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Published March 06, 2010, 12:00 AM

Plan for spring flood uncertainties

ST. PAUL — A combination of climate features — including a wet fall season and heavy, wet snowfalls all winter — have elevated the risk of spring flooding on many Minnesota watersheds. One obvious consequence of spring flooding in western and southern Minnesota counties would be delayed field working conditions in the agricultural landscape.

By: Mark Seeley, University of Minnesota Extension, West Central Tribune

ST. PAUL — A combination of climate features — including a wet fall season and heavy, wet snowfalls all winter — have elevated the risk of spring flooding on many Minnesota watersheds. One obvious consequence of spring flooding in western and southern Minnesota counties would be delayed field working conditions in the agricultural landscape.

Saturated soils combined with a slower-than-normal onset to spring will likely delay suitable field working conditions in some areas. In addition, flooded roads and highways may present some problems in transporting seed and fertilizer as well as large farm implements. Expecting, and planning ahead for, these possibilities will help farmers cope with such problems.

On the plus side, stored soil moisture should be adequate to maintain crop health throughout any drier-than-normal periods that occur early in the growing season.

In the forecasts provided by the National Weather Service on Feb. 19, virtually all points along the main stem of the Red River between North Dakota and Minnesota have more than a 50 percent chance of reaching major flood stage in March or April. Many of the Minnesota and North Dakota tributaries to the Red River have more than a 60 percent probability of at least reaching moderate flood stage.

Many southern Minnesota communities along the Minnesota River Valley have more than a 50 percent probability for moderate flooding, including Montevideo, Granite Falls and Henderson. Many other smaller watersheds are likely to have minor or moderate spring flooding, including the Cottonwood River at New Ulm and the Redwood River at Redwood Falls.

The biggest uncertainties are the forecasts for March and April temperature and precipitation. Fortunately, early March looks to be somewhat warmer and drier than normal.

For the balance of spring, there is no forecast consensus. A higher flood risk would result from a dramatic warm-up, which would accelerate the melting and runoff of the snow pack over the top of frozen soil. If combined with significant rainfall, such a weather pattern would produce rapid rises in watershed flows.

Conversely, periodic freeze/thaw cycles combined with persistent dry weather would help alleviate the flood threat. Realistically, there is not a high probability that such a pattern will emerge, and as a consequence many communities are justifiably preparing to cope with spring floods.

The National Oceanic and Atmospheric Administration Regional Offices of the National Weather Service, along with the North Central River Forecast Center in Chanhassen are providing daily updates and periodic summaries of the hydrologic outlooks.

Farmers can find climatology updates on the Web site of the Minnesota Climatology Working Group at http://climate.umn.edu/ and useful flood planning information on University of Minnesota Extension’s flood Web site at www.extension.umn.edu/flood.

Mark Seeley is a climatologist with University of Minnesota Extension.

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