IMPACT OF SURFACE RUNOFF AND SUBSURFACE DRAINAGE ON LAKE MICHIGAN TRIBUTARIES IN AGRICULTURAL LAND USE REGIONS OF EASTERN WISCONSIN
Water quality in Lake Michigan is impacted by a variety of watersheds along the Wisconsin shoreline, each with diverse land uses and resulting contributions. Phosphate loading, which contributes to overgrowth of the nuisance alga Cladophora, nitrogen pollution, which can exacerbate eutrophication, and coliform bacterial contamination, which indicates fecal contamination and can create public health hazards, are key concerns. We analyzed weekly samples from 22 sites along 5 tributary streams (Centerville, Fischer, Point, Calvin, and Pine Creeks) in Manitowoc County, WI, an agriculturally dominated region of the state. Our data indicate that nutrient and bacterial levels are consistently and notably above surface water quality thresholds. Analysis of samples collected pre- and post-rain events of >0.5” showed spikes of phosphorus, turbidity, and E. coli bacterial levels, indicating surface level runoff influence. However, in other instances, rain events did not elevate relatively high background levels indicating other sources. Visual assessment of stream beds and discussion with local agricultural professionals leads us to hypothesize that subsurface drainage, such as tile drainage lines from agricultural fields, are a significant and continuous source of nutrient loading into these streams.
Rebecca Abler (Primary Presenter/Author), University of Wisconsin-Green Bay, Manitowoc Campus, firstname.lastname@example.org;
Richard Hein (Co-Presenter/Co-Author), University of Wisconsin-Green Bay, Manitowoc Campus, email@example.com;