MODELING IMPACT OF URBAN AND UPSTREAM NONPOINT SOURCES ON EUTROPHICATION OF THE MILWAUKEE RIVER

This paper describes a study conducted to evaluate the impact of the a bsence vs. the presence of the North Avenue Damin Milwaukee, Wisconsin , on water quality in the Milwaukee River in terms of conventional con stituents, such as DO, chlorophyll a, BOD, and nutrients (N and P). Ph ytoplanktonic primary production had been recognized earlier as a link between mostly nonpoint nutrient loads to the Milwaukee River and deg radation of water quality in the River. A mathematical model of a rele vant section of the River was used in the study to estimate the effect of the removal of the Dam on this primary production link. The author s established the model using WASP, which is USEPA's widely used model ling package. The modelled extent of the River included both shallow, productive upstream reaches as well as impounded downstream sections. In the impounded reach of the River where the Dam is located, the simu lated removal of the Dam (1) replaced net phytoplankton decay with net phytoplankton growth because of improved light conditions and limited settling; (2) substantially increased the concentration of DO because of the increased photosynthetic production and reduced benthic consum ption; and (3) somewhat increased bottle BOD5 because of the elevated phytoplankton levels. The simulated removal of the Dam eliminated the negative effects of eutrophication at the site while possibly shifting the potential for these effects further downstream towards Lake Michi gan. Copyright (C) 1996 IAWQ.