Minnesota Drought Situation Report - August 23, 2007
Drought Monitor - August 21, 2007
The latest U. S. Drought Monitor (see map at right)
places Minnesota's Arrowhead region and portions of central Minnesota in the Extreme Drought
category. Much of the rest of the northern two-thirds of Minnesota falls in the Severe Drought
or Moderate Drought designation. Most of northwestern Minnesota is described as being
Abnormally Dry. Last weekend's
extraordinary rainfall event significantly altered drought designations in southern Minnesota. Conditions in southwestern and south central Minnesota
counties improved by two categories over the previous week. These areas now fall in the
Abnormally Dry category, a designation often used to describe regions coming out of drought. Southeastern
Minnesota counties are very wet and no longer experience drought conditions. The drought situation in the northern one third of Minnesota is the result of the lingering impacts of a
very dry 2006, a snow-sparse 2006-2007 winter, and dry 2007 mid-summer weather. The drought situation in the southern two thirds of Minnesota is due to an
extremely dry 2007 growing season (see: 12-week U.S. Drought Monitor animation).
The U. S. Drought Monitor index is a blend of science and subjectivity where intensity categories are based on several indicators.
Last week's weather:
A very large area of southern Minnesota received over four inches of rain this past weekend (see map at left). The rain event led to
devastating floods in southeastern Minnesota. In southwestern and south central Minnesota,
the heavy rain was widely regarded as beneficial, replenishing soil moisture reserves and elevating levels in surface water systems. In the most drought-stricken
regions of Minnesota, last week's rainfall was light to moderate. Central Minnesota areas experiencing Extreme Drought reported rainfall totals of
around one inch for the 7-day period ending Monday morning. An additional one or more inches of rain
fell in isolated sections of central Minnesota on Monday evening and early Tuesday morning. The rain was welcome, but did not significantly change the drought status
in these locales. In the northern one third of Minnesota, rainfall totals were very light last week, generally less than one tenth of an inch.
Weekly temperatures were very cool last week, ranging from two to six degrees below the long-term mean.
Mid-summer Dryness (June 5 - August 14):
Dryness was entrenched across Minnesota for much of the mid-summer. Rainfall for the ten-week period from June 5 through August 14 totaled less than four inches
in many locations in the southern two thirds of Minnesota (see map below).
In these areas, rainfall totals for the period were five or more inches short of the historical average (see map below).
When compared with historical rainfall totals for the same ten-week time frame, 2007 values ranked at or below the 5th percentile (one year in twenty occurrence)
for many counties (see map below). In a few areas, the June 5 - August 14 rainfall totals were near all-time record low values.
The timing of the dry weather was unfortunate. The period from May through September is historically the wettest time of the year in Minnesota. Long-term average
rainfall rates during this time interval are around one inch per week. Very dry weather, occurring during a time of year when ample rain is typical, leads to the rapid
intensification of drought. The lack of precipitation, along with very high evaporation rates, led to deteriorating crop conditions, lower
stream flows and lake levels, and increased wildfire danger.
Growing Season (April 1 to present) precipitation totals, departure, and ranking:
Growing season rainfall totals (April 1 to present) have deviated negatively from historical averages by more than four inches across many northeastern, central, and east central
Minnesota counties (see map below). This is roughly the equivalent of missing all of June's rainfall. When compared with other seasonal
rainfall totals-to-date in the historical database, this year's rainfall for the season ranks just above the 10th percentile (one year in ten occurrence) in
central and east central locales, and in portions of Minnesota's Arrowhead region (see map below).
Agriculture - The
Agricultural Statistics Service reports that as of August 17 (before the weekend rains), topsoil moisture across 68% of Minnesota's landscape was "Short" or "Very Short".
Next week's report will show significant improvement in the percentage of Minnesota's landscape considered to have "Adequate" topsoil moisture.
Corn and soybean conditions in many areas continue to be sub-par due to inadequate soil moisture supply during the core of the growing season.
Only 33% of Minnesota's corn acreage is considered to be in "Good" or "Excellent" condition. 43% of Minnesota's soybean acreage is considered to be in "Good" or "Excellent" condition.
On August 7, a federal agricultural disaster was declared for
24 Minnesota counties suffering from drought. Farmers and ranchers in an additional 32 adjacent counties are also eligible for drought recovery assistance.
Stream flow - Stream discharge in
roughly 30% of Minnesota's rivers and streams remains below the 25th percentile when compared with historical data for this time of year.
Flow conditions in many north central, northeastern, central, and east central
Minnesota watersheds fall below the 10th percentile for the date.
Lake levels -
Water levels are very low on many Minnesota lakes, exposing shoreline, and in some cases, making water access difficult.
Quantitative lake level data are difficult to obtain in real time. However, anecdotal reports indicate that many lakes in northern, central and east central Minnesota
are a foot or more below average levels for the date. The Lake Superior water level is
near an all-time low for the date and could fall below the all-time seasonal low by early autumn.
Wildfire Danger - The Department of Natural Resources - Division of Forestry classifies current
wildfire danger as Moderate, High, or Very High across
much of northern Minnesota. The remainder of the state is depicted in the Low Danger category. The DNR has eased fire restrictions in central and southern Minnesota counties, but
open burning restrictions remain in place across much of
Public water supply - Many Minnesota communities
have imposed watering restrictions due to increased lawn watering demands.
More drought information resources are found at http://climate.umn.edu/doc/journal/drought_information_resources.htm.
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Last modified: August 23, 2007