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

compiled 5/3/00


- 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.
(see: http://climate.umn.edu/doc/journal/drought_2000/db0417.htm for graphical depictions of the anomalies)

- 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 normal precipitation.
(see: http://climate.umn.edu/doc/weekmap.htm , http://climate.umn.edu/cawap/monsum/monsum.htm)

- 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.
(see: http://climate.umn.edu/cawap/monsum/monsum.htm

- 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.


- 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 supplementary indicators.
(see: http://enso.unl.edu/monitor/monitor.html)

- 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.
(see: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/regional_monitoring/palmer.gif)

- 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 corn/soybean rotation.
(see: http://www.nass.usda.gov/mn/cwmn.htm)

- 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 Minnesota.
(see: http://water.usgs.gov/cgi-bin/daily_flow?mn , http://www.dnr.state.mn.us/waters/programs/surwat_section/stream_hydro/productsf.html)

- 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.
(see: http://climate.umn.edu/doc/ice_out/ice_out_status_00.htm)

- 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.
(see: http://www.ra.dnr.state.mn.us/fire/)


- 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 end.
(see: http://www.cpc.ncep.noaa.gov)

- 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.
(see: http://www.cpc.ncep.noaa.gov)

- (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.


- 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 .


- 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.
- St. Croix River: a "flat-pool" elevation existed during April on the St. Croix near Stillwater. Unseen in April in 60 or more years.
- Waseca County: tile lines at the Southern Research and Outreach Center were not flowing in mid-April, a rare occurrence.
- statewide: stream flows continue to drop across the state. Several watersheds that are currently in the normal range are close to falling into the low flow range.


- May 11, Low Flow Coordination Meeting (for information contact: judy.boudreau@dnr.state.mn.us)
- May 18, Climate Prediction Center releases 30/90 day outlooks


http://climate.umn.edu - Minnesota Climatology Working Group
http://enso.unl.edu - National Drought Mitigation Center
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
http://www.dnr.state.mn.us/waters/ - DNR Waters
http://water.usgs.gov/cgi-bin/daily_flow?mn - U.S. Geological Survey, Minnesota
http://www.nass.usda.gov/mn/ - Minnesota Agricultural Statistics Service
http://www.ra.dnr.state.mn.us/fire/ - DNR Wildfire Information Center


Dana Dostert, DNR Waters Hydrologist - St. Paul
Dave Ruschy, Department of Soil, Water and Climate - U. of. M
Dave Ford, DNR Waters Surface Water Engineer - St. Paul
Mark Seeley, Agricultural Meteorologist - U. of M. Extension Service
Molly Shodeen, DNR Waters Hydrologist - St. Paul
Bob Merritt, DNR Waters Regional Hydrologist (acting) - Detroit Lakes
Arielle Balak, University of Minnesota Southern Research and Outreach Center - Waseca
Gary McDevitt, NWS Hydrologist - Chanhassen

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