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Full-Text Articles in Physical Sciences and Mathematics
Human Impacts To Minnesota Wetlands, Carol A. Johnston
Human Impacts To Minnesota Wetlands, Carol A. Johnston
Journal of the Minnesota Academy of Science
ABSTRACT-Minnesota's 3.6 million ha of wetlands have been impacted by a variety of human activities, including agricultural drainage, urbanization, water control, and nonpoint source pollution. More than half of Minnesota's wetlands have been destroyed since the first European settlers arrived, an average loss of about 35,600 ha/yr. Drainage for agriculture is the major cause of wetland loss in Minnesota, particularly in southern Minnesota and the Red River Valley. In addition to impacting wetlands directly, wetland drainage affects downstream areas by increasing flood flows, and releasing sediment and nutrients. Urban development and highway construction affect a smaller proportion of Minnesota's wetlands, …
The Metropolitan Wastewater Treatment Plant And The Mississippi River: 50 Years Of Improving Water Quality, D. Kent Johnson, Paul W. Aasen
The Metropolitan Wastewater Treatment Plant And The Mississippi River: 50 Years Of Improving Water Quality, D. Kent Johnson, Paul W. Aasen
Journal of the Minnesota Academy of Science
ABSTRACT-The Metropolitan Waste Control Commission and its predecessors have operated the Metropolitan Wastewater Treatment Plant on the Mississippi River at St. Paul, MN, for the past 50 years. Analysis of water quality data collected over the past 60 years shows a general improvement of water quality as the waste treatment process has been upgraded. In 1926, dissolved oxygen ranged from <1 mg/L to 2 mg/L in the river reach from St. Paul to Lock and Dam 3 (August mean values). In 1987, dissolved oxygen values in the same area were 7 mg/L or greater. The drought of 1988 produced severe low flow conditions in the Mississippi River, but dissolved oxygen values continued to meet or exceed the 5 mg/L water quality standard. Biological sampling in 1926 and 1959 showed an absence of clean water organisms. Biological sampling in 1985 showed an abundance of clean water organisms. The most dramatic evidence of this resurgence is the reappearance of the Hexagenia mayfly in St. Paul after a 50 year absence. The water quality improvements in the Mississippi River correlate directly with improved treatment plant processes, particularly the current advanced secondary treatment facility, and with improved waste control throughout the Minneapolis/St. Paul area.