'Chocolate milk' in Lake Superior spurred by erosion
Jul 08, 2018 07:43AM ● Published by Editor
By John Myers of the Duluth News Tribune - July 7, 2018
Recent heavy rains in and around the Twin Ports raised river levels and sent thousands of tons of silt into Lake Superior, muddying the waters for anglers and raising concerns from other lake lovers.
Some of the silt is from the South Shore clay banks of the big lake, but most comes from erosion from Lake Superior's tributaries, including the St. Louis River.
The worst offender by far is the Nemadji River, which starts in Pine County and runs through Carlton County before crossing into Wisconsin and entering Lake Superior at the Superior harbor entry.
Rain events were creating a chocolate milk-like "mud line'' in Lake Superior even in May, but the mudlines have been more pronounced through June and into July as heavy rains continue to pummel the region.
Superior officially saw 9.86 inches of rain from June 1 to July 1 — more than double their usual amount for the month, including four downpours of 1.4 inches or more, according to data from the National Weather Service. In one case, more than 9 inches fell in two days just south of the Twin Ports in the Nemadji River watershed.
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