map of Willamette River Basin

Western Oregon has a wet reputation. Verdant evergreen forests carpet the hills. Soggy springs drain into rivers that churn brown with winter rain. Snow piles high on the uplands. In a normal year, the Willamette River Basin (WRB) — the heart of Oregon’s cities, farms and forests — gets dumped on by buckets of rain and snow. But, a new study involving scientists, economists and community stakeholders presents a more complex picture of water availability in the WRB, now and decades into the future.

The researchers used a comprehensive model to look at human, hydrologic and ecological dimensions of the water system. The model allowed them to examine how climate change, management strategies, cost, population and a host of other factors may impact water quantity within the basin over the next 90 years.

Despite the region’s soggy image, the study showed that water scarcity may occur depending on the time and place. “If you look at the aggregate, water as a whole over the year, there’s a lot of water,” says Anne Nolin, co-author of the study and a professor at the College of Earth, Ocean, and Atmospheric Sciences. “But we actually have scarcity that happens on a seasonal and regular basis.” The findings were recently published in the Proceedings of the National Academy of Sciences.

The study resulted in a number of other surprising findings. One of them is that humans are not the biggest direct consumers of water. Lush forests in the uplands and cool, flowing rivers required for healthy fish habitat require the most water. Humans place high value on these ecosystems and the water they use. The researchers also found that climate change in the uplands has the largest impact on water scarcity, while in the lowlands, the outcomes of decision-making dominate water availability. Paradoxically, urban expansion into agricultural areas may save water, since urban water use is often lower than irrigated agriculture. In addition, almost all residential water is recycled back into the system, while most agricultural water is not. Socio-economic issues play a huge role in water use as well. For some users, water may be considered scarce even if there is a nearby source, because the cost to obtain the water (e.g., investing in an irrigation system) or transport it is prohibitive. The authors likened the situation to the global food system. There may be enough food to feed the world, but access is uneven, leading to seasons and regions of scarcity.

Nolin says it’s important to contextualize the findings. “If you only cared about water in urban areas, you could look at this study and say, wow, we could save water if we cut down the forests, or expanded our cities into agriculture. But that’s not all we care about. We value verdant forests and the ecosystem services they provide. We value environmental flows to keep native fish healthy as part of a healthy aquatic ecosystem. We value our agricultural land, high-quality farm products, and that heritage,” she says.

The findings are lending important insights into water use across the WRB. But Nolin says the process itself — collaborating with economists and stakeholders — was fundamental to understanding the entire system.

“Nobody was aware of the whole thing,” she says. “Through this water project and modeling effort, we were able to not just model the system, but quantify and identify the linkages, basically piece together how the whole system works.”

In a follow-on project, the research team is adding additional components to the model, including stream temperature, crop choices, energy and groundwater. The team, for example, will look at how climate change and urban water use increases water temperature in nearby streams. They will explore forest management practices that help retain more snowpack and decrease severe wildfire. They will examine the water demand when farmers transition from grass seed to filberts, a thirsty crop for its first few years. And, they will look at the impacts of an exceptionally dry year, such as 2015, when people started tapping into groundwater to subsidize their needs. They hope to provide a water modeling template that can be used in other basins facing scarcity and challenging tradeoffs between food, energy and water.

The project’s success in identifying times and regions of scarcity can be attributed to the willingness among institutions and people to explore different future scenarios. Nolin says that collaborative approach could not have happened in an already-contentious region, such as the Sacramento River Delta.

“It’s our opportunity as scientists and as stakeholder partners to identify desired, sustainable water futures and to choose adaptation pathways that help us achieve our goals. Basically, what kind of place do we want to live in? Let’s make sure that place is sustainable.”

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