Total Phosphorus loads known to Lake of the Woods
Ann Arbor, MI — Evidence indicates that phosphorus inputs into Lake of the Woods have been declining in the last few decades. Lake of the Woods is the second largest inland lake in Ontario and an important international water body that is on Minnesota’s list of impaired waters, recognized by the International Joint Commission (IJC) as needing bi-national management, and highlighted in former Ontario Environment Minister John Wilkinson's Annual Report on Drinking Water for 2010. The lake supports Ontario’s largest non-resident sport fishery and provides drinking water to many towns and cities. Increasing political attention has necessitated more research on the water quality of the lake, with a focus on whether increases in nutrient loads are linked to the high frequency of algal blooms on the lake.
Research conducted by scientists from Trent University and the Ontario Ministry of the Environment investigated the total phosphorus budget for Lake of the Woods. Three observations were made: 1) contrary to popular public perception, increasing residential shoreline development contributes relatively small TP into Lake of the Woods, 2) the largest anthropogenic TP sources are pulp and paper mills along the Rainy River, the lakes primary tributary, and atmospheric deposition, and 3) due to reduced nutrient loading from pulp and paper mills since the 1970s, nutrient loading may, in fact, have declined in the last few decades.
"For the first time, we present a total phosphorus budget for Lake of the Woods," says coauthor Kathryn Hargan. "Our team determined both the major and minor sources of total phosphorus into the lake and that these sources have led to no significant increase." These load reductions likely indicate that the water quality of the Lake of the Woods, with respect to nutrient loading, has improved over the last few decades.
The results from this research may be used by governments and the International Joint Commission to inform new policies and help better manage the water quality of the Lake of the Woods. Due to the highly complex morphology and hydrology of the lake, it may prove best to manage isolated bays separately from the lake’s main channel, as these bays have shown to have unique water quality.
Original Publication Information
Results of this study, "A total phosphorus budget for the Lake of the Woods and the Rainy River catchment," are reported by Kathryn E. Hargan, Andrew M. Paterson, and Peter J. Dillon in the Volume 37, No. 4, of the Journal of Great Lakes Research, published by Elsevier, 2011.
Contacts
For more information about the study, contact Kathryn Hargan, Biology Department, Queen’s University, 116 Barrie Street, Kingston, Ontario, Canada K7L 3N6; kathrynhargan@gmail.com.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, Environment Canada, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; jglr@ec.gc.ca; (306) 975-5310.
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