A changing climate for water

Our blue planet has a lot of water. It’s the same water that’s been here for billions of years. No more, no less. However, Earth’s water is constantly rearranged—frozen as ice, steamed into vapor, or flowing in rivers. This rearrangement of water is probably the most obvious thing most of us can see in a changing climate. We see increasing floods and droughts, while scientists monitor decades-long trends in rising sea level and global temperatures.

“Oregon is a great place to study water and climate change because we have such varied geography and climate zones,” says John Selker, an ecological engineer in OSU’s College of Agricultural Sciences. “The diversity of climate zones in our state parallels the diversity of the globe: from oceans to desert, mountains to valleys, glaciers to cropland. It’s possible to expand our understanding of large-scale trends by examining regional-scale trends observable in Oregon.” Oregon is a model for the world.

[caption caption="Oregon precipitation map. (Illustration by Peg Herring.)"] [/caption]

A precipitation map illustrates Oregon’s climatic diversity in shades of purple, green, and gold. Our climate is dominated by two huge forces—the atmosphere and the ocean—plus a complex topography of mountain ranges. As a result, we see large variations in temperature and precipitation in short distances west to east, across the state. Those mountain ranges capture much of the state’s water. The release of that water, as runoff or snow melt, drives the migration of salmon, the growth of forests, and the availability of water to use for drinking, irrigation, recreation, and hydropower. The availability of water has shaped the state’s ecosystems and economies, affecting what grows where, what’s built where, and which strategies we choose to manage our water. Projected climatic changes are likely to throw a monkey wrench into many of these strategies.

Over the last 15 years, dozens of studies of changing climate have been published. Oregon State scientists have been involved in many of these studies, and their research is part of huge, global datasets that cumulatively document altered precipitation, accelerated glacier melt, extreme droughts and floods, and changes in water availability worldwide.

The trends are similar in all these studies. “Measurable changes, like higher heat, wilder weather, rising sea levels, are symptoms consistent with what all the climate models suggest we’ll see in the future,” says John Bolte, head of OSU’s Department of Biological and Ecological Engineering. What can we learn from these climate models? There is no onesize-fits-all answer. Oregon’s diversity, like the world’s, will drive different changes in different ways.

Climate models all agree that heat extremes will increase and cold extremes will decrease. Most models predict that Oregon’s total annual precipitation will remain about the same, with most precipitation falling in winter, and most of that in the mountains. Less of that precipitation will be stored as mountain snow, so stream flows will peak earlier. That could mean less water available in summer for irrigation, hydropower, and fish habitat.

Global sea level is rising, driven in part by melting glacial ice and by the fact that warmer water takes up more space. Climate studies project that sea level along the Northwest coast will rise between 4 and 56 inches by 2100, with significant local variations. As sea levels rise, saltwater will intrude farther into rivers, shrinking freshwater habitats. Ocean wave heights will likely increase, which will in turn increase coastal erosion. Coastlines battered by more frequent storms will reshape themselves, which could affect coastal highways and bridges. Across the state, municipal water supply and flood control infrastructures will be affected by increased storms and flood risk.

Long-term data show that ocean temperatures off our coast, although quite variable, are likely to increase, and ocean circulation will continue to change in response to ocean-atmospheric processes, which will affect marine ecosystems. Rising water temperatures promote earlier and longer-lasting, harmful algal blooms associated with paralytic shellfish poisoning. The climatic link to ocean acidification is unclear, but acidified waters hinder the ability of some ocean animals to build shells and skeletons. Shellfish aquaculture is particularly threatened by ocean acidification.

Oregon agriculture is already adapting to many climate changes. Growers are experiencing an increase in frost-free days and higher temperatures. Irrigated crops could be vulnerable as demand for available water increases and supplies decrease.

As a critical measure of snowpack, all climate studies use the amount of snow that remains in the mountains by April 1. Studies show that the April 1 snowpack will continue to decline, prompting earlier peak stream flows, warming stream temperatures, and reducing available water in summer. Salmon will experience the impacts of a changing climate throughout their lives in freshwater, coastal, and marine environments.

There is no established map into this future. When we consider what to plant, where to build, which fish to harvest, or how much water to store in reservoirs, we depend on assumptions based on our past experiences. We locate highways and plan bridges, culverts, and dams based on what we expect from past climatic conditions.

As the climate changes, we need to adjust our expectations. Our scientists are not merely documenting the changes that are upon us. They are working to reduce negative consequences and discover new opportunities that climate change will deliver.