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Water Summary Update: Rapid runoff led to historic flooding in March

  • 4/5/2019 8:00:00 AM
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DES MOINES — Although statewide precipitation was slightly below average in March, a combination of high precipitation in Nebraska, snowmelt and rapid runoff led to historic flooding along the Missouri River, according to the latest Water Summary Update.  

“March precipitation in Iowa was just slightly below normal, but the storm in the middle of the month brought significant rain to Iowa and Nebraska, which resulted in the extensive flooding that occurred in western Iowa,” said Tim Hall, DNR’s coordinator of hydrology resources.

“Conditions in the Missouri River basin remain wet, with more snowmelt to come from the Dakotas and later from the mountains in Montana and Wyoming,” Hall added.

A very strong low pressure system (bomb cyclone) between March 12 and 14 was the most notable event of the month. Heavy rainfall in eastern Nebraska and blizzard conditions across western Nebraska occurred as the system moved east. In Iowa, above freezing temperatures combined with heavy rainfall on top of a substantial snowpack and frozen soil led to rapid melting and runoff.

Preliminary statewide precipitation was just over 2 inches - about 0.10 inches below average. This ranks March about in the middle of pack for historical March precipitation. Statewide average snowfall was 2.20 inches or 2.50 inches below average, making snowfall in March the 28th lowest in 132 years. The highest level reported was in Sibley (Osceola County) at 9.5 inches of snow, 1.6 inches above average. The state of Nebraska received about 3 inches of rainfall for the month of March, which is about double their normal for the month.

While overall streamflow is trending down, many streams in Iowa moved above flood stage, with the highest in western and northeast Iowa.

Iowa temperatures averaged 30.7 degrees, or 5.2 degrees below normal, ranking March 2019 as the 30th coldest among 147 years of state records.

For a thorough review of Iowa’s water resource trends, go to www.iowadnr.gov/watersummaryupdate

The report is prepared by technical staff from Iowa DNR, the Iowa Department of Agriculture and Land Stewardship, IIHR—Hydroscience and Engineering, and the U.S. Geological Survey, in collaboration with Iowa Homeland Security and Emergency Management Department.

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