* Water pressures
* Models predict less in summer, more in winter

Too much water in the winter. Not enough in the summer. This could be the twisted logic global warming applies to the Skagit River.

Early research by climate change scientists suggests that the Skagit will flow higher in the flood-prone winter months and lower in the summer, when salmon, farmers and thirsty residents need it most. Topping this off is a recent trend toward more extreme fluctuations in wintertime precipitation that could push the river above flood stage more regularly, scientists warn.

Those who set policy for flood control and water resource management are just catching up to the challenge that’s expected in the coming decades. Some would refrain from decision making for now.

Dan Swenson, a water resources supervisor for the state Department of Ecology, said government agencies need to learn more about how the Skagit system will respond to global warming before they can change policies with confidence.

Scientists at the University of Washington’s Climate Impacts Group are developing a computer model to more accurately show how the Skagit will flow in a warmer climate. The first study results are expected next year.

UW scientists have already developed a model that gives a crude picture of how the Skagit’s flows will change under global warming. The results are still useful, according to Alan Hamlet, the scientist who devised the model. They indicate the size of the changes to the river’s flow that can be expected when more winter precipitation falls as rain instead of snow.

Hamlet’s simulation compares the river’s annual flow in the late 20th century with a projection for the mid-21st century. Because less water will be stored in the mountains as snow to feed the river in the late spring and summer, the model predicts more flow in winter and less in summer.

But this future trend — warmer temperatures and higher winter flows — only sets the stage for an increased flood risk. Floods in the Skagit Valley occur after an extreme rain event, often in November or December.

Climate factors don’t determine where a major flood strikes after a given storm, whether it’s the Chehalis basin, the Skagit or somewhere else. But some scientists believe the chances of a large flood have increased in the past 30 years, in part because of global warming, but also because storms like the one that inundated the Chehalis basin earlier this month have become more common.

Hamlet’s computer simulations indicate that a warmer climate increases flood risk in those river basins that contain snow in the winter. As Hamlet put it, global warming effectively increases the size of a river basin because rain falls over a larger area in a warmer climate, contributing more water to the flood as less is stored as snow.

What’s not so well understood is a change that has appeared in rainfall patterns since about 1973. Total rainfall amounts have changed little, but changes in rainfall variability have gotten the attention of scientists.

“The wet years are wetter, the dry years are drier,” Hamlet said. “This increases the flood risk. The 100-year flood gets bigger due to the precipitation change.”

Stream gauge measurements appear to support this idea. Of the nine biggest floods to hit Concrete in the last 80 years, seven were recorded in 1980 or later — after rains became more variable.

“There’s little question that this 30-year period has seen increased flood risk in the western part of the state,” Hamlet said.

This can be attributed in part to global warming, Hamlet said, due to the “more rain, less snow” factor. The other contributor is the “wet years are wetter” factor.

Scientists have not been able to connect this change in precipitation patterns to global warming, so it may not continue to contribute to the flood risk, even as global warming persists for another century or more.

Planners wait and see

Flood planning in Skagit County has yet to take climate change into account. Ric Boge, surface water manager for Skagit County, said he relies on input from Ecology and the U.S. Army Corps of Engineers on how to address global warming.

How will global warming influence future flood projects?

“We’ve asked the corps that same question,” Boge said. “Should we be factoring in anything? Changes in amount of precipitation, when it comes, how it comes? The answer we’re consistently getting back is, they don’t have any direction yet or reliable information to ... project how floods are going to be changing in the future.”

Corps officials confirmed that global warming does not factor into the ongoing flood protection study for the Skagit. They said they haven’t seen a strong correlation between global warming and flooding.

“If someone statistically essentially proves it, I’m pretty sure we’ll incorporate it,” corps hydraulic engineer Ted Perkins said.

The Federal Emergency Management Agency is also not taking global warming into account as it draws up new flood insurance maps for the Skagit basin.

The latest FEMA map, due in the next few months, will update the valley’s floodplain and give flood elevations in the event of a 100-year flood — a statistical event that has a 1 percent chance of occurring in a given year. It’s the same 100-year flood that Hamlet said may be getting bigger as a result of climate changes.

Even so, the maps don’t look ahead to possible changes, according to Mark Carey, the director of FEMA’s mitigation division. Maps are based on current conditions, as derived from historical records, gauge readings and precipitation records, he said.

FEMA updates the flood maps as often as possible, as funding allows, to account for changes as they occur, Carey said.

County Commissioner Sharon Dillon said an aggressive flood policy is needed, whether or not global warming heightens the risk.

“I think that there’s a concern, even taking out the global warming part of it, of allowing building close to any river, stream or creek,” Dillon said.

After the devastating floods in Southwest Washington, the time has come for the government to “persuade” home and business owners not to build close to a body of water, Dillon said. This could mean establishing a development-free floodway in the lower Skagit.

“We may not like to do this, but prudently as leaders, we really need to start looking at it,” she said.

Summer water

For all the extra water that’s expected to fill the valley in winter, global warming’s cruel irony is that it will bring less than it does now during the driest months.

Salmon, farmers and water purveyors such as the Skagit PUD and the city of Anacortes will compete for an ever diminishing resource, even as the population and demand for residential water grows.

Hamlet’s crude model of the Skagit predicts flows will decrease by 23 percent from April to September due to a reduced snowpack. The river’s flow rate is already prone to fall below 10,000 cubic feet per second in August and September, months when the state’s instream flow rule sets aside 10,000 cfs as a water right for the salmon.

Hamlet’s analysis doesn’t take into account the disappearance of the glaciers, which supply a quarter of the North Cascades’ water in the summer. But it also doesn’t account for the role the power utilities play as they release water through the Baker and Ross dams to boost flow levels for fish.

Ed Schild, director of hydroelectric resources for Puget Sound Energy, said there will be enough water behind the dams to support salmon in the future, even if there is less snowpack. Although the amount of snow will decrease, overall precipitation is likely to increase in the winter as a result of global warming, according to scientists at the Climate Impacts Group.

“You might end up with less (power) generation, but we’ll still fill up the reservoir,” Schild said.

If summers are drier and hotter, as climate change scientists predict, PSE may feel pressure to release more water in the summer for the benefit of salmon or to meet an increasing power demand.

“It could put some pressure on what you do have stored. It may be that we put water out a little sooner,” Schild said.

Something’s got to give

The salmon are assured their share of water by law through the instream flow rule. Swenson of Ecology said that at this point, the state wouldn’t consider lowering the mandatory flow levels. If summer flows dip below 10,000 cfs more regularly, water users who acquired their water right after the 2001 rule would be asked more often not to turn on their taps.

Or if the lakes behind the Baker dams relinquish their water before the end of the summer to keep the flow level up, then the campers, the anglers and the water skiers will feel the pinch.

“The biggest single impact will be on recreation rather than generation or fish,” Schild said.

Farming advocates are starting to think about adjusting to a smaller water supply during the height of irrigation season. Water quantities for irrigation are already a concern.

“We know we’re right on the edge in terms of having enough water to meet our needs,” said Mike Rundlett, environmental affairs manager for the Western Washington Agricultural Association.

Even so, the estimated 15,000 acres of crops that are irrigated in the county aren’t much competition for Skagit water. Irrigation diverts only 0.3 percent of the Skagit’s flow in September. Most irrigation water comes from underground, Rundlett said.

A U.S. Geological Survey study will shed more light on how groundwater and surface water are connected in the Skagit and Samish basins. The results could change where farmers get their water, so they can minimize their already small impact on the Skagit, Rundlett said.

“Whatever solution we come up with has to work for fish as well as farming,” he said.

A new era of water planning

Anacortes and the PUD, the two major water purveyors in the county, have water rights that take priority over the instream flow rule for salmon. But Swenson said it might still make sense for the two water purveyors to change their operations to accommodate climate change.

The PUD and Anacortes already have a water shortage response plan that dates back to 1996, when there was a lot less understanding of the impacts of global warming. Under certain conditions, the response plan calls for mandatory restriction of irrigation and yard watering, and water rationing at homes and businesses.

“That seemed like a pretty unlikely possibility 12 years ago, and it seemed pretty easy to adopt because it seemed far-fetched that we’d have to ration water use. But with global warming you’ve got to wonder just whether that could come into play more over the years,” said Ian Munce, Anacortes’ city attorney and planning director, who also takes the lead in the city’s water management.

The PUD won’t be concerned if global warming reduces the flow of snow-fed rivers and streams in the summer, Planning Engineer Scott Spahr said. The Judy Reservoir, which holds the PUD’s water, is filled in the wet months by mountain streams that already run dry in the summer, Spahr said.

The PUD is expanding its capacity to serve a growing population over the next 50 years by building a pump station that will divert water from the Skagit into the reservoir. The pump will operate during those times of the year that aren’t vital to salmon, Spahr said.

“I think that we’re a lot less vulnerable than other water systems that don’t have a reservoir like we do to act as an insulator,” Spahr said.

In Anacortes, which does not have a reservoir, Munce said the next round of long-range water resource planning will address a future with less water. There’s a lot of room to improve water conservation, re-use and storage practices, he said.

“We haven’t even scratched the surface of water conservation and water management, in my opinion, and the next round of water planning will because now it’s required under state law,” he said.

Munce mentioned the idea of taking water treated at the Anacortes wastewater plant and piping it to the refineries for their use.

“They’re already doing a lot of water re-use over there. These are issues people are going to demand,” Munce said.

Skagit Warming Series:
Skagit Warming Page
Climate change and the Skagit Valley
Temperatures rising, glaciers melting in Northwest
Nature’s Laboratory
Researchers explore effects of climate change on health
Climate change poses threat to regional icons
Warming shifts odds away from salmon survival
Climate change could have dramatic impact on local agricultural scene
Cashing in on global warming
Warming: A rising tide
Tribe, La Conner on front lines
Green Power
Nuclear power unlikely alternative
Skagit Warming: Government action
Climate and You
What You Can Do
Why turn off the lights?
Skagit Warming: Tell us what you think

• Ralph Schwartz can be reached at 360-416-2138 or .