When you ask the average Oregonian to describe the Willamette Valley, the first thing you’ll likely hear is, “It’s wet.” That seems obvious enough. If the Willamette Basin were a literal basin—like a flat-bottomed washtub—it would catch enough water within a year to fill it more than 5 feet deep.
Yet that’s not the whole story, says Sam Chan, an OSU Sea Grant watershed specialist. “It’s really more accurate to say that there’s a perceived abundance of water in the Willamette Basin.”
Chan is one of 35 OSU members of a scientific team that just finished a massive 6-year modeling study called Willamette Water 2100. Their verdict: With a growing population and a warming climate, parts of Willamette country will likely face water scarcity over the next 90 years.
The Willamette River and its tributaries drain a watershed that amounts to 12 percent of Oregon’s land area, holds 60 percent of the state’s population and some of its choicest farmlands, and hosts its three largest cities: Portland, Salem, and Eugene.
“We hope our findings will help policy-makers and other decision-makers identify the most effective measures to help the people in the Basin mitigate some of these scarcities, or adapt to them,” says OSU hydroclimatologist Anne Nolin, who leads the WW2100 team.
WW2100 makes predictions of likely outcomes under 20 different scenarios, says team member William Jaeger, an OSU economist and coauthor of a new OSU Extension publication, “Water, Economics, and Climate Change in the Willamette Basin, Oregon” which presents the model’s findings in detail.
“We started with the ‘business as usual’ scenario,” he says. “That gives us a baseline prediction of where and when water scarcity is likely to increase. And then we asked the ‘what-if’ questions.”
Such as: What if more farmers wanted to use irrigation? What if incentives were used to encourage water conservation in urban areas? What if the basin’s 13 federal reservoirs were managed differently? What if urban growth boundaries were changed? Every tweak sends ripples through the fabric of the model, altering its predictions in small or big ways.
The WW2100 model is equipped to answer such questions because it’s “a coupled human-natural system model, based on empirical data,” says Jaeger. That means the model draws on a sturdy foundation of research to describe in detail the ways in which people change the natural world, and are changed by it, as they go about their lives: choosing where to build, how to manage cities and farms, how to use and protect forests and streams, and a host of other individual and collective decisions.
“That combination of human and natural dynamics is really rare in a model,” Jaeger says.
The centerpiece of WW2100 is a software platform called Envision, developed by OSU ecological engineer and WW2100 team member John Bolte. Envision is the executive brain that enables all the different models to talk to one another, share data, and project water scarcity at different moments in time, across the whole basin and in the different watersheds that compose it.
“We learned things from this coupled modeling that we couldn’t have learned from projections from either natural dynamics or human systems alone,” says Nolin. For example, it would seem obvious that a warming climate would have an impact on water. Yet the research team found that future patterns of water scarcity—when and where it will happen and how big an impact it will have—depend much more on the “people” side: rising incomes, population growth, urban expansion, farming practices, conservation measures. And they depend on how the available tools—water laws, land use practices, reservoirs, utilities management, environmental regulations—are used to allocate what water there is.
“We’re fortunate here in the Willamette Basin,” Nolin says, “because, unlike many places in the West, water is not yet a crisis.” Nolin and her team hope WW2100 will help keep it that way by clarifying the choices along with the inevitable tradeoffs.