Beam me to Planet Gore !
Posted on 09/15/2009 2:26:24 PM PDT by crazyhorse691
In a warming world, scientists have told us to expect more rain and less snow in the Northwest -- but not less overall precipitation.
New evidence, however, suggests that dry years are becoming more severely dry across the region.
Even in the rain-drenched Northwest, the trend could escalate water conflicts if it continues. Farmers, conservationists and city water managers would face severe challenges trying to balance human needs with the survival requirements of endangered salmon that need cold, clean, rushing water.
Researchers with the U.S. Forest Service looked for changes in the amount of water flowing out of mountain basins since 1948 at 43 rivers and streams across Oregon, Washington, Idaho and western Montana.
Few rivers showed significant declines in runoff until researchers isolated the driest 25 percent of years.
Then nearly three-quarters of river basins showed severe decreases in water flow. Runoff fell by 30 percent or greater in most streams, and by nearly 50 percent at some locations during dry years.
"And those are really important years," says study author Charlie Luce, a Forest Service research hydrologist in Boise.
"Those are the years that test the trees, whether they live, die, or catch on fire. Those are the years that test the fish, that test the farmers and the water managers." The journal Geophysical Research Letters published the study online Aug. 22.
Previous studies found little or no change in river flow or annual precipitation because they looked at average or median values. The region's average annual precipitation actually increased by about 10 percent over the past century, according to the U.S. Global Change Research Program.
Philip Mote, director of the Oregon Climate Change Research Institute at Oregon State University, says the new findings are important and "potentially very worrisome."
"But we can't be sure these trends will continue," Mote says.
Global warming The pattern found in the new study runs contrary to predictions based on computer simulations of global warming. Those suggest the Northwest should continue to receive about the same amount of precipitation but that runoff will peak earlier and leave rivers emptier in hot summer months.
That's because rising temperatures are likely to cause more precipitation to fall as rain instead of snow and the mountain snowpack to melt earlier in the spring. In a new forecast for western Washington, for instance, Susan Dickerson and Robert Mitchell at Western Washington University in Bellingham predict increases in winter flows, decreases in summer flows, and a shift toward earlier spring snowmelt as the regional climate warms.
"The biggest hydrologic change is a shift in timing of flow, not a change in total annual flow," Mote says. Since 1920, snow accumulation in Northwest mountains has fallen about 25 percent, Mote has calculated.
The new findings paint a more complicated picture. Not only will we see more rain and earlier snowmelts, but we also could see significant decreases in overall precipitation during drought years.
"It would just be harder and harder to keep farming this dry ground if the dry years get worse," says Gary Westcott, who grew up on a ranch in eastern Oregon and has run a small farm near Vale since 1979.
Droughts have hit Northwest farmers hard in recent years. Federal officials in 2002 halted irrigation to about 1,200 farms to shield endangered Klamath Basin fish from a worsening drought. That brought an estimated net loss of $27 million to $46 million in crop revenues, of which taxpayers covered about $30 million in emergency payments.
In 2005, Gov. Ted Kulongoski declared drought disaster emergencies in six counties. In 2007, some eastern Oregon rivers produced about a third of their average runoff, and some reservoirs ran dry months before the end of the growing season.
Impact on irrigation In his years of farming, Westcott hasn't noted an increased severity in drought years. Rather, he says, drought seems more frequent.
Drier winters would undermine plans to extend irrigation with more reservoirs. Washington passed a law in 2006 creating a Columbia River management plan calling for new reservoirs for eastern Washington farmers. Kulongoski has backed the idea of building water storage areas in eastern Oregon to help farmers and maintain instream flows for fish.
The new study doesn't prove that dry years are getting drier because of less rain and snow, just that rivers run much lower than they did decades ago.
"It is not clear whether precipitation is decreasing, or whether water use is increasing," says Julia Jones, an associate professor in the department of forest ecosystems and society at Oregon State University.
In the Northwest, forests consume huge amounts of water. Dense, tall stands of native Douglas firs can soak up more than 40 percent of the precipitation that falls in a river basin.
Several land use changes since the 1950s have tended to increase water use, Jones says. Fire suppression has allowed forests to expand in some basins. Clear-cutting of old growth and replanting young, fast-growing trees has increased water consumption in summer. In some watersheds, deep-rooted trees that extract more water than grasses are overtaking abandoned farm fields and pastures.
Warmer springs and falls, due to climate change, could extend the growing season of trees and shrubs -- and their water intake.
No matter the cause, if the trends are real, Jones says, the potential for water conflicts will increase.
Climate models Because climate models don't point to decreasing precipitation, says Mote, the OSU climate scientist, rising greenhouse gases may have nothing to do with decreased runoff in dry years. "You can't conclude based on this study that climate models are missing something."
Luce agrees that it's impossible to link greenhouse gases and a warming climate to less precipitation in dry years. But he says the evidence is fairly strong that the decreases in river runoff are the result of less rain and snow and that the shift is contrary to climate models. Luce plans to extend his analysis to precipitation records but says those records aren't as reliable as the numbers on runoff.
To account for changes in water use, Luce tracked forest water consumption and evaporative losses in one river basin and found that those water losses could not explain the decreases in river flow. Luce and co-author Z.A. Holden with the Forest Service in Missoula, Mont., also noted sharp decreases in flow in two river basins in which large tracts of forest had been lost to fires -- which should have increased runoff by allowing more precipitation to reach streams.
Luce speculates that changes in the Pacific Ocean circulation pattern known as the El Nino Southern Oscillation may be the driving force behind his findings. Scientists have linked shifts in the El Nino cycle to droughts in some regions and torrential rains in others. In recent years, some researchers have proposed that global warming may be altering El Nino events and intensifying droughts.
But researchers don't know enough to predict how the El Nino cycle will respond to future climate warming.
"Climate models embody the theory as we understand it," Luce says. "Now we've got a new set of observations that don't quite agree with the theory. People can go out and refine the theory."
--- Joe Rojas-Burke; joerojas@news.oregonian.com
Rain, rivers, there’s a connection? Who knew?
Your tax dollars at work.
I imagine that the grant applications have already been submitted to fund a study to find out if the reverse is also true: does river runoff increase when it rains?
My prediction is that solar dimming will have already peaked just prior to Christmas, and we will be seeing slightly longer daylight hours by Christmas.
I also predict this has something to do with the Winter Solstice. Now let some GW fanatic prove me wrong...
Computer climate models are what GW is based upon. So, is this genius stating that these climate models aren't irrefutable, leaving GW the hoax of the Century?
From Professor Obvious —
New study shows river runoff decreases in driest years in Oregon, Northwest
Hey, solar dimming is my scam...go git your own:-)
Uh, uh. Yours is solar dimming, mine is Winter Solstice.
This is the same state that gave us the congresscritter that wants to put “GPS-Taxicab-tax-Mileage-meters” on all of our cars.
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I wonder if there is somewhere I can apply for a grant to study why I like honey on my biscuits.
Appears those scientists connected that dot, huh. Brillent!
You’re almost correct. The real culprit is the slow leakage of light from the northern hemisphere to the southern hemisphere. This is also a man made phenomenon. If it is not stopped, we in the northern will soon be in total, perpetual darkness.
Say WA? Evergreen State ping
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