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Lost Tides
Lost Tides

 

The Columbia is the Northwest’s preeminent river. As it meanders 1,214 miles from its source in British Columbia to the Pacific, it is fed by a system of rivers, springs, and creeks that drain an area encompassing 258,000 square miles in seven states and two Canadian Provinces. Millions of the region’s inhabitants benefit from the services the river provides, which include irrigation, hydroelectricity, access to foreign and domestic markets, and opportunities for recreation.

The “Lower Columbia”—the 145 miles stretching from Bonneville Dam to the Pacific Ocean—is the section of the river perhaps best known by the denizens of Northwest Oregon and Southwest Washington. Here, where the river approaches a turbulent junction with the sea, the river is broad, calm, and easily navigable, the result of more than 100 years of engineering which has resulted in a vast system of dams, levees, dredged shipping lanes, and jetties.  The US Army Corps of Engineers, the Bonneville Power Administration, and other agencies work hard to keep the system safe and working, and at locations like Cape Disappointment and the Wanapum Dam work continues today. Given that climate is changing and global sea-level is rising, a questions poses itself: how have alterations to river flow and system morphology influenced the hydrodynamics within the lower river and its estuary; and what lesson do past changes hold for the future? 

Assistant Professor Stefan Talke, along with colleagues in the Department of Civil and Environmental Engineering, has long investigated how anthropogenic alterations have changed the physics of the Lower Columbia and other estuaries from their natural state.  Human and naturally-induced changes are subtly reflected in wave behavior (e.g., storm surge), tidal flows, bathymetry, water temperature and salinity intrusion. To elucidate the  past, present, future functioning of estuaries, Dr. Talke has become an expert in the hydrodynamic processes and sediment transport in estuaries, rivers, and oceans. He combines historical research, field data collection, data analysis and computer modeling to unravel the story implicit in historical and modern records and reconcile how natural and manmade factors affect the environment.

“I came to PSU in 2010,” Dr. Talke said, “and began working with Professor David Jay on a project looking into why tides off the West Coast of the Americas had increased in magnitude over the last 100 years. The data we had showed that the height of tides had generally gone up everywhere. But in some places, like Astoria, the historical record showed an increase on the order of ten percent. It was a big change, and the reason for it was a mystery.”

Dr. Talke’s work with Professor Jay put him on a trail that eventually led to a prestigious National Science Foundation Faculty Early Career Development “CAREER” award. CAREER awards support junior faculty members who epitomize the integration of teaching and scholarship through research activities. Dr. Talke received the honor for his proposal “Modeling 19th Century Estuaries to Address 21st Century Problems.” Funding from the award will finance the study of historical trends in sea level, tides, water temperature, and salinity in the Lower Columbia.  Moreover, by embedding local  high school teachers and underrepresented students in his research team, the project hopes to develop curricular materials that will introduce secondary school students to the exciting applications of science and engineering right here in their own “backyards.”

During the five year project, the team will take historical records discovered by Dr. Talke in the vaults of the US National Archives and other archives and modify existing computer models to learn more about changes in the Lower Columbia’s estuarine system. Using multi-decade time series of 19th century tidal and water temperature measurements in combination with 20th and 21st century data, the team will determine the natural variability in the river and establish historical baselines to gain a better understanding of changes that have occurred over time. Their work will also explore hydrodynamic processes, assess trends in water temperature and salinity intrusion, and make predictions about the future of the estuary.

“There was a lot of detective work involved in finding those records,” Dr. Talke said. “But when I uncovered them, it was like coming upon a treasure trove of data that could expand the horizon of time in which we can study the estuary by decades. The archives contain records that date back as far as about 1850 in Oregon.   For example, tides, water temperature, and climate were measured continuously in Astoria from 1853 to 1876, while Portland was still a village. Because of those records we’re really starting to get some interesting insights into things we just couldn’t see before: we’re starting to understand more about the system’s sensitivities and we can make better predictions about what the Columbia River estuary might look like in the future.”

What the historical records reveal are aspects of the interactions between river and ocean from before the time manmade structures regulated the course and flow, and temperatures (water and atmospheric) began trending upwards. The estuary we observe today is largely the result of building on the river that began in 1885 with the construction of the south jetty at Clatsop Spit. Upstream of the Pacific, the river is now hemmed in by levees, and the controlling depth has doubled in some places from about 8m to approximately 16m. Much of the flood plain has been reclaimed for human use. Throughout the Columbia River Basin over 470 dams store water for hydroelectricity, drinking, and irrigation. Sediment is trapped behind dams and is no longer deposited at the mouth as it once was, affecting estuarine bathymetry.  In Summer, the interplay between the warmer fresh water from the river and the colder salt water from the ocean is changing, likely resulting in increased salinity further upstream than ever before. The spring freshets, the yearly rise in stream or river levels due to snowmelt, occurs a month earlier on average, and a 40% reduced magnitude. The deep shipping lanes affect how tides roll upstream and the river rolls downstream. All of these factors place stress on the estuary, its marine and riparian environments, fish and wildlife habitats, and other characteristics of the river.  Understanding how  climate change and sea-level rise may further stress the system is critical to coming up with solutions to problems such as declining salmon populations. By understanding the river’s past, we may better able to preview the future.

Along with other researchers at PSU and elsewhere, Dr. Talke is working to recover that past and project into the future. As the tides rise and the river changes, the estuary may be reshaped over long time scales. How that change will affect the ecology and the people who depend on the system is unclear. However, Dr. Talke’s recovery and analysis of historical data stretches our knowledge back further than ever before. Doing so provides enhanced information about natural cycles of drought and surplus, and helps frame current events and discussions about the effects of climate change. Dr. Talke’s study will help establish historical baselines and generate understanding of the present and future estuary. At the same time he and his team will help create educational materials that inspire and entice the next generation of young people to engage in STEM related fields and take on the great challenges of the 21st century.