Before we spend millions on flood control, let’s remember thousands of years

Bitter Lake encroaches on the town of Waubay during spring flooding in 2011. (Photo by Brad Johnson)

Twenty-seven years ago, the federal government reached a startling conclusion about one of South Dakota’s most unusual watersheds.

After years of research, the Northern Great Plains Water Resources Research Center concluded that soil surveys indicated the Waubay Lakes Chain in northeastern South Dakota probably had not spilled naturally into the Big Sioux River with any significant volume or duration since the glacial age.

That conclusion wasn’t drawn from a few decades of rainfall records. It emerged from one of the most comprehensive scientific investigations ever conducted on a South Dakota watershed.

On June 30, the U.S. Army Corps of Engineers returned to Webster looking through a much shorter window into the past.

Using projections built largely on the last 20 years of precipitation, the Corps outlined rising lake levels, inundated roads, threatened homes and farmland, and nearly $100 million in potential public infrastructure damage under one scenario.

Then Jay Gilbertson asked what may have been the most important question of the afternoon.

The East Dakota Water Development District manager asked why the public presentation emphasized roughly two decades of precipitation when earlier federal studies reconstructed the watershed’s climatic history over centuries.

Before South Dakota considers the next step, that question deserves a public answer.

The Waubay–Bitter Lake system is one of the nation’s most significant closed-basin watersheds, compared by federal scientists to Devils Lake in North Dakota and Utah’s Great Salt Lake because all three respond to long-term climate cycles rather than having permanent surface outlets.

After the region’s devastating floods of the late 1990s, federal and state agencies took an unusually broad approach. They sponsored five separate investigations, bringing together hydrologists, climate scientists, geologists, engineers and statisticians to answer a single question: How does the 10-lake Waubay-Bitter Lake system naturally behave?

To answer that question, scientists drilled living bur oaks growing on islands in Waubay Lake. They matched those tree rings with century-old bur oak timbers from Fort Sisseton. They analyzed ancient shorelines, soil surveys, lake sediments, pollen and radiocarbon dates.

Together, those lines of evidence reconstructed the watershed’s climatic history across centuries.

Tree-ring chronologies documented an extreme drought in the mid-1700s comparable to the Dust Bowl, demonstrating that dramatic swings between wet and dry periods have long been part of this landscape.

The lesson was simple: This watershed has a much longer memory than we do.

If you’ve visited Fort Sisseton, you’ve stood in the middle of that memory. When soldiers established Fort Sisseton in 1864, they looked out across lakes on three sides. In fact, Army records later noted that the fort had originally been surrounded by a chain of lakes before many of them dried during the following years.

During the Dust Bowl — and again during the drought of 1976 — you could stand in the same place and wonder why anyone chose that location for a military fort. Today, visitors once again look across water much as those soldiers did more than 160 years ago.

Those changing views became more than history. They became scientific evidence.

None of this proves the Corps is wrong.

Changing land use, drainage, wetlands, roads, climate trends and advances in hydrologic modeling may well make the last 20 years of precipitation the most appropriate basis for forecasting future conditions.

Perhaps the Corps fully integrated the earlier paleohydrology and climatological research into its modern engineering analysis. If so, the public presentation never explained how.

And when hundreds of millions of public dollars may follow, unexplained assumptions aren’t a footnote. They become part of the public debate.

Let us know what you think...

The Corps’ Planning Assistance to States study is essentially complete. The next decision shifts from engineers to elected officials.

According to the Corps, the next step would likely be a $3 million general investigation feasibility study, with about half paid by the non-federal sponsor. If that study ultimately leads to construction, the alternatives discussed publicly range into the hundreds of millions of dollars, with state and local governments responsible for a substantial share of the cost.

For a county the size of Day County, the non-federal share is not simply a local question. It is the kind of question that ultimately reaches Pierre.

That is where science meets public policy. Before public policy follows the science, the connection between them should be clearly explained.

Twenty-seven years ago, federal scientists began with one question: How does this watershed naturally behave?

The Corps is now asking: What should we do about it?

Both are essential questions, and South Dakotans deserve to understand the first answer before they invest millions of public dollars in the second.

Citizens need to understand how the Corps’ short-term analytical window connects to the long-term climatological record federal scientists once believed was essential to understanding this watershed.

The larger the public investment, the greater the obligation to explain the science — clearly, publicly, and before the money moves.

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