Low Flows in the Upper Mississippi River
Last summer low flows in the Mississippi River upstream of St. Cloud, Minnesota caused some problems for power companies and other local interests along the river. The Mississippi River at St. Cloud, Minnesota entered this winter with flows that were about 50% of the median flow. Image courtesy of the USGS.
The Mississippi River basin upstream of Minneapolis, Minnesota has been in a severe to extreme drought since last summer.
Precipitation amounts in calendar year 2006 were 50% to 90% of normal over the northern half of Minnesota. The summer was particularly dry.
As of February 20th snow water equivalents were only 0.25" to 1" over northern Minnesota, and snow depths were 8" to 16" less than normal.
Because of the drought conditions and low snowfall amounts the U.S. Army Corps of Engineers are not going to drawdown the reservoirs in the headwaters area as far as they normally would. Two of the headwaters dams, Federal Dam and Winnibigoshish Dam, are discharging the minimum allowed flows and so far the pools are holding steady. However, as the year progresses it is likely that these two reservoirs will not reach their summer target levels. The graph to the left shows the hydrograph ensemble for the Lake Winnibigoshish elevation.
This is an exceedance probability graph for the Mississippi River at St. Cloud, Minnesota for the period February 16 through September 29, 2007. Each member of the distribution is the mean flow for the entire period. The HS distribution represents our model climatology or the normal chances of exceeding the mean flows. The CS distribution represenst simulations that incorporate the current conditions at the start of each simulation. Normally there is an 85% chance of the mean flow exceeding 3953 cfsd, but this year the chances are only about 20% that the mean flow for the entire period will exceed 3953 cfsd.

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