds any other economic value from national forestlands," Grant says.

The underground pool lies almost entirely within Oregon. Volcanic rock in the highest reaches of the Oregon Cascades is typically less than a few million years old, with cracks and crevices that store far more water than the older, dense Washington Cascades. The spongy rock and the water it holds extend into northeastern California, and some of its spring water emerges into the Sacramento River system.
More study proposed

A group of OSU and other scientists including Grant are proposing more research to better gauge the subterranean supply and examine the potential effects if thirsty regions such as California and the Southwest someday seek to extract its water.

"We need to have a better understanding of what's there so we're in a position to make wise decisions about it in the future," said Michael Campana, director of the Institute for Water and Watersheds at Oregon State University. "There's an exceptionally big resource here, and someone, someday, may want to use it."

Grant took flak from colleagues last summer after Campana posted a California newspaper article on his blog, WaterWired. It described a lecture by Grant and hinted that Oregon's hidden reservoir could help cure California's perennial water shortage.

Some thought Grant was suggesting the water might go to California. Not so, says Grant. Rather, he wanted "to focus attention on where water comes from now, and how those places are likely to become increasingly important in a climate-warmed and water-challenged future," he wrote in a response on Campana's blog.

But the exchange highlighted the value of the underground water system, and researchers are now considering how to better understand it.
On par with Lake Mead

The volume of the underground water is difficult to fathom. Most of it lies in a layer around 500 feet thick, Grant says. Rough estimates suggest the system probably holds at least as much water as Lake Mead, the largest constructed reservoir in the nation.

Actually, it probably holds much more, but some water remains locked in cracks and crevices and cannot find its way out. While eight years of drought has left Lake Mead half full, however, Oregon's reservoir is still brimming.

Given the enormous value of the reservoir of pristine water, Grant says, land managers may need to think about new ways to safeguard its quality. For instance, it might be worth considering limits on transport of hazardous materials across some parts of the Cascades to reduce the risk of spills contaminating the water, he said.

Forests such as those that house the groundwater system must be managed in the future to promote sustainable water supplies as much as anything else, Jones' National Research Council panel concluded in a report last summer.

That's especially true as growth and development erode forested areas that have long held crucial watersheds, Jones said.
Huge springs discovered

When Grant and his team began studying the water system, they found its water spilling from large springs so little-known they don't appear on maps. One spring pours out a full 1 percent of the summer volume of the Willamette River -- some 43 million gallons a day, enough to supply almost half of Portland's year-round water needs.

Grant isn't highlighting its location.

"You can be sure the bottled water people would like to know all about it," he said.

He and his colleagues are also studying the way global warming may influence the underground water supply. Many climate models show that as temperatures rise, more winter snow will fall as rain instead and run off the landscape more quickly. Less snow will remain to melt and feed rivers in summer, when water is needed most.

The underground Cascade reservoir changes the picture in the rivers its springs supply. Water entering the reservoir as rain or melting snow pushes water out of the springs, so as less water flows in from melting snow in the summer, less will exit the springs, Grant says.

However, because so much water remains underground, plenty is left to flow out during the summer. That means rivers fed by the reservoir's springs -- though reduced somewhat by climate change -- will keep flowing far more reliably than rivers fed by snowmelt alone.

"The high Cascades will continue to have water when others are losing it," Grant said. "When people look for where water comes from in the West, this is a place they will look."

-- Michael Milstein; [email protected]