Sources and sinks for nitrogen and phosphorus in part of the Upper Mississippi River Basin, Minnesota and Wisconsin, 1991-93 [Abstract] in Minnesota Water '96--Changing Patterns of Power and Responsibility: Implications for Water Policy, Fifth Biennial Conference on Water Resources in Minnesota, University of Minnesota, Water Resources Research Center, May 20-21, 1996
By Kroening, S.E., and Fallon, J.D.
Abstract
The preface of a slide presentation at the conference is the abstract.
A mass balance approach was used to estimate the sources and sinks for nitrogen and phosphorus in the portion of the Upper Mississippi River Basin upstream from the outlet of Lake Pepin. The mass-balance model included five input terms: commercial fertilizer, animal manure, atmospheric deposition, nitrogen fixation, and point sources. The output terms were: phosphorus and nitrogen removed by crop harvest; export by river outflow; and a term including volatilization, denitrification, sedimentation, and ground-water storage. Initial results showed an annual source of 625,000 metric tons of nitrogen and 88,000 metric tons of phosphorus. Seventy percent of the nitrogen and 97 percent of the phosphorus input to the study area were from commercial fertilizer and animal manure. Twelve percent of the nitrogen and four percent of the phosphorus removed were through discharge to the Mississippi River at Lake Pepin.
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U.S. Department of the Interior |
U.S. Geological Survey
