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Published April 13, 2009, 12:00 AM

Moisture for 2009 swamps 1897, 1997

Heavy fall rains set stage for flooding
The ingredients for the record Red River crest this spring fell into place long ago.

By: Patrick Springer, INFORUM

Heavy fall rains set stage for flooding


The ingredients for the record Red River crest this spring fell into place long ago.

In the recent past, heavy fall rains saturated the ground and then froze, setting the stage for the historic initial crest of 40.82 feet March 28.

Make that very heavy rains. The barrage of precipitation that led to this year’s record flood crest obliterated the levels that produced the 1997 flood and record 1897 flood.

From July through March, Fargo received 25.26 inches of moisture, according to figures compiled by Adnan Akyuz, North Dakota’s state climatologist.

That’s far more than the 14.09 inches during the same period in 1996-97, when the Red River in Fargo peaked at 39.57 inches, and the 17.05 inches in 1896-97, when the river crested at 40.1 feet.

Red River flooding this year is unusually prolonged, said Mark Seeley, a University of Minnesota Extension climatologist. Major flooding on the Red rarely extends beyond 15 days.

The second crest, expected Thursday to Saturday, will keep the river above major flood stage for days.

“The tale of the second crest is yet to be told,” Seeley said, adding that this year could produce the longest major flooding period on record.

Also noteworthy, this year’s floodwaters have come disproportionately from the North Dakota side of the valley, Seeley said. Usually, both sides of the basin contribute in almost equal measure.

Heavy rains during the second crest would create major problems. So far, at least, the forecast calls for little rain leading up to the crest.

“Historically, a roll of the dice – Mother Nature only favors two weeks of dryness in the Fargo-Moorhead area,” Seeley said. “Right now the weather gods are smiling on us.”

Drawing on past years, the Fargo-Moorhead area can expect a two-week dry spell in April. But a 4-inch gully-washer also is common this time of year in eastern North Dakota and western Minnesota.

“It would be Noah’s flood all over again,” Seeley said of the possibility of several inches of rain falling with the Red River at very high levels. “It would be ridiculous.”

But the real beginnings of the soggy conditions that caused the Red and its tributaries to overflow their banks began much earlier, according to a University of North Dakota researcher.

Leon Osborne, a professor of atmospheric science and student of weather patterns, believes the flood is merely the latest phase in a wet cycle that began 32 years ago.

That’s when global weather patterns shifted in ways that tended to produce wetter conditions on the northern Plains, with noteworthy results in the Red River Valley, including the floods of 1997 and 2009.

The good news: Osborne believes the prolonged wet cycle has peaked, and the trend now is moving toward a drier average annual rainfall.

“We’re starting down that crest,” he said, adding annual rainfall averages will fluctuate until the wet cycle ends about 2015.

Dry periods since the onset of the wet period, most notably the drought of 1988-89, were interruptions in the predominantly wet period, Osborne said.

As the wet trend fades over the next five or six years, Osborne wouldn’t be surprised if one or two turn out to be exceptionally wet years. Eventually, the climate inevitably will enter a dry phase.

“Probably 35 years from now we’re going to be saying we could use some of that excessive moisture we had in 2009,” he said.

Still, Osborne and Akyuz agree that wet conditions beget more rain. Moisture in soil, ponds and rivers is available to evaporate and return as precipitation through the hydrological cycle.

So it will take time to reach a drier equilibrium.

“It could be a phase of several years,” said Akyuz, a professor of climatology at North Dakota State University. “We just need it to get into negative feedback,” when moisture tapers off, with less available to evaporate and return as rain or snow.

“Probably about 2020 we’re going to be at that midpoint between excessively wet and excessively dry,” Osborne said.


Readers can reach Forum reporter Patrick Springer at (701) 241-5522

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