Minnesota Drought Situation Report - August 16, 2007
(August 14 report modified for recent changes in U. S. Drought Monitor)
Drought Monitor - August 14, 2007
The latest U. S. Drought Monitor(see map at right)
now places Minnesota's Arrowhead region and portions of central Minnesota in the Extreme Drought
category. This is a one-category deterioration of drought conditions from the previous week.
This week's map shows improvement in drought conditions in southeastern Minnesota. Overall, the U.S. Drought Monitor continues to depict
much of northeastern Minnesota and most of the southern one half of Minnesota in the Severe Drought
category. Elsewhere in Minnesota, most areas are classified as experiencing a Moderate Drought or
described as being Abnormally Dry. 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:
Welcome rain fell this past Friday and Saturday across sections of central and southeastern Minnesota. Rainfall totals ranged between one and two and one half inches in these
areas (see map at left). Small sections of northwestern and north central Minnesota also received more than one inch of rain
for the week. Elsewhere in Minnesota, rainfall was spotty, totaling less than one-quarter inch in most locales.
Monday evening rain, occurring
after the Monday morning map deadline, exceeded one inch in many central, east central, and southeastern Minnesota counties. In some east central
Minnesota counties, rainfall totals topped two inches in this event. Weekly
temperatures were generally above the long-term mean last week.
The combined impact of the Saturday and Monday rain events kept the drought situation from deteriorating further in central Minnesota, and
greatly improved drought conditions in southeastern Minnesota. The situation continues to worsen in southwestern and south central Minnesota, and in far
Dryness has been entrenched across most of Minnesota for much of the 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 is 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:
Rainfall totals since April 1 are less than ten inches across portions of central, east central, and southwestern Minnesota (see map below). Growing
season rainfall totals have deviated negatively from historical averages by more than four inches across many central, east central, southwestern, and south central
Minnesota counties (see map below). This is roughly the equivalent of missing all of June's rainfall. Seasonal rainfall deficits exceeding
six inches are reported in spotty areas of central, east central, and south central Minnesota. 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 many counties in the southern two thirds
of Minnesota, and portions of Minnesota's Arrowhead region (see map below).
Agriculture - The
Agricultural Statistics Service reports that as of August 10, topsoil moisture across 78% of Minnesota's landscape was "Short" or "Very Short". This is a
slight improvement from the previous week. Corn and soybean conditions in many areas continue to be sub-par due to inadequate soil moisture supply.
Only 33% of Minnesota's corn acreage is considered to be in "Good" or "Excellent" condition. 45% of Minnesota's soybean acreage is considered to be in "Good" or "Excellent" condition.
A federal agricultural disaster has been declared for
24 Minnesota counties suffering from drought. Farmers and ranchers in an additional 32 adjacent counties will also be eligible for drought recovery assistance.
Stream flow -Stream discharge in roughly
33% of Minnesota's rivers and streams is below the 25th percentile when compared with historical data for this time of year.
Flow conditions in many northeastern, central, and east central
Minnesota watersheds fall below the 10th percentile for the date, leading the Department of Natural Resources to
suspend surface water appropriation permits in some areas.
Mississippi River flow conditions remain very low along the upper reaches of the river.
Mississippi River discharge near Anoka is at roughly the same flow rate as it was during the heart of some of Minnesota's more famous droughts (1976, 1988, 2006).
Lake levels -
Lake levels continue to drop throughout Minnesota, 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, especially in 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 High or Very High across portions of central
and northern Minnesota. With the exception of southeastern Minnesota, the remainder of the state is depicted in the Moderate Danger category. Southeastern
Minnesota counties have a Low wildfire danger designation. The DNR has issued
open burning restrictions for many Minnesota counties.
Public water supply - Many Minnesota communities
have imposed watering restrictions due to increased lawn watering demands.