RedN NAWQA
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Red River of the North Basin
National Water-Quality Assessment Program
M.E. Brigham(1), Tatiana Mayer(2), G.K. McCullough(3), L.H. Tornes(1), 1996,
Transport and Speciation of Nutrients in Tributaries to Southern Lake
Winnipeg, Canada: Abstracts of Presentations from 16th Annual
International Symposium on Lake, Reservoir and Watershed Management, Nov.
13-16, 1996, Minneapolis/St. Paul, MN, North American Lake Management Society, p.64.
(1)U.S. Geological Survey, Mounds View, MN
(2)Canadian Centre for Inland Waters, Burlington, Ontario
(3)Department of Fisheries and Oceans, Freshwater Institute, Winnipeg, Manitoba
Abstract
Concern over eutrophication of Lake Winnipeg has prompted monitoring of
nutrients in major tributaries to the southern basin of the lake. We
estimated loads of nitrogen (N) and phosphorus (P) near the mouths of the
Winnipeg River and the Red River of the North (Red River), the two major
tributaries to southern Lake Winnipeg. Also, nutrient loads and speciation of
suspended nutrients were determined for the Red River at the U.S.-Canada
border. Dissolved N exceeded suspended N in both rivers, and was mainly in
nitrate and organic forms. Suspended N was mostly organic. From 1975-88, the
mean of annual P loads in the Red River was about twice that of the Winnipeg
River, despite the five-fold greater streamflow in the Winnipeg River. on
average, about 60 percent of the P load in the Red River came from the U.S.
portion of that river's Basin. Dissolved P, mostly bioavailable
orthophosphate, accounted for about half the total P load in both rivers. On
average, about half of the suspended P in the Red River was in bioavailable
forms--mostly nonapatite inorganic P, with some organic P. The remainder was
biologically unavailable apatite P. Thus, much of the N and P load to
southern Lake Winnipeg is biologically available. Although the City of
Winnipeg is also known to be a major nutrient source, a substantial portion of
the load comes from nonpoint sources south of the U.S.-Canada border.
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