|HydroClim Minnesota - May , 2000
A monthly electronic newsletter summarizing Minnesota climate conditions and the resulting impact on water resources.
Distributed on the Wednesday following the first Monday of each month.
State Climatology Office - DNR Waters
WHAT HAS HAPPENED:
- the last quarter of 1999 (October - December) was extremely dry across most of
Minnesota. Many western Minnesota communities were at or near all-time record low
precipitation totals for the period. Additionally, snowfall totals this past winter were
very light, roughly 50 to 75 percent of average. The shortage of precipitation created
deficits in surface hydrology normally benefiting from autumn recharge and snow melt
runoff. The situation was most acute in far southwestern Minnesota where the dry spell
commenced in July - 1999, roughly three months earlier than the rest of the state.
Precipitation totals over the nine month period, July - 1999 through March - 2000, fell
short of normal by over eight inches in some southwestern Minnesota communities.
- precipitation totals for the month of April were generally below average across much
of Minnesota. South central, southeastern, and central Minnesota fell short of historical
averages by 1.25 to 1.75 inches. Some counties in far western Minnesota, and in portions
of northern Minnesota received near normal precipitation. For most of Minnesota, April
rainfall totals were insufficient to stem the worsening precipitation deficits. Over the
last seven months, most Minnesota communities have received approximately 50 percent of
- April temperatures were close to historical averages throughout Minnesota. This marks
the first time in six months that monthly average temperatures did not exceed normal.
- while not directly tied to hydrology, a notable (and damaging) atmospheric phenomenon occurred on April 5. A strong low pressure system moving through the Upper Midwest transported powerful sustained winds into Minnesota. Wind gusts exceeded 50 mph in many areas, and exceeded 70 mph in some locations.WHERE WE STAND NOW:
- as of their April 27th release, the National Drought Mitigation Center continues to
classify southwestern Minnesota in their "D2" category ("Severe Drought -
crop or pasture losses likely; fire risk very high; water shortages common; water
restrictions imposed"). The remainder of southern Minnesota is in the "D1"
category ("First Stage Drought - damage to crops, pastures; fire risk high; streams,
reservoirs, or wells low, water shortages developing or imminent, voluntary water use
restrictions requested"). Areas of north central Minnesota are in the "DO"
category ("Abnormally Dry"). The NDMC index is a blend of science and
subjectivity where intensity categories are based on six key indicators and numerous
- the April 29th Palmer Drought Index depiction places southwestern and west central
Minnesota in the moderate drought category, and near normal elsewhere. The Palmer Drought
Index is used for assessing long-term meteorological conditions.
- the Minnesota Agricultural Statistics Service reports that topsoil moisture statewide
as of Friday, April 28 was rated 13% very short, 40% short, 44% adequate, and 3% surplus.
In southwestern Minnesota, soils are very dry throughout the rooting zone. Most other
areas of Minnesota have average moisture in the middle and lower soil layers. Quantitative
soil moisture measurements are rare. However, recent soil moisture measurements from
University of Minnesota research locations show sharp differences between south central
and southwestern Minnesota. Plant available soil moisture measured at the U. of M.
facility in Waseca (Waseca county) exceeds 10 inches in a five foot profile. By contrast,
plant available moisture measured at Lamberton (Redwood county) is approximately three
inches. Measurements at both locations are taken at plots planted in corn, soybeans, or a
- current stream discharge values for many Minnesota streams rank below the 25th
percentile for this time of year. According to U.S. Geological Survey reports, some stream
flows fall below the 10th percentile. Some of the lowest stream flow values (relative to
the historical distribution) can be found in southwestern, central, and north central
- early spring lake level data are currently being processed. However, preliminary indications are that lake levels rose very little from last autumn. Typically, autumn precipitation and snow-melt runoff leads to significant lake level rises from autumn to spring. Additionally, it appears that on average, lake levels are 0.5 foot lower than last year at this time.
- delayed early-winter ice development and mild winter and spring temperatures led to
extraordinarily early lake ice-out dates in 2000. Many Minnesota lakes lost their ice
three to four weeks ahead of their historical average. For some lakes, this year's ice-out
was the earliest on record. All of Minnesota's lakes are now free of ice.
- water levels in many wetland complexes are quite low, or in many cases the wetlands are completely dry.
- the present warm and dry weather enhances the potential for wildfires. Burning
restrictions are in place for many Minnesota counties.
- the 30-day outlook from the Climate Prediction Center tilts towards below normal May
precipitation in the southern two thirds of Minnesota, near normal in the far north.
Normal May precipitation ranges from two and one half inches in the northwest, to four
inches in the southeast. The May temperature outlook is for above normal conditions
statewide. Normal high temperatures climb from near 60 in early May to the low 70's by the
end of the month. Normal lows climb from near 40 early in the month to near 50 by month's
- the 90-day outlook for May through July tilts towards below-normal precipitation in
the southern half of Minnesota, near normal in the north. The May through July outlook
calls for above-normal temperatures statewide.
- (REPEATED FROM LAST MONTH) foresters note the potential for a major burn in the BWCA. Many trees blown down by the July, 1999 superstorm rest on their larger branches, keeping most of the heavier fuel off the ground. This architecture, plus a lack of shade, creates an excellent drying condition. A modest dry spell in the future will lead to high forest fire danger in that area.FROM THE AUTHOR:
- many of the state's hydrological systems are showing the signs of significant precipitation deficits. These deficits leave Minnesota's water resources very dependent on adequate spring and summer rains. With temperatures climbing and many plants now actively growing, evapotranspiration rates are on the increase. Historically, rainfall rates are matched by evapotranspiration rates starting in June. Therefore, much of the summer rainfall is "consumed" by the transpiration process and little is left to replenish surface and ground water systems. Should precipitation totals remain meager, the situation could deteriorate quickly in surface and near-surface water resources. Deeper aquifers remain unaffected in the short term, especially in light of the very wet 1990's. Public and private entities should take the proactive step of reacquainting themselves with their drought contingency plans. Drought information resources can be found on the State Climatology Office Web site at http://climate.umn.edu/doc/drought_2000.htm .NOTES FROM THE FIELD:
- northwestern Minnesota: the upward spiral of surface water rises has stopped, but
groundwater connected wetlands and lakes remain high. Paradoxically, perched wetland
complexes are nearly dry.
- May 11, Low Flow Coordination Meeting (for information contact: firstname.lastname@example.org)
http://climate.umn.edu - Minnesota Climatology
Dana Dostert, DNR Waters Hydrologist - St. Paul
Contributions of information and suggestions are welcome!