Prairie Smoke: 2010

Friday, November 5, 2010

November 2010

The above graph shows a trace of the gage heights of the Minnesota River before, during and after the recent flood event in late September. Note that the river at Mankato was above flood stage for about 9 days, producing damage to roads and some buildings.

The following graph shows streamflow in cubic feet per second (cfs) during the same period. The small brown triangles show what the normal discharge is for these same days of late September and early October. The peak flood discharge was over 80,000cfs; the normal discharge for those days is about 800cfs. That is amazing! The normal discharge indicates that this time of the year is the low water period of the river -- but certainly not this year!

The following map shows that the highest precipitation occurred in an east/west strip over the I=90 corridor with very substantial rains (9-10 inches) in the Mankato/St. Peter area.

And finally, next is a map of the percent of mean rainfall for the month; you can see that we received over 300% of the normal precip for the month. Again, really remarkable!

In early October a controlled burn of the 7-acre Uhler Prairie was conducted by the St. Peter Fire Department. It had been eight years since this prairie was last burned, and thus it was well overdue for a scorching. Fires are essential to a prairie for three reasons: (1) they remove dead and decaying material, (2) they release stored nutrients into the ground and encourage new growth, and (3) they keep trees and other woody plants from spreading into grasslands. Without fires, prairies have a difficult time thriving in the long run. The original native prairies (pre-settlement) were usually started by lightning strikes, but restored prairies are now burned periodically by the various agencies, organizations, and municipalities that manage them. What remains after Sunday’s burn looks and smells like a charred, ashen field, but don’t be discouraged; next spring the prairie will bounce back and appear greener than it has in years. The following is a series of photos from during and after the event.


Uhler Prairie Burn, 10/3/10. Photo by Herb Chilstrom.

Uhler Prairie Burn, 10/3/10. Photo by Herb Chilstrom.


Uhler Prairie Burn, 10/3/10. Photo by Herb Chilstrom.


Uhler Prairie Burn, 10/3/10. Photo by Herb Chilstrom.

Uhler Prairie Burn, 10/3/10. Photo by Herb Chilstrom.

Uhler Prairie the day after the burn, 10/4/10. Photo by Bob Dunlap.

Bob Moline

Tuesday, April 6, 2010

March 2010

This graph shows the gauge height (measured or calculated by the U.S. Geological Survey) for the Minnesota River at Mankato during the high water period this spring. You can see that the MN River was above flood stage at Mankato from late 18 March through late 28 March. MN Highway 22 remained open through this period but MN 99, the road that crosses the river close to the Whiskey River Restaurant, was closed at the bridge for a while. Water never covered the highway but came very close to the structural beams under the road that support the bridge so MNDOT decided it was best to close the bridge. MN 99 has reopened now, of course.

March was warmer than usual this spring so the serious snowmelt period occurred earlier than normal this year. Normal high water time for the river is around the second week in April. Even today, however, the river is carrying plenty of water: the discharge rate this morning is 27,900cfs (cubic feet per second) whereas the normal discharge for 6 April is about 6,250cfs. For comparison, discharge for the river at flood stage a couple of weeks ago was around 62,000cfs!

The above map prepared by the Midwestern Regional Climate Center at the U of Illinois shows the temperature anomalies (departures from normal) for March in the Upper Midwest and you'll note that all of MN was above normal for March. Northeastern MN was 10 to 11 degrees above normal and much of south central MN (Arb Country!) was between 4 and 5 degrees above normal.

A companion map showing precip anomalies over the Upper Midwest seems not to be correct indicating much more precip than I think we had so I'm not including it here. As a substitute, here's a map of total March snowfall and it shows the VERY unusual case of no snowfall in MN. Isn't that remarkable?!

On the other hand, we had plenty of snow cover this winter that lingered into March and here's the DNR's map documenting that. The map shows 15-18 inches of snow in Nicollet Co and measurements from our yard in St. Peter indicated 17-18 inches. You'll no doubt agree that if we'd received our normal March snowfall, between 10 and 12 inches, flooding of the MN River would have been much more serious.

For a more detailed summary of Minnesota's climate conditions and the resulting impact on water resources in March, please visit http://climate.umn.edu/doc/journal/hc1004.htm.

Here's a series of photographs from the Arb this past winter, taken by Arboretum Naturalist Bob Dunlap.