Abstract
Lake McCarrons in Roseville, Minnesota, displays signs of anthropogenic eutrophication. To increase its summer transparency, different approaches/actions have been considered. A wetland system designed to remove phosphorus from the watershed surface runoff into the lake was installed and went into operation in 1985. Its performance has been described in reports by Oberts and Osgood (1988) and the Metropolitan Council Environmental Services (MCES, 1997). Other reduction techniques for primary productivity can be considered. There is also some question about the effect that the wetland system has had on inflow water temperatures. By exposing the tributary water to the atmosphere, a wetland may cause a warming of the tributary water, which is then more likely to enter the surface mixed-layer of a stratified lake in summer. In the surface mixed layer, light can be plentiful, and the phosphorus in the inflow may stimulate 'increased algae growth. The Executive Summary of the MCES (1997) report ends with this statement: "Because of the amount of polluting material discharged into the lake over the past decades, lake improvement will be difficult and expensive. The MWTS has been helpful over the past 12 years in reducing net inputs to the lake, but this study has shown that the system is decreasing the effectiveness and may be directing inflow to a limited volume of the lake above the thermocline. Possible approaches to lake improvement include chemical treatment of the lake andlor inflows; rerouting inflow below the thennocline; whole or partial lake mlxmg; and attention to the management changes noted above for the MWTS to improve perfonnance. "In this report we shall address some of these issues.
Original language | English (US) |
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State | Published - Sep 2000 |
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St. Anthony Falls Laboratory
Shen, L. (Director)
St. Anthony Falls LaboratoryEquipment/facility: Facility